Strategy. To pursue its goal, the fund normally invests at least 80% of its net assets, plus any borrowings for investment purposes, in municipal bonds that provide income exempt from U.S. federal income tax. Municipal bonds are debt securities or other obligations issued by states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities, or multistate agencies and authorities. Municipal bonds typically are issued to finance public projects, but also may be issued for private activities. The fund's sub-adviser, Insight North America LLC, focuses on identifying undervalued sectors and securities. To select municipal bonds for the fund, the sub-adviser uses fundamental credit analysis to estimate the relative value and attractiveness of … Show more… To pursue its goal, the fund normally invests at least 80% of its net assets, plus any borrowings for investment purposes, in municipal bonds that provide income exempt from U.S. federal income tax. Municipal bonds are debt securities or other obligations issued by states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities, or multistate agencies and authorities. Municipal bonds typically are issued to finance public projects, but also may be issued for private activities. The fund's sub-adviser, Insight North America LLC, focuses on identifying undervalued sectors and securities. To select municipal bonds for the fund, the sub-adviser uses fundamental credit analysis to estimate the relative value and attractiveness of various sectors and securities and to exploit pricing inefficiencies in the municipal bond market. The sub-adviser actively trades among various sectors and securities based on their apparent relative values. The fund seeks to invest in several different sectors, and may overweight a particular sector depending on each sector's relative value at a given time. The fund invests at least 50% of its net assets in bonds that are rated investment grade (i.e., Baa3/BBB- or higher) at the time of purchase or, if unrated, deemed of comparable quality by the fund's sub-adviser. For additional yield, the fund may invest up to 50% of its net assets in bonds that are rated below investment grade ("high yield" or "junk" bonds) or, if unrated, deemed of comparable quality by the fund's sub-adviser. The fund may invest in bonds of any maturity or duration and does not expect to target any specific range of maturity or duration. The dollar-weighted average maturity and duration of the fund's portfolio will vary from time to time depending on the portfolio manager's views on the direction of interest rates. A bond's maturity is the length of time until the principal must be fully repaid with interest. Duration is an indication of an investment's "interest rate risk," or how sensitive a bond or the fund's portfolio may be to changes in interest rates. Generally, the longer a bond's duration, the more likely it is to react to interest rate fluctuations and the greater its long-term risk/return potential. Although the fund normally invests at least 80% of its net assets in municipal bonds, the income from which is exempt from U.S. federal income tax, the fund may invest up to 50% of its net assets in municipal bonds, the income from which is subject to the federal alternative minimum tax. A rigorous sell discipline is employed to continuously evaluate all fund holdings. Current holdings may become sell candidates if creditworthiness is deteriorating, if bonds with better risk and return characteristics become available, or if the holding no longer meets the sub-adviser's strategic or portfolio construction objectives. The fund may, but is not required to, use derivative instruments as a substitute for investing directly in an underlying asset, to increase returns, to manage credit or interest rate risk, to manage the effective duration or maturity of the fund's portfolio, or as part of a hedging strategy. The derivative instruments in which the fund may invest typically include options, futures and options on futures (including those relating to securities, indices, and interest rates), and swaps (including total return swaps, interest rate swaps such as Municipal Market Data Rate Locks (MMD Rate Locks), and credit default swaps). To the extent the fund invests in derivative instruments that have economic characteristics similar to municipal bonds that provide income exempt from U.S. federal income tax as described in the fund's policy with respect to the investment of at least 80% of its net assets, the market value of such instruments will be included in the 80% calculation. Show less