Fair Values of Assets and Liabilities Unrealized and Realized Gain (Loss) on Trading Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Net Realized and Unrealized Gain (Loss) on Trading Securities	$ (31,460)	$ (8,515)	$ (27,431)	$ 1,923
Net Unrealized Loss on Trading Securities	$ (32,755)	$ (17,612)	$ (43,165)	$ (18,266)