Derivatives (Derivatives Associated with Fixed Income Trading Activities) (Details) - USD ($)	Mar. 31, 2016	Mar. 31, 2015
Customer Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional	$ 1,822,343,000	$ 1,675,215,000
Assets	87,287,000	83,797,000
Liabilities	935,000	2,241,000
Offsetting Upstream Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional	1,822,343,000	1,675,215,000
Assets	935,000	2,241,000
Liabilities	87,287,000	83,797,000
Put Option [Member] | ShortMember
Derivative Instruments, Gain (Loss) [Line Items]
Notional		7,500,000
Assets		0
Liabilities		12,000
Put Option [Member] | LongMember
Derivative Instruments, Gain (Loss) [Line Items]
Notional	5,000,000	12,500,000
Assets	9,000	60,000
Liabilities	0	0
Forwards And Futures Purchased [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,673,789,000	3,181,574,000
Assets	12,939,000	5,805,000
Liabilities	423,000	538,000
Forwards And Futures Sold [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,925,911,000	3,511,607,000
Assets	1,086,000	1,105,000
Liabilities	$ 12,806,000	$ 7,290,000