Derivatives (Derivatives Associated with Fixed Income Trading Activities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Customer Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	$ 1,903,647	$ 1,697,992
Assets	34,224	39,495
Liabilities	12,508	14,996
Offsetting Upstream Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	1,903,647	1,697,992
Assets	12,368	14,996
Liabilities	31,374	39,495
Put Option | Short
Derivative Instruments, Gain (Loss) [Line Items]
Notional		5,000
Assets		0
Liabilities		8
Put Option | Long
Derivative Instruments, Gain (Loss) [Line Items]
Notional	25,000	17,500
Assets	78	63
Liabilities	0	0
Forwards And Futures Purchased
Derivative Instruments, Gain (Loss) [Line Items]
Notional	4,245,499	2,916,750
Assets	3,403	6,257
Liabilities	10,366	26,659
Forwards And Futures Sold
Derivative Instruments, Gain (Loss) [Line Items]
Notional	4,562,708	3,085,396
Assets	12,646	27,330
Liabilities	$ 2,212	$ 6,615