Derivatives (Details) $ in Thousands	Sep. 30, 2017 USD ($) company	Dec. 31, 2016 USD ($)
Fair Values of Derivative Instruments
Derivative Assets	$ 80,466	$ 83,780
Derivative Liabilities	90,915	82,323
Derivatives designated as hedging instruments
Fair Values of Derivative Instruments
Notional Amount	42,566	131,391
Derivative Assets	0	4,325
Derivative Liabilities	6,648	5,976
Derivatives designated as hedging instruments | Interest rate swaps on certificates of deposit
Fair Values of Derivative Instruments
Notional Amount	42,566	48,365
Derivative Assets	0	0
Derivative Liabilities	6,648	5,976
Derivatives designated as hedging instruments | Foreign currency forward contracts
Fair Values of Derivative Instruments
Notional Amount	0	83,026
Derivative Assets	0	4,325
Derivative Liabilities	0	0
Derivatives not designated as hedging instruments
Fair Values of Derivative Instruments
Notional Amount	9,942,781	8,507,660
Derivative Assets	80,466	79,455
Derivative Liabilities	84,267	76,347
Derivatives not designated as hedging instruments | Interest rate swaps and options
Fair Values of Derivative Instruments
Notional Amount	8,742,980	7,668,482
Derivative Assets	64,822	67,578
Derivative Liabilities	64,212	65,131
Derivatives not designated as hedging instruments | Foreign exchange contracts
Fair Values of Derivative Instruments
Notional Amount	1,131,414	767,764
Derivative Assets	14,187	11,874
Derivative Liabilities	20,054	11,213
Derivatives not designated as hedging instruments | RPAs
Fair Values of Derivative Instruments
Notional Amount	68,387	71,414
Derivative Assets	2	3
Derivative Liabilities	1	3
Derivatives not designated as hedging instruments | Warrants
Fair Values of Derivative Instruments
Notional Amount	0	0
Derivative Assets	1,455	0
Derivative Liabilities	0	$ 0
Derivatives not designated as hedging instruments | Warrant, Public Companies
Fair Values of Derivative Instruments
Derivative Assets	$ 856
Number of companies in which warrants are held | company	4
Derivatives not designated as hedging instruments | Warrant, Private Companies
Fair Values of Derivative Instruments
Derivative Assets	$ 599
Number of companies in which warrants are held | company	32