Derivatives (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative liabilities	$ 74,935	$ 82,323
Net reductions to interest expense related to net settlements of derivatives	1,000	3,000	$ 3,600
Derivative assets	66,146	83,780
Collateral posted	28,796	36,349
Credit-Risk-Related Contingent Features
Derivative [Line Items]
Aggregate fair value of derivative instruments in net liability position	6,300	7,100
Collateral posted	6,200	9,100
Derivative instruments designated as hedging instruments
Derivative [Line Items]
Notional amount	35,811	131,391
Derivative liabilities	6,799	5,976
Derivative assets	0	4,325
Derivative instruments designated as hedging instruments | Interest rate swaps on certificates of deposit
Derivative [Line Items]
Notional amount	35,811	48,365
Derivative liabilities	6,799	5,976
Derivative assets	0	0
Derivative instruments designated as hedging instruments | Foreign currency forward contracts
Derivative [Line Items]
Notional amount	0	83,026
Derivative liabilities	0	0
Derivative assets	0	4,325
Derivative instruments not designated as hedging instruments
Derivative [Line Items]
Notional amount	10,153,108	8,507,660
Derivative liabilities	68,136	76,347
Derivative assets	66,146	79,455
Derivative instruments not designated as hedging instruments | Public Companies
Derivative [Line Items]
Derivative assets	993
Derivative instruments not designated as hedging instruments | Interest rate swaps and options
Derivative [Line Items]
Notional amount	9,333,860	7,668,482
Derivative liabilities	57,958	65,131
Derivative assets	58,633	67,578
Notional amount of derivative assets	4,690,000	3,860,000
Notional amount of derivative liabilities	4,650,000	3,810,000
Derivative instruments not designated as hedging instruments | Credit risk participation agreements (“RPAs”)
Derivative [Line Items]
Notional amount	49,033	71,414
Derivative liabilities	8	3
Derivative assets	$ 1	$ 3
Weighted average remaining maturity	6 years	3 years 8 months
Derivative instruments not designated as hedging instruments | Credit risk participation agreements (“RPAs”) | Long
Derivative [Line Items]
Notional amount	$ 35,200	$ 48,300
Derivative liabilities	8	3
Interest rate derivative exposure	419	179
Derivative instruments not designated as hedging instruments | Credit risk participation agreements (“RPAs”) | Short
Derivative [Line Items]
Notional amount	13,800	23,100
Derivative assets	$ 1	3
Derivative instruments not designated as hedging instruments | Foreign exchange options
Derivative [Line Items]
Term of contract (in years)	5 years
Derivative instruments not designated as hedging instruments | Private Companies
Derivative [Line Items]
Derivative assets	$ 679
Derivative instruments not designated as hedging instruments | Warrants
Derivative [Line Items]
Notional amount	0	0
Derivative liabilities	0	0
Derivative assets	$ 1,672	$ 0