Derivatives (Derivatives Not Designated as Hedging Instruments - Foreign Exchange Contracts) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative assets - Fair value	$ 99,103	$ 66,146
Derivative liabilities - Fair value	133,702	74,935
Foreign exchange contracts
Derivative [Line Items]
Notional amount		95,200
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	13,254,731	10,153,108
Derivative assets - Fair value	99,042	66,146
Derivative liabilities - Fair value	126,006	68,136
Derivatives not designated as hedging instruments | Foreign exchange contracts
Derivative [Line Items]
Notional amount	1,405,339	770,215
Derivative assets - Fair value	11,034	5,840
Derivative liabilities - Fair value	11,075	10,170
Derivatives not designated as hedging instruments | Customer Counterparties
Derivative [Line Items]
Derivative assets - Fair value	12,915
Derivative liabilities - Fair value	132
Derivatives not designated as hedging instruments | Customer Counterparties | Foreign exchange contracts
Derivative [Line Items]
Notional amount	664,568	167,707
Derivative assets - Fair value	6,782	2,189
Derivative liabilities - Fair value	4,905	850
Derivatives not designated as hedging instruments | Customer Counterparties | Forwards and spot
Derivative [Line Items]
Notional amount	648,305	163,389
Derivative assets - Fair value	6,780	2,189
Derivative liabilities - Fair value	4,815	752
Derivatives not designated as hedging instruments | Customer Counterparties | Swaps
Derivative [Line Items]
Notional amount	15,683	4,318
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	90	98
Derivatives not designated as hedging instruments | Customer Counterparties | Collars
Derivative [Line Items]
Notional amount	580
Derivative assets - Fair value	2
Derivative liabilities - Fair value	0
Derivatives not designated as hedging instruments | Financial Counterparties
Derivative [Line Items]
Derivative assets - Fair value	65
Derivative liabilities - Fair value	7,780
Derivatives not designated as hedging instruments | Financial Counterparties | Foreign exchange contracts
Derivative [Line Items]
Notional amount	740,771	602,508
Derivative assets - Fair value	4,252	3,651
Derivative liabilities - Fair value	6,170	9,320
Derivatives not designated as hedging instruments | Financial Counterparties | Forwards and spot
Derivative [Line Items]
Notional amount	115,547	155,872
Derivative assets - Fair value	127	662
Derivative liabilities - Fair value	213	7,800
Derivatives not designated as hedging instruments | Financial Counterparties | Swaps
Derivative [Line Items]
Notional amount	624,644	446,636
Derivative assets - Fair value	4,125	2,989
Derivative liabilities - Fair value	5,955	$ 1,520
Derivatives not designated as hedging instruments | Financial Counterparties | Collars
Derivative [Line Items]
Notional amount	580
Derivative assets - Fair value	0
Derivative liabilities - Fair value	$ 2