Derivative Financial Instruments Master Netting Arrangements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Offsetting Derivative Assets [Abstract]
Fair value	$ 108,389	$ 78,947
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	108,389	78,947
Derivative, Collateral, Obligation to Return Securities	(26,754)	(42,356)
Derivative, Collateral, Obligation to Return Cash	(3,730)	(12,668)
Derivative Asset, Fair Value, Amount Offset Against Collateral	77,905	23,923
Offsetting Securities Purchased under Agreements to Resell [Abstract]
Securities Purchased under Agreements to Resell, Gross	247,876	64,028
Securities Purchased under Agreements to Resell, Liability	0	0
Securities Purchased under Agreements to Resell	247,876	64,028
Securities Purchased under Agreements to Resell, Collateral, Obligation to Return Securities	(247,876)	(64,028)
Securities Purchased under Agreements to Resell, Collateral, Obligation to Return Cash	0	0
Securities Purchased under Agreements to Resell, Amount Offset Against Collateral	0	0
Offsetting Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed [Abstract]
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Gross	356,265	142,975
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Liability	0	0
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed	356,265	142,975
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Securities	(274,630)	(106,384)
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Cash	(3,730)	(12,668)
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Amount Offset Against Collateral	77,905	23,923
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	(108,581)	(64,438)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability	108,581	64,438
Derivative, Collateral, Right to Reclaim Securities	92,662	29,319
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(15,919)	(35,119)
Offsetting Securities Sold under Agreements to Repurchase [Abstract]
Securities Sold under Agreements to Repurchase, Gross	0	0
Securities Sold under Agreements to Repurchase, Asset	0	0
Securities Sold under Agreements to Repurchase	0	0
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	0	0
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash	0	0
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral	0	0
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract]
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Gross	(108,581)	(64,438)
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Asset	0	0
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned	(108,581)	(64,438)
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Collateral, Right to Reclaim Securities	92,662	29,319
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Amount Offset Against Collateral	(15,919)	(35,119)
Interest rate swaps
Offsetting Derivative Assets [Abstract]
Fair value	0	810
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	0	810
Derivative, Collateral, Obligation to Return Securities	0	(721)
Derivative, Collateral, Obligation to Return Cash	0	(89)
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Foreign exchange forwards
Offsetting Derivative Assets [Abstract]
Fair value	95,449	57,644
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	95,449	57,644
Derivative, Collateral, Obligation to Return Securities	(14,456)	(22,738)
Derivative, Collateral, Obligation to Return Cash	(3,730)	(12,579)
Derivative Asset, Fair Value, Amount Offset Against Collateral	77,263	22,327
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	(95,454)	(44,285)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability	95,454	44,285
Derivative, Collateral, Right to Reclaim Securities	80,107	17,964
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(15,347)	(26,321)
Foreign currency options
Offsetting Derivative Assets [Abstract]
Fair value	1,187	10,383
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	1,187	10,383
Derivative, Collateral, Obligation to Return Securities	(557)	(8,806)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	630	1,577
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	(1,187)	(10,383)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability	1,187	10,383
Derivative, Collateral, Right to Reclaim Securities	631	1,585
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(556)	(8,798)
Client interest rate derivatives
Offsetting Derivative Assets [Abstract]
Fair value	11,753	10,110
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	11,753	10,110
Derivative, Collateral, Obligation to Return Securities	(11,741)	(10,091)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	12	19
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	(11,940)	(9,770)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability	11,940	9,770
Derivative, Collateral, Right to Reclaim Securities	11,924	9,770
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ (16)	$ 0