Derivative Financial Instruments - Master Netting Arrangements (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	$ 298,052	$ 137,271
Gross Amounts offset in the Statement of Financial Position	(283)	(274)
Net Amounts of Assets Presented in the Statement of Financial Position	297,769	136,997
Gross Assets Subject To Master Netting Arrangement Not Offset	(265,184)	(117,783)
Cash Collateral Received Subject to Master Netting Arrangements	(17,766)	(7,781)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	14,819	11,433
Gross Amounts of Recognized Liabilities	49,176	31,385
Gross Amounts offset in the Statement of Financial Position	(283)	(274)
Net Amounts of Liabilities Presented in the Statement of Financial Position	48,893	31,111
Gross Liabilities Subject To Master Netting Arrangement Not Offset	(11,903)	(19,639)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	36,990	11,472
Derivative
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	62,025	41,660
Gross Amounts offset in the Statement of Financial Position	(283)	(274)
Net Amounts of Assets Presented in the Statement of Financial Position	61,742	41,386
Gross Assets Subject To Master Netting Arrangement Not Offset	(29,157)	(22,172)
Cash Collateral Received Subject to Master Netting Arrangements	(17,766)	(7,781)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	14,819	11,433
Gross Amounts of Recognized Liabilities	49,176	31,385
Gross Amounts offset in the Statement of Financial Position	(283)	(274)
Net Amounts of Liabilities Presented in the Statement of Financial Position	48,893	31,111
Gross Liabilities Subject To Master Netting Arrangement Not Offset	(11,903)	(19,639)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	36,990	11,472
Derivative | Interest rate swaps
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	4,340	4,609
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	4,340	4,609
Gross Assets Subject To Master Netting Arrangement Not Offset	(1,370)	(1,639)
Cash Collateral Received Subject to Master Netting Arrangements	(2,970)	(2,970)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	0	0
Derivative | Foreign exchange forwards
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	53,972	34,004
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	53,972	34,004
Gross Assets Subject To Master Netting Arrangement Not Offset	(24,627)	(17,843)
Cash Collateral Received Subject to Master Netting Arrangements	(14,796)	(4,811)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	14,549	11,350
Gross Amounts of Recognized Liabilities	45,204	28,136
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	45,204	28,136
Gross Liabilities Subject To Master Netting Arrangement Not Offset	(8,467)	(16,808)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	36,737	11,328
Derivative | Client foreign currency options
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	806	501
Gross Amounts offset in the Statement of Financial Position	(283)	(274)
Net Amounts of Assets Presented in the Statement of Financial Position	523	227
Gross Assets Subject To Master Netting Arrangement Not Offset	(253)	(144)
Cash Collateral Received Subject to Master Netting Arrangements	0	0
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	270	83
Gross Amounts of Recognized Liabilities	806	501
Gross Amounts offset in the Statement of Financial Position	(283)	(274)
Net Amounts of Liabilities Presented in the Statement of Financial Position	523	227
Gross Liabilities Subject To Master Netting Arrangement Not Offset	(270)	(83)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	253	144
Derivative | Client interest rate derivatives
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	2,907	2,546
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	2,907	2,546
Gross Assets Subject To Master Netting Arrangement Not Offset	(2,907)	(2,546)
Cash Collateral Received Subject to Master Netting Arrangements	0	0
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	0	0
Gross Amounts of Recognized Liabilities	3,166	2,748
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	3,166	2,748
Gross Liabilities Subject To Master Netting Arrangement Not Offset	(3,166)	(2,748)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	0	0
Reverse Repurchase Securities Borrowing And Similar Arrangements
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	236,027	95,611
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	236,027	95,611
Gross Assets Subject To Master Netting Arrangement Not Offset	(236,027)	(95,611)
Cash Collateral Received Subject to Master Netting Arrangements	0	0
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	0	0
Gross Amounts of Recognized Liabilities	0	0
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	0	0
Gross Liabilities Subject To Master Netting Arrangement Not Offset	0	0
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	$ 0	$ 0