Derivative Financial Instruments - Master Netting Arrangements (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	$ 361,598	$ 156,461
Net Amounts of Assets Presented in the Statement of Financial Position	361,598	156,461
Gross Assets Offset Under Master Netting Arrangements, Total	0	0
Gross Assets Subect To Master Netting Arrangement Not Offset	(348,609)	(143,857)
Cash Collateral Received Subject to Master Netting Arrangements	(7,460)	(6,110)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	5,529	6,494
Gross Amounts of Recognized Liabilities	12,204	13,437
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	12,204	13,437
Gross Liabilities Subect To Master Netting Arrangement Not Offset	(4,733)	(7,258)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	7,471	6,179
Derivative
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	22,911	23,104
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	22,911	23,104
Gross Assets Subect To Master Netting Arrangement Not Offset	(9,922)	(10,500)
Cash Collateral Received Subject to Master Netting Arrangements	(7,460)	(6,110)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	5,529	6,494
Gross Amounts of Recognized Liabilities	12,204	13,437
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	12,204	13,437
Gross Liabilities Subect To Master Netting Arrangement Not Offset	(4,733)	(7,258)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	7,471	6,179
Derivative | Interest rate swaps
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	8,506	9,005
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	8,506	9,005
Gross Assets Subect To Master Netting Arrangement Not Offset	(1,046)	(2,895)
Cash Collateral Received Subject to Master Netting Arrangements	(7,460)	(6,110)
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	13,267	12,352
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	13,267	12,352
Gross Assets Subect To Master Netting Arrangement Not Offset	(8,364)	(7,363)
Cash Collateral Received Subject to Master Netting Arrangements	0	0
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	4,903	4,989
Gross Amounts of Recognized Liabilities	11,028	11,658
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	11,028	11,658
Gross Liabilities Subect To Master Netting Arrangement Not Offset	(4,069)	(5,720)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	6,959	5,938
Derivative | Client foreign currency options
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	485	1,189
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	485	1,189
Gross Assets Subect To Master Netting Arrangement Not Offset	(485)	(218)
Cash Collateral Received Subject to Master Netting Arrangements	0	0
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	0	971
Gross Amounts of Recognized Liabilities	485	1,189
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	485	1,189
Gross Liabilities Subect To Master Netting Arrangement Not Offset	0	(971)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	485	218
Derivative | Client interest rate derivatives
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	653	558
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	653	558
Gross Assets Subect To Master Netting Arrangement Not Offset	(27)	(24)
Cash Collateral Received Subject to Master Netting Arrangements	0	0
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	626	534
Gross Amounts of Recognized Liabilities	691	590
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	691	590
Gross Liabilities Subect To Master Netting Arrangement Not Offset	(664)	(567)
Cash Collateral Pledged Subject to Master Netting Arrangements	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	27	23
Reverse Repurchase Securities Borrowing And Similar Arrangements
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	338,687	133,357
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	338,687	133,357
Gross Assets Subect To Master Netting Arrangement Not Offset	(338,687)	(133,357)
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 Subect 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