Derivative Financial Instruments (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Derivative Financial Instruments Not Designated as Hedging Instruments
Asset Derivatives	$ 27,712		$ 27,712		$ 30,891
Liability Derivatives	26,953		26,953		28,106
Net Gains (Losses) Recognized in the Statements of Income	2,649	3,823	5,291	6,763
Interest Rate Lock Commitments
Derivative Financial Instruments Not Designated as Hedging Instruments
Asset Derivatives	681		681		1,531
Liability Derivatives	31		31		1,648
Interest Rate Lock Commitments | Mortgage Banking
Derivative Financial Instruments Not Designated as Hedging Instruments
Net Gains (Losses) Recognized in the Statements of Income	1,908	4,886	3,389	7,245
Forward Commitments
Derivative Financial Instruments Not Designated as Hedging Instruments
Asset Derivatives	171		171		3,114
Liability Derivatives	45		45		155
Forward Commitments | Mortgage Banking
Derivative Financial Instruments Not Designated as Hedging Instruments
Net Gains (Losses) Recognized in the Statements of Income	(341)	(1,689)	(105)	(2,008)
Interest Rate Swap Agreements
Derivative Financial Instruments Not Designated as Hedging Instruments
Asset Derivatives	26,637		26,637		25,982
Liability Derivatives	26,855		26,855		26,197
Interest Rate Swap Agreements | Other Noninterest Income
Derivative Financial Instruments Not Designated as Hedging Instruments
Net Gains (Losses) Recognized in the Statements of Income	339	(41)	367	113
Foreign Exchange Contracts
Derivative Financial Instruments Not Designated as Hedging Instruments
Asset Derivatives	223		223		264
Liability Derivatives	22		22		106
Foreign Exchange Contracts | Other Noninterest Income
Derivative Financial Instruments Not Designated as Hedging Instruments
Net Gains (Losses) Recognized in the Statements of Income	$ 743	$ 667	$ 1,640	$ 1,413