Credit Quality (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	$ 6,212,746	$ 6,240,213
Corporate Credit Exposure [Member] | Owner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	740,373	743,502
Corporate Credit Exposure [Member] | Nonowner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	1,579,814	1,553,259
Corporate Credit Exposure [Member] | Other Commercial [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	1,180,690	1,212,205
Corporate Credit Exposure [Member] | Construction & land development [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	569,223	549,877
Corporate Credit Exposure [Member] | Pass [Member] | Owner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	684,714	679,651
Corporate Credit Exposure [Member] | Pass [Member] | Nonowner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	1,436,098	1,407,006
Corporate Credit Exposure [Member] | Pass [Member] | Other Commercial [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	1,061,332	1,073,347
Corporate Credit Exposure [Member] | Pass [Member] | Construction & land development [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	488,618	462,517
Corporate Credit Exposure [Member] | Special Mention [Member] | Owner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	29,946	38,150
Corporate Credit Exposure [Member] | Special Mention [Member] | Nonowner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	63,138	67,035
Corporate Credit Exposure [Member] | Special Mention [Member] | Other Commercial [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	61,860	78,158
Corporate Credit Exposure [Member] | Special Mention [Member] | Construction & land development [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	28,853	41,093
Corporate Credit Exposure [Member] | Substandard [Member] | Owner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	25,713	25,701
Corporate Credit Exposure [Member] | Substandard [Member] | Nonowner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	80,578	79,218
Corporate Credit Exposure [Member] | Substandard [Member] | Other Commercial [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	54,504	57,436
Corporate Credit Exposure [Member] | Substandard [Member] | Construction & land development [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	51,752	45,267
Corporate Credit Exposure [Member] | Doubtful [Member] | Owner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	0	0
Corporate Credit Exposure [Member] | Doubtful [Member] | Nonowner-occupied [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	0	0
Corporate Credit Exposure [Member] | Doubtful [Member] | Other Commercial [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	2,994	3,264
Corporate Credit Exposure [Member] | Doubtful [Member] | Construction & land development [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	0	1,000
Consumer Credit Exposure [Member] | Residential Real Estate [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	1,862,806	1,897,658
Consumer Credit Exposure [Member] | Bankcard [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	10,574	11,519
Consumer Credit Exposure [Member] | Other consumer [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	269,266	272,193
Consumer Credit Exposure [Member] | Pass [Member] | Residential Real Estate [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	1,773,587	1,790,296
Consumer Credit Exposure [Member] | Pass [Member] | Bankcard [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	10,136	11,079
Consumer Credit Exposure [Member] | Pass [Member] | Other consumer [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	265,338	265,995
Consumer Credit Exposure [Member] | Special Mention [Member] | Residential Real Estate [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	39,330	56,722
Consumer Credit Exposure [Member] | Special Mention [Member] | Bankcard [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	318	304
Consumer Credit Exposure [Member] | Special Mention [Member] | Other consumer [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	3,488	5,366
Consumer Credit Exposure [Member] | Substandard [Member] | Residential Real Estate [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	49,889	50,640
Consumer Credit Exposure [Member] | Substandard [Member] | Bankcard [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	120	136
Consumer Credit Exposure [Member] | Substandard [Member] | Other consumer [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	440	832
Consumer Credit Exposure [Member] | Doubtful [Member] | Residential Real Estate [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	0	0
Consumer Credit Exposure [Member] | Doubtful [Member] | Bankcard [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	0	0
Consumer Credit Exposure [Member] | Doubtful [Member] | Other consumer [Member]
Schedule of Credit Quality Indicators Information, by Class of Loans
Financing receivable, credit quality indicators information	$ 0	$ 0