Consolidated Statements of Income and Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Interest income:
Loans and loans held for sale	$ 103,126	$ 107,904	$ 206,208	$ 222,460
Investment securities:
Taxable	21,783	22,176	44,201	43,661
Tax-exempt	3,846	3,137	7,426	6,332
Total investment securities interest	25,629	25,313	51,627	49,993
Total interest income	128,755	133,217	257,835	272,453
Deposits:
Demand-interest bearing	236	177	483	361
Savings and money market accounts	5,033	7,398	10,136	15,243
Certificates and other time deposits	3,169	5,606	6,693	12,433
Securities sold under agreements to repurchase	276	940	544	1,855
Wholesale borrowings	1,118	1,653	2,269	3,292
Total interest expense	9,832	15,774	20,125	33,184
Net interest income	118,923	117,443	237,710	239,269
Provision for noncovered loan losses	8,766	10,138	16,895	27,156
Provision for covered loan losses	3,430	7,481	9,362	12,812
Net interest income after provision for loan losses	106,727	99,824	211,453	199,301
Other income:
Trust department income	5,730	5,863	11,357	11,377
Service charges on deposits	14,478	15,712	28,887	30,622
Credit card fees	11,216	13,510	21,396	25,717
ATM and other service fees	3,890	3,063	7,680	5,980
Bank owned life insurance income	2,923	3,015	5,979	8,256
Investment services and insurance	2,388	1,972	4,635	4,419
Investment securities gains, net	548	889	808	889
Loan sales and servicing income	5,139	2,891	11,830	5,676
Other operating income	8,989	4,576	14,455	11,311
Total other income	55,301	51,491	107,027	104,247
Other expenses:
Salaries, wages, pension and employee benefits	61,598	56,713	125,571	116,583
Net occupancy expense	7,971	8,086	16,563	16,680
Equipment expense	7,598	6,816	14,702	13,652
Stationery, supplies and postage	2,285	2,750	4,428	5,455
Bankcard, loan processing and other costs	8,858	8,266	16,511	15,829
Professional services	9,307	5,940	12,659	11,734
Amortization of intangibles	483	543	966	1,086
FDIC expense	3,463	4,581	7,183	8,947
Other operating expense	17,514	16,373	34,262	34,548
Total other expenses	119,077	110,068	232,845	224,514
Income before income tax expense	42,951	41,247	85,635	79,034
Income tax expense	12,366	11,484	24,706	21,710
Net income	30,585	29,763	60,929	57,324
Other comprehensive income (loss), net of taxes:
Changes in unreaized securities' holding gains and losses	4,103	17,198	5,987	17,536
Reclassification for realized securities' gains	(356)	(578)	(525)	(578)
Total other comprehensive gain (loss), net of taxes	3,747	16,620	5,462	16,958
Comprehensive income	34,332	46,383	66,391	74,282
Net income available to common shareholders	30,585	29,763	60,929	57,324
Net income used in diluted EPS calculation	$ 30,585	$ 29,763	$ 60,929	$ 57,324
Weighted average number of common shares outstanding - basic	109,562	109,138	109,386	108,954
Average common shares outstanding	109,562	109,139	109,386	108,955
Basic earnings per common share (in dollars per share)	$ 0.28	$ 0.27	$ 0.56	$ 0.53
Diluted earnings per common share (in dollars per share)	$ 0.28	$ 0.27	$ 0.56	$ 0.53
Dividend per common share (in dollars per share)	$ 0.16	$ 0.16	$ 0.32	$ 0
Non stock options [Member]
Other comprehensive income (loss), net of taxes:
Average common shares outstanding			109,386	108,955