Loans and Allowance for Loan Losses (Details 5) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Summary of Age Analysis of Past Due Loans
30-89 days past due	$ 48,476	$ 53,599
Greater than 90 days past due	120,339	109,150
Total past due	168,815	162,749
Current	10,961,458	11,014,277
Total Loans	11,130,273	11,177,026
Recorded investment > 90 days and accruing	3,780	5,880
Originated loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	43,132	51,471
Greater than 90 days past due	107,898	88,178
Total past due	151,030	139,649
Current	5,299,977	4,748,081
Total Loans	5,451,007	4,887,730
Recorded investment > 90 days and accruing	2,524	4,871
Acquired loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	5,344	2,128
Greater than 90 days past due	3,064	2,126
Total past due	8,408	4,254
Current	5,037,074	5,613,599
Total Loans	5,045,482	5,617,853
Recorded investment > 90 days and accruing	1,256	1,009
Covered loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due
Greater than 90 days past due	9,377	18,846
Total past due	9,377	18,846
Current	624,407	652,597
Total Loans	633,784	671,443
Recorded investment > 90 days and accruing
Commercial Loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	20,491	24,939
Greater than 90 days past due	88,301	77,076
Total past due	108,792	102,015
Current	7,883,583	7,960,143
Total Loans	7,992,375	8,062,158
Recorded investment > 90 days and accruing	2,004	3,821
Commercial Loans [Member] | Originated loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	20,153	24,939
Greater than 90 days past due	79,222	58,867
Total past due	99,375	83,806
Current	3,603,153	3,242,166
Total Loans	3,702,528	3,325,972
Recorded investment > 90 days and accruing	1,983	3,821
Commercial Loans [Member] | Acquired loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	338
Greater than 90 days past due	305
Total past due	643
Current	4,064,681	4,496,644
Total Loans	4,065,324	4,496,644
Recorded investment > 90 days and accruing	21
Commercial Loans [Member] | Covered loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due
Greater than 90 days past due	8,774	18,209
Total past due	8,774	18,209
Current	215,749	221,333
Total Loans	224,523	239,542
Recorded investment > 90 days and accruing
Residential mortgage Loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	23,857	22,248
Greater than 90 days past due	27,689	26,037
Total past due	51,546	48,285
Current	1,459,803	1,459,213
Total Loans	1,511,349	1,507,498
Recorded investment > 90 days and accruing	1,582	994
Residential mortgage Loans [Member] | Originated loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	19,161	22,248
Greater than 90 days past due	24,636	25,400
Total past due	43,797	47,648
Current	520,421	439,499
Total Loans	564,218	487,147
Recorded investment > 90 days and accruing	383	994
Residential mortgage Loans [Member] | Acquired loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	4,696
Greater than 90 days past due	2,450
Total past due	7,146
Current	664,129	734,669
Total Loans	671,275	734,669
Recorded investment > 90 days and accruing	1,199
Residential mortgage Loans [Member] | Covered loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due
Greater than 90 days past due	603	637
Total past due	603	637
Current	275,253	285,045
Total Loans	275,856	285,682
Recorded investment > 90 days and accruing
Consumer loan [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	4,128	6,412
Greater than 90 days past due	4,349	6,037
Total past due	8,477	12,449
Current	1,618,072	1,594,921
Total Loans	1,626,549	1,607,370
Recorded investment > 90 days and accruing	194	1,065
Consumer loan [Member] | Originated loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	3,818	4,284
Greater than 90 days past due	4,040	3,911
Total past due	7,858	8,195
Current	1,176,403	1,066,416
Total Loans	1,184,261	1,074,611
Recorded investment > 90 days and accruing	158	56
Consumer loan [Member] | Acquired loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due	310	2,128
Greater than 90 days past due	309	2,126
Total past due	619	4,254
Current	308,264	382,286
Total Loans	308,883	386,540
Recorded investment > 90 days and accruing	36	1,009
Consumer loan [Member] | Covered loans [Member]
Summary of Age Analysis of Past Due Loans
30-89 days past due
Greater than 90 days past due
Total past due
Current	133,405	146,219
Total Loans	133,405	146,219
Recorded investment > 90 days and accruing