Loans, Loans by Past Due Status (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Summarized details of Loans
Current	$ 19,508,627	$ 18,510,978
Financing Receivable, Recorded Investment, Nonaccrual Status	282,602	178,258
Total loans	19,815,286	18,714,343
Accruing loans past due 90 days or more	1,000	2,000
Nonaccrual Loans, Current Portion	$ 236,000	$ 124,000
Percent of current nonaccrual loans	84.00%	69.00%
Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	$ 19,593	$ 20,181
Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	2,970	3,278
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	1,494	1,648
Commercial and industrial
Summarized details of Loans
Current	6,506,175	6,095,848
Financing Receivable, Recorded Investment, Nonaccrual Status	193,439	93,575
Total loans	6,701,986	6,190,683
Commercial and industrial | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	1,755	602
Commercial and industrial | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	369	409
Commercial and industrial | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	248	249
Commercial real estate — owner occupied
Summarized details of Loans
Current	911,908	903,021
Financing Receivable, Recorded Investment, Nonaccrual Status	9,635	8,049
Total loans	921,736	918,212
Commercial real estate — owner occupied | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	193	7,142
Commercial real estate — owner occupied | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Commercial real estate — owner occupied | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Commercial and business lending
Summarized details of Loans
Current	7,418,083	6,998,869
Financing Receivable, Recorded Investment, Nonaccrual Status	203,074	101,624
Total loans	7,623,722	7,108,895
Commercial and business lending | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	1,948	7,744
Commercial and business lending | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	369	409
Commercial and business lending | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	248	249
Commercial real estate — investor
Summarized details of Loans
Current	3,481,548	3,225,332
Financing Receivable, Recorded Investment, Nonaccrual Status	11,528	8,643
Total loans	3,495,791	3,234,266
Commercial real estate — investor | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	2,715	291
Commercial real estate — investor | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Commercial real estate — investor | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Real estate construction
Summarized details of Loans
Current	1,284,092	1,160,909
Financing Receivable, Recorded Investment, Nonaccrual Status	957	940
Total loans	1,285,573	1,162,145
Real estate construction | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	427	270
Real estate construction | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	97	26
Real estate construction | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Commercial Real Estate Lending [Member]
Summarized details of Loans
Current	4,765,640	4,386,241
Financing Receivable, Recorded Investment, Nonaccrual Status	12,485	9,583
Total loans	4,781,364	4,396,411
Commercial Real Estate Lending [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	3,142	561
Commercial Real Estate Lending [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	97	26
Commercial Real Estate Lending [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Commercial Financing Receivable [Member]
Summarized details of Loans
Current	12,183,723	11,385,110
Financing Receivable, Recorded Investment, Nonaccrual Status	215,559	111,207
Total loans	12,405,086	11,505,306
Commercial Financing Receivable [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	5,090	8,305
Commercial Financing Receivable [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	466	435
Commercial Financing Receivable [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	248	249
Residential mortgage
Summarized details of Loans
Current	5,976,038	5,726,855
Financing Receivable, Recorded Investment, Nonaccrual Status	52,300	51,482
Total loans	6,035,720	5,783,267
Residential mortgage | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	7,040	4,491
Residential mortgage | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	342	439
Residential mortgage | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Home equity
Summarized details of Loans
Current	946,678	982,639
Financing Receivable, Recorded Investment, Nonaccrual Status	14,363	15,244
Total loans	968,771	1,005,802
Home equity | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	6,150	6,190
Home equity | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	1,580	1,729
Home equity | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	0	0
Other consumer
Summarized details of Loans
Current	402,188	416,374
Financing Receivable, Recorded Investment, Nonaccrual Status	380	325
Total loans	405,709	419,968
Other consumer | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	1,313	1,195
Other consumer | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	582	675
Other consumer | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	1,246	1,399
Consumer Loan [Member]
Summarized details of Loans
Current	7,324,904	7,125,868
Financing Receivable, Recorded Investment, Nonaccrual Status	67,043	67,051
Total loans	7,410,200	7,209,037
Consumer Loan [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Summarized details of Loans
Total Past Due	14,503	11,876
Consumer Loan [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Summarized details of Loans
Total Past Due	2,504	2,843
Consumer Loan [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Summarized details of Loans
Total Past Due	$ 1,246	$ 1,399