Loans, Commercial Loans by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Commercial loans by credit quality indicator
Commercial and industrial	$ 6,147,440	$ 5,905,902
Commercial real estate — owner occupied	918,212	1,007,937
Lease financing	43,243	51,529
Commercial and business lending	7,108,895	6,965,368
Commercial real estate — investor	3,234,266	3,056,485
Real estate construction	1,162,145	1,008,956
Commercial real estate lending	4,396,411	4,065,441
Total commercial	11,505,306	11,030,809
Pass [Member]
Commercial loans by credit quality indicator
Commercial and industrial	5,455,573	5,594,497
Commercial real estate — owner occupied	827,694	904,526
Lease financing	37,969	46,931
Commercial and business lending	6,321,236	6,545,954
Commercial real estate — investor	3,150,134	2,974,493
Real estate construction	1,156,524	998,972
Commercial real estate lending	4,306,658	3,973,465
Total commercial	10,627,894	10,519,419
Special Mention [Member]
Commercial loans by credit quality indicator
Commercial and industrial	339,953	119,328
Commercial real estate — owner occupied	38,886	18,437
Lease financing	1,190	88
Commercial and business lending	380,029	137,853
Commercial real estate — investor	27,630	12,137
Real estate construction	252	2,082
Commercial real estate lending	27,882	14,219
Total commercial	407,911	152,072
Potential Problem [Member]
Commercial loans by credit quality indicator
Commercial and industrial	230,680	108,522
Commercial real estate — owner occupied	35,706	48,695
Lease financing	2,450	2,709
Commercial and business lending	268,836	159,926
Commercial real estate — investor	25,944	24,043
Real estate construction	3,919	1,776
Commercial real estate lending	29,863	25,819
Total commercial	298,699	185,745
Impaired [Member]
Commercial loans by credit quality indicator
Commercial and industrial	121,234	83,555
Commercial real estate — owner occupied	15,926	36,279
Lease financing	1,634	1,801
Commercial and business lending	138,794	121,635
Commercial real estate — investor	30,558	45,812
Real estate construction	1,450	6,126
Commercial real estate lending	32,008	51,938
Total commercial	$ 170,802	$ 173,573

Commercial and business lending subtotal

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Commercial Real Estate Investor loans receivable.

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Amount before allowance of commercial leases and leveraged lease transactions where the entity is long-term creditor. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes leases covered under loss sharing agreements.

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Amount before allowance of loans issued to commercial and industrial institutions. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes real estate loans and loans covered under loss sharing agreements.

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Amount before allowance of commercial construction loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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