Loans and Allowances for Credit Losses, Activity in Allowance for Credit Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Allowance for loan losses [Roll Forward]
Beginning balance	$ 189,056	$ 185,396
Provision for loan losses	276us-gaap_ProvisionForLoanAndLeaseLosses	410us-gaap_ProvisionForLoanAndLeaseLosses
Loans charged off	(2,169)	(2,848)
Recoveries	10,523	5,360
Ending balance	197,686	188,318
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	1,230	2,088
Provision for off-balance sheet credit losses	(276)us-gaap_ProvisionForOtherCreditLosses	(410)us-gaap_ProvisionForOtherCreditLosses
Ending balance	954	1,678
Total provision for credit losses	0	0
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	14,603,403	12,973,148	14,127,266
Individually measured for impairment, recorded investment	80,733	104,706	80,771
Total	14,684,136	13,077,854	14,208,037
Related allowance [Abstract]
Collectively measured for impairment, related allowance	169,296	157,194	160,699
Individually measured for impairment, related allowance	317	4,159	312
Total measured for impairment, related allowance	197,686	188,318
Commercial [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	90,875	79,180
Provision for loan losses	10,353	4,225
Loans charged off	(174)	(144)
Recoveries	357	1,985
Ending balance	101,411	85,246
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	475	119
Provision for off-balance sheet credit losses	102	457
Ending balance	577	576
Total provision for credit losses	10,455	4,682
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	9,377,283	8,032,659	9,082,143
Individually measured for impairment, recorded investment	13,880	19,047	13,527
Total	9,391,163	8,051,706	9,095,670
Related allowance [Abstract]
Collectively measured for impairment, related allowance	101,214	81,813	90,709
Individually measured for impairment, related allowance	197	3,433	166
Total measured for impairment, related allowance	101,411	85,246
Commercial Real Estate [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	42,445	41,573
Provision for loan losses	(10,417)	(1,591)
Loans charged off	(28)	(220)
Recoveries	8,819	1,827
Ending balance	40,819	41,589
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	707	1,876
Provision for off-balance sheet credit losses	(374)	(836)
Ending balance	333	1,040
Total provision for credit losses	(10,791)	(2,427)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	2,915,562	2,592,102	2,709,593
Individually measured for impairment, recorded investment	19,902	39,305	18,557
Total	2,935,464	2,631,407	2,728,150
Related allowance [Abstract]
Collectively measured for impairment, related allowance	40,801	41,404	42,404
Individually measured for impairment, related allowance	18	185	41
Total measured for impairment, related allowance	40,819	41,589
Residential Mortgage [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	23,458	29,465
Provision for loan losses	(27)	(516)
Loans charged off	(624)	(996)
Recoveries	437	354
Ending balance	23,244	28,307
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	28	90
Provision for off-balance sheet credit losses	(4)	(28)
Ending balance	24	62
Total provision for credit losses	(31)	(544)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	1,880,512	1,973,295	1,901,391
Individually measured for impairment, recorded investment	46,487	45,380	48,121
Total	1,926,999	2,018,675	1,949,512
Related allowance [Abstract]
Collectively measured for impairment, related allowance	23,142	27,766	23,353
Individually measured for impairment, related allowance	102	541	105
Total measured for impairment, related allowance	23,244	28,307
Consumer [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	4,233	6,965
Provision for loan losses	339	(460)
Loans charged off	(1,343)	(1,488)
Recoveries	910	1,194
Ending balance	4,139	6,211
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	20	3
Provision for off-balance sheet credit losses	0	(3)
Ending balance	20	0
Total provision for credit losses	339	(463)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	430,046	375,092	434,139
Individually measured for impairment, recorded investment	464	974	566
Total	430,510	376,066	434,705
Related allowance [Abstract]
Collectively measured for impairment, related allowance	4,139	6,211	4,233
Individually measured for impairment, related allowance	0	0	0
Total measured for impairment, related allowance	4,139	6,211
Specific Allowance [Member]
Allowance for loan losses [Roll Forward]
Beginning balance			161,011
Ending balance	169,613	161,353	161,011
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	14,603,403	12,973,148	14,127,266
Individually measured for impairment, recorded investment	80,733	104,706	80,771
Total	14,684,136	13,077,854	14,208,037
Related allowance [Abstract]
Collectively measured for impairment, related allowance	169,296	157,194	160,699
Individually measured for impairment, related allowance	317	4,159	312
Total measured for impairment, related allowance	169,613	161,353	161,011
Nonspecific Allowance [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	28,045	28,213
Provision for loan losses	28	(1,248)
Loans charged off	0	0
Recoveries	0	0
Ending balance	28,073	26,965
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	0	0
Provision for off-balance sheet credit losses	0	0
Ending balance	0	0
Total provision for credit losses	28	(1,248)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	0	0	0
Individually measured for impairment, recorded investment	0	0	0
Total	0	0	0
Related allowance [Abstract]
Collectively measured for impairment, related allowance	0	0	0
Individually measured for impairment, related allowance	0	0	0
Total measured for impairment, related allowance	$ 28,073	$ 26,965

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

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