Loans, Allowance for Loan Losses, and Credit Quality Changes in the Allowance for Loan Losses by Portfolio Segment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	$ 268,315	$ 297,409	$ 378,151
Provision for loan losses	13,000us-gaap_ProvisionForLoanAndLeaseLosses	10,000us-gaap_ProvisionForLoanAndLeaseLosses	3,000us-gaap_ProvisionForLoanAndLeaseLosses
Charge offs	(44,096)	(88,061)	(117,046)
Recoveries	29,083	48,967	33,304
Loans and Leases Receivable, Allowance, Ending Balance	266,302	268,315	297,409
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	17,866	13,637
Ending balance impaired loans collectively evaluated for impairment	32,565	38,238
Total Impaired Loans, Related Allowance	50,431	51,875
Ending balance all other loans collectively evaluated for impairment	215,871	216,440
Loans and Leases Receivable, Allowance, Total	266,302	268,315	297,409
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	101,822	101,686
Ending balance impaired loans collectively evaluated for impairment	173,807	207,727
Total Impaired Loans, Recorded Investment	275,629	309,413
Ending balance all other loans collectively evaluated for impairment	17,318,217us-gaap_NotesReceivableNet	15,586,848us-gaap_NotesReceivableNet
Total loans	17,593,846	15,896,261
Commercial and Industrial Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	104,501	97,852
Provision for loan losses	14,767	12,930
Charge offs	(14,633)	(35,146)
Recoveries	11,390	28,865
Loans and Leases Receivable, Allowance, Ending Balance	116,025	104,501
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	13,615	7,994
Ending balance impaired loans collectively evaluated for impairment	2,852	3,923
Total Impaired Loans, Related Allowance	16,467	11,917
Ending balance all other loans collectively evaluated for impairment	99,558	92,584
Loans and Leases Receivable, Allowance, Total	116,025	104,501
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	45,118	29,343
Ending balance impaired loans collectively evaluated for impairment	38,437	40,893
Total Impaired Loans, Recorded Investment	83,555	70,236
Ending balance all other loans collectively evaluated for impairment	5,822,347	4,752,444
Total loans	5,905,902	4,822,680
Commercial Real Estate Owner Occupied Portfolio [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	19,476	27,389
Provision for loan losses	(1,296)	(1,778)
Charge offs	(3,476)	(6,474)
Recoveries	1,806	339
Loans and Leases Receivable, Allowance, Ending Balance	16,510	19,476
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	1,490	1,019
Ending balance impaired loans collectively evaluated for impairment	1,731	1,936
Total Impaired Loans, Related Allowance	3,221	2,955
Ending balance all other loans collectively evaluated for impairment	13,289	16,521
Loans and Leases Receivable, Allowance, Total	16,510	19,476
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	20,731	24,744
Ending balance impaired loans collectively evaluated for impairment	15,548	17,929
Total Impaired Loans, Recorded Investment	36,279	42,673
Ending balance all other loans collectively evaluated for impairment	971,658	1,072,042
Total loans	1,007,937	1,114,715
Finance Leases Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	1,607	3,024
Provision for loan losses	35	(1,429)
Charge offs	(39)	(206)
Recoveries	7	218
Loans and Leases Receivable, Allowance, Ending Balance	1,610	1,607
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	574	0
Ending balance impaired loans collectively evaluated for impairment	0	29
Total Impaired Loans, Related Allowance	574	29
Ending balance all other loans collectively evaluated for impairment	1,036	1,578
Loans and Leases Receivable, Allowance, Total	1,610	1,607
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	1,801	0
Ending balance impaired loans collectively evaluated for impairment	0	69
Total Impaired Loans, Recorded Investment	1,801	69
Ending balance all other loans collectively evaluated for impairment	49,728	55,414
Total loans	51,529	55,483
Commercial Real Estate Investor Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	58,156	63,181
Provision for loan losses	(17,290)	(2,140)
Charge offs	(4,529)	(9,846)
Recoveries	9,996	6,961
Loans and Leases Receivable, Allowance, Ending Balance	46,333	58,156
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	1,649	3,932
Ending balance impaired loans collectively evaluated for impairment	1,938	3,963
Total Impaired Loans, Related Allowance	3,587	7,895
Ending balance all other loans collectively evaluated for impairment	42,746	50,261
Loans and Leases Receivable, Allowance, Total	46,333	58,156
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	19,683	32,367
Ending balance impaired loans collectively evaluated for impairment	26,129	50,175
Total Impaired Loans, Recorded Investment	45,812	82,542
Ending balance all other loans collectively evaluated for impairment	3,010,673	2,856,914
Total loans	3,056,485	2,939,456
Real Estate Construction Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	23,418	20,741
Provision for loan losses	(1,277)	541
Charge offs	(1,958)	(3,375)
Recoveries	816	5,511
Loans and Leases Receivable, Allowance, Ending Balance	20,999	23,418
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	328	254
Ending balance impaired loans collectively evaluated for impairment	767	2,162
Total Impaired Loans, Related Allowance	1,095	2,416
Ending balance all other loans collectively evaluated for impairment	19,904	21,002
Loans and Leases Receivable, Allowance, Total	20,999	23,418
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	3,776	3,777
Ending balance impaired loans collectively evaluated for impairment	2,350	6,483
Total Impaired Loans, Recorded Investment	6,126	10,260
Ending balance all other loans collectively evaluated for impairment	1,002,830	885,988
Total loans	1,008,956	896,248
Home Equity Portfolio Segments [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	32,196	56,826
Provision for loan losses	7,087	(8,213)
Charge offs	(12,332)	(20,629)
Recoveries	3,408	4,212
Loans and Leases Receivable, Allowance, Ending Balance	30,359	32,196
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	11	123
Ending balance impaired loans collectively evaluated for impairment	13,004	13,866
Total Impaired Loans, Related Allowance	13,015	13,989
Ending balance all other loans collectively evaluated for impairment	17,344	18,207
Loans and Leases Receivable, Allowance, Total	30,359	32,196
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	962	929
Ending balance impaired loans collectively evaluated for impairment	30,845	33,871
Total Impaired Loans, Recorded Investment	31,807	34,800
Ending balance all other loans collectively evaluated for impairment	1,604,251	1,790,214
Total loans	1,636,058	1,825,014
Installment and Credit Cards Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	2,416	4,299
Provision for loan losses	6,279	(2,127)
Charge offs	(2,876)	(1,389)
Recoveries	616	1,633
Loans and Leases Receivable, Allowance, Ending Balance	6,435	2,416
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	0	0
Ending balance impaired loans collectively evaluated for impairment	308	487
Total Impaired Loans, Related Allowance	308	487
Ending balance all other loans collectively evaluated for impairment	6,127	1,929
Loans and Leases Receivable, Allowance, Total	6,435	2,416
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	0	0
Ending balance impaired loans collectively evaluated for impairment	1,587	1,360
Total Impaired Loans, Recorded Investment	1,587	1,360
Ending balance all other loans collectively evaluated for impairment	452,632	405,714
Total loans	454,219	407,074
Residential Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Loans and Leases Receivable, Allowance, Beginning Balance	26,545	24,097
Provision for loan losses	4,695	12,216
Charge offs	(4,253)	(10,996)
Recoveries	1,044	1,228
Loans and Leases Receivable, Allowance, Ending Balance	28,031	26,545
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	199	315
Ending balance impaired loans collectively evaluated for impairment	11,965	11,872
Total Impaired Loans, Related Allowance	12,164	12,187
Ending balance all other loans collectively evaluated for impairment	15,867	14,358
Loans and Leases Receivable, Allowance, Total	28,031	26,545
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	9,751	10,526
Ending balance impaired loans collectively evaluated for impairment	58,911	56,947
Total Impaired Loans, Recorded Investment	68,662	67,473
Ending balance all other loans collectively evaluated for impairment	4,404,098	3,768,118
Total loans	$ 4,472,760	$ 3,835,591

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A valuation allowance for financing receivables that are expected to be uncollectible.

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

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

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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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 and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

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

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