Loans, Changes in the Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	$ 266,302	$ 268,315	$ 297,409
Provision for loan losses	38,000	13,000	10,000
Charge offs	(52,280)	(44,096)	(88,061)
Recoveries	22,242	29,083	48,967
Balance at end of year	274,264	266,302	268,315
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	7,963	17,866
Ending balance impaired loans collectively evaluated for impairment	25,706	32,565
Total Impaired Loans, Related Allowance	33,669	50,431
Ending balance all other loans collectively evaluated for impairment	240,595	215,871
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	111,487	101,822
Ending balance impaired loans collectively evaluated for impairment	154,134	173,807
Total Impaired Loans, Recorded Investment	265,621	275,629
Ending balance all other loans collectively evaluated for impairment	18,448,722	17,318,217
Total loans	18,714,343	17,593,846
Commercial and Industrial Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	116,025	104,501
Provision for loan losses	30,861	14,767
Charge offs	(27,687)	(14,633)
Recoveries	9,795	11,390
Balance at end of year	128,994	116,025	104,501
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	7,522	13,615
Ending balance impaired loans collectively evaluated for impairment	640	2,852
Total Impaired Loans, Related Allowance	8,162	16,467
Ending balance all other loans collectively evaluated for impairment	120,832	99,558
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	89,935	45,118
Ending balance impaired loans collectively evaluated for impairment	31,299	38,437
Total Impaired Loans, Recorded Investment	121,234	83,555
Ending balance all other loans collectively evaluated for impairment	6,026,206	5,822,347
Total loans	6,147,440	5,905,902
Commercial Real Estate Owner Occupied Portfolio [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	16,510	19,476
Provision for loan losses	3,894	(1,296)
Charge offs	(2,645)	(3,476)
Recoveries	921	1,806
Balance at end of year	18,680	16,510	19,476
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	0	1,490
Ending balance impaired loans collectively evaluated for impairment	448	1,731
Total Impaired Loans, Related Allowance	448	3,221
Ending balance all other loans collectively evaluated for impairment	18,232	13,289
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	6,221	20,731
Ending balance impaired loans collectively evaluated for impairment	9,705	15,548
Total Impaired Loans, Recorded Investment	15,926	36,279
Ending balance all other loans collectively evaluated for impairment	902,286	971,658
Total loans	918,212	1,007,937
Finance Leases Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	1,610	1,607
Provision for loan losses	(671)	35
Charge offs	0	(39)
Recoveries	26	7
Balance at end of year	965	1,610	1,607
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	0	574
Ending balance impaired loans collectively evaluated for impairment	0	0
Total Impaired Loans, Related Allowance	0	574
Ending balance all other loans collectively evaluated for impairment	965	1,036
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	1,634	1,801
Ending balance impaired loans collectively evaluated for impairment	0	0
Total Impaired Loans, Recorded Investment	1,634	1,801
Ending balance all other loans collectively evaluated for impairment	41,609	49,728
Total loans	43,243	51,529
Commercial Real Estate Investor Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	46,333	58,156
Provision for loan losses	(2,827)	(17,290)
Charge offs	(4,645)	(4,529)
Recoveries	4,157	9,996
Balance at end of year	43,018	46,333	58,156
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	229	1,649
Ending balance impaired loans collectively evaluated for impairment	1,602	1,938
Total Impaired Loans, Related Allowance	1,831	3,587
Ending balance all other loans collectively evaluated for impairment	41,187	42,746
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	5,460	19,683
Ending balance impaired loans collectively evaluated for impairment	25,098	26,129
Total Impaired Loans, Recorded Investment	30,558	45,812
Ending balance all other loans collectively evaluated for impairment	3,203,708	3,010,673
Total loans	3,234,266	3,056,485
Real Estate Construction Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	20,999	23,418
Provision for loan losses	2,749	(1,277)
Charge offs	(750)	(1,958)
Recoveries	2,268	816
Balance at end of year	25,266	20,999	23,418
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	0	328
Ending balance impaired loans collectively evaluated for impairment	453	767
Total Impaired Loans, Related Allowance	453	1,095
Ending balance all other loans collectively evaluated for impairment	24,813	19,904
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	0	3,776
Ending balance impaired loans collectively evaluated for impairment	1,450	2,350
Total Impaired Loans, Recorded Investment	1,450	6,126
Ending balance all other loans collectively evaluated for impairment	1,160,695	1,002,830
Total loans	1,162,145	1,008,956
Home Equity Portfolio Segments [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	26,464	27,932
Provision for loan losses	906	6,278
Charge offs	(7,048)	(10,946)
Recoveries	3,233	3,200
Balance at end of year	23,555	26,464	27,932
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	46	11
Ending balance impaired loans collectively evaluated for impairment	10,072	11,371
Total Impaired Loans, Related Allowance	10,118	11,382
Ending balance all other loans collectively evaluated for impairment	13,437	15,082
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	1,281	962
Ending balance impaired loans collectively evaluated for impairment	21,032	23,698
Total Impaired Loans, Recorded Investment	22,313	24,660
Ending balance all other loans collectively evaluated for impairment	983,489	1,027,267
Total loans	1,005,802	1,051,927
Installment and Credit Cards Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	6,435	2,416
Provision for loan losses	2,194	6,279
Charge offs	(3,869)	(2,876)
Recoveries	765	616
Balance at end of year	5,525	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	195	308
Total Impaired Loans, Related Allowance	195	308
Ending balance all other loans collectively evaluated for impairment	5,330	6,127
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	0	0
Ending balance impaired loans collectively evaluated for impairment	1,154	1,587
Total Impaired Loans, Recorded Investment	1,154	1,587
Ending balance all other loans collectively evaluated for impairment	418,814	452,632
Total loans	419,968	454,219
Residential Portfolio Segment [Member]
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	31,926	30,809
Provision for loan losses	894	5,504
Charge offs	(5,636)	(5,639)
Recoveries	1,077	1,252
Balance at end of year	28,261	31,926	$ 30,809
Allowance for loan losses:
Ending balance impaired loans individually evaluated for impairment	166	199
Ending balance impaired loans collectively evaluated for impairment	12,296	13,598
Total Impaired Loans, Related Allowance	12,462	13,797
Ending balance all other loans collectively evaluated for impairment	15,799	18,129
Loans [Abstract]
Ending balance impaired loans individually evaluated for impairment	6,956	9,751
Ending balance impaired loans collectively evaluated for impairment	64,396	66,058
Total Impaired Loans, Recorded Investment	71,352	75,809
Ending balance all other loans collectively evaluated for impairment	5,711,915	4,981,082
Total loans	$ 5,783,267	$ 5,056,891