Loans, Impaired Loans Recorded Investment, Unpaid Principal Balance, Related Allowance, Average Recorded Investment, and Interest Income Recognized (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	$ 233,078	$ 247,575
Unpaid Principal Balance	267,094	275,814
Related Allowance	34,094	25,846
Average Recorded Investment	234,164	236,860
Interest Income Recognized	$ 1,090	$ 8,051
Net Recorded Investment of the Impaired Loans	74.00%	80.00%
Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	$ 162,022	$ 175,681
Unpaid Principal Balance	170,162	181,002
Related Allowance	34,094	25,846
Average Recorded Investment	168,908	140,098
Interest Income Recognized	1,398	7,254
Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	71,056	71,894
Unpaid Principal Balance	96,932	94,812
Related Allowance	0	0
Average Recorded Investment	65,256	96,762
Interest Income Recognized	(308)	797
Commercial and industrial
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	128,841	142,244
Unpaid Principal Balance	157,811	166,418
Related Allowance	18,778	10,838
Average Recorded Investment	133,027	147,769
Interest Income Recognized	36	3,121
Commercial and industrial | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	76,452	81,649
Unpaid Principal Balance	81,091	83,579
Related Allowance	18,778	10,838
Average Recorded Investment	77,130	58,494
Interest Income Recognized	312	2,629
Commercial and industrial | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	52,389	60,595
Unpaid Principal Balance	76,720	82,839
Related Allowance	0	0
Average Recorded Investment	55,897	89,275
Interest Income Recognized	(348)	492
Commercial real estate — owner occupied
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	22,489	26,234
Unpaid Principal Balance	23,893	26,766
Related Allowance	2,043	2,973
Average Recorded Investment	25,381	14,072
Interest Income Recognized	47	772
Commercial real estate — owner occupied | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	16,264	23,796
Unpaid Principal Balance	16,617	23,937
Related Allowance	2,043	2,973
Average Recorded Investment	22,978	12,124
Interest Income Recognized	47	736
Commercial real estate — owner occupied | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	6,225	2,438
Unpaid Principal Balance	7,276	2,829
Related Allowance	0	0
Average Recorded Investment	2,403	1,948
Interest Income Recognized	0	36
Commercial and business lending
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	151,330	168,478
Unpaid Principal Balance	181,704	193,184
Related Allowance	20,821	13,811
Average Recorded Investment	158,408	161,841
Interest Income Recognized	11	3,893
Commercial and business lending | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	92,716	105,445
Unpaid Principal Balance	97,708	107,516
Related Allowance	20,821	13,811
Average Recorded Investment	100,108	70,618
Interest Income Recognized	359	3,365
Commercial and business lending | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	58,614	63,033
Unpaid Principal Balance	83,996	85,668
Related Allowance	0	0
Average Recorded Investment	58,300	91,223
Interest Income Recognized	(348)	528
Commercial real estate — investor
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	20,387	19,118
Unpaid Principal Balance	20,472	19,157
Related Allowance	2,721	1,597
Average Recorded Investment	16,559	16,924
Interest Income Recognized	464	1,739
Commercial real estate — investor | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	18,582	17,823
Unpaid Principal Balance	18,619	17,862
Related Allowance	2,721	1,597
Average Recorded Investment	16,559	16,924
Interest Income Recognized	464	1,694
Commercial real estate — investor | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,805	1,295
Unpaid Principal Balance	1,853	1,295
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	45
Real estate construction
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	458	467
Unpaid Principal Balance	532	578
Related Allowance	82	86
Average Recorded Investment	461	484
Interest Income Recognized	7	29
Real estate construction | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	458	467
Unpaid Principal Balance	532	578
Related Allowance	82	86
Average Recorded Investment	461	484
Interest Income Recognized	7	29
Real estate construction | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Commercial real estate lending
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	20,845	19,585
Unpaid Principal Balance	21,004	19,735
Related Allowance	2,803	1,683
Average Recorded Investment	17,020	17,408
Interest Income Recognized	471	1,768
Commercial real estate lending | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	19,040	18,290
Unpaid Principal Balance	19,151	18,440
Related Allowance	2,803	1,683
Average Recorded Investment	17,020	17,408
Interest Income Recognized	471	1,723
Commercial real estate lending | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,805	1,295
Unpaid Principal Balance	1,853	1,295
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	45
Total commercial
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	172,175	188,063
Unpaid Principal Balance	202,708	212,919
Related Allowance	23,624	15,494
Average Recorded Investment	175,428	179,249
Interest Income Recognized	482	5,661
Total commercial | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	111,756	123,735
Unpaid Principal Balance	116,859	125,956
Related Allowance	23,624	15,494
Average Recorded Investment	117,128	88,026
Interest Income Recognized	830	5,088
Total commercial | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	60,419	64,328
Unpaid Principal Balance	85,849	86,963
Related Allowance	0	0
Average Recorded Investment	58,300	91,223
Interest Income Recognized	(348)	573
Residential mortgage
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	48,863	47,486
Unpaid Principal Balance	51,722	50,126
Related Allowance	6,635	6,512
Average Recorded Investment	46,792	45,410
Interest Income Recognized	470	1,831
Residential mortgage | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	38,438	40,561
Unpaid Principal Balance	40,851	42,922
Related Allowance	6,635	6,512
Average Recorded Investment	40,475	40,411
Interest Income Recognized	431	1,614
Residential mortgage | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,425	6,925
Unpaid Principal Balance	10,871	7,204
Related Allowance	0	0
Average Recorded Investment	6,317	4,999
Interest Income Recognized	39	217
Home equity
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,974	10,891
Unpaid Principal Balance	11,595	11,631
Related Allowance	3,719	3,718
Average Recorded Investment	10,877	11,061
Interest Income Recognized	137	556
Home equity | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,762	10,250
Unpaid Principal Balance	11,383	10,986
Related Allowance	3,719	3,718
Average Recorded Investment	10,238	10,521
Interest Income Recognized	136	549
Home equity | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	212	641
Unpaid Principal Balance	212	645
Related Allowance	0	0
Average Recorded Investment	639	540
Interest Income Recognized	1	7
Other consumer
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,066	1,135
Unpaid Principal Balance	1,069	1,138
Related Allowance	116	122
Average Recorded Investment	1,067	1,140
Interest Income Recognized	1	3
Other consumer | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,066	1,135
Unpaid Principal Balance	1,069	1,138
Related Allowance	116	122
Average Recorded Investment	1,067	1,140
Interest Income Recognized	1	3
Other consumer | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Total consumer
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	60,903	59,512
Unpaid Principal Balance	64,386	62,895
Related Allowance	10,470	10,352
Average Recorded Investment	58,736	57,611
Interest Income Recognized	608	2,390
Total consumer | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	50,266	51,946
Unpaid Principal Balance	53,303	55,046
Related Allowance	10,470	10,352
Average Recorded Investment	51,780	52,072
Interest Income Recognized	568	2,166
Total consumer | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,637	7,566
Unpaid Principal Balance	11,083	7,849
Related Allowance	0	0
Average Recorded Investment	6,956	5,539
Interest Income Recognized	$ 40	$ 224