Loans and Allowance for Credit Losses for Loans - Amortized Cost In Those Loan Classes Based on Payment Activity by Origination Year (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 32,686,416	$ 32,217,112
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	219,558	730,764
Year two, fiscal year before current fiscal year	734,505	781,246
Year three, two years before current fiscal year	728,699	688,973
Year four, three years before current fiscal year	597,333	586,114
Year five, four years before current fiscal year	511,822	384,867
More than five years before current fiscal year	1,224,534	946,981
Revolving Loans Amortized Cost Basis	44,041	64,798
Revolving Loans Converted to Term Loans	0	0
Total	4,060,492	4,183,743
Residential mortgage | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0	0
Year two, fiscal year before current fiscal year	2,478	3,085
Year three, two years before current fiscal year	2,814	4,212
Year four, three years before current fiscal year	2,489	3,464
Year five, four years before current fiscal year	3,645	4,144
More than five years before current fiscal year	11,754	3,365
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	23,180	18,270
Residential mortgage | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	219,558	730,764
Year two, fiscal year before current fiscal year	732,027	778,161
Year three, two years before current fiscal year	725,885	684,761
Year four, three years before current fiscal year	594,844	582,650
Year five, four years before current fiscal year	508,177	380,723
More than five years before current fiscal year	1,212,780	943,616
Revolving Loans Amortized Cost Basis	44,041	64,798
Revolving Loans Converted to Term Loans	0	0
Total	4,037,312	4,165,473
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	223,686	446,991
Year two, fiscal year before current fiscal year	427,098	454,481
Year three, two years before current fiscal year	412,842	290,819
Year four, three years before current fiscal year	258,263	161,744
Year five, four years before current fiscal year	137,794	57,330
More than five years before current fiscal year	73,527	37,456
Revolving Loans Amortized Cost Basis	1,184,530	1,200,000
Revolving Loans Converted to Term Loans	49,582	52,017
Total	2,767,322	2,700,838
Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	1,890	8,580
Year two, fiscal year before current fiscal year	8,179	10,634
Year three, two years before current fiscal year	9,917	11,756
Year four, three years before current fiscal year	10,612	8,886
Year five, four years before current fiscal year	7,550	5,365
More than five years before current fiscal year	17,277	15,476
Revolving Loans Amortized Cost Basis	304,977	319,247
Revolving Loans Converted to Term Loans	49,174	51,609
Total	409,576	431,553
Consumer loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	214,566	426,140
Year two, fiscal year before current fiscal year	411,863	438,289
Year three, two years before current fiscal year	397,550	272,248
Year four, three years before current fiscal year	241,099	151,746
Year five, four years before current fiscal year	129,168	50,888
More than five years before current fiscal year	50,637	16,644
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	1,444,883	1,355,955
Consumer loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	7,230	12,271
Year two, fiscal year before current fiscal year	7,056	5,558
Year three, two years before current fiscal year	5,375	6,815
Year four, three years before current fiscal year	6,552	1,112
Year five, four years before current fiscal year	1,076	1,077
More than five years before current fiscal year	5,613	5,336
Revolving Loans Amortized Cost Basis	879,553	880,753
Revolving Loans Converted to Term Loans	408	408
Total	912,863	913,330
Consumer loans | 90 Days or More Past Due Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0	0
Year two, fiscal year before current fiscal year	0	0
Year three, two years before current fiscal year	0	0
Year four, three years before current fiscal year	0	0
Year five, four years before current fiscal year	0	25
More than five years before current fiscal year	96	83
Revolving Loans Amortized Cost Basis	573	378
Revolving Loans Converted to Term Loans	810	730
Total	1,479	1,216
Consumer loans | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0	19
Year two, fiscal year before current fiscal year	42	108
Year three, two years before current fiscal year	141	173
Year four, three years before current fiscal year	247	223
Year five, four years before current fiscal year	208	35
More than five years before current fiscal year	131	94
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	769	652
Consumer loans | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0	0
Year two, fiscal year before current fiscal year	0	0
Year three, two years before current fiscal year	0	0
Year four, three years before current fiscal year	0	0
Year five, four years before current fiscal year	0	0
More than five years before current fiscal year	0	22
Revolving Loans Amortized Cost Basis	1	5
Revolving Loans Converted to Term Loans	408	408
Total	409	435
Consumer loans | Performing Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	1,890	8,580
Year two, fiscal year before current fiscal year	8,179	10,634
Year three, two years before current fiscal year	9,917	11,756
Year four, three years before current fiscal year	10,612	8,886
Year five, four years before current fiscal year	7,550	5,340
More than five years before current fiscal year	17,181	15,393
Revolving Loans Amortized Cost Basis	304,404	318,869
Revolving Loans Converted to Term Loans	48,364	50,879
Total	408,097	430,337
Consumer loans | Performing Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	214,566	426,121
Year two, fiscal year before current fiscal year	411,821	438,181
Year three, two years before current fiscal year	397,409	272,075
Year four, three years before current fiscal year	240,852	151,523
Year five, four years before current fiscal year	128,960	50,853
More than five years before current fiscal year	50,506	16,550
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	1,444,114	1,355,303
Consumer loans | Performing Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	7,230	12,271
Year two, fiscal year before current fiscal year	7,056	5,558
Year three, two years before current fiscal year	5,375	6,815
Year four, three years before current fiscal year	6,552	1,112
Year five, four years before current fiscal year	1,076	1,077
More than five years before current fiscal year	5,613	5,314
Revolving Loans Amortized Cost Basis	879,552	880,748
Revolving Loans Converted to Term Loans	0	0
Total	$ 912,454	$ 912,895