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	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 32,606,814	$ 32,217,112
90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	5,352	13,541
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	1,084,533	730,764
Year two, fiscal year before current fiscal year	661,652	781,246
Year three, two years before current fiscal year	622,035	688,973
Year four, three years before current fiscal year	471,948	586,114
Year five, four years before current fiscal year	408,997	384,867
More than five years before current fiscal year	1,022,747	946,981
Revolving Loans Amortized Cost Basis	60,510	64,798
Revolving Loans Converted to Term Loans	0	0
Total	4,332,422	4,183,743
Residential mortgage | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,002	3,170
Residential mortgage | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	1,084,533	730,764
Year two, fiscal year before current fiscal year	661,418	778,161
Year three, two years before current fiscal year	619,942	684,761
Year four, three years before current fiscal year	467,876	582,650
Year five, four years before current fiscal year	405,847	380,723
More than five years before current fiscal year	1,019,676	943,616
Revolving Loans Amortized Cost Basis	60,510	64,798
Revolving Loans Converted to Term Loans	0	0
Total	4,319,802	4,165,473
Residential mortgage | Non-Performing Loans | 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	234	3,085
Year three, two years before current fiscal year	2,093	4,212
Year four, three years before current fiscal year	4,072	3,464
Year five, four years before current fiscal year	3,150	4,144
More than five years before current fiscal year	3,071	3,365
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	12,620	18,270
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	629,016	446,991
Year two, fiscal year before current fiscal year	356,023	454,481
Year three, two years before current fiscal year	330,058	290,819
Year four, three years before current fiscal year	199,111	161,744
Year five, four years before current fiscal year	96,690	57,330
More than five years before current fiscal year	44,835	37,456
Revolving Loans Amortized Cost Basis	1,222,783	1,200,000
Revolving Loans Converted to Term Loans	43,966	52,017
Total	2,922,482	2,700,838
Consumer | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	11,096	8,580
Year two, fiscal year before current fiscal year	6,593	10,634
Year three, two years before current fiscal year	8,055	11,756
Year four, three years before current fiscal year	8,745	8,886
Year five, four years before current fiscal year	6,031	5,365
More than five years before current fiscal year	14,395	15,476
Revolving Loans Amortized Cost Basis	303,777	319,247
Revolving Loans Converted to Term Loans	43,966	51,609
Total	402,658	431,553
Consumer | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	611,402	426,140
Year two, fiscal year before current fiscal year	342,636	438,289
Year three, two years before current fiscal year	315,460	272,248
Year four, three years before current fiscal year	183,135	151,746
Year five, four years before current fiscal year	89,642	50,888
More than five years before current fiscal year	21,423	16,644
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	1,563,698	1,355,955
Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	6,518	12,271
Year two, fiscal year before current fiscal year	6,794	5,558
Year three, two years before current fiscal year	6,543	6,815
Year four, three years before current fiscal year	7,231	1,112
Year five, four years before current fiscal year	1,017	1,077
More than five years before current fiscal year	9,017	5,336
Revolving Loans Amortized Cost Basis	919,006	880,753
Revolving Loans Converted to Term Loans	0	408
Total	956,126	913,330
Consumer | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	325	271
Consumer | 90 Days or More Past Due Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Consumer | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total	233	245
Consumer | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	92	26
Consumer | Performing | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	11,096	8,580
Year two, fiscal year before current fiscal year	6,593	10,634
Year three, two years before current fiscal year	8,055	11,756
Year four, three years before current fiscal year	8,745	8,886
Year five, four years before current fiscal year	6,031	5,340
More than five years before current fiscal year	14,327	15,393
Revolving Loans Amortized Cost Basis	303,235	318,869
Revolving Loans Converted to Term Loans	43,502	50,879
Total	401,584	430,337
Consumer | Performing | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	611,329	426,121
Year two, fiscal year before current fiscal year	342,584	438,181
Year three, two years before current fiscal year	315,330	272,075
Year four, three years before current fiscal year	182,973	151,523
Year five, four years before current fiscal year	89,463	50,853
More than five years before current fiscal year	21,302	16,550
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	1,562,981	1,355,303
Consumer | Performing | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	6,518	12,271
Year two, fiscal year before current fiscal year	6,794	5,558
Year three, two years before current fiscal year	6,543	6,815
Year four, three years before current fiscal year	7,231	1,112
Year five, four years before current fiscal year	1,017	1,077
More than five years before current fiscal year	9,017	5,314
Revolving Loans Amortized Cost Basis	918,946	880,748
Revolving Loans Converted to Term Loans	0	0
Total	956,066	912,895
Consumer | Non-Performing 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	68	83
Revolving Loans Amortized Cost Basis	542	378
Revolving Loans Converted to Term Loans	464	730
Total	1,074	1,216
Consumer | Non-Performing Loans | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	73	19
Year two, fiscal year before current fiscal year	52	108
Year three, two years before current fiscal year	130	173
Year four, three years before current fiscal year	162	223
Year five, four years before current fiscal year	179	35
More than five years before current fiscal year	121	94
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans	0	0
Total	717	652
Consumer | Non-Performing 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	60	5
Revolving Loans Converted to Term Loans	0	408
Total	$ 60	$ 435