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, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 30,428,067	$ 29,699,208
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2020	233,209
2019	878,038
2018	942,328
2017	754,821
2016	454,888
Prior to 2016	1,169,386
Revolving Loans Amortized Cost Basis	46,312
Revolving Loans Converted to Term Loans	0
Total	4,478,982	4,377,111
Residential mortgage | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	233,209
2019	877,519
2018	942,127
2017	752,209
2016	450,980
Prior to 2016	1,160,244
Revolving Loans Amortized Cost Basis	46,312
Revolving Loans Converted to Term Loans	0
Total	4,462,600
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	129,345
2019	564,938
2018	381,361
2017	232,030
2016	90,668
Prior to 2016	114,298
Revolving Loans Amortized Cost Basis	1,263,906
Revolving Loans Converted to Term Loans	56,526
Total	2,833,072	$ 2,852,341
Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,017
2019	1,851
2018	3,621
2017	9,999
2016	2,492
Prior to 2016	21,740
Revolving Loans Amortized Cost Basis	384,505
Revolving Loans Converted to Term Loans	56,526
Total	481,751
Consumer loans | Home equity | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,017
2019	1,851
2018	3,621
2017	9,999
2016	2,492
Prior to 2016	21,668
Revolving Loans Amortized Cost Basis	384,208
Revolving Loans Converted to Term Loans	55,710
Total	480,566
Consumer loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
2020	120,779
2019	556,242
2018	363,325
2017	220,699
2016	86,794
Prior to 2016	88,895
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans	0
Total	1,436,734
Consumer loans | Automobile | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	120,779
2019	556,072
2018	363,005
2017	220,424
2016	86,715
Prior to 2016	88,776
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans	0
Total	1,435,771
Consumer loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,549
2019	6,845
2018	14,415
2017	1,332
2016	1,382
Prior to 2016	3,663
Revolving Loans Amortized Cost Basis	879,401
Revolving Loans Converted to Term Loans	0
Total	914,587
Consumer loans | Other consumer | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,549
2019	6,845
2018	14,415
2017	1,332
2016	1,382
Prior to 2016	3,663
Revolving Loans Amortized Cost Basis	878,495
Revolving Loans Converted to Term Loans	0
Total	913,681
90 Days or More Past Due Loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	519
2018	201
2017	2,612
2016	3,908
Prior to 2016	9,142
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans	0
Total	16,382
90 Days or More Past Due Loans | Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	72
Revolving Loans Amortized Cost Basis	297
Revolving Loans Converted to Term Loans	816
Total	1,185
90 Days or More Past Due Loans | Consumer loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	170
2018	320
2017	275
2016	79
Prior to 2016	119
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans	0
Total	963
90 Days or More Past Due Loans | Consumer loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	0
Revolving Loans Amortized Cost Basis	906
Revolving Loans Converted to Term Loans	0
Total	$ 906