Loans Held for Sale, Loans and Allowance for Credit Losses - Summary of Credit Quality Indicator And by Origination Year (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Financing Receivable Recorded Investment [Line Items]
2020	$ 365,050
2019	1,692,792
2018	2,721,950
2017	1,826,052
2016	1,080,100
2015 and Prior	1,921,595
Revolving Loans	3,784,652
Total	13,392,191
Commercial Portfolio Segment
Financing Receivable Recorded Investment [Line Items]
2020	175,477
2019	812,411
2018	1,305,789
2017	774,788
2016	472,159
2015 and Prior	821,024
Revolving Loans	3,387,662
Total	7,749,310
Commercial Portfolio Segment \| Pass
Financing Receivable Recorded Investment [Line Items]
2020	174,633
2019	796,988
2018	1,155,772
2017	713,223
2016	397,273
2015 and Prior	738,601
Revolving Loans	3,179,764
Total	7,156,254
Commercial Portfolio Segment \| Special mention
Financing Receivable Recorded Investment [Line Items]
2020	261
2019	7,690
2018	69,934
2017	34,365
2016	39,415
2015 and Prior	16,712
Revolving Loans	86,730
Total	255,107
Commercial Portfolio Segment \| Substandard
Financing Receivable Recorded Investment [Line Items]
2020	583
2019	5,949
2018	76,623
2017	26,435
2016	35,471
2015 and Prior	58,585
Revolving Loans	114,862
Total	318,508
Commercial Portfolio Segment \| Doubtful
Financing Receivable Recorded Investment [Line Items]
2019	1,784
2018	3,460
2017	765
2015 and Prior	7,126
Revolving Loans	6,306
Total	19,441
Commercial Real Estate
Financing Receivable Recorded Investment [Line Items]
2020	110,565
2019	406,781
2018	762,387
2017	694,378
2016	282,714
2015 and Prior	581,749
Revolving Loans	142,186
Total	2,980,760
Commercial Real Estate \| Pass
Financing Receivable Recorded Investment [Line Items]
2020	109,070
2019	406,225
2018	737,092
2017	692,826
2016	274,966
2015 and Prior	562,834
Revolving Loans	141,895
Total	2,924,908
Commercial Real Estate \| Special mention
Financing Receivable Recorded Investment [Line Items]
2020	1,495
2019	346
2018	25,125
2017	945
2016	293
2015 and Prior	3,221
Revolving Loans	279
Total	31,704
Commercial Real Estate \| Substandard
Financing Receivable Recorded Investment [Line Items]
2019	210
2018	170
2017	607
2016	7,455
2015 and Prior	15,694
Revolving Loans	12
Total	24,148
Consumer
Financing Receivable Recorded Investment [Line Items]
2020	79,008
2019	473,600
2018	653,774
2017	356,886
2016	325,227
2015 and Prior	518,822
Revolving Loans	254,804
Total	2,662,121
Consumer \| Current
Financing Receivable Recorded Investment [Line Items]
2020	79,008
2019	471,638
2018	646,405
2017	356,462
2016	320,817
2015 and Prior	504,905
Revolving Loans	252,225
Total	2,631,460
Consumer \| 30-59 days past due
Financing Receivable Recorded Investment [Line Items]
2019	1,506
2018	4,076
2017	340
2016	1,795
2015 and Prior	7,443
Revolving Loans	2,358
Total	17,518
Consumer \| 60-89 days past due
Financing Receivable Recorded Investment [Line Items]
2019	309
2018	1,134
2017	76
2016	1,075
2015 and Prior	1,494
Revolving Loans	221
Total	4,309
Consumer \| 90+ days past due
Financing Receivable Recorded Investment [Line Items]
2019	147
2018	2,159
2017	8
2016	1,540
2015 and Prior	4,980
Total	$ 8,834

Amount, after fee received for commitment to originate or purchase, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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