Loans and Allowances for Credit Losses, Activity in Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL	$ 315,311		$ 236,568
Beginning balance - Incurred Loss Model		$ 205,340	210,759	$ 207,457
Provision for loan losses - CECL	134,365		230,329
Provision for loan losses - incurred		4,918		12,887
Loans charged off	(15,570)	(13,227)	(34,487)	(25,002)
Recoveries of loans previously charged off	1,491	5,503	3,187	7,192
Ending balance - CECL	435,597		435,597
Ending balance - Incurred Loss Model	435,597	202,534	435,597	202,534
Provision Details [Abstract]
Change in provision due to changes in reasonable and supportable forecasts, primarily due to COVID-19 pandemic	54,600
Other changes to provision	84,200
Provision change due to changes in impairment, risk grading, and other portfolio changes	14,400
Provision change due to risk grading	55,700
Provision changes due to net charge-offs	14,100
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL	28,514		25,137
Provision for off-balance sheet credit risk	4,405		7,782
Ending balance - CECL	32,919		32,919
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance - Incurred Loss Model		1,821		1,790
Provision for off-balance sheet credit losses		82		113
Ending balance - Incurred Loss Model		1,903		1,903
Total provision for credit losses	135,321	5,000	229,092	13,000
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment					$ 23,900,494	$ 21,570,036
Individually measured for impairment, recorded investment					255,396	180,951
Total					24,155,890	21,750,987
Related allowance [Abstract]
Collectively measured for impairment, related allowance					411,274	176,150
Individually measured for impairment, related allowance					24,323	17,414
Total	435,597	202,534	210,759	202,534	435,597	210,759
Commercial [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL	213,438		151,868
Beginning balance - Incurred Loss Model		103,577	118,187	102,226
Provision for loan losses - CECL	111,153		188,876
Provision for loan losses - incurred		13,771		24,879
Loans charged off	(14,487)	(11,385)	(31,102)	(21,853)
Recoveries of loans previously charged off	318	434	780	1,145
Ending balance - CECL	310,422		310,422
Ending balance - Incurred Loss Model	310,422	106,397	310,422	106,397
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL	14,040		11,578
Provision for off-balance sheet credit risk	542		3,004
Ending balance - CECL	14,582		14,582
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance - Incurred Loss Model		1,725		1,655
Provision for off-balance sheet credit losses		17		87
Ending balance - Incurred Loss Model		1,742		1,742
Total provision for credit losses		13,788		24,966
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment					13,956,511	13,916,234
Individually measured for impairment, recorded investment					201,999	115,416
Total					14,158,510	14,031,650
Related allowance [Abstract]
Collectively measured for impairment, related allowance					286,639	100,773
Individually measured for impairment, related allowance					23,783	17,414
Total	310,422	106,397	118,187	106,397	310,422	118,187
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL	51,461		47,185
Beginning balance - Incurred Loss Model		58,134	51,805	60,026
Provision for loan losses - CECL	17,221		22,336
Provision for loan losses - incurred		(8,173)		(10,177)
Loans charged off	(1)	(118)	(887)	(118)
Recoveries of loans previously charged off	75	4,345	122	4,457
Ending balance - CECL	68,756		68,756
Ending balance - Incurred Loss Model	68,756	54,188	68,756	54,188
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL	12,575		11,767
Provision for off-balance sheet credit risk	3,844		4,652
Ending balance - CECL	16,419		16,419
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance - Incurred Loss Model		48		52
Provision for off-balance sheet credit losses		68		64
Ending balance - Incurred Loss Model		116		116
Total provision for credit losses		(8,105)		(10,113)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment					4,540,188	4,406,157
Individually measured for impairment, recorded investment					13,956	27,626
Total					4,554,144	4,433,783
Related allowance [Abstract]
Collectively measured for impairment, related allowance					68,216	51,805
Individually measured for impairment, related allowance					540	0
Total	68,756	54,188	51,805	54,188	68,756	51,805
Paycheck Protection Program
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL	0		0
Provision for loan losses - CECL	0		0
Loans charged off	0		0
Recoveries of loans previously charged off	0		0
Ending balance - CECL	0		0
Ending balance - Incurred Loss Model	0		0
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL	0		0
Provision for off-balance sheet credit risk	0		0
Ending balance - CECL	0		0
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment					2,081,428
Individually measured for impairment, recorded investment					0
Total					2,081,428
Related allowance [Abstract]
Collectively measured for impairment, related allowance					0
Individually measured for impairment, related allowance					0
Total	0		0		0
Loans to individuals [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL	50,412		37,515
Provision for loan losses - CECL	5,991		19,117
Loans charged off	(1,082)		(2,498)
Recoveries of loans previously charged off	1,098		2,285
Ending balance - CECL	56,419		56,419
Ending balance - Incurred Loss Model	56,419		56,419
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL	1,899		1,792
Provision for off-balance sheet credit risk	19		126
Ending balance - CECL	1,918		1,918
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment					3,322,367
Individually measured for impairment, recorded investment					39,441
Total					3,361,808	2,084,172
Related allowance [Abstract]
Collectively measured for impairment, related allowance					56,419
Individually measured for impairment, related allowance					0
Total	56,419		56,419		56,419
Loans to individuals [Member] | Residential mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - Incurred Loss Model		15,668	14,400	17,964
Provision for loan losses - incurred		1		(2,407)
Loans charged off		(94)		(136)
Recoveries of loans previously charged off		149		303
Ending balance - Incurred Loss Model		15,724		15,724
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance - Incurred Loss Model		47		52
Provision for off-balance sheet credit losses		(3)		(8)
Ending balance - Incurred Loss Model		44		44
Total provision for credit losses		(2)		(2,415)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment						2,046,550
Individually measured for impairment, recorded investment						37,622
Total					1,813,442	2,084,172
Related allowance [Abstract]
Collectively measured for impairment, related allowance						14,400
Individually measured for impairment, related allowance						0
Total		15,724	14,400	17,964		14,400
Loans to individuals [Member] | Personal [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - Incurred Loss Model		8,783	9,172	9,473
Provision for loan losses - incurred		1,660		1,523
Loans charged off		(1,630)		(2,895)
Recoveries of loans previously charged off		575		1,287
Ending balance - Incurred Loss Model		9,388		9,388
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance - Incurred Loss Model		1		31
Provision for off-balance sheet credit losses		0		(30)
Ending balance - Incurred Loss Model		1		1
Total provision for credit losses		1,660		1,493
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment						1,201,095
Individually measured for impairment, recorded investment						287
Total					$ 1,226,097	1,201,382
Related allowance [Abstract]
Collectively measured for impairment, related allowance						9,172
Individually measured for impairment, related allowance						0
Total		9,388	9,172	9,473		9,172
Specific Allowance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - Incurred Loss Model			193,564
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment						21,570,036
Individually measured for impairment, recorded investment						180,951
Total						21,750,987
Related allowance [Abstract]
Collectively measured for impairment, related allowance						176,150
Individually measured for impairment, related allowance						17,414
Total			193,564			193,564
Nonspecific Allowance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL	0		0
Beginning balance - Incurred Loss Model		19,178	17,195	17,768
Provision for loan losses - CECL	0		0
Provision for loan losses - incurred		(2,341)		(931)
Loans charged off	0	0	0	0
Recoveries of loans previously charged off	0	0	0	0
Ending balance - CECL	0		0
Ending balance - Incurred Loss Model		16,837		16,837
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL	0		0
Provision for off-balance sheet credit risk	0		0
Ending balance - CECL	$ 0		0
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance - Incurred Loss Model		0		0
Provision for off-balance sheet credit losses		0		0
Ending balance - Incurred Loss Model		0		0
Total provision for credit losses		(2,341)		(931)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment						0
Individually measured for impairment, recorded investment						0
Total						0
Related allowance [Abstract]
Collectively measured for impairment, related allowance						0
Individually measured for impairment, related allowance						0
Total		$ 16,837	17,195	$ 17,768		$ 17,195
Previously Reported [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			210,759
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			1,585
Previously Reported [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			118,187
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			1,434
Previously Reported [Member] | Commercial real estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			51,805
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			107
Previously Reported [Member] | Paycheck Protection Program
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			0
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			0
Previously Reported [Member] | Loans to individuals [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			23,572
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			44
Previously Reported [Member] | Nonspecific Allowance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			17,195
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			0
Restatement Adjustment [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			25,809
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			23,552
Restatement Adjustment [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			33,681
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			10,144
Restatement Adjustment [Member] | Commercial real estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			(4,620)
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			11,660
Restatement Adjustment [Member] | Paycheck Protection Program
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			0
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			0
Restatement Adjustment [Member] | Loans to individuals [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			13,943
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			1,748
Restatement Adjustment [Member] | Nonspecific Allowance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance - CECL			(17,195)
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance - CECL			$ 0