Commitments and Contingencies (Details) - USD ($)		3 Months Ended		9 Months Ended
	Jan. 01, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member			us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201602Member
Total allowance for loan losses	$ 281,402,000	$ 603,800,000	$ 265,013,000	$ 603,800,000	$ 265,013,000	$ 588,648,000		$ 281,402,000	$ 257,376,000	$ 250,555,000
Carrying amount included in other assets		214,615,000		214,615,000				146,612,000
Amount of future funding commitments included in carrying amount		124,866,000		124,866,000				78,266,000
Permanent and short-term construction loans and letter of credit commitments		52,686,000		52,686,000				2,124,000
Funded portion of permanent and short-term loans and letters of credit		5,194,000		5,194,000				3,196,000
Contractual amount net of risk participations		31,000,000		31,000,000				33,000,000
Guarantor obligations, advanced payment from merchant		20,600,000		20,600,000				21,400,000
Guarantor obligations, advanced payment from merchant, reserve							$ 2,700,000
Minimum
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		0		0
Maximum
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		5,000,000		5,000,000
Other assets held for sale
Loss Contingencies [Line Items]
Guarantor obligations, advanced payment from merchant		17,900,000		17,900,000
Guarantee obligations
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		14,091,035,000		14,091,035,000				13,117,770,000
Maximum potential exposure for sponsored transactions		20,230,000,000	$ 19,130,000,000	55,470,000,000	$ 55,720,000,000
Letters of credit
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		177,000,000		177,000,000				202,614,000
Commitments to fund commercial and industrial loans
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		7,990,189,000		7,990,189,000				7,018,152,000
Commitments to fund commercial real estate, construction, and land development loans
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		2,891,857,000		2,891,857,000				3,032,252,000
Commitments under home equity lines of credit
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		1,588,844,000		1,588,844,000				1,501,452,000
Unused credit card lines
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		984,636,000		984,636,000				877,929,000
Other loan commitments
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments		458,509,000		458,509,000				485,371,000
Unfunded Loan Commitment
Loss Contingencies [Line Items]
Current expected credit losses	$ 27,400,000
Total allowance for loan losses		$ 60,800,000		$ 60,800,000				$ 1,400,000