Commitments and Contingencies (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Total allowance for loan losses	$ 493,452,000	$ 257,036,000		$ 281,402,000	$ 250,555,000
Carrying amount included in other assets	166,460,000			146,612,000
Amount of future funding commitments included in carrying amount	93,749,000			78,266,000
Short-term construction loans and letter of credit commitments	792,000			2,124,000
Funded portion of short-term loans and letters of credit	4,516,000			3,196,000
Contractual amount net of risk participations	32,000,000			33,000,000
Guarantor obligations, advanced payment from merchant	21,200,000			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
Maximum
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	5,000,000
Other assets held for sale
Loss Contingencies [Line Items]
Guarantor obligations, advanced payment from merchant	18,500,000
Guarantee obligations
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	13,021,539,000			13,117,770,000
Maximum potential exposure for sponsored transactions	18,370,000,000	$ 17,710,000,000
Letters of credit*
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	182,629,000			202,614,000
Commitments to fund commercial and industrial loans
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	6,994,969,000			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	2,925,791,000			3,032,252,000
Commitments under home equity lines of credit
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	1,508,176,000			1,501,452,000
Unused credit card lines
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	940,016,000			877,929,000
Other loan commitments
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	469,958,000			485,371,000
ASU 2016-13
Loss Contingencies [Line Items]
Total allowance for loan losses			$ 281,402,000
ASU 2016-13 | Unfunded Loan Commitment
Loss Contingencies [Line Items]
Current Expected Credit Losses			$ 27,400,000
Total allowance for loan losses	$ 38,400,000			$ 1,400,000