Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Loan commitments to extend credit	$ 7,601,390,000	$ 8,183,158,000
Standby letters of credit	337,336,000	355,503,000
Commitment To Contribute Capital	55,500,000	129,200,000
Commitment To Contribute Capital To Low Income Housing Project Partnerships	0	88,515,000
Purchase Commitment, Remaining Minimum Amount Committed	0	50,000
Unused Commitments to Extend Credit	$ 7,994,225,000	$ 8,667,924,000