Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Loan commitments to extend credit	$ 7,528,248,000	$ 6,234,061,000
Standby letters of credit	364,210,000	320,063,000
Commitment To Contribute Capital	101,991,000	62,553,000
Purchase Commitment, Remaining Minimum Amount Committed	50,000	2,541,000
Unused Commitments to Extend Credit	$ 7,994,499,000	$ 6,619,218,000