Commitments and Credit Risk - Textual (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Outstanding letters of credit	$ 36,929,000	$ 39,101,000
Standby Letters of Credit
Other Commitments [Line Items]
Deferred revenue	$ 0	0
Minimum
Other Commitments [Line Items]
Term of letter of credit	9 months
Maximum
Other Commitments [Line Items]
Term of letter of credit	15 years
Credit card commitments
Other Commitments [Line Items]
Outstanding commitments	$ 573,779,000	560,863,000
Other loan commitments
Other Commitments [Line Items]
Outstanding commitments	$ 3,384,471,000	$ 3,455,471,000