Loans - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable
Non-covered loans net of unearned premiums and deferred loan fees	$ 19,600,000		$ 19,600,000		$ 21,500,000
Outstanding balances for PCI loans	4,000,000,000.0		4,000,000,000.0		4,400,000,000
Transfer of loans to loans held for sale			216,211,000	$ 263,324,000
Sales of loans			0	0
Impaired loans	250,000		$ 250,000
Number of consecutive months for performing restructured loans to be put on accrual status			6 months
TDRs not reported as non-accrual loans	74,400,000		$ 74,400,000		77,200,000
Non-performing TDRs	67,800,000		67,800,000		55,000,000.0
Specific reserves for loan losses			11,700,000	5,300,000
Loan charge-offs related to loans modified as TDRs	$ 1,100,000	$ 0	$ 2,000,000.0	$ 0
Days past due to place on payment default	90 days	90 days	90 days	90 days
Other real estate owned	$ 7,200,000		$ 7,200,000		9,500,000
Residential real estate properties
Accounts, Notes, Loans and Financing Receivable
Other real estate owned	1,200,000		1,200,000		852,000
In formal foreclosure proceedings
Accounts, Notes, Loans and Financing Receivable
Residential mortgage and consumer loans secured by residential real estate properties	$ 1,700,000		1,700,000		$ 1,800,000
Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Transfer of loans to loans held for sale			$ 216,200,000	$ 263,300,000