Non Purchased Loans - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Restructured loans discontinued past due period	90 days
Allowance for loan losses attributable to restructured loans	$ 52,162,000	$ 49,026,000
Non-Purchased
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonperforming loans charged off past due period	90 days
Number of restructured loans | loan	2	1
Restructured loans discontinued past due period	90 days	90 days
Average recorded investment in impaired loans	$ 38,188,000	$ 27,080,000	$ 21,998,000
Interest income recognized on impaired loans			573,000
Modifications, recorded investment	4,679,000	5,325,000	5,588,000
Modifications, subsequent default, recorded investment		139,000	$ 184,000
Remaining availability under commitments to lend additional funds on restructured loans	0	42,000
Unfunded commitment	7,266,000	6,982,000
Non-Purchased | Nonaccruing Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Outstanding balance of restructured loans	164,000	41,000
Non-Purchased | Restructured Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Outstanding balance of restructured loans	3,058,000	3,128,000
Allowance for loan losses attributable to restructured loans	$ 125,000	$ 34,000