Fair Value - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Average capitalization rate	7.60%	7.60%
Specific reserve for impaired loans	$ 28,924	$ 28,924	$ 28,118	$ 27,122	$ 26,000	$ 24,562	$ 23,400
Additions		8,100
Paydowns and chargeoffs		200
Additions to level 3 from foreclosed loans		300
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of impaired loans	11,500	11,500		4,200
Specific reserve for impaired loans	2,100	2,100		$ 2,400
Increase to level 3 from migrated branches taken out of service	$ 2,000
Reductions related to sale of loans		$ 5,300