Borrowings - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016	Jun. 30, 2017 USD ($)	Jun. 30, 2016	Dec. 31, 2016 USD ($)
Credit Facilities [Line Items]
Short-term borrowings	$ 10,000,000		$ 10,000,000		$ 10,000,000
Revolving Credit Facility
Credit Facilities [Line Items]
Credit facility capacity	100,000,000		$ 100,000,000
Credit facility expiration date			Oct. 24, 2019
Credit facility capacity, outstanding	45,000,000		$ 45,000,000
Short-term borrowings	$ 10,000,000		$ 10,000,000
Line of credit interest rate during period (as a percent)	2.70%	2.00%	2.60%	2.10%
Unamortized debt issuance costs	$ 224,000		$ 224,000		$ 272,000
Interest coverage ratio, minimum	3.5		3.5
Leverage ratio, minimum	2.5		2.5