Earnings per Share - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 21, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive securities excluded from diluted earnings per share calculation (in shares)		479,000	269,000	378,000	149,000
Shares of common stock issued (in shares)	2,702,500
Net proceeds from issuance of common stock	$ 55,700,000			$ 0	$ 55,641,000
CapGen Capital Group III LP
Shares of common stock issued (in shares)	6,210,000
Net proceeds from issuance of common stock	$ 0