Common Stock and Treasury Stock - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Common Stock [Line Items]
Share repurchase program, authorized amount	$ 75,800,000		$ 75,800,000
Stock repurchase program, remaining authorization amount	$ 19,800,000		$ 19,800,000
Stock Buy back Program [Member]
Common Stock [Line Items]
Stock Repurchased During Period, Shares	9,600	20,100	20,700	34,600
Stock Repurchased During Period, Value	$ 276,000	$ 748,000	$ 603,000	$ 1,295,000