Stockholders' Equity - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 30, 2015
Equity Class Of Treasury Stock [Line Items]
Other Restrictions on Payment of Dividends	Our U.S. Credit Facility permits us to pay dividends up to $3.0 million per fiscal year to its stockholders so long as we have not defaulted at the time of such dividend and no default would result from declaring or paying such dividend.
Common stock par value	$ 0.666	$ 0.666
Stock repurchase program expiration date	Dec. 31, 2019
Common shares repurchased during period, shares	300,000	691,196
Common shares repurchased during period, value	$ 8,745,000	$ 18,014,000	$ 11,009,000
Stock Repurchase Program
Equity Class Of Treasury Stock [Line Items]
Common stock par value				$ 0.666
Stock Repurchase Program | Maximum
Equity Class Of Treasury Stock [Line Items]
Authorized amount of common stock under stock repurchase program				$ 100,000,000