Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to the Company	$ 1,117	$ 10,367	$ 11,956	$ 23,868
Weighted average number of shares:
Weighted average number of shares used in calculating basic net income per share	32,166	32,093	32,147	32,067
Effect of dilutive stock-based compensation plans:
Stock options	34	38	35	39
Weighted average number of shares used in calculating diluted net income per share	32,200	32,131	32,182	32,106
Average market price of common stock used for calculation of dilutive shares	$ 48.44	$ 39.47	$ 47.47	$ 37.40
Net income per share:
Basic	0.03	0.32	0.37	0.74
Diluted	$ 0.03	$ 0.32	$ 0.37	$ 0.74