Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to the Company	$ 15,269	$ 13,069	$ 27,225	$ 36,937
Weighted average number of shares:
Weighted average number of shares used in calculating basic net income per share	32,187	32,104	32,160	32,079
Effect of dilutive stock-based compensation plans:
Stock options	27	37	33	39
Weighted average number of shares used in calculating diluted net income per share	32,214	32,141	32,193	32,118
Average market price of common stock used for calculation of dilutive shares	$ 53.49	$ 42.03	$ 49.49	$ 38.97
Net income per share:
Basic	0.47	0.41	0.85	1.15
Diluted	$ 0.47	$ 0.41	$ 0.85	$ 1.15