Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income attributable to the Company													$ 57,279	$ 41,569	$ 17,517
Weighted average number of shares used in calculating basic net income per share													31,978	31,832	31,649
Stock options													58	99	129
Long-term incentive plan													52	57	156
Weighted average number of shares used in calculating diluted net income per share													32,088	31,988	31,934
Average market price of common stock used for calculation of dilutive shares													$ 36.68	$ 36.29	$ 31.85
Basic	$ 1.18	$ 0.30	$ (0.07)	$ 0.38	$ 0.26	$ 0.37	$ 0.35	$ 0.33	$ 0.27	$ 0.15	$ (0.23)	$ 0.36	1.79	1.31	0.55
Diluted	$ 1.18	$ 0.30	$ (0.07)	$ 0.38	$ 0.25	$ 0.37	$ 0.35	$ 0.33	$ 0.27	$ 0.15	$ (0.23)	$ 0.36	$ 1.79	$ 1.30	$ 0.55
Common Stock, shares outstanding	32,000				31,900				31,800				32,000	31,900	31,800