Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	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, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to the Company													$ 52,733	$ 57,279	$ 41,569
Weighted average number of shares used in calculating basic net income per share													32,086	31,978	31,832
Stock options													39	58	99
Long-term incentive plan													45	52	57
Weighted average number of shares used in calculating diluted net income per share													32,170	32,088	31,988
Average market price of common stock used for calculation of dilutive shares													$ 40.25	$ 36.68	$ 36.29
Basic	$ 0.49	$ 0.41	$ 0.32	$ 0.42	$ 1.18	$ 0.30	$ (0.07)	$ 0.38	$ 0.26	$ 0.37	$ 0.35	$ 0.33	1.64	1.79	1.31
Diluted	$ 0.49	$ 0.41	$ 0.32	$ 0.42	$ 1.18	$ 0.30	$ (0.07)	$ 0.38	$ 0.25	$ 0.37	$ 0.35	$ 0.33	$ 1.64	$ 1.79	$ 1.30
Common Stock, shares outstanding	32,100				32,000				31,900				32,100	32,000	31,900