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, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 16,173	$ 37,190	$ 14,199	$ (10,440)	$ 28,673	$ 30,759	$ 9,613	$ (8,560)	$ 57,122	$ 60,485	$ 25,346
Weighted average common stock outstanding, basic (in shares)									39,557	39,337	39,096
Dilutive effect of stock options and restricted stock units1									668	531	699
Weighted average common stock outstanding, diluted (in shares)									40,225	39,868	39,795
Basic (in dollars per share)	$ 0.41	$ 0.94	$ 0.36	$ (0.27)	$ 0.73	$ 0.78	$ 0.24	$ (0.22)	$ 1.44	$ 1.54	$ 0.65
Diluted (in dollars per share)	$ 0.40	$ 0.92	$ 0.35	$ (0.27)	$ 0.72	$ 0.77	$ 0.24	$ (0.22)	$ 1.42	$ 1.52	$ 0.64