Earnings Per Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings (numerator)
Net income attributable to common stockholders	$ 30,908	$ 14,450	$ 74,502	$ 28,846
Shares (denominator)
Weighted average common shares outstanding (basic)	50,115	49,057	49,713	48,633
Dilutive effect of stock options and stock awards outstanding	962	1,359	1,170	1,428
Adjusted weighted average common shares outstanding (diluted)	51,077	50,416	50,883	50,061
Earnings per share attributable to common stockholders
Basic	$ 0.62	$ 0.29	$ 1.50	$ 0.59
Diluted	$ 0.61	$ 0.29	$ 1.46	$ 0.58
Stock options and stock awards excluded from EPS calculation because the effect would be anti-dilutive		651	94	704