Earnings Per Share (Details) - USD ($) $ / shares in Units, $ 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	$ 53,137	$ 21,482	$ 139,909	$ 95,439
Basic weighted average number of shares outstanding (in shares)	196,121,691	196,445,684	196,577,436	196,311,529
Dilutive effect of stock options and RSUs (in shares)	2,537,768	3,006,624	2,681,324	2,978,488
Diluted weighted average number of shares outstanding (in shares)	198,659,459	199,452,308	199,258,760	199,290,017
Basic net income per common share (in usd per share)	$ 0.27	$ 0.11	$ 0.71	$ 0.49
Diluted net income per common share (in usd per share)	$ 0.27	$ 0.11	$ 0.70	$ 0.48
Anti-dilutive shares excluded from diluted earnings per share computation (in shares)	606,903	385,861	486,008	407,845