Net Income Per Share - Reconciliation between Basic and Diluted Weighted Average Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 152,400	$ 113,896
Net income attributable to unvested awarded performance stock	(5,192)	(3,201)
Net income attributable to common shares	$ 147,208	$ 110,695
Weighted average number of common shares outstanding – basic	282,397	280,564
Less unvested awarded performance stock included in weighted average number of common shares outstanding – basic	(9,621)	(7,885)
Weighted average number of common shares outstanding for basic net income per common share	272,776	272,679
Dilutive effect of stock options	2,085	2,335
Weighted average number of shares outstanding – diluted	274,861	275,014
Basic (in dollars per share)	$ 0.54	$ 0.41
Diluted (in dollars per share)	$ 0.54	$ 0.40