Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings per Share
Adjustments to net income (in dollars)	$ 0	$ 0	$ 0	$ 0
Antidilutive securities (in shares)	0	0	0	0
Numerator:
Net income	$ 67,388	$ 58,363	$ 204,399	$ 171,998
Denominator:
Basic: weighted-average shares outstanding (in shares)	135,466,669	139,556,532	137,643,005	139,549,665
Add: weighted-average equity-based awards (in shares)	208,829	139,798	166,568	120,822
Diluted: weighted-average shares outstanding (in shares)	135,675,498	139,696,330	137,809,573	139,670,487
Basic earnings per share (in dollars per share)	$ 0.50	$ 0.42	$ 1.48	$ 1.23
Diluted earnings per share (in dollars per share)	$ 0.50	$ 0.42	$ 1.48	$ 1.23