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
Adjustments to net income (in dollars)	$ 0	$ 0	$ 0	$ 0
Antidilutive securities (in shares)	0	0	0	0
Numerator:
Net income	$ 58,363	$ 53,235	$ 171,998	$ 173,626
Denominator:
Basic: weighted-average shares outstanding (in shares)	139,556,532	139,500,542	139,549,665	139,473,360
Add: weighted-average equity-based awards (in shares)	139,798	3,016	120,822	1,013
Diluted: weighted-average shares outstanding (in shares)	139,696,330	139,503,558	139,670,487	139,474,373
Basic earnings per share (in dollars per share)	$ 0.42	$ 0.38	$ 1.23	$ 1.24
Diluted earnings per share (in dollars per share)	$ 0.42	$ 0.38	$ 1.23	$ 1.24