Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings per Share
Adjustments to net income (in dollars)			$ 0	$ 0
Antidilutive securities (in shares)			0	0
Numerator:
Net income	$ 69,053	$ 56,895	$ 137,011	$ 113,635
Denominator:
Basic: weighted-average shares outstanding (in shares)	137,907,063	139,546,615	138,749,209	139,546,174
Add: weighted-average equity-based awards (in shares)	158,816	99,502	142,746	98,383
Diluted: weighted-average shares outstanding (in shares)	138,065,879	139,646,117	138,891,955	139,644,557
Basic earnings per share (in dollars per share)	$ 0.50	$ 0.41	$ 0.99	$ 0.81
Diluted earnings per share (in dollars per share)	$ 0.50	$ 0.41	$ 0.99	$ 0.81