Earnings per Share (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings per Share
Adjustments to net income (in dollars)	$ 0	$ 0	$ 0	$ 0
Antidilutive securities (in shares)	537,000	0	513,000	0
Numerator:
Net income	$ 20,049,000	$ 72,433,000	$ 58,914,000	$ 142,357,000
Denominator:
Basic: weighted-average shares outstanding (in shares)	129,856,730	134,420,380	129,876,218	134,655,217
Add: weighted-average equity-based awards (in shares)	148,465	231,628	287,504	269,114
Diluted: weighted-average shares outstanding (in shares)	130,005,195	134,652,008	130,163,722	134,924,331
Basic earnings per share (in dollars per share)	$ 0.15	$ 0.54	$ 0.45	$ 1.06
Diluted earnings per share (in dollars per share)	$ 0.15	$ 0.54	$ 0.45	$ 1.06