Shareholders' Equity (Details) - USD ($)	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Feb. 12, 2018	Sep. 30, 2019	Dec. 31, 2018	Oct. 30, 2018	Oct. 29, 2018	Sep. 30, 2018	Nov. 29, 2017	Apr. 25, 2017
Distribution Made to Limited Partner [Line Items]
Authorized stock repurchase amount													$ 250,000,000.0
Remaining unused authorization for stock repurchase program										$ 78,300,000
Repurchase aggregate cost	$ 25,000,000.0	$ 18,000,000.0	$ 25,000,000.0	$ 300,000	$ 501,500,000
Repurchase of common stock included in accrued expenses	3,700,000						$ 3,700,000				$ 0
Repurchase of common stock included in accrued expenses	3,700,000						3,700,000				$ 0
October 2018 Stock Repurchase Program
Distribution Made to Limited Partner [Line Items]
Authorized stock repurchase amount									$ 300,000,000.0
Remaining unused authorization for stock repurchase program	$ 200,000,000.0						$ 200,000,000.0
Repurchase of common stock (in shares)	202,449						672,473
Repurchase aggregate cost	$ 25,000,000.0						$ 68,000,000.0
Repurchase of common stock included in accrued expenses								$ 2,500,000
Repurchase of common stock included in accrued expenses								$ 2,500,000
Tender Offer
Distribution Made to Limited Partner [Line Items]
Authorized stock repurchase amount												$ 500,000,000.0
Repurchase of common stock (in shares)						5,660,376
Repurchase aggregate cost						$ 500,000,000.0
Repurchase price (in dollars per share)						$ 88.33