Stock Repurchase Plan - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Feb. 09, 2017	Oct. 31, 2015
Equity Class Of Treasury Stock [Line Items]
Total cost of shares repurchased		$ 122,000,000	$ 84,900,000
2015 Repurchase Plan
Equity Class Of Treasury Stock [Line Items]
Authorized amount to repurchase outstanding common stock					$ 250,000,000
2017 Repurchase Plan
Equity Class Of Treasury Stock [Line Items]
Authorized amount to repurchase outstanding common stock				$ 300,000,000
Remaining amount of authorized under 2017 Repurchase Plan	$ 270,700,000	270,700,000
2015 & 2017 Repurchase Plan
Equity Class Of Treasury Stock [Line Items]
Total cost of shares repurchased	$ 1,200,000	$ 122,000,000