Share Repurchases (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Nov. 29, 2018	May 25, 2017
Equity, Class of Treasury Stock [Line Items]
Shares repurchased	1,000,000.0	900,000
Value of shares repurchased	$ 35,000,000	$ 50,000,000	$ 175,000,000
Treasury stock acquired, average cost per share (in usd per share)	$ 35.83	$ 56.19
5/25/2017 Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount (in usd)					$ 200,000,000.0
Shares repurchased		2,700,000
Value of shares repurchased		$ 175,000,000.0
Treasury stock acquired, average cost per share (in usd per share)		$ 64.94
11/29/2018 Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount (in usd)				$ 300,000,000.0
Shares repurchased			0