Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Feb. 07, 2018	Dec. 31, 2017	Dec. 31, 2019	Feb. 13, 2017
Dividends, Common Stock [Abstract]
Dividends Payable, Date Declared	Feb. 28, 2020
Dividends Payable, Amount Per Share	$ 0.075
Dividends Payable, Date of Record	Mar. 13, 2020
Dividends Payable, Date to be Paid	Mar. 30, 2020
Payment, Tax Withholding, Share-based Payment Arrangement	$ 32.1	$ 36.8
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred Stock, Shares Authorized	100.0				100.0
Preferred Stock, Shares Issued	0.0				0.0
Preferred Stock, Shares Outstanding	0.0				0.0
Stock Repurchase Program, Authorized Amount						$ 300.0
Stock Repurchase Program, Period in Force			3 years
Treasury Stock, Shares, Acquired				133.5
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 166.5
Dividend Declared [Member]
Dividends, Common Stock [Abstract]
Dividends, Common Stock, Cash	14.4
Dividend Paid [Member]
Dividends, Common Stock [Abstract]
Dividends, Common Stock, Cash	14.2
Restricted Stock Units (RSUs) [Member]
Dividends, Common Stock [Abstract]
Dividends Paid, Share-based compensation, Cash	$ 0.5
Vesting of restricted stock units	0.9
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation	0.3
Stock, Shares Issued Net of Shares for Tax Withholdings	0.6