Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2018	Jan. 01, 2018
Statement of Stockholders' Equity [Abstract]
Dividends per share on common stock (in usd per share)	$ 0.64	$ 0.64	$ 0.61
Retained earnings	$ (1,835.5)	$ (1,735.2)
ASU 2018-02
Tax Cuts And Jobs Act Of 2017 reclassification from accumulated other comprehensive income to retained earnings Tax Effect	$ 13.4			$ 13.4
ASU 2016-16
Retained earnings					$ 1.0
ASU 2014-09
Retained earnings					$ (2.4)