General (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
	Jan. 01, 2018	Jun. 30, 2017	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss)
Cumulative effect of new accounting principle in period of adoption	$ (151.2)
ASU 2014-09
New accounting pronouncement or change in accounting principle, effect of change on beginning retained earnings	3.0
ASU 2017-07
New accounting pronouncement or change in accounting principle, effect of change on other income		$ 7.0	$ 13.9
New accounting pronouncement or change in accounting principle, effect of change on operating results		$ (7.0)	$ (13.9)
ASU 2018-02
New accounting pronouncement or change in accounting principle, effect of change on beginning retained earnings	151.0
Cumulative effect of new accounting principle in period of adoption	$ (151.0)