Accounts Receivable, Net of Allowance (Schedule of Activity, Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts [Rollforward]
Allowance for doubtful accounts at beginning of year	$ 7.7	$ 13.9
Provision for doubtful accounts	2.9	2.1
Amounts charged against the allowance	(2.2)	(8.3)
Allowance for doubtful accounts at end of year	$ 8.4	$ 7.7