Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Non-financial assets and liabilities measured at fair value on a nonrecurring basis	$ 0.0		$ 0.0		$ 0.0
Increase (decrease) in fair value of marketable securities	$ 0.9	$ (1.1)	$ 1.4	$ (0.7)