Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash flow hedge instrument term, maximum	12 months
Cumulative unrealized gain (loss) on cash flow derivative instruments in accumulated other comprehensive loss	$ 1.6	$ 2.2