Derivative Instruments (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Sep. 30, 2017
Derivative
Derivative Instruments in Hedges, Net Investment in Foreign Operations, Assets, Fair Value, Net			$ 15,500,000	$ 14,800,000
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ 700,000	$ 800,000.0
Foreign currency derivatives
Derivative
Derivative, Notional Amount	39,700,000
Commodity derivative contracts
Derivative
Derivative, Notional Amount	180,800,000		143,900,000
Unrealized (loss) gain in other comprehensive income	$ (1,900,000)		$ 4,700,000