Financial Instruments - Summarization for Foreign Currency Forward Purchase and Sale Contracts (Details) - Sep. 30, 2017 - Foreign Exchange Forward Contracts € in Millions, £ in Millions, CAD in Millions, $ in Millions	CAD	GBP (£)	USD ($)	EUR (€)
British, Pounds | Long
Derivative [Line Items]
Notional Amount in Foreign Currency | £		£ 10
Canada, Dollars | Short
Derivative [Line Items]
Notional Amount in Foreign Currency | CAD	CAD 2
European, Euro | Short
Derivative [Line Items]
Notional Amount in Foreign Currency | €				€ 4
U.S., Dollars | Long
Derivative [Line Items]
Notional Amount in Foreign Currency			$ 7
U.S., Dollars | Short
Derivative [Line Items]
Notional Amount in Foreign Currency			$ 14