Long-Term Debt (Other Debt and Interest Payments Narrative) (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) item	Mar. 31, 2017 USD ($)
Debt Instrument [Line Items]
Interest Paid on borrowing	$ 212,000,000	$ 279,000,000
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative Liability, Number of Instruments Held | item	8
Interest Rate Swap, Currently Effective [Member]
Debt Instrument [Line Items]
Notional Amount, Liability	$ 2,200,000,000