Contingencies (Guarantees and Other Similar Matters Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Contingent liability related to performance surety bonds	$ 30,000,000
Redeemable noncontrolling interest	37,000,000	$ 38,000,000
Letter of Credit [Member]
Loss Contingencies [Line Items]
Credit line available under the agreement	57,000,000
Credit Agreement [Member] | Revolving Credit Facility [Member]
Loss Contingencies [Line Items]
Credit line available under the agreement	$ 3,000,000,000
Debt instrument, term	5 years