Equity Affiliates - Additional Information (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Dividends received from equity affiliates		$ 16	$ 11	$ 16
Equity method investments		160
Discount rate used in assessment of fair value	16.00%
Impairment of equity affiliate				$ 39
Equity method investment carrying amount over the book value		26
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments		5
Goodwill [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment carrying amount over the book value		$ 19
Other Than Goodwill [Member] | Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Estimated useful life		5 years
Other Than Goodwill [Member] | Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Estimated useful life		45 years