Intangible Assets Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets Acquired		$ 11	$ 26
Impairment of Intangible Assets (Excluding Goodwill)	$ 48
Amortization expense		$ 60	$ 88	$ 108