Goodwill and Other Intangible Assets (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Definite-lived intangible assets
Carrying amount of indefinite-lived intangible assets	$ 647	$ 645
Carrying amount of indefinite-lived intangible assets - trade names	67	67
Gross Carrying Amount	572	498
Accumulated Amortization	(434)	(390)
Net Carrying Amount	138	108
Definite-lived intangible assets acquired during the year, amount assigned	$ 54
Definite-lived intangible assets acquired during the year, weighted-average amortization period	9 years
Aggregate amortization expense for definite-lived intangible assets	$ 27	28	$ 33
Estimated intangible amortization expense for next five years:
2018	29
2019	26
2020	20
2021	17
2022	15
Customer relationships [Member]
Definite-lived intangible assets
Gross Carrying Amount	194	144
Accumulated Amortization	(124)	(112)
Net Carrying Amount	70	32
Contracts [Member]
Definite-lived intangible assets
Gross Carrying Amount	222	213
Accumulated Amortization	(194)	(177)
Net Carrying Amount	28	36
Other [Member]
Definite-lived intangible assets
Gross Carrying Amount	156	141
Accumulated Amortization	(116)	(101)
Net Carrying Amount	$ 40	$ 40