Goodwill, Customer Relationships and Other Intangible Assets - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	2 Months Ended	10 Months Ended	12 Months Ended
	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived and Indefinite-Lived Intangible Assets
Goodwill	$ 10,837		$ 10,837
Finite-lived intangible assets, net	8,845		8,845
Other indefinite-life intangible assets	0		0
Total other intangible assets, net	378		378
Impact to goodwill from business combination deferred state income tax differences	16		16
Acquired finite-lived intangible asset amortization expense	139
Intangible assets and goodwill	20,199		$ 20,199
Finite-lived intangible assets, useful life			11 years 10 months 24 days
Predecessor
Finite-Lived and Indefinite-Lived Intangible Assets
Goodwill				$ 7,729
Finite-lived intangible assets, net				860
Other indefinite-life intangible assets				15
Total other intangible assets, net				55
Acquired finite-lived intangible asset amortization expense		$ 168		211	$ 227
Customer relationships
Finite-Lived and Indefinite-Lived Intangible Assets
Finite-lived intangible assets, net	8,845		$ 8,845
Finite-lived intangible assets, accumulated amortization	126		$ 126
Finite-lived intangible assets, useful life			12 years 2 months 12 days
Customer relationships | Predecessor
Finite-Lived and Indefinite-Lived Intangible Assets
Finite-lived intangible assets, net				860
Finite-lived intangible assets, accumulated amortization				1,113
Trade names
Finite-Lived and Indefinite-Lived Intangible Assets
Finite-lived intangible assets, net	126		$ 126
Finite-lived intangible assets, accumulated amortization	4		$ 4
Finite-lived intangible assets, useful life			4 years 9 months 18 days
Trade names | Predecessor
Finite-Lived and Indefinite-Lived Intangible Assets
Finite-lived intangible assets, net				0
Finite-lived intangible assets, accumulated amortization				0
Developed technology
Finite-Lived and Indefinite-Lived Intangible Assets
Finite-lived intangible assets, net	252		$ 252
Finite-lived intangible assets, accumulated amortization	$ 9		$ 9
Finite-lived intangible assets, useful life			4 years 9 months 18 days
Developed technology | Predecessor
Finite-Lived and Indefinite-Lived Intangible Assets
Finite-lived intangible assets, net				40
Finite-lived intangible assets, accumulated amortization				$ 189