Background (Details) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
New Accounting Pronouncement, Early Adoption [Line Items]
Number of reportable segments | segment	1
Provisional income tax expense (benefit)			$ 195
Provisional income tax expense (benefit), purchase accounting adjustment	$ 83
Contract Acquisition and Fulfillment Costs
New Accounting Pronouncement, Early Adoption [Line Items]
Amortization period	30 months
Adjustments for New Accounting Pronouncement
New Accounting Pronouncement, Early Adoption [Line Items]
Production and distribution costs		$ 70
Accounting Standards Update 2014-09 | Accumulated Deficit
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative effect of new accounting principle in period of adoption			9
Cumulative effect of new accounting, tax			$ 3
Accounting Standards Update 2018-02
New Accounting Pronouncement, Early Adoption [Line Items]
Reclassification from AOCI to retained earnings, tax effect	$ 6