Debt - Credit Facilities (Details) - USD ($)			6 Months Ended
	May 26, 2017	Feb. 03, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Line of Credit Facility [Line Items]
Gross Carrying Amount			$ 4,440,000,000		$ 4,940,000,000
Repayments of long-term debt			4,251,000,000	$ 1,566,000,000
Proceeds from new note issuances			3,741,000,000	$ 2,520,000,000
Revolver
Line of Credit Facility [Line Items]
Maximum borrowing capacity					250,000,000
Amount drawn on the Revolver			0
Line of Credit
Line of Credit Facility [Line Items]
Repayments of long-term debt			1,700,000,000
Line of Credit | 2016 TLA
Line of Credit Facility [Line Items]
Gross Carrying Amount					$ 2,700,000,000
Repayments of long-term debt		$ 139,000,000	139,000,000
Line of Credit | 2017 TLA
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 2,550,000,000
Repayments of long-term debt	$ 1,200,000,000		$ 361,000,000
Interest rate on credit facility (as a percent)			2.48%
Write-off of unamortized discount and deferred financing costs	12,000,000
2022, 2027, and 2047 Notes | Unsecured Debt
Line of Credit Facility [Line Items]
Proceeds from new note issuances	$ 1,200,000,000