Debt and Credit Facility (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Summary of Financing Arrangements

The following table summarizes the carrying amount of our borrowings under various financing arrangements (in millions):

				December 31,
Type of Borrowing	Issue Date	Due Date	Interest Rate	2017		2016
Senior Unsecured	September 2015	September 2018	1.85%	$	999	$	998
Senior Unsecured	September 2017	September 2018	3-month LIBOR + 0.17%	749		—
Term Loan	October 2017	October 2018	Variable	999		—
Senior Unsecured	September 2017	March 2019	3-month LIBOR + 0.22%	748		—
Senior Unsecured	March 2014	April 2019	2.05%	499		499
Term Loan	May 2016	May 2019	Variable	—		311
Senior Unsecured	September 2017	September 2019	1.85%	997		—
Senior Unsecured	September 2017	September 2019	3-month LIBOR + 0.25%	499		—
Senior Unsecured	November 2014	February 2020	2.35%	499		498
Senior Unsecured	September 2015	September 2020	2.55%	1,994		1,991
Term Loan	October 2017	October 2020	Variable	998		—
Senior Unsecured	March 2011	April 2021	4.50%	995		994
Senior Unsecured	December 2011	December 2021	4.40%	1,246		1,245
Senior Unsecured	September 2016	March 2022	1.95%	497		497
Senior Unsecured	September 2015	September 2022	3.25%	996		995
Term Loan	October 2017	October 2022	Variable	2,497		—
Senior Unsecured	September 2016	September 2023	2.50%	745		744
Senior Unsecured	March 2014	April 2024	3.70%	1,742		1,741
Senior Unsecured	November 2014	February 2025	3.50%	1,744		1,743
Senior Unsecured	September 2015	March 2026	3.65%	2,729		2,726
Senior Unsecured	September 2016	March 2027	2.95%	1,244		1,243
Senior Unsecured	September 2015	September 2035	4.60%	990		989
Senior Unsecured	September 2016	September 2036	4.00%	740		739
Senior Unsecured	December 2011	December 2041	5.65%	995		995
Senior Unsecured	March 2014	April 2044	4.80%	1,733		1,732
Senior Unsecured	November 2014	February 2045	4.50%	1,730		1,729
Senior Unsecured	September 2015	March 2046	4.75%	2,215		2,214
Senior Unsecured	September 2016	March 2047	4.15%	1,723		1,723
Total debt, net				33,542		26,346
Less current portion				2,747		—
Total long-term debt, net				$	30,795	$	26,346

Schedule of Contractual Maturities of Financing Obligations

As of December 31, 2017, the aggregate future principal maturities of financing obligations for each of the next five years, based on contractual due dates, are as follows (in millions):

	2018		2019		2020		2021		2022
Contractual Maturities	$	2,750	$	2,812	$	3,750	$	2,500	$	3,438