Long-Term Debt (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	May. 31, 2015	Apr. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Oct. 27, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Senior notes	$ 1,750,000,000
Loss on early debt extinguishment			$ 0	$ 0	$ (85,000,000)	$ 0
2.7% Senior Notes due June 2020
Debt Instrument [Line Items]
Senior notes	$ 850,000,000
Debt interest rate (as percent)	2.70%
3.85% Senior Notes due June 2025
Debt Instrument [Line Items]
Senior notes	$ 900,000,000
Debt interest rate (as percent)	3.85%
Senior notes, interest rate increase in the event the Company's credit rating is downgraded below investment grade (as percent)	2.00%
3.125% Senior Notes due June 2016
Debt Instrument [Line Items]
Debt interest rate (as percent)			3.125%		3.125%
Face value of the debt repaid					$ 600,000,000
6.8% Senior Notes due November 2017
Debt Instrument [Line Items]
Debt interest rate (as percent)			6.80%		6.80%
Face value of the debt repaid					$ 500,000,000
Term loan
Debt Instrument [Line Items]
Repayment of debt					180,000,000
3.125% Senior Notes due October 2015
Debt Instrument [Line Items]
Senior notes			$ 300,000,000		$ 300,000,000			$ 300,000,000
Debt interest rate (as percent)			3.125%		3.125%			3.125%
3.125% Senior Notes due October 2015 | Subsequent event
Debt Instrument [Line Items]
Senior notes							$ 300,000,000
Debt interest rate (as percent)							3.125%
Revolving credit facility
Debt Instrument [Line Items]
Revolving credit facility with a syndicate of banks		$ 2,000,000,000
Commitment fees		0
Compensating balance requirements		$ 0