Credit Facilities and Debt (Textuals) (Details)					9 Months Ended
		Apr. 11, 2016 USD ($)	Mar. 27, 2015 USD ($)	Sep. 20, 2011 USD ($)	Sep. 30, 2016 USD ($)		Aug. 15, 2016 USD ($)	Mar. 11, 2016 EUR (€)	Dec. 31, 2015 USD ($)		Dec. 03, 2015 USD ($)	Dec. 03, 2015 EUR (€)
Debt Instrument
Bridge Loan							$ 1,300,000,000
Commercial paper outstanding					$ 20,000,000				$ 0
Commercial paper face amount					$ 600,000,000
Weighted average interest rate					0.75%
Letter of Credit
Debt Instrument
Debt instrument aggregate principal amount			$ 100,000,000
Revolving Credit Facility
Debt Instrument
Term of debt			5 years
Debt instrument aggregate principal amount			$ 600,000,000
Permitted increases in Credit Facility borrowing base			200,000,000
Maximum permitted increases in Credit Facility borrowing base			$ 800,000,000
Interest rate per annum, effective rate					1.00%
Maximum leverage ratio					4.00
Maximum leverage ratio subsequent					3.5
Risk Sharing Finance Facility Agreement
Debt Instrument
Research and development facility agreement					$ 42,000,000				76,000,000
Senior Notes
Debt Instrument
Redemption price percentage				101.00%
Senior Notes Due 2016, 3.550%
Debt Instrument
Interest on notes due				3.55%
Senior Notes Due				$ 600,000,000	0	[1]			600,000,000	[1]
Settlement of debt		$ 607,000,000
Settlement of debt, interest amount					7,000,000
Senior Notes Due 2021, 4.875%
Debt Instrument
Fair value of senior notes due					654,000,000				640,000,000
Interest on notes due				4.875%
Senior Notes Due				$ 600,000,000	600,000,000	[1]			600,000,000	[1]
Senior Notes Due 2023, 2.250%
Debt Instrument
Fair value of senior notes due					608,000,000
Senior Notes Due	[1]				$ 560,000,000				$ 0
Senior Notes Due 2023, 2.250% | Senior Notes
Debt Instrument
Interest on notes due								2.25%
Face amount | €								€ 500,000,000
Risk Sharing Finance Facility Agreement
Debt Instrument
Face amount											$ 135,000,000	€ 120,000,000
Maximum leverage ratio					3.50
Risk Sharing Finance Facility Agreement | Loans payable
Debt Instrument
Term of debt					12 years

[1] The fair value of our Senior Notes (as defined below) was determined using quoted prices in active markets for identical securities, which are considered Level 1 inputs. The fair value of our Senior Notes due 2021 was $654 million and $640 million as of September 30, 2016 and December 31, 2015, respectively. The fair value of our Senior Notes due 2023 was $608 million as of September 30, 2016.