Credit Facilities and Debt (Textuals) (Details)				3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 27, 2015 USD ($)	Sep. 20, 2011 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016	Dec. 31, 2016 USD ($)	Oct. 28, 2016 USD ($)	Oct. 28, 2016 EUR (€)	Oct. 24, 2016 USD ($)	Oct. 24, 2016 EUR (€)	Aug. 15, 2016 USD ($)	Mar. 11, 2016 USD ($)	Mar. 11, 2016 EUR (€)	Dec. 03, 2015 USD ($)	Dec. 03, 2015 EUR (€)
Debt Instrument
Bridge Loan											$ 1,300,000,000
Commercial Paper				$ 600,000,000
Commercial paper outstanding				$ 60,000,000		$ 65,000,000
Weighted average interest rate				1.17%		1.12%
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				3.50
Risk Sharing Finance Facility Agreement
Debt Instrument
Research and development facility agreement				$ 40,000,000		$ 38,000,000
European Investment Bank - Research and Development Finance Contract [Member]
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate				0.59%
Term of debt				11 years
Senior Notes
Debt Instrument
Redemption price percentage			101.00%
Line of Credit [Member]
Debt Instrument
Face amount							$ 113,000,000	€ 105,000,000	$ 161,000,000	€ 150,000,000
Senior Notes Due 2016, 3.550%
Debt Instrument
Interest on notes due			3.55%
Face amount			$ 600,000,000
Senior Notes Due 2021, 4.875%
Debt Instrument
Fair value of senior notes due				$ 652,000,000		651,000,000
Interest on notes due			4.875%
Senior Notes Due	[1]			600,000,000		600,000,000
Face amount			$ 600,000,000
Senior Notes Due 2023, 2.250%
Debt Instrument
Fair value of senior notes due				575,000,000		555,000,000
Senior Notes Due	[1]			$ 537,000,000		522,000,000
Senior Notes Due 2023, 2.250% | Senior Notes
Debt Instrument
Interest on notes due												2.25%	2.25%
Face amount												$ 500,000,000	€ 500,000,000
Risk Sharing Finance Facility Agreement
Debt Instrument
Face amount														$ 129,000,000	€ 120,000,000
Term of debt				5 years
Risk Sharing Finance Facility Agreement | Loans Payable [Member]
Debt Instrument
Term of debt				12 years
Senior Notes due 2026
Debt Instrument
Fair value of senior notes due				$ 494,000,000		487,000,000
Senior Notes Due				500,000,000		500,000,000
Senior Notes due 2046
Debt Instrument
Fair value of senior notes due				398,000,000		397,000,000
Senior Notes Due				400,000,000		400,000,000
Research and Development Facility Contract [Member]
Debt Instrument
Senior Notes Due				$ 113,000,000		$ 110,000,000

[1] The fair value of our Senior Notes 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 $652 million and $651 million as of March 31, 2017 and December 31, 2016, respectively. The fair value of our Senior Notes due 2023 was $575 million and $555 million as of March 31, 2017 and December 31, 2016, respectively. The fair value of our Senior Notes due 2026 was $494 million and $487 million as of March 31, 2017 and December 31, 2016, respectively.The fair value of our Senior Notes due 2046 was $398 million and $397 million as of March 31, 2017 and December 31, 2016, respectively.