Financing Arrangement (Convertible Note Hedge and Warrants Issuance) (Details) $ / shares in Units, shares in Thousands, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2011 USD ($)	Jan. 06, 2017	Dec. 31, 2015 $ / shares shares	Dec. 31, 2015 $ / shares shares	Jul. 14, 2011 $ / shares shares
Financing Arrangements
Shares Received Under Convertible Note Hedge | shares			1,700	5,100
Share Price | $ / shares			$ 68.72	$ 68.72
Convertible Note Hedge [Member]
Financing Arrangements
Amount paid for Convertible Note Hedge | $	$ 107
Warrants
Financing Arrangements
Number of Trading Days Warrants are Exercisable		60
Strike price of warrants | $ / shares					$ 41.14
Proceeds from Warrants transaction | $	$ 65
Warrants - Underlying
Financing Arrangements
Shares covered by warrants issuance | shares					19,900
Warrants - Estimated
Financing Arrangements
Shares covered by warrants issuance | shares			8,000	8,000
Convertible Debt
Financing Arrangements
Debt Instrument, Convertible, Conversion Price | $ / shares					$ 31.74