Financing Arrangement (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended					1 Months Ended		1 Months Ended		42 Months Ended		1 Months Ended	21 Months Ended
	Aug. 30, 2012	Jul. 31, 2011	Sep. 30, 2014	Mar. 31, 2014		Jul. 31, 2011 Convertible Note Hedge	Jul. 14, 2011 Convertible Note Hedge	Jul. 31, 2011 Warrants	Jul. 14, 2011 Warrants	Feb. 29, 2016 Revolving Credit Facility [Member]	Aug. 30, 2012 Revolving Credit Facility [Member]	Jul. 31, 2011 Convertible Debt days	Jun. 30, 2016 Convertible Debt	Sep. 30, 2014 Convertible Debt	Jul. 14, 2011 Convertible Debt	Jul. 14, 2011 Convertible Debt Liability Component	Jul. 14, 2011 Convertible Debt Equity Component	Jul. 14, 2011 Convertible Debt
Financing Arrangements
Principal amount			$ 633,000,000	$ 633,000,000										$ 633,000,000
Contractual interest rate of 0.75% Convertible Senior Notes due 2016															0.75%			0.75%
Debt Instrument, Date of First Required Payment												Jan. 15, 2012
Debt Instrument, Frequency of Periodic Payment		semiannually
Debt Instrument, Issuance Date												Jul. 15, 2011
Convertible Senior Notes due description												2016
0.75% Convertible Senior Notes due 2016 maturity date												Jul. 15, 2016
Conversion rate of Notes												31.5075
Face amount of Notes															1,000
Debt Instrument, Convertible, Conversion Price															$ 31.74
Line of Credit Facility, Initiation Date	Aug. 30, 2012
Number of trading days greater than or equal to the initial conversion price												20
Consecutive trading days under conversion trigger												30
Trigger price as percent of conversion price												130.00%
Trigger price												$ 41.26
Number of trading day that trading price falls below 98% of last reported sales price multiplied by conversion rate												5
Consecutive trading days under conversion trigger, trading price												10
Debt trading price as a percentage of stock price times conversion rate												98.00%
Convertible Senior Notes, Carrying Value			591,000,000	580,000,000	[1]											525,000,000
Effective interest rate															4.54%
Debt issuance costs											2,000,000				15,000,000	13,000,000	2,000,000
Debt instrument remaining discount amortization period													1 year 10 months
Shares covered by Hedge Transactions							19.9
Strike price for convertible note hedge							$ 31.74
Amount paid for Convertible Note Hedge						107,000,000
Shares covered by warrants issuance									19.9
Strike price of warrants									$ 41.14
Proceeds from Warrants transaction								65,000,000
Line of Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity											500,000,000
Line of Credit Facility, Expiration Date	Feb. 29, 2016
Line of Credit Facility Term										3 years 6 months
Option To Request Additional Commitments On Credit Facility											$ 250,000,000

[1] Derived from audited consolidated financial statements.