Financing Arrangement (0.75% Convertible senior notes due 2016) (Details) (USD $)
1 Months Ended 12 Months Ended 21 Months Ended
Jul. 31, 2011
Mar. 31, 2015
Jun. 30, 2016
Mar. 31, 2014
Jul. 14, 2011
Financing Arrangement [Line Items]          
0.75% Convertible senior notes due 2016, net (short-term)   $ 602,000,000   $ 0  
Convertible Senior Notes, Carrying Value   0   580,000,000  
Temporary equity   31,000,000   0  
Debt Instrument, Convertible, Carrying Amount of Equity Component   107,000,000   107,000,000  
Debt Instrument, Frequency of Periodic Payment semiannually        
Share Price   $ 58.24      
Debt Instrument, Convertible, If-converted Value in Excess of Principal   528,000,000      
Convertible Debt          
Financing Arrangement [Line Items]          
Principal amount   633,000,000   633,000,000  
Convertible Senior Notes, Carrying Value   602,000,000   580,000,000  
Debt Instrument, Unamortized Discount (Premium), Net   31,000,000   53,000,000  
Debt Instrument, Date of First Required Payment Jan. 15, 2012        
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
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%        
Effective interest rate         4.54%
Debt issuance costs         15,000,000
Debt instrument remaining discount amortization period (in years)     1 year 3 months    
Convertible Debt | Liability Component [Member]          
Financing Arrangement [Line Items]          
Convertible Senior Notes, Carrying Value         525,000,000
Debt issuance costs         13,000,000
Convertible Debt | Equity Component          
Financing Arrangement [Line Items]          
Debt issuance costs         2,000,000
Convertible Debt          
Financing Arrangement [Line Items]          
Debt Instrument, Fair Value Disclosure   $ 1,158,000,000   $ 731,000,000  
Contractual interest rate of 0.75% Convertible Senior Notes due 2016         0.75%