Debt (Schedule of Long Term Debt Instruments) (Parenthetical) (Details)	Mar. 31, 2014
Senior Notes [Member] | 4.875% Senior Notes [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	4.875%
Convertible Debt [Member] | 2011 4.0% Notes [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	4.00%
Convertible Debt [Member] | 2011 4.25% Notes [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	4.25%
Convertible Debt [Member] | 2009 4.0% Notes [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	4.00%
Convertible Debt [Member] | 2009 4.25% Notes [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	4.25%
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt instrument, weighted average interest rate	2.90%
Notes Payable [Member] | Equipment [Member]
Debt Instrument [Line Items]
Debt instrument, weighted average interest rate	3.00%