Debt (Details) (Senior Subordinated Convertible Notes [Member], USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 NotesConverted
Senior Subordinated Convertible Notes [Member]
Debt Instrument [Line Items]
Stated Interest Rate Percentage - Debt Instruments (in hundredths)	3.75%
Maturity year of Senior subordinated convertible notes	2034
First Conversion Date	Jan. 15, 2009
Number of Notes Converted	6,963
Cash Payments for Debt Conversions (in millions)	$ 14.7
Deferred Tax Liability (in millions)	0.74
Per Note Conversion Price (in dollars per share)	$ 497.14
Principal note amount (in millions)	5
Excess above Principal Note Amount (in millions)	$ 16
If converted, issuance of common stock shares (in shares)	90,835