Earnings Per Share (Narrative) (Details) (USD $)	9 Months Ended	3 Months Ended	9 Months Ended
Sep. 30, 2013 Convertible Senior Notes 2032 [Member]	Sep. 30, 2012 Convertible Senior Notes 2025 [Member]	Sep. 30, 2012 Convertible Senior Notes 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Stock Price Trigger	$ 32.53	$ 38.57	$ 38.57

Price of the entity's common stock which would be required to be attained for the conversion feature embedded in the debt instrument to become effective.

No definition available.

Name:	us-gaap_DebtInstrumentConvertibleStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration