Convertible Senior Notes (Warrants) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2013
Debt Disclosure [Abstract]
Proceeds from sale of warrants	$ 38.4
Shares exercisable upon conversion	9.8
Strike price (USD per share)	$ 34.2

The cash inflow associated with the amount received from holders exercising their stock warrants.

No definition available.

Name:	us-gaap_ProceedsFromWarrantExercises
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration