Significant Accounting Policies (Details 5) (USD $) In Millions, unless otherwise specified	1 Months Ended
Aug. 31, 2012 2 3/4 percent convertible senior notes	Mar. 31, 2013 2 3/4 percent convertible senior notes	Sep. 30, 2012 2 5/8 percent convertible subordinated notes
Long-term obligations
Interest rate on convertible debt (as a percent)		2.75%	2.625%
Debt issued	$ 201.3

Increase of additional borrowings on existing and new debt instruments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(f))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph f

-Article 4

Name:	us-gaap_DebtInstrumentIncreaseAdditionalBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration