Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Basis of Presentation - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	27 Months Ended	39 Months Ended	48 Months Ended	51 Months Ended
	Dec. 31, 2009	Dec. 31, 2010	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Convertible Senior Notes 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prior period reclassification adjustment to decrease deferred tax liability and increase additional paid-in capital	$ 499.6	$ 467.1	$ 357.2	$ 352.6
Debt Instrument [Line Items]
Convertible senior notes included in calculation of net income per share					$ 1,725
Convertible senior notes interest rate					1.75%