Fair Value Measurements - Additional Information (Detail)	Jun. 30, 2013 7.875% Senior Notes due 2021 [Member]	Jan. 29, 2013 7.875% Senior Notes due 2021 [Member]	Dec. 31, 2012 7.875% Senior Notes due 2021 [Member]	Jun. 30, 2013 Convertible Senior Notes due March 2028 [Member]	Dec. 31, 2012 Convertible Senior Notes due March 2028 [Member]	Jun. 30, 2012 Convertible Senior Notes due March 2028 [Member]	Dec. 31, 2011 Convertible Senior Notes due March 2028 [Member]	Dec. 31, 2010 Convertible Senior Notes due March 2028 [Member]
Fair Value Measurements [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.875%	7.875%	7.875%	3.25%	3.25%	3.25%	3.25%	3.25%

Interest rate stated in the contractual debt agreement.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant