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

Debt (Parenthetical) (Detail)	Jun. 30, 2012 8.375% Senior Notes Due In 2017	Mar. 31, 2012 8.375% Senior Notes Due In 2017	Dec. 31, 2011 8.375% Senior Notes Due In 2017	Nov. 13, 2009 8.375% Senior Notes Due In 2017	Jun. 30, 2012 8.125% Senior Notes Due In 2018	Dec. 31, 2011 8.125% Senior Notes Due In 2018	Aug. 17, 2010 8.125% Senior Notes Due In 2018
Debt Instrument [Line Items]
Interest rate on notes	8.375%	8.375%	8.375%		8.125%	8.125%	8.125%
Debt instrument maturity period	2017	2017			2018
Discount rate on issue of senior notes				1.425%