Segment Information, Nature of Operations, and Certain Concentrations - Profit (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2012
Segment Reporting, Profit Reconciling Item [Line Items]
Senior notes interest rate	3.95%
Senior notes maturity period	Sep. 15, 2022
Senior Notes due 2022 [Member]
Segment Reporting, Profit Reconciling Item [Line Items]
Senior notes interest rate	3.95%
Senior notes maturity period	Sep. 15, 2022
Senior notes due 2010 [Member]
Segment Reporting, Profit Reconciling Item [Line Items]
Senior notes interest rate	5.00%
Senior notes maturity period	Jun. 15, 2010

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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)(2))

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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration