Unrecognized Share-Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 39,651
Stock option
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	15,464
Average Expected Recognition Period - in Years	2 years 7 months 10 days
Restricted stock units
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 24,187
Average Expected Recognition Period - in Years	2 years 8 months 10 days

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant