Weighted - Average Assumptions (Detail) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Risk-free interest rate	1.40%	2.60%	2.20%
Expected life	5 years 8 months 12 days	5 years 6 months	5 years 3 months 18 days
Expected volatility	68.00%	69.00%	65.00%
Expected dividend yield	$ 0	$ 0	$ 0

Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedVolatilityRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Risk-free interest rate assumption used in valuing an instrument.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsRiskFreeInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average expected dividend for an entity using a valuation technique with different dividend rates during the contractual term.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsWeightedAverageExpectedDividend
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration