Income Taxes - Additional Information (Detail) (USD $)	6 Months Ended
Jun. 30, 2013
Income Tax Examination [Line Items]
Tax years open to examination	Years ended December 31, 2009 through December 31, 2012
Adjustments to the federal tax returns	$ 0
Maximum [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Tax years under audit	2008
Minimum [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Tax years under audit	2007

The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

Name:	us-gaap_IncomeTaxExaminationLiabilityRefundAdjustmentFromSettlementWithTaxingAuthority
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant