Fair Value Measurements of Assets and Liabilities - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Other-than-temporary impairments	$ 0	$ 0	$ 0
Valuation techniques, description	There were no changes to our valuation techniques during 2014.

Amount after tax of other than temporary impairment (OTTI) on investment in available-for-sale debt security, recognized in other comprehensive loss, attributable to parent entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Name:	us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAvailableforsaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration