Investments - Assets Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level3) (Detail) $ in Thousands	6 Months Ended
Jun. 30, 2015 USD ($)
Investments, Debt and Equity Securities [Abstract]
Beginning balance	$ 7,374
Unrealized gain (loss)	0
Ending balance	$ 7,374

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

Name:	us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration