Commitments and Contingencies - Additional Information (Detail) - Claim	6 Months Ended	12 Months Ended
Jun. 30, 2015	Dec. 31, 2014
Indemnification Agreement [Member]
Loss Contingencies [Line Items]
Claims received by fund	0	0

The total number of new claims filed pertaining to a loss contingency during the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Name:	us-gaap_LossContingencyNewClaimsFiledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration