Subsequent Events - Additional Information (Detail) - Subsequent Event [Member]	Jul. 13, 2015 USD ($)
Subsequent Event [Line Items]
Registration payment arrangement, maximum potential consideration	$ 200,000,000
Market Issuance Sales Agreement With Cantor Fitzgerald [Member]
Subsequent Event [Line Items]
Registration payment arrangement, maximum potential consideration	$ 50,000,000

Describes the maximum potential amount of consideration, undiscounted, that could be transferred under the registration payment arrangement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6449706&loc=d3e16207-108621

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