Subsequent Events - Additional Information (Detail) (Subsequent Event [Member], USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
Nov. 05, 2013
Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock public offering, shares	34,883,721
Common stock public offering, per share	$ 2.15
Common stock public offering, net proceeds	$ 72

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

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