Warrants - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]
Warrants exercised	2,168,335	80,014
Weighted average exercise price	7.91	4.08
Proceeds from exercise of warrants	$ 17.1	$ 0.3

The cash inflow from issuance of rights to purchase common shares at predetermined price (usually issued together with corporate debt).

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

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