Assets Held for Sale - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Property, Plant and Equipment Assets Held-for-sale Disclosure [Abstract]
Fair value of assets held for sale	$ 10.3
Percentage of fair value of assets held for sale under sales assistance agreement		50.00%
Renewal term of sales assistance agreement	6 months

Fair value portion of assets classified as held for sale.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258

Name:	us-gaap_AssetsHeldForSaleLongLivedFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant