Acquisitions and Dispositions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended
Apr. 30, 2012
Business Acquisition [Line Items]
Percentage of ownership interest sold	80.00%
Gain on sale of business	$ 42.0

Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment.

No definition available.

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