Assets Measured at Level Three Fair Value on Non-recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Goodwill	$ 74.0
Intangible assets	$ 2.1

This item represents the cumulative amount paid in excess of fair value for acquired assets from one or more business combinations, after to the initial recording thereof.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 33

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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