Summary of Activity Related to Goodwill and Other Intangible Assets Net (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2012
Acquired Names of Business
Goodwill and Other Assets Disclosure [Line Items]
Unamortized acquired names	$ 11.7
Amortized acquired names	$ 0.1
Weighted-average amortization period	1 year 8 months 12 days
Noncompete Agreements
Goodwill and Other Assets Disclosure [Line Items]
Weighted-average amortization period	1 year 7 months 6 days
Reacquired Franchise Rights
Goodwill and Other Assets Disclosure [Line Items]
Weighted-average amortization period	1 year 1 month 6 days

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16265-109275

Name:	us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration