Basis of Presentation and Accounting Policies - Additional Information (Detail)	3 Months Ended
Mar. 31, 2013
Basis Of Presentation [Line Items]
Number of branches operated	57
Minimum [Member]
Basis Of Presentation [Line Items]
Intangible assets amortized over an estimated useful life	3 years
Maximum [Member]
Basis Of Presentation [Line Items]
Intangible assets amortized over an estimated useful life	10 years

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

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