Summary of Notes Payable (Parenthetical) (Detail)	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Average interest rate	3.07%	3.49%

Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of debt outstanding by type or by instrument at that time.

No definition available.

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant