Debt - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013	Feb. 15, 2013	Jun. 22, 2012
Debt Disclosure [Line Items]
Maximum borrowing under PNC facility		$ 40,000,000	$ 27,000,000
Fees and expenses relating to creation of PNC facility			245,000
Borrowings outstanding under PNC facility	28,187,000
Available borrowing under PNC facility	7,179,000
PNC Facility effective rate of interest	2.50%
Interest rate description under PNC facility	Interest charges with respect to loans are computed on the actual principal amount of loans outstanding during the month at a rate per annum equal to (A) with respect to domestic rate loans, the sum of (i) a rate per annum equal to the higher of (1) the base commercial lending rate of PNC, (2) the federal funds open rate plus .5% and (3) the daily LIBOR plus 1%, plus (ii) .5% and (B) with respect to Eurodollar rate loans, the sum of the Eurodollar rate plus 2.25%.
Domestic Rate Loans
Debt Disclosure [Line Items]
PNC facility spread rate for calculation of interest	0.50%
Domestic Rate Loans | Federal Funds Base Rate
Debt Disclosure [Line Items]
PNC facility spread rate for calculation of interest	0.50%
Domestic Rate Loans | Libor Rate
Debt Disclosure [Line Items]
PNC facility spread rate for calculation of interest	1.00%
Eurodollar Rates
Debt Disclosure [Line Items]
PNC facility spread rate for calculation of interest	2.25%
Term Loan
Debt Disclosure [Line Items]
Maximum borrowing under PNC facility		4,000,000	4,000,000
Revolving Credit Facility
Debt Disclosure [Line Items]
Maximum borrowing under PNC facility		$ 36,000,000	$ 23,000,000