Quarterly report pursuant to Section 13 or 15(d)

Line of Credit - Additional Information (Detail)

v2.4.0.6
Line of Credit - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 6 Months Ended
May 31, 2011
Jun. 30, 2012
Line of Credit Facility [Line Items]    
Revolving credit facility, maximum borrowing capacity $ 60  
Revolving credit facility, expiration date Dec. 31, 2012  
Revolving credit facility, interest rate description   Amounts borrowed under the revolver bear interest, at our option, at the prime lending rate established by JPMorgan Chase Bank, N.A. or LIBOR plus 1.5 percent. We pay a fee on a quarterly basis of one-fourth of one percent per annum on the weighted-average unused portion of the revolver.
Revolving credit facility, interest rate above LIBOR   1.50%
Revolving credit facility, unused quarterly commitment fee   0.25%
Total outstanding letters of credit   35.9
Revolving credit facility, unused portion   $ 24.1
Line of credit covenant, Earnings before interest, taxes, depreciation and amortization (EBITDA) to interest expense ratio   4.0
Minimum
    
Line of Credit Facility [Line Items]    
Line of credit covenant, current ratio   1.25
Line of credit covenant, debt to net worth   0.5
Extended Expiration
    
Line of Credit Facility [Line Items]    
Revolving credit facility, expiration date Dec. 31, 2013