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Financial Instruments - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Financial Instruments [Line Items]          
Period cash equivalents and short-term investments have been in continuous unrealized gain (loss) position, years, maximum     1 year    
Credit Agreement [Member] | Revolving Credit Facility [Member] | BMO Harris Bank N.A. ("BMO Harris") [Member]          
Financial Instruments [Line Items]          
Revolving credit facility $ 50,000,000.0   $ 50,000,000.0    
Percentage of cash and marketable securities deposited with bank collateral for securitization 100.00%   100.00%    
Credit facility borrowings $ 0   $ 0   $ 0
Revolving credit facility maturity date     Jan. 20, 2022    
CCKF [Member]          
Financial Instruments [Line Items]          
Percentage of investment in equity affiliate 30.70%   30.70%    
Non controlling interest $ 3,200,000   $ 3,200,000    
CCKF [Member] | Maximum [Member]          
Financial Instruments [Line Items]          
Gain (loss) from investment in affiliate (100,000) $ 100,000 200,000 $ 100,000  
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]          
Financial Instruments [Line Items]          
Total short-term investments (available for sale), Fair value $ 38,200,000   $ 38,200,000   1,700,000
Certificate Of Deposit Commercial Paper And Treasury Bills [Member] | Level 2 [Member]          
Financial Instruments [Line Items]          
Total short-term investments (available for sale), Fair value         $ 5,100,000