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Long-Term Debt (6.125% Senior Notes due 2021) - Additional Information (Detail) - 6.125% Senior Notes Due 2021 [Member] - USD ($)
6 Months Ended
Mar. 12, 2013
Jun. 30, 2021
Debt Instrument [Line Items]    
Issued Senior Notes $ 150,000,000.0  
Debt instrument interest rate 6.125% 6.125%
Debt instrument maturity date Mar. 15, 2021  
Interest on the notes   payable semi-annually in arrears on March 15 and September 15 of each year
Debt instrument, redemption date   Jun. 24, 2020