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Stockholders' Equity - Additional Information (Detail) - USD ($)
3 Months Ended 12 Months Ended
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Equity [Line Items]              
Series A preferred stock pays a cumulative dividend         $ 1.00 $ 1.00 $ 1.00
Received distributions from the earnings of subsidiaries         $ 121,300,000 $ 96,600,000 $ 122,200,000
Capital contributions to subsidiaries         0 0 $ 0
Series A [Member]              
Equity [Line Items]              
Series A preferred stock pays a cumulative dividend $ 0.25 $ 0.25 $ 0.25 $ 0.25      
Preferred stock aggregate dividends         10,000 $ 10,000  
UPCIC [Member]              
Equity [Line Items]              
Statutory capital contribution $ 30,000,000.0       $ 30,000,000.0