Fair Value Measurements (Gross Amounts and Fair Value of Debt) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Term Loan Due 2026
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 469,411	$ 523,688
Senior Notes 6.75
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	452,836	500,000
Fair Value, Inputs, Level 2 | Term Loan Due 2026
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	460,023	528,684
Fair Value, Inputs, Level 2 | Senior Notes 6.75
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	$ 464,157	$ 533,250