Fair Value of Financial Instruments - Carrying Value and Fair Value of Long-Term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	$ 296,755	$ 315,419
Fair Value	297,023	315,646
Revolving Credit Facility Due Mar. 2020 And Nov. 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	36,531	36,813
Fair Value	36,531	36,813
Term Loan, Due Feb. 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	235,379	249,715
Fair Value	235,379	249,715
2.40% Term Loan, Due Jun. 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	2,094	2,629
Fair Value	2,116	2,651
2.05% Term Loan, Due Mar. 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	12,516	14,737
Fair Value	12,669	14,873
1.30% Term Loan, Due Jun. 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	3,769	4,382
Fair Value	3,784	4,384
1.55% Term Loan, Due Sep. 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	6,466	7,143
Fair Value	$ 6,544	$ 7,210