Fair Value of Financial Instruments - Carrying Value and Fair Value of Long-Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	$ 444,142	$ 375,161
Fair Value	451,357	384,268
Revolving Credit Facility Due Mar. 2020 And Nov. 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	130,000	61,595
Fair Value	130,000	61,595
5.375% Notes, Due Oct. 2020 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	250,000	250,000
Fair Value	256,623	256,563
2.40% Term Loan, Due Jun. 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	8,151	8,282
Fair Value	8,349	8,877
2.05% Term Loan, Due Mar. 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	35,023	35,163
Fair Value	35,570	37,089
1.30% Term Loan, Due Jun. 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	9,781	9,788
Fair Value	9,712	10,062
1.55% Term Loan, Due Sep. 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	11,187	10,333
Fair Value	$ 11,103	$ 10,082