Fair Value Measurement and Fair Value of Financial Instruments - Estimated Fair Values and Related Carrying Values of Financial Instruments (Detail) - USD ($)	Jun. 30, 2016	Dec. 31, 2015	Aug. 31, 2013
4.375% Senior Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carry value	$ 248,182,000	$ 248,053,000	$ 250,000,000
Fair value	$ 267,613,000	$ 254,075,000
Stated interest percentage	4.375%	4.375%	4.375%
Interest rate swap agreements
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carry value	$ 6,592,000	$ 4,474,000
Fair value	$ 6,592,000	$ 4,474,000

Contractual interest rate for funds borrowed, under the debt agreement.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Fair value portion of notes payable.

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