Short and Long-Term Debt - Schedule of Outstanding Debt (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Total	$ 361,311	$ 474,499
Amounts due within one year	20,000	26,667
Long-term debt	341,311	447,832
Senior Notes Payable Through 2021, 5.41%
Debt Instrument [Line Items]
Senior notes payable	$ 0	26,667
Senior notes, interest rate	5.41%
Senior Notes Payable Through 2021, 4.00%
Debt Instrument [Line Items]
Senior notes payable	$ 60,000	80,000
Senior notes, interest rate	4.00%
Senior Notes Payable Through 2031, 3.40%
Debt Instrument [Line Items]
Senior notes payable	$ 69,604	74,139
Senior notes, interest rate	3.40%
Master Note Facility Due in 2022
Debt Instrument [Line Items]
Debt Instrument, Covenant, Fixed Charges Coverage Ratio, Minimum	1.50
Debt Instrument, Covenant, Consolidated Leverage Ratio, Maximum	3.50
Debt Instrument, Covenant, Consolidated Leverage Ratio In Period Of Acquisition, Maximum	4.00
Revolving Credit Facility
Debt Instrument [Line Items]
Senior revolving credit facility maturing in 2023, net of debt issuance costs	$ 231,707	$ 293,693

Debt Instrument, Covenant, Consolidated Leverage Ratio In Period Of Acquisition, Maximum

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Debt Instrument, Covenant, Consolidated Leverage Ratio, Maximum

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Debt Instrument, Covenant, Fixed Charges Coverage Ratio, Minimum

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

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