Debt - Debt (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 326,147	$ 331,354
Less current maturities	19,669	18,806
Long-term debt	306,478	312,548
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Total debt	$ 99,606	$ 99,617
Debt instrument interest rate percentage	3.95%	3.95%
Unsecured private placement 3.95% note [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2021	2021
Unsecured private placement 3.95% note [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2027	2027
Unsecured private placement 3.86% note [Member]
Debt Instrument [Line Items]
Total debt	$ 99,595	$ 99,560
Debt instrument interest rate percentage	3.86%	3.86%
Unsecured private placement 3.86% note [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2019	2019
Unsecured private placement 3.86% note [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2025	2025
Unsecured private placement 4.86% note [Member]
Debt Instrument [Line Items]
Total debt	$ 64,764	$ 64,740
Debt instrument interest rate percentage	4.86%	4.86%
Unsecured private placement 4.86% note [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2017	2017
Unsecured private placement 4.86% note [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2023	2023
Unsecured private placement 5.88% note [Member]
Debt Instrument [Line Items]
Total debt	$ 34,162	$ 39,860
Debt instrument interest rate percentage	5.88%	5.88%
Unsecured private placement 5.88% note [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2016	2016
Unsecured private placement 5.88% note [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2022	2022
Unsecured private placement 5.69% note [Member]
Debt Instrument [Line Items]
Total debt	$ 17,108	$ 17,096
Debt instrument interest rate percentage	5.69%	5.69%
Unsecured private placement 5.69% note [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2016	2016
Unsecured private placement 5.69% note [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2018	2018
Unsecured U.S. bank debt [Member]
Debt Instrument [Line Items]
Maturity Dates	2019	2019
Debt of foreign subsidiaries Unsecured bank debt, foreign currency [Member]
Debt Instrument [Line Items]
Total debt	$ 2,960	$ 4,810
Maturity Dates	2016	2016
Debt of foreign subsidiaries Unsecured bank term loan, foreign currency [Member]
Debt Instrument [Line Items]
Total debt	$ 3,373	$ 3,724
Maturity Dates	2021	2021
Debt of foreign subsidiaries Secured bank debt, foreign currency [Member]
Debt Instrument [Line Items]
Total debt	$ 4,579	$ 1,947
Maturity Dates	2016	2016

Debt instruments maturity year.

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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.

+ References

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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