Debt - Debt (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total debt	$ 341,453	$ 273,931
Less current maturities	21,671	27,034
Long-term debt	319,782	$ 246,897
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Total debt	$ 100,000
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	$ 100,000	$ 100,000
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	$ 65,000	$ 65,000
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	$ 40,000	$ 40,000
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	$ 22,857	$ 22,857
Debt instrument interest rate percentage	5.69%	5.69%
Unsecured private placement 5.69% note [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2015	2015
Unsecured private placement 5.69% note [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2018	2018
Unsecured private placement 6.86% note [Member]
Debt Instrument [Line Items]
Total debt		$ 4,284
Debt instrument interest rate percentage	6.86%	6.86%
Maturity Dates	2015	2015
Unsecured U.S. bank debt [Member]
Debt Instrument [Line Items]
Total debt		$ 20,000
Maturity Dates	2019	2019
Debt of foreign subsidiaries Unsecured bank debt, foreign currency [Member]
Debt Instrument [Line Items]
Total debt	$ 7,892	$ 12,043
Maturity Dates	2015	2015
Debt of foreign subsidiaries Unsecured bank term loan, foreign currency [Member]
Debt Instrument [Line Items]
Total debt	$ 3,993	$ 4,840
Maturity Dates	2021	2021
Debt of foreign subsidiaries Secured bank term loan, foreign currency [Member]
Debt Instrument [Line Items]
Total debt		$ 2,723
Maturity Dates	2015	2015
Debt of foreign subsidiaries Secured bank debt, foreign currency [Member]
Debt Instrument [Line Items]
Total debt	$ 1,211	$ 1,638
Maturity Dates	2015	2015
Debt of foreign subsidiaries Unsecured bank debt, U.S dollars [Member]
Debt Instrument [Line Items]
Total debt	$ 500	$ 546
Maturity Dates	2015	2015

Debt instruments maturity year.

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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.

+ Details

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. 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 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 2: 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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Section S99

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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20, 22

-Article 5

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- Definition

Amount of long-term debt, after unamortized discount or premium, scheduled 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 210.5-02.19,20)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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+ 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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