Borrowing Facilities (Details) THB in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017 THB	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Nov. 12, 2015 USD ($)
Line of Credit Facility [Line Items]
Credit Agreement maturity date	Nov. 12, 2020
Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit Agreement description	The Company has a $430 million Credit Agreement (the Credit Agreement) by and among Benchmark, JPMorgan Chase Bank, N.A. as administrative agent and collateral agent (the Administrative Agent), and the financial institutions acting as lenders thereunder from time to time. This Credit Agreement provides for a five-year $200 million revolving credit facility and a five-year $230 million term loan facility (the Term Loan), both with a maturity date of November 12, 2020.
Credit Agreement capacity						$ 430.0
Description of variable interest rate basis	Interest on outstanding borrowings under the Credit Agreement accrues, at our option, at (a) the adjusted London interbank offered rate (LIBOR) plus 1.25% to 2.25%, or (b) the alternative base rate plus 0.25% to 1.25%, and is payable quarterly in arrears. The alternative base rate is equal to the highest of (i) the Administrative Agent’s prime rate, (ii) the federal funds rate plus 0.50% and (iii) the adjusted LIBOR rate plus 1.00%. The margin on the interest rates fluctuates based upon the ratio of the Company’s debt to its consolidated EBITDA.
Credit Agreement covenant terms	The Credit Agreement contains financial covenants as to debt leverage and interest coverage, and certain customary affirmative and negative covenants, including restrictions on our ability to incur additional debt and liens, pay dividends, repurchase shares, sell assets and merge or consolidate with other persons. Amounts due under the Credit Agreement may be accelerated upon specified events of default, including a failure to pay amounts due, breach of a covenant, material inaccuracy of a representation, or occurrence of bankruptcy or insolvency, subject, in some cases, to cure periods.
Credit agreement, secured by percentage of stock of the Company's domestic subsidiaries	100.00%
Credit agreement, secured by percentage of voting capital stock of each direct foreign subsidiary	65.00%
Credit Agreement covenant compliance	As of March 31, 2017 and December 31, 2016, the Company was in compliance with all of these covenants and restrictions.
Credit Agreement [Member] | JP Morgan Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit Agreement issuer	JPMorgan Chase Bank, N.A. as administrative agent and collateral agent (the Administrative Agent), and the financial institutions acting as lenders thereunder from time to time.
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit Agreement capacity						200.0
Term period	5 years
Credit Agreement maturity date	Nov. 12, 2020
Possible increase to total commitments under Credit Agreement						150.0
Letters of credit outstanding amount						2.1
Revolving credit facility, available for future borrowings						197.9
Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Term period	5 years
Credit Agreement maturity date	Nov. 12, 2020
Term Loan Description	a five-year $230 million term loan facility (the Term Loan), both with a maturity date of November 12, 2020.
Term Loan proceeds							$ 230.0
Term Loan frequency of periodic payments	quarterly
Derivative Notional Amount						161.7
Principal amount						215.6
Term Loan Facility [Member] | Interest Rate Swap [Member]
Line of Credit Facility [Line Items]
Derivative Notional Amount						161.7
Term Loan Facility [Member] | Scenario Forecast [Member]
Line of Credit Facility [Line Items]
Quarterly principal installments		$ 8.6	$ 5.8	$ 4.3	$ 2.9
Standby Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Revolving credit facility, available for future borrowings						20.0
Foreign currencies [Member]
Line of Credit Facility [Line Items]
Revolving credit facility, available for future borrowings						$ 20.0
Thailand Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit Agreement maturity date	Oct. 31, 2017
Thailand Subsidiary [Member] | Thailand Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit Agreement capacity | THB	THB 350
Minimum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
U.S. Credit facility, commitment fee	0.30%
Maximum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
U.S. Credit facility, commitment fee	0.40%
LIBOR Plus [Member] | Minimum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
LIBOR Plus [Member] | Maximum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.25%
Alternate Base Rate Plus [Member] | Minimum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.25%
Alternate Base Rate Plus [Member] | Maximum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%