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Debt Narrative (Details) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Apr. 18, 2017 USD ($) | Apr. 04, 2017 USD ($)
Line of Credit Facility |  |  |  |
Weighted average interest rate at end of period | 5.07% |  |  |
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months | $ 6,609,000 |  |  |
Letters of Credit Outstanding, Amount | 4,670,000 |  |  |
Commitment fees on unused lines of credit | $ 570,000 |  |  |
Debt, Weighted Average Interest Rate, net of Currency Swap Contract | 4.24% |  |  |
JPMorgan, 2017 Credit Agreement |  |  |  |
Line of Credit Facility |  |  |  |
LineOfCreditFacilityInterestRateMarginSpreadAddedToFederalFundsRateOnUSDollarBorrowings | 0.50% |  |  |
Line Of Credit Facility, Minimum LIBOR one month interest rate on borrowings denominated in US dollars | 0.00% |  |  |
LineOfCreditFacilityInterestRateMarginSpreadAddedtoLIBORRateOnUSDollarBorrowings | 1.00% |  |  |
Line Of Credit Facility, Minimum LIBOR one month interest rate on eurocurrency borrowings | 0.00% |  |  |
JPMorgan Chase Bank, National Association, Amended and Restated Credit Agreement |  |  |  |
Line of Credit Facility |  |  |  |
Weighted average interest rate at end of period |  | 1.64% |  |
Outstanding Borrowings |  | $ 25,000,000 |  | $ 45,000,000
Prudential Investment Management, Inc. Private Shelf Agreement |  |  |  |
Line of Credit Facility |  |  |  |
Maximum borrowing capacity |  | 80,000,000 |  |
Outstanding Borrowings |  | 11,143,000 |  |
Series A Notes |  |  |  |
Line of Credit Facility |  |  |  |
Face amount |  | $ 4,000,000 |  |
Interest rate, Stated percentage |  | 4.00% |  |
Debt Instrument Term |  | 7 years |  |
Maturity date range, Start |  | Mar. 08, 2017 |  |
Maturity date range, End |  | Mar. 08, 2018 |  |
Series B Notes |  |  |  |
Line of Credit Facility |  |  |  |
Face amount |  | $ 7,143,000 |  |
Interest rate, Stated percentage |  | 4.10% |  |
Debt Instrument Term |  | 10 years |  |
Maturity date range, Start |  | Jun. 28, 2017 |  |
Maturity date range, End |  | Jun. 28, 2021 |  |
HSBC Bank (China) Company Limited, Shanghai Branch |  |  |  |
Line of Credit Facility |  |  |  |
Maximum borrowing capacity |  | $ 5,000,000 |  |
Outstanding Borrowings |  | $ 0 |  |
Line of Credit |  |  |  |
Line of Credit Facility |  |  |  |
Outstanding Borrowings | $ 60,000,000 |  |  |
Line of Credit | JPMorgan, 2017 Credit Agreement |  |  |  |
Line of Credit Facility |  |  |  |
Line of Credit Facility, Current Borrowing Capacity | $ 400,000,000 |  |  |
Percentage of stock of first tier foreign subsidiaries granted to lenders | 65.00% |  |  |
Minimum interest rate spread added to adjusted LIBOR rate based on leverage ratio on Eurocurrency borrowings | 1.25% |  |  |
Maximum interest rate spread added to adjusted LIBOR rate based on leverage ratio on Eurocurrency borrowings | 2.25% |  |  |
Face amount |  |  | $ 300,000,000 |
LineOfCreditFacilityMinimumInterestRateMarginSpreadAddedtoLIBORRateOnUSDollarBorrowings | 0.25% |  |  |
LineOfCreditFacilityMaximumInterestRateMarginSpreadAddedToLIBORRateOnUSDollarBorrowings | 1.25% |  |  |
Debt Instrument, Notes Repurchase Price As Percentage Of Principal Amount In Changes Of Control | 101.00% |  |  |
Debt Instrument, Notes Repurchase Price As Percentage Of Principal Amount When Not Use Asset Sales Proceeds For Specific Purposes | 100.00% |  |  |
Revolving Credit Facility |  |  |  |
Line of Credit Facility |  |  |  |
Outstanding Borrowings | $ 20,000,000 |  |  |
Line of Credit Facility, Remaining Borrowing Capacity | 180,000,000 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months | 5,000,000 |  |  |
Long-term Debt, Additional Repayments of Principal in Next Twelve Months | 25,000,000 |  |  |
Long-term Debt, Current Maturities | 30,000,000 |  |  |
Revolving Credit Facility | JPMorgan, 2017 Credit Agreement |  |  |  |
Line of Credit Facility |  |  |  |
Line of Credit Facility, Current Borrowing Capacity | 200,000,000 |  |  |
Additional borrowing capacity available | $ 150,000,000 |  |  |
Minimum commitment fee percentage | 0.175% |  |  |
Maximum commitment fee percentage | 0.35% |  |  |
Minimum interest rate spread added to adjusted LIBOR rate based on leverage ratio on Eurocurrency borrowings | 1.075% |  |  |
Maximum interest rate spread added to adjusted LIBOR rate based on leverage ratio on Eurocurrency borrowings | 1.90% |  |  |
Debt Instrument, Covenant, Indebtedness to Adjusted EBITDA Ratio, Maximum | 4.25 |  |  |
Debt Instrument, Covenant, Adjusted EBITDA to Interest Expense Ratio, Maximum | 3.50 |  |  |
Debt Instrument, Covenant, Senior Secured Net Indebtedness to Adjusted EBITDA Ratio, Maximum | 3.50 |  |  |
Debt Instrument, Covenant, Net Leverage Ratio, Minimum | 3.00 |  |  |
LineOfCreditFacilityMinimumInterestRateMarginSpreadAddedtoLIBORRateOnUSDollarBorrowings | 0.075% |  |  |
LineOfCreditFacilityMaximumInterestRateMarginSpreadAddedToLIBORRateOnUSDollarBorrowings | 0.90% |  |  |
Letter of Credit |  |  |  |
Line of Credit Facility |  |  |  |
Line of Credit Facility, Remaining Borrowing Capacity | $ 175,330,000 |  |  |
Bonds |  |  |  |
Line of Credit Facility |  |  |  |
Face amount |  |  | $ 300,000,000 |
Interest rate, Stated percentage | 5.625% |  | 5.625% |
Minimum | Revolving Credit Facility | JPMorgan, 2017 Credit Agreement |  |  |  |
Line of Credit Facility |  |  |  |
Debt Instrument, Covenant, Repayment of Debt, Percentage of Excess Cash Flow | 25.00% |  |  |
Maximum | Revolving Credit Facility | JPMorgan, 2017 Credit Agreement |  |  |  |
Line of Credit Facility |  |  |  |
Debt Instrument, Covenant, Repayment of Debt, Percentage of Excess Cash Flow | 50.00% |  |  |

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- Definition 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. + 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 Reference 2: 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(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: 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 + Details
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