Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Face (par) amount of debt instrument at time of issuance.

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- Definition

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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Amount of unamortized debt discount (premium) and debt issuance costs.

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- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

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The effective interest rate at the end of the reporting period.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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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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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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Weighted average interest rate of long-term debt outstanding calculated at point in time.

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The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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The cash outflow for the settlement of obligation drawn from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

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Debt (Details)	1 Months Ended		9 Months Ended
Debt (Details)	Apr. 30, 2020 KRW (₩)	Jan. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 KRW (₩)	Sep. 30, 2019 USD ($)	Oct. 31, 2020 USD ($)	Sep. 30, 2020 KRW (₩)	May 31, 2020 USD ($)	May 31, 2020 KRW (₩)	Dec. 31, 2019 USD ($)	Oct. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)
Debt Instrument [Line Items]
Long-term Debt			$ 1,328,191,000							$ 1,460,351,000
Less: Unamortized discount and deferred debt costs, net			(9,092,000)							(10,117,000)
Less: Short-term borrowings and current portion of long-term debt			(136,526,000)							(144,479,000)
Long-term debt			1,182,573,000							1,305,755,000
Proceeds from revolving credit facilities			312,000,000		$ 172,700,000
Repayments of revolving credit facilities			$ 332,000,000		$ 92,700,000
Term loan, LIBOR plus 1.60%, due March 2022 \| China \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.60%	1.60%
Term Loan, LIBOR plus 1.40% due March 2022 \| China \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.40%	1.40%
Senior Notes \| 6.625% Senior notes, due September 2027
Debt Instrument [Line Items]
Debt			$ 525,000,000							525,000,000
Stated interest rate (as a percent)			6.625%				6.625%
Line of Credit \| Revolving Credit Facility \| Korea
Debt Instrument [Line Items]
Credit facility, borrowing capacity											$ 30,000,000.0
Proceeds from revolving credit facilities			$ 60,000,000.0
Unused borrowing capacity			30,000,000.0
Repayments of revolving credit facilities			60,000,000.0
Line of Credit \| Revolving Credit Facility \| Korea \| Subsequent Event
Debt Instrument [Line Items]
Credit facility, borrowing capacity						$ 30,000,000.0
Line of Credit \| $30 million revolving credit facility, LIBOR plus the applicable bank rate \| Korea
Debt Instrument [Line Items]
Debt			0							0
Line of Credit \| $30 million revolving credit facility, applicable bank rate plus 1.51% \| Korea
Debt Instrument [Line Items]
Debt			0							0
Credit facility, borrowing capacity								$ 30,000,000.0
Unused borrowing capacity			$ 30,000,000.0
Line of Credit \| $30 million revolving credit facility, applicable bank rate plus 1.51% \| Korea \| Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.51%	1.51%
Proceeds from revolving credit facilities			$ 30,000,000.0
Payments of long-term debt			30,000,000.0
Line of Credit \| $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) \| Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, borrowing capacity														$ 250,000,000.0
Proceeds from revolving credit facilities			150,000,000.0
Remaining borrowing capacity			250,000,000.0
Repayments of revolving credit facilities			$ 150,000,000.0
Line of Credit \| $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) \| Revolving Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.25%	1.25%
Line of Credit \| $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) \| Revolving Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.75%	1.75%
Line of Credit \| $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) \| Revolving Credit Facility \| Singapore
Debt Instrument [Line Items]
Debt			$ 0							0
Line of Credit \| Revolving credit facility, TAIFX plus the applicable bank rate, due December 2024 (Taiwan) \| Revolving Credit Facility \| Taiwan
Debt Instrument [Line Items]
Debt			0							20,000,000
Long-term Debt										56,000,000.0
Credit facility, borrowing capacity										36,000,000.0
Proceeds from revolving credit facilities			72,000,000.0
Unused borrowing capacity			36,000,000.0
Face amount of debt										20,000,000.0
Repayments of revolving credit facilities			92,000,000.0
Subsidiary Term Loans \| Term loan, fund floating rate plus 1.60%, due June 2020 \| Korea
Debt Instrument [Line Items]
Debt			0							24,000,000
Face amount of debt													$ 90,000,000.0
Proceeds from issuance of long-term debt			$ 24,000,000.0
Weighted average interest rate (as a percent)			4.21%				4.21%
Subsidiary Term Loans \| Term loan, fund floating rate plus 1.60%, due June 2020 \| Korea \| Fund Floating Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.60%	1.60%
Subsidiary Term Loans \| Term loan, fixed rate at 1.80%, due May 2021 \| Korea
Debt Instrument [Line Items]
Debt			$ 0							0
Stated interest rate (as a percent)			1.80%				1.80%	1.80%	1.80%
Unused borrowing capacity \| ₩							₩ 60,000,000,000
Face amount of debt \| ₩									₩ 60,000,000,000
Payments of long-term debt			$ 48,400,000	₩ 60,000,000,000
Proceeds from issuance of long-term debt			48,400,000	₩ 60,000,000,000
Subsidiary Term Loans \| Term loan, applicable bank rate plus 2.03%, due July 2022 \| Korea
Debt Instrument [Line Items]
Debt			0							40,000,000
Face amount of debt												$ 40,000,000.0
Payments of long-term debt			$ 40,000,000.0
Subsidiary Term Loans \| Term loan, applicable bank rate plus 2.03%, due July 2022 \| Korea \| Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			2.03%	2.03%
Subsidiary Term Loans \| Term loan, applicable bank rate plus 2.03%, due September 2022 \| Korea
Debt Instrument [Line Items]
Debt			$ 100,000,000							60,000,000
Interest rate at period end (as a percent)			2.68%				2.68%
Face amount of debt												$ 140,000,000.0
Payments of long-term debt			$ 40,000,000.0
Proceeds from issuance of long-term debt			$ 80,000,000.0
Subsidiary Term Loans \| Term loan, applicable bank rate plus 2.03%, due September 2022 \| Korea \| Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			2.03%	2.03%
Subsidiary Term Loans \| Term loan, applicable bank rate plus 1.77%, due April 2023 \| Korea
Debt Instrument [Line Items]
Debt			$ 128,187,000							0
Subsidiary Term Loans \| Term loan, applicable bank rate plus 1.77%, due April 2023 \| Korea \| Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.77%	1.77%
Subsidiary Term Loans \| Term loan, LIBOR plus 2.56%, due December 2023 \| Korea
Debt Instrument [Line Items]
Debt			$ 20,000,000							200,000,000
Subsidiary Term Loans \| Term loan, LIBOR plus 2.56%, due December 2023 \| Korea \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			2.56%	2.56%
Subsidiary Term Loans \| Term loan, LIBOR plus 2.56%, due December 2023 \| Japan
Debt Instrument [Line Items]
Payments of long-term debt		$ 120,000,000.0	$ 60,000,000.0
Subsidiary Term Loans \| Term loan, applicable bank rate plus 1.98%, due December 2028 \| Korea
Debt Instrument [Line Items]
Debt			$ 90,000,000							66,000,000
Subsidiary Term Loans \| Term loan, applicable bank rate plus 1.98%, due December 2028 \| Korea \| Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			1.98%	1.98%
Subsidiary Term Loans \| Short-term term loans, variable rate
Debt Instrument [Line Items]
Debt			$ 3,250,000							0
Subsidiary Term Loans \| Short-term term loans, variable rate \| Japan
Debt Instrument [Line Items]
Debt			16,562,000							7,071,000
Unused borrowing capacity			$ 4,700,000
Subsidiary Term Loans \| Short-term term loans, variable rate \| Japan \| Weighted Average
Debt Instrument [Line Items]
Weighted average interest rate (as a percent)			0.26%				0.26%
Subsidiary Term Loans \| Short-term term loans, variable rate \| Japan \| TIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			0.15%	0.15%
Subsidiary Term Loans \| Short-term term loans, variable rate \| Japan \| TIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			0.30%	0.30%
Subsidiary Term Loans \| Term loan, fixed rate at 0.86%, due June 2022 \| Japan
Debt Instrument [Line Items]
Debt			$ 16,591,000							23,018,000
Stated interest rate (as a percent)			0.86%				0.86%
Subsidiary Term Loans \| Term loan, fixed rate at 0.60%, due July 2022 \| Japan
Debt Instrument [Line Items]
Debt			$ 3,792,000							5,064,000
Stated interest rate (as a percent)			0.60%				0.60%
Subsidiary Term Loans \| Term loan, fixed rate at 1.30%, due July 2023 \| Japan
Debt Instrument [Line Items]
Debt			$ 147,895,000							179,541,000
Stated interest rate (as a percent)			1.30%				1.30%
Subsidiary Term Loans \| Term loan, fixed rate at 1.35%, due December 2024 \| Japan
Debt Instrument [Line Items]
Debt			$ 229,664,000							262,407,000
Stated interest rate (as a percent)			1.35%				1.35%
Subsidiary Term Loans \| Term loan, LIBOR plus 1.60%, due March 2022 \| China
Debt Instrument [Line Items]
Debt			$ 28,500,000							29,000,000
Subsidiary Term Loans \| Term Loan, LIBOR plus 1.40% due March 2022 \| China
Debt Instrument [Line Items]
Debt			$ 18,750,000							$ 19,250,000
Subsidiary Term Loans \| Term loan, entered in April 2020 \| Korea
Debt Instrument [Line Items]
Interest rate at period end (as a percent)			2.56%				2.56%
Face amount of debt \| ₩	₩ 150,000,000,000
Payments of long-term debt \| ₩	₩ 150,000,000,000