Debt (Details)	1 Months Ended						3 Months Ended		6 Months Ended
	Apr. 30, 2020 USD ($)	Apr. 30, 2020 KRW (₩)	Jan. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)	May 31, 2015	Jun. 30, 2020 USD ($)	Jun. 30, 2020 KRW (₩)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	May 31, 2020 KRW (₩)	Oct. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Long-term Debt				$ 1,460,351,000			$ 1,554,664,000		$ 1,554,664,000
Less: Unamortized discount and deferred debt costs, net				(10,117,000)			(9,403,000)		(9,403,000)
Less: Short-term borrowings and current portion of long-term debt				(144,479,000)			(148,872,000)		(148,872,000)
Long-term debt				1,305,755,000			1,396,389,000		1,396,389,000
Proceeds from revolving credit facilities									282,000,000	$ 85,000,000
Repayments of revolving credit facilities									$ 216,000,000	$ 5,000,000
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%
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%
Senior Notes | 6.625% Senior notes, due September 2027
Debt Instrument [Line Items]
Debt				525,000,000			$ 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									$ 30,000,000.0
Unused borrowing capacity							$ 30,000,000.0		30,000,000.0
Repayments of revolving credit facilities									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		0
Line of Credit | $30 million revolving credit facility, applicable bank rate plus 1.51% | Korea
Debt Instrument [Line Items]
Debt				0			30,000,000		30,000,000
Credit facility, borrowing capacity							30,000,000.0		$ 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%
Proceeds from revolving credit facilities							$ 30,000,000.0
Weighted average interest rate (as a percent)							2.21%		2.21%
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		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%
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%
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		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				20,000,000			$ 56,000,000		$ 56,000,000
Credit facility, borrowing capacity				56,000,000.0
Interest rate at period end (as a percent)							2.78%		2.78%
Proceeds from revolving credit facilities				20,000,000.0					$ 36,000,000.0
Repayments of revolving credit facilities									36,000,000.0
Subsidiary Term Loans | Term loan, fund floating rate plus 1.60%, due June 2020 | Korea
Debt Instrument [Line Items]
Debt				24,000,000			$ 0		0
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%
Subsidiary Term Loans | Term loan, fixed rate at 1.80%, due May 2021 | Korea
Debt Instrument [Line Items]
Debt				0			$ 0		$ 0
Stated interest rate (as a percent)							1.80%		1.80%		1.80%
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				40,000,000			40,000,000		$ 40,000,000
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%
Subsidiary Term Loans | Term loan, applicable bank rate plus 2.03%, due September 2022 | Korea
Debt Instrument [Line Items]
Debt				60,000,000			$ 140,000,000		$ 140,000,000
Interest rate at period end (as a percent)							2.94%		2.94%
Face amount of debt													$ 140,000,000.0
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%
Subsidiary Term Loans | Term loan, applicable bank rate plus 1.77%, due April 2023 | Korea
Debt Instrument [Line Items]
Debt				0			$ 124,715,000		$ 124,715,000
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%
Subsidiary Term Loans | Term loan, LIBOR plus 2.56%, due December 2023 | Korea
Debt Instrument [Line Items]
Debt				200,000,000			80,000,000		$ 80,000,000
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%
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
Subsidiary Term Loans | Term loan, applicable bank rate plus 1.98%, due December 2028 | Korea
Debt Instrument [Line Items]
Debt				66,000,000			90,000,000		$ 90,000,000
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%
Subsidiary Term Loans | Short-term term loans, variable rate | Japan
Debt Instrument [Line Items]
Debt				7,071,000			4,762,000		$ 4,762,000
Unused borrowing capacity							$ 6,500,000		$ 6,500,000
Subsidiary Term Loans | Short-term term loans, variable rate | Japan | Weighted Average
Debt Instrument [Line Items]
Weighted average interest rate (as a percent)							0.18%		0.18%
Subsidiary Term Loans | Short-term term loans, variable rate | Japan | TIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)									0.10%
Subsidiary Term Loans | Short-term term loans, variable rate | Japan | TIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)									0.20%
Subsidiary Term Loans | Term loan, fixed rate at 0.86%, due June 2022 | Japan
Debt Instrument [Line Items]
Debt				23,018,000			$ 18,531,000		$ 18,531,000
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				5,064,000			$ 4,169,000		$ 4,169,000
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				179,541,000			$ 156,583,000		$ 156,583,000
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				262,407,000			$ 237,654,000		$ 237,654,000
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				29,000,000			$ 28,500,000		$ 28,500,000
Subsidiary Term Loans | Term Loan, LIBOR plus 1.40% due March 2022 | China
Debt Instrument [Line Items]
Debt				$ 19,250,000			$ 18,750,000		$ 18,750,000
Subsidiary Term Loans | Term loan, entered in April 2020 | Korea
Debt Instrument [Line Items]
Interest rate at period end (as a percent)		2.87%
Face amount of debt | ₩		₩ 150,000,000,000
Payments of long-term debt | ₩		₩ 150,000,000,000
Proceeds from issuance of long-term debt	$ 124,700,000