Debt (Interest Rates) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Oct. 31, 2019	Dec. 31, 2018	Nov. 30, 2015	May 31, 2015
Subsidiary Term Loans | Term loan, fund floating rate plus 1.60%, due June 2020 | Korea
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	3.90%		4.49%
Credit facility, borrowing capacity					$ 150,000,000.0
Subsidiary Term Loans | Term loan, LIBOR plus 2.56%, due December 2023 | Korea
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	4.49%		5.38%
Interest rate spread (as a percent)	2.56%
Subsidiary Term Loans | Term loan, LIBOR plus 1.80% due December 2019 | China
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	0.00%		4.22%
Subsidiary Term Loans | Term Loan, LIBOR plus 1.60% Due March 2022 | China
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	3.53%		0.00%
Subsidiary Term Loans | Term Loan, LIBOR plus 1.40% Due March 2022 | China
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	3.30%		0.00%
Revolving Credit Facility | Line of Credit | $30 million revolving credit facility, LIBOR plus the applicable bank rate, due October 2020 | Korea
Debt Instrument [Line Items]
Credit facility, borrowing capacity	$ 30,000,000	$ 30,000,000.0
Revolving Credit Facility | Line of Credit | Short-term term loans, variable rates | Japan
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	0.22%		0.24%
Revolving Credit Facility | Line of Credit | $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore)
Debt Instrument [Line Items]
Credit facility, borrowing capacity	$ 250,000,000
Revolving Credit Facility | Line of Credit | Revolving credit facility, TAIFX plus a bank-determined spread, due November 2020 | Taiwan
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	0.00%		4.26%
Credit facility, borrowing capacity				$ 39,000,000.0
Revolving Credit Facility | Line of Credit | Revolving credit facility, TAIFX plus the applicable bank rate, due December 2024 | Taiwan
Debt Instrument [Line Items]
Interest rate at end of period (as a percent)	3.35%		0.00%
Credit facility, borrowing capacity	$ 56,000,000.0
Minimum | Revolving Credit Facility | Line of Credit | $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore)
Debt Instrument [Line Items]
Interest rate (as a percent)	1.25%
Maximum | Revolving Credit Facility | Line of Credit | $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore)
Debt Instrument [Line Items]
Interest rate (as a percent)	1.75%
Fund Floating Rate | Subsidiary Term Loans | Term loan, fund floating rate plus 1.60%, due June 2020 | Korea
Debt Instrument [Line Items]
Interest rate spread (as a percent)	1.60%
London Interbank Offered Rate (LIBOR) | Subsidiary Term Loans | Term loan, LIBOR plus 2.56%, due December 2023 | Korea
Debt Instrument [Line Items]
Interest rate spread (as a percent)	2.56%
London Interbank Offered Rate (LIBOR) | Subsidiary Term Loans | Term loan, LIBOR plus 1.80% due December 2019 | China
Debt Instrument [Line Items]
Interest rate spread (as a percent)	1.80%
London Interbank Offered Rate (LIBOR) | Subsidiary Term Loans | Term Loan, LIBOR plus 1.60% Due March 2022 | China
Debt Instrument [Line Items]
Interest rate spread (as a percent)	1.60%
London Interbank Offered Rate (LIBOR) | Subsidiary Term Loans | Term Loan, LIBOR plus 1.40% Due March 2022 | China
Debt Instrument [Line Items]
Interest rate spread (as a percent)	1.40%