Debt (Narrative) (Details) ¥ in Billions	1 Months Ended		3 Months Ended	12 Months Ended
	Aug. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jul. 31, 2018 JPY (¥)	Nov. 30, 2015 USD ($)	May 31, 2015 USD ($)
Debt Instrument [Line Items]
Total debt				$ 1,334,129,000	$ 1,365,533,000
Debt Instruments [Abstract]
Proceeds from revolving credit facilities				0	75,000,000	$ 125,000,000
Senior notes | 6.625% Senior notes, due June 2021
Debt Instrument [Line Items]
Total debt	$ 200,000,000			$ 0
Debt Instruments [Abstract]
Interest rate (as a percent)	6.625%			6.625%
Redemption price (as a percent)		100.00%
Write off of deferred debt issuance cost	$ 800,000
Line of Credit | Revolving Credit Facility | $75 million revolving credit facility, foreign currency funding-linked base rate plus 1.60%, due September 2018
Debt Instruments [Abstract]
Credit facility, borrowing capacity								$ 75,000,000.0
Line of Credit | Revolving Credit Facility | $75 million revolving credit facility, foreign currency funding-linked base rate plus 1.60%, due June 2018
Debt Instruments [Abstract]
Credit facility, borrowing capacity			$ 75,000,000
Line of Credit | Revolving Credit Facility | $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore)
Debt Instrument [Line Items]
Total debt				$ 0	0
Debt Instruments [Abstract]
Credit facility, borrowing capacity				250,000,000
Remaining borrowing capacity				250,000,000
Write off of deferred debt issuance cost		$ 400,000
Line of Credit | Revolving Credit Facility | Korea | $75 million revolving credit facility, foreign currency funding-linked base rate plus 1.60%, due September 2018
Debt Instrument [Line Items]
Total debt				0	75,000,000
Debt Instruments [Abstract]
Credit facility, borrowing capacity				75,000,000
Line of Credit | Revolving Credit Facility | Korea | $30 million revolving credit facility, LIBOR plus the applicable bank rate, due October 2019
Debt Instrument [Line Items]
Total debt				0	0
Debt Instruments [Abstract]
Credit facility, borrowing capacity				30,000,000			$ 30,000,000
Remaining borrowing capacity				30,000,000
Line of Credit | Revolving Credit Facility | Taiwan | Revolving credit facility, TAIFX plus a bank-determined spread, due November 2020 (Taiwan)
Debt Instrument [Line Items]
Total debt				20,000,000	20,000,000
Debt Instruments [Abstract]
Credit facility, borrowing capacity										$ 39,000,000
Remaining borrowing capacity				19,000,000
Subsidiary Term Loans | Korea | Term loan, LIBOR plus 2.34%, due September 2021
Debt Instruments [Abstract]
Amount of debt agreement								$ 75,000,000
Subsidiary Term Loans | Korea | Term loan, fund floating rate plus 1.60%, due June 2020
Debt Instrument [Line Items]
Total debt				125,000,000	86,000,000
Debt Instruments [Abstract]
Credit facility, borrowing capacity											$ 150,000,000
Proceeds from revolving credit facilities			$ 64,000,000
Subsidiary Term Loans | Korea | Term loan, LIBOR plus 2.56%, due December 2023
Debt Instrument [Line Items]
Total debt				200,000,000	0
Debt Instruments [Abstract]
Amount of debt agreement				200,000,000
Subsidiary Term Loans | Korea | Term loan, applicable bank rate plus 1.98%, due December 2028
Debt Instrument [Line Items]
Total debt				24,000,000	0
Debt Instruments [Abstract]
Credit facility, borrowing capacity				90,000,000
Remaining borrowing capacity				66,000,000
Subsidiary Term Loans | Japan | Term loan, fixed rate at 1.30%, due July 2023
Debt Instrument [Line Items]
Total debt				$ 225,180,000	0
Debt Instruments [Abstract]
Amount of debt agreement		$ 233,200,000							¥ 26.0
Interest rate (as a percent)				1.30%
Subsidiary Term Loans | Japan | Short-term term loans, variable rates
Debt Instrument [Line Items]
Total debt				$ 8,232,000	$ 30,455,000
Debt Instruments [Abstract]
Remaining borrowing capacity				$ 4,600,000