Income Taxes - Additional Information (Details 5) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Deferred tax assets, operating loss carryforwards	$ 4,724,000	$ 4,647,000
Credit carry-forwards	15,964,000	16,909,000
Deferred tax asset valuation allowance	8,011,000	8,274,000
Foreign tax credit carry-forwards	5,785,000
Research and development credits	7,495,000
Implementation of ASU 2018-02		0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		18,001,000
Foreign income tax expense	10,666,000	12,538,000	$ 7,150,000
Unrecognized tax benefits	5,016,000
Accrued for interest and penalties related to uncertain income tax	$ 707,000	2,515,000
Minimum [Member]
Income Taxes
Open Tax Year	2008
Maximum
Income Taxes
Open Tax Year	2018
U.S. Federal Tax and Jobs Act Estimate
Income Taxes
Deferred Federal, State and Local, Tax Expense (Benefit)	$ 241,000	6,267,000
Tax Adjustments, Settlements, and Unusual Provisions	589,000	$ 11,734,000
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 348,000
Foreign Tax Credit Carryforward | Minimum [Member]
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2023
Foreign Tax Credit Carryforward | Maximum
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2029
Research Tax Credit Carryforward [Member] | Minimum [Member]
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2021
Research Tax Credit Carryforward [Member] | Maximum
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2039
Operating Loss Carryforward [Member] | Minimum [Member]
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2021
Operating Loss Carryforward [Member] | Maximum
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2039