Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Tax Contingency [Line Items]
Change in Company's estimates of the recoverability of its deferred tax assets	$ 0
Deferred income tax asset after valuation allowance	29,700		$ 29,700		$ 31,300
Gross deferred income tax asset	29,900		29,900		31,500
Valuation allowance	200		200		200
Provision for income taxes	3,030	$ 1,452	11,986	$ 9,540
Tax provision related to uncertain tax positions	700
Tax provision related to employee stock compensation plans	0
Impact of changes due to U.S. Tax Act					0
Cash held outside of North America	84,200		84,200		121,900
Withholding tax estimate on repatriation of funds	10,200		10,200		8,400
Republic of China [Member]
Income Tax Contingency [Line Items]
Cash held/undistributed earnings intended to be permanently reinvested	$ 63,500		$ 63,500		$ 54,700