Background and Basis of Presentation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid	$ 7,886	$ 4,740	$ 4,740
Income taxes paid, including foreign withholding taxes	24,229	33,904	66,793
Non-cash investing and financing activities:
Dividend payable	10,746	11,627	12,156
Increases in noncontrolling interests	13,750	0	0
Non-cash acquisition of patents	22,500	0	32,500
Accrued capitalized patent costs and property and equipment	$ 1,619	$ (2,789)	$ 1