Revenue - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 104,498	$ 75,609	$ 180,708	$ 144,240
Increase/(decrease) in disaggregated revenue	$ 28,889		$ 36,468
Percentage increase/(decrease) in disaggregated revenue	38.00%		25.00%
Variable patent royalty revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 4,597	8,594	$ 10,543	17,874
Increase/(decrease) in disaggregated revenue	$ (3,997)		$ (7,331)
Percentage increase/(decrease) in disaggregated revenue	(47.00%)		(41.00%)
Fixed-fee royalty revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 77,338	63,736	$ 143,685	126,609
Increase/(decrease) in disaggregated revenue	$ 13,602		$ 17,076
Percentage increase/(decrease) in disaggregated revenue	21.00%		13.00%
Current patent royalties
Disaggregation of Revenue [Line Items]
Revenue	$ 81,935	72,330	$ 154,228	144,483
Increase/(decrease) in disaggregated revenue	$ 9,605		$ 9,745
Percentage increase/(decrease) in disaggregated revenue	13.00%		7.00%
Non-current patent royalties
Disaggregation of Revenue [Line Items]
Revenue	$ 19,249	1,237	$ 19,954	(4,538)
Increase/(decrease) in disaggregated revenue	$ 18,012		$ 24,492
Percentage increase/(decrease) in disaggregated revenue	1456.00%		540.00%
Total patent royalties
Disaggregation of Revenue [Line Items]
Revenue	$ 101,184	73,567	$ 174,182	139,945
Increase/(decrease) in disaggregated revenue	$ 27,617		$ 34,237
Percentage increase/(decrease) in disaggregated revenue	38.00%		24.00%
Current technology solutions revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 3,314	2,042	$ 6,526	4,070
Increase/(decrease) in disaggregated revenue	$ 1,272		$ 2,456
Percentage increase/(decrease) in disaggregated revenue	62.00%		60.00%
Patent sales
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 0	$ 225
Increase/(decrease) in disaggregated revenue	$ 0		$ (225)
Percentage increase/(decrease) in disaggregated revenue	0.00%		0.00%