Revenue Recognition - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 102,161	$ 72,523	$ 75,609	$ 68,631	$ 75,326	$ 75,079	$ 69,555	$ 87,444	$ 318,924	$ 307,404	$ 532,938
Total Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									307,431	302,060
Variable Patent Royalty Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									30,428	36,384
Fixed-Fee Royalty Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									257,221	239,347
Current Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									287,649	275,731
Non-Current Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									19,782	26,329
Current Technology Solutions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									10,518	4,594
Patent Sales
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									$ 975	750
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										382,113	532,938
Calculated under Revenue Guidance in Effect before Topic 606 | Total Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										371,862	512,358
Calculated under Revenue Guidance in Effect before Topic 606 | Variable Patent Royalty Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										36,845	47,840
Calculated under Revenue Guidance in Effect before Topic 606 | Fixed-Fee Royalty Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										318,688	301,628
Calculated under Revenue Guidance in Effect before Topic 606 | Current Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										355,533	349,468
Calculated under Revenue Guidance in Effect before Topic 606 | Non-Current Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										16,329	162,890
Calculated under Revenue Guidance in Effect before Topic 606 | Current Technology Solutions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										9,501	20,580
Calculated under Revenue Guidance in Effect before Topic 606 | Patent Sales
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										$ 750	$ 0