Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 165,546	$ 57,359
Trading securities - debt	0	93,843
Trading securities - equity	109,103	17,140
Investment securities - private equity	143,257	0
Investment securities - equity method investments	30,673	0
Investment at fair value (6)	2,752	1,500
Accounts receivable	506	511
Prepaid expenses and other current assets	5,832	2,912
Total current assets	457,669	173,265
Long-term restricted cash	35,000	35,000
Patents, net of accumulated amortization	16,912	7,814
Leased right-of-use assets	951	1,264
Other non-current assets	4,988	818
Total assets	515,520	218,161
Current liabilities:
Accounts payable	1,019	1,765
Accrued expenses and other current liabilities	3,707	7,265
Accrued compensation	2,265	507
Royalties and contingent legal fees payable	2,162	2,178
Senior Secured Notes Payable - short-term	115,663	0
Total current liabilities	124,816	11,715
Series A warrant liabilities	6,640	3,568
Series A embedded derivative liabilities	26,728	17,974
Series B warrant liabilities	52,341	0
Long-term lease liabilities	951	1,264
Other long-term liabilities	591	593
Total liabilities	212,067	35,114
Commitments and contingencies (Note 10)
Series A redeemable convertible preferred stock, par value $0.001 per share; stated value $100 per share; 350,000 shares authorized, issued and outstanding as of December 31, 2020 and December 31, 2019, respectively; aggregate liquidation preference of $35,000 as of December 31, 2020 and December 31, 2019, respectively	10,924	8,089
Stockholders' equity:
Preferred stock, par value $0.001 per share; 10,000,000 shares authorized; no shares issued or outstanding	0	0
Common stock, par value $0.001 per share; 300,000,000 shares authorized; 49,279,453 and 50,370,987 shares issued and outstanding as of December 31, 2020 and December 31, 2019, respectively	49	50
Treasury stock, at cost, 4,604,365 and 2,919,828 shares as of December 31, 2020 and December 31, 2019, respectively	(43,270)	(39,272)
Additional paid-in capital	651,416	652,003
Accumulated deficit	(326,708)	(439,656)
Total Acacia Research Corporation stockholders' equity	281,487	173,125
Noncontrolling interests	11,042	1,833
Total stockholders' equity	292,529	174,958
Total liabilities, redeemable convertible preferred stock, and stockholders' equity	$ 515,520	$ 218,161