UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 217,957	$ 165,546
Restricted cash	761	0
Equity securities at fair value	387,120	109,103
Equity securities without readily determinable fair value	5,816	143,257
Investment securities - equity method investments	31,840	30,673
Investment at fair value	0	2,752
Accounts receivable	412	506
Other receivable (Note 3)	21,539	0
Prepaid expenses and other current assets	3,986	5,832
Total current assets	669,431	457,669
Long-term restricted cash	35,424	35,000
Patents, net of accumulated amortization	39,826	16,912
Leased right-of-use assets	671	951
Other non-current assets	4,482	4,988
Total assets	749,834	515,520
Current liabilities:
Accounts payable	2,196	1,019
Accrued expenses and other current liabilities	5,586	3,707
Accrued compensation	4,019	2,265
Royalties and contingent legal fees payable	1,793	2,162
Accrued patent investment costs	8,000	0
Senior Secured Notes Payable	182,855	115,663
Total current liabilities	204,449	124,816
Series A warrant liabilities	18,527	6,640
Series A embedded derivative liabilities	41,411	26,728
Series B warrant liabilities	229,637	52,341
Long-term lease liabilities	671	951
Other long-term liabilities	5,591	591
Total liabilities	500,286	212,067
Commitments and contingencies
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 September 30, 2021 and December 31, 2020; aggregate liquidation preference of $35,000 as of September 30, 2021 and December 31, 2020	13,686	10,924
Stockholders' equity:
Common stock, par value $0.001 per share; 300,000,000 shares authorized; 49,591,852 and 49,279,453 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively	50	49
Treasury stock, at cost, 4,604,365 shares as of September 30, 2021 and December 31, 2020	(43,270)	(43,270)
Additional paid-in capital	649,349	651,416
Accumulated deficit	(382,215)	(326,708)
Total Acacia Research Corporation stockholders' equity	223,914	281,487
Noncontrolling interests	11,948	11,042
Total stockholders' equity	235,862	292,529
Total liabilities, redeemable convertible preferred stock, and stockholders' equity	$ 749,834	$ 515,520