CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 368,837	$ 293,814	$ 190,993
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes	76,432	60,420	41,875
Depreciation and amortization	13,832	13,840	13,874
Stock-based compensation	2,017	1,698	2,056
Amortization of debt discount and issuance costs	9,136	8,397	7,799
Loss on write-off of property and equipment	0	0	104
Loss on extinguishment of debt	0	0	216
Amortization of discount on short-term investments	0	(343)	(2,229)
Amortization of lease guarantee	0	(135)	(325)
Changes in fair values of equity and long-term investments, net	(89,309)	(50,277)	0
Other non-cash items	(259)	21	0
Changes in operating assets and liabilities:
Receivables from collaborative arrangements	(16,780)	(14,504)	3,859
Prepaid expenses and other current assets	203	(678)	(113)
Other assets	0	0	27
Accounts payable	(39)	56	(1)
Accrued personnel-related expenses and other accrued liabilities	(257)	804	(439)
Accrued interest payable	0	0	(112)
Other long-term liabilities	0	0	(126)
Net cash provided by operating activities	363,813	313,113	257,458
Cash flows from investing activities
Maturities of marketable securities	0	86,000	213,924
Purchases of marketable securities	0	(12,943)	(231,915)
Purchases of equity and long term investments	(66,278)	(87,981)	0
Purchases and sales of marketable securities and other investments managed by ISP Fund LP, net	(190,970)	(14,877)	0
Sale of equity investments managed by ISP FUND LP	21,440		0
Purchase and sale of other investments managed by ISP FUND LP	279,530		0
Purchases of property and equipment	0	(13)	(12)
Net cash provided by (used in) investing activities	43,722	(314,937)	(18,003)
Cash flows from financing activities
Repurchase of common stock	(394,149)	0	0
Distributions to noncontrolling interest	(59,457)	(30,474)	(10,553)
Repurchase of shares to satisfy tax withholding	(60)	(92)	(89)
Payments of principal on senior secured term loans	0	0	(13,750)
Payments of cash dividends to stockholders	0	0	(11)
Proceeds from issuances of common stock, net	1,169	436	627
Net proceeds from the issuance of variable interest entity's equity	0	345	0
Net cash used in financing activities	(452,497)	(29,785)	(23,776)
Net increase (decrease) in cash and cash equivalents	(44,962)	(31,609)	215,679
Cash and cash equivalents at beginning of period	246,487	278,096	62,417
Cash and cash equivalents at end of period	201,525	246,487	278,096
Supplemental disclosure of cash flow information
Cash paid for interest	$ 9,933	$ 9,933	$ 10,974