CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income	$ 109,695	$ 78,952
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes	19,736	15,932
Depreciation and amortization	3,460	3,463
Stock-based compensation	451	435
Amortization of debt discount and issuance costs	2,211	2,032
Amortization of discount on short-term investments	0	(272)
Amortization of lease guarantee	0	(81)
Changes in fair values of equity and long-term investments, net	(54,673)	(21,915)
Other non-cash items	8	0
Changes in operating assets and liabilities:
Receivables from collaborative arrangements	4,957	(2,707)
Prepaid expenses and other current assets	571	140
Accounts payable	(52)	112
Accrued personnel-related expenses and other accrued liabilities	227	(126)
Accrued interest payable	(2,484)	(2,484)
Net cash provided by operating activities	84,107	73,481
Cash flows from investing activities
Maturities of marketable securities	0	54,000
Purchases of marketable securities	0	(12,943)
Purchases of equity and long term investments	(26,394)	(25,000)
Purchases of property and equipment	0	(13)
Net cash provided by (used in) investing activities	(26,394)	16,044
Cash flows from financing activities
Repurchase of shares to satisfy tax withholding	(25)	(55)
Proceeds from issuances of common stock, net	0	225
Distributions to noncontrolling interest	(21,285)	(15,810)
Net cash used in financing activities	(21,310)	(15,640)
Net increase in cash and cash equivalents	36,403	73,885
Cash and cash equivalents at beginning of period	246,487	278,096
Cash and cash equivalents at end of period	282,890	351,981
Supplemental disclosure of cash flow information
Cash paid for interest	$ 4,967	$ 4,967