CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net income	$ 220,541	$ 177,177
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes	45,069	35,823
Depreciation and amortization	6,918	6,921
Stock-based compensation	921	810
Amortization of debt discount and issuance costs	4,472	4,110
Amortization of discount on short-term investments	0	(336)
Amortization of lease guarantee	0	(135)
Changes in fair values of equity and long-term investments, net	(99,046)	(68,613)
Other non-cash items	16	6
Changes in operating assets and liabilities:
Receivables from collaborative arrangements	(10,331)	(2,975)
Prepaid expenses and other current assets	906	317
Accounts payable	(36)	185
Accrued personnel-related expenses and other accrued liabilities	(709)	(15)
Net cash provided by operating activities	168,721	153,275
Cash flows from investing activities
Maturities of marketable securities	0	82,000
Purchases of marketable securities	0	(12,943)
Purchases of equity and long term investments	(46,373)	(60,000)
Distributions of equity and long-term investments	110,000	0
Purchases of property and equipment	0	(13)
Net cash provided by (used in) investing activities	63,627	9,044
Cash flows from financing activities
Repurchase of common stock	(394,149)	0
Distributions to noncontrolling interest	(41,446)	(27,962)
Repurchase of shares to satisfy tax withholding	(35)	(72)
Proceeds from issuances of common stock, net	60	422
Net proceeds from the issuance of variable interest entity's equity	0	344
Net cash used in financing activities	(435,570)	(27,268)
Net increase (decrease) in cash and cash equivalents	(203,222)	135,051
Cash and cash equivalents at beginning of period	246,487	278,096
Cash and cash equivalents at end of period	43,265	413,147
Supplemental disclosure of cash flow information
Cash paid for interest	$ 4,967	$ 4,967