CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Cash flows from operating activities
Net income	$ 30,330		$ 16,845
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,468		3,496
Stock-based compensation	2,169		2,507
Amortization of debt discount and issuance costs	2,092		687
Loss on extinguishment of debt	3,137		0
Amortization of premium (discount) on short-term investments	(100)		17
Amortization of lease guarantee	(81)		(81)
Changes in operating assets and liabilities:
Receivables from collaborative arrangements	14,705		3,120
Prepaid expenses and other current assets	(196)		(114)
Accounts payable	(535)		2,176
Accrued personnel-related expenses and other accrued liabilities	(1,702)		752
Accrued interest payable	(3,375)		(1,428)
Other long-term liabilities	2		5
Deferred revenue	0		(221)
Net cash provided by operating activities	49,914		27,761
Cash flows from investing activities
Maturities of marketable securities	31,875		26,387
Purchases of marketable securities	(5,362)		(3,992)
Net cash provided by investing activities	26,513		22,395
Cash flows from financing activities
Repurchase of shares to satisfy tax withholding	(2,611)		(553)
Payments of principal on senior secured term loans	(120,000)		0
Payments of cash dividends to stockholders	(38)		(67)
Proceeds from issuances of common stock, net	114		8
Payment of principal on non-recourse notes due 2029	0		(7,752)
Distributions to noncontrolling interest	(90)		0
Net cash used in financing activities	(122,625)		(8,364)
Net (decrease) increase in cash and cash equivalents	(46,198)		41,792
Cash and cash equivalents at beginning of period	73,336	[1]	118,016
Cash and cash equivalents at end of period	27,138		159,808
Supplemental disclosure of cash flow information
Cash paid for interest	$ 8,941		$ 13,522

[1] *Condensed consolidated balance sheet as of December 31, 2017 has been derived from audited consolidated financial statements.