CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016
Cash flows from operating activities
Net income	$ 75,758		$ 34,065
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,487		10,458
Stock-based compensation	7,406		6,423
Amortization of debt discount and issuance costs	2,953		2,138
Loss (gain) on extinguishment of debt	7,256		(1,752)
Amortization of discount on short-term investments	(6)		(8)
Amortization of lease guarantee	(243)		(108)
Interest added to the principal balance of the non-recourse term notes due 2029	0		855
Realized gain on sale of marketable securities, net	0		(1)
Changes in operating assets and liabilities:
Receivables from collaborative arrangements	(5,031)		(10,393)
Prepaid expenses and other current assets	327		280
Other assets	0		(22)
Accounts payable	501		(290)
Accrued personnel-related expenses and other accrued liabilities	(606)		220
Accrued interest payable	(4,262)		(1,305)
Other long-term liabilities	13		2
Deferred revenue	(663)		(664)
Net cash provided by operating activities	93,890		39,898
Cash flows from investing activities
Maturities of marketable securities	44,387		52,101
Purchases of marketable securities	(41,743)		(82,746)
Sales of marketable securities	0		2,995
Purchases of property and equipment	0		(250)
Net cash provided by (used in) investing activities	2,644		(27,900)
Cash flows from financing activities
Proceeds from senior secured term loans	250,000		0
Proceeds from issuance of convertible senior notes due 2025	192,500		0
Payments of debt issuance costs and debt discount	(12,803)		0
Payment of principal on non-recourse notes due 2029	(487,189)		(3,277)
Repurchase of shares to satisfy tax withholding	(1,183)		(884)
Payments of cash dividends to stockholders	(146)		(895)
Proceeds from issuances of common stock, net	188		341
Repurchase of common stock	(17,500)		(65,565)
Repurchase of convertible subordinated notes due 2023	0		(8,095)
Proceeds from capped-call options	0		391
Net cash used in financing activities	(76,133)		(77,984)
Net increase (decrease) in cash and cash equivalents	20,401		(65,986)
Cash and cash equivalents at beginning of period	118,016	[1]	159,180
Cash and cash equivalents at end of period	138,417		93,194
Supplemental disclosure of cash flow information
Cash paid for interest	$ 36,556		$ 37,729

[1] Condensed consolidated balance sheet as of December 31, 2016 has been derived from audited consolidated financial statements.