Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income taxes

Income (loss) from operations before income taxes

	Year Ended December 31,
	2015		2014		2013
U.S.	$	110,560	$	(48,506)	$	(82,848)
Non-U.S.		(103,004)		(41)		—
Income (loss) before income taxes	$	7,556	$	(48,547)	$	(82,848)

Schedule of reconciliation of income taxes at the U.S. federal statutory rate to the provision for income taxes

	Year Ended December 31,
	2015		2014		2013
Provision (benefit) at U.S. federal statutory rate	$	2,645	$	(16,992)	$	(28,997)
Unbenefitted net operating losses and tax credits		(29,424)		13,432		18,215
Non-deductible amortization of debt discount		1,087		2,294		6,645
Non-deductible interest expense		122		1		747
Non-deductible debt exchange expense and loss on repurchase of senior notes		—		—		7,985
Deferred tax impact of law change		—		—		(5,549)
Foreign tax rate differential		21,443		—		—
Non-deductible officer compensation		4,696		830		976
Other		456		369		277
Provision (benefit) for income taxes	$	1,025	$	(66)	$	299

Schedule of significant components of deferred tax assets and liabilities

	December 31,
	2015		2014
Deferred tax assets:
Federal and state net operating loss carry forwards	$	329,984	$	504,267
Federal and state research credits		201,151		165,352
Capitalized research and development		13,017		2,475
Deferred revenue and accruals		11,212		15,799
Non-cash compensation		39,034		31,248
Deferred financing obligation		20,328		20,383
Other		3,125		8,306
Total gross deferred tax assets		617,851		747,830
Less valuation allowance for deferred tax assets		(542,936)		(669,168)
Net deferred tax assets	$	74,915	$	78,662
Deferred tax liabilities:
Property and equipment	$	(25,787)	$	(19,925)
Equity component of 2018 Notes and 2020 Notes		(49,128)		(58,737)
Total gross deferred tax liabilities		(74,915)		(78,662)
Net deferred income taxes	$	—	$	—

Unrecognized tax benefits

	December 31,
	2015
Balance at beginning of period	$	—
Additions based on tax positions related to the current year		836
Additions for tax positions of prior years		—
Balance at end of period	$	836