Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Schedule of Income Tax Expense

Income tax benefit (expense) for the periods presented consisted of the following:

	Years Ended December 31,
	2014			2013			2012
Current:
Federal	$	(19,476	)	$	(7	)	$	(7	)
State		(1,496	)		(108	)		—
Total current		(20,972	)		(115	)		(7	)
Deferred:
Federal		36,917			—			—
State		313			—			—
Total deferred		37,230			—			—
Total income tax benefit (expense)	$	16,258		$	(115	)	$	(7	)

Schedule of Reconciliation of Statutory Federal Income Tax Rate

A reconciliation of the statutory Federal income tax rate of 35% to the Company’s effective income tax rates is as follows:

	Years Ended December 31,
	2014			2013			2012
Federal tax provision at statutory rate		35.0	%		35.0	%		35.0	%
State taxes (net of Federal benefit)		0.4	%		1.4	%		10.8	%
Orphan drug credit		—			—			0.3	%
Stock-based compensation		0.1	%		(0.2	%)		1.5	%
Non-deductible officer compensation		0.1	%		(1.8	%)		(1.9	%)
Change in valuation allowance		(40.5	%)		(52.1	%)		(45.5	%)
Research and development credits		(1.5	%)		17.1	%		—
Other		0.2	%		0.3	%		(0.2	%)
Effective income tax rate		(6.2	%)		(0.3	%)		0.0	%

Schedule of Company's Deferred Tax Assets

Significant components of the Company’s deferred tax assets for Federal and state income taxes are follows:

	December 31,
	2014			2013
Deferred tax assets:
Deferred revenue	$	1,005		$	6,073
Net operating loss carryforward		9,100			80,620
Stock-based compensation		26,000			21,257
Tax credits		12,098			22,616
Intangible assets		5,259			—
Accruals and reserves		15,247			10,544
Total deferred tax assets		68,709			141,110
Less: valuation allowance		(16,023	)		(120,807	)
Total net deferred tax assets		52,686			20,303
Deferred tax liabilities
Depreciation		(2,741	)		(2,674	)
Convertible Notes		(12,792	)		(17,629	)
Total deferred tax liabilities		(15,533	)		(20,303	)
Net deferred tax assets	$	37,153		$	—
Recorded as:
Net current deferred tax assets	$	21,987		$	5,541
Net non-current deferred tax assets		15,176			—
Net non-current deferred tax liabilities (included in “Other non-current liabilities”)		(10	)		(5,541	)
Net deferred tax assets	$	37,153		$	—

Schedule of Gross Unrecognized Tax Positions

The following table summarizes activity related to the Company’s gross unrecognized tax positions:

	December 31,
	2014			2013			2012
Balance as of beginning of year	$	5,955		$	4,602		$	3,936
Additions based on tax positions related to the current year		6,439			702			400
Additions based on tax position related to prior year		—			660			270
Decreases based on tax positions related to prior year		(27	)		(9	)		(4	)
Balance as of end of year	$	12,367		$	5,955		$	4,602