Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Increase in valuation allowance	$ 162,500
Operating Loss Carryforwards [Line Items]
Decrease in accounts receivable	(5,032)	$ (8,948)	$ (11,686)
Decrease in deferred tax asset	(507,268)		$ (323,501)
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	981,800
Net operating losses that begin to expire in 2030	380,100
Net operating losses that will carry-forward indefinitely	601,700
Federal | Research and development
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	45,600
State
Operating Loss Carryforwards [Line Items]
Net operating losses	978,800
Net operating losses that begin to expire in 2030	978,800
State | Research and development
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	23,900
State | Federal Orphan Drug
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	1,500
State | Investment tax credit
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	$ 5,900
Accounting Standards Update 2014-09
Operating Loss Carryforwards [Line Items]
Cumulative-effect adjustment		27,984
Decrease in deferred revenue		30,700
Decrease in accounts receivable		2,700
Decrease in deferred tax asset		8,400
Accounting Standards Update 2014-09 | Accumulated Deficit
Operating Loss Carryforwards [Line Items]
Cumulative-effect adjustment		$ 27,984