Leases - Adoption Effect of the Derecognition of Build-to-Suit Lease Assets and Recognition of Operating Lease Right-of-Use Assets and Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, net	$ 19,735
Property, plant and equipment, net			$ 44,219
Other accrued liabilities	19,196		15,726
Build-to-suit lease financing obligation			28,510
Operating lease right-of-use assets	22,160
Operating lease liabilities	9,115
Operating lease liabilities, noncurrent	16,162
Accumulated deficit	(372,826)		(302,695)
San Francisco Office Lease
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, net	814
Property, plant and equipment, net			28,101
Other accrued liabilities	0		552
Build-to-suit lease financing obligation			28,510
Operating lease right-of-use assets	5,953
Operating lease liabilities	5,580
Operating lease liabilities, noncurrent	1,446
Accumulated deficit	$ 135		$ 0
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 25,700
ASU 2016-02 | San Francisco Office Lease
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, net		(26,676)
Other accrued liabilities		(552)
Build-to-suit lease financing obligation		(28,510)
Operating lease right-of-use assets		10,130
Operating lease liabilities		5,167
Operating lease liabilities, noncurrent		7,026
Accumulated deficit		$ 135