Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Jan. 01, 2018
Product Information [Line Items]
Operating lease, right-of-use asset	$ 57,771
Current operating lease liabilities	12,051
Noncurrent operating lease liabilities	$ 54,258
Effect of adopting accounting principle in period of adoption		$ 4,646	$ (3,076)
ASC 842
Product Information [Line Items]
Operating lease, right-of-use asset		59,400
Current operating lease liabilities		11,000
Noncurrent operating lease liabilities		57,300
Accumulated Deficit
Product Information [Line Items]
Effect of adopting accounting principle in period of adoption		4,646	$ (3,076)
Accumulated Deficit | ASC 842
Product Information [Line Items]
Effect of adopting accounting principle in period of adoption		$ 4,600