Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 8,423	$ 8,641	$ 0
Operating lease liabilities	$ 12,767
Topic 842
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		8,641
Operating lease liabilities		$ 12,800