Summary of Significant Accounting Policies - New Accounting Standards (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract liabilities		$ 0	$ 0
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting standard, net of tax			179
Contract liabilities			200
Accounting Standards Update 2018-02 | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax to retained earnings	$ 168
Accounting Standards Update 2016-02 | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset	17,600
Operating lease, liability	$ 21,000
Retained Earnings | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting standard, net of tax			$ 179