Recent Accounting Standards - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax expense	$ 200	$ 200
Selling, general and administrative expenses		$ 164,046	$ 161,651	$ 139,272
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Selling, general and administrative expenses			$ (1,600)	$ (3,000)
Minimum | Subsequent Event | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset					$ 9,000
Operating lease, liability					9,000
Maximum | Subsequent Event | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset					11,000
Operating lease, liability					$ 11,000