Intangible Assets - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2,400,000	$ 200,000	$ 0
Amortization expense for 2018	2,200,000
Amortization expense for 2019	2,200,000
Amortization expense for 2020	2,100,000
Amortization expense for 2021	2,100,000
Amortization expense for 2022	$ 2,100,000