Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment					$ 0
Amortization	$ 1,500,000	$ 1,500,000	$ 4,500,000	$ 4,700,000