Goodwill and Intangible Assets - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) acquisition	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Number of acquisitions resulting in goodwill | acquisition	4
Goodwill impairment loss | $	$ 0		$ 0
Number of acquisitions resulting in intangible assets | acquisition	3
Intangible asset amortization | $	$ 69,000	$ 60,000