Goodwill and Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 1,501,000	$ 1,501,000
Additions	166,539,000	0
Impairments	(1,491,000)	0	$ 0
Goodwill, ending balance	$ 166,549,000	$ 1,501,000	$ 1,501,000