Goodwill and Intangible Assets - Narrative (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 01, 2013
Business Acquisition [Line Items]
Goodwill		$ 33,899,000	$ 33,899,000	$ 38,634,000
Other identifiable intangible assets		8,082,000
Identified intangible assets with indefinite useful life		3,721,000	3,721,000
Impairment of goodwill	$ 4,700,000	0	$ 4,735,000	$ 0
Impairment of intangible assets		0
HCN
Business Acquisition [Line Items]
Goodwill					$ 38,600,000
Other identifiable intangible assets					8,100,000
Identified intangible assets with indefinite useful life					3,700,000
Identified intangible assets with finite useful life					$ 4,400,000
Fair value of goodwill		33,900,000
Impairment of goodwill		$ 4,700,000