Description of Business and Summary of Significant Accounting Policies - Estimated Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2017
Buildings [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	40 years
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	20 years
Furniture, fixtures and equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	5 years
Furniture, fixtures and equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	8 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	The shorter of the lease term or useful life