Basis of Presentation and Significant Accounting Policies - Summary of Estimated Useful Lives Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	7 years
Buildings [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	25 years
Buildings [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	40 years
Furniture and Fixtures [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	5 years
Furniture and Fixtures [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	10 years
Capitalized Software [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	2 years
Capitalized Software [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	7 years
Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	3 years
Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	7 years