Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Schedule of Estimated Useful Life of Assets Used to Compute Depreciation Using the Straight-Line Method (Detail)

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Summary of Significant Accounting Policies - Schedule of Estimated Useful Life of Assets Used to Compute Depreciation Using the Straight-Line Method (Detail)
3 Months Ended
Mar. 31, 2018
Buildings and Other Improvements [Member] | Minimum [Member]  
Property, Plant and Equipment [Line Items]  
Estimated useful lives of assets 10 years
Buildings and Other Improvements [Member] | Maximum [Member]  
Property, Plant and Equipment [Line Items]  
Estimated useful lives of assets 20 years
Leasehold Improvements [Member]  
Property, Plant and Equipment [Line Items]  
Estimated useful lives of assets Remaining lease period
Office Furniture and Equipment [Member] | Minimum [Member]  
Property, Plant and Equipment [Line Items]  
Estimated useful lives of assets 5 years
Office Furniture and Equipment [Member] | Maximum [Member]  
Property, Plant and Equipment [Line Items]  
Estimated useful lives of assets 7 years
Computer Equipment and Software [Member] | Minimum [Member]  
Property, Plant and Equipment [Line Items]  
Estimated useful lives of assets 3 years
Computer Equipment and Software [Member] | Maximum [Member]  
Property, Plant and Equipment [Line Items]  
Estimated useful lives of assets 5 years