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Operations and Summary of Significant Accounting Policies - Estimated Economic Lives of Property and Equipment (Detail)
12 Months Ended
Dec. 31, 2017
Property, Plant and Equipment [Line Items]  
Leasehold improvements Shorter of underlying lease term or asset life
Buildings [Member]  
Property, Plant and Equipment [Line Items]  
Useful Life 29 years
Minimum [Member] | Furniture and fixtures [Member]  
Property, Plant and Equipment [Line Items]  
Useful Life 2 years
Minimum [Member] | Equipment [Member]  
Property, Plant and Equipment [Line Items]  
Useful Life 3 years
Minimum [Member] | Software [Member]  
Property, Plant and Equipment [Line Items]  
Useful Life 3 years
Maximum [Member] | Furniture and fixtures [Member]  
Property, Plant and Equipment [Line Items]  
Useful Life 7 years
Maximum [Member] | Equipment [Member]  
Property, Plant and Equipment [Line Items]  
Useful Life 5 years
Maximum [Member] | Software [Member]  
Property, Plant and Equipment [Line Items]  
Useful Life 10 years