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Significant Accounting Policies - Disclosure of Estimated Useful Lives for Investment Properties (Detail)
12 Months Ended
Dec. 31, 2017
Bottom of range [member]  
Disclosure of detailed information about investment property [line items]  
Estimated useful lives, Investment Property 25 years
Top of range [member]  
Disclosure of detailed information about investment property [line items]  
Estimated useful lives, Investment Property 45 years