XML 146 R130.htm IDEA: XBRL DOCUMENT v3.8.0.1
Retirement Benefit Plans - Summary of Key Assumptions Used for the Actuarial Valuations (Detail)
Dec. 31, 2017
Dec. 31, 2016
Bottom of range [member]    
Disclosure of defined benefit plans [line items]    
Discount rates 0.06% 0.06%
Expected rates of salary increase 2.00% 2.00%
Top of range [member]    
Disclosure of defined benefit plans [line items]    
Discount rates 3.85% 3.58%
Expected rates of salary increase 4.42% 4.42%