XML 364 R122.htm IDEA: XBRL DOCUMENT v3.10.0.1
Tax - Summary of Unrecognised Deferred Tax Position (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Unrecognised deferred tax position [line items]    
Unrecognised deferred tax $ 163 $ 184
Gross carrying amount 989 1,002
Revenue losses [member]    
Unrecognised deferred tax position [line items]    
Gross carrying amount 448 452
Unrecognised deferred tax 67 76
Capital losses [member]    
Unrecognised deferred tax position [line items]    
Gross carrying amount 516 515
Unrecognised deferred tax 90 99
Total losses [member]    
Unrecognised deferred tax position [line items]    
Gross carrying amount 964 967
Unrecognised deferred tax 157 175
Other [member]    
Unrecognised deferred tax position [line items]    
Unrecognised deferred tax 6 9
Gross carrying amount $ 25 $ 35