Fair Value Measurements - Summary of Fair Values of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - CAD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	$ 47,368	$ 41,278
Financial liabilities	23,595	20,570
Recurring Fair Value Measurement
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	2,187	1,550
Financial liabilities	197	93
Recurring Fair Value Measurement | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	935	465
Financial liabilities	0	0
Recurring Fair Value Measurement | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	1,204	1,045
Financial liabilities	197	93
Recurring Fair Value Measurement | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	48	40
Financial liabilities	0	0
Recurring Fair Value Measurement | Cash equivalents
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	790	313
Recurring Fair Value Measurement | Cash equivalents | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	790	313
Recurring Fair Value Measurement | Cash equivalents | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Cash equivalents | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Marketable equity securities
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	88	102
Recurring Fair Value Measurement | Marketable equity securities | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	41	64
Recurring Fair Value Measurement | Marketable equity securities | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Marketable equity securities | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	47	38
Recurring Fair Value Measurement | Debt securities
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	105	90
Recurring Fair Value Measurement | Debt securities | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	104	88
Recurring Fair Value Measurement | Debt securities | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Debt securities | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	1	2
Recurring Fair Value Measurement | Settlement receivables
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	1,126	949
Recurring Fair Value Measurement | Settlement receivables | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Settlement receivables | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	1,126	949
Recurring Fair Value Measurement | Settlement receivables | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	78	96
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	78	96
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial assets	0	0
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	158	32
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	0	0
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	158	32
Recurring Fair Value Measurement | Derivative instruments and embedded derivatives | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	0	0
Recurring Fair Value Measurement | Settlement payables
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	39	61
Recurring Fair Value Measurement | Settlement payables | Level 1
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	0	0
Recurring Fair Value Measurement | Settlement payables | Level 2
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	39	61
Recurring Fair Value Measurement | Settlement payables | Level 3
Disclosure of fair value measurement of liabilities and assets [line items]
Financial liabilities	$ 0	$ 0