Allowance for Credit Losses - ECL Estimates (Details) - scenario	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2020	Jan. 01, 2020
Measurement of ECL Measurements [Line Items]
Number of forward-looking economic scenarios	4		3
Reasonable and supportable forecast period for consensus economic scenarios	2 years
Reversion period for average historical values	20 years
Reversion period for most assumption variables	3 years
GDP growth rate (percent)		9.00%
Forecast Period 2020 [Member] | Central Scenario [Member]
Measurement of ECL Measurements [Line Items]
Inflation (percent)			2.00%
Forecast Period 2020 [Member] | Upside Scenario [Member]
Measurement of ECL Measurements [Line Items]
GDP growth rate (percent)			4.00%
Forecast Period 2020 [Member] | Downside Scenario [Member]
Measurement of ECL Measurements [Line Items]
Policy interest rate (percent, less than)			0.50%