Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Sep. 30, 2011
Tax Credit Carryforward [Line Items]
NOL allocated amount		$ 3,650
Afg [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount	$ 1,251
Minimum [Member]
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2029
Maximum [Member]
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2040