Accounting Changes - Additional Information (Detail) - Accounting Standards Update 2016-13 [Member] - USD ($) $ in Billions		3 Months Ended	6 Months Ended
	Jan. 01, 2020	Jun. 30, 2020	Jun. 30, 2020
Increase in allowance for credit losses due to new accounting standard	$ 1.5
Decrease in retained earnings due to new accounting standard	$ 1.1
Increase in the allowance for credit losses due to deteriorating economic conditions		$ 1.3	$ 1.9