Income Taxes - Differences Between Statutory Income Tax Rate and Effective Income Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Increase (decrease) resulting from:
Tax at statutory rate	$ (331)	$ 182
Tax-exempt income from municipal bonds	(5)	(5)
Dividend received exclusion	(4)	(4)
Other	(10)	(1)
Total provision (benefit) for income taxes	$ (350)	$ 172
Increase (decrease) resulting from:
Tax at statutory rate	21.00%	21.00%
Tax-exempt income from municipal bonds	0.30%	(0.60%)
Dividend received exclusion	0.30%	(0.50%)
Other	0.60%	(0.10%)
Provision for income taxes	22.20%	19.80%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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