Variable Interest Entities - Summary of Variable Interest Entities Information (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Total Assets	$ 170,540	$ 144,988
Total Liabilities	152,818	127,950
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total Assets	335	282
Total Liabilities	1	1
Variable Interest Entity, Not Primary Beneficiary | LIHTC investments
Variable Interest Entity [Line Items]
Total Assets	6,693	6,405
Total Liabilities	2,547	2,526
Maximum Exposure to Loss	1,820	1,846
Variable Interest Entity, Not Primary Beneficiary | KCC indirect investments
Variable Interest Entity [Line Items]
Total Assets	11,225	12,954
Total Liabilities	173	205
Maximum Exposure to Loss	$ 78	$ 89