Variable Interest Entities - Summary of Variable Interest Entities Information (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Total Assets	$ 171,192	$ 144,988
Total Liabilities	153,650	127,950
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total Assets	300	282
Total Liabilities	1	1
Variable Interest Entity, Not Primary Beneficiary | LIHTC investments
Variable Interest Entity [Line Items]
Total Assets	6,300	6,405
Total Liabilities	2,534	2,526
Maximum Exposure to Loss	1,760	1,846
Variable Interest Entity, Not Primary Beneficiary | KCC indirect investments
Variable Interest Entity [Line Items]
Total Assets	9,930	12,954
Total Liabilities	177	205
Maximum Exposure to Loss	$ 74	$ 89