Variable Interest Entities - Summary of Variable Interest Entities Information (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Variable Interest Entity [Line Items]
Total Assets	$ 280		$ 282
Total Liabilities	1		$ 1
LIHTC Investments [Member]
Variable Interest Entity [Line Items]
Total Assets	6,401	$ 6,405
Total Liabilities	2,534	2,526
Maximum Exposure to Loss	1,823	1,846
KCC Indirect Investments [Member]
Variable Interest Entity [Line Items]
Total Assets	12,221	12,954
Total Liabilities	182	205
Maximum Exposure to Loss	$ 84	$ 89