Variable Interest Entities - Variable Interest Entities Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Total Assets	$ 248	$ 230
Total Liabilities	2	4
LIHTC Investments [Member]
Variable Interest Entity [Line Items]
Total Assets	5,932	6,003
Total Liabilities	2,569	2,943
Maximum Exposure to Loss	1,740	1,561
KCC Indirect Investments [Member]
Variable Interest Entity [Line Items]
Total Assets	19,659	26,817
Total Liabilities	376	292
Maximum Exposure to Loss	$ 122	$ 153