Variable Interest Entities - Variable Interest Entities Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Total Assets	$ 178	$ 176
Total Liabilities	4	1
LIHTC Investments [Member]
Variable Interest Entity [Line Items]
Total Assets	4,814	4,914
Total Liabilities	2,003	1,368
Maximum Exposure to Loss	1,465	$ 1,332
KCC Indirect Investments [Member]
Variable Interest Entity [Line Items]
Total Assets	32,755
Total Liabilities	201
Maximum Exposure to Loss	$ 195