Variable Interest Entities - Variable Interest Entities Information (Detail) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
LIHTC Funds [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Carrying Amount of Assets, Consolidated VIEs	$ 1	$ 1	$ 1
Variable Interest Entity, Carrying Amount of Liabilities, Consolidated VIEs	1	2	1
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIEs	26	55	55
Variable Interest Entity, Carrying Amount of Liabilities, Unconsolidated VIEs	14	36	36
LIHTC Investments, KCDC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIEs	834	775	764
Variable Interest Entity, Carrying Amount of Liabilities, Unconsolidated VIEs	271	263	258
Maximum Exposure to Loss, Unconsolidated VIEs	543	498	507
LIHTC Investments, KAHC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIEs	260	470	470
Variable Interest Entity, Carrying Amount of Liabilities, Unconsolidated VIEs	231	462	462
Maximum Exposure to Loss, Unconsolidated VIEs	$ 14	$ 9	$ 14