Remaining Maturity of Securities Available for Sale (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Available for Sale - Amortized Cost
Due in One Year or Less	$ 7,880.8	$ 9,335.0
Due After One Year Through Five Years	21,094.8	17,808.8
Due After Five Years Through Ten Years	5,759.1	4,036.5
Due After Ten Years	897.2	1,187.5
Total	35,631.9	32,367.8
Available for Sale - Fair Value
Due in One Year or Less	7,876.6	9,332.6
Due After One Year Through Five Years	21,058.7	17,777.0
Due After Five Years Through Ten Years	5,753.6	4,023.1
Due After Ten Years	890.9	1,185.2
Total	$ 35,579.8	$ 32,317.9