Remaining Maturity of Securities Available for Sale (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Available for Sale - Amortized Cost
Due in One Year or Less	$ 8,619.5
Due After One Year Through Five Years	16,807.1
Due After Five Years Through Ten Years	3,045.0
Due After Ten Years	1,147.3
Total	29,618.9
Held to Maturity - Amortized Cost
Due in One Year or Less	1,864.9
Due After One Year Through Five Years	2,348.2
Due After Five Years Through Ten Years	22.1
Due After Ten Years	35.4
Total	4,270.6	2,325.8
Available for Sale - Fair Value
Due in One Year or Less	8,629.4
Due After One Year Through Five Years	16,861.6
Due After Five Years Through Ten Years	3,045.5
Due After Ten Years	1,152.9
Total	29,689.4
Held to Maturity - Fair Value
Due in One Year or Less	1,868.3
Due After One Year Through Five Years	2,348.6
Due After Five Years Through Ten Years	23.3
Due After Ten Years	25.2
Fair Value	$ 4,265.4	$ 2,321.4