Condensed Statement of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
OPERATING ACTIVITIES:
Net Income	$ 811.8us-gaap_NetIncomeLoss	$ 731.3us-gaap_NetIncomeLoss	$ 687.3us-gaap_NetIncomeLoss
Adjustments to Reconcile Net Income to Net Cash Provided by (Used in) Operating Activities:
Change in Accrued Income Taxes	55.2	(31.5)	18.5
Other, net	86.1	176.9	16.6
Net Cash Provided by Operating Activities	936.0	839.3	814.4
INVESTING ACTIVITIES:
Change in Time Deposits with Banks	3,297.2	(782.1)	(2,107.1)
Purchases of Securities - Available for Sale	(12,668.0)	(8,168.0)	(19,546.4)
Proceeds from Sale, Maturity and Redemption of Securities - Available for Sale	11,476.6	8,456.4	21,183.3
Other, net	(157.4)	109.4	(161.2)
Net Cash (Used in) Provided by Investing Activities	(8,212.4)	(5,683.3)	1,627.6
FINANCING ACTIVITIES:
Change in Senior Notes and Long-Term Debt		750.0	500.0
Proceeds from Issuance of Preferred Stock - Series C	388.5
Treasury Stock Purchased	(480.7)	(309.7)	(162.4)
Net Proceeds from Stock Options	127.5	146.2	106.8
Cash Dividends Paid on Common Stock	(302.9)us-gaap_PaymentsOfDividendsCommonStock	(220.6)us-gaap_PaymentsOfDividendsCommonStock	(354.3)us-gaap_PaymentsOfDividendsCommonStock
Other, net	(222.4)	226.7
Net Cash Provided by (Used in) Financing Activities	7,073.7	4,388.3	(3,072.9)
Decrease in Cash and Due from Banks	(111.8)	(590.3)	(562.6)
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Cash and Due from Banks at End of Year	3,050.6us-gaap_CashAndDueFromBanks	3,162.4us-gaap_CashAndDueFromBanks	3,752.7us-gaap_CashAndDueFromBanks
Parent Company
OPERATING ACTIVITIES:
Net Income	811.8	731.3	687.3
Adjustments to Reconcile Net Income to Net Cash Provided by (Used in) Operating Activities:
Equity in Undistributed Net Income of Subsidiaries	(532.4)	131.0	(247.3)
Change in Prepaid Expenses	0.2	(1.1)	(0.9)
Change in Accrued Income Taxes	(30.7)	(18.1)	34.7
Other, net	56.1	102.6	(36.0)
Net Cash Provided by Operating Activities	305.0	945.7	437.8
INVESTING ACTIVITIES:
Change in Time Deposits with Banks		1,691.4	(422.2)
Purchases of Securities - Available for Sale			(0.4)
Proceeds from Sale, Maturity and Redemption of Securities - Available for Sale	2.9	0.2	94.3
Change in Capital Investments in Subsidiaries		(13.0)	0.3
Advances to Wholly-Owned Subsidiaries	(238.5)	(1,000.0)
Other, net	1.1	1.8
Net Cash (Used in) Provided by Investing Activities	(234.5)	680.4	(328.0)
FINANCING ACTIVITIES:
Change in Senior Notes and Long-Term Debt	(500.0)	317.9	300.0
Proceeds from Issuance of Preferred Stock - Series C	388.5
Treasury Stock Purchased	(480.7)	(309.7)	(162.4)
Net Proceeds from Stock Options	127.5	146.2	106.8
Cash Dividends Paid on Common Stock	(302.9)	(220.6)	(354.3)
Other, net	0.1		0.1
Net Cash Provided by (Used in) Financing Activities	(767.5)	(66.2)	(109.8)
Decrease in Cash and Due from Banks	(697.0)	1,559.9
Cash and Due from Banks at Beginning of Year	1,566.4	6.5	6.5
Cash and Due from Banks at End of Year	$ 869.4	$ 1,566.4	$ 6.5

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Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

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