Accumulated Other Comprehensive Income (Loss) Changes During Period (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income	$ (1.1)	$ 69.3
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	2.1	32.0
Tax Effect	(0.8)	(12.0)
Other Comprehensive Income	1.3	20.0
Net Unrealized Gains (Losses) on Securities Available for Sale | Noncredit-Related Unrealized Losses on Securities OTTI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	2.1	5.8
Tax Effect	(0.8)	(2.2)
Other Comprehensive Income	1.3	3.6
Net Unrealized Gains (Losses) on Securities Available for Sale | Other Unrealized Gains (Losses) on Securities Available-for-Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	0.2	29.6
Tax Effect	(0.1)	(11.1)
Other Comprehensive Income	0.1	18.5
Net Unrealized Gains (Losses) on Securities Available for Sale | Reclassification Adjustment for (Gains) Losses Included in Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(0.2)	(3.4)
Tax Effect	0.1	1.3
Other Comprehensive Income	(0.1)	(2.1)
Net Unrealized Gains (Losses) on Cash Flow Hedge Designations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(7.4)	17.9
Tax Effect	2.2	(6.6)
Other Comprehensive Income	(5.2)	11.3
Net Unrealized Gains (Losses) on Cash Flow Hedge Designations | Reclassification Adjustment for (Gains) Losses Included in Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	1.8	(1.0)
Tax Effect	(0.7)	0.4
Other Comprehensive Income	1.1	(0.6)
Net Unrealized Gains (Losses) on Cash Flow Hedge Designations | Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(9.2)	18.9
Tax Effect	2.9	(7.0)
Other Comprehensive Income	(6.3)	11.9
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	26.4	(10.3)
Tax Effect	(30.6)	26.1
Other Comprehensive Income	(4.2)	15.8
Foreign Currency Translation Adjustments | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(56.4)	34.9
Tax Effect	0.5
Other Comprehensive Income	(55.9)	34.9
Foreign Currency Translation Adjustments | Net Investment Hedge Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	82.8	(45.2)
Tax Effect	(31.1)	26.1
Other Comprehensive Income	51.7	(19.1)
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	11.2	35.4
Tax Effect	(4.2)	(13.2)
Other Comprehensive Income	7.0	22.2
Net Pension and Other Postretirement Benefit Adjustments | Reclassification Adjustment for (Gains) Losses Included in Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	11.2	8.7
Tax Effect	(4.2)	(3.1)
Other Comprehensive Income	7.0	5.6
Net Pension and Other Postretirement Benefit Adjustments | Net Actuarial Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax		26.7
Tax Effect		(10.1)
Other Comprehensive Income		$ 16.6