Accumulated Other Comprehensive Income (Loss) Changes During Period (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss)	$ 53.3	$ 8.2
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	86.7	7.3
Tax Effect	(32.6)	(2.8)
Other Comprehensive Income (Loss)	54.1	4.5
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		1.5
Tax Effect		(0.6)
Other Comprehensive Income (Loss)		0.9
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	86.8	5.7
Tax Effect	(32.7)	(2.2)
Other Comprehensive Income (Loss)	54.1	3.5
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	(0.1)	0.1
Tax Effect	0.1
Other Comprehensive Income (Loss)		0.1
Net Unrealized Gains (Losses) on Cash Flow Hedges Designations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(3.7)	2.6
Tax Effect	2.6	(1.0)
Other Comprehensive Income (Loss)	(1.1)	1.6
Net Unrealized Gains (Losses) on Cash Flow Hedges Designations | Reclassification Adjustment for (Gains) Losses Included in Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	1.0	0.2
Tax Effect	(0.4)	(0.1)
Other Comprehensive Income (Loss)	0.6	0.1
Net Unrealized Gains (Losses) on Cash Flow Hedges Designations | Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(4.7)	2.4
Tax Effect	3.0	(0.9)
Other Comprehensive Income (Loss)	(1.7)	1.5
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	25.5	(4.7)
Tax Effect	(31.4)	3.4
Other Comprehensive Income (Loss)	(5.9)	(1.3)
Net Foreign Currency Adjustments | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(90.1)	6.5
Tax Effect	12.2	(0.9)
Other Comprehensive Income (Loss)	(77.9)	5.6
Net Foreign Currency Adjustments | Long-Term Intra-Entity Foreign Currency Transaction Losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(1.0)	(0.6)
Tax Effect	0.3	0.2
Other Comprehensive Income (Loss)	(0.7)	(0.4)
Net Foreign Currency Adjustments | Net Investment Hedge Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	116.6	(10.6)
Tax Effect	(43.9)	4.1
Other Comprehensive Income (Loss)	72.7	(6.5)
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	9.5	6.4
Tax Effect	(3.3)	(3.0)
Other Comprehensive Income (Loss)	6.2	3.4
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	9.5	6.4
Tax Effect	(3.3)	(3.0)
Other Comprehensive Income (Loss)	$ 6.2	$ 3.4