Accumulated Other Comprehensive Income (Loss) Changes During Period (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Effect	$ (18.6)	$ (4.3)	$ (18.7)
Other Comprehensive (Loss) Income	(75.4)	38.7	62.6
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	34.7	(152.2)	98.0
Tax Effect	(13.1)	57.2	(36.8)
Other Comprehensive (Loss) Income	21.6	(95.0)	61.2
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	4.5	3.0	15.7
Tax Effect	(1.7)	(1.1)	(5.9)
Other Comprehensive (Loss) Income	2.8	1.9	9.8
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	30.1	(156.8)	96.2
Tax Effect	(11.4)	59.0	(36.1)
Other Comprehensive (Loss) Income	18.7	(97.8)	60.1
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	1.6	(13.9)
Tax Effect		(0.7)	5.2
Other Comprehensive (Loss) Income	0.1	0.9	(8.7)
Net Unrealized (Losses) Gains on Cash Flow Hedges Designations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(12.7)	6.8	8.0
Tax Effect	5.1	(2.5)	(2.4)
Other Comprehensive (Loss) Income	(7.6)	4.3	5.6
Net Unrealized (Losses) Gains on Cash Flow Hedges Designations | Reclassification Adjustment for (Gains) Losses Included in Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(4.0)	4.7	4.8
Tax Effect	1.5	(1.8)	(1.8)
Other Comprehensive (Loss) Income	(2.5)	2.9	3.0
Net Unrealized (Losses) Gains on Cash Flow Hedges Designations | Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(8.7)	2.1	3.2
Tax Effect	3.6	(0.7)	(0.6)
Other Comprehensive (Loss) Income	(5.1)	1.4	2.6
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	33.8	(15.4)	4.2
Tax Effect	(42.6)	12.0	15.8
Other Comprehensive (Loss) Income	(8.8)	(3.4)	20.0
Net Foreign Currency Adjustments | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(107.8)	91.9	37.9
Tax Effect	10.8	(29.7)	3.1
Other Comprehensive (Loss) Income	(97.0)	62.2	41.0
Net Foreign Currency Adjustments | Long-Term Intra-Entity Foreign Currency Transaction Losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(1.0)
Tax Effect	0.4
Other Comprehensive (Loss) Income	(0.6)
Net Foreign Currency Adjustments | Net Investment Hedge Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	142.6	(107.3)	(33.7)
Tax Effect	(53.8)	41.7	12.7
Other Comprehensive (Loss) Income	88.8	(65.6)	(21.0)
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(112.6)	203.8	(28.9)
Tax Effect	32.0	(71.0)	4.7
Other Comprehensive (Loss) Income	(80.6)	132.8	(24.2)
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	25.2	46.1	33.9
Tax Effect	(9.5)	(16.1)	(11.1)
Other Comprehensive (Loss) Income	15.7	30.0	22.8
Net Pension and Other Postretirement Benefit Adjustments | Net Actuarial Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(137.8)	157.7	(62.8)
Tax Effect	41.5	(54.9)	15.8
Other Comprehensive (Loss) Income	$ (96.3)	$ 102.8	$ (47.0)