Accumulated Other Comprehensive Income (Loss) Changes During Period (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Effect	$ (17.0)	$ (18.6)	$ (4.3)
Other Comprehensive (Loss) Income	(53.0)	(75.4)	38.7
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(94.0)	34.7	(152.2)
Tax Effect	35.4	(13.1)	57.2
Other Comprehensive (Loss) Income	(58.6)	21.6	(95.0)
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	0.0	4.5	3.0
Tax Effect	0.0	(1.7)	(1.1)
Other Comprehensive (Loss) Income	0.0	2.8	1.9
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	(94.3)	30.1	(156.8)
Tax Effect	35.5	(11.4)	59.0
Other Comprehensive (Loss) Income	(58.8)	18.7	(97.8)
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	0.3	0.1	1.6
Tax Effect	(0.1)	0.0	(0.7)
Other Comprehensive (Loss) Income	0.2	0.1	0.9
Net Unrealized (Losses) Gains on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	3.5	(12.7)	6.8
Tax Effect	(1.8)	5.1	(2.5)
Other Comprehensive (Loss) Income	1.7	(7.6)	4.3
Net Unrealized (Losses) Gains on Cash Flow Hedges | Reclassification Adjustment for (Gains) Losses Included in Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	4.7	(4.0)	4.7
Tax Effect	(2.0)	1.5	(1.8)
Other Comprehensive (Loss) Income	2.7	(2.5)	2.9
Net Unrealized (Losses) Gains on Cash Flow Hedges | Unrealized (Losses) Gains on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(1.2)	(8.7)	2.1
Tax Effect	0.2	3.6	(0.7)
Other Comprehensive (Loss) Income	(1.0)	(5.1)	1.4
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	28.4	33.8	(15.4)
Tax Effect	(44.3)	(42.6)	12.0
Other Comprehensive (Loss) Income	(15.9)	(8.8)	(3.4)
Net Foreign Currency Adjustments | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(101.5)	(107.8)	91.9
Tax Effect	4.9	10.8	(29.7)
Other Comprehensive (Loss) Income	(96.6)	(97.0)	62.2
Net Foreign Currency Adjustments | Long-Term Intra-Entity Foreign Currency Transaction Losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(18.7)	(1.0)	0.0
Tax Effect	7.1	0.4	0.0
Other Comprehensive (Loss) Income	(11.6)	(0.6)	0.0
Net Foreign Currency Adjustments | Net Investment Hedge Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	148.6	142.6	(107.3)
Tax Effect	(56.3)	(53.8)	41.7
Other Comprehensive (Loss) Income	92.3	88.8	(65.6)
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	26.1	(112.6)	203.8
Tax Effect	(6.3)	32.0	(71.0)
Other Comprehensive (Loss) Income	19.8	(80.6)	132.8
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	38.3	25.2	46.1
Tax Effect	(14.5)	(9.5)	(16.1)
Other Comprehensive (Loss) Income	23.8	15.7	30.0
Net Pension and Other Postretirement Benefit Adjustments | Net Actuarial Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	(12.2)	(137.8)	157.7
Tax Effect	8.2	41.5	(54.9)
Other Comprehensive (Loss) Income	$ (4.0)	$ (96.3)	$ 102.8