Accumulated Other Comprehensive Income (Loss) - Details of Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
TAX EFFECT
Other comprehensive income (loss), after reclassifications	$ (25.7)	$ 112.4	$ (72.4)
AFTER TAX
Other Comprehensive Income (Loss)	(14.1)	(44.3)	2.7
Net Unrealized (Losses) Gains on Debt Securities Available for Sale
BEFORE TAX
Other comprehensive income (loss) before reclassifications	(31.9)	(70.2)	(1.8)
Reclassification adjustments	0.5	1.4	(0.5)
Other comprehensive income (loss), after reclassifications	(31.4)	(68.8)	(2.3)
TAX EFFECT
Other comprehensive income (loss) before reclassifications	9.2	26.9	0.7
Reclassification adjustments	(0.1)	(0.5)	0.2
Other comprehensive income (loss), after reclassifications	9.1	26.4	0.9
AFTER TAX
Other comprehensive income (loss) before reclassifications	(22.7)	(43.3)	(1.1)
Reclassification adjustments	0.4	0.9	(0.3)
Other Comprehensive Income (Loss)	(22.3)	(42.4)	(1.4)
Net Unrealized Gains (Losses) on Cash Flow Hedges
BEFORE TAX
Reclassification adjustments	(71.1)	(24.5)	(1.9)
Other comprehensive income (loss), after reclassifications	(1.8)	9.3	2.5
TAX EFFECT
Reclassification adjustments	17.7	9.4	0.7
Other comprehensive income (loss), after reclassifications	0.4	(10.9)	6.6
AFTER TAX
Reclassification adjustments	(53.4)	(15.1)	(1.2)
Other Comprehensive Income (Loss)	(1.4)	(1.6)	9.1
Net Foreign Currency Adjustments
BEFORE TAX
Other comprehensive income (loss) before reclassifications	(107.8)	156.5	(126.5)
Other comprehensive income (loss), after reclassifications	63.4	(64.7)	80.6
TAX EFFECT
Other comprehensive income (loss) before reclassifications	1.5	(3.1)	(3.1)
Other comprehensive income (loss), after reclassifications	(41.2)	81.4	(81.5)
AFTER TAX
Other comprehensive income (loss) before reclassifications	(106.3)	153.4	(129.6)
Other Comprehensive Income (Loss)	22.2	16.7	(0.9)
Long-Term Intra-Entity Foreign Currency Transaction Losses
BEFORE TAX
Other comprehensive income (loss) before reclassifications	(1.8)	2.0	(5.3)
TAX EFFECT
Other comprehensive income (loss) before reclassifications	0.5	(0.7)	2.0
AFTER TAX
Other comprehensive income (loss) before reclassifications	(1.3)	1.3	(3.3)
Net Investment Hedge Gains (Losses)
BEFORE TAX
Other comprehensive income (loss) before reclassifications	173.0	(223.2)	212.4
TAX EFFECT
Other comprehensive income (loss) before reclassifications	(43.2)	85.2	(80.4)
AFTER TAX
Other comprehensive income (loss) before reclassifications	129.8	(138.0)	132.0
Net Pension and Other Postretirement Benefit Adjustments
BEFORE TAX
Other comprehensive income (loss) before reclassifications	(54.9)	(58.4)	(31.1)
Reclassification adjustments	36.3	25.9	25.4
Other comprehensive income (loss), after reclassifications	(18.6)	(32.5)	(5.7)
TAX EFFECT
Other comprehensive income (loss) before reclassifications	9.6	25.4	11.2
Reclassification adjustments	(3.6)	(9.9)	(9.6)
Other comprehensive income (loss), after reclassifications	6.0	15.5	1.6
AFTER TAX
Other comprehensive income (loss) before reclassifications	(45.3)	(33.0)	(19.9)
Reclassification adjustments	32.7	16.0	15.8
Other Comprehensive Income (Loss)	(12.6)	(17.0)	(4.1)
Foreign Exchange Contracts | Net Unrealized Gains (Losses) on Cash Flow Hedges
BEFORE TAX
Other comprehensive income (loss) before reclassifications	70.5	32.5	3.1
TAX EFFECT
Other comprehensive income (loss) before reclassifications	(17.6)	(19.5)	4.2
AFTER TAX
Other comprehensive income (loss) before reclassifications	52.9	13.0	7.3
Interest Rate Contracts | Net Unrealized Gains (Losses) on Cash Flow Hedges
BEFORE TAX
Other comprehensive income (loss) before reclassifications	(1.2)	1.3	1.3
TAX EFFECT
Other comprehensive income (loss) before reclassifications	0.3	(0.8)	1.7
AFTER TAX
Other comprehensive income (loss) before reclassifications	$ (0.9)	$ 0.5	$ 3.0