Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Income Tax Expense Benefit [Line Items]
Interest expense, domestic deposits	$ 65.8	$ 64.2		$ 110.7
Net unrecognized tax benefits	8.8	9.0
Accrued interest and penalties related to unrecognized tax benefits	$ 2.9	2.9
Open tax year	2011 2012
Deferred tax liabilities	$ 445.3	412.6
Undistributed earnings of foreign subsidiaries	$ 631.0	$ 651.0
Federal statutory rate	21.00%	35.00%		35.00%
Deferred income taxes	$ 806.2	$ 851.6	[1]
Noncurrent Liabilities [Member]
Income Tax Expense Benefit [Line Items]
Deferred tax liabilities	106.9	323.3
Deferred minimum tax credits	48.5
General Business Tax Credits [Member]
Income Tax Expense Benefit [Line Items]
Deferred tax credits	$ 799.1
Deferred tax credits expiration year	2034
State Tax Credits [Member]
Income Tax Expense Benefit [Line Items]
Deferred tax credits	$ 7.4
Deferred tax credits expiration year	2021
Deferred tax credits, Foreign		1.9
HR One [Member]
Income Tax Expense Benefit [Line Items]
Deferred income taxes	$ 2.9	$ 1.0
U.S. repatriation tax rate		10.00%
U.S. repatriation tax amount		$ 40.0

[1] See Note 3 - Revenues from Contracts with Customers for additional information about the restatements related to Topic 606.