Goodwill and Other Intangibles - Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Beginning Balance	$ 605.6	$ 519.4
Goodwill Acquired	71.4	78.3
Measurement Period Adjustments		(1.3)
Foreign Exchange Rates	(7.7)	9.2
Ending Balance	669.3	605.6
CORPORATE & INSTITUTIONAL SERVICES
Goodwill [Roll Forward]
Beginning Balance	534.5	448.4
Goodwill Acquired	71.4	78.3
Measurement Period Adjustments		(1.3)
Foreign Exchange Rates	(7.7)	9.1
Ending Balance	598.2	534.5
WEALTH MANAGEMENT
Goodwill [Roll Forward]
Beginning Balance	71.1	71.0
Goodwill Acquired	0.0	0.0
Measurement Period Adjustments		0.0
Foreign Exchange Rates	0.0	0.1
Ending Balance	$ 71.1	$ 71.1

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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