Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense related to other intangible assets					$ 12.5	$ 13.2
Goodwill	$ 687.2	$ 687.2			$ 687.2		$ 669.3
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000			10,000,000		10,000,000
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense related to other intangible assets		$ 4.2		$ 4.3	$ 12.5	$ 13.2
Estimated future amortization expense for 2019	$ 4.1	4.1			4.1
Estimated future amortization expense for 2020	16.3	16.3			16.3
Estimated future amortization expense for 2021	14.0	14.0			14.0
Estimated future amortization expense for 2022	9.5	9.5			9.5
Estimated future amortization expense for 2023	9.2	9.2			9.2
BEx LLC
Acquired Finite-Lived Intangible Assets [Line Items]
Consideration transferred			$ 37.9
Goodwill			12.5
Software intangible assets acquired			$ 25.0
Belvedere Advisors LLC
Acquired Finite-Lived Intangible Assets [Line Items]
Consideration transferred	17.6
Goodwill	$ 9.3	9.3			9.3
Performance term	5 years
Belvedere Advisors LLC | Computer Software, Intangible Asset
Acquired Finite-Lived Intangible Assets [Line Items]
Software intangible assets acquired	$ 8.3	$ 8.3			$ 8.3