Goodwill And Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense for acquired intangible assets		$ 25.5	$ 25.8	$ 21.9
Client Contracts And Broker Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets	$ 3.8
Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets, useful life		1 year
Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets, useful life		10 years