Goodwill And Intangible Assets (Components Of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	$ 992,776	$ 855,809
Intangible assets, accumulated amortization	(200,404)	(153,062)
Customer Relationships [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	481,547	452,157
Intangible assets, accumulated amortization	(97,892)	(69,483)
Broker Relationships [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	182,626	175,681
Intangible assets, accumulated amortization	(45,135)	(34,827)
Trade Names [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	103,681	94,795
Intangible assets, accumulated amortization	(23,821)	(17,673)
Investment Management Agreements [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	98,000	0
Intangible assets, accumulated amortization	0	0
Technology [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	54,241	62,288
Intangible assets, accumulated amortization	(22,288)	(22,671)
Insurance Licenses [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	30,185	39,985
Intangible assets, accumulated amortization	0	0
Lloyd's Syndicate Capacity [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	12,000	12,000
Intangible assets, accumulated amortization	0	0
Other [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	30,496	18,903
Intangible assets, accumulated amortization	$ (11,268)	$ (8,408)