Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands				6 Months Ended
	Feb. 01, 2016	Jul. 24, 2015	May 01, 2015	Jun. 30, 2016	Dec. 31, 2015
Schedule Of Acquired Intangible Assets By Major Class [Line Items]
Goodwill and other intangible assets				$ 2,217,973	$ 2,210,266
Goodwill acquired during the period				$ 14,084
Allied International Holdings, Inc.
Schedule Of Acquired Intangible Assets By Major Class [Line Items]
Total identified intangible assets	$ 14,000
Goodwill acquired during the period	$ 14,084
New Energy Risk Inc.
Schedule Of Acquired Intangible Assets By Major Class [Line Items]
Goodwill acquired during the period		$ 13,400
Catlin Group Limited
Schedule Of Acquired Intangible Assets By Major Class [Line Items]
Total identified intangible assets			$ 988,000
Goodwill acquired during the period			$ 794,000