Acquisitions Of Businesses (Details) $ in Thousands										10 Months Ended		12 Months Ended
	Nov. 01, 2018 Company	Oct. 02, 2018 Company	May 03, 2018 Company	Apr. 04, 2018 Company	Nov. 01, 2017 Company	Mar. 01, 2017 Company	Jan. 04, 2017 Company	Apr. 15, 2016 USD ($) Company	Apr. 01, 2016 Company	Nov. 01, 2018 USD ($)	Nov. 01, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill												$ 990,887	$ 964,893	$ 979,628
Amortization periods												8 years 9 months
Number of businesses acquired | Company	1	1	1	1	1	1	1	1	1
2018 Acquisitions
Business Acquisition [Line Items]
Purchase price										$ 71,300
Working capital acquired												$ 8,600
Other net assets												200
Goodwill												25,900
Identifiable intangible assets												$ 36,600
2017Acquisitions [Member]
Business Acquisition [Line Items]
Purchase price											$ 111,900
Working capital acquired													12,300
Other net assets													2,300
Goodwill													40,700
Identifiable intangible assets													$ 56,600
Ardent [Member]
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired								100.00%
Purchase price								$ 201,400
Working capital acquired								34,100
Other net assets								3,900
Goodwill								121,900
Identifiable intangible assets								41,500
Acquired goodwill, tax deductible amount								$ 99,700
Amortization periods												13 years 6 months