Goodwill and Other Intangible Assets Goodwill and Other Intangible Assets (Schedule of Consideration Paid and Net Assets Acquired, Business Combinations, 2019 Acquisitions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquisition consideration:
Cash, net of cash acquired and other	$ 179,481	$ 6,684	$ 115,995
Identifiable assets acquired and liabilities assumed:
Goodwill	1,221,440	$ 1,100,350	$ 1,137,700
2019 Acquisitions [Member]
Acquisition consideration:
Cash, net of cash acquired and other	175,000
Estimated fair value of contingent consideration and other liabilities	38,900
Total consideration transferred	213,900
Identifiable assets acquired and liabilities assumed:
Current assets, primarily composed of accounts receivable	90,000
Property and equipment, including finance leases and other long-term assets	55,200
Amortizing intangible assets	66,100
Current liabilities, including current portion of finance lease obligations and long-term debt	(94,100)
Long-term debt, including finance lease obligations	(2,400)
Deferred income taxes and other long-term liabilities	(21,300)
Total identifiable net assets	93,500
Goodwill	120,400
Total net assets acquired, including goodwill	$ 213,900