Goodwill and Other Intangible Assets (Schedule of Recognized Identified Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Acquisition consideration:
Cash, net of cash acquired	$ 589,055	$ 10,493
Identifiable assets acquired and liabilities assumed:
Goodwill	1,331,699		$ 1,243,034
2021 Acquisitions
Acquisition consideration:
Cash, net of cash acquired	589,000
Estimated fair value of contingent consideration	40,100
Total consideration transferred	629,100
Identifiable assets acquired and liabilities assumed:
Current assets, primarily accounts receivable	216,200
Long-term assets, primarily property and equipment and operating lease assets	182,000
Amortizing intangible assets	367,200
Current liabilities, including current portion of operating lease liabilities	(147,300)
Long-term liabilities, primarily operating lease liabilities and deferred income taxes	(77,100)
Total identifiable net assets	541,000
Goodwill	88,100
Total net assets acquired, including goodwill	$ 629,100