Commitments And Contingencies (Changes in Self-insurance Liability) (Details) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Write-off of insurance receivables		$ 9,300	$ 5,300		$ 15,000
Litigation of Recorded Insurance Receivable						$ 25,000
Insurance Settlements Receivable		213,407				152,987	$ 213,407
Insurance Related Expenses [Roll Forward]
Balance, beginning of period					$ 831,058	758,812	831,058	$ 924,563
Reserves provided						93,156	98,176	97,916
Adjustment to self insurance reserves	$ 37,900	(75,300)		$ (19,800)		(35,873)	(97,789)	(57,132)
Payments						(79,082)	(72,633)	(134,289)
Balance, end of period		$ 758,812				$ 737,013	$ 758,812	$ 831,058