Income Taxes(Components Of Deferred Income Taxes) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets relating to:
Accrued expenses	$ 588	$ 331
Bad debt reserves	143	89
Insurance reserves	187	139
Lease liabilities	204	180
Retirement liabilities	205	216
Deferred compensation	31	28
Federal and state operating loss carryforwards	274	124
Other	113	71
Total deferred tax assets	1,745	1,178
Deferred Tax Assets, Valuation Allowance	(84)	(45)
Deferred Tax Assets, Net of Valuation Allowance	1,661	1,133
Deferred tax liabilities relating to:
Federal and state intangible assets	2,073	1,999
Capitalized software	670	554
Depreciation and amortization	37	62
Investments basis	407	230
Retirement assets	260	249
Lease right-of-use assets	131	164
Prepaid expenses	102	102
Total deferred tax liabilities	3,680	3,360
Net deferred tax liability	$ 2,019	$ 2,227