Fair Value Measurements (Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Assets:
Restricted cash, primarily money market funds	$ 9,166		$ 8,150
Liabilities:
Gain included in interest and other income/expense	3,500	$ 1,500
Equity securities, unrealized gain	3,000	$ 400
Recurring [Member]
Assets:
Assets, fair value disclosure	91,806		97,733
Liabilities:
Deferred compensation plan obligations	34,222		30,996
Total	34,222		30,996
Recurring [Member] | Money Market Funds [Member]
Assets:
Cash equivalents	51,371		54,848
Restricted cash, primarily money market funds	6,213		5,254
Recurring [Member] | Grantor Trusts [Member]
Assets:
Investments	34,222		30,996
Recurring [Member] | Mutual Funds [Member]
Assets:
Investments			6,635
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member]
Assets:
Assets, fair value disclosure	91,806		97,733
Liabilities:
Deferred compensation plan obligations	34,222		30,996
Total	34,222		30,996
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member] | Money Market Funds [Member]
Assets:
Cash equivalents	51,371		54,848
Restricted cash, primarily money market funds	6,213		5,254
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member] | Grantor Trusts [Member]
Assets:
Investments	34,222		30,996
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member] | Mutual Funds [Member]
Assets:
Investments			6,635
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets, fair value disclosure	0		0
Liabilities:
Total	0		0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets:
Assets, fair value disclosure	0		0
Liabilities:
Total	$ 0		$ 0