Fair Value Measurements (Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Liabilities:
Gain included in interest and other income/expense	$ 1,500
Unrealized gain (loss) included in interest and other income/expense	400
Recurring [Member]
Assets:
Total	120,214	$ 40,738
Liabilities:
Deferred compensation plan obligations	31,775	31,497
Total	31,775	31,497
Recurring [Member] | Money Market Funds [Member]
Assets:
Cash equivalents, primarily money market funds (1)	81,285
Recurring [Member] | Grantor Trusts [Member]
Assets:
Investments	31,775	31,497
Recurring [Member] | Mutual Funds [Member]
Assets:
Investments	7,154	7,206
Recurring [Member] | Interest Rate Contracts [Member]
Assets:
Derivative assets		2,035
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member]
Assets:
Total	120,214	38,703
Liabilities:
Deferred compensation plan obligations	31,775	31,497
Total	31,775	31,497
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member] | Money Market Funds [Member]
Assets:
Cash equivalents, primarily money market funds (1)	81,285
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member] | Grantor Trusts [Member]
Assets:
Investments	31,775	31,497
Recurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member] | Mutual Funds [Member]
Assets:
Investments	7,154	7,206
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Total	0	2,035
Liabilities:
Total	0	0
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Contracts [Member]
Assets:
Derivative assets		2,035
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets:
Total	0	0
Liabilities:
Total	$ 0	$ 0