Fair Value Measurements (Schedule Of Assets And Liabilities Carried At Fair Value Measured On A Recurring Basis) (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash		$ 1,400	$ 1,200	$ 900	$ 700
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	514,513	821,345
Restricted cash	[2]	1,356	1,223
Deferred compensation plan assets	[3]	44,257	42,344
Total		560,126	864,912
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	514,513	821,345
Restricted cash	[2]	1,356	1,223
Deferred compensation plan assets	[3]	44,257	42,344
Total		560,126	864,912
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	0	0
Restricted cash	[2]	0	0
Deferred compensation plan assets	[3]	0	0
Total		0	0
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	0	0
Restricted cash	[2]	0	0
Deferred compensation plan assets	[3]	0	0
Total		0	0
Money Market Funds [Member] | Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		$ 194,600	$ 336,000

[1] Cash and cash equivalents consist of deposit accounts and money market funds with original maturity dates of three months or less, which are Level 1 assets. At March 31, 2022 and December 31, 2021, we had $194.6 million and $336.0 million, respectively, in money market funds.

[2] Restricted cash is classified as “Prepaid expenses and other” in the Consolidated Balance Sheets. Restricted cash primarily represents cash held in account for use on customer contracts.

[3] Deferred compensation plan assets are classified as “Other assets” in the Consolidated Balance Sheets.