Fair Value Measurements (Schedule Of Assets And Liabilities Carried At Fair Value Measured On A Recurring Basis) (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash		$ 1,200	$ 700	$ 1,100	$ 2,300
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents		821,345	902,867
Restricted cash		1,223	695
Deferred compensation plan assets		42,344	36,491
Total		864,912	940,053
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	[1]	821,345	902,867
Restricted cash	[2]	1,223	695
Deferred compensation plan assets	[3]	42,344	36,491
Total		864,912	940,053
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring 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, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring 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 | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents		$ 336,000	$ 482,200

[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 December 31, 2021 and 2020, we had $336.0 million and $482.2 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.