Fair Value Measurements (Schedule Of Assets And Liabilities Carried At Fair Value Measured On A Recurring Basis) (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash		$ 2,300	$ 2,000	$ 2,000	$ 4,200
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents		363,907	467,430
Restricted cash		2,307	1,958
Deferred compensation plan assets		23,124	22,054
Total		389,338	491,442
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	[1]	363,907	467,430
Restricted cash	[2]	2,307	1,958
Deferred compensation plan assets	[3]	23,124	22,054
Total		389,338	491,442
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		$ 161,300	$ 194,200

[1] Cash and cash equivalents consist primarily of money market funds with original maturity dates of three months or less, which are Level 1 assets. At December 31, 2018 and 2017, we had $161.3 million and $194.2 million, respectively, in money market funds.

[2] Restricted cash is classified as “Prepaid expenses and other” in the Consolidated Balance Sheets.

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