Fair Value Measurements (Schedule Of Assets And Liabilities Carried At Fair Value Measured On A Recurring Basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	$ 480,496	$ 464,617
Restricted cash	[2]	2,082	2,043
Deferred compensation plan assets	[3]	20,372	12,153
Total		502,950	478,813
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	480,496	464,617
Restricted cash	[2]	2,082	2,043
Deferred compensation plan assets	[3]	20,372	12,153
Total		502,950	478,813
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
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] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		$ 187,000	$ 154,600

[1] Cash and cash equivalents include money market funds with original maturity dates of three months or less, which are Level 1 assets. At September 30, 2017 and December 31, 2016, we had $187.0 million and $154.6 million, respectively, in money market funds.

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

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