Fair Value Measurements (Schedule Of Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	$ 236,949	$ 213,591
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	130,771	177,613
Certificates Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	40,400	3,500
Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	27,315
U S Government Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	12,231	12,871
Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	4,604	12,065
International Government Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities		1,459
Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	1,400	1,399
Treasury Bills [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities		1,193
Measured At Fair Value On Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	236,949	213,591
Measured At Fair Value On Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	236,949	213,591
Measured At Fair Value On Recurring Basis [Member] | Equity Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	2,182	2,264
Measured At Fair Value On Recurring Basis [Member] | Equity Mutual Funds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	2,182	2,264
Measured At Fair Value On Recurring Basis [Member] | Foreign Currency Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	8,926	4,876
Fair value of Liabilities	1,081	1,365
Measured At Fair Value On Recurring Basis [Member] | Foreign Currency Exchange Contracts [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	8,926	4,876
Fair value of Liabilities	1,081	1,365
Measured At Fair Value On Recurring Basis [Member] | Deferred Compensation [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Liabilities	2,182	2,264
Measured At Fair Value On Recurring Basis [Member] | Deferred Compensation [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Liabilities	2,182	2,264
Measured At Fair Value On Recurring Basis [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Liabilities		384
Measured At Fair Value On Recurring Basis [Member] | Interest Rate Swaps [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Liabilities		384
Measured At Fair Value On Recurring Basis [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	34,208	15,490
Measured At Fair Value On Recurring Basis [Member] | Money Market Funds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	34,208	15,490
Measured At Fair Value On Recurring Basis [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	130,771	177,613
Measured At Fair Value On Recurring Basis [Member] | Corporate Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	130,771	177,613
Measured At Fair Value On Recurring Basis [Member] | Certificates Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	1,500	1,999
Total marketable securities	40,400	3,500
Measured At Fair Value On Recurring Basis [Member] | Certificates Of Deposit [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	1,500	1,999
Total marketable securities	40,400	3,500
Measured At Fair Value On Recurring Basis [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	27,315
Measured At Fair Value On Recurring Basis [Member] | Asset-backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	27,315
Measured At Fair Value On Recurring Basis [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	898	1,800
Total marketable securities	20,228	3,491
Measured At Fair Value On Recurring Basis [Member] | Commercial Paper [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Assets	898	1,800
Total marketable securities	20,228	3,491
Measured At Fair Value On Recurring Basis [Member] | U S Government Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	12,231	12,871
Measured At Fair Value On Recurring Basis [Member] | U S Government Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	12,231	12,871
Measured At Fair Value On Recurring Basis [Member] | Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	4,604	12,065
Measured At Fair Value On Recurring Basis [Member] | Agency Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	4,604	12,065
Measured At Fair Value On Recurring Basis [Member] | International Government Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities		1,459
Measured At Fair Value On Recurring Basis [Member] | International Government Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities		1,459
Measured At Fair Value On Recurring Basis [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	1,400	1,399
Measured At Fair Value On Recurring Basis [Member] | Municipal Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	$ 1,400	1,399
Measured At Fair Value On Recurring Basis [Member] | Treasury Bills [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities		1,193
Measured At Fair Value On Recurring Basis [Member] | Treasury Bills [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities		$ 1,193