Fair Value Measurements (Financial Assets And Liabilities Carried At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	$ 290,277	$ 211,045
Total assets at fair value	302,686	217,747
Total liabilities at fair value	3,199	3,427
U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	50,847	21,318
Obligations Of Government-Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	16,612	5,785	[1]
State And Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	142,873	134,309
Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	79,909	49,597
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	36	36
Forward Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	9,210	3,275	[2]
Money Market Investments Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	3,199	3,427
Liabilities Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	3,199	3,427
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	25,540	11,203
Total assets at fair value	31,365	16,199
Total liabilities at fair value	3,199	3,427
Level 1 [Member] | U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	25,540	11,203
Level 1 [Member] | Obligations Of Government-Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	0	[1]
Level 1 [Member] | State And Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	0
Level 1 [Member] | Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	0
Level 1 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	0
Level 1 [Member] | Forward Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	2,626	1,569	[2]
Level 1 [Member] | Money Market Investments Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	3,199	3,427
Level 1 [Member] | Liabilities Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	3,199	3,427
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	262,149	194,245
Total assets at fair value	268,733	195,951
Total liabilities at fair value	0	0
Level 2 [Member] | U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	25,307	10,115
Level 2 [Member] | Obligations Of Government-Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	16,612	5,785	[1]
Level 2 [Member] | State And Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	142,873	131,626
Level 2 [Member] | Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	77,321	46,683
Level 2 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	36	36
Level 2 [Member] | Forward Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	6,584	1,706	[2]
Level 2 [Member] | Money Market Investments Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0
Level 2 [Member] | Liabilities Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	0	0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	2,588	5,597
Total assets at fair value	2,588	5,597
Total liabilities at fair value	0	0
Level 3 [Member] | U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	0
Level 3 [Member] | Obligations Of Government-Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	0	[1]
Level 3 [Member] | State And Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	2,683
Level 3 [Member] | Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	2,588	2,914
Level 3 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments subtotal	0	0
Level 3 [Member] | Forward Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0	[2]
Level 3 [Member] | Money Market Investments Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0
Level 3 [Member] | Liabilities Related To The Deferred Compensation Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	$ 0	$ 0

[1] Includes investments in notes issued by the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, the Federal Farm Credit Banks and the Federal Home Loan Bank.

[2] The fair value of forward contracts are calculated as follows: a. Fair value of forward collar contract associated with forecasted sales hedges are calculated using the midpoint of ask and bid rates for similar contracts. b. Fair value of regular forward contracts associated with forecasted sales hedges are calculated using the period-end exchange rate adjusted for the discount rate (3 month LIBOR rate). c. Fair value of balance sheet hedges are calculated at the period end exchange rate adjusted for current forward points unless the hedge has been traded but not settled at period end. If this is the case, the fair value is calculated at the rate at which the hedge is being settled.