Investments And Marketable Securities (Aggregate Market Value And Unrealized Losses Of Investments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	56	13
Aggregate Market Value, Unrealized Loss Less 12 months	$ 60,616	$ 21,736
Unrealized Losses, Unrealized Loss Less 12 months	(865)	(14)
Number of investments, Unrealized Loss Greater 12 months	70	26
Aggregate Market Value, Unrealized Loss Greater 12 months	42,377	34,921
Unrealized Losses, Unrealized Loss Greater 12 months	(572)	(941)
Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	5	0
Aggregate Market Value, Unrealized Loss Less 12 months	4,599	0
Unrealized Losses, Unrealized Loss Less 12 months	(3)	0
Number of investments, Unrealized Loss Greater 12 months	6	1
Aggregate Market Value, Unrealized Loss Greater 12 months	6,708	610
Unrealized Losses, Unrealized Loss Greater 12 months	(4)	(6)
State And Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	16	10
Aggregate Market Value, Unrealized Loss Less 12 months	24,556	17,707
Unrealized Losses, Unrealized Loss Less 12 months	(7)	(6)
Number of investments, Unrealized Loss Greater 12 months	11	13
Aggregate Market Value, Unrealized Loss Greater 12 months	18,612	20,461
Unrealized Losses, Unrealized Loss Greater 12 months	(36)	(457)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	35	3
Aggregate Market Value, Unrealized Loss Less 12 months	31,461	4,029
Unrealized Losses, Unrealized Loss Less 12 months	(855)	(8)
Number of investments, Unrealized Loss Greater 12 months	53	12
Aggregate Market Value, Unrealized Loss Greater 12 months	17,057	13,850
Unrealized Losses, Unrealized Loss Greater 12 months	$ (532)	$ (478)