Investments (Breakdown Of Investments With Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value In Loss Position for Less Than 12 Months	$ 64,612
Unrealized Losses In Loss Position for Less Than 12 Months	(394)
Fair Value In Loss Position for 12 Months or Greater	42,891
Unrealized Losses In Loss Position for 12 Months or Greater	(5,984)
Total, Fair Value	107,503
Total, Unrealized Losses	(6,378)
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value In Loss Position for Less Than 12 Months	47,097
Unrealized Losses In Loss Position for Less Than 12 Months	(144)
Fair Value In Loss Position for 12 Months or Greater	0
Unrealized Losses In Loss Position for 12 Months or Greater	0
Total, Fair Value	47,097
Total, Unrealized Losses	(144)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value In Loss Position for Less Than 12 Months	17,515
Unrealized Losses In Loss Position for Less Than 12 Months	(250)
Fair Value In Loss Position for 12 Months or Greater	0
Unrealized Losses In Loss Position for 12 Months or Greater	0
Total, Fair Value	17,515
Total, Unrealized Losses	(250)
Auction Rate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value In Loss Position for Less Than 12 Months	0
Unrealized Losses In Loss Position for Less Than 12 Months	0
Fair Value In Loss Position for 12 Months or Greater	42,891
Unrealized Losses In Loss Position for 12 Months or Greater	(5,984)
Total, Fair Value	42,891
Total, Unrealized Losses	$ (5,984)