Marketable Securities (Details) (USD $) In Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Company's marketable securities
Amortized Cost	$ 364,125	$ 430,242
Gross Unrealized Gains	671	2,691
Gross Unrealized Losses	(12,070)	(2,968)
Estimated Fair Value	352,726	429,965
Municipal securities [Member]
Company's marketable securities
Amortized Cost	314,125	368,583
Gross Unrealized Gains	671	550
Gross Unrealized Losses	(406)	(2,833)
Estimated Fair Value	314,390	366,300
Treasury Securities [Member]
Company's marketable securities
Amortized Cost		7,937
Gross Unrealized Gains		11
Gross Unrealized Losses		(57)
Estimated Fair Value		7,981
Corporate Debt Securities [Member]
Company's marketable securities
Amortized Cost		3,722
Gross Unrealized Gains		0
Gross Unrealized Losses		(78)
Estimated Fair Value		3,644
Equity Securities [Member]
Company's marketable securities
Amortized Cost	50,000	50,000
Gross Unrealized Gains	0	2,130
Gross Unrealized Losses	(11,664)	0
Estimated Fair Value	$ 38,336	$ 52,130

- Definition

This item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.

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