INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Held to Maturity and Available-for-sale
Held to maturity and available-for-sale securities, Amortized Cost	$ 684,614	$ 820,164
Held to maturity and available-for-sale securities, Gross Unrealized Holding Gains	56	115
Held to maturity and available-for-sale securities, Gross Unrealized Holding Losses	8	3
Held to maturity and available-for-sale securities, Fair Value	684,662	820,276
Held to Maturity, Available-for-sale, and Trading
Investments, Fair Value Disclosure	688,572us-gaap_InvestmentsFairValueDisclosure	824,186us-gaap_InvestmentsFairValueDisclosure
Variable rate demand notes
Available-for-sale
Amortized Cost	3,900	4,001
Fair Value	3,900	4,001
Short-term \| Certificates of deposit
Held-to-Maturity
Amortized Cost	15,991	19,482
Gross Unrealized Holding Losses	1	2
Fair Value	15,990	19,480
Short-term \| Municipal securities
Held-to-Maturity
Amortized Cost	622,082	744,542
Gross Unrealized Holding Gains	48	105
Fair Value	622,130	744,647
Short-term \| U.S. government Agencies
Held-to-Maturity
Amortized Cost	1,401	9,199
Gross Unrealized Holding Losses		1
Fair Value	1,401	9,198
Short-term \| Auction rate securities
Trading
Fair Value	3,910	3,910
Long-term \| Municipal securities
Held-to-Maturity
Amortized Cost	33,662	42,940
Gross Unrealized Holding Gains	8	10
Fair Value	33,670	42,950
Long-term \| U.S. government Agencies
Held-to-Maturity
Amortized Cost	7,578
Gross Unrealized Holding Losses	7
Fair Value	$ 7,571

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Represents the cost of debt and equity securities, which are categorized as held-to-maturity and available-for-sale, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

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Represents investments in debt securities which are categorized as held-to-maturity and available-for-sale; such investments are normally measured at amortized cost (carrying value) unless circumstances indicate that the value to be recovered from the investment is less than its carried amount. This element may be used in connection with the fair value disclosures required in footnote disclosures to the financial statements.

+ References

No definition available.

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Represents the gross unrealized gains for securities, at a point in time, which are categorized as held-to-maturity and available-for-sale securities.

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No definition available.

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Represents the gross unrealized losses for securities, at a point in time, which are categorized as held-to-maturity and available-for-sale securities.

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No definition available.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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