Investments in Available-for-Sale Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	$ 255,156	$ 240,382
Gross Unrealized Gains	10,108	2,706
Gross Unrealized Losses	(4,328)	(3,436)
Fair Value	260,936	239,652
Total Investments	248,464	234,305
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	126,193	146,993
Gross Unrealized Gains		2
Gross Unrealized Losses	(459)	(412)
Fair Value	125,734	146,583
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	123,692	88,118
Gross Unrealized Gains
Gross Unrealized Losses	(962)	(396)
Fair Value	122,730	87,722
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	5,271	5,271
Gross Unrealized Gains	10,108	2,704
Gross Unrealized Losses	(2,907)	(2,628)
Fair Value	12,472	5,347
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
U.S. government and agency securities	125,734	146,583
Corporate notes and bonds	122,730	87,722
Total Investments	248,464	234,305
Other Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity securities	$ 12,472	$ 5,347

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.

+ References+ Details

Total of debt securities categorized neither as held-to-maturity nor trading which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer.

+ References

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+ Details

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

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+ Details

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details