Investments in Debt and Equity Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Investments in Debt and Equity Securities
Available-for-sale securities, gross unrealized losses that were in effect for less than one year (as a percent)	94.00%
Available-for-sale securities
Cost	$ 335,228	$ 330,627
Gross Unrealized Gains	67,487	55,357
Gross Unrealized Losses	(8,250)	(8,176)
Fair Value	394,465	377,808
Equity
Available-for-sale securities
Cost	157,649	153,846
Gross Unrealized Gains	57,796	45,071
Gross Unrealized Losses	(3,288)	(3,675)
Fair Value	212,157	195,242
Debt
Available-for-sale securities
Cost	166,551	163,127
Gross Unrealized Gains	9,691	10,286
Gross Unrealized Losses	(4,962)	(4,501)
Fair Value	171,280	168,912
Other
Available-for-sale securities
Cost	11,028	13,654
Fair Value	$ 11,028	$ 13,654

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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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.

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- 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.

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