Summary of Significant Accounting Policies (Details 4) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Fair Value Measurements
Fair value of marketable securities	$ 2,600,000	$ 2,400,000
Cost of marketable securities	2,600,000	2,500,000
Level 1
Fair Value Measurements
Pension plan assets at fair value	1,000,000	3,800,000
Level 1 \| Cash and equivalents
Fair Value Measurements
Pension plan assets at fair value	1,000,000	3,800,000
Level 2
Fair Value Measurements
Pension plan assets at fair value	238,300,000	206,800,000
Level 2 \| Equity securities, domestic
Fair Value Measurements
Pension plan assets at fair value	53,200,000	61,300,000
Level 2 \| Equity securities, international
Fair Value Measurements
Pension plan assets at fair value	43,200,000	29,400,000
Level 2 \| Fixed income
Fair Value Measurements
Pension plan assets at fair value	141,900,000	116,100,000
Total
Fair Value Measurements
Pension plan assets at fair value	239,300,000	210,600,000
Total \| Equity securities, domestic
Fair Value Measurements
Pension plan assets at fair value	53,200,000	61,300,000
Total \| Equity securities, international
Fair Value Measurements
Pension plan assets at fair value	43,200,000	29,400,000
Total \| Fixed income
Fair Value Measurements
Pension plan assets at fair value	141,900,000	116,100,000
Total \| Cash and equivalents
Fair Value Measurements
Pension plan assets at fair value	$ 1,000,000	$ 3,800,000

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

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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