Convertible Securities (Details) $ / shares in Units, shares in Millions	12 Months Ended
Dec. 31, 2015 USD ($) trading_day $ / shares	Dec. 31, 2014 USD ($) shares
Debt Instrument
Shares issued in conversion \| shares		1.9
Loss recognized on conversion of debt securities		$ 18,800,000
2006 Junior Convertible Securities
Debt Instrument
Outstanding principal of junior convertible trust preferred securities		$ 300,000,000.0
2007 Junior Convertible Securities
Debt Instrument
Stated interest rate	5.15%
Principal amount at maturity	$ 50
Conversion ratio (in shares)	0.25
Conversion price (in usd per share) \| $ / shares	$ 200
Redemption closing price trigger \| $ / shares	$ 260
Number of trading days closing price has exceeded threshold \| trading_day	20
Consecutive trading days	30 days
Deferred tax liability	$ 9,400,000
Common Stock
Debt Instrument
Shares issued in conversion \| shares		1.9

Debt Instrument, Individual Security, Face Amount

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Represents the deferred taxes generated from the excess of the interest expense calculated under federal income tax regulations over interest expense as calculated for book purposes.

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- Definition

Gain (Loss) on Conversion of Debt Securities

+ References

No definition available.

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- Definition

The amount of the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
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- Definition

The price per share of the conversion feature embedded in the debt instrument.

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- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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- Definition

Price of the entity's common stock which would be required to be attained for the conversion feature embedded in the debt instrument to become effective.

+ References

No definition available.

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- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instruments must exceed threshold percentage for a specified number of trading days to trigger conversion feature, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Number of shares issued during the period as a result of the conversion of convertible securities.

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