The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

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- Definition

Amount of the hedged item as of the balance sheet date related to the derivative. For example, the hedged balance on a debt instrument.

+ Details

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- Definition

The average forward price on the group of price risk forward or futures contracts, such as gas futures contracts.

+ Details

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- Definition

Cap rate on an interest rate derivative such as an interest rate cap or collar. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ Details

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- Definition

The percentage of expected requirements covered by the aggregate notional amount of derivative contracts expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract as a percentage of expected need.

+ Details

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Data Type:	num:percentItemType
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Period Type:	instant

- Definition

The time remaining until the derivative matures.

+ Details

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- Definition

Aggregate notional amount of all derivatives. The notional amount relates to a number of currency units, shares, bushels, pounds, or other units specified in a derivative instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Notional Amount
-URI http://asc.fasb.org/extlink&oid=6519104

+ Details

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- Definition

Number of monthly interest payments required under an equipment financing arrangement.

+ Details

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- Definition

Number of monthly interest payments, which are protected against the variability in expected future cash flows attributable to changes in the benchmark interest rate.

+ Details

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Derivative Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	1 Months Ended		1 Months Ended
	Jun. 30, 2011	Jun. 30, 2011 Interest rate cap	Jun. 27, 2011 Interest rate cap	Jun. 30, 2011 Interest rate swap	Dec. 31, 2008 Interest rate swap	Jun. 27, 2011 Interest rate swap	Dec. 30, 2008 Interest rate swap	Jun. 07, 2011 Natural Gas Hedge MMBtu
Fair Value of Financial Instruments
Notional value			$ 255.0			$ 450.0	$ 31.5
Debt instrument, description of variable rate basis	LIBOR or CDOR	3-month LIBOR		3-month LIBOR	1-month LIBOR
Agreement period (in years)			3Y			3Y		1Y
Fixed rate (as a percent)						1.17%	5.59%
Derivative Number of Monthly Interest Payments Hedged					62
Derivative Number of Monthly Interest Payments					64
Fixed rate (as a percent)			2.00%
Amount to be hedged (in mmbtus)								$ 4.2
Price per mmbtu of forecasted natural gas (in dollars per mmbtu)								5.00
Percentage of forecasted natural gas to be hedged (as a percent)								35.00%