Long-term debt Schedule of Long-term Debt (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Apr. 14, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Secured Debt		$ 1,400,000
Unsecured Debt		800,000
Other Long-term Debt	105		113
Long-term Debt	1,926,064		1,529,798
Long-term Debt, Current Maturities	(23,132)		(97,247)
Long-term debt, net of current maturities	1,902,932		1,432,551
Debt Instrument, Unamortized Discount	8,258
Revolving Loan Facility [Member]
Debt Instrument [Line Items]
Secured Debt	239,000	500,000	0
Debt, Weighted Average Interest Rate	3.00%
Term Loan 'A' Facility [Member]
Debt Instrument [Line Items]
Secured Debt	200,000	200,000	0
Debt, Weighted Average Interest Rate	3.00%
Term Loan 'B' Facility [Member]
Debt Instrument [Line Items]
Secured Debt	693,156	700,000	0
Debt Instrument, Unamortized Discount	1,594
Debt, Weighted Average Interest Rate	4.00%
Prior Revolving Loan Facility [Member]
Debt Instrument [Line Items]
Secured Debt	0		510,000
Debt, Weighted Average Interest Rate			3.50%
Prior Term Loan Facility [Member]
Debt Instrument [Line Items]
Secured Debt	0		380,000
Debt, Weighted Average Interest Rate			3.50%
7.5% Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured Debt	793,336		0
Debt Instrument, Unamortized Discount	6,664
Debt Instrument, Interest Rate, Stated Percentage	7.50%
9.25% Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured Debt	467		639,685
Debt Instrument, Unamortized Discount			$ 10,315
Debt Instrument, Interest Rate, Stated Percentage	9.25%		9.25%

Interest rate stated in the contractual debt agreement.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of debt outstanding by type or by instrument at that time.

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Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Total of the portions of the carrying amounts as of the balance sheet date of long-term debt, which may include notes payable, bonds payable, debentures, mortgage loans, and commercial paper, which are scheduled to be repaid within one year or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year (current maturities) or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Including both current and noncurrent portions, carrying amount as of the balance sheet date of other forms of debt not elsewhere specified in the taxonomy with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Carrying value as of the balance sheet date , including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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