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Income taxes Additional income tax details (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Internal Revenue Service (IRS) [Member]		Dec. 31, 2012 Internal Revenue Service (IRS) [Member]
Additional income tax disclosures [Abstract]
Reduction in reserve for unrecognized tax benefits related to prior years	$ 14,300
Proceeds from income tax refunds	5,009
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		$ 1,287,118	[1]	$ 1,176,802	[1]
[1] The federal NOL begins to expire in 2028.

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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The amount of cash received during the period as refunds for the overpayment of taxes.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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