Supplemental cash flow information (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012
Interest	$ 11,293		$ 10,220
Income/withholding taxes (1)	27,254	[1]	33,625	[1]
Accrued capital costs	4,034		935
Iceland [Member]
Income/withholding taxes (1)	$ 18,067		$ 22,633

[1] We paid withholding taxes in Iceland of $18,067 and $22,633 in the nine months ended September 30, 2013 and 2012, respectively. Our tax payments in Iceland for withholding taxes, income taxes and associated refunds are denominated in Icelandic kronur ("ISK"). We expect to receive refunds of the withholding tax payments in the fourth quarters of 2013 and 2014. See Note 18 Subsequent events for additional information about withholding tax refunds.