Supplemental cash flow information (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013
Interest	$ 9,684		$ 11,293
Income/withholding taxes (1)	10,079	[1]	27,254	[1]
Accrued capital costs	663		5,734
Iceland [Member]
Income/withholding taxes (1)	$ 5,491		$ 18,067

[1] We paid withholding taxes in Iceland on intercompany dividends of $5,491 and $18,067 during the nine months ended September 30, 2014 and 2013, respectively. Our tax payments in Iceland for withholding taxes, income taxes and any associated refunds are denominated in Icelandic kronur ("ISK").