Significant components of U.S. deferred income tax expense (benefit) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Significant components of U.S. deferred income tax expense (benefit)
Deferred tax (benefit) expense	$ (3,209,000)	$ 10,661,000	$ 17,774,000
Net operating loss carryforward (generated) expired	(6,536,000)	26,924,000	187,597,000
Valuation allowance increase (decrease)	9,745,000	(37,585,000)	(205,371,000)
Provision for Income taxes	$ 0	$ 0	$ 0