Income taxes (Reconciliation of the Differences Due to Federal Statutory Rate) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Expected federal income tax credit at statutory rates	$ (238)	$ (2,050)	$ 12,547
State income taxes, net of federal effect	(33)	(263)	2,184
Income Tax Reconciliation, Tax Exempt Income	547	583	670
Valuation allowance for deferred tax assets	0	10,762	(25,036)
Reversal of valuation allowance	41,632	0	0
Section 382 impairment re-evaluation	8,163	(8,163)	0
Rate change for deferred taxes	52	(814)	0
Other, net	23	(134)	(737)
Provision (benefit) for income taxes	$ 50,146	$ (79)	$ (10,372)