Income taxes (Reconciliation of the Differences Due to Federal Statutory Rate) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Jun. 30, 2013	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Expected federal income tax provision/credit at statutory rates										$ (11,582)	$ (1,370)	$ (238)
State income taxes, net of federal effect										(1,456)	(179)	(33)
Effect of nontaxable income, net										643	489	547
Reversal of valuation allowance	$ (41,600)									4	0	41,632
Section 382 impairment re-evaluation										0	0	8,163
Tax affected disallowed merger costs										0	(974)	0
Rate change for deferred taxes										(353)	1,687	52
Other, net										231	169	23
Benefit (provision) for income taxes		$ (3,878)	$ (2,626)	$ (2,861)	$ (3,148)	$ (2,982)	$ (1,965)	$ 5,065	$ (296)	$ (12,513)	$ (178)	$ 50,146