Income taxes (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Tax Disclosure [Abstract]
Income tax expense	$ 1,384,000	$ 1,168,000	$ 4,714,000	$ 7,384,000
Unrecognized Tax Benefits	14,341,000		14,341,000
Proceeds from Income Tax Refunds			$ 5,009,000