Property and equipment Narrative (Details) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended
	Jun. 30, 2008	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2000	Oct. 31, 1999
Property and Equipment [Abstract]
Capital Leases, Future Minimum Payments Due	$ 48,900,000
Number of renewals permitted under building lease	2
Lessee Leasing Arrangements, Operating Leases, Renewal Term	5 years
Capital Lease Obligations Recorded	27,600,000													12,000,000	15,200,000
Increase in lease financing obligations	12,500,000
Impairment of Long-Lived Assets Held-for-use		0	4,409,000	0	0	0	0	0	0	4,409,000	0	0
Capital Leases, Income Statement, Amortization Expense										1,900,000	2,015,000		2,015,000
Net Book value of Buildings leased		7,700,000				12,600,000				7,700,000	12,600,000
Lease expense for land under operating lease										741,000		741,000	741,000
Repayment of Other Debt, Building Leases										2,200,000	2,000,000	1,900,000
Interest Expense, Other		(261,000)	(271,000)	(280,000)	(288,000)	(297,000)	(305,000)	(312,000)	(321,000)	(1,100,000)	(1,235,000)	(1,360,000)
Impairment of long-lived assets held-for-use included in discontinued operations				$ 687,000