Property and equipment Narrative (Details) (USD $)	1 Months Ended	12 Months Ended
	Jun. 30, 2008	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
Capital Lease Obligations Recorded	27,600,000				12,000,000	15,200,000
Increase in lease financing obligations	12,500,000
Capital Leases, Income Statement, Amortization Expense		2,000,000	2,000,000	2,000,000
Net Book value of Buildings leased		12,600,000	14,600,000
Lease expense for land under operating lease		741,000	741,000	741,000
Repayment of Other Debt, Building Leases		2,000,000	1,900,000	1,700,000
Interest Expense, Other		$ (1,235,000)	$ (1,360,000)	$ (1,468,000)