Federal and state income taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 1,700,000	$ 1,100,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	800,000	700,000
Unrecognized Tax Benefits, Income Tax Penalities and Interest Accrued that Would Impact the Effective Tax Rate	500,000	500,000
Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations	557,000	683,000
Unrecognized Tax Benefits Change in Next Twelve Months	12 months
State and Local Jurisdiction, Missouri [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	250,800,000
State and Local Jurisdiction, Colorado [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 12,000,000