Income Taxes (Narrative) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	$ 12,641,000	$ 2,425,000	$ 1,864,000	$ 1,964,000
Unrecognized tax benefits that would impact effective tax rate	10,200,000	2,200,000	1,100,000
State Jurisdiction | Colorado
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	46,500,000
State Jurisdiction | Kansas
Operating Loss Carryforwards [Line Items]
Income tax credit	$ 15,800,000