Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit - Permanent tax positions	$ 4.4	$ 4.3
Unrecognized tax benefit - Temporary tax positions	29.5	30.4
Unrecognized tax benefit balance	33.9	34.7
NOL and tax credit carryforwards	(32.8)	(33.6)
Decrease in unrecognized tax benefit	(0.8)
Amounts accrued for penalties related to unrecognized tax benefits	0	0
Federal Tax Loss Carryback Claims [Abstract]
Discrete tax benefit	$ 15
Tax loss carryback period (in years)	2Y
Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Year(s) no longer subject to audit as statute of limitations has expired	2007
Earliest year subject to examination	2008
Colorado [Member]
Income Tax Examination [Line Items]
Earliest year subject to examination	2006
Year(s) under examination	None
Minnesota [Member]
Income Tax Examination [Line Items]
Earliest year subject to examination	2007
Year(s) under examination	None
Texas [Member]
Income Tax Examination [Line Items]
Earliest year subject to examination	2007
Year(s) under examination	None
Wisconsin [Member]
Income Tax Examination [Line Items]
Earliest year subject to examination	2007
Year(s) under examination	None