Income Taxes - Reconciliation of Effective Income Tax Rate (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Tax Contingency [Line Items]
Federal income tax benefit at the statutory rate, percent	35.00%	(35.00%)	(35.00%)
Federal income tax benefit at the statutory rate	$ 11.4	$ (18.4)	$ (22.1)
State income taxes, net of federal tax benefits, percent	14.90%	(5.80%)	4.60%
State income taxes, net of federal tax benefits	4.8	(3.0)	2.9
Non-deductible expenses and other, percent	2.70%	1.40%	2.60%
Non-deductible expenses and other	0.8	0.7	1.6
Forfeiture of equity compensation, percent	3.70%	0.00%	0.00%
Forfeiture of equity compensation	1.2	0	0
Non-deductible donation of land, percent	3.50%	0.00%	0.00%
Non-deductible donation of land	1.2	0	0
Dividend income from foreign subsidiary, percent	0.00%	3.50%	0.00%
Dividend income from foreign subsidiary	0	1.8	0
Reversal of reserves for unrecognized tax benefits, percent	(1.70%)	(4.10%)	1.90%
Reversal of reserves for unrecognized tax benefits	(0.5)	(2.1)	1.2
Credits, percent	(3.70%)	(13.70%)	(3.10%)
Credits	1.2	7.2	2.0
Change in valuation allowance/reserve of deferred tax assets, percent	(47.20%)	31.40%	28.60%
Change in valuation allowance/reserve of deferred tax assets	(15.4)	16.5	18.1
Income tax (benefit) expense from continuing operations, percent	7.20%	(22.30%)	(0.40%)
Income tax (benefit) expense from continuing operations	$ 2.3	$ (11.7)	$ (0.3)