Income Taxes - Reconciliation of Effective Income Tax Rate (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Expense
Federal income tax (expense) benefit at the statutory rate, percent	35.00%	35.00%	(35.00%)
Federal income tax (expense) benefit at the statutory rate	$ 66.0	$ 3.0	$ (10.9)
State income taxes, net of federal tax benefits, percent	3.40%	(52.50%)	(15.00%)
State income taxes, net of federal tax benefits	6.5	(4.4)	(4.7)
Non-deductible expenses and other, percent	(0.90%)	(8.10%)	(2.20%)
Non-deductible expenses and other	(1.8)	(0.7)	(0.7)
Cancellation of stock options, percent	0.00%	(24.50%)	(3.90%)
Cancellation of stock options	0	(2.1)	(1.2)
Non-deductible donation of land, percent	0.00%	0.00%	(3.70%)
Non-deductible donation of land	0	0	(1.1)
Dividend income from foreign subsidiary, percent	(5.40%)	0.00%	0.00%
Dividend income from foreign subsidiary	(10.2)	0	0
Reserves for unrecognized tax benefits, percent	(0.10%)	(1.40%)	1.70%
Reserves for unrecognized tax benefits	(0.2)	(0.1)	0.5
Credits, percent	0.80%	6.20%	3.00%
Credits	(1.6)	(0.4)	(0.9)
Change in valuation allowance/reserve of deferred tax assets, percent	(3.60%)	(10.90%)	47.80%
Change in valuation allowance/reserve of deferred tax assets	$ (6.8)	$ (0.9)	$ 14.9
Income tax (expense) benefit from continuing operations, percent	29.20%	(56.20%)	(7.30%)