Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 31, 2014
Net tax benefit from share-based transactions									$ 1.3	$ 1.6
Unrecognized tax benefit, liability due to tax sharing agreement	0				0				0	0	0	2.5
Adjustment to overstated non-current deferred tax liability	194.0				193.2				194.0	193.2
Reclassification from deferred income taxes, noncurrent	51.8				60.7				51.8	60.7
Non-cash reduction in equity method investments	(0.4)	15.1	0	0					14.7	0	0
The effect to current period income tax expense and net income due to out of period adjustment				1.6
Income tax expense (benefit)	6.2	(14.9)	6.5	0.8	8.5	(0.3)	2.8	0.1	(1.4)	11.1	(5.9)
Correction of an overstatement of net income from continuing operation	8.1	10.8	10.2	1.1	13.3	(3.1)	2.5	(0.2)	30.2	12.5	6.0
KRS II
Investment in various real estate joint ventures	8.4								8.4				23.8
Non-cash reduction in equity method investments									14.7
Income tax expense (benefit)									$ (13.7)