Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of income-producing properties	$ 0.0	$ 0.0	$ 1.9	$ 0.0
Income from discontinued operations	0.0	0.0	0.0	34.3
Discontinued Operations | Real Estate Leasing
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of income-producing properties	0.0	0.0	0.0	70.1
Real estate leasing revenue	0.0	0.0	0.0	0.3
Revenue from discontinued operations	0.0	0.0	0.0	70.4
Gain on sale of income-producing properties	0.0	0.0	0.0	55.9
Real estate leasing operating profit	0.0	0.0	0.0	0.3
Total operating profit before taxes	0.0	0.0	0.0	56.2
Income tax expense	0.0	0.0	0.0	21.9
Income from discontinued operations	$ 0.0	$ 0.0	$ 0.0	$ 34.3