Income Taxes - Deferred Tax Assets and Deferred Tax Liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Benefit plans	$ 23.6	$ 32.2
Capitalized costs	24.1	17.8
Charitable contribution	1.5	4.0
Basis differences for property and equipment	0	3.6
Joint ventures and other investments	15.0	5.5
Impairment and amortization	0.5	4.1
Insurance and other reserves	6.7	5.4
Solar credit	3.5	2.9
Other	5.4	0.8
Total deferred tax assets	80.3	76.3
Deferred tax liabilities:
Tax-deferred gains on real estate transactions	225.4	211.4
Basis differences for property and equipment	23.4	0
Straight-line rental income and advanced rent	7.2	8.1
Other	5.2	1.9
Total deferred tax liabilities	261.2	221.4
Net deferred tax liability	$ 180.9	$ 145.1