Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Unamortized discount on recourse debt	$ 70.6	[1]	$ 74.1
Preferred stock, shares authorized	1,500,000	[1]	1,500,000
Preferred stock, shares unissued	1,500,000	[1]	1,500,000
Common stock, shares authorized	200,000,000	[1]	200,000,000
Restricted cash	231.4	[1]	260.7
Property, plant, and equipment, at cost	6,145.5	[1]	6,275.8
Less accumulated depreciation	1,524.9	[1]	1,505.2
Partially-owned subsidiaries
Restricted cash	76.7	[1]	77.1
Property, plant, and equipment, at cost	1,889.1	[1]	1,887.2
Less accumulated depreciation	$ 215.3	[1]	$ 202.1

[1] (unaudited)