CONDENSED CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) (USD $) In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Preferred stock, non-voting, authorized shares	25.0	25.0
Preferred stock, non-voting, issued shares	0	0
Class B common stock held in treasury	7.5	7.5
Class A common stock, voting
Common stock, par value	0.01	0.01
Common stock, authorized shares	500.0	500.0
Common stock, issued shares	2.6	2.6
Common stock, outstanding shares	2.6	2.6
Class B common stock, non-voting
Common stock, par value	0.01	0.01
Common stock, authorized shares	500.0	500.0
Common stock, issued shares	163.7	162.7
Class A exchangeable shares
Exchangeable shares, issued shares	2.9	2.9
Exchangeable shares, outstanding shares	2.9	2.9
Class B exchangeable shares
Exchangeable shares, issued shares	19.3	19.3
Exchangeable shares, outstanding shares	19.3	19.3