Stockholders' Equity (Details 2) (USD $) In Millions									1 Months Ended	9 Months Ended
	Sep. 30, 2011 Series A Preferred stock	Dec. 31, 2010 Series A Preferred stock	Sep. 30, 2010 Series A Preferred stock	Dec. 31, 2009 Series A Preferred stock	Sep. 30, 2011 Series B Preferred stock	Dec. 31, 2010 Series B Preferred stock	Sep. 30, 2010 Series B Preferred stock	Dec. 31, 2009 Series B Preferred stock	Aug. 31, 2011 Common stock	Sep. 30, 2011 Common stock	Sep. 30, 2010 Common stock
Reconciliation of Outstanding Shares
Outstanding shares at beginning of period	3.0	3.0	3.0	3.0	10.0	10.0	10.0	10.0		320.4	319.0
Shares issued										1.7	1.4
Treasury stock acquired										(17.0)	(0.1)
Outstanding shares at end of period	3.0	3.0	3.0	3.0	10.0	10.0	10.0	10.0		305.1	320.3
Common stock share repurchase disclosures
Share repurchase program, maximum authorized amount (in dollars)									$ 200.0