Stockholders' Equity (Details ) (USD $) In Millions, unless otherwise specified	1 Months Ended			9 Months Ended
	Feb. 28, 2014 Common stock	Feb. 28, 2013 Common stock	May 31, 2012 Common stock	Sep. 30, 2014 Common stock	Sep. 30, 2013 Common stock	Sep. 30, 2014 Series A Preferred stock	Dec. 31, 2013 Series A Preferred stock	Sep. 30, 2013 Series A Preferred stock	Dec. 31, 2012 Series A Preferred stock	Sep. 30, 2014 Series B Preferred stock	Dec. 31, 2013 Series B Preferred stock	Sep. 30, 2013 Series B Preferred stock	Dec. 31, 2012 Series B Preferred stock
Reconciliation of Outstanding Shares
Outstanding shares at beginning of period				295.2	293.8	3.0	3.0	3.0	3.0	10.0	10.0	10.0	10.0
Shares issued				3.1	4.5
Treasury stock acquired				(4.7)	(4.4)
Outstanding shares at end of period				293.6	293.9	3.0	3.0	3.0	3.0	10.0	10.0	10.0	10.0
Common stock share repurchase disclosures
Share repurchase program, maximum authorized amount (in dollars)	$ 200.0	$ 150.0	$ 200.0