Equity Incentive Compensation Plans and Other Benefit Plans (Equity Incentive Plans) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 2010 Equity Incentive Plan	Dec. 31, 2011 2005 Equity Incentive Plan	Dec. 31, 2011 Scenerio One 2010 Equity Incentive Plan	Dec. 31, 2011 Scenerio One 2005 Equity Incentive Plan	Dec. 31, 2011 Scenerio Two 2010 Equity Incentive Plan	Dec. 31, 2011 Scenerio Two 2005 Equity Incentive Plan	May 31, 2010 Class A 2010 Equity Incentive Plan	May 31, 2005 Class A 2005 Equity Incentive Plan	Dec. 31, 2011 Class A Minimum 2010 Equity Incentive Plan	Dec. 31, 2011 Class A Minimum 2005 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of Common Stock shares available for grant										1,000,000	2,900,000
Options may not be less than fair market value of Common Stock on the date of grant (in shares)												1	1
Vesting rate based on Plan (as a percent)						25.00%	25.00%	100.00%	100.00%
Options granted under plan, term (in years)				10 years	10 years
Shares available to be issued in period				697,596	189,297
Vesting period based on plan (in years)	4 years					4 years	4 years	3 years	3 years
Total compensation cost (in dollars)	$ 9.0	$ 8.3	$ 7.7