Equity Incentive Compensation Plans and Other Benefit Plans (Equity Incentive Plans) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended								12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Two Thousand Ten Equity Incentive Plan	Dec. 31, 2012 Two Thousand Ten Equity Incentive Plan Scenerio One	Dec. 31, 2012 Two Thousand Ten Equity Incentive Plan Scenerio Two	May 31, 2010 Two Thousand Ten Equity Incentive Plan Common Class A	Dec. 31, 2012 Two Thousand Ten Equity Incentive Plan Common Class A Minimum	Dec. 31, 2012 Two Thousand Five Equity Incentive Plan	Dec. 31, 2012 Two Thousand Five Equity Incentive Plan Scenerio One	Dec. 31, 2012 Two Thousand Five Equity Incentive Plan Scenerio Two	May 31, 2005 Two Thousand Five Equity Incentive Plan Common Class A	Dec. 31, 2012 Two Thousand Five Equity Incentive Plan Common Class A Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Expiration	Tenth Year
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%	100.00%				25.00%	100.00%
Options granted under plan, term (in years)				10 years					10 years
Shares available to be issued in period				426,055					173,915
Vesting period based on plan (in years)	4 years				4 years	3 years				4 years	3 years
Total compensation cost (in dollars)	$ 9.3	$ 9.0	$ 8.3