Subsequent Events Series A-1 Preferred Stock Conversion (Details) (USD $)	12 Months Ended				3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 12, 2013	Mar. 31, 2013 Series A-1 Preferred Stock [Member] The Carlyle Group [Member]	Feb. 12, 2013 Series A-1 Preferred Stock [Member] The Carlyle Group [Member]
Subsequent Event [Line Items]
Optional Preferred Stock Conversion Price						$ 76.03
Conversion of Series A-1 Preferred Stock into Slass A common stock	273,021	216,554			5,984,232
Cash paid with conversion of preferred stock				$ 2,100,000
Series A-1 Preferred Stock dividend	$ 4,375,000	$ 0	$ 0