Shareholder's Equity (Details) (USD $)	5 Months Ended	7 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended			12 Months Ended
	Dec. 31, 2011	Jul. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Aug. 23, 2011	Jan. 31, 2010 Class A	Dec. 31, 2011 Class A	Dec. 31, 2011 Class B	Dec. 31, 2010 Class B	Dec. 31, 2011 Dividend payments limited by covenants by Credit Agreement
Shareholder's Equity
Common Stock, voting rights (votes per share)								1
Common Stock, voting rights (percent of vote per share)									95.00%
Per share liquidation preference (or restrictions) of common stock that has a preference in involuntary liquidation in excess of the par or stated value of the shares (in dollars per share)									$ 0.50	$ 0.50
Convertible at the option of the holder (shares per share converted)									1
Issuance of Class A common stock (in shares)							8,000,000
Common stock, shares issued price per share (in dollars per share)							$ 29.25
Proceeds from issuance of common stock			$ 0	$ 224,313,000	$ 0		$ 224,300,000
Dividends per share (in dollars per share)			$ 0.31	$ 0.30	$ 0.30
Quarterly dividend, amount of increase in quarterly dividend (in dollars per share)						$ 0.05
Quarterly dividend, previous before Board of Directors approved increase (in dollars per share)		$ 0.075
Quarterly dividend, increase (in dollars per share)	$ 0.08
Dividends payment covenant credit agreement based on net earnings											35,000,000
Dividends payment covenant credit agreement based on net earnings, (as a percent)											75.00%
Dividends payment covenant credit agreement based on net earnings, (Number of quarters)											4
Dividends payment covenant credit agreement based on indentures governing senior and subordinated indentures per share annually (in dollars per share)											$ 0.36
Dividends payments credit agreement bond indentures annually without consideration of coverage ratio or exhausted restricted payments baskets											20,000,000
Dividends payments credit agreement on debt in event it is in a non-payment default											$ 10,000,000