Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Phantom and restricted stock issuances (in shares)	11,323	193,602	119,010
Stock options exercised (in shares)	22,095	650,621	0
Share repurchase (in shares)	13,948,687	8,620,689	21,721,959
Cancellation of shares (in shares)			68,976
Conversions from Class B to common stock (in shares)	1,323,322	900,290	49