Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Common stock, par value (in dollars per share)	0.001	0.001
Common stock, shares authorized	330,000	330,000
Class A Common Stock
Common stock, shares issued	112,176	111,725
Common stock, shares outstanding	98,190	99,244
Common stock, shares held in treasury	13,986	12,481