Stockholders' Equity - Share Count and Par Value Data Related to Stockholders' Equity (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stockholders Equity [Line Items]
Preferred stock, par value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares outstanding	0	0
Common stock-class A, par value per share	$ 0.01	$ 0.01
Common stock-class A, shares authorized	150,000,000	150,000,000
Common stock-class A, shares issued	72,151,857	72,151,857
Common stock-class A, shares outstanding	50,908,267	52,095,166	55,711,325
Treasury stock, shares held	21,243,590	20,056,691