Consolidated Balance Sheets Constolidated Balance Sheets Parentheticals (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets
Allowance for doubtful accounts	$ 2,037	$ 1,753
Noncurrent assets
Accumulated depreciation on property and equipment	39,534	32,516
Accumulated amortization on intangible assets	$ 35,145	$ 25,626
Stockholders' equity
Preferred stock, shares authorized	50,000	50,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, shares outstanding	42,420	42,134
Common Stock Class A [Member]
Stockholders' equity
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000	100,000
Common stock, shares issued	42,420	31,646
Common stock, shares outstanding	42,420	31,646
Common Stock Class B [Member]
Stockholders' equity
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000	50,000
Common stock, shares issued	0	10,488
Common stock, shares outstanding	0	10,488