SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, policies j - m (Details) (USD $)	12 Months Ended							12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 US Bank Credit Facility [Member]	Dec. 31, 2011 US Bank Credit Facility [Member]	Dec. 31, 2012 $120 Million Credit Facility [Member]	Dec. 31, 2012 $125 Million Credit Facility [Member]	Dec. 31, 2012 Class A Common Stock [Member]	Dec. 31, 2011 Class A Common Stock [Member]	Dec. 31, 2009 Class A Common Stock [Member] 2006 Share Repurchase Program [Member]	Dec. 31, 2006 Class A Common Stock [Member] 2006 Share Repurchase Program [Member]	Dec. 31, 2009 Class A Common Stock [Member] 2009 Share Repurchase Program [Member]	Dec. 31, 2010 Class A Common Stock [Member] 2010 Share Repurchase Program [Member]	Dec. 31, 2011 Class A Common Stock [Member] 2011 Share Repurchase Program [Member]	Dec. 31, 2012 Class B Common Stock [Member]	Dec. 31, 2011 Class B Common Stock [Member]	Dec. 31, 2012 Treasury Stock [Member]	Dec. 31, 2011 Treasury Stock [Member]
Class of Stock [Line Items]
Common Stock, shares authorized (in shares)								160,000,000	160,000,000						30,000,000	30,000,000
Common Stock, par value (in dollars per share)								$ 0.01	$ 0.01						$ 0.01	$ 0.01
Common Stock, voting rights								1 vote							10 votes
Common Stock, conversion basis								1.075
Preferred Stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred Stock, shares issued (in shares)	0	0
Common stock split ratio		2.0
Reconciliation of outstanding share [Abstract]
Balance (in shares)								20,049,086	19,934,066						2,919,790	3,040,620	4,931,872	4,882,672
Conversion of Class B to Class A (in shares)								23,423	129,882						(21,794)	(120,830)	0	0
Repurchase of Class A Common Stock (in shares)									(49,200)							0		49,200
Issuance of shares for stock options (in shares)	198,000	240,500	272,500						34,338							0		0
Balance (in shares)								20,072,509	20,049,086						2,897,996	2,919,790	4,931,872	4,931,872
Repurchase Program [Line Items]
Share repurchase program, authorized amount											$ 20,000,000	$ 15,000,000	$ 15,000,000	$ 15,000,000
Share repurchase program, total amount authorized										80,000,000
Share repurchase program, amount to trigger plan expiration		15,000,000
Shares repurchased, value		798,000	2,803,000
Shares repurchased, average cost per share (in dollars per share)		$ 16.21
Share repurchase program, remaining authorized amount	15,000,000
Debt Instrument [Line Items]
Face amount of debt instrument						120,000,000	125,000,000
Revenue Recognition [Abstract]
Percentage of revenue derived from private payers	100.00%	99.00%	98.00%
Deferred revenue, amortization period	14 months
Advertising Expense	800,000	600,000	800,000
Deferred Financing Costs [Line Items]
Deferred financing costs, gross	2,000,000	1,900,000	300,000	2,000,000	1,900,000
Credit facility	125,000,000
Interest expense from deferred financing costs	1,100,000	300,000
Amortized deferred financing fees	$ 600,000	$ 782,000	$ 455,000