COMPUTATION OF EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Information related to EPS computation
Series A 3% Redeemable Convertible Preferred Stock, dividend rate (as a percent)	3.00%		3.00%
Net income allocated to common stockholders (in dollars)	$ 10,266	$ 12,079
Basic:
Weighted-average common shares outstanding	28,055	27,614
Basic (in dollars per share)	$ 0.30	$ 0.36
Diluted:
Weighted-average shares outstanding used in basic calculation	28,055	27,614
Dilutive effect of options (in shares)	308	120
Dilutive effect of unvested restricted stock (in shares)	422	253
Weighted-average common stock and common stock equivalents (in shares)	28,785	27,987
Diluted (in dollars per share)	$ 0.30	$ 0.36
Common Stock
Information related to EPS computation
Net income allocated to common stockholders (in dollars)	8,513	9,981
Basic:
Basic (in dollars per share)	$ 0.30	$ 0.36
Diluted:
Diluted (in dollars per share)	$ 0.30	$ 0.36
Series A 3% Redeemable Convertible Preferred Stock
Information related to EPS computation
Series A 3% Redeemable Convertible Preferred Stock, dividend rate (as a percent)	3.00%	3.00%
Net income allocated to common stockholders (in dollars)	$ 1,753	$ 2,098
Diluted:
Stock issuable upon conversion of the Series A Preferred Stock (in shares)	5,806	5,806
Stock awards excluded from calculation as their effect would be anti-dilutive (in shares)	834	1,061