STOCK OWNERSHIP AND BENEFIT PLANS (Details 5) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock ownership and benefit plans
Number of shares authorized		942,500
Number of shares available for future grant		136,650
Total stock-based compensation expense	$ 895	$ 4,443	$ 3,397	$ 3,501
401 (k) Plan
Matching employer contributions on first level of qualified compensation (as a percent)		100.00%
Percentage of qualified compensation, first level, matched by employer		3.00%
Matching employer contributions on second level of qualified compensation (as a percent)		50.00%
Percentage of qualified compensation, second level, matched by employer		2.00%
Total DMC contributions		431	379	360
Employee Stock Purchase Plan
Stock ownership and benefit plans
Number of shares authorized		600,000
Number of shares available for future grant		158,055
Shares purchased		14,717	8,688	11,005
Total stock-based compensation expense		$ 58	$ 57	$ 48
Employee Stock Purchase Plan | Maximum
Stock ownership and benefit plans
Percentage of earnings that may be authorized by employees to withhold to purchase common stock		15.00%
Percentage of fair market value of the entity's common stock used to purchase common stock on the Offering Date or Purchase Date		85.00%