SHAREHOLDERS EQUITY - Summary of dividend payments (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Note [Abstract]
Record Date	Mar. 18, 2013	Dec. 10, 2012	Sep. 17, 2012	Jun. 18, 2012	Mar. 19, 2012	Dec. 05, 2011	Aug. 19, 2011	May 23, 2011	Mar. 17, 2011
Payment Date	Mar. 25, 2013	Dec. 17, 2012	Sep. 24, 2012	Jun. 25, 2012	Mar. 26, 2012	Dec. 19, 2011	Aug. 26, 2011	May 31, 2011	Mar. 24, 2011
Dividend (per share)	$ 0.14	$ 0.13	$ 0.13	$ 0.13	$ 0.13	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.52	$ 0.48
Dividend paid, amount	$ 1,569	$ 1,447	$ 1,439	$ 1,439	$ 1,437	$ 1,336	$ 1,365	$ 1,429	$ 1,415	$ 5,762	$ 5,545