NET EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	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	Dec. 31, 2010
Earnings (Numerator) [Abstract]
Basic EPS - Net earnings									$ 40,005	$ 38,765	$ 33,277
Diluted EPS - Net earnings									$ 40,005	$ 38,765	$ 33,277
Number of Shares (Denominator) [Abstract]
Basic EPS - Weighted average common shares outstanding (in shares)									28,994,212	28,574,623	27,964,348
Effect of dilutive securities - stock options and restricted stock (in shares)									1,358,364	1,669,837	1,656,317
Diluted EPS - Weighted average common shares outstanding (in shares)									30,352,576	30,244,460	29,620,665
Per Share Amount [Abstract]
Basic EPS - Net earnings (in dollars per share)	$ 0.34	$ 0.37	$ 0.34	$ 0.32	$ 0.33	$ 0.38	$ 0.34	$ 0.31	$ 1.38	$ 1.36	$ 1.19
Diluted EPS - Net earnings (in dollars per share)	$ 0.33	$ 0.36	$ 0.33	$ 0.31	$ 0.31	$ 0.36	$ 0.32	$ 0.30	$ 1.32	$ 1.28	$ 1.12
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive stock options outstanding, excluded from diluted earnings per share calculation (in shares)									282,027	15,400	288,000