EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Mar. 31, 2018	[1]	Dec. 31, 2017	[1]	Sep. 30, 2017	[1]	Jun. 30, 2017	[1]	Mar. 31, 2017	[1]	Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2015	[1]	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Calculation of earnings per common share - diluted [Abstract]
Net earnings attributable to common shareholders- basic																	$ 55,122	$ 50,556	$ 44,747
Basic and diluted common shares outstanding [Abstract]
Weighted average common shares outstanding - basic (in shares)																	13,790	13,867	14,513
Effect of dilutive shares (in shares)																	177	161	175
Weighted average shares common outstanding - diluted (in shares)																	13,967	14,028	14,688
Earnings per common share - basic (in dollars per share)	$ 0.65		$ 1.12		$ 1.24		$ 0.97		$ 0.76		$ 0.92		$ 1.21		$ 0.76		$ 4.00	$ 3.65	$ 3.08
Earnings per common share - diluted (in dollars per share)	$ 0.65		$ 1.11		$ 1.23		$ 0.96		$ 0.75		$ 0.91		$ 1.21		$ 0.75		$ 3.95	$ 3.60	$ 3.05

[1] Basic and diluted earnings per share are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted per share information may not equal annual basic and diluted earnings per share.