EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2019		Mar. 31, 2018		Mar. 31, 2017
Earnings Per Share, Basic and Diluted [Abstract]
Net earnings attributable to common shareholders - basic and diluted	$ 15,052		$ 14,864		$ 18,003		$ 15,273		$ 8,897		$ 15,581		$ 17,221		$ 13,423		$ 63,192		$ 55,122		$ 50,556
Basic and diluted common shares outstanding [Abstract]
Weighted average common shares outstanding - basic (in shares)																	13,448		13,790		13,867
Effect of dilutive shares (in shares)																	130		177		161
Weighted average shares common outstanding - diluted (in shares)																	13,578		13,967		14,028
Earnings per common share - basic (in dollars per share)	$ 1.12	[1]	$ 1.10	[1]	$ 1.33	[1]	$ 1.14	[1]	$ 0.65	[1]	$ 1.12	[1]	$ 1.24	[1]	$ 0.97	[1]	$ 4.70	[1]	$ 4.00	[1]	$ 3.65
Earnings per common share - diluted (in dollars per share)	$ 1.12	[1]	$ 1.10	[1]	$ 1.33	[1]	$ 1.12	[1]	$ 0.65	[1]	$ 1.11	[1]	$ 1.23	[1]	$ 0.96	[1]	$ 4.65	[1]	$ 3.95	[1]	$ 3.60

[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.