EMPLOYEE RETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension plans [Member] | Emc Insurance Companies [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 3,708	$ 3,545	$ 7,568	$ 7,185
Interest cost	2,800	2,544	5,595	5,069
Expected return on plan assets	(5,191)	(4,840)	(10,382)	(9,680)
Amortization of net actuarial loss	913	1,083	1,821	2,122
Amortization of prior service cost (credit)	5	7	10	15
Net periodic benefit cost (income)	2,235	2,339	4,612	4,711
Pension plans [Member] | EMC Insurance Group, Inc. [Member]
Components of net periodic benefit cost [Abstract]
Net periodic benefit cost (income)	670	683	1,400	1,400
Entity's share of estimated contributions to employee benefit plan			2,700
Postretirement benefit plans [Member] | Emc Insurance Companies [Member]
Components of net periodic benefit cost [Abstract]
Service cost	340	318	681	636
Interest cost	570	554	1,140	1,108
Expected return on plan assets	(1,078)	(1,056)	(2,156)	(2,112)
Amortization of net actuarial loss	343	373	686	747
Amortization of prior service cost (credit)	(2,788)	(2,834)	(5,577)	(5,669)
Net periodic benefit cost (income)	(2,613)	(2,645)	(5,226)	(5,290)
Postretirement benefit plans [Member] | EMC Insurance Group, Inc. [Member]
Components of net periodic benefit cost [Abstract]
Net periodic benefit cost (income)	$ (736)	$ (730)	(1,500)	$ (1,500)
Entity's share of estimated contributions to employee benefit plan			$ 0