LIABILITY FOR LOSSES AND SETTLEMENT EXPENSES HISTORICAL CLAIMS DURATION (Details)	Dec. 31, 2018
Commercial Auto Liability [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	23.20%
Short-duration insurance contracts, historical claims duration, year two	25.70%
Short-duration insurance contracts, historical claims duration, year three	21.10%
Short-duration insurance contracts, historical claims duration, year four	16.10%
Short-duration insurance contracts, historical claims duration, year five	7.90%
Short-duration insurance contracts, historical claims duration, year six	3.10%
Short-duration insurance contracts, historical claims duration, year seven	1.40%
Short-duration insurance contracts, historical claims duration, year eight	0.40%
Short-duration insurance contracts, historical claims duration, year nine	0.10%
Short-duration insurance contracts, historical claims duration, year ten	0.00%
Commercial Property [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	70.10%
Short-duration insurance contracts, historical claims duration, year two	20.30%
Short-duration insurance contracts, historical claims duration, year three	4.30%
Short-duration insurance contracts, historical claims duration, year four	2.10%
Short-duration insurance contracts, historical claims duration, year five	1.80%
Short-duration insurance contracts, historical claims duration, year six	0.50%
Short-duration insurance contracts, historical claims duration, year seven	0.30%
Short-duration insurance contracts, historical claims duration, year eight	0.00%
Short-duration insurance contracts, historical claims duration, year nine	0.50%
Short-duration insurance contracts, historical claims duration, year ten	0.10%
Workers' Compensation [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	30.80%
Short-duration insurance contracts, historical claims duration, year two	30.00%
Short-duration insurance contracts, historical claims duration, year three	13.80%
Short-duration insurance contracts, historical claims duration, year four	7.40%
Short-duration insurance contracts, historical claims duration, year five	4.20%
Short-duration insurance contracts, historical claims duration, year six	2.30%
Short-duration insurance contracts, historical claims duration, year seven	1.90%
Short-duration insurance contracts, historical claims duration, year eight	1.10%
Short-duration insurance contracts, historical claims duration, year nine	0.90%
Short-duration insurance contracts, historical claims duration, year ten	0.70%
Other Liability [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	11.30%
Short-duration insurance contracts, historical claims duration, year two	19.80%
Short-duration insurance contracts, historical claims duration, year three	19.90%
Short-duration insurance contracts, historical claims duration, year four	16.90%
Short-duration insurance contracts, historical claims duration, year five	12.30%
Short-duration insurance contracts, historical claims duration, year six	6.60%
Short-duration insurance contracts, historical claims duration, year seven	4.80%
Short-duration insurance contracts, historical claims duration, year eight	2.10%
Short-duration insurance contracts, historical claims duration, year nine	1.00%
Short-duration insurance contracts, historical claims duration, year ten	1.60%
Personal Auto Liability [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	45.60%
Short-duration insurance contracts, historical claims duration, year two	29.20%
Short-duration insurance contracts, historical claims duration, year three	14.70%
Short-duration insurance contracts, historical claims duration, year four	8.00%
Short-duration insurance contracts, historical claims duration, year five	2.80%
Short-duration insurance contracts, historical claims duration, year six	1.40%
Short-duration insurance contracts, historical claims duration, year seven	1.00%
Short-duration insurance contracts, historical claims duration, year eight	0.40%
Short-duration insurance contracts, historical claims duration, year nine	0.30%
Short-duration insurance contracts, historical claims duration, year ten	0.00%
Homeowners Insurance [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	83.10%
Short-duration insurance contracts, historical claims duration, year two	13.90%
Short-duration insurance contracts, historical claims duration, year three	2.00%
Short-duration insurance contracts, historical claims duration, year four	0.90%
Short-duration insurance contracts, historical claims duration, year five	0.50%
Short-duration insurance contracts, historical claims duration, year six	0.10%
Short-duration insurance contracts, historical claims duration, year seven	0.20%
Short-duration insurance contracts, historical claims duration, year eight	0.10%
Short-duration insurance contracts, historical claims duration, year nine	0.00%
Short-duration insurance contracts, historical claims duration, year ten	0.00%
Auto Physical Damage [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	94.20%
Short-duration insurance contracts, historical claims duration, year two	6.40%
Short-duration insurance contracts, historical claims duration, year three	(0.30%)
Short-duration insurance contracts, historical claims duration, year four	(0.10%)
Short-duration insurance contracts, historical claims duration, year five	(0.10%)
Short-duration insurance contracts, historical claims duration, year six	0.00%
Short-duration insurance contracts, historical claims duration, year seven	0.00%
Short-duration insurance contracts, historical claims duration, year eight	0.00%
Short-duration insurance contracts, historical claims duration, year nine	0.00%
Short-duration insurance contracts, historical claims duration, year ten	0.00%
Assumed Pro Rata [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	26.50%
Short-duration insurance contracts, historical claims duration, year two	39.60%
Short-duration insurance contracts, historical claims duration, year three	16.30%
Short-duration insurance contracts, historical claims duration, year four	6.30%
Short-duration insurance contracts, historical claims duration, year five	3.50%
Short-duration insurance contracts, historical claims duration, year six	1.20%
Short-duration insurance contracts, historical claims duration, year seven	0.60%
Short-duration insurance contracts, historical claims duration, year eight	0.60%
Short-duration insurance contracts, historical claims duration, year nine	0.40%
Short-duration insurance contracts, historical claims duration, year ten	0.20%
Assumed Excess of Loss [Member]
Short-duration insurance contracts, historical claims duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	30.70%
Short-duration insurance contracts, historical claims duration, year two	31.50%
Short-duration insurance contracts, historical claims duration, year three	11.00%
Short-duration insurance contracts, historical claims duration, year four	7.40%
Short-duration insurance contracts, historical claims duration, year five	4.40%
Short-duration insurance contracts, historical claims duration, year six	2.30%
Short-duration insurance contracts, historical claims duration, year seven	2.40%
Short-duration insurance contracts, historical claims duration, year eight	0.80%
Short-duration insurance contracts, historical claims duration, year nine	1.00%
Short-duration insurance contracts, historical claims duration, year ten	1.90%