VARIABLE INTEREST ENTITY - (Carrying Amount of VIE Consolidated Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments
Debt securities, available-for-sale, at amortized cost	$ 433,664	$ 422,300
Equity securities, available-for-sale, at fair value	17,758	15,434
Total investments (including $0 and $26,284 related to the VIE, respectively)	451,525	444,021
Cash and cash equivalents	64,423	86,228	$ 74,593	$ 53,038
Reinsurance recoverable	211,424	124,601
Prepaid reinsurance premiums	108,577	135,492
Premiums receivable, net	29,791	46,393
Deferred acquisition costs	39,436	40,893
Other assets	10,156	13,403
Total assets	925,371	904,873
Liabilities
Loss and loss adjustment expense reserves	296,230	230,515	$ 158,110	$ 97,706
Unearned premiums	281,992	294,423
Reinsurance payable	63,599	71,944
Debt, net of deferred financing costs	44,404	49,251
Other liabilities	19,302	25,059
Total liabilities	710,112	677,414
Monarch Delaware - Variable Interest Entity [Member]
Investments
Debt securities, available-for-sale, at amortized cost		25,111
Equity securities, available-for-sale, at fair value		1,173
Total investments (including $0 and $26,284 related to the VIE, respectively)	0	26,284
Cash and cash equivalents	0	14,211
Reinsurance recoverable		3,323
Prepaid reinsurance premiums		2,481
Premiums receivable, net		1,184
Deferred acquisition costs		1,722
Other assets	$ 0	2,322
Total assets		51,527
Liabilities
Loss and loss adjustment expense reserves		6,356
Unearned premiums		8,752
Reinsurance payable		1,802
Debt, net of deferred financing costs		4,930
Other liabilities		1,825
Total liabilities		$ 23,665