Segment Information - Summary of Operations by Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Gross premiums written									$ 1,103,393	$ 1,316,097	$ 1,068,453
Net premiums written									900,959	981,900	610,390
Net premiums earned	$ 272,686	$ 270,325	$ 276,563	$ 335,287	$ 231,947	$ 264,597	$ 228,812	$ 170,219	1,154,861	895,575	613,121
Net incurred losses and LAE	(121,416)	(222,417)	(216,338)	(312,404)	(187,698)	(153,974)	(92,819)	(19,534)	(872,575)	(454,025)	(193,551)
Life and Annuity Policy Benefits	2,199	0	(2,194)	(96)	(786)	(423)	160	46	(91)	(1,003)	(4,015)
Acquisition costs	(95,026)	(50,282)	(66,855)	(93,788)	(55,106)	(54,242)	(53,334)	(30,108)	(305,951)	(192,790)	(96,906)
Operating expenses									(334,837)	(333,234)	(285,237)
Underwriting income (loss)									(358,593)	(85,477)	33,412
Net investment income	79,376	85,472	77,732	78,696	68,453	69,430	66,469	66,319	321,276	270,671	208,789
Net realized and unrealized gains (losses)	152,664	148,185	269,711	460,791	(158,213)	(57,223)	(54,418)	(143,030)	1,031,351	(412,884)	190,334
Fees and commission income	9,007	6,587	6,178	6,681	11,455	6,950	8,352	8,331	28,453	35,088	66,103
Other income	19,502	826	11,030	5,812	34,267	8,226	(9,351)	1,943	37,170	35,085	22,605
Corporate expenses									(138,249)	(74,141)	(150,748)
Interest income (expense)									(52,541)	(26,217)	(28,102)
Net foreign exchange gains (losses)	(12,189)	13,631	2,587	3,850	(1,279)	(1,040)	5,519	(5,868)	7,879	(2,668)	(17,537)
Loss on sale of subsidiary									0	0	(16,349)
EARNINGS (LOSS) BEFORE INCOME TAXES	163,715	123,453	227,859	361,719	(168,554)	(24,892)	(12,144)	(54,953)	876,746	(260,543)	308,507
Income tax benefit (expense)	22,427	(14,597)	(7,518)	(4,749)	10,688	(746)	(3,646)	(172)	(4,437)	6,124	6,395
Earnings from equity method investments	11,722	17,703	17,713	8,772	8,488	3,317	15,645	14,697	55,910	42,147	5,904
NET EARNINGS (LOSS) FROM CONTINUING OPERATIONS									928,219	(212,272)	320,806
Net earnings from discontinued operations, net of income taxes									0	0	10,993
NET EARNINGS (LOSS)	197,864	126,559	238,054	365,742	(149,378)	(22,321)	(145)	(40,428)	928,219	(212,272)	331,799
Net loss (earnings) attributable to noncontrolling interest	4,900	109	2,713	2,148	42,955	11,489	8,389	(782)	9,870	62,051	(20,341)
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED	202,764	126,668	240,767	367,890	(106,423)	(10,832)	8,244	(41,210)	938,089	(150,221)	311,458
Dividends on preferred shares	(8,925)	(8,925)	(8,925)	(9,139)	(7,000)	(5,133)	0	0	(35,914)	(12,133)	0
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED ORDINARY SHAREHOLDERS	$ 193,839	$ 117,743	$ 231,842	$ 358,751	$ (113,423)	$ (15,965)	$ 8,244	$ (41,210)	902,175	(162,354)	311,458
Non-life Run-off
Segment Reporting Information [Line Items]
Net incurred losses and LAE									(51,625)	306,067	190,674
Atrium
Segment Reporting Information [Line Items]
Net incurred losses and LAE									$ (77,276)	$ (69,810)	$ (69,419)
Underwriting ratios:
Loss ratio									47.10%	47.70%	51.50%
Acquisition expense ratio									34.70%	34.60%	35.40%
Other operating expense ratio									8.80%	12.20%	13.00%
Combined ratio									90.60%	94.50%	99.90%
StarStone
Segment Reporting Information [Line Items]
Net incurred losses and LAE									$ (727,636)	$ (673,383)	$ (314,806)
Underwriting ratios:
Loss ratio									90.70%	94.20%	68.50%
Acquisition expense ratio									21.80%	18.90%	10.50%
Other operating expense ratio									15.10%	22.00%	29.50%
Combined ratio									127.60%	135.10%	108.50%
Operating Segments | Non-life Run-off
Segment Reporting Information [Line Items]
Gross premiums written									$ (25,069)	$ (8,910)	$ 14,102
Net premiums written									(25,338)	(9,217)	6,482
Net premiums earned									168,496	9,427	14,162
Net incurred losses and LAE									(51,625)	306,067	190,674
Life and Annuity Policy Benefits									0	0	0
Acquisition costs									(73,642)	(4,006)	(328)
Operating expenses									(199,756)	(158,731)	(132,235)
Underwriting income (loss)									(156,527)	152,757	72,273
Net investment income									275,236	226,287	166,678
Net realized and unrealized gains (losses)									968,350	(381,712)	179,545
Fees and commission income									18,293	16,466	43,849
Other income									34,809	35,978	21,157
Corporate expenses									(70,689)	(39,093)	(101,592)
Interest income (expense)									(62,055)	(30,616)	(28,970)
Net foreign exchange gains (losses)									9,918	2,534	(7,347)
Loss on sale of subsidiary											0
EARNINGS (LOSS) BEFORE INCOME TAXES									1,017,335	(17,399)	345,593
Income tax benefit (expense)									(7,250)	3,581	6,990
Earnings from equity method investments									56,128	42,147	5,904
NET EARNINGS (LOSS) FROM CONTINUING OPERATIONS											358,487
Net earnings from discontinued operations, net of income taxes											0
NET EARNINGS (LOSS)									1,066,213	28,329	358,487
Net loss (earnings) attributable to noncontrolling interest									(6,409)	(3,107)	(14,687)
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED									1,059,804	25,222
Dividends on preferred shares									0	0
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED ORDINARY SHAREHOLDERS									1,059,804	25,222	343,800
Operating Segments | Atrium
Segment Reporting Information [Line Items]
Gross premiums written									192,373	171,494	153,472
Net premiums written									172,356	153,488	134,214
Net premiums earned									164,059	146,315	134,747
Net incurred losses and LAE									(77,276)	(69,810)	(69,419)
Life and Annuity Policy Benefits									0	0	0
Acquisition costs									(56,956)	(50,646)	(47,688)
Operating expenses									(14,452)	(17,777)	(17,444)
Underwriting income (loss)									15,375	8,082	196
Net investment income									7,049	5,686	4,218
Net realized and unrealized gains (losses)									6,195	(3,251)	1,117
Fees and commission income									10,160	18,622	22,788
Other income									140	162	230
Corporate expenses									(13,825)	(6,921)	(12,142)
Interest income (expense)									0	0	(559)
Net foreign exchange gains (losses)									(504)	(3,394)	(5,060)
Loss on sale of subsidiary											0
EARNINGS (LOSS) BEFORE INCOME TAXES									24,590	18,986	10,788
Income tax benefit (expense)									(4,033)	(3,732)	(1,593)
Earnings from equity method investments									0	0	0
NET EARNINGS (LOSS) FROM CONTINUING OPERATIONS											9,195
Net earnings from discontinued operations, net of income taxes											0
NET EARNINGS (LOSS)									20,557	15,254	9,195
Net loss (earnings) attributable to noncontrolling interest									(8,432)	(6,257)	(3,772)
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED									12,125	8,997
Dividends on preferred shares									0	0
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED ORDINARY SHAREHOLDERS									12,125	8,997	5,423
Operating Segments | StarStone
Segment Reporting Information [Line Items]
Gross premiums written									917,555	1,121,135	895,160
Net premiums written									735,429	805,562	464,901
Net premiums earned									801,926	714,959	459,403
Net incurred losses and LAE									(727,636)	(673,383)	(314,806)
Life and Annuity Policy Benefits									0	0	0
Acquisition costs									(174,711)	(135,452)	(48,012)
Operating expenses									(120,629)	(156,726)	(135,558)
Underwriting income (loss)									(221,050)	(250,602)	(38,973)
Net investment income									47,401	35,973	27,706
Net realized and unrealized gains (losses)									50,957	(17,672)	16,613
Fees and commission income									0	0	632
Other income									338	(541)	570
Corporate expenses									(7,790)	0	0
Interest income (expense)									(475)	(624)	(1,902)
Net foreign exchange gains (losses)									(1,538)	(2,856)	(926)
Loss on sale of subsidiary											0
EARNINGS (LOSS) BEFORE INCOME TAXES									(132,157)	(236,322)	3,720
Income tax benefit (expense)									6,931	6,327	988
Earnings from equity method investments									(218)	0	0
NET EARNINGS (LOSS) FROM CONTINUING OPERATIONS											4,708
Net earnings from discontinued operations, net of income taxes											0
NET EARNINGS (LOSS)									(125,444)	(229,995)	4,708
Net loss (earnings) attributable to noncontrolling interest									24,711	71,415	(1,882)
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED									(100,733)	(158,580)
Dividends on preferred shares									0	0
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED ORDINARY SHAREHOLDERS									(100,733)	(158,580)	2,826
Other
Segment Reporting Information [Line Items]
Gross premiums written									18,534	32,378	5,719
Net premiums written									18,512	32,067	4,793
Net premiums earned									20,380	24,874	4,809
Net incurred losses and LAE									(16,038)	(16,899)	0
Life and Annuity Policy Benefits									(91)	(1,003)	(4,015)
Acquisition costs									(642)	(2,686)	(878)
Operating expenses									0	0	0
Underwriting income (loss)									3,609	4,286	(84)
Net investment income									(8,410)	2,725	10,187
Net realized and unrealized gains (losses)									5,849	(10,249)	(6,941)
Fees and commission income									0	0	(1,166)
Other income									1,883	(514)	648
Corporate expenses									(45,945)	(28,127)	(37,014)
Interest income (expense)									9,989	5,023	3,329
Net foreign exchange gains (losses)									3	1,048	(4,204)
Loss on sale of subsidiary											(16,349)
EARNINGS (LOSS) BEFORE INCOME TAXES									(33,022)	(25,808)	(51,594)
Income tax benefit (expense)									(85)	(52)	10
Earnings from equity method investments									0	0	0
NET EARNINGS (LOSS) FROM CONTINUING OPERATIONS											(51,584)
Net earnings from discontinued operations, net of income taxes											10,993
NET EARNINGS (LOSS)									(33,107)	(25,860)	(40,591)
Net loss (earnings) attributable to noncontrolling interest									0	0	0
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED									(33,107)	(25,860)
Dividends on preferred shares									(35,914)	(12,133)
NET EARNINGS (LOSS) ATTRIBUTABLE TO ENSTAR GROUP LIMITED ORDINARY SHAREHOLDERS									$ (69,021)	$ (37,993)	$ (40,591)