Segment Reporting (Schedule Of Significant Components Of The Company's Revenues And Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Gross premiums written	$ 922,090	$ 862,133
Net premiums written	544,136	511,675
Net premiums earned	366,045	353,606
Net claims and claim expenses incurred	193,081	126,605
Acquisition expenses	83,282	65,592
Operational expenses	47,283	56,235
Underwriting income (loss)	42,399	105,174
Net investment income	54,325	28,863
Net foreign exchange gains (losses)	8,165	(1,692)
Equity in (losses) earnings of other ventures	(1,507)	1,611
Other income	1,665	4,079
Net realized and unrealized gains on investments	43,373	61,653
Corporate expenses	(5,286)	(8,225)
Interest expense	(10,526)	(10,538)
Income before taxes	132,608	180,925
Income tax expense	(334)	(2,744)
Net income attributable to redeemable noncontrolling interests	(34,327)	(44,591)
Dividends on preference shares	(5,595)	(5,595)
Net income available to RenaissanceRe common shareholders	92,352	127,995
Net claims and claim expenses incurred – current accident year	164,075	128,209
Net claims and claim expenses incurred – prior accident years	29,006	(1,604)
Total net incurred	$ 193,081	$ 126,605
Net claims and claim expense ratio – current accident year	44.80%	36.30%
Net claims and claim expense ratio – prior accident years	7.90%	(0.50%)
Net claims and claim expense ratio – calendar year	52.70%	35.80%
Underwriting expense ratio	35.70%	34.50%
Combined ratio	88.40%	70.30%
Other
Segment Reporting Information [Line Items]
Gross premiums written	$ 0	$ 0
Net premiums written	0	0
Net premiums earned	(2)	0
Net claims and claim expenses incurred	(328)	(82)
Acquisition expenses	0	0
Operational expenses	11	60
Underwriting income (loss)	315	22
Net investment income	54,325	28,863
Net foreign exchange gains (losses)	8,165	(1,692)
Equity in (losses) earnings of other ventures	(1,507)	1,611
Other income	1,665	4,079
Net realized and unrealized gains on investments	43,373	61,653
Corporate expenses	(5,286)	(8,225)
Interest expense	(10,526)	(10,538)
Income tax expense	(334)	(2,744)
Net income attributable to redeemable noncontrolling interests	(34,327)	(44,591)
Dividends on preference shares	(5,595)	(5,595)
Net claims and claim expenses incurred – current accident year	0	0
Net claims and claim expenses incurred – prior accident years	(328)	(82)
Total net incurred	(328)	(82)
Property
Segment Reporting Information [Line Items]
Net claims and claim expenses incurred – prior accident years	(928)	(5,928)
Property | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written	520,529	444,959
Net premiums written	289,871	232,859
Net premiums earned	186,988	175,232
Net claims and claim expenses incurred	38,838	21,804
Acquisition expenses	29,103	20,124
Operational expenses	27,665	28,657
Underwriting income (loss)	91,382	104,647
Net claims and claim expenses incurred – current accident year	39,766	27,732
Net claims and claim expenses incurred – prior accident years	(928)	(5,928)
Total net incurred	$ 38,838	$ 21,804
Net claims and claim expense ratio – current accident year	21.30%	15.80%
Net claims and claim expense ratio – prior accident years	(0.50%)	(3.40%)
Net claims and claim expense ratio – calendar year	20.80%	12.40%
Underwriting expense ratio	30.30%	27.90%
Combined ratio	51.10%	40.30%
Casualty and Specialty
Segment Reporting Information [Line Items]
Net claims and claim expenses incurred – prior accident years	$ 30,262	$ 4,406
Casualty and Specialty | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written	401,561	417,174
Net premiums written	254,265	278,816
Net premiums earned	179,059	178,374
Net claims and claim expenses incurred	154,571	104,883
Acquisition expenses	54,179	45,468
Operational expenses	19,607	27,518
Underwriting income (loss)	(49,298)	505
Net claims and claim expenses incurred – current accident year	124,309	100,477
Net claims and claim expenses incurred – prior accident years	30,262	4,406
Total net incurred	$ 154,571	$ 104,883
Net claims and claim expense ratio – current accident year	69.40%	56.30%
Net claims and claim expense ratio – prior accident years	16.90%	2.50%
Net claims and claim expense ratio – calendar year	86.30%	58.80%
Underwriting expense ratio	41.20%	40.90%
Combined ratio	127.50%	99.70%