Schedule III - Supplementary insurance information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplementary Insurance Information, by Segment [Line Items]
Deferred acquisition costs	$ 181,002	$ 161,022	$ 133,891
Reserve for losses and loss expenses	2,996,567	3,243,147	3,047,933
Unearned premiums	966,210	989,229	822,280
Net premiums earned	2,246,889	1,993,055	2,098,795
Net investment income	127,824	100,086	96,089
Losses and loss expenses	977,833	765,015	776,796
Amortization of deferred acquisition costs	410,058	339,467	360,403
Other operating expenses	402,050	362,435	343,638
Net premiums written	2,228,825	2,045,657	2,012,646
Validus Re
Supplementary Insurance Information, by Segment [Line Items]
Deferred acquisition costs	60,459	59,091	52,835
Reserve for losses and loss expenses	1,146,869	1,333,878	1,723,465
Unearned premiums	294,509	305,138	296,115
Net premiums earned	990,213	917,284	1,133,937
Net investment income	74,912	72,633	76,102
Losses and loss expenses	457,976	307,290	430,026
Amortization of deferred acquisition costs	166,387	141,670	180,779
Other operating expenses	88,778	84,478	98,928
Net premiums written	977,671	954,854	1,016,258
AlphaCat
Supplementary Insurance Information, by Segment [Line Items]
Deferred acquisition costs	2,526	1,281	1,377
Reserve for losses and loss expenses	11,013	15,278	35,146
Unearned premiums	24,643	13,060	12,810
Net premiums earned	159,935	123,001	134,164
Net investment income	6,658	4,286	3,882
Losses and loss expenses	657	(16,704)	433
Amortization of deferred acquisition costs	16,327	11,584	13,946
Other operating expenses	39,635	36,799	34,923
Net premiums written	171,588	122,437	130,609
Talbot
Supplementary Insurance Information, by Segment [Line Items]
Deferred acquisition costs	92,095	95,246	88,656
Reserve for losses and loss expenses	1,302,635	1,352,056	1,362,574
Unearned premiums	533,558	552,660	535,659
Net premiums earned	838,091	879,774	830,694
Net investment income	26,414	20,575	18,061
Losses and loss expenses	347,322	423,394	346,337
Amortization of deferred acquisition costs	187,535	187,162	170,738
Other operating expenses	167,679	162,174	146,071
Net premiums written	819,939	909,559	865,779
Western World
Supplementary Insurance Information, by Segment [Line Items]
Deferred acquisition costs	28,622	9,566
Reserve for losses and loss expenses	600,331	613,551
Unearned premiums	130,101	133,185
Net premiums earned	258,650	72,996
Net investment income	21,509	4,523
Losses and loss expenses	171,878	51,035
Amortization of deferred acquisition costs	41,408	3,169
Other operating expenses	40,798	11,256
Net premiums written	259,627	58,807
Corporate & Eliminations
Supplementary Insurance Information, by Segment [Line Items]
Deferred acquisition costs	(2,700)	(4,162)	(8,977)
Reserve for losses and loss expenses	(64,281)	(71,616)	(73,252)
Unearned premiums	(16,601)	(14,814)	(22,304)
Net premiums earned	0	0	0
Net investment income	(1,669)	(1,931)	(1,956)
Losses and loss expenses	0	0	0
Amortization of deferred acquisition costs	(1,599)	(4,118)	(5,060)
Other operating expenses	65,160	67,728	63,716
Net premiums written	$ 0	$ 0	$ 0