Segment information (Segment consolidation) (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2018 USD ($) segments	Mar. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segments		3
Underwriting revenues
Gross premiums written		$ 1,832,456	$ 1,190,857
Reinsurance premiums ceded		(376,294)	(200,106)
Net premiums written		1,456,162	990,751
Change in unearned premiums		(837,220)	(415,375)
Net premiums earned		618,942	575,376
Other insurance related income (loss)		25,496	1,236
Segmental revenues		644,438	576,612
Underwriting deductions
Losses and loss expenses		321,545	269,585
Policy acquisition costs		116,456	111,628
General and administrative expenses		114,726	87,924
Share compensation expenses		9,729	9,491
Total underwriting deductions		562,456	478,628
Segmental (loss) income		81,982	97,984
Net investment return	[1]	9,959	57,586
Other items	[2]	(20,445)	(10,934)
(Income) attributable to AlphaCat investors		(10,862)	(7,503)
Net (income) attributable to noncontrolling interests		(64,712)	(42,572)
Net (loss) income (attributable) available to Validus common shareholders		(4,078)	94,561
Operating Segments | Reinsurance segment
Underwriting revenues
Gross premiums written		765,573	643,141
Reinsurance premiums ceded		(190,194)	(114,446)
Net premiums written		575,379	528,695
Change in unearned premiums		(350,627)	(297,040)
Net premiums earned		224,752	231,655
Other insurance related income (loss)		2	2
Segmental revenues		224,754	231,657
Underwriting deductions
Losses and loss expenses		103,473	80,881
Policy acquisition costs		48,340	43,535
General and administrative expenses		28,915	19,969
Share compensation expenses		2,663	2,623
Total underwriting deductions		183,391	147,008
Segmental (loss) income		41,363	84,649
Net (loss) income (attributable) available to Validus common shareholders		41,363	84,649
Operating Segments | Insurance segment
Underwriting revenues
Gross premiums written		785,795	382,790
Reinsurance premiums ceded		(191,637)	(79,000)
Net premiums written		594,158	303,790
Change in unearned premiums		(294,620)	(24,696)
Net premiums earned		299,538	279,094
Other insurance related income (loss)		2,170	996
Segmental revenues		301,708	280,090
Underwriting deductions
Losses and loss expenses		183,389	186,610
Policy acquisition costs		60,057	61,192
General and administrative expenses		68,050	45,276
Share compensation expenses		2,989	3,373
Total underwriting deductions		314,485	296,451
Segmental (loss) income		(12,777)	(16,361)
Net (loss) income (attributable) available to Validus common shareholders		(12,777)	(16,361)
Operating Segments | Asset management segment
Underwriting revenues
Gross premiums written		286,625	164,926
Reinsurance premiums ceded		0	(6,660)
Net premiums written		286,625	158,266
Change in unearned premiums		(191,973)	(93,639)
Net premiums earned		94,652	64,627
Other insurance related income (loss)		28,080	5,161
Segmental revenues		122,732	69,788
Underwriting deductions
Losses and loss expenses		34,683	2,094
Policy acquisition costs		8,059	6,901
General and administrative expenses		10,208	9,641
Share compensation expenses		41	82
Total underwriting deductions		52,991	18,718
Segmental (loss) income		69,741	51,070
Net investment return	[1]	12,735	4,749
Other items	[2]	362	388
(Income) attributable to AlphaCat investors		(10,862)	(7,503)
Net (income) attributable to noncontrolling interests		(64,712)	(42,572)
Net (loss) income (attributable) available to Validus common shareholders		7,264	6,132
Corporate & Investments
Underwriting revenues
Gross premiums written		0	0
Reinsurance premiums ceded		0	0
Net premiums written		0	0
Change in unearned premiums		0	0
Net premiums earned		0	0
Other insurance related income (loss)		0	0
Segmental revenues		0	0
Underwriting deductions
Losses and loss expenses		0	0
Policy acquisition costs		0	0
General and administrative expenses		12,309	17,961
Share compensation expenses		4,036	3,413
Total underwriting deductions		16,345	21,374
Segmental (loss) income		(16,345)	(21,374)
Net investment return	[1]	(2,776)	52,837
Other items	[2]	(20,807)	(11,322)
Net (loss) income (attributable) available to Validus common shareholders		(39,928)	20,141
Eliminations
Underwriting revenues
Gross premiums written		(5,537)	0
Reinsurance premiums ceded		5,537	0
Net premiums written		0	0
Change in unearned premiums		0	0
Net premiums earned		0	0
Other insurance related income (loss)		(4,756)	(4,923)
Segmental revenues		(4,756)	(4,923)
Underwriting deductions
Losses and loss expenses		0	0
Policy acquisition costs		0	0
General and administrative expenses		(4,756)	(4,923)
Share compensation expenses		0	0
Total underwriting deductions		(4,756)	(4,923)
Segmental (loss) income		0	0
Net investment return	[1]	0	0
Other items	[2]	0	0
Net (loss) income (attributable) available to Validus common shareholders		$ 0	$ 0

[1] Net investment return includes net investment income, net realized and change in net unrealized gains (losses) on investments and income (loss) from investment affiliates.

[2] Other items includes finance expenses, transaction expenses, dividends on preferred shares, tax benefit (expense), foreign exchange gains (losses), income (loss) from operating affiliate and other income (loss).