Validus 10-Q 2 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	VALIDUS HOLDINGS LTD
Entity Central Index Key	1,348,259
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		79,329,028

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Fixed maturity investments trading, at fair value (amortized cost: 2018—$5,874,140; 2017—$5,876,261)	$ 5,803,022	$ 5,858,348
Short-term investments trading, at fair value (amortized cost: 2018—$3,638,995; 2017—$3,381,714)	3,638,940	3,381,757
Other investments, at fair value (cost: 2018—$331,950; 2017—$330,416)	357,246	355,218
Investments in investment affiliates, equity method (cost: 2018—$75,302; 2017—$61,944)	113,471	100,137
Cash and cash equivalents	672,173	754,990
Restricted cash	302,277	394,663
Total investments and cash	10,887,129	10,845,113
Premiums receivable	1,865,460	939,487
Deferred acquisition costs	309,825	213,816
Prepaid reinsurance premiums	390,900	132,938
Securities lending collateral	4,210	2,717
Loss reserves recoverable	979,944	1,233,997
Paid losses recoverable	59,892	46,873
Income taxes recoverable	7,705	9,044
Deferred tax asset	56,739	52,467
Receivable for investments sold	31,512	12,182
Intangible assets	169,168	171,411
Goodwill	229,573	229,573
Accrued investment income	29,621	29,096
Other assets	578,964	508,165
Total assets	15,600,642	14,426,879
Liabilities
Reserve for losses and loss expenses	4,632,629	4,831,390
Unearned premiums	2,242,368	1,147,186
Reinsurance balances payable	398,861	331,645
Securities lending payable	4,210	2,717
Deferred tax liability	3,633	4,600
Payable for investments purchased	85,946	74,496
Accounts payable and accrued expenses	520,916	1,225,875
Notes payable to AlphaCat investors	1,268,194	1,108,364
Senior notes payable	245,614	245,564
Debentures payable	539,572	539,158
Total liabilities	9,941,943	9,510,995
Commitments and contingent liabilities
Redeemable noncontrolling interests	1,423,110	1,004,094
Shareholders' equity
Preferred shares (Issued and Outstanding: 2018—16,000; 2017—16,000)	400,000	400,000
Common shares (Issued: 2018—162,003,969; 2017—161,994,491; Outstanding: 2018—79,329,028; 2017—79,319,550)	28,351	28,349
Treasury shares (2018—82,674,941; 2017—82,674,941)	(14,468)	(14,468)
Additional paid-in capital	824,356	814,641
Accumulated other comprehensive income (loss)	9,405	(22,192)
Retained earnings	2,653,588	2,688,742
Total shareholders' equity available to Validus	3,901,232	3,895,072
Noncontrolling interests	334,357	16,718
Total shareholders' equity	4,235,589	3,911,790
Total liabilities, noncontrolling interests and shareholders’ equity	$ 15,600,642	$ 14,426,879

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Assets
Fixed maturities, at amortized cost or cost	$ 5,874,140	$ 5,876,261
Short-term investments, at amortized cost or cost	3,638,995	3,381,714
Other investments, at amortized cost or cost	331,950	330,416
Investments in investment affiliates, at cost	$ 75,302	$ 61,944
Preferred shares - Shareholders' Equity
Preferred shares, shares issued	16,000	16,000
Preferred shares, shares outstanding	16,000	16,000
Common Shares - Shareholders' Equity
Common shares, shares issued	162,003,969	161,994,491	161,285,411	161,279,976
Common shares, shares outstanding	79,329,028	79,319,550	79,137,590
Treasury shares, common shares	82,674,941	82,674,941	82,147,821

Consolidated Statements of Inco

Consolidated Statements of Income and Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
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
Net investment income	52,072	40,214
Net realized gains (losses) on investments	2,200	(1,164)
Change in net unrealized (losses) gains on investments	(57,381)	13,348
Income from investment affiliates	13,068	5,188
Other insurance related income and other income	25,540	1,330
Foreign exchange gains	525	1,569
Total revenues	654,966	635,861
Expenses
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
Finance expenses	14,263	13,943
Transaction expenses	7,756	0
Total expenses	584,475	492,571
Income before taxes and (income) attributable to AlphaCat investors	70,491	143,290
Tax benefit	6,833	3,549
(Income) attributable to AlphaCat investors	(10,862)	(7,503)
Net income	66,462	139,336
Net (income) attributable to noncontrolling interests	(64,712)	(42,572)
Net income available to Validus	1,750	96,764
Dividends on preferred shares	(5,828)	(2,203)
Net (loss) income (attributable) available to Validus common shareholders	(4,078)	94,561
Comprehensive (loss) income
Net income	66,462	139,336
Other comprehensive income (loss)
Change in foreign currency translation adjustments	1,837	597
Change in minimum pension liability, net of tax	(38)	68
Change in fair value of cash flow hedge	28,763	98
Other comprehensive income (loss)	30,562	763
Comprehensive (income) attributable to noncontrolling interests	(64,712)	(42,572)
Comprehensive income available to Validus	$ 32,312	$ 97,527
Earnings per common share
Basic (loss) earnings per share (attributable) available to Validus common shareholders	$ (0.05)	$ 1.19
(Loss) earnings per diluted share (attributable) available to Validus common shareholders	(0.05)	1.17
Cash dividends declared per common share	$ 0.38	$ 0.38
Weighted average number of common shares and common share equivalents outstanding:
Basic (in shares)	79,325,688	79,133,671
Diluted (in shares)	79,325,688	80,739,142

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Preferred shares	Common shares	Treasury shares	Additional paid-in capital	Accumulated other comprehensive loss	Retained earnings
Balance - Beginning of period at Dec. 31, 2016		$ 150,000	$ 28,224	$ (14,376)	$ 821,023	$ (23,216)	$ 2,876,636
Common shares issued (redeemed), net			1		(168)
Share compensation expenses					9,491
Other comprehensive (loss) income	$ 763					763
Amounts reclassified from accumulated other comprehensive loss	0
Net income	139,336						139,336
Net (income) attributable to noncontrolling interests	(42,572)						(42,572)
Dividends on common shares							(31,063)
Dividends on preferred shares							(2,203)
Balance - End of period at Mar. 31, 2017	3,911,876	150,000	28,225	(14,376)	830,346	(22,453)	2,940,134
Noncontrolling interests at Mar. 31, 2017	330,597
Total shareholders' equity at Mar. 31, 2017	4,242,473
Balance - Beginning of period at Dec. 31, 2017	3,895,072	400,000	28,349	(14,468)	814,641	(22,192)	2,688,742
Common shares issued (redeemed), net			2		(14)
Share compensation expenses					9,729
Other comprehensive (loss) income	30,562					30,562
Amounts reclassified from accumulated other comprehensive loss						1,035
Net income	66,462						66,462
Net (income) attributable to noncontrolling interests	(64,712)						(64,712)
Dividends on common shares							(31,076)
Dividends on preferred shares							(5,828)
Balance - End of period at Mar. 31, 2018	3,901,232	$ 400,000	$ 28,351	$ (14,468)	$ 824,356	$ 9,405	$ 2,653,588
Noncontrolling interests at Mar. 31, 2018	334,357
Total shareholders' equity at Mar. 31, 2018	$ 4,235,589

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows provided by (used in) operating activities
Net income	$ 66,462	$ 139,336
Adjustments to reconcile net income to cash provided by (used in) operating activities:
Share compensation expenses	9,729	9,491
Amortization of discount on senior notes	27	27
(Income) from investment and operating affiliates	(13,068)	(5,188)
Net realized and change in net unrealized losses (gains) on investments	55,181	(12,184)
Amortization of intangible assets	2,243	1,416
Foreign exchange (gains) included in net income	(9,885)	(4,938)
Amortization of premium on fixed maturities	3,899	3,536
Change in:
Premiums receivable	(924,817)	(488,653)
Deferred acquisition costs	(96,009)	(82,953)
Prepaid reinsurance premiums	(257,962)	(121,050)
Loss reserves recoverable	255,701	(20,743)
Paid losses recoverable	(13,069)	(2,619)
Reserve for losses and loss expenses	(207,632)	53,436
Unearned premiums	1,095,182	536,425
Reinsurance balances payable	66,720	63,070
Other operational balance sheet items, net	13,240	(50,610)
Net cash provided by operating activities	45,942	17,799
Cash flows provided by (used in) investing activities
Proceeds on sales of fixed maturity investments	785,662	743,631
Proceeds on maturities of fixed maturity investments	166,651	123,269
Purchases of fixed maturity investments	(963,990)	(676,349)
Purchases (sales) of short-term investments, net	(257,214)	11,030
Purchases of other investments, net	(1,137)	(34,295)
Decrease (increase) in securities lending collateral	(1,493)	(607)
(Investments in) distributions from investment affiliates, net	(266)	10,922
Net cash (used in) provided by investing activities	(271,787)	177,601
Cash flows provided by (used in) financing activities
Net proceeds on issuance of notes payable to AlphaCat investors	155,966	73,048
Redemption of common shares, net	(12)	(167)
Dividends paid on preferred shares	(5,828)	(2,203)
Dividends paid on common shares	(31,032)	(30,092)
(Decrease) increase in securities lending payable	1,493	607
Third party investment in redeemable noncontrolling interests	385,300	103,699
Third party redemption of redeemable noncontrolling interests	(173,986)	(68,296)
Third party investment in noncontrolling interests	281,300	154,980
Third party distributions of noncontrolling interests	0	(62,770)
Third party subscriptions deployed in AlphaCat Funds and Sidecars	(578,666)	(144,452)
Net cash provided by financing activities	34,535	24,354
Effect of foreign currency rate changes on cash and cash equivalents and restricted cash	16,107	5,798
Net (decrease) increase in cash and cash equivalents and restricted cash	(175,203)	225,552
Cash and cash equivalents and restricted cash—beginning of period	1,149,653	490,932
Cash and cash equivalents and restricted cash—end of period	974,450	716,484
Supplemental disclosure of cash flow information:
Taxes paid during the period	460	16
Interest paid during the period	$ 19,068	$ 19,073

Basis of preparation and consol

Basis of preparation and consolidation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation and consolidation	Basis of preparation and consolidation These unaudited Consolidated Financial Statements (the “Consolidated Financial Statements”) have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 in Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In addition, the year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by U.S. GAAP. This Quarterly Report on Form 10-Q should be read in conjunction with the financial statements and related notes included in Validus Holdings, Ltd.’s (the “Company”) Annual Report on Form 10-K for the year ended December 31, 2017 , as filed with the U.S. Securities and Exchange Commission (the “SEC”). During the fourth quarter of 2017, the Company changed its reportable segments to “Reinsurance,” “Insurance,” and “Asset Management.” The change in reportable segments and primary lines of business had no impact on the Company’s historical consolidated financial positions, results of operations or cash flows as previously reported. Where applicable, all prior periods presented have been reclassified to conform to this new presentation. The Company consolidates in these Consolidated Financial Statements the results of operations and financial position of every voting interest entity (“VOE”) in which the Company has a controlling financial interest and variable interest entity (“VIE”) in which the Company is considered to be the primary beneficiary. The consolidation assessment, including the determination as to whether an entity qualifies as a VIE or VOE, depends on the facts and circumstances surrounding each entity. In the opinion of management, these unaudited Consolidated Financial Statements reflect all adjustments (including normal recurring adjustments) considered necessary for a fair statement of the Company’s financial position and results of operations as at the end of and for the periods presented. All significant intercompany accounts and transactions have been eliminated. The results of operations for any interim period are not necessarily indicative of the results for a full year. The preparation of these Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. While the amounts included in the Consolidated Financial Statements reflect management’s best estimates and assumptions, actual results could differ from those estimates. The Company’s principal estimates include: • the reserve for losses and loss expenses; • the premium written on a line slip or proportional basis; • the valuation of goodwill and intangible assets; • the loss reserves recoverable, including the provision for uncollectible amounts; and • the valuation of invested assets and other financial instruments. The term “ASC” used in these notes refers to Accounting Standard Codification issued by the United States Financial Accounting Standards Board (the “FASB”).

Recent accounting pronouncement

Recent accounting pronouncements	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent accounting pronouncements	Recent accounting pronouncements Accounting Standards Adopted in 2018 In May 2014, the FASB issued Accounting Standards Updated (“ASU”) 2014-09, “Revenue from Contracts with Customers (Topic 606).” The guidance in this ASU affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets, unless those contracts are within the scope of other standards (for example, insurance contracts or lease contracts). The core principal of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In March and April 2016, the FASB issued ASU 2016-08, “Revenue from Contracts with Customers (Topic 606) - Principal versus Agent Considerations (Reporting Revenue Gross versus Net)” and ASU 2016-10, “Revenue from Contracts with Customers (Topic 606) - Identifying Performance Obligations and Licensing.” The amendments in these ASUs clarify the implementation guidance within ASU 2014-09 on principal versus agent considerations and the aspects of identifying performance obligations, respectively, while retaining the related principals in those areas. In May 2016, the FASB issued ASU 2016-12, “Revenue from Contracts with Customers (Topic 606) - Narrow-Scope Improvements and Practical Expedients.” The amendments in this ASU do not change the core principal of the guidance in Topic 606. Rather, the amendments provide clarifying guidance in a few narrow areas and add practical expedients to reduce the potential for diversity in practice as well as the cost and complexity of applying the guidance. In December 2016, the FASB issued ASU 2016-20, “Technical Corrections and Improvements to Topic 606 - Revenue from Contracts with Customers.” The amendments in this ASU affect narrow aspects of the guidance issued in ASU 2014-09. The amendments in these ASUs became effective for the Company on January 1, 2018. This guidance impacts the timing of performance fee recognition by AlphaCat Managers Ltd. (“AlphaCat Managers”). Previously, the performance fees were recognized by AlphaCat Managers monthly, on a seasonal basis, in line with the underlying insurance contract portfolio of the AlphaCat sidecars and higher risk ILS funds it manages. However, upon adoption of this guidance, performance fees are now only recognized when it is probable that a significant reversal of the amount of cumulative revenue recognized will not occur. While performance fees are variable and dependent on the results of these entities, the adoption of this guidance did not have a material impact on the results of the Company. In January 2016, the FASB issued ASU 2016-01, “Financial Instruments - Overall (Subtopic 825-10) - Recognition and measurement of financial assets and financial liabilities.” The amendments in this ASU address certain aspects of recognition, measurement and disclosure of financial instruments. The amendments in this ASU became effective for the Company on January 1, 2018. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230) - Classification of Certain Cash Receipts and Cash Payments.” This ASU is directed at reducing diversity in practice and addresses eight specific issues in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The amendments in this ASU became effective for the Company on January 1, 2018. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In October 2016, the FASB issued ASU 2016-16, “Income Taxes (Topic 740) - Intra- Entity Transfers of Assets Other Than Inventory,” This ASU aims to improve the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. Prior to the effective date of this ASU, U.S. GAAP prohibited the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party. The ASU requires that an entity recognize the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. This ASU does not include new disclosure requirements; however, existing disclosure requirements might be applicable when accounting for the current and deferred income taxes for an intra-entity transfer of an asset other than inventory. The amendments in this ASU became effective for the Company on January 1, 2018. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In January 2017, the FASB issues ASU 2017-01, “Business Combinations (Topic 805) - Clarifying the Definition of a Business.” The amendments in this ASU clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in this ASU became effective for the Company on January 1, 2018. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In May 2017, the FASB issues ASU 2017-09, “Compensation - Stock Compensation (Topic 718).” This ASU is directed at reducing diversity in practice when applying the accounting guidance to a change in the terms or conditions of a share-based payment award. The amendments in this ASU became effective for the Company on January 1, 2018. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements.

Business combinations

Business combinations	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Business combination	Business combinations American International Group, Inc. (“AIG”) On January 21, 2018, the Company entered into a definitive agreement and plan of merger (the “Merger Agreement”) with AIG. The Merger Agreement provides that, subject to the satisfaction or waiver of certain conditions set forth therein, the Company will merge with an existing AIG subsidiary in accordance with the Bermuda Companies Act (the “Merger”), with the Company surviving the Merger as a wholly–owned subsidiary of AIG (the “Surviving Company”). Pursuant to the Merger Agreement, at the effective time of the Merger, holders of the Company’s common shares will be entitled to receive consideration of $68.00 in cash per common share. Each of the Company’s issued and outstanding Series A and Series B Preferred Shares will remain issued and outstanding as a “Series A Preferred Share” and “Series B Preferred Share,” respectively, of the Surviving Company. The Merger is expected to close in mid-2018, subject to regulatory approvals and other customary closing conditions. The Merger Agreement permits the Company to pay out regular quarterly cash dividends not to exceed $0.38 per common share, with its quarterly dividend for the second fiscal quarter for 2018 to be paid prior to the closing of the Merger even if such closing occurs prior to the regular record or payment date of such dividend. Crop Risk Services (“CRS”) On May 1, 2017, Western World, a wholly–owned subsidiary of the Company acquired all of the outstanding capital stock of CRS for an aggregate purchase price of $185,576 in cash. CRS is a primary crop insurance managing general agent (“MGA”) based in Decatur, Illinois with 1,170 agents across 36 states. CRS does not have insurance licenses of its own, but acts solely as an MGA in that it can produce business for any properly licensed entity on a commission basis. Concurrent with closing of the transaction, Stratford, a wholly–owned subsidiary of Western World, was granted the required licenses to write crop insurance in the United States and executed several agreements to transfer the related agriculture book of business to Stratford. The CRS acquisition was undertaken to expand the Company’s presence in U.S. primary specialty lines. For segmental reporting purposes, the results of CRS’ operations, including the related agricultural book of business have been included within the Insurance segment in the Consolidated Financial Statements from the date of acquisition. For further information regarding the acquisition of CRS please refer to Note 5, “Business combinations,” included within the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 .

Investments

Investments	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Investments	Investments Managed investments represent assets governed by the Company’s investment policy statement (“IPS”) whereas, non-managed investments represent assets held in support of consolidated AlphaCat VIEs which are not governed by the Company’s IPS. Refer to Note 6 , “Variable interest entities,” for further details. The amortized cost (or cost) and fair value of the Company’s investments as at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 December 31, 2017 Amortized Cost or Cost Fair Value Amortized Fair Value Managed investments U.S. government and government agency $ 598,080 $ 589,161 $ 733,510 $ 727,397 Non-U.S. government and government agency 318,542 318,345 310,845 312,239 U.S. states, municipalities and political subdivisions 186,551 184,964 201,347 201,303 Agency residential mortgage-backed securities 992,087 968,258 984,387 978,049 Non-agency residential mortgage-backed securities 43,522 43,487 40,264 40,373 U.S. corporate 1,553,311 1,534,805 1,531,498 1,533,395 Non-U.S. corporate 417,264 415,156 420,522 422,249 Bank loans 475,154 468,815 450,320 442,951 Asset-backed securities 744,051 741,712 657,234 658,303 Commercial mortgage-backed securities 325,058 318,392 315,002 312,395 Total fixed maturities 5,653,620 5,583,095 5,644,929 5,628,654 Short-term investments 188,306 188,251 229,968 230,011 Other investments Hedge funds 6,954 15,758 6,954 15,774 Private equity investments 64,424 79,774 63,684 78,407 Fixed income investment funds 199,802 200,944 203,167 204,426 Overseas deposits 60,770 60,770 56,611 56,611 Total other investments 331,950 357,246 330,416 355,218 Investments in investment affiliates (a) 75,302 113,471 61,944 100,137 Total managed investments $ 6,249,178 $ 6,242,063 $ 6,267,257 $ 6,314,020 Non-managed investments Catastrophe bonds $ 220,520 $ 219,927 $ 231,332 $ 229,694 Short-term investments 3,450,689 3,450,689 3,151,746 3,151,746 Total non-managed investments 3,671,209 3,670,616 3,383,078 3,381,440 Total investments $ 9,920,387 $ 9,912,679 $ 9,650,335 $ 9,695,460 (a) The Company’s investments in investment affiliates have been treated as equity method investments with the corresponding gains and losses recorded in income as “Income from investment affiliates.” (a) Fixed maturity investments The following table sets forth certain information regarding Standard & Poor’s credit quality ratings (or an equivalent rating with another recognized rating agency) of the Company’s fixed maturity investments as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Fair Value % of Total Fair Value % of Total Managed fixed maturities AAA $ 2,648,321 45.7 % $ 2,715,074 46.4 % AA 419,695 7.2 % 442,397 7.6 % A 1,159,233 20.0 % 1,137,795 19.4 % BBB 830,866 14.3 % 828,392 14.1 % Total investment grade managed fixed maturities 5,058,115 87.2 % 5,123,658 87.5 % BB 170,818 2.9 % 168,967 2.9 % B 240,099 4.1 % 237,131 4.0 % CCC 21,783 0.4 % 18,217 0.3 % NR 92,280 1.6 % 80,681 1.4 % Total non-investment grade managed fixed maturities 524,980 9.0 % 504,996 8.6 % Total managed fixed maturities $ 5,583,095 96.2 % $ 5,628,654 96.1 % Non-managed catastrophe bonds BB 21,607 0.4 % 22,110 0.3 % B 2,379 — % 3,265 0.1 % NR 195,941 3.4 % 204,319 3.5 % Total non-investment grade non-managed catastrophe bonds 219,927 3.8 % 229,694 3.9 % Total non-managed catastrophe bonds 219,927 3.8 % 229,694 3.9 % Total fixed maturities $ 5,803,022 100.0 % $ 5,858,348 100.0 % The amortized cost and fair values for the Company’s fixed maturity investments held at March 31, 2018 and December 31, 2017 are shown below by contractual maturity. Actual maturity may differ from contractual maturity due to prepayment rights associated with certain investments. March 31, 2018 December 31, 2017 Amortized Cost or Cost Fair Value Amortized Cost or Cost Fair Value Managed fixed maturities Due in one year or less $ 346,118 $ 344,749 $ 343,360 $ 343,541 Due after one year through five years 2,453,565 2,424,185 2,527,018 2,513,620 Due after five years through ten years 560,679 554,188 577,347 577,109 Due after ten years 188,540 188,124 200,317 205,264 3,548,902 3,511,246 3,648,042 3,639,534 Asset-backed and mortgage-backed securities 2,104,718 2,071,849 1,996,887 1,989,120 Total managed fixed maturities $ 5,653,620 $ 5,583,095 $ 5,644,929 $ 5,628,654 Non-managed catastrophe bonds Due in one year or less $ 67,370 $ 67,926 $ 88,797 $ 88,367 Due after one year through five years 147,400 146,238 140,035 138,844 Due after five years through ten years 5,750 5,763 2,500 2,483 Total non-managed catastrophe bonds 220,520 219,927 231,332 229,694 Total fixed maturities $ 5,874,140 $ 5,803,022 $ 5,876,261 $ 5,858,348 (b) Other investments The following tables set forth certain information regarding the Company’s other investment portfolio as at March 31, 2018 and December 31, 2017 : March 31, 2018 Fair Value Investments with redemption restrictions Investments without redemption restrictions Redemption frequency (a) Redemption notice period (a) Hedge funds $ 15,758 $ 15,758 $ — Private equity investments 79,774 79,774 — Fixed income investment funds 200,944 200,944 — Overseas deposits 60,770 60,770 — Total other investments $ 357,246 $ 357,246 $ — December 31, 2017 Fair Value Investments with redemption restrictions Investments without redemption restrictions Redemption frequency (a) Redemption notice period (a) Hedge funds 15,774 15,774 — Private equity investments 78,407 78,407 — Fixed income investment funds 204,426 200,532 3,894 Daily Daily to 2 days Overseas deposits 56,611 56,611 — Total other investments $ 355,218 $ 351,324 $ 3,894 (a) The redemption frequency and notice periods only apply to investments without redemption restrictions. Other investments include investments in various funds and pooled investment schemes. These alternative investments employ various investment strategies primarily involving, but not limited to, investments in collateralized obligations, fixed income securities, private equities, distressed debt and equity securities. Certain debt-like investments totaling $193,053 ( December 31, 2017 : $186,734 ) are either rated or consist of underlying securities or instruments which carry credit ratings issued by nationally recognized statistical rating organizations. Other equity-like investments totaling $164,193 ( December 31, 2017 : $168,484 ) are unrated given the nature of their underlying assets, such as private equity investments, and as such do not carry credit ratings. Certain securities included in other investments are subject to redemption restrictions. Distributions from these funds will be received as the underlying investments of the funds are liquidated. Currently, it is not known to the Company when these underlying assets will be sold by their investment managers; however, it is estimated that the majority of the underlying assets of the investments will liquidate over five to ten -year periods from inception of the funds. Furthermore, the underlying investments held in the overseas deposit funds are liquid and will generally trade freely in an open market. However, the Company’s ability to withdraw from the overseas deposit funds is restricted by annual and quarterly funding and release processes for Lloyd’s market participants. The Company’s maximum exposure to any of these alternative investments is limited to the invested amounts and any remaining capital commitments. Refer to Note 15 , “Commitments and contingencies,” for further details. As at March 31, 2018 , the Company does not have any plans to sell any of the other investments listed above. (c) Investments in investment affiliates Included in the Company’s managed investment portfolio as at March 31, 2018 are investments in Aquiline Financial Services Fund II L.P. (“Aquiline II”), Aquiline Financial Services Fund III L.P. (“Aquiline III”), Aquiline Technology Growth Fund L.P. (“Aquiline Tech”) and Aquiline Armour Co-Invest L.P. (“Aquiline Armour”) (collectively the “Aquiline partnerships”). For further information regarding the Company’s Aquiline partnerships refer to Note 7(c), “Investments in investment affiliates,” included within the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . The following table presents a reconciliation of the Company’s beginning and ending investments in investment affiliates for three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Investment affiliates, beginning of year $ 100,137 $ 100,431 Net capital contributions (distributions) 266 (10,922 ) Income from investment affiliates 13,068 5,188 Investment affiliates, end of year $ 113,471 $ 94,697 As at March 31, 2018 , the Company’s total unfunded investment commitment to the Aquiline partnerships was $107,386 ( December 31, 2017 : $125,996 ). The following table presents the Company’s investments in the Aquiline partnerships as at March 31, 2018 and December 31, 2017 : March 31, 2018 Investment at cost Voting ownership % Equity ownership % Carrying value Aquiline II $ 33,008 — % 8.1 % $ 49,208 Aquiline III 24,737 — % 9.0 % 47,114 Aquiline Tech 3,858 — % 10.6 % 3,450 Aquiline Armour 13,699 — % 15.2 % 13,699 Total investments in investment affiliates $ 75,302 $ 113,471 December 31, 2017 Investment at cost Voting ownership % Equity ownership % Carrying value Aquiline II $ 33,349 — % 8.1 % $ 51,914 Aquiline III 24,737 — % 9.0 % 44,733 Aquiline Tech 3,858 — % 10.6 % 3,490 Total investments in investment affiliates $ 61,944 $ 100,137 (d) Net investment income Net investment income was derived from the following sources: Three Months Ended March 31, 2018 2017 Managed investments Fixed maturities and short-term investments $ 37,769 $ 31,671 Other investments 4,223 6,870 Cash and cash equivalents and restricted cash 1,139 610 Securities lending income 3 13 Total gross investment income 43,134 39,164 Investment expenses (3,343 ) (2,972 ) Total managed net investment income $ 39,791 $ 36,192 Non managed investments Fixed maturities and short-term investments $ 4,148 $ 3,060 Cash and cash equivalents and restricted cash 8,133 962 Total non-managed net investment income 12,281 4,022 Total net investment income $ 52,072 $ 40,214 Net investment income from other investments includes distributed and undistributed net income from certain fixed income investment funds. (e) Net realized gains (losses) and change in net unrealized (losses) gains on investments The following table sets forth an analysis of net realized gains (losses) and the change in net unrealized (losses) gains on investments: Three Months Ended March 31, 2018 2017 Managed investments Gross realized gains $ 6,830 $ 2,690 Gross realized (losses) (5,688 ) (5,582 ) Net realized gains (losses) on investments 1,142 (2,892 ) Change in net unrealized (losses) gains on investments (56,777 ) 14,349 Total net realized and change in net unrealized (losses) gains on managed investments $ (55,635 ) $ 11,457 Non-managed investments Gross realized gains $ 1,235 $ 1,728 Gross realized (losses) (177 ) — Net realized gains on investments 1,058 1,728 Change in net unrealized (losses) on investments (604 ) (1,001 ) Total net realized and change in net unrealized gains on non-managed investments 454 727 Total net realized and change in net unrealized (losses) gains on total investments $ (55,181 ) $ 12,184 (f) Pledged investments and cash As at March 31, 2018 , the Company had $6,120,705 ( December 31, 2017 : $5,853,744 ) of cash and cash equivalents, restricted cash, short-term investments and fixed maturity investments that were pledged during the normal course of business. Of those, $6,092,111 were held in trust ( December 31, 2017 : $5,789,081 ). Pledged assets are generally for the benefit of the Company’s cedants and policyholders, to support AlphaCat’s fully collateralized reinsurance transactions, as collateral for derivative instruments and to facilitate the accreditation of Validus Reinsurance, Ltd. (“Validus Re”), Validus Reinsurance (Switzerland) Ltd. (“Validus Re Swiss”) and Lloyd’s Syndicate 1183 (the “Talbot Syndicate”) as alien (re)insurers by certain regulators. In addition, the Company has pledged cash and investments as collateral under the Company’s credit facilities in the amount of $540,239 ( December 31, 2017 : $576,864 ). For further details on the credit facilities, refer to Note 13 “Debt and financing arrangements.”

Fair value measurements

Fair value measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair value measurements	Fair value measurements (a) Classification within the fair value hierarchy Fair value is defined as the price to sell an asset or transfer a liability in an orderly transaction between market participants. Under U.S. GAAP, a company must determine the appropriate level in the fair value hierarchy for each fair value measurement. The fair value hierarchy prioritizes the inputs, which refer broadly to assumptions market participants would use in pricing an asset or liability, into three levels. It gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The level in the fair value hierarchy within which a fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement in its entirety. The three levels of the fair value hierarchy are described below: Level 1 - Fair values are measured based on unadjusted quoted prices in active markets for identical assets or liabilities that we have the ability to access. Level 2 - Fair values are measured based on quoted prices in active markets for similar assets or liabilities, quoted prices for identical assets or liabilities in inactive markets, or for which significant inputs are observable (e.g., interest rates, yield curves, prepayment speeds, default rates, loss severities, etc.) or can be corroborated by observable market data. Level 3 - Fair values are measured based on unobservable inputs that reflect the Company’s own judgments about assumptions where there is little, if any, market activity for that asset or liability that market participants might use. The availability of observable inputs can vary from financial instrument to financial instrument and is affected by a wide variety of factors including, for example, the type of financial instrument, whether the financial instrument is new and not yet established in the marketplace, and other characteristics particular to the instrument. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires significantly more judgment. Accordingly, the degree of judgment exercised by management in determining fair value is greatest for instruments categorized in Level 3. In periods of market dislocation, the observability of prices and inputs may be reduced for many instruments. This may lead the Company to change the selection of the valuation technique (for example, from market to cash flow approach) or to use multiple valuation techniques to estimate the fair value of a financial instrument. These circumstances could cause an instrument to be reclassified between levels within the fair value hierarchy. At March 31, 2018 , the Company’s investments were allocated between Levels 1, 2 and 3 as follows: Level 1 Level 2 Level 3 Fair value based on NAV practical expedient (a) Total Managed investments U.S. government and government agency $ — $ 589,161 $ — $ — $ 589,161 Non-U.S. government and government agency — 318,345 — — 318,345 U.S. states, municipalities and political subdivisions — 184,964 — — 184,964 Agency residential mortgage-backed securities — 968,258 — — 968,258 Non-agency residential mortgage-backed securities — 43,487 — — 43,487 U.S. corporate — 1,534,805 — — 1,534,805 Non-U.S. corporate — 415,156 — — 415,156 Bank loans — 241,312 227,503 — 468,815 Asset-backed securities — 639,896 101,816 — 741,712 Commercial mortgage-backed securities — 318,392 — — 318,392 Total fixed maturities — 5,253,776 329,319 — 5,583,095 Short-term investments 175,526 12,725 — — 188,251 Other investments Hedge funds — — — 15,758 15,758 Private equity investments — — — 79,774 79,774 Fixed income investment funds — 9,458 17,933 173,553 200,944 Overseas deposits — — — 60,770 60,770 Total other investments — 9,458 17,933 329,855 357,246 Investments in investment affiliates (b) — — — — 113,471 Total managed investments $ 175,526 $ 5,275,959 $ 347,252 $ 329,855 $ 6,242,063 Non-managed investments Catastrophe bonds $ — $ 154,230 $ 65,697 $ — $ 219,927 Short-term investments 3,450,689 — — — 3,450,689 Total non-managed investments 3,450,689 154,230 65,697 — 3,670,616 Total investments $ 3,626,215 $ 5,430,189 $ 412,949 $ 329,855 $ 9,912,679 (a) In accordance with ASC Topic 820 “Fair Value Measurements,” investments measured at fair value using the net asset value (“NAV”) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. (b) In accordance with ASC Topic 825 “Financial Instruments,” the Company’s investments in investment affiliates have not been classified in the fair value hierarchy. At December 31, 2017 , the Company’s investments were allocated between Levels 1, 2 and 3 as follows: Level 1 Level 2 Level 3 Fair value based on NAV practical expedient (a) Total Managed investments U.S. government and government agency $ — $ 727,397 $ — $ — $ 727,397 Non-U.S. government and government agency — 312,239 — — 312,239 U.S. states, municipalities and political subdivisions — 201,303 — — 201,303 Agency residential mortgage-backed securities — 978,049 — — 978,049 Non-agency residential mortgage-backed securities — 40,373 — — 40,373 U.S. corporate — 1,533,395 — — 1,533,395 Non-U.S. corporate — 422,249 — — 422,249 Bank loans — 232,886 210,065 — 442,951 Asset-backed securities — 554,490 103,813 — 658,303 Commercial mortgage-backed securities — 312,395 — — 312,395 Total fixed maturities — 5,314,776 313,878 — 5,628,654 Short-term investments 198,054 31,957 — — 230,011 Other investments Hedge funds — — — 15,774 15,774 Private equity investments — — — 78,407 78,407 Fixed income investment funds — 13,351 17,404 173,671 204,426 Overseas deposits — — — 56,611 56,611 Total other investments — 13,351 17,404 324,463 355,218 Investments in investment affiliates (b) — — — — 100,137 Total managed investments $ 198,054 $ 5,360,084 $ 331,282 $ 324,463 $ 6,314,020 Non-managed investments Catastrophe bonds $ — $ 152,233 $ 77,461 $ — $ 229,694 Short-term investments 3,151,746 — — — 3,151,746 Total non-managed investments 3,151,746 152,233 77,461 — 3,381,440 Total investments $ 3,349,800 $ 5,512,317 $ 408,743 $ 324,463 $ 9,695,460 (a) In accordance with ASC Topic 820 “Fair Value Measurements,” investments measured at fair value using the net asset value (“NAV”) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. (b) In accordance with ASC Topic 825 “Financial Instruments,” the Company’s investments in investment affiliates have not been classified in the fair value hierarchy. At March 31, 2018 , managed Level 3 investments totaled $347,252 ( December 31, 2017 : $331,282 ), representing 5.6% ( December 31, 2017 : 5.2% ) of total managed investments. (b) Valuation techniques There have been no material changes in the Company’s valuation techniques during the periods presented in these Consolidated Financial Statements. The following methods and assumptions were used in estimating the fair value of each class of financial instrument recorded in the Consolidated Balance Sheets. Fixed maturity investments In general, valuation of the Company’s fixed maturity investment portfolio is provided by pricing services, such as index providers and pricing vendors, as well as broker quotations. The pricing vendors provide valuations for a high volume of liquid securities that are actively traded. For securities that do not trade on an exchange, the pricing services generally utilize market data and other observable inputs in matrix pricing models to determine month end prices. Prices are generally verified using third party data. Index providers generally utilize centralized trade reporting networks, available market makers and statistical techniques. In general, broker-dealers value securities through their trading desks based on observable inputs. The methodologies include mapping securities based on trade data, bids or offers, observed spreads, and performance on newly issued securities. Broker-dealers also determine valuations by observing secondary trading of similar securities. Prices obtained from broker quotations are considered non-binding, however they are based on observable inputs and by observing secondary trading of similar securities obtained from active, non-distressed markets. The Company considers these valuations to be Level 2 inputs as they are corroborated with other market observable inputs. The techniques generally used to determine the fair value of the Company’s fixed maturity investments are detailed below by asset class. U.S. government and government agency U.S. government and government agency securities consist primarily of debt securities issued by the U.S. Treasury and mortgage pass-through agencies such as the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation and the Government National Mortgage Association. Fixed maturity investments included in U.S. government and government agency securities are primarily priced by pricing services. When evaluating these securities, the pricing services gather information from market sources and integrate other observations from markets and sector news. Evaluations are updated by obtaining broker dealer quotes and other market information including actual trade volumes, when available. The fair value of each security is individually computed using analytical models which incorporate option adjusted spreads and other daily interest rate data. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. Non-U.S. government and government agency Non-U.S. government and government agency securities consist of debt securities issued by non-U.S. governments and their agencies along with supranational organizations (also known as sovereign debt securities). Securities held in these sectors are primarily priced by pricing services that employ proprietary discounted cash flow models to value the securities. Key quantitative inputs for these models are daily observed benchmark curves for treasury, swap and high issuance credits. The pricing services then apply a credit spread for each security which is developed by in-depth and real time market analysis. For securities in which trade volume is low, the pricing services utilize data from more frequently traded securities with similar attributes. These models may also be supplemented by daily market and credit research for international markets. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. U.S. states, municipalities and political subdivisions The Company’s U.S. states, municipalities and political subdivisions portfolio contains debt securities issued by U.S. domiciled state and municipal entities. These securities are generally priced by independent pricing services using the techniques described for U.S. government and government agency securities described above. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. Agency residential mortgage-backed securities The Company’s agency residential mortgage-backed investments are primarily priced by pricing services using a mortgage pool specific model which utilizes daily inputs from the active to be announced market which is very liquid, as well as the U.S. treasury market. The model also utilizes additional information, such as the weighted average maturity, weighted average coupon and other available pool level data which is provided by the sponsoring agency. Valuations are also corroborated with daily active market quotes. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. Non-agency residential mortgage-backed securities The Company’s non-agency mortgage-backed investments include non-agency prime residential mortgage-backed fixed maturity investments. The Company holds no sub-prime fixed maturity investments in its fixed maturity investments portfolio. Securities held in these sectors are primarily priced by pricing services using an option adjusted spread model or other relevant models, which principally utilize inputs including benchmark yields, available trade information or broker quotes, and issuer spreads. The pricing services also review collateral prepayment speeds, loss severity and delinquencies among other collateral performance indicators for the securities valuation, when applicable. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. U.S. corporate U.S. corporate debt securities consist primarily of investment-grade debt of a wide variety of U.S. corporate issuers and industries. The Company’s corporate fixed maturity investments are primarily priced by pricing services. When evaluating these securities, the pricing services gather information from market sources regarding the issuer of the security and obtain credit data, as well as other observations, from markets and sector news. Evaluations are updated by obtaining broker dealer quotes and other market information including actual trade volumes, when available. The pricing services also consider the specific terms and conditions of the securities, including any specific features which may influence risk. In certain instances, securities are individually evaluated using a spread which is added to the U.S. treasury curve or a security specific swap curve as appropriate. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. Non-U.S. corporate Non-U.S. corporate debt securities consist primarily of investment-grade debt of a wide variety of non-U.S. corporate issuers and industries. The Company’s non-U.S. corporate fixed maturity investments are primarily priced by pricing services. When evaluating these securities, the pricing services gather information from market sources regarding the issuer of the security and obtain credit data, as well as other observations, from markets and sector news. Evaluations are updated by obtaining broker dealer quotes and other market information including actual trade volumes, when available. The pricing services also consider the specific terms and conditions of the securities, including any specific features which may influence risk. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. Bank loans The Company’s bank loan investments consist primarily of below-investment-grade debt of a wide variety of corporate issuers and industries. The Company’s bank loans are primarily priced by pricing services. When evaluating these securities, the pricing services gather information from market sources regarding the issuer of the security and obtain credit data, as well as other observations, from markets and sector news. Evaluations are updated by obtaining broker dealer quotes and other market information including actual trade volumes, when available. The pricing services also consider the specific terms and conditions of the securities, including any specific features which may influence risk. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. Also, included in the bank loan portfolio is a collection of loan participations held through an intermediary. A third party pricing service provides monthly valuation reports for each loan and participation using a combination of quotations from loan pricing services, leveraged loan indices or market price quotes obtained directly from the intermediary. Significant unobservable inputs used to price these securities include credit spreads and default rates; therefore, the fair values of these investments are classified as Level 3. Asset-backed securities Asset backed securities include mostly investment-grade debt securities backed by pools of loans with a variety of underlying collateral, including automobile loan receivables, student loans, credit card receivables, and collateralized loan obligations originated by a variety of financial institutions. Securities held in these sectors are primarily priced by pricing services. The pricing services apply dealer quotes and other available trade information such as bids and offers, prepayment speeds which may be adjusted for the underlying collateral or current price data, the U.S. treasury curve and swap curve as well as cash settlement. The pricing services determine the expected cash flows for each security held in this sector using historical prepayment and default projections for the underlying collateral and current market data. In addition, a spread is applied to the relevant benchmark and used to discount the cash flows noted above to determine the fair values of the securities held in this sector. As the significant inputs used to price these securities are observable, the fair value of these investments are classified as Level 2. Where pricing is unavailable from pricing services, we obtain non-binding quotes from broker-dealers. This is generally the case when there is a low volume of trading activity and current transactions are not orderly. Broker-dealer quotes for which significant observable inputs are unable to be corroborated with market observable information are classified as Level 3. Commercial mortgage-backed securities Commercial mortgage backed securities are investment-grade debt primarily priced by pricing services. The pricing services apply dealer quotes and other available trade information such as bids and offers, prepayment speeds which may be adjusted for the underlying collateral or current price data, the U.S. treasury curve and swap curve as well as cash settlement. The pricing services determine the expected cash flows for each security held in this sector using historical prepayment and default projections for the underlying collateral and current market data. In addition, a spread is applied to the relevant benchmark and used to discount the cash flows noted above to determine the fair value of the securities held in this sector. As the significant inputs used to price these securities are observable, the fair values of these investments are classified as Level 2. Catastrophe bonds Catastrophe bonds are priced based on broker or underwriter bid indications. Level 2 catastrophe bonds are those traded over-the-counter; catastrophe bonds available only via private issuances are classified as Level 3. Short-term investments Short-term investments consist primarily of highly liquid securities, all with maturities of less than one year from the date of purchase. The fair value of the portfolio is generally determined using amortized cost which approximates fair value. As the highly liquid money market-type funds are actively traded, the fair value of these investments are classified as Level 1. To the extent that the remaining securities are not actively traded due to their approaching maturity, the fair values of these investments are classified as Level 2. Other investments Hedge funds The hedge fund’s administrator provides quarterly NAVs with a three month delay in valuation. The fair value of this investment is measured using the NAV practical expedient and therefore has not been categorized within the fair value hierarchy. Private equity investments The private equity funds provide quarterly or semi-annual partnership capital statements with a three or six month delay which are used as a basis for valuation. These private equity investments vary in investment strategies and are not actively traded in any open markets. The fair value of these investments are measured using the NAV practical expedient and therefore have not been categorized within the fair value hierarchy. Fixed income investment funds The Company’s investment funds classified as Level 2 consist of a pooled investment fund. The pooled investment is invested in fixed income securities with high credit ratings and is available only to Lloyd’s Trust Fund participants. The fair value of units in the investment fund is based on the NAV of the fund, which is traded on a daily basis. Included in investment funds is a residual equity tranche of a structured credit fund valued using a dynamic yield that calculates an income accrual based on an underlying valuation model with a typical cash flow waterfall structure. Significant unobservable inputs used to price this fund include default rates and prepayment rates; therefore, the fair value of the investment fund is classified as Level 3. The fair value of the Company’s remaining investment funds is based on the NAV of the fund as reported by the independent fund administrator. The fund’s administrators provide a monthly reported NAV with a one or three month delay in their valuation. The fair value of these investments is measured using the NAV practical expedient and therefore it has not been categorized within the fair value hierarchy. None of these investments are probable of being sold at amounts different than their NAVs. Overseas deposits The Company’s share of a portfolio of Lloyd’s overseas deposits is managed centrally by Lloyd’s and invested according to local regulatory requirements. The composition of the portfolio varies and the deposits are made across the market. The fair values of the deposits are based on the portfolio level reporting that is provided by Lloyd’s. The fair values of these investments are measured using the NAV practical expedient and therefore have not been categorized within the fair value hierarchy. (c) Level 3 investments The following table presents a reconciliation of the beginning and ending balances for all investments measured at fair value on a recurring basis using Level 3 inputs during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 Bank Loans Catastrophe Bonds Fixed Income Investment Funds Asset Backed Securities Total Level 3 investments, beginning of period $ 210,065 $ 77,461 $ 17,404 $ 103,813 $ 408,743 Purchases 30,785 18,825 529 — 50,139 Sales — — — (70 ) (70 ) Settlements (13,842 ) (31,484 ) — — (45,326 ) Realized gains — 1,235 — — 1,235 Change in net unrealized gains (losses) 495 (340 ) — (1,927 ) (1,772 ) Level 3 investments, end of period $ 227,503 $ 65,697 $ 17,933 $ 101,816 $ 412,949 Three Months Ended March 31, 2017 Bank Loans Catastrophe Bonds Fixed Income Investment Funds Asset Backed Securities Total Level 3 investments, beginning of period $ 246,496 $ 48,375 $ 12,168 $ 23,931 $ 330,970 Purchases 23,176 61,091 — — 84,267 Settlements (33,110 ) (38,780 ) 392 — (71,498 ) Realized gains — 3,134 — — 3,134 Change in net unrealized gains (losses) 132 (1,144 ) — (49 ) (1,061 ) Level 3 investments, end of period $ 236,694 $ 72,676 $ 12,560 $ 23,882 $ 345,812 There were no transfers into or out of Level 3 during the three months ended March 31, 2018 or 2017 . (d) Financial instruments not carried at fair value ASC Topic 825 “Financial Instruments” is also applicable to disclosures of financial instruments not carried at fair value, except for certain financial instruments, including insurance contracts and investments in affiliates. The carrying values of accrued investment income, other assets, net payable for investments purchased and accounts payable and accrued expenses approximated their fair values at March 31, 2018 , due to their respective short maturities. As these financial instruments are not actively traded, their respective fair values are classified within Level 2.

Variable interest entities

Variable interest entities	3 Months Ended
	Mar. 31, 2018
Variable Interest Entities Disclosure [Abstract]
Variable interest entities	Variable interest entities The Company consolidates all VIEs in which it is considered to be the primary beneficiary. The Company’s VIEs are primarily entities in the AlphaCat segment. (a) Consolidated VIEs AlphaCat sidecars Beginning on May 25, 2011, the Company joined with other investors in capitalizing a series of reinsurance and investment entities, referred to as “sidecars,” for the purpose of investing in collateralized reinsurance and retrocessional contracts. Certain of these sidecars deployed their capital through transactions entered into by AlphaCat Reinsurance Ltd. (“AlphaCat Re”). Each of these entities returns capital once the risk period expires and all losses have been paid out. The AlphaCat sidecars are VIEs and are consolidated by the Company. The Company’s maximum exposure to any of these sidecars is the amount of capital invested at any given time. AlphaCat ILS funds The AlphaCat ILS funds received third party subscriptions beginning on December 17, 2012. The Company and third party investors invest in the AlphaCat ILS funds for the purpose of investing in instruments with returns linked to property catastrophe reinsurance, retrocession and ILS contracts. The AlphaCat ILS funds have varying risk profiles and are categorized by the maximum permitted portfolio expected loss of the fund. The permitted portfolio expected loss represents the average annual loss over the set of simulation scenarios divided by the total limit. Lower risk ILS funds are defined as having a maximum permitted portfolio expected loss of less than 7%, whereas higher risk ILS funds have a maximum permitted portfolio expected loss of 7% or greater. The AlphaCat ILS funds primarily deploy their capital through transactions entered into by AlphaCat Re and AlphaCat Master Fund Ltd. (“AlphaCat Master Fund”). All of the AlphaCat ILS funds are VIEs and were consolidated by the Company through May 31, 2017. However, on June 1, 2017, the Company redeemed its investment in one of the lower risk AlphaCat ILS funds. As a result, the Company was no longer deemed to be the primary beneficiary and therefore this fund was deconsolidated effective June 1, 2017. The Company’s maximum exposure to any of the funds is the amount of capital invested at any given time and any remaining capital commitments. AlphaCat Re and AlphaCat Master Fund The Company utilizes AlphaCat Re and AlphaCat Master Fund (collectively the “Master Funds”), both market facing entities, for the purpose of writing collateralized reinsurance and investing in capital markets products, respectively, on behalf of certain entities within the Asset Management segment and direct third party investors. AlphaCat Re enters into transactions on behalf of the AlphaCat sidecars and ILS funds (collectively the “Feeder Funds”) and direct third party investors, whereas AlphaCat Master Fund only enters into transactions on behalf of certain AlphaCat ILS funds. All of the risks and rewards of the underlying transactions are allocated to the Feeder Funds and direct third party investors using variable funding notes. The Master Funds are VIEs and are consolidated by the Company. Notes Payable to AlphaCat Investors The Master Funds issue variable funding notes to the Feeder Funds, and direct to third party investors, in order to write collateralized reinsurance and invest in capital markets products on their behalf. The Company’s investments in the Feeder Funds, together with investments made by third parties in the Feeder Funds and on a direct basis, are provided as consideration for the notes to the Master Funds. The duration of the underlying collateralized reinsurance contracts and capital market products is typically twelve months ; however, the variable funding notes do not have a stated maturity date since repayment is dependent on the settlement and income or loss of the underlying transactions. Therefore, the notes are redeemed as the underlying transactions are settled. The income or loss generated by the underlying transactions is then transferred to the Feeder Funds and direct third party investors via the variable funding notes. Any notes issued by the Master Funds to the consolidated Feeder Funds are eliminated on consolidation and only variable funding notes issued by AlphaCat Re directly to third party investors and non-consolidated Feeder Funds remain on the Consolidated Balance Sheets as notes payable to AlphaCat investors with the related income or loss included in the Consolidated Statements of (Loss) Income and Comprehensive Income as (income) attributable to AlphaCat investors. To the extent that the income has not been returned to the investors, it is included in accounts payable and accrued expenses in the Consolidated Balance Sheets. One of the AlphaCat ILS funds (the “Fund”) issued both common shares and structured notes to the Company and third party investors in order to capitalize the fund. The Fund deploys its capital through AlphaCat Re; therefore, the structured notes do not have a stated maturity date since repayment is dependent on the settlement and income or loss of the variable funding notes with AlphaCat Re. The structured notes rank senior to the common shares of the Fund and earn an interest rate of 6.5% ( 2017 : 7% ) per annum, payable on a cumulative basis in arrears. As the Fund is consolidated by the Company, the structured notes issued to the Company are eliminated on consolidation and only the structured notes issued to third party investors remain on the Consolidated Balance Sheets as notes payable to AlphaCat investors, with any related interest included in the Consolidated Statements of (Loss) Income and Comprehensive (Loss) Income as loss (income) attributable to AlphaCat investors. To the extent that the accrued interest on the structured notes has not been returned to the investors, it is included in accounts payable and accrued expenses in the Consolidated Balance Sheets. The following tables present reconciliations of the beginning and ending notes payable to AlphaCat investors during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 Variable Funding Notes Structured Notes Total Notes payable to AlphaCat investors, beginning of period $ 936,164 $ 172,200 $ 1,108,364 Issuance of notes payable to AlphaCat investors 506,540 179,972 686,512 Redemption of notes payable to AlphaCat investors (530,546 ) — (530,546 ) Foreign exchange losses 3,864 — 3,864 Notes payable to AlphaCat investors, end of period $ 916,022 $ 352,172 $ 1,268,194 Three Months Ended March 31, 2017 Variable Funding Notes Structured Notes Total Notes payable to AlphaCat investors, beginning of period $ 278,202 $ — $ 278,202 Issuance of notes payable to AlphaCat investors 274,010 103,320 377,330 Redemption of notes payable to AlphaCat investors (208,956 ) — (208,956 ) Notes payable to AlphaCat investors, end of period $ 343,256 $ 103,320 $ 446,576 The income attributable to AlphaCat investors for the three months ended March 31, 2018 was $10,862 ( 2017 : $7,503 ). As at March 31, 2018 , amounts due to AlphaCat investors totaling $43,442 ( December 31, 2017 : $18,054 ) were included in accounts payable and accrued expenses. BetaCat ILS funds The BetaCat ILS funds follow a passive buy-and-hold investment strategy, investing exclusively in catastrophe bonds (principal-at-risk variable rate notes and other event-linked securities, referred to collectively as “Cat Bonds”) focused on property and casualty risks and issued under Rule 144A of the Securities Act of 1933, as amended. Two of the three BetaCat ILS funds are VIEs, one of which is consolidated by the Company. The remaining fund is a VOE and is consolidated by the Company as it owns all of the fund’s voting equity interests. The Company’s maximum exposure to any of the funds is the amount of capital invested at any given time. The following table presents the total assets and total liabilities of the Company’s consolidated VIEs, excluding intercompany eliminations, as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Total Assets Total Liabilities Total Assets Total Liabilities AlphaCat sidecars $ 25,952 $ 3,071 $ 25,975 $ 3,267 AlphaCat ILS funds - Lower Risk 1,046,458 11,156 1,107,503 259,630 AlphaCat ILS funds - Higher Risk 1,431,945 676,225 1,310,071 912,341 AlphaCat Re and AlphaCat Master Fund 3,878,359 3,878,189 3,398,082 3,397,912 BetaCat ILS funds 104,857 2,207 77,221 261 Assets of consolidated VIEs can only be used to settle obligations and liabilities of the consolidated VIEs and do not have recourse to the general credit of the Company. Investments held by these entities are presented separately in Note 4 , “Investments,” as non-managed investments. (b) Non-Consolidated VIEs The Company invests in private equity and other investment vehicles as part of the Company’s investment portfolio. The activities of these VIEs are generally limited to holding investments and the Company’s involvement in these entities is passive in nature. The Company’s maximum exposure to the VIEs is the amount of capital invested at any given time, and the Company does not have the power to direct the activities which most significantly impact the VIEs economic performance. The Company is therefore not the primary beneficiary of these VIEs. Refer to Note 4 , “Investments,” for further details.

Noncontrolling interest

Noncontrolling interest	3 Months Ended
	Mar. 31, 2018
Noncontrolling Interest [Abstract]
Noncontrolling interest	Noncontrolling interests Investors in certain of the AlphaCat and BetaCat ILS funds have rights that enable them, subject to certain limitations, to redeem their shares. Such investments held by third parties are therefore recorded in the Company’s Consolidated Balance Sheets as redeemable noncontrolling interests, a mezzanine item between liabilities and shareholders’ equity. If and when a redemption notice is received, the fair value of the redemption is reclassified to accounts payable and accrued expenses. The AlphaCat sidecars and one of the AlphaCat ILS funds have no shareholder redemption rights. Therefore, the third party equity is recorded in the Company’s Consolidated Balance Sheets as noncontrolling interests. The following tables present a reconciliation of the beginning and ending balances of redeemable noncontrolling interests and noncontrolling interests for the three months ended March 31, 2018 and 2017 : Redeemable Noncontrolling Interests Noncontrolling Interests Total Three Months Ended March 31, Three Months Ended March 31, Three Months Ended March 31, 2018 2017 2018 2017 2018 2017 Balance, beginning of period $ 1,004,094 $ 1,528,001 $ 16,718 $ 165,977 $ 1,020,812 $ 1,693,978 Issuance of shares 385,300 103,699 281,300 154,980 666,600 258,679 Income attributable to noncontrolling interests 28,373 25,930 36,339 16,642 64,712 42,572 Redemption of shares / Distributions 5,343 — — (7,002 ) 5,343 (7,002 ) Balance, end of period $ 1,423,110 $ 1,657,630 $ 334,357 $ 330,597 $ 1,757,467 $ 1,988,227 As at March 31, 2018 , redemptions payable of $nil ( December 31, 2017 : $180,104 ) relating to redeemable noncontrolling interests were included within accounts payable and accrued expenses in the Company’s Consolidated Balance Sheets.

Derivative instruments

Derivative instruments	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative instruments	Derivative instruments The Company enters into various derivative instruments in the form of foreign currency forward exchange contracts, interest rate swap contracts and weather derivative instruments. These derivative instruments are used to manage exposures to currency and interest rate risks, to enhance the efficiency of the Company’s investment portfolio and to provide protection against cedants’ financial exposure to variability in weather patterns. All of the Company’s outstanding derivative financial instruments are recognized in the Consolidated Balance Sheets at their fair values. The effect on earnings from recognizing the fair values of these derivative financial instruments depends on each instrument’s intended use, hedge designation, and effectiveness in offsetting the exposure it is intended to hedge. (a) Derivatives not designated as hedging instruments The following tables summarize information on the classification and amount of the fair value of derivatives not designated as hedging instruments within the Company’s Consolidated Balance Sheets as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Derivatives not designated as hedging instruments Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Foreign currency forward contracts $ 239,398 $ 1,945 $ 433 $ 283,765 $ 1,147 $ 906 Interest rate swap contracts $ 200,000 $ 7,357 $ — $ 200,000 $ 1,589 $ — Weather derivative contracts $ 4,825 $ 26,958 $ — $ 4,825 $ 853 $ — (a) Asset and liability derivative positions are classified within other assets and accounts payable and accrued expenses, respectively, within the Company’s Consolidated Balance Sheets. The foreign currency forward contracts and interest rate swap contracts are valued on the basis of standard industry valuation models. The inputs to these models are based on observable market inputs, and as such the fair values of these contracts are classified as Level 2. The weather derivative contracts are valued on the basis of modeled and other information provided by Validus’ counterparties. Validus reviews this information, which represents Level 3 inputs, as it is ultimately management’s responsibility to ensure that the fair values reflected in the Company’s financial statements are appropriate. The following table summarizes information on the classification and net impact on earnings recognized in the Company’s Consolidated Statements of Income and Comprehensive Income relating to derivatives that were not designated as hedging instruments during the three months ended March 31, 2018 and 2017 : Derivatives not designated as hedging instruments Classification of gains recognized in earnings Three Months Ended March 31, 2018 2017 Foreign currency forward contracts Foreign exchange (losses) gains $ (5,201 ) $ 453 Foreign currency forward contracts Other insurance related income and other income $ — $ (105 ) Interest rate swap contracts Net realized gains on investments $ 5,944 $ — Weather derivative contracts Other insurance related income and other income $ 26,773 $ — (b) Derivatives designated as hedging instruments Derivative instruments designated as cash flow hedges During 2012 and 2013, the Company entered into several swap agreements with third parties in order to convert the floating interest rates associated with its Junior Subordinated Deferrable Debentures into fixed rates. See Note 13 , “ Debt and financing arrangements, ” for further details. The Company also designates certain foreign exchange contracts as cash flow hedges of anticipated foreign currency-denominated sales or purchases. The following table summarizes information on the classification and amount of the fair value of derivatives designated as hedging instruments on the Consolidated Balance Sheets as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Derivatives designated as hedging instruments Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Interest rate swap contracts $ 552,263 $ 23,256 $ 4,931 $ 552,263 $ 9,806 $ 18,840 Foreign currency forward contracts $ 80,373 $ 4,503 $ — $ 96,293 $ 1,891 $ — (a) Asset and liability derivative positions are classified within other assets and accounts payable and accrued expenses, respectively, within the Company’s Consolidated Balance Sheets. The interest rate swap contracts and foreign currency forward contracts are valued on the basis of Level 2 inputs. The following tables provide the total impact on other comprehensive income and earnings relating to the derivative instruments formally designated as cash flow hedges for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, Interest rate swap contracts 2018 2017 Amount recognized in other comprehensive income $ 25,843 $ 98 Amount reclassified to finance expenses $ 1,343 $ — Three Months Ended March 31, Foreign currency forward contracts 2018 2017 Amount recognized in other comprehensive income $ 2,920 $ — Amount reclassified to general and administrative expenses $ (308 ) $ — (c) Balance sheet offsetting There was no balance sheet offsetting activity as at March 31, 2018 or December 31, 2017 . The Company provides investments as collateral for interest rate swap contracts and weather derivative contracts. The Company does not provide collateral or financial instruments as security for foreign currency forward contracts. Our derivative instruments are generally traded under International Swaps and Derivatives Association master agreements, which establish terms that apply to all transactions. On a periodic basis, the amounts receivable from or payable to the counterparties are settled in cash. The Company has not elected to settle multiple transactions with an individual counterparty on a net basis.

Reserve for losses and loss exp

Reserve for losses and loss expenses	3 Months Ended
	Mar. 31, 2018
Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract]
Reserve for losses and loss expenses	Reserve for losses and loss expenses The following table summarizes the Company’s reserve for losses and loss expenses as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Case reserves $ 1,770,278 $ 1,753,844 IBNR 2,862,351 3,077,546 Reserve for losses and loss expenses $ 4,632,629 $ 4,831,390 The following table represents an analysis of paid and unpaid losses and loss expenses incurred and a reconciliation of the beginning and ending unpaid losses and loss expenses for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Reserve for losses and loss expenses, beginning of period $ 4,831,390 $ 2,995,195 Loss reserves recoverable (1,233,997 ) (430,421 ) Net reserves for losses and loss expenses, beginning of period 3,597,393 2,564,774 Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in: Current year 329,115 330,816 Prior years (7,570 ) (61,231 ) Total incurred losses and loss expenses 321,545 269,585 Foreign exchange loss 15,627 12,317 Less net losses and loss expenses paid in respect of losses occurring in: Current year (19,735 ) (7,698 ) Prior years (262,145 ) (238,089 ) Total net paid losses (281,880 ) (245,787 ) Net reserve for losses and loss expenses, end of period 3,652,685 2,600,889 Loss reserves recoverable 979,944 451,856 Reserve for losses and loss expenses, end of period $ 4,632,629 $ 3,052,745 Incurred losses and loss expenses comprise: Three Months Ended March 31, 2018 2017 Gross losses and loss expenses $ 248,781 $ 336,442 Reinsurance recoveries 72,764 (66,857 ) Net incurred losses and loss expenses $ 321,545 $ 269,585 The net (favorable) adverse development on prior accident years by segment and line of business for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 Property Specialty - Short-tail Specialty - Other Total Reinsurance Segment $ (4,822 ) $ (13,451 ) $ 435 $ (17,838 ) Insurance Segment 4,068 (12,201 ) (7,415 ) (15,548 ) Asset Management Segment 25,200 616 — 25,816 Net adverse (favorable) development $ 24,446 $ (25,036 ) $ (6,980 ) $ (7,570 ) Three Months Ended March 31, 2017 Property Specialty - Short-tail Specialty - Other Total Reinsurance Segment $ (4,062 ) $ (26,748 ) $ (314 ) $ (31,124 ) Insurance Segment (8,666 ) (11,763 ) (6,260 ) (26,689 ) Asset Management Segment (4,395 ) 977 — (3,418 ) Net favorable development $ (17,123 ) $ (37,534 ) $ (6,574 ) $ (61,231 ) The net favorable development on prior accident years for the three months ended March 31, 2018 and 2017 was primarily driven by favorable development on attritional losses.

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2018
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance The Company’s reinsurance balances recoverable at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 December 31, 2017 Loss reserves recoverable on unpaid: Case reserves $ 235,814 $ 275,450 IBNR 744,130 958,547 Total loss reserves recoverable 979,944 1,233,997 Paid losses recoverable 59,892 46,873 Total reinsurance recoverable $ 1,039,836 $ 1,280,870 (a) Credit risk The cession of reinsurance does not legally discharge the Company from its primary liability for the full amount of the (re)insurance policies it writes, and the Company is required to pay the loss and bear collection risk regarding reinsurers’ obligations under reinsurance and retrocession agreements. Validus records provisions for uncollectible reinsurance recoverable when collection becomes unlikely due to the reinsurer’s inability to pay. To the extent the creditworthiness of the Company’s reinsurers were to deteriorate due to adverse events affecting the reinsurance industry, such as a large number of major catastrophes, actual uncollectible amounts could be significantly greater than the Company’s provision. Amounts recoverable from reinsurers are estimated in a manner consistent with the underlying loss reserves. The Company evaluates the financial condition of its reinsurers and monitors concentration of credit risk arising from its exposure to individual reinsurers. The reinsurance program is generally placed with reinsurers whose rating, at the time of placement, is A- or better as rated by Standard & Poor’s or the equivalent with other rating agencies. Exposure to a single reinsurer is also controlled with restrictions dependent on rating. As at March 31, 2018 , $1,029,021 or 99.0% ( December 31, 2017 : $1,270,503 or 99.2% ) of the Company’s reinsurance balances recoverable were either fully collateralized or recoverable from reinsurers rated A- or better. Information regarding the Company’s concentration of credit risk arising from its exposure to individual reinsurers as at March 31, 2018 and December 31, 2017 is as follows: March 31, 2018 December 31, 2017 Reinsurance Recoverable % of Total Reinsurance Recoverable % of Total Top 10 reinsurers $ 878,685 84.5 % $ 1,055,445 82.5 % Other reinsurers’ balances > $1 million 153,572 14.8 % 218,226 17.0 % Other reinsurers’ balances < $1 million 7,579 0.7 % 7,199 0.5 % Total $ 1,039,836 100.0 % $ 1,280,870 100.0 % March 31, 2018 Top 10 Reinsurers Rating Reinsurance Recoverable % of Total Fully collateralized reinsurers NR $ 407,361 39.2 % Everest Re A+ 128,360 12.3 % Lloyd's Syndicates A+ 69,885 6.7 % Swiss Re AA- 56,892 5.5 % Munich Re AA- 50,097 4.8 % Hannover Re AA- 49,501 4.8 % Transatlantic Re A+ 38,446 3.7 % Qatar Insurance Company A 30,981 3.0 % Markel A 25,893 2.5 % XL Catlin A+ 21,269 2.0 % Total $ 878,685 84.5 % NR: Not rated December 31, 2017 Top 10 Reinsurers Rating Reinsurance Recoverable % of Total Fully collateralized reinsurers NR $ 459,339 35.9 % Everest Re A+ 128,206 10.0 % Munich Re AA- 94,180 7.4 % Lloyd's Syndicates A+ 74,277 5.8 % Federal Crop Insurance Corporation (a) 68,745 5.4 % Swiss Re AA- 65,218 5.1 % Hannover Re AA- 53,523 4.2 % Qatar Insurance Company A 50,160 3.9 % Transatlantic Re A+ 33,729 2.6 % Markel A 28,068 2.2 % Total $ 1,055,445 82.5 % NR: Not rated (a) The Company participates in a crop reinsurance program sponsored by the U.S. federal government. The Company remains obligated for amounts ceded in the event that its reinsurers or retrocessionaires do not meet their obligations, except for amounts ceded to the U.S. federal government in the Insurance segment agriculture line of business. At March 31, 2018 and December 31, 2017 , the provision for uncollectible reinsurance relating to reinsurance recoverables was $8,403 and $8,848 , respectively.

Share capital

Share capital	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Share capital	Share capital The Company’s share capital consists of Preferred Shares and Common Shares, each with a par value of $0.175 per share. Holders of Preferred Shares have no voting rights with respect to matters that generally require the approval of voting shareholders but are entitled to vote in certain extraordinary instances. Holders of common shares are entitled to one vote for each share held, subject to certain voting limitations. The Company is authorized to issue up to an aggregate of 571,428,571 common and preferred shares with a par value of $0.175 per share. (a) Preferred shares 5.875% Non-Cumulative Preferred Shares, Series A (the “Series A Preferred Shares”) On June 13, 2016, the Company issued 6,000 shares of its 5.875% Non-Cumulative Preferred Shares, Series A (the “Series A Preferred Shares”) (equivalent to 6,000,000 Depositary Shares, each of which represents a 1/1,000th interest in a Series A Preferred Share), $0.175 par value and $25,000 liquidation preference per share (equivalent to $25 per Depositary Share). The Series A Preferred Shares were registered and sold under the Securities Act of 1933, as amended, and were issued at a price to the public of $25,000 per share (equivalent to $25 per Depositary Share). After underwriting discounts and expenses, the Company received net proceeds of $144,852 which were used for general corporate purposes. The Depositary Shares, representing the Series A Preferred Shares, are traded on the New York Stock Exchange (“NYSE”) under the symbol “VRPRA.” Holders of the Series A Preferred Shares have no voting rights, except with respect to certain fundamental changes in the terms of the Series A Preferred Shares and in the case of certain dividend non-payments or as otherwise required by Bermuda law or the Company’s bye-laws. 5.800% Non-Cumulative Preferred Shares, Series B (the “Series B Preferred Shares”) On June 12, 2017, the Company issued 10,000 shares of its 5.800% Non-Cumulative Preferred Shares, Series B (the “Series B Preferred Shares”) (equivalent to 10,000,000 Depositary Shares, each of which represents a 1/1,000th interest in a Series B Preferred Share), $0.175 par value and $25,000 liquidation preference per share (equivalent to $25 per Depositary Share). The Series B Preferred Shares were registered and sold under the Securities Act of 1933, as amended, and were issued at a price to the public of $25,000 per share (equivalent to $25 per Depositary Share). After underwriting discounts and expenses, the Company received net proceeds of $241,686 which were used for general corporate purposes. The Depositary Shares, representing the Series B Preferred Shares, are traded on the New York Stock Exchange (“NYSE”) under the symbol “VRPRB.” Holders of the Series B Preferred Shares have no voting rights, except with respect to certain fundamental changes in the terms of the Series B Preferred Shares and in the case of certain dividend non-payments or as otherwise required by Bermuda law or the Company’s bye-laws. The Company had 6,000 Series A Preferred Shares and 10,000 Series B Preferred Shares issued and outstanding as at March 31, 2018 and December 31, 2017 . For further information regarding the Company’s preferred shares refer to Note 16(a), “Share capital,” included within the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . (b) Common shares The holders of common shares are entitled to receive dividends and are allocated one vote per share , provided that, if the controlled shares of any shareholder or group of related shareholders constitute more than 9.09 percent of the outstanding common shares of the Company, their voting power will be reduced to 9.09 percent. The Company may from time to time repurchase its securities, including common shares, Junior Subordinated Deferrable Debentures and Senior Notes. The Company has repurchased 81,035,969 common shares for an aggregate purchase price of $2,730,975 from the inception of its share repurchase program to March 31, 2018 . The Company had $293,426 remaining under its authorized share repurchase program as of March 31, 2018 . The Company may make purchases under its share repurchase program from time to time in the open market or in privately negotiated transactions. The timing, form and amount of the share repurchases under the program will depend on a variety of factors, including market conditions, the Company’s capital position relative to internal and rating agency targets, legal requirements and other factors. The repurchase program may be modified, extended or terminated by the Board of Directors at any time. The following table is a summary of the common shares issued and outstanding during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Common shares issued, beginning of period 161,994,491 161,279,976 Restricted share awards vested, net of shares withheld 7,423 3,440 Restricted share units vested, net of shares withheld 2,055 1,995 Common shares issued, end of period 162,003,969 161,285,411 Treasury shares, end of period (82,674,941 ) (82,147,821 ) Common shares outstanding, end of period 79,329,028 79,137,590 (c) Dividends During February 2018, the Company announced a quarterly cash dividend of $0.38 per common share (2017: $0.38 ), payable on March 29, 2018 to shareholders of record on March 15, 2018. The Company also announced a quarterly cash dividend of $0.3671875 (2017: $0.3671875 ) and $0.3625000 per depository share on the outstanding Series A and Series B Preferred Shares, respectively. The Series A and Series B Preferred Share dividends are payable on March 15, 2018 to shareholders of record on March 1, 2018.

Stock plans

Stock plans	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock plans	Stock plans (a) Long Term Incentive Plan The Company’s Amended and Restated 2005 Long Term Incentive Plan (“LTIP”) provides for grants to employees of options, stock appreciation rights (“SARs”), restricted shares, restricted share units, performance shares, dividend equivalents or other share-based awards. The total number of shares reserved for issuance under the LTIP are 2,753,292 , of which 706,006 shares are remaining. The LTIP is administered by the Compensation Committee of the Board of Directors. No SARs have been granted to date. The grant date fair value of each award is established at the fair market value of the Company’s common shares at the date of grant. (i) Options The Company has not granted any stock option awards since September 4, 2009. These stock option awards were fully amortized as at December 31, 2012, and the final options outstanding were exercised during the year ended December 31, 2017. While outstanding, the Company’s options could be exercised for voting common shares upon vesting and had a term of ten years. The fair value of the option awards at the date of grant was determined using the Black-Scholes option-pricing model. Expected volatility was based on the stock price volatility of comparable publicly-traded companies. The Company used the simplified method consistent with U.S. GAAP authoritative guidance on stock compensation expenses to estimate expected lives for options granted during the period. Activity with respect to options for the three months ended March 31, 2017 was as follows: Options Weighted Average Grant Date Fair Value Weighted Average Grant Date Exercise Price Options outstanding, beginning and end of period 26,136 $ 6.78 $ 23.48 (ii) Restricted share awards Restricted shares granted under the LTIP vest either pro rata or 100% at the end of the required service period and contain certain restrictions during the vesting period, relating to, among other things, forfeiture in the event of termination of employment, and transferability. Share compensation expenses of $8,113 were recorded in connection with restricted share awards for the three months ended March 31, 2018 ( 2017 : $9,044 ). The expenses represent the proportionate accrual of the fair value of each grant based on the remaining vesting period. Activity with respect to unvested restricted share awards for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 2017 Restricted Share Awards Weighted Average Grant Date Fair Value Restricted Share Awards Weighted Average Grant Date Fair Value Restricted share awards outstanding, beginning of period 2,080,397 $ 43.66 2,469,982 $ 40.89 Restricted share awards granted 1,552 67.64 2,082 57.66 Restricted share awards vested (8,092 ) 44.49 (4,571 ) 37.93 Restricted share awards forfeited (6,138 ) 47.46 (513 ) 48.69 Restricted share awards outstanding, end of period 2,067,719 $ 43.66 2,466,980 $ 40.91 At March 31, 2018 , there were $40,926 ( December 31, 2017 : $48,907 ) of total unrecognized share compensation expenses in respect of restricted share awards that are expected to be recognized over a weighted-average period of 2.2 years ( December 31, 2017 : 2.3 years ). (iii) Restricted share units Restricted share units under the LTIP vest either ratably or 100% at the end of the required service period and contain certain restrictions during the vesting period, relating to, among other things, forfeiture in the event of termination of employment, and transferability. Share compensation expenses of $332 were recorded in connection with restricted share units for the three months ended March 31, 2018 ( 2017 : $315 ). The expenses represent the proportionate accrual of the fair value of each grant based on the remaining vesting period. Activity with respect to unvested restricted share units for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 2017 Restricted Share Units Weighted Average Grant Date Fair Value Restricted Share Units Weighted Average Grant Date Fair Value Restricted share units outstanding, beginning of period 109,394 $ 42.20 112,808 $ 40.95 Restricted share units vested (2,178 ) 38.24 (2,115 ) 38.24 Restricted share units issued in lieu of cash dividends 886 42.20 717 40.95 Restricted share units forfeited (1 ) 38.24 — — Restricted share units outstanding, end of period 108,101 $ 42.28 111,410 $ 41.01 At March 31, 2018 , there were $1,592 ( December 31, 2017 : $1,909 ) of total unrecognized share compensation expenses in respect of restricted share units that are expected to be recognized over a weighted-average period of 2.3 years ( December 31, 2017 : 2.4 years ). (iv) Performance share awards Performance share awards vest three years after the grant date, with the grant date fair value of each share awarded recognized evenly over this period. The number of performance shares initially granted is adjusted via “conversion adjustments” to reflect the compounded growth in the Dividend-Adjusted Book Value per Diluted Share over the three years. The cumulative compensation expense recognized and unrecognized as at any reporting period date represents the adjusted estimate of performance shares that will ultimately be awarded, valued at their original grant date fair values. Share compensation expenses of $1,284 were recorded for the three months ended March 31, 2018 ( 2017 : $132 ). The share compensation expenses represent the proportionate accrual of the fair value of each grant based on the remaining vesting period. Activity with respect to unvested performance share awards for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 2017 Performance Share Awards Weighted Average Grant Date Fair Value Performance Share Awards Weighted Average Grant Date Fair Value Performance share awards outstanding, beginning of period 314,068 $ 49.37 285,820 $ 44.53 Performance share awards conversion adjustment — — (26,322 ) 36.82 Performance share awards outstanding, end of period 314,068 $ 49.37 259,498 $ 45.26 At March 31, 2018 , there were $6,597 ( December 31, 2017 : $7,813 ) of total unrecognized share compensation expenses in respect of performance share awards that are expected to be recognized over a weighted-average period of 1.8 years ( December 31, 2017 : 1.9 years ). (b) Total share compensation expenses The breakdown of share compensation expenses by award type is as follows: Three Months Ended March 31, 2018 2017 Restricted share awards $ 8,113 $ 9,044 Restricted share units 332 315 Performance share awards 1,284 132 Total $ 9,729 $ 9,491

Debt and financing arrangements

Debt and financing arrangements	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt and financing arrangements	Debt and financing arrangements The Company’s financing structure is composed of debentures and senior notes payable along with credit and other facilities. For further information regarding the Company’s financing structure refer to Note 19, “Debt and financing arrangements,” included within the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . (a) Senior Notes and Junior Subordinated Deferrable Debentures The Company’s outstanding debentures and senior notes payable as at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 December 31, 2017 Deferrable debentures 2006 Junior Subordinated $ 150,000 $ 150,000 2007 Junior Subordinated 139,800 139,800 Flagstone 2006 Junior Subordinated 136,022 135,608 Flagstone 2007 Junior Subordinated 113,750 113,750 Total debentures payable 539,572 539,158 2010 Senior Notes due 2040 250,000 250,000 Less: Unamortized debt issuance costs (4,386 ) (4,436 ) Total senior notes payable 245,614 245,564 Total debentures and senior notes payable $ 785,186 $ 784,722 The following table summarizes the key terms of the Company’s Senior Notes and Junior Subordinated deferrable debentures: Description Issuance date Issued Maturity date Interest Rate as at Interest payments due Issuance Date March 31, 2018 2006 Junior Subordinated Deferrable Debentures June 15, 2006 $ 150,000 June 15, 2036 9.069 % (a) 5.831 % (e) Quarterly Flagstone 2006 Junior Subordinated Deferrable Debentures August 23, 2006 $ 136,022 September 15, 2036 3.540 % (b) 6.463 % (e) Quarterly 2007 Junior Subordinated Deferrable Debentures June 21, 2007 $ 200,000 June 15, 2037 8.480 % (c) 5.180 % (e) Quarterly Flagstone 2007 Junior Subordinated Deferrable Debentures June 8, 2007 $ 100,000 July 30, 2037 3.000 % (b) 5.900 % (e) Quarterly Flagstone 2007 Junior Subordinated Deferrable Debentures September 20, 2007 $ 25,000 September 15, 2037 3.100 % (b) 5.983 % (e) Quarterly 2010 Senior Notes due 2040 January 26, 2010 $ 250,000 January 26, 2040 8.875 % (d) 8.875 % (d) Semi-annually in arrears (a) Fixed interest rate for 5 years , floating interest rate of three-month LIBOR plus 3.550% thereafter, reset quarterly. (b) Floating interest rate of three-month LIBOR plus amount stated, reset quarterly. (c) Fixed interest rate for 5 years , floating interest rate of three-month LIBOR plus 2.950% thereafter, reset quarterly. (d) Fixed interest rate. (e) Fixed interest rate as a result of interest rate swap contracts entered into by the Company. Future payments of principal of $250,000 on the 2010 Senior Notes and $539,572 on the debentures are all expected to be made after 2023. (b) Credit and other facilities The Company’s outstanding credit facilities as at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 Credit facility Commitment Outstanding (a) Drawn (b) Cash and investments pledged as collateral $85,000 syndicated unsecured letter of credit facility $ 85,000 $ — $ — $ — $300,000 syndicated secured letter of credit facility 300,000 98,419 — 123,468 $100,000 secured bi-lateral letter of credit facility 100,000 4,407 — 22,364 $25,000 IPC bi-lateral facility 25,000 7,705 — — $236,000 Flagstone bi-lateral facility 236,000 109,796 — 156,058 $65,000 unsecured revolving credit facility 65,000 — — — $100,000 unsecured revolving credit facility 100,000 — — — FHLB secured facility 433,165 206,000 206,000 238,349 Total credit facilities $ 1,344,165 $ 426,327 $ 206,000 $ 540,239 (a) Indicates utilization of commitment amount. (b) Represents drawn borrowings included in accounts payable and accrued expenses. December 31, 2017 Credit facility Commitment Outstanding (a) Drawn (b) Cash and investments pledged as collateral $85,000 syndicated unsecured letter of credit facility $ 85,000 $ — $ — $ — $300,000 syndicated secured letter of credit facility 300,000 92,979 — 118,188 $24,000 secured bi-lateral letter of credit facility 24,000 5,765 — 22,340 $25,000 IPC bi-lateral facility 25,000 7,754 — — $236,000 Flagstone bi-lateral facility 236,000 115,682 — 184,569 $65,000 unsecured revolving credit facility 65,000 — — — $100,000 unsecured revolving credit facility 100,000 — — — FHLB secured facility 484,096 206,000 206,000 251,767 Total credit facilities $ 1,319,096 $ 428,180 $ 206,000 $ 576,864 (a) Indicates utilization of commitment amount. (b) Represents drawn borrowings included in accounts payable and accrued expenses. On January 24, 2018, the Company increased the size of the secured bi-lateral letter of credit facility with Citibank Europe plc (the “Secured bi-lateral LOC facility”) from $24,000 to $100,000 . All covenants and restrictions under the Secured bi-lateral LOC facility remain unchanged. As of March 31, 2018 , $4,407 ( December 31, 2017 : $5,765 ) of letters of credit were outstanding under the Secured bi-lateral LOC facility. As of March 31, 2018 and December 31, 2017 , the Company was in compliance with all covenants and restrictions under its credit facilities. (c) Finance expenses Finance expenses consist of interest on the Junior Subordinated Deferrable Debentures and the 2010 Senior Notes, the amortization of debt offering costs, credit facility fees, bank and other charges and AlphaCat financing fees as follows: Three Months Ended March 31, 2018 2017 2006 Junior Subordinated Deferrable Debentures $ 2,186 $ 2,187 2007 Junior Subordinated Deferrable Debentures 1,810 1,810 Flagstone 2006 Junior Subordinated Deferrable Debentures 2,227 2,221 Flagstone 2007 Junior Subordinated Deferrable Debentures 1,713 1,723 2010 Senior Notes 5,597 5,597 Credit facilities 416 218 Bank and other charges 263 151 AlphaCat fees (a) 51 36 Total finance expenses $ 14,263 $ 13,943 (a) Includes finance expenses incurred by AlphaCat Managers Ltd. in relation to fund raising for the AlphaCat sidecars, the AlphaCat ILS funds and AlphaCat direct.

Accumulated other comprehensive

Accumulated other comprehensive loss	3 Months Ended
	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive loss	Accumulated other comprehensive income (loss) The changes in accumulated other comprehensive income (loss), by component for the three months ended March 31, 2018 and 2017 are as follows: Three Months Ended March 31, 2018 Foreign currency translation adjustment Minimum pension liability Cash flow hedge Total Balance, net of tax, beginning of period $ (18,217 ) $ 2,719 $ (6,694 ) $ (22,192 ) Other comprehensive income (loss), net of tax 1,837 (38 ) 28,763 30,562 Amounts reclassified from accumulated other comprehensive income — — 1,035 1,035 Balance, net of tax, end of period $ (16,380 ) $ 2,681 $ 23,104 $ 9,405 Three Months Ended March 31, 2017 Foreign currency translation adjustment Minimum pension liability Cash flow hedge Total Balance, net of tax, beginning of period $ (22,274 ) $ (150 ) $ (792 ) $ (23,216 ) Other comprehensive income, net of tax 597 68 98 763 Balance, net of tax, end of period $ (21,677 ) $ (82 ) $ (694 ) $ (22,453 )

Commitments and contingencies

Commitments and contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies (a) Funds at Lloyd’s The Company operates in Lloyd’s through a corporate member, Talbot 2002 Underwriting Capital Ltd (“T02”), which is the sole participant in Lloyd’s Syndicate 1183 (the “Talbot Syndicate”). Lloyd’s sets T02’s Economic Capital Assessment (“ECA”) annually based on the Talbot Syndicate’s business plan, rating environment and reserving environment together with input arising from Lloyd’s discussions with regulatory and rating agencies, and other parties. This ECA is satisfied by syndicate net assets determined on a basis consistent with Solvency II, an EU directive covering capital adequacy, risk management and regulatory reporting for insurers. Any syndicate net liabilities on a Solvency II basis are required to be funded in addition to the ECA. Such additional funds, known as Funds at Lloyd’s (“FAL”), comprises cash and investments. The Company provided FAL in the amount of $661,600 during the fourth quarter of 2017 ( 2016 : $583,600 ). The amounts which are provided as FAL are not available for distribution to the Company for the payment of dividends. T02 may also be required to maintain funds under the control of Lloyd’s in excess of its capital requirement and such funds also may not be available for distribution to the Company for the payment of dividends. (b) Lloyd’s Central Fund Whenever a member of Lloyd’s is unable to pay its debts to policyholders, such debts may be payable by the Lloyd’s Central Fund. If Lloyd’s determines that the Central Fund needs to be increased, it has the power to assess premium levies on current Lloyd’s members up to 3% of a member’s underwriting capacity in any one year. The Company does not believe that any assessment is likely in the foreseeable future and has not provided any allowance for such an assessment. However, based on the Company’s 2018 estimated premium income at Lloyd’s of £650,000 , at March 31, 2018 using an exchange rate of £1 equals $1.40 and assuming the maximum 3% assessment, the Company would be assessed approximately $27,300 ( December 31, 2017 : $26,325 ). (c) Unfunded investment commitments As at March 31, 2018 and December 31, 2017 , the Company had total unfunded investment commitments related to the following: Unfunded investment commitments March 31, 2018 December 31, 2017 Fixed maturity investments (a) $ 28,067 $ 22,082 Other investments (b) 87,353 86,697 Investments in investment affiliates (c) 107,386 125,996 Total unfunded investment commitments $ 222,806 $ 234,775 (a) The Company has an outstanding commitment to participate in certain secured loan facilities through participation agreements with an established loan originator. (b) The Company’s total capital commitments related to other investments as at March 31, 2018 was $268,000 ( December 31, 2017 : $268,000 ). (c) Refer to Note 4 (c), “Investments in Investment Affiliates.”

Related party transactions

Related party transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related party transactions	Related party transactions The transactions listed below are classified as related party transactions as principals and/or directors of each counterparty are members of the Company’s board of directors. (a) Aquiline Capital Partners LLC (“Aquiline Capital”) Wellington Aquiline Capital are shareholders of Wellington Insurance Company (“Wellington”) and Christopher E. Watson serves as a director of Wellington. Pursuant to reinsurance agreements with a subsidiary of Wellington, the Company recognized gross premiums written during the three months ended March 31, 2018 of $782 ( 2017 : $2,974 ) with $262 included in premiums receivable at March 31, 2018 ( December 31, 2017 : $211 ). The Company also recognized premium adjustments during the three months ended March 31, 2018 of $778 ( 2017 : $861 ). Aquiline II, Aquiline III, Aquiline Tech and Aquiline Armour Jeffrey W. Greenberg and Christopher E. Watson, directors of the Company, serve as managing principal and senior principal, respectively, of Aquiline Capital. Additional information related to the Company’s investments in Aquiline II, III, Tech and Armour is disclosed in Note 4 (c), “Investments in Investment Affiliates.” The Company had, as of March 31, 2018 and December 31, 2017 , investments in Aquiline II, III, Tech and Armour with a total value of $113,471 and $100,137 and outstanding unfunded commitments of $107,386 and $125,996 , respectively. For the three months ended March 31, 2018 , the Company incurred $132 ( 2017 : $356 ) in partnership fees associated with these investments. (b) Other Certain shareholders of the Company and their affiliates, as well as employees of entities associated with directors and officers may have purchased insurance and/or reinsurance from the Company in the ordinary course of business. The Company does not believe these transactions to be material.

Earnings per share

Earnings per share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings per common share	Earnings per common share The following table sets forth the computation of basic (loss) earnings per common share and (loss) earnings per diluted common share available to Validus common shareholders for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Basic (loss) earnings per common share Net (loss) income allocated to Validus common shareholders (4,078 ) 94,561 Weighted average number of common shares outstanding 79,325,688 79,133,671 Basic (loss) earnings per share (attributable) available to Validus common shareholders $ (0.05 ) $ 1.19 (Loss) earnings per diluted common share Net (loss) income (attributable) available to Validus common shareholders $ (4,078 ) $ 94,561 Weighted average number of common shares outstanding 79,325,688 79,133,671 Share equivalents: Stock options — 15,379 Unvested restricted shares — 1,590,092 Weighted average number of diluted common shares outstanding 79,325,688 80,739,142 (Loss) earnings per diluted common share (attributable) available to Validus common shareholders $ (0.05 ) $ 1.17 Earnings per diluted common share assumes the exercise of all dilutive stock options and restricted stock grants. Due to the net loss incurred during the three months ended March 31, 2018 , share equivalents were not included in the computation of loss per diluted share due to their anti-dilutive effect. Share equivalents that would result in the issuance of 1,503 common shares were outstanding for the three months ended March 31, 2017 , but were not included in the computation of earnings per diluted share because the effect would be anti-dilutive.

Segment information

Segment information	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment information	Segment information The Company conducts its operations worldwide through three reportable segments, which have been determined under ASC Topic 280 “Segment Reporting” to be Reinsurance, Insurance and Asset Management. The Company’s reportable segments are strategic business units that offer different products and services. They are managed and have capital allocated separately because each segment undertakes different strategies. A description of each of the Company’s reportable segments and its Corporate and Investments function is as follows: Reinsurance Segment The Reinsurance segment operates globally and is primarily focused on treaty reinsurance within the following lines and classes of business: • Property: catastrophe excess of loss, per risk excess of loss, proportional and treaty; • Specialty - Short-tail: aerospace and aviation, agriculture, composite, marine, other specialty (including contingency, crisis management and life and accident & health), technical lines, terrorism, trade credit and workers’ compensation; and • Specialty - Other: casualty and financial lines of business. Insurance Segment The Insurance segment operates globally and focuses on specialty insurance within both the Lloyd’s and the U.S. commercial insurance markets and is focused on a wide range of insurance products within the following lines and classes of business: • Property: direct property and downstream energy and power; • Specialty - Short-tail: accident & health, agriculture, aviation, contingency, marine, and political lines (including war and political violence); and • Specialty - Other: financial, liability (including general liability, professional liability, products liability and miscellaneous malpractice), marine and energy, political risk and products and airports. Asset Management Segment The Asset Management segment leverages the Company’s underwriting and analytical expertise and earns management and performance fees primarily through the management of ILS funds and sidecars. Corporate and Investments The Company’s Corporate and Investments function, which includes the activities of the parent company, carries out certain functions for the group, including investment management. Corporate and Investments includes investment income on a managed basis and other non-segment expenses, predominantly general and administrative, stock compensation, finance and transaction expenses. Transaction expenses are primarily composed of legal and financial advisory services incurred in connection with the Company’s Merger with AIG. Corporate and Investments also includes the activities of certain key executives such as the Chief Executive Officer and Chief Financial Officer. For reporting purposes, Corporate and Investments is reflected separately; however, it is not considered a reportable segment under these circumstances. Other reconciling items include, but are not limited to, the elimination of certain inter segment revenues and expenses and other items that are not allocated to the reportable segments. The following tables summarize the results of our reportable segments and “Corporate and Investments” function: Three Months Ended March 31, Reinsurance Segment Information 2018 2017 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 2 2 Total underwriting 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 Underwriting income $ 41,363 $ 84,649 Selected ratios: Ratio of net to gross premiums written 75.2 % 82.2 % Losses and loss expense ratio 46.0 % 34.9 % Policy acquisition cost ratio 21.5 % 18.8 % General and administrative expense ratio 14.1 % 9.8 % Expense ratio 35.6 % 28.6 % Combined ratio 81.6 % 63.5 % Three Months Ended March 31, Insurance Segment Information 2018 2017 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 2,170 996 Total underwriting 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 Underwriting (loss) $ (12,777 ) $ (16,361 ) Selected ratios: Ratio of net to gross premiums written 75.6 % 79.4 % Losses and loss expense ratio 61.2 % 66.9 % Policy acquisition cost ratio 20.0 % 21.9 % General and administrative expense ratio 23.7 % 17.4 % Expense ratio 43.7 % 39.3 % Combined ratio 104.9 % 106.2 % Three Months Ended March 31, Asset Management Segment Information 2018 2017 Fee revenues Third party $ 6,209 $ 4,644 Related party 443 631 Total fee revenues 6,652 5,275 Expenses General and administrative expenses 4,547 3,844 Share compensation expenses 41 82 Finance expenses 78 31 Tax (benefit) (7 ) (1 ) Foreign exchange losses (gains) 1 (1 ) Total expenses 4,660 3,955 Income before investment income from funds and sidecars 1,992 1,320 Investment income (loss) from funds and sidecars (a) AlphaCat Sidecars 32 (112 ) AlphaCat ILS Funds - Lower Risk (b) 1,234 2,189 AlphaCat ILS Funds - Higher Risk (b) 3,820 2,367 BetaCat ILS Funds 186 368 Validus' share of investment income from funds and sidecars 5,272 4,812 Asset Management segment income $ 7,264 $ 6,132 Gross premiums written AlphaCat Sidecars $ (143 ) $ 66 AlphaCat ILS Funds - Lower Risk (b) 109,950 52,908 AlphaCat ILS Funds - Higher Risk (b) 165,896 93,536 AlphaCat Direct (c) 10,922 18,416 Total $ 286,625 $ 164,926 (a) The investment income (loss) from funds and sidecars is based on equity accounting. (b) Lower risk AlphaCat ILS funds have a maximum permitted portfolio expected loss of less than 7%, whereas higher risk AlphaCat ILS funds have a maximum permitted portfolio expected loss of 7% or greater. The portfolio expected loss represents the average annual loss over the set of simulation scenarios divided by the total limit. (c) AlphaCat Direct includes direct investments from a third party investor in AlphaCat Re. Three Months Ended March 31, Corporate and Investments 2018 2017 Managed investments Managed net investment income (a) $ 39,791 $ 36,192 Net realized gains (losses) on managed investments (a) 1,142 (2,892 ) Change in net unrealized (losses) gains on managed investments (a) (56,777 ) 14,349 Income from investment affiliates 13,068 5,188 Total managed investment return $ (2,776 ) $ 52,837 Corporate expenses General and administrative expenses $ 12,309 $ 17,961 Share compensation expenses 4,036 3,413 Finance expenses (a) 14,090 13,864 Dividends on preferred shares 5,828 2,203 Tax (benefit) (a) (6,826 ) (3,548 ) Total Corporate expenses $ 29,437 $ 33,893 Other items Foreign exchange (losses) gains (a) (3 ) 1,103 Other income 44 94 Transaction expenses (7,756 ) — Total other items $ (7,715 ) $ 1,197 Total Corporate and Investments $ (39,928 ) $ 20,141 (a) These items exclude the components which are included in the Asset Management segment income (loss) and amounts which are consolidated from VIEs. The following tables reconcile the results of our reportable segments and “Corporate & Investments” function to the Consolidated results of the Company for the years indicated: Three Months Ended March 31, 2018 Reinsurance Segment Insurance Segment Asset Management Segment and Consolidated VIEs Corporate & Investments Eliminations Total Underwriting revenues Gross premiums written $ 765,573 $ 785,795 $ 286,625 $ — $ (5,537 ) $ 1,832,456 Reinsurance premiums ceded (190,194 ) (191,637 ) — — 5,537 (376,294 ) Net premiums written 575,379 594,158 286,625 — — 1,456,162 Change in unearned premiums (350,627 ) (294,620 ) (191,973 ) — — (837,220 ) Net premiums earned 224,752 299,538 94,652 — — 618,942 Other insurance related income 2 2,170 28,080 — (4,756 ) 25,496 Total underwriting revenues 224,754 301,708 122,732 — (4,756 ) 644,438 Underwriting deductions Losses and loss expenses 103,473 183,389 34,683 — — 321,545 Policy acquisition costs 48,340 60,057 8,059 — — 116,456 General and administrative expenses 28,915 68,050 10,208 12,309 (4,756 ) 114,726 Share compensation expenses 2,663 2,989 41 4,036 — 9,729 Total underwriting deductions 183,391 314,485 52,991 16,345 (4,756 ) 562,456 Underwriting income (loss) $ 41,363 $ (12,777 ) $ 69,741 $ (16,345 ) $ — $ 81,982 Net investment return (a) — — 12,735 (2,776 ) — 9,959 Other items (b) — — 362 (20,807 ) — (20,445 ) (Income) attributable to AlphaCat investors — — (10,862 ) — — (10,862 ) Net (income) attributable to noncontrolling interests — — (64,712 ) — — (64,712 ) Net income (loss) available (attributable) to Validus common shareholders $ 41,363 $ (12,777 ) $ 7,264 $ (39,928 ) $ — $ (4,078 ) (a) Net investment return includes net investment income, net realized and change in net unrealized gains (losses) on investments and income (loss) from investment affiliates. (b) 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). Three Months Ended March 31, 2017 Reinsurance Segment Insurance Segment Asset Management Segment and Consolidated VIEs Corporate & Investments Eliminations Total Underwriting revenues Gross premiums written $ 643,141 $ 382,790 $ 164,926 $ — $ — $ 1,190,857 Reinsurance premiums ceded (114,446 ) (79,000 ) (6,660 ) — — (200,106 ) Net premiums written 528,695 303,790 158,266 — — 990,751 Change in unearned premiums (297,040 ) (24,696 ) (93,639 ) — — (415,375 ) Net premiums earned 231,655 279,094 64,627 — — 575,376 Other insurance related income 2 996 5,161 — (4,923 ) 1,236 Total underwriting revenues 231,657 280,090 69,788 — (4,923 ) 576,612 Underwriting deductions Losses and loss expenses 80,881 186,610 2,094 — — 269,585 Policy acquisition costs 43,535 61,192 6,901 — — 111,628 General and administrative expenses 19,969 45,276 9,641 17,961 (4,923 ) 87,924 Share compensation expenses 2,623 3,373 82 3,413 — 9,491 Total underwriting deductions 147,008 296,451 18,718 21,374 (4,923 ) 478,628 Underwriting income (loss) $ 84,649 $ (16,361 ) $ 51,070 $ (21,374 ) $ — $ 97,984 Net investment return (a) — — 4,749 52,837 — 57,586 Other items (b) — — 388 (11,322 ) — (10,934 ) (Income) attributable to AlphaCat investors — — (7,503 ) — — (7,503 ) Net (income) attributable to noncontrolling interests — — (42,572 ) — — (42,572 ) Net income (loss) available (attributable) to Validus common shareholders $ 84,649 $ (16,361 ) $ 6,132 $ 20,141 $ — $ 94,561 (a) Net investment return includes net investment income, net realized and change in net unrealized gains (losses) on investments and income (loss) from investment affiliates. (b) 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). The Company’s exposures are generally diversified across geographic zones. The following tables set forth the gross premiums written allocated to the territory of coverage exposure for the years indicated: Gross Premiums Written Three Months Ended March 31, 2018 Reinsurance Segment Insurance Segment Asset Management Segment Eliminations Total % United States $ 200,174 $ 560,722 $ 31,023 $ (1,525 ) $ 790,394 43.1 % Worldwide excluding United States (a) 39,325 52,232 2,879 — 94,436 5.2 % Australia and New Zealand 1,136 8,177 — — 9,313 0.5 % Europe 37,982 5,560 338 — 43,880 2.4 % Latin America and Caribbean 6,539 18,445 — — 24,984 1.4 % Japan 2,100 916 431 — 3,447 0.2 % Canada 3,735 933 — — 4,668 0.3 % Rest of the world (b) 18,298 27,220 — — 45,518 2.5 % Sub-total, non United States 109,115 113,483 3,648 — 226,246 12.3 % Worldwide including United States (a) 118,809 26,655 248,114 (4,012 ) 389,566 21.3 % Other locations non-specific (c) 337,475 84,935 3,840 — 426,250 23.3 % Total $ 765,573 $ 785,795 $ 286,625 $ (5,537 ) $ 1,832,456 100.0 % Gross Premiums Written Three Months Ended March 31, 2017 Reinsurance Segment Insurance Segment Asset Management Segment Eliminations Total % United States $ 223,928 $ 190,188 $ 28,203 $ — $ 442,319 37.1 % Worldwide excluding United States (a) 35,208 32,538 7,035 — 74,781 6.3 % Australia and New Zealand 789 3,174 — — 3,963 0.3 % Europe 31,945 8,681 466 — 41,092 3.5 % Latin America and Caribbean 9,960 20,687 — — 30,647 2.6 % Japan 1,951 1,005 1,193 — 4,149 0.3 % Canada 2,358 449 — — 2,807 0.2 % Rest of the world (b) 15,103 20,392 — — 35,495 3.0 % Sub-total, non United States 97,314 86,926 8,694 — 192,934 16.2 % Worldwide including United States (a) 95,801 27,187 123,309 — 246,297 20.7 % Other locations non-specific (c) 226,098 78,489 4,720 — 309,307 26.0 % Total $ 643,141 $ 382,790 $ 164,926 $ — $ 1,190,857 100.0 % (a) Represents risks in two or more geographic zones. (b) Represents risks in one geographic zone. (c) The other locations non-specific category refers to business for which an analysis of exposure by geographic zone is not applicable since these exposures can span multiple geographic areas and, in some instances, are not fixed locations.

Significant accounting policies

Significant accounting policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of preparation	These unaudited Consolidated Financial Statements (the “Consolidated Financial Statements”) have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 in Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In addition, the year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by U.S. GAAP. This Quarterly Report on Form 10-Q should be read in conjunction with the financial statements and related notes included in Validus Holdings, Ltd.’s (the “Company”) Annual Report on Form 10-K for the year ended December 31, 2017 , as filed with the U.S. Securities and Exchange Commission (the “SEC”). In the opinion of management, these unaudited Consolidated Financial Statements reflect all adjustments (including normal recurring adjustments) considered necessary for a fair statement of the Company’s financial position and results of operations as at the end of and for the periods presented. All significant intercompany accounts and transactions have been eliminated. The results of operations for any interim period are not necessarily indicative of the results for a full year.
Use of estimates	The preparation of these Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. While the amounts included in the Consolidated Financial Statements reflect management’s best estimates and assumptions, actual results could differ from those estimates. The Company’s principal estimates include: • the reserve for losses and loss expenses; • the premium written on a line slip or proportional basis; • the valuation of goodwill and intangible assets; • the loss reserves recoverable, including the provision for uncollectible amounts; and • the valuation of invested assets and other financial instruments.
Consolidating voting interest entities and variable interest entities	The Company consolidates in these Consolidated Financial Statements the results of operations and financial position of every voting interest entity (“VOE”) in which the Company has a controlling financial interest and variable interest entity (“VIE”) in which the Company is considered to be the primary beneficiary. The consolidation assessment, including the determination as to whether an entity qualifies as a VIE or VOE, depends on the facts and circumstances surrounding each entity.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Amortized cost (or cost), gross unrealized gains and (losses) and fair value of investments	The amortized cost (or cost) and fair value of the Company’s investments as at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 December 31, 2017 Amortized Cost or Cost Fair Value Amortized Fair Value Managed investments U.S. government and government agency $ 598,080 $ 589,161 $ 733,510 $ 727,397 Non-U.S. government and government agency 318,542 318,345 310,845 312,239 U.S. states, municipalities and political subdivisions 186,551 184,964 201,347 201,303 Agency residential mortgage-backed securities 992,087 968,258 984,387 978,049 Non-agency residential mortgage-backed securities 43,522 43,487 40,264 40,373 U.S. corporate 1,553,311 1,534,805 1,531,498 1,533,395 Non-U.S. corporate 417,264 415,156 420,522 422,249 Bank loans 475,154 468,815 450,320 442,951 Asset-backed securities 744,051 741,712 657,234 658,303 Commercial mortgage-backed securities 325,058 318,392 315,002 312,395 Total fixed maturities 5,653,620 5,583,095 5,644,929 5,628,654 Short-term investments 188,306 188,251 229,968 230,011 Other investments Hedge funds 6,954 15,758 6,954 15,774 Private equity investments 64,424 79,774 63,684 78,407 Fixed income investment funds 199,802 200,944 203,167 204,426 Overseas deposits 60,770 60,770 56,611 56,611 Total other investments 331,950 357,246 330,416 355,218 Investments in investment affiliates (a) 75,302 113,471 61,944 100,137 Total managed investments $ 6,249,178 $ 6,242,063 $ 6,267,257 $ 6,314,020 Non-managed investments Catastrophe bonds $ 220,520 $ 219,927 $ 231,332 $ 229,694 Short-term investments 3,450,689 3,450,689 3,151,746 3,151,746 Total non-managed investments 3,671,209 3,670,616 3,383,078 3,381,440 Total investments $ 9,920,387 $ 9,912,679 $ 9,650,335 $ 9,695,460 (a) The Company’s investments in investment affiliates have been treated as equity method investments with the corresponding gains and losses recorded in income as “Income from investment affiliates.”
Investment ratings on fixed maturities	The following table sets forth certain information regarding Standard & Poor’s credit quality ratings (or an equivalent rating with another recognized rating agency) of the Company’s fixed maturity investments as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Fair Value % of Total Fair Value % of Total Managed fixed maturities AAA $ 2,648,321 45.7 % $ 2,715,074 46.4 % AA 419,695 7.2 % 442,397 7.6 % A 1,159,233 20.0 % 1,137,795 19.4 % BBB 830,866 14.3 % 828,392 14.1 % Total investment grade managed fixed maturities 5,058,115 87.2 % 5,123,658 87.5 % BB 170,818 2.9 % 168,967 2.9 % B 240,099 4.1 % 237,131 4.0 % CCC 21,783 0.4 % 18,217 0.3 % NR 92,280 1.6 % 80,681 1.4 % Total non-investment grade managed fixed maturities 524,980 9.0 % 504,996 8.6 % Total managed fixed maturities $ 5,583,095 96.2 % $ 5,628,654 96.1 % Non-managed catastrophe bonds BB 21,607 0.4 % 22,110 0.3 % B 2,379 — % 3,265 0.1 % NR 195,941 3.4 % 204,319 3.5 % Total non-investment grade non-managed catastrophe bonds 219,927 3.8 % 229,694 3.9 % Total non-managed catastrophe bonds 219,927 3.8 % 229,694 3.9 % Total fixed maturities $ 5,803,022 100.0 % $ 5,858,348 100.0 %
Fixed maturities investments by contractual maturity	The amortized cost and fair values for the Company’s fixed maturity investments held at March 31, 2018 and December 31, 2017 are shown below by contractual maturity. Actual maturity may differ from contractual maturity due to prepayment rights associated with certain investments. March 31, 2018 December 31, 2017 Amortized Cost or Cost Fair Value Amortized Cost or Cost Fair Value Managed fixed maturities Due in one year or less $ 346,118 $ 344,749 $ 343,360 $ 343,541 Due after one year through five years 2,453,565 2,424,185 2,527,018 2,513,620 Due after five years through ten years 560,679 554,188 577,347 577,109 Due after ten years 188,540 188,124 200,317 205,264 3,548,902 3,511,246 3,648,042 3,639,534 Asset-backed and mortgage-backed securities 2,104,718 2,071,849 1,996,887 1,989,120 Total managed fixed maturities $ 5,653,620 $ 5,583,095 $ 5,644,929 $ 5,628,654 Non-managed catastrophe bonds Due in one year or less $ 67,370 $ 67,926 $ 88,797 $ 88,367 Due after one year through five years 147,400 146,238 140,035 138,844 Due after five years through ten years 5,750 5,763 2,500 2,483 Total non-managed catastrophe bonds 220,520 219,927 231,332 229,694 Total fixed maturities $ 5,874,140 $ 5,803,022 $ 5,876,261 $ 5,858,348
Other investments	The following tables set forth certain information regarding the Company’s other investment portfolio as at March 31, 2018 and December 31, 2017 : March 31, 2018 Fair Value Investments with redemption restrictions Investments without redemption restrictions Redemption frequency (a) Redemption notice period (a) Hedge funds $ 15,758 $ 15,758 $ — Private equity investments 79,774 79,774 — Fixed income investment funds 200,944 200,944 — Overseas deposits 60,770 60,770 — Total other investments $ 357,246 $ 357,246 $ — December 31, 2017 Fair Value Investments with redemption restrictions Investments without redemption restrictions Redemption frequency (a) Redemption notice period (a) Hedge funds 15,774 15,774 — Private equity investments 78,407 78,407 — Fixed income investment funds 204,426 200,532 3,894 Daily Daily to 2 days Overseas deposits 56,611 56,611 — Total other investments $ 355,218 $ 351,324 $ 3,894 (a) The redemption frequency and notice periods only apply to investments without redemption restrictions.
Reconciliation of beginning and ending investment in affiliate balances	The following table presents a reconciliation of the Company’s beginning and ending investments in investment affiliates for three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Investment affiliates, beginning of year $ 100,137 $ 100,431 Net capital contributions (distributions) 266 (10,922 ) Income from investment affiliates 13,068 5,188 Investment affiliates, end of year $ 113,471 $ 94,697
Schedule of equity method investments	The following table presents the Company’s investments in the Aquiline partnerships as at March 31, 2018 and December 31, 2017 : March 31, 2018 Investment at cost Voting ownership % Equity ownership % Carrying value Aquiline II $ 33,008 — % 8.1 % $ 49,208 Aquiline III 24,737 — % 9.0 % 47,114 Aquiline Tech 3,858 — % 10.6 % 3,450 Aquiline Armour 13,699 — % 15.2 % 13,699 Total investments in investment affiliates $ 75,302 $ 113,471 December 31, 2017 Investment at cost Voting ownership % Equity ownership % Carrying value Aquiline II $ 33,349 — % 8.1 % $ 51,914 Aquiline III 24,737 — % 9.0 % 44,733 Aquiline Tech 3,858 — % 10.6 % 3,490 Total investments in investment affiliates $ 61,944 $ 100,137
Net investment income	Net investment income was derived from the following sources: Three Months Ended March 31, 2018 2017 Managed investments Fixed maturities and short-term investments $ 37,769 $ 31,671 Other investments 4,223 6,870 Cash and cash equivalents and restricted cash 1,139 610 Securities lending income 3 13 Total gross investment income 43,134 39,164 Investment expenses (3,343 ) (2,972 ) Total managed net investment income $ 39,791 $ 36,192 Non managed investments Fixed maturities and short-term investments $ 4,148 $ 3,060 Cash and cash equivalents and restricted cash 8,133 962 Total non-managed net investment income 12,281 4,022 Total net investment income $ 52,072 $ 40,214
Analysis of net realized gains and the change in net unrealized gains (losses) on investments	The following table sets forth an analysis of net realized gains (losses) and the change in net unrealized (losses) gains on investments: Three Months Ended March 31, 2018 2017 Managed investments Gross realized gains $ 6,830 $ 2,690 Gross realized (losses) (5,688 ) (5,582 ) Net realized gains (losses) on investments 1,142 (2,892 ) Change in net unrealized (losses) gains on investments (56,777 ) 14,349 Total net realized and change in net unrealized (losses) gains on managed investments $ (55,635 ) $ 11,457 Non-managed investments Gross realized gains $ 1,235 $ 1,728 Gross realized (losses) (177 ) — Net realized gains on investments 1,058 1,728 Change in net unrealized (losses) on investments (604 ) (1,001 ) Total net realized and change in net unrealized gains on non-managed investments 454 727 Total net realized and change in net unrealized (losses) gains on total investments $ (55,181 ) $ 12,184

Fair value measurements (Tables

Fair value measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair value hierarchy - allocation of investments	At March 31, 2018 , the Company’s investments were allocated between Levels 1, 2 and 3 as follows: Level 1 Level 2 Level 3 Fair value based on NAV practical expedient (a) Total Managed investments U.S. government and government agency $ — $ 589,161 $ — $ — $ 589,161 Non-U.S. government and government agency — 318,345 — — 318,345 U.S. states, municipalities and political subdivisions — 184,964 — — 184,964 Agency residential mortgage-backed securities — 968,258 — — 968,258 Non-agency residential mortgage-backed securities — 43,487 — — 43,487 U.S. corporate — 1,534,805 — — 1,534,805 Non-U.S. corporate — 415,156 — — 415,156 Bank loans — 241,312 227,503 — 468,815 Asset-backed securities — 639,896 101,816 — 741,712 Commercial mortgage-backed securities — 318,392 — — 318,392 Total fixed maturities — 5,253,776 329,319 — 5,583,095 Short-term investments 175,526 12,725 — — 188,251 Other investments Hedge funds — — — 15,758 15,758 Private equity investments — — — 79,774 79,774 Fixed income investment funds — 9,458 17,933 173,553 200,944 Overseas deposits — — — 60,770 60,770 Total other investments — 9,458 17,933 329,855 357,246 Investments in investment affiliates (b) — — — — 113,471 Total managed investments $ 175,526 $ 5,275,959 $ 347,252 $ 329,855 $ 6,242,063 Non-managed investments Catastrophe bonds $ — $ 154,230 $ 65,697 $ — $ 219,927 Short-term investments 3,450,689 — — — 3,450,689 Total non-managed investments 3,450,689 154,230 65,697 — 3,670,616 Total investments $ 3,626,215 $ 5,430,189 $ 412,949 $ 329,855 $ 9,912,679 (a) In accordance with ASC Topic 820 “Fair Value Measurements,” investments measured at fair value using the net asset value (“NAV”) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. (b) In accordance with ASC Topic 825 “Financial Instruments,” the Company’s investments in investment affiliates have not been classified in the fair value hierarchy. At December 31, 2017 , the Company’s investments were allocated between Levels 1, 2 and 3 as follows: Level 1 Level 2 Level 3 Fair value based on NAV practical expedient (a) Total Managed investments U.S. government and government agency $ — $ 727,397 $ — $ — $ 727,397 Non-U.S. government and government agency — 312,239 — — 312,239 U.S. states, municipalities and political subdivisions — 201,303 — — 201,303 Agency residential mortgage-backed securities — 978,049 — — 978,049 Non-agency residential mortgage-backed securities — 40,373 — — 40,373 U.S. corporate — 1,533,395 — — 1,533,395 Non-U.S. corporate — 422,249 — — 422,249 Bank loans — 232,886 210,065 — 442,951 Asset-backed securities — 554,490 103,813 — 658,303 Commercial mortgage-backed securities — 312,395 — — 312,395 Total fixed maturities — 5,314,776 313,878 — 5,628,654 Short-term investments 198,054 31,957 — — 230,011 Other investments Hedge funds — — — 15,774 15,774 Private equity investments — — — 78,407 78,407 Fixed income investment funds — 13,351 17,404 173,671 204,426 Overseas deposits — — — 56,611 56,611 Total other investments — 13,351 17,404 324,463 355,218 Investments in investment affiliates (b) — — — — 100,137 Total managed investments $ 198,054 $ 5,360,084 $ 331,282 $ 324,463 $ 6,314,020 Non-managed investments Catastrophe bonds $ — $ 152,233 $ 77,461 $ — $ 229,694 Short-term investments 3,151,746 — — — 3,151,746 Total non-managed investments 3,151,746 152,233 77,461 — 3,381,440 Total investments $ 3,349,800 $ 5,512,317 $ 408,743 $ 324,463 $ 9,695,460 (a) In accordance with ASC Topic 820 “Fair Value Measurements,” investments measured at fair value using the net asset value (“NAV”) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. (b) In accordance with ASC Topic 825 “Financial Instruments,” the Company’s investments in investment affiliates have not been classified in the fair value hierarchy.
Reconciliation of beginning and ending balances for all Level 3 investments measured at fair value on recurring basis	The following table presents a reconciliation of the beginning and ending balances for all investments measured at fair value on a recurring basis using Level 3 inputs during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 Bank Loans Catastrophe Bonds Fixed Income Investment Funds Asset Backed Securities Total Level 3 investments, beginning of period $ 210,065 $ 77,461 $ 17,404 $ 103,813 $ 408,743 Purchases 30,785 18,825 529 — 50,139 Sales — — — (70 ) (70 ) Settlements (13,842 ) (31,484 ) — — (45,326 ) Realized gains — 1,235 — — 1,235 Change in net unrealized gains (losses) 495 (340 ) — (1,927 ) (1,772 ) Level 3 investments, end of period $ 227,503 $ 65,697 $ 17,933 $ 101,816 $ 412,949 Three Months Ended March 31, 2017 Bank Loans Catastrophe Bonds Fixed Income Investment Funds Asset Backed Securities Total Level 3 investments, beginning of period $ 246,496 $ 48,375 $ 12,168 $ 23,931 $ 330,970 Purchases 23,176 61,091 — — 84,267 Settlements (33,110 ) (38,780 ) 392 — (71,498 ) Realized gains — 3,134 — — 3,134 Change in net unrealized gains (losses) 132 (1,144 ) — (49 ) (1,061 ) Level 3 investments, end of period $ 236,694 $ 72,676 $ 12,560 $ 23,882 $ 345,812

Variable interest entities (Tab

Variable interest entities (Tables)	3 Months Ended
	Mar. 31, 2018
Variable Interest Entities Disclosure [Abstract]
Summary of notes payable to variable interest entities	The following tables present reconciliations of the beginning and ending notes payable to AlphaCat investors during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 Variable Funding Notes Structured Notes Total Notes payable to AlphaCat investors, beginning of period $ 936,164 $ 172,200 $ 1,108,364 Issuance of notes payable to AlphaCat investors 506,540 179,972 686,512 Redemption of notes payable to AlphaCat investors (530,546 ) — (530,546 ) Foreign exchange losses 3,864 — 3,864 Notes payable to AlphaCat investors, end of period $ 916,022 $ 352,172 $ 1,268,194 Three Months Ended March 31, 2017 Variable Funding Notes Structured Notes Total Notes payable to AlphaCat investors, beginning of period $ 278,202 $ — $ 278,202 Issuance of notes payable to AlphaCat investors 274,010 103,320 377,330 Redemption of notes payable to AlphaCat investors (208,956 ) — (208,956 ) Notes payable to AlphaCat investors, end of period $ 343,256 $ 103,320 $ 446,576
Total assets and liabilities of the Company's consolidated VIEs	The following table presents the total assets and total liabilities of the Company’s consolidated VIEs, excluding intercompany eliminations, as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Total Assets Total Liabilities Total Assets Total Liabilities AlphaCat sidecars $ 25,952 $ 3,071 $ 25,975 $ 3,267 AlphaCat ILS funds - Lower Risk 1,046,458 11,156 1,107,503 259,630 AlphaCat ILS funds - Higher Risk 1,431,945 676,225 1,310,071 912,341 AlphaCat Re and AlphaCat Master Fund 3,878,359 3,878,189 3,398,082 3,397,912 BetaCat ILS funds 104,857 2,207 77,221 261

Noncontrolling interest (Tables

Noncontrolling interest (Tables)	3 Months Ended
	Mar. 31, 2018
Noncontrolling Interest [Abstract]
Reconciliation of beginning and ending balances of noncontrolling interest and redeemable noncontrolling interest	The following tables present a reconciliation of the beginning and ending balances of redeemable noncontrolling interests and noncontrolling interests for the three months ended March 31, 2018 and 2017 : Redeemable Noncontrolling Interests Noncontrolling Interests Total Three Months Ended March 31, Three Months Ended March 31, Three Months Ended March 31, 2018 2017 2018 2017 2018 2017 Balance, beginning of period $ 1,004,094 $ 1,528,001 $ 16,718 $ 165,977 $ 1,020,812 $ 1,693,978 Issuance of shares 385,300 103,699 281,300 154,980 666,600 258,679 Income attributable to noncontrolling interests 28,373 25,930 36,339 16,642 64,712 42,572 Redemption of shares / Distributions 5,343 — — (7,002 ) 5,343 (7,002 ) Balance, end of period $ 1,423,110 $ 1,657,630 $ 334,357 $ 330,597 $ 1,757,467 $ 1,988,227

Derivative instruments (Tables)

Derivative instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Not designated as hedging instruments
Derivative [Line Items]
Location and fair value amount of derivative instruments reported on the balance sheet	The following tables summarize information on the classification and amount of the fair value of derivatives not designated as hedging instruments within the Company’s Consolidated Balance Sheets as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Derivatives not designated as hedging instruments Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Foreign currency forward contracts $ 239,398 $ 1,945 $ 433 $ 283,765 $ 1,147 $ 906 Interest rate swap contracts $ 200,000 $ 7,357 $ — $ 200,000 $ 1,589 $ — Weather derivative contracts $ 4,825 $ 26,958 $ — $ 4,825 $ 853 $ — (a) Asset and liability derivative positions are classified within other assets and accounts payable and accrued expenses, respectively, within the Company’s Consolidated Balance Sheets.
Location and amount of gains and losses related to derivative instruments reported on in the income statement	The following table summarizes information on the classification and net impact on earnings recognized in the Company’s Consolidated Statements of Income and Comprehensive Income relating to derivatives that were not designated as hedging instruments during the three months ended March 31, 2018 and 2017 : Derivatives not designated as hedging instruments Classification of gains recognized in earnings Three Months Ended March 31, 2018 2017 Foreign currency forward contracts Foreign exchange (losses) gains $ (5,201 ) $ 453 Foreign currency forward contracts Other insurance related income and other income $ — $ (105 ) Interest rate swap contracts Net realized gains on investments $ 5,944 $ — Weather derivative contracts Other insurance related income and other income $ 26,773 $ —
Designated as hedging instruments
Derivative [Line Items]
Location and fair value amount of derivative instruments reported on the balance sheet	The following table summarizes information on the classification and amount of the fair value of derivatives designated as hedging instruments on the Consolidated Balance Sheets as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Derivatives designated as hedging instruments Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Notional Exposure Asset Derivative at Fair Value (a) Liability Derivative at Fair Value (a) Interest rate swap contracts $ 552,263 $ 23,256 $ 4,931 $ 552,263 $ 9,806 $ 18,840 Foreign currency forward contracts $ 80,373 $ 4,503 $ — $ 96,293 $ 1,891 $ — (a) Asset and liability derivative positions are classified within other assets and accounts payable and accrued expenses, respectively, within the Company’s Consolidated Balance Sheets
Location and amount of gains and losses related to derivative instruments reported on in the income statement	The following tables provide the total impact on other comprehensive income and earnings relating to the derivative instruments formally designated as cash flow hedges for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, Interest rate swap contracts 2018 2017 Amount recognized in other comprehensive income $ 25,843 $ 98 Amount reclassified to finance expenses $ 1,343 $ — Three Months Ended March 31, Foreign currency forward contracts 2018 2017 Amount recognized in other comprehensive income $ 2,920 $ — Amount reclassified to general and administrative expenses $ (308 ) $ —

Reserve for losses and loss e31

Reserve for losses and loss expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract]
Summary of reserve for losses and loss expenses	The following table summarizes the Company’s reserve for losses and loss expenses as at March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Case reserves $ 1,770,278 $ 1,753,844 IBNR 2,862,351 3,077,546 Reserve for losses and loss expenses $ 4,632,629 $ 4,831,390
Reserve for losses and loss expenses	The following table represents an analysis of paid and unpaid losses and loss expenses incurred and a reconciliation of the beginning and ending unpaid losses and loss expenses for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Reserve for losses and loss expenses, beginning of period $ 4,831,390 $ 2,995,195 Loss reserves recoverable (1,233,997 ) (430,421 ) Net reserves for losses and loss expenses, beginning of period 3,597,393 2,564,774 Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in: Current year 329,115 330,816 Prior years (7,570 ) (61,231 ) Total incurred losses and loss expenses 321,545 269,585 Foreign exchange loss 15,627 12,317 Less net losses and loss expenses paid in respect of losses occurring in: Current year (19,735 ) (7,698 ) Prior years (262,145 ) (238,089 ) Total net paid losses (281,880 ) (245,787 ) Net reserve for losses and loss expenses, end of period 3,652,685 2,600,889 Loss reserves recoverable 979,944 451,856 Reserve for losses and loss expenses, end of period $ 4,632,629 $ 3,052,745 Incurred losses and loss expenses comprise: Three Months Ended March 31, 2018 2017 Gross losses and loss expenses $ 248,781 $ 336,442 Reinsurance recoveries 72,764 (66,857 ) Net incurred losses and loss expenses $ 321,545 $ 269,585
Prior year development by segment and line of business	The net (favorable) adverse development on prior accident years by segment and line of business for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 Property Specialty - Short-tail Specialty - Other Total Reinsurance Segment $ (4,822 ) $ (13,451 ) $ 435 $ (17,838 ) Insurance Segment 4,068 (12,201 ) (7,415 ) (15,548 ) Asset Management Segment 25,200 616 — 25,816 Net adverse (favorable) development $ 24,446 $ (25,036 ) $ (6,980 ) $ (7,570 ) Three Months Ended March 31, 2017 Property Specialty - Short-tail Specialty - Other Total Reinsurance Segment $ (4,062 ) $ (26,748 ) $ (314 ) $ (31,124 ) Insurance Segment (8,666 ) (11,763 ) (6,260 ) (26,689 ) Asset Management Segment (4,395 ) 977 — (3,418 ) Net favorable development $ (17,123 ) $ (37,534 ) $ (6,574 ) $ (61,231 )

Reinsurance (Tables)

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2018
Reinsurance Disclosures [Abstract]
Schedule of reinsurance recoverable	The Company’s reinsurance balances recoverable at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 December 31, 2017 Loss reserves recoverable on unpaid: Case reserves $ 235,814 $ 275,450 IBNR 744,130 958,547 Total loss reserves recoverable 979,944 1,233,997 Paid losses recoverable 59,892 46,873 Total reinsurance recoverable $ 1,039,836 $ 1,280,870
Reinsurance recoverables by reinsurer	Information regarding the Company’s concentration of credit risk arising from its exposure to individual reinsurers as at March 31, 2018 and December 31, 2017 is as follows: March 31, 2018 December 31, 2017 Reinsurance Recoverable % of Total Reinsurance Recoverable % of Total Top 10 reinsurers $ 878,685 84.5 % $ 1,055,445 82.5 % Other reinsurers’ balances > $1 million 153,572 14.8 % 218,226 17.0 % Other reinsurers’ balances < $1 million 7,579 0.7 % 7,199 0.5 % Total $ 1,039,836 100.0 % $ 1,280,870 100.0 % March 31, 2018 Top 10 Reinsurers Rating Reinsurance Recoverable % of Total Fully collateralized reinsurers NR $ 407,361 39.2 % Everest Re A+ 128,360 12.3 % Lloyd's Syndicates A+ 69,885 6.7 % Swiss Re AA- 56,892 5.5 % Munich Re AA- 50,097 4.8 % Hannover Re AA- 49,501 4.8 % Transatlantic Re A+ 38,446 3.7 % Qatar Insurance Company A 30,981 3.0 % Markel A 25,893 2.5 % XL Catlin A+ 21,269 2.0 % Total $ 878,685 84.5 % NR: Not rated December 31, 2017 Top 10 Reinsurers Rating Reinsurance Recoverable % of Total Fully collateralized reinsurers NR $ 459,339 35.9 % Everest Re A+ 128,206 10.0 % Munich Re AA- 94,180 7.4 % Lloyd's Syndicates A+ 74,277 5.8 % Federal Crop Insurance Corporation (a) 68,745 5.4 % Swiss Re AA- 65,218 5.1 % Hannover Re AA- 53,523 4.2 % Qatar Insurance Company A 50,160 3.9 % Transatlantic Re A+ 33,729 2.6 % Markel A 28,068 2.2 % Total $ 1,055,445 82.5 % NR: Not rated (a) The Company participates in a crop reinsurance program sponsored by the U.S. federal government. The Company remains obligated for amounts ceded in the event that its reinsurers or retrocessionaires do not meet their obligations, except for amounts ceded to the U.S. federal government in the Insurance segment agriculture line of business.

Share capital (Tables)

Share capital (Tables)	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Summary of common shares issued and outstanding	The following table is a summary of the common shares issued and outstanding during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Common shares issued, beginning of period 161,994,491 161,279,976 Restricted share awards vested, net of shares withheld 7,423 3,440 Restricted share units vested, net of shares withheld 2,055 1,995 Common shares issued, end of period 162,003,969 161,285,411 Treasury shares, end of period (82,674,941 ) (82,147,821 ) Common shares outstanding, end of period 79,329,028 79,137,590

Stock plans (Tables)

Stock plans (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options, activity during the period	Activity with respect to options for the three months ended March 31, 2017 was as follows: Options Weighted Average Grant Date Fair Value Weighted Average Grant Date Exercise Price Options outstanding, beginning and end of period 26,136 $ 6.78 $ 23.48
Restricted shares awards, activity during the period	Activity with respect to unvested restricted share awards for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 2017 Restricted Share Awards Weighted Average Grant Date Fair Value Restricted Share Awards Weighted Average Grant Date Fair Value Restricted share awards outstanding, beginning of period 2,080,397 $ 43.66 2,469,982 $ 40.89 Restricted share awards granted 1,552 67.64 2,082 57.66 Restricted share awards vested (8,092 ) 44.49 (4,571 ) 37.93 Restricted share awards forfeited (6,138 ) 47.46 (513 ) 48.69 Restricted share awards outstanding, end of period 2,067,719 $ 43.66 2,466,980 $ 40.91
Restricted share units, activity during the period	Activity with respect to unvested restricted share units for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 2017 Restricted Share Units Weighted Average Grant Date Fair Value Restricted Share Units Weighted Average Grant Date Fair Value Restricted share units outstanding, beginning of period 109,394 $ 42.20 112,808 $ 40.95 Restricted share units vested (2,178 ) 38.24 (2,115 ) 38.24 Restricted share units issued in lieu of cash dividends 886 42.20 717 40.95 Restricted share units forfeited (1 ) 38.24 — — Restricted share units outstanding, end of period 108,101 $ 42.28 111,410 $ 41.01
Performance share awards, activity during the period	Activity with respect to unvested performance share awards for the three months ended March 31, 2018 and 2017 was as follows: Three Months Ended March 31, 2018 2017 Performance Share Awards Weighted Average Grant Date Fair Value Performance Share Awards Weighted Average Grant Date Fair Value Performance share awards outstanding, beginning of period 314,068 $ 49.37 285,820 $ 44.53 Performance share awards conversion adjustment — — (26,322 ) 36.82 Performance share awards outstanding, end of period 314,068 $ 49.37 259,498 $ 45.26
Total share compensation expenses	The breakdown of share compensation expenses by award type is as follows: Three Months Ended March 31, 2018 2017 Restricted share awards $ 8,113 $ 9,044 Restricted share units 332 315 Performance share awards 1,284 132 Total $ 9,729 $ 9,491

Debt and financing arrangemen35

Debt and financing arrangements (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Summary of outstanding debentures and senior notes payable	The Company’s outstanding debentures and senior notes payable as at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 December 31, 2017 Deferrable debentures 2006 Junior Subordinated $ 150,000 $ 150,000 2007 Junior Subordinated 139,800 139,800 Flagstone 2006 Junior Subordinated 136,022 135,608 Flagstone 2007 Junior Subordinated 113,750 113,750 Total debentures payable 539,572 539,158 2010 Senior Notes due 2040 250,000 250,000 Less: Unamortized debt issuance costs (4,386 ) (4,436 ) Total senior notes payable 245,614 245,564 Total debentures and senior notes payable $ 785,186 $ 784,722
Summary of key terms of debentures and senior notes	The following table summarizes the key terms of the Company’s Senior Notes and Junior Subordinated deferrable debentures: Description Issuance date Issued Maturity date Interest Rate as at Interest payments due Issuance Date March 31, 2018 2006 Junior Subordinated Deferrable Debentures June 15, 2006 $ 150,000 June 15, 2036 9.069 % (a) 5.831 % (e) Quarterly Flagstone 2006 Junior Subordinated Deferrable Debentures August 23, 2006 $ 136,022 September 15, 2036 3.540 % (b) 6.463 % (e) Quarterly 2007 Junior Subordinated Deferrable Debentures June 21, 2007 $ 200,000 June 15, 2037 8.480 % (c) 5.180 % (e) Quarterly Flagstone 2007 Junior Subordinated Deferrable Debentures June 8, 2007 $ 100,000 July 30, 2037 3.000 % (b) 5.900 % (e) Quarterly Flagstone 2007 Junior Subordinated Deferrable Debentures September 20, 2007 $ 25,000 September 15, 2037 3.100 % (b) 5.983 % (e) Quarterly 2010 Senior Notes due 2040 January 26, 2010 $ 250,000 January 26, 2040 8.875 % (d) 8.875 % (d) Semi-annually in arrears (a) Fixed interest rate for 5 years , floating interest rate of three-month LIBOR plus 3.550% thereafter, reset quarterly. (b) Floating interest rate of three-month LIBOR plus amount stated, reset quarterly. (c) Fixed interest rate for 5 years , floating interest rate of three-month LIBOR plus 2.950% thereafter, reset quarterly. (d) Fixed interest rate. (e) Fixed interest rate as a result of interest rate swap contracts entered into by the Company.
Summary of outstanding credit and other facilities	The Company’s outstanding credit facilities as at March 31, 2018 and December 31, 2017 were as follows: March 31, 2018 Credit facility Commitment Outstanding (a) Drawn (b) Cash and investments pledged as collateral $85,000 syndicated unsecured letter of credit facility $ 85,000 $ — $ — $ — $300,000 syndicated secured letter of credit facility 300,000 98,419 — 123,468 $100,000 secured bi-lateral letter of credit facility 100,000 4,407 — 22,364 $25,000 IPC bi-lateral facility 25,000 7,705 — — $236,000 Flagstone bi-lateral facility 236,000 109,796 — 156,058 $65,000 unsecured revolving credit facility 65,000 — — — $100,000 unsecured revolving credit facility 100,000 — — — FHLB secured facility 433,165 206,000 206,000 238,349 Total credit facilities $ 1,344,165 $ 426,327 $ 206,000 $ 540,239 (a) Indicates utilization of commitment amount. (b) Represents drawn borrowings included in accounts payable and accrued expenses. December 31, 2017 Credit facility Commitment Outstanding (a) Drawn (b) Cash and investments pledged as collateral $85,000 syndicated unsecured letter of credit facility $ 85,000 $ — $ — $ — $300,000 syndicated secured letter of credit facility 300,000 92,979 — 118,188 $24,000 secured bi-lateral letter of credit facility 24,000 5,765 — 22,340 $25,000 IPC bi-lateral facility 25,000 7,754 — — $236,000 Flagstone bi-lateral facility 236,000 115,682 — 184,569 $65,000 unsecured revolving credit facility 65,000 — — — $100,000 unsecured revolving credit facility 100,000 — — — FHLB secured facility 484,096 206,000 206,000 251,767 Total credit facilities $ 1,319,096 $ 428,180 $ 206,000 $ 576,864 (a) Indicates utilization of commitment amount. (b) Represents drawn borrowings included in accounts payable and accrued expenses.
Components of finance expenses	Finance expenses consist of interest on the Junior Subordinated Deferrable Debentures and the 2010 Senior Notes, the amortization of debt offering costs, credit facility fees, bank and other charges and AlphaCat financing fees as follows: Three Months Ended March 31, 2018 2017 2006 Junior Subordinated Deferrable Debentures $ 2,186 $ 2,187 2007 Junior Subordinated Deferrable Debentures 1,810 1,810 Flagstone 2006 Junior Subordinated Deferrable Debentures 2,227 2,221 Flagstone 2007 Junior Subordinated Deferrable Debentures 1,713 1,723 2010 Senior Notes 5,597 5,597 Credit facilities 416 218 Bank and other charges 263 151 AlphaCat fees (a) 51 36 Total finance expenses $ 14,263 $ 13,943 (a) Includes finance expenses incurred by AlphaCat Managers Ltd. in relation to fund raising for the AlphaCat sidecars, the AlphaCat ILS funds and AlphaCat direct.

Accumulated other comprehensi36

Accumulated other comprehensive loss (Tables)	3 Months Ended
	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of changes in accumulated other comprehensive loss	The changes in accumulated other comprehensive income (loss), by component for the three months ended March 31, 2018 and 2017 are as follows: Three Months Ended March 31, 2018 Foreign currency translation adjustment Minimum pension liability Cash flow hedge Total Balance, net of tax, beginning of period $ (18,217 ) $ 2,719 $ (6,694 ) $ (22,192 ) Other comprehensive income (loss), net of tax 1,837 (38 ) 28,763 30,562 Amounts reclassified from accumulated other comprehensive income — — 1,035 1,035 Balance, net of tax, end of period $ (16,380 ) $ 2,681 $ 23,104 $ 9,405 Three Months Ended March 31, 2017 Foreign currency translation adjustment Minimum pension liability Cash flow hedge Total Balance, net of tax, beginning of period $ (22,274 ) $ (150 ) $ (792 ) $ (23,216 ) Other comprehensive income, net of tax 597 68 98 763 Balance, net of tax, end of period $ (21,677 ) $ (82 ) $ (694 ) $ (22,453 )

Commitments and contingencies (

Commitments and contingencies (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Unfunded investment commitments	As at March 31, 2018 and December 31, 2017 , the Company had total unfunded investment commitments related to the following: Unfunded investment commitments March 31, 2018 December 31, 2017 Fixed maturity investments (a) $ 28,067 $ 22,082 Other investments (b) 87,353 86,697 Investments in investment affiliates (c) 107,386 125,996 Total unfunded investment commitments $ 222,806 $ 234,775 (a) The Company has an outstanding commitment to participate in certain secured loan facilities through participation agreements with an established loan originator. (b) The Company’s total capital commitments related to other investments as at March 31, 2018 was $268,000 ( December 31, 2017 : $268,000 ). (c) Refer to Note 4 (c), “Investments in Investment Affiliates.”

Earnings per share (Tables)

Earnings per share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Computation of basic and diluted earnings per share	The following table sets forth the computation of basic (loss) earnings per common share and (loss) earnings per diluted common share available to Validus common shareholders for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Basic (loss) earnings per common share Net (loss) income allocated to Validus common shareholders (4,078 ) 94,561 Weighted average number of common shares outstanding 79,325,688 79,133,671 Basic (loss) earnings per share (attributable) available to Validus common shareholders $ (0.05 ) $ 1.19 (Loss) earnings per diluted common share Net (loss) income (attributable) available to Validus common shareholders $ (4,078 ) $ 94,561 Weighted average number of common shares outstanding 79,325,688 79,133,671 Share equivalents: Stock options — 15,379 Unvested restricted shares — 1,590,092 Weighted average number of diluted common shares outstanding 79,325,688 80,739,142 (Loss) earnings per diluted common share (attributable) available to Validus common shareholders $ (0.05 ) $ 1.17

Segment information (Tables)

Segment information (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Summary of results of operating segments and Corporate and Investments	The following tables summarize the results of our reportable segments and “Corporate and Investments” function: Three Months Ended March 31, Reinsurance Segment Information 2018 2017 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 2 2 Total underwriting 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 Underwriting income $ 41,363 $ 84,649 Selected ratios: Ratio of net to gross premiums written 75.2 % 82.2 % Losses and loss expense ratio 46.0 % 34.9 % Policy acquisition cost ratio 21.5 % 18.8 % General and administrative expense ratio 14.1 % 9.8 % Expense ratio 35.6 % 28.6 % Combined ratio 81.6 % 63.5 % Three Months Ended March 31, Insurance Segment Information 2018 2017 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 2,170 996 Total underwriting 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 Underwriting (loss) $ (12,777 ) $ (16,361 ) Selected ratios: Ratio of net to gross premiums written 75.6 % 79.4 % Losses and loss expense ratio 61.2 % 66.9 % Policy acquisition cost ratio 20.0 % 21.9 % General and administrative expense ratio 23.7 % 17.4 % Expense ratio 43.7 % 39.3 % Combined ratio 104.9 % 106.2 % Three Months Ended March 31, Asset Management Segment Information 2018 2017 Fee revenues Third party $ 6,209 $ 4,644 Related party 443 631 Total fee revenues 6,652 5,275 Expenses General and administrative expenses 4,547 3,844 Share compensation expenses 41 82 Finance expenses 78 31 Tax (benefit) (7 ) (1 ) Foreign exchange losses (gains) 1 (1 ) Total expenses 4,660 3,955 Income before investment income from funds and sidecars 1,992 1,320 Investment income (loss) from funds and sidecars (a) AlphaCat Sidecars 32 (112 ) AlphaCat ILS Funds - Lower Risk (b) 1,234 2,189 AlphaCat ILS Funds - Higher Risk (b) 3,820 2,367 BetaCat ILS Funds 186 368 Validus' share of investment income from funds and sidecars 5,272 4,812 Asset Management segment income $ 7,264 $ 6,132 Gross premiums written AlphaCat Sidecars $ (143 ) $ 66 AlphaCat ILS Funds - Lower Risk (b) 109,950 52,908 AlphaCat ILS Funds - Higher Risk (b) 165,896 93,536 AlphaCat Direct (c) 10,922 18,416 Total $ 286,625 $ 164,926 (a) The investment income (loss) from funds and sidecars is based on equity accounting. (b) Lower risk AlphaCat ILS funds have a maximum permitted portfolio expected loss of less than 7%, whereas higher risk AlphaCat ILS funds have a maximum permitted portfolio expected loss of 7% or greater. The portfolio expected loss represents the average annual loss over the set of simulation scenarios divided by the total limit. (c) AlphaCat Direct includes direct investments from a third party investor in AlphaCat Re. Three Months Ended March 31, Corporate and Investments 2018 2017 Managed investments Managed net investment income (a) $ 39,791 $ 36,192 Net realized gains (losses) on managed investments (a) 1,142 (2,892 ) Change in net unrealized (losses) gains on managed investments (a) (56,777 ) 14,349 Income from investment affiliates 13,068 5,188 Total managed investment return $ (2,776 ) $ 52,837 Corporate expenses General and administrative expenses $ 12,309 $ 17,961 Share compensation expenses 4,036 3,413 Finance expenses (a) 14,090 13,864 Dividends on preferred shares 5,828 2,203 Tax (benefit) (a) (6,826 ) (3,548 ) Total Corporate expenses $ 29,437 $ 33,893 Other items Foreign exchange (losses) gains (a) (3 ) 1,103 Other income 44 94 Transaction expenses (7,756 ) — Total other items $ (7,715 ) $ 1,197 Total Corporate and Investments $ (39,928 ) $ 20,141 (a) These items exclude the components which are included in the Asset Management segment income (loss) and amounts which are consolidated from VIEs. The following tables reconcile the results of our reportable segments and “Corporate & Investments” function to the Consolidated results of the Company for the years indicated: Three Months Ended March 31, 2018 Reinsurance Segment Insurance Segment Asset Management Segment and Consolidated VIEs Corporate & Investments Eliminations Total Underwriting revenues Gross premiums written $ 765,573 $ 785,795 $ 286,625 $ — $ (5,537 ) $ 1,832,456 Reinsurance premiums ceded (190,194 ) (191,637 ) — — 5,537 (376,294 ) Net premiums written 575,379 594,158 286,625 — — 1,456,162 Change in unearned premiums (350,627 ) (294,620 ) (191,973 ) — — (837,220 ) Net premiums earned 224,752 299,538 94,652 — — 618,942 Other insurance related income 2 2,170 28,080 — (4,756 ) 25,496 Total underwriting revenues 224,754 301,708 122,732 — (4,756 ) 644,438 Underwriting deductions Losses and loss expenses 103,473 183,389 34,683 — — 321,545 Policy acquisition costs 48,340 60,057 8,059 — — 116,456 General and administrative expenses 28,915 68,050 10,208 12,309 (4,756 ) 114,726 Share compensation expenses 2,663 2,989 41 4,036 — 9,729 Total underwriting deductions 183,391 314,485 52,991 16,345 (4,756 ) 562,456 Underwriting income (loss) $ 41,363 $ (12,777 ) $ 69,741 $ (16,345 ) $ — $ 81,982 Net investment return (a) — — 12,735 (2,776 ) — 9,959 Other items (b) — — 362 (20,807 ) — (20,445 ) (Income) attributable to AlphaCat investors — — (10,862 ) — — (10,862 ) Net (income) attributable to noncontrolling interests — — (64,712 ) — — (64,712 ) Net income (loss) available (attributable) to Validus common shareholders $ 41,363 $ (12,777 ) $ 7,264 $ (39,928 ) $ — $ (4,078 ) (a) Net investment return includes net investment income, net realized and change in net unrealized gains (losses) on investments and income (loss) from investment affiliates. (b) 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). Three Months Ended March 31, 2017 Reinsurance Segment Insurance Segment Asset Management Segment and Consolidated VIEs Corporate & Investments Eliminations Total Underwriting revenues Gross premiums written $ 643,141 $ 382,790 $ 164,926 $ — $ — $ 1,190,857 Reinsurance premiums ceded (114,446 ) (79,000 ) (6,660 ) — — (200,106 ) Net premiums written 528,695 303,790 158,266 — — 990,751 Change in unearned premiums (297,040 ) (24,696 ) (93,639 ) — — (415,375 ) Net premiums earned 231,655 279,094 64,627 — — 575,376 Other insurance related income 2 996 5,161 — (4,923 ) 1,236 Total underwriting revenues 231,657 280,090 69,788 — (4,923 ) 576,612 Underwriting deductions Losses and loss expenses 80,881 186,610 2,094 — — 269,585 Policy acquisition costs 43,535 61,192 6,901 — — 111,628 General and administrative expenses 19,969 45,276 9,641 17,961 (4,923 ) 87,924 Share compensation expenses 2,623 3,373 82 3,413 — 9,491 Total underwriting deductions 147,008 296,451 18,718 21,374 (4,923 ) 478,628 Underwriting income (loss) $ 84,649 $ (16,361 ) $ 51,070 $ (21,374 ) $ — $ 97,984 Net investment return (a) — — 4,749 52,837 — 57,586 Other items (b) — — 388 (11,322 ) — (10,934 ) (Income) attributable to AlphaCat investors — — (7,503 ) — — (7,503 ) Net (income) attributable to noncontrolling interests — — (42,572 ) — — (42,572 ) Net income (loss) available (attributable) to Validus common shareholders $ 84,649 $ (16,361 ) $ 6,132 $ 20,141 $ — $ 94,561 (a) Net investment return includes net investment income, net realized and change in net unrealized gains (losses) on investments and income (loss) from investment affiliates. (b) 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).
Gross premiums written allocated to the territory of coverage exposure	The Company’s exposures are generally diversified across geographic zones. The following tables set forth the gross premiums written allocated to the territory of coverage exposure for the years indicated: Gross Premiums Written Three Months Ended March 31, 2018 Reinsurance Segment Insurance Segment Asset Management Segment Eliminations Total % United States $ 200,174 $ 560,722 $ 31,023 $ (1,525 ) $ 790,394 43.1 % Worldwide excluding United States (a) 39,325 52,232 2,879 — 94,436 5.2 % Australia and New Zealand 1,136 8,177 — — 9,313 0.5 % Europe 37,982 5,560 338 — 43,880 2.4 % Latin America and Caribbean 6,539 18,445 — — 24,984 1.4 % Japan 2,100 916 431 — 3,447 0.2 % Canada 3,735 933 — — 4,668 0.3 % Rest of the world (b) 18,298 27,220 — — 45,518 2.5 % Sub-total, non United States 109,115 113,483 3,648 — 226,246 12.3 % Worldwide including United States (a) 118,809 26,655 248,114 (4,012 ) 389,566 21.3 % Other locations non-specific (c) 337,475 84,935 3,840 — 426,250 23.3 % Total $ 765,573 $ 785,795 $ 286,625 $ (5,537 ) $ 1,832,456 100.0 % Gross Premiums Written Three Months Ended March 31, 2017 Reinsurance Segment Insurance Segment Asset Management Segment Eliminations Total % United States $ 223,928 $ 190,188 $ 28,203 $ — $ 442,319 37.1 % Worldwide excluding United States (a) 35,208 32,538 7,035 — 74,781 6.3 % Australia and New Zealand 789 3,174 — — 3,963 0.3 % Europe 31,945 8,681 466 — 41,092 3.5 % Latin America and Caribbean 9,960 20,687 — — 30,647 2.6 % Japan 1,951 1,005 1,193 — 4,149 0.3 % Canada 2,358 449 — — 2,807 0.2 % Rest of the world (b) 15,103 20,392 — — 35,495 3.0 % Sub-total, non United States 97,314 86,926 8,694 — 192,934 16.2 % Worldwide including United States (a) 95,801 27,187 123,309 — 246,297 20.7 % Other locations non-specific (c) 226,098 78,489 4,720 — 309,307 26.0 % Total $ 643,141 $ 382,790 $ 164,926 $ — $ 1,190,857 100.0 % (a) Represents risks in two or more geographic zones. (b) Represents risks in one geographic zone. (c) The other locations non-specific category refers to business for which an analysis of exposure by geographic zone is not applicable since these exposures can span multiple geographic areas and, in some instances, are not fixed locations.

Business combinations (Narrativ

Business combinations (Narrative) (Details) $ / shares in Units, $ in Thousands	May 01, 2017USD ($)StatesAgent	Jan. 21, 2018$ / shares
Crop Risk Services
Business Acquisition [Line Items]
Number of agents | Agent	1,170
Number of states | States	36
Total purchase price | $	$ 185,576
American International Group, Inc.
Business Acquisition [Line Items]
Share price		$ 68
Merger agreement, maximum permitted dividend per share		$ 0.38

Investments (Amortized cost or

Investments (Amortized cost or cost and fair value of investments) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		$ 5,874,140	$ 5,876,261
Short-term investments, at amortized cost or cost		3,638,995	3,381,714
Other investments, at amortized cost or cost		331,950	330,416
Investments in investment affiliates, at cost		75,302	61,944
Total investments		9,920,387	9,650,335
Fixed maturities, at fair value		5,803,022	5,858,348
Short-term investments, at fair value		3,638,940	3,381,757
Other investments, at fair value		357,246	355,218
Investments in investment affiliates, at fair value		113,471	100,137
Total investments		9,912,679	9,695,460
Managed investments
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		5,653,620	5,644,929
Short-term investments, at amortized cost or cost		188,306	229,968
Other investments, at amortized cost or cost		331,950	330,416
Total investments		6,249,178	6,267,257
Fixed maturities, at fair value		5,583,095	5,628,654
Short-term investments, at fair value		188,251	230,011
Other investments, at fair value		357,246	355,218
Total investments		6,242,063	6,314,020
Managed investments | U.S. government and government agency
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		598,080	733,510
Fixed maturities, at fair value		589,161	727,397
Managed investments | Non-U.S. government and government agency
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		318,542	310,845
Fixed maturities, at fair value		318,345	312,239
Managed investments | U.S. states, municipalities and political subdivisions
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		186,551	201,347
Fixed maturities, at fair value		184,964	201,303
Managed investments | Agency residential mortgage-backed securities
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		992,087	984,387
Fixed maturities, at fair value		968,258	978,049
Managed investments | Non-agency residential mortgage-backed securities
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		43,522	40,264
Fixed maturities, at fair value		43,487	40,373
Managed investments | U.S. corporate
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		1,553,311	1,531,498
Fixed maturities, at fair value		1,534,805	1,533,395
Managed investments | Non-U.S. corporate
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		417,264	420,522
Fixed maturities, at fair value		415,156	422,249
Managed investments | Bank loans
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		475,154	450,320
Fixed maturities, at fair value		468,815	442,951
Managed investments | Asset-backed securities
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		744,051	657,234
Fixed maturities, at fair value		741,712	658,303
Managed investments | Commercial mortgage-backed securities
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		325,058	315,002
Fixed maturities, at fair value		318,392	312,395
Managed investments | Hedge funds
Amortized cost (or cost) and estimated fair value of investments
Other investments, at amortized cost or cost		6,954	6,954
Other investments, at fair value		15,758	15,774
Managed investments | Private equity investments
Amortized cost (or cost) and estimated fair value of investments
Other investments, at amortized cost or cost		64,424	63,684
Other investments, at fair value		79,774	78,407
Managed investments | Fixed income investment funds
Amortized cost (or cost) and estimated fair value of investments
Other investments, at amortized cost or cost		199,802	203,167
Other investments, at fair value		200,944	204,426
Managed investments | Overseas deposits
Amortized cost (or cost) and estimated fair value of investments
Other investments, at amortized cost or cost		60,770	56,611
Other investments, at fair value		60,770	56,611
Non-managed investments
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		220,520	231,332
Short-term investments, at amortized cost or cost		3,450,689	3,151,746
Total investments		3,671,209	3,383,078
Fixed maturities, at fair value		219,927	229,694
Short-term investments, at fair value		3,450,689	3,151,746
Total investments		3,670,616	3,381,440
Non-managed investments | Catastrophe bonds
Amortized cost (or cost) and estimated fair value of investments
Fixed maturities, at amortized cost or cost		220,520	231,332
Fixed maturities, at fair value		219,927	229,694
Investment affiliate
Amortized cost (or cost) and estimated fair value of investments
Investments in investment affiliates, at cost	[1]	75,302	61,944
Investments in investment affiliates, at fair value		$ 113,471	$ 100,137	$ 94,697	$ 100,431
[1]	The Company’s investments in investment affiliates have been treated as equity method investments with the corresponding gains and losses recorded in income as “Income from investment affiliates.”

Investments (Fixed maturities b

Investments (Fixed maturities by investment rating) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fixed Maturities
Fair value	$ 5,803,022	$ 5,858,348
Percentage of total	100.00%	100.00%
Managed investments
Fixed Maturities
Fair value	$ 5,583,095	$ 5,628,654
Percentage of total	96.20%	96.10%
Managed investments | Total investment grade fixed maturities
Fixed Maturities
Fair value	$ 5,058,115	$ 5,123,658
Percentage of total	87.20%	87.50%
Managed investments | Total investment grade fixed maturities | AAA
Fixed Maturities
Fair value	$ 2,648,321	$ 2,715,074
Percentage of total	45.70%	46.40%
Managed investments | Total investment grade fixed maturities | AA
Fixed Maturities
Fair value	$ 419,695	$ 442,397
Percentage of total	7.20%	7.60%
Managed investments | Total investment grade fixed maturities | A rating
Fixed Maturities
Fair value	$ 1,159,233	$ 1,137,795
Percentage of total	20.00%	19.40%
Managed investments | Total investment grade fixed maturities | BBB
Fixed Maturities
Fair value	$ 830,866	$ 828,392
Percentage of total	14.30%	14.10%
Managed investments | Total non-investment grade fixed maturities
Fixed Maturities
Fair value	$ 524,980	$ 504,996
Percentage of total	9.00%	8.60%
Managed investments | Total non-investment grade fixed maturities | BB
Fixed Maturities
Fair value	$ 170,818	$ 168,967
Percentage of total	2.90%	2.90%
Managed investments | Total non-investment grade fixed maturities | B
Fixed Maturities
Fair value	$ 240,099	$ 237,131
Percentage of total	4.10%	4.00%
Managed investments | Total non-investment grade fixed maturities | CCC
Fixed Maturities
Fair value	$ 21,783	$ 18,217
Percentage of total	0.40%	0.30%
Managed investments | Total non-investment grade fixed maturities | NR
Fixed Maturities
Fair value	$ 92,280	$ 80,681
Percentage of total	1.60%	1.40%
Non-managed investments
Fixed Maturities
Fair value	$ 219,927	$ 229,694
Percentage of total	3.80%	3.90%
Non-managed investments | Total non-investment grade fixed maturities
Fixed Maturities
Fair value	$ 219,927	$ 229,694
Percentage of total	3.80%	3.90%
Non-managed investments | Total non-investment grade fixed maturities | BB
Fixed Maturities
Fair value	$ 21,607	$ 22,110
Percentage of total	0.40%	0.30%
Non-managed investments | Total non-investment grade fixed maturities | B
Fixed Maturities
Fair value	$ 2,379	$ 3,265
Percentage of total	0.00%	0.10%
Non-managed investments | Total non-investment grade fixed maturities | NR
Fixed Maturities
Fair value	$ 195,941	$ 204,319
Percentage of total	3.40%	3.50%

Investments (Maturity profile o

Investments (Maturity profile of fixed maturity investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Maturity profile
Amortized cost	$ 5,874,140	$ 5,876,261
Fair value	5,803,022	5,858,348
Managed investments
Maturity profile
Amortized cost	5,653,620	5,644,929
Fair value	5,583,095	5,628,654
Managed investments | Asset backed and mortgaged backed securities
Maturity profile
Amortized cost	2,104,718	1,996,887
Fair value	2,071,849	1,989,120
Managed investments | Fixed maturities trading securities allocated to contractual maturity
Maturity profile
Amortized cost	3,548,902	3,648,042
Fair value	3,511,246	3,639,534
Managed investments | Fixed maturities trading securities allocated to contractual maturity | Due in one year or less
Maturity profile
Amortized cost	346,118	343,360
Fair value	344,749	343,541
Managed investments | Fixed maturities trading securities allocated to contractual maturity | Due after one year through five years
Maturity profile
Amortized cost	2,453,565	2,527,018
Fair value	2,424,185	2,513,620
Managed investments | Fixed maturities trading securities allocated to contractual maturity | Due after five years through ten years
Maturity profile
Amortized cost	560,679	577,347
Fair value	554,188	577,109
Managed investments | Fixed maturities trading securities allocated to contractual maturity | Due after ten years
Maturity profile
Amortized cost	188,540	200,317
Fair value	188,124	205,264
Non-managed investments
Maturity profile
Amortized cost	220,520	231,332
Fair value	219,927	229,694
Non-managed investments | Due in one year or less
Maturity profile
Amortized cost	67,370	88,797
Fair value	67,926	88,367
Non-managed investments | Due after one year through five years
Maturity profile
Amortized cost	147,400	140,035
Fair value	146,238	138,844
Non-managed investments | Due after five years through ten years
Maturity profile
Amortized cost	5,750	2,500
Fair value	$ 5,763	$ 2,483

Investments (Other investments)

Investments (Other investments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Other investments, at fair value	$ 357,246	$ 355,218
Managed investments
Investment [Line Items]
Other investments, at fair value	357,246	355,218
Managed investments | Hedge funds
Investment [Line Items]
Other investments, at fair value	15,758	15,774
Managed investments | Private equity investments
Investment [Line Items]
Other investments, at fair value	79,774	78,407
Managed investments | Fixed income investment funds
Investment [Line Items]
Other investments, at fair value	200,944	204,426
Managed investments | Overseas deposits
Investment [Line Items]
Other investments, at fair value	60,770	56,611
Managed investments | Subject to redemption restriction
Investment [Line Items]
Other investments, at fair value	357,246	351,324
Managed investments | Subject to redemption restriction | Hedge funds
Investment [Line Items]
Other investments, at fair value	15,758	15,774
Managed investments | Subject to redemption restriction | Private equity investments
Investment [Line Items]
Other investments, at fair value	79,774	78,407
Managed investments | Subject to redemption restriction | Fixed income investment funds
Investment [Line Items]
Other investments, at fair value	200,944	200,532
Managed investments | Subject to redemption restriction | Overseas deposits
Investment [Line Items]
Other investments, at fair value	60,770	56,611
Managed investments | Not subject to redemption restriction
Investment [Line Items]
Other investments, at fair value	0	3,894
Managed investments | Not subject to redemption restriction | Hedge funds
Investment [Line Items]
Other investments, at fair value	0	0
Managed investments | Not subject to redemption restriction | Private equity investments
Investment [Line Items]
Other investments, at fair value	0	0
Managed investments | Not subject to redemption restriction | Fixed income investment funds
Investment [Line Items]
Other investments, at fair value	$ 0	$ 3,894
Redemption frequency		Daily	[1]
Managed investments | Not subject to redemption restriction | Fixed income investment funds | Minimum
Investment [Line Items]
Redemption notice period		1 day
Managed investments | Not subject to redemption restriction | Fixed income investment funds | Maximum
Investment [Line Items]
Redemption notice period		2 days
Managed investments | Not subject to redemption restriction | Overseas deposits
Investment [Line Items]
Other investments, at fair value	$ 0	$ 0
Recurring | Managed investments
Investment [Line Items]
Other investments, at fair value	357,246	355,218
Recurring | Managed investments | Hedge funds
Investment [Line Items]
Other investments, at fair value	15,758	15,774
Recurring | Managed investments | Private equity investments
Investment [Line Items]
Other investments, at fair value	79,774	78,407
Recurring | Managed investments | Fixed income investment funds
Investment [Line Items]
Other investments, at fair value	200,944	204,426
Recurring | Managed investments | Overseas deposits
Investment [Line Items]
Other investments, at fair value	$ 60,770	$ 56,611
[1]	The redemption frequency and notice periods only apply to investments without redemption restrictions.

Investments (Investment affilia

Investments (Investment affiliate rollforward) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Equity Method Investments [Line Items]
Investments in affiliates, beginning of period	$ 100,137
Income from investment affiliates	13,068	$ 5,188
Investments in affiliates, end of period	113,471
Investment affiliate
Schedule of Equity Method Investments [Line Items]
Investments in affiliates, beginning of period	100,137	100,431
Net capital (distributions) contributions	266	(10,922)
Income from investment affiliates	13,068	5,188
Investments in affiliates, end of period	$ 113,471	$ 94,697

Investments (Investment affil46

Investments (Investment affiliate details) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Remaining commitment		$ 222,806	$ 234,775
Investments in investment affiliates, at cost		75,302	61,944
Investments in affiliates		113,471	100,137
Investment affiliate
Schedule of Equity Method Investments [Line Items]
Remaining commitment		107,386	125,996
Investments in investment affiliates, at cost	[1]	75,302	61,944
Investments in affiliates		113,471	100,137	$ 94,697	$ 100,431
Investment affiliate | Aquiline Financial Services Fund II LP
Schedule of Equity Method Investments [Line Items]
Investments in investment affiliates, at cost		$ 33,008	$ 33,349
Voting ownership %		0.00%	0.00%
Equity ownership %		8.10%	8.10%
Investments in affiliates		$ 49,208	$ 51,914
Investment affiliate | Aquiline Financial Services Fund III LP
Schedule of Equity Method Investments [Line Items]
Investments in investment affiliates, at cost		$ 24,737	$ 24,737
Voting ownership %		0.00%	0.00%
Equity ownership %		9.00%	9.00%
Investments in affiliates		$ 47,114	$ 44,733
Investment affiliate | Aquiline Tech
Schedule of Equity Method Investments [Line Items]
Investments in investment affiliates, at cost		$ 3,858	$ 3,858
Voting ownership %		0.00%	0.00%
Equity ownership %		10.60%	10.60%
Investments in affiliates		$ 3,450	$ 3,490
Investment affiliate | Aquiline Armour
Schedule of Equity Method Investments [Line Items]
Investments in investment affiliates, at cost		$ 13,699
Voting ownership %		0.00%
Equity ownership %		15.20%
Investments in affiliates		$ 13,699
[1]	The Company’s investments in investment affiliates have been treated as equity method investments with the corresponding gains and losses recorded in income as “Income from investment affiliates.”

Investments (Components of net

Investments (Components of net investment income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net investment income
Net investment income	$ 52,072	$ 40,214
Managed investments
Net investment income
Total gross investment income	43,134	39,164
Investment expenses	(3,343)	(2,972)
Net investment income	39,791	36,192
Managed investments | Fixed maturities and short term investments
Net investment income
Total gross investment income	37,769	31,671
Managed investments | Other investments
Net investment income
Total gross investment income	4,223	6,870
Managed investments | Restricted cash, cash and cash equivalents
Net investment income
Total gross investment income	1,139	610
Managed investments | Securities lending income
Net investment income
Total gross investment income	3	13
Non-managed investments
Net investment income
Net investment income	12,281	4,022
Non-managed investments | Fixed maturities and short term investments
Net investment income
Total gross investment income	4,148	3,060
Non-managed investments | Restricted cash, cash and cash equivalents
Net investment income
Total gross investment income	$ 8,133	$ 962

Investments (Realized and unrea

Investments (Realized and unrealized gains) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Net realized gains (losses) on investments	$ 2,200	$ (1,164)
Change in net unrealized (losses) gains on investments	(57,381)	13,348
Total net realized and change in net unrealized gains (losses) on investments	(55,181)	12,184
Managed investments
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Gross realized gains	6,830	2,690
Gross realized (losses)	(5,688)	(5,582)
Net realized gains (losses) on investments	1,142	(2,892)
Change in net unrealized (losses) gains on investments	(56,777)	14,349
Total net realized and change in net unrealized gains (losses) on investments	(55,635)	11,457
Non-managed investments
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Gross realized gains	1,235	1,728
Gross realized (losses)	(177)	0
Net realized gains (losses) on investments	1,058	1,728
Change in net unrealized (losses) gains on investments	(604)	(1,001)
Total net realized and change in net unrealized gains (losses) on investments	$ 454	$ 727

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value	$ 357,246	$ 355,218
Cash, cash equivalents, restricted cash and investments pledged as collateral	6,120,705	5,853,744
Investments held in trust	6,092,111	5,789,081
Investments and cash pledged as collateral	540,239	576,864
Managed investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value	357,246	355,218
Managed investments | Subject to redemption restriction
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value	$ 357,246	351,324
Managed investments | Minimum | Subject to redemption restriction
Schedule of Trading Securities and Other Trading Assets [Line Items]
Redemption restriction period	5 years
Managed investments | Maximum | Subject to redemption restriction
Schedule of Trading Securities and Other Trading Assets [Line Items]
Redemption restriction period	10 years
Rated or consist of externally rated securities | Managed investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value	$ 193,053	186,734
Not externally rated | Managed investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value	$ 164,193	$ 168,484

Fair value measurements (Fair v

Fair value measurements (Fair value hierarchy) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		$ 5,803,022	$ 5,858,348
Short-term investments, at fair value		3,638,940	3,381,757
Other investments, at fair value		357,246	355,218
Investments in affiliates		113,471	100,137
Total investments		9,912,679	9,695,460
Managed investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		5,583,095	5,628,654
Short-term investments, at fair value		188,251	230,011
Other investments, at fair value		357,246	355,218
Total investments		6,242,063	6,314,020
Managed investments | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		589,161	727,397
Managed investments | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		318,345	312,239
Managed investments | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		184,964	201,303
Managed investments | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		968,258	978,049
Managed investments | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		43,487	40,373
Managed investments | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		1,534,805	1,533,395
Managed investments | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		415,156	422,249
Managed investments | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		468,815	442,951
Managed investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		741,712	658,303
Managed investments | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		318,392	312,395
Managed investments | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		15,758	15,774
Managed investments | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		79,774	78,407
Managed investments | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		200,944	204,426
Managed investments | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		60,770	56,611
Non-managed investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		219,927	229,694
Short-term investments, at fair value		3,450,689	3,151,746
Total investments		3,670,616	3,381,440
Non-managed investments | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		219,927	229,694
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments		9,912,679	9,695,460
Recurring | Fair value based on NAV practical expedient
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	[1]	329,855	324,463
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments		3,626,215	3,349,800
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments		5,430,189	5,512,317
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments		412,949	408,743
Recurring | Managed investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		5,583,095	5,628,654
Short-term investments, at fair value		188,251	230,011
Other investments, at fair value		357,246	355,218
Total investments		6,242,063	6,314,020
Recurring | Managed investments | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		589,161	727,397
Recurring | Managed investments | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		318,345	312,239
Recurring | Managed investments | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		184,964	201,303
Recurring | Managed investments | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		968,258	978,049
Recurring | Managed investments | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		43,487	40,373
Recurring | Managed investments | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		1,534,805	1,533,395
Recurring | Managed investments | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		415,156	422,249
Recurring | Managed investments | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		468,815	442,951
Recurring | Managed investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		741,712	658,303
Recurring | Managed investments | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		318,392	312,395
Recurring | Managed investments | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		15,758	15,774
Recurring | Managed investments | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		79,774	78,407
Recurring | Managed investments | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		200,944	204,426
Recurring | Managed investments | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		60,770	56,611
Recurring | Managed investments | Fair value based on NAV practical expedient
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Short-term investments, at fair value	[1]	0	0
Other investments, at fair value	[1]	329,855	324,463
Total investments	[1]	329,855	324,463
Recurring | Managed investments | Fair value based on NAV practical expedient | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Managed investments | Fair value based on NAV practical expedient | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	[1]	15,758	15,774
Recurring | Managed investments | Fair value based on NAV practical expedient | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	[1]	79,774	78,407
Recurring | Managed investments | Fair value based on NAV practical expedient | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	[1]	173,553	173,671
Recurring | Managed investments | Fair value based on NAV practical expedient | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	[1]	60,770	56,611
Recurring | Managed investments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Short-term investments, at fair value		175,526	198,054
Other investments, at fair value		0	0
Total investments		175,526	198,054
Recurring | Managed investments | Level 1 | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 1 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 1 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 1 | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 1 | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		5,253,776	5,314,776
Short-term investments, at fair value		12,725	31,957
Other investments, at fair value		9,458	13,351
Total investments		5,275,959	5,360,084
Recurring | Managed investments | Level 2 | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		589,161	727,397
Recurring | Managed investments | Level 2 | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		318,345	312,239
Recurring | Managed investments | Level 2 | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		184,964	201,303
Recurring | Managed investments | Level 2 | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		968,258	978,049
Recurring | Managed investments | Level 2 | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		43,487	40,373
Recurring | Managed investments | Level 2 | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		1,534,805	1,533,395
Recurring | Managed investments | Level 2 | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		415,156	422,249
Recurring | Managed investments | Level 2 | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		241,312	232,886
Recurring | Managed investments | Level 2 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		639,896	554,490
Recurring | Managed investments | Level 2 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		318,392	312,395
Recurring | Managed investments | Level 2 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 2 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 2 | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		9,458	13,351
Recurring | Managed investments | Level 2 | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		329,319	313,878
Short-term investments, at fair value		0	0
Other investments, at fair value		17,933	17,404
Total investments		347,252	331,282
Recurring | Managed investments | Level 3 | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		227,503	210,065
Recurring | Managed investments | Level 3 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		101,816	103,813
Recurring | Managed investments | Level 3 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Managed investments | Level 3 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 3 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Managed investments | Level 3 | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		17,933	17,404
Recurring | Managed investments | Level 3 | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value		0	0
Recurring | Non-managed investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value		3,450,689	3,151,746
Total investments		3,670,616	3,381,440
Recurring | Non-managed investments | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		219,927	229,694
Recurring | Non-managed investments | Fair value based on NAV practical expedient
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value	[1]	0	0
Total investments	[1]	0	0
Recurring | Non-managed investments | Fair value based on NAV practical expedient | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	[1]	0	0
Recurring | Non-managed investments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value		3,450,689	3,151,746
Total investments		3,450,689	3,151,746
Recurring | Non-managed investments | Level 1 | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		0	0
Recurring | Non-managed investments | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value		0	0
Total investments		154,230	152,233
Recurring | Non-managed investments | Level 2 | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		154,230	152,233
Recurring | Non-managed investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value		0	0
Total investments		65,697	77,461
Recurring | Non-managed investments | Level 3 | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		$ 65,697	$ 77,461
[1]	In accordance with ASC Topic 820 “Fair Value Measurements,” investments measured at fair value using the net asset value (“NAV”) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

Fair value measurements (Level

Fair value measurements (Level 3 rollforward) (Details) - Recurring - Level 3 - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reconciliation of beginning and ending balances for all investments measured at fair value on recurring basis
Level 3 investments - beginning of period	$ 408,743	$ 330,970
Purchases	50,139	84,267
Sales	(70)
Settlements	(45,326)	(71,498)
Realized gains	1,235	3,134
Change in net unrealized (losses) gains	(1,772)	(1,061)
Level 3 investments - end of period	412,949	345,812
Bank loan portfolio
Reconciliation of beginning and ending balances for all investments measured at fair value on recurring basis
Level 3 investments - beginning of period	210,065	246,496
Purchases	30,785	23,176
Sales	0
Settlements	(13,842)	(33,110)
Realized gains	0	0
Change in net unrealized (losses) gains	495	132
Level 3 investments - end of period	227,503	236,694
Catastrophe bonds
Reconciliation of beginning and ending balances for all investments measured at fair value on recurring basis
Level 3 investments - beginning of period	77,461	48,375
Purchases	18,825	61,091
Sales	0
Settlements	(31,484)	(38,780)
Realized gains	1,235	3,134
Change in net unrealized (losses) gains	(340)	(1,144)
Level 3 investments - end of period	65,697	72,676
Fixed income investment funds
Reconciliation of beginning and ending balances for all investments measured at fair value on recurring basis
Level 3 investments - beginning of period	17,404	12,168
Purchases	529	0
Sales	0
Settlements	0	392
Realized gains	0	0
Change in net unrealized (losses) gains	0	0
Level 3 investments - end of period	17,933	12,560
Asset-backed securities
Reconciliation of beginning and ending balances for all investments measured at fair value on recurring basis
Level 3 investments - beginning of period	103,813	23,931
Purchases	0	0
Sales	(70)
Settlements	0	0
Realized gains	0	0
Change in net unrealized (losses) gains	(1,927)	(49)
Level 3 investments - end of period	$ 101,816	$ 23,882

Fair value measurements (Narrat

Fair value measurements (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Trading Securities	$ 9,912,679	$ 9,695,460
Managed investments
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Trading Securities	6,242,063	6,314,020
Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Trading Securities	$ 9,912,679	9,695,460
Recurring | Hedge funds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment Time Lag Reporting	3 months
Recurring | Minimum | Private equity investments
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment Time Lag Reporting	3 months
Recurring | Minimum | Fixed income investment funds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment Time Lag Reporting	1 month
Recurring | Maximum | Private equity investments
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment Time Lag Reporting	6 months
Recurring | Maximum | Fixed income investment funds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment Time Lag Reporting	3 months
Recurring | Managed investments
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Trading Securities	$ 6,242,063	6,314,020
Recurring | Level 3
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Trading Securities	412,949	408,743
Recurring | Level 3 | Fixed income investment funds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Transfers Into Level 3	0
Recurring | Level 3 | Managed investments
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Trading Securities	$ 347,252	$ 331,282
Ratio of Level 3 investments to total investments (percent)	5.60%	5.20%

Variable interest entities (Not

Variable interest entities (Notes payable to AlphaCat investors) (Details) - Variable interest entities, primary beneficiary - AlphaCat ILS funds - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Variable Interest Entity [Line Items]
Notes payable to AlphaCat investors, beginning of period	$ 1,108,364	$ 278,202
Issuance of notes payable to AlphaCat investors	686,512	377,330
Redemption of notes payable to AlphaCat investors	(530,546)	(208,956)
Foreign exchange losses	3,864
Notes payable to AlphaCat investors, end of period	1,268,194	446,576
Variable Funding Notes
Variable Interest Entity [Line Items]
Notes payable to AlphaCat investors, beginning of period	936,164	278,202
Issuance of notes payable to AlphaCat investors	506,540	274,010
Redemption of notes payable to AlphaCat investors	(530,546)	(208,956)
Foreign exchange losses	3,864
Notes payable to AlphaCat investors, end of period	916,022	343,256
Structured Notes
Variable Interest Entity [Line Items]
Notes payable to AlphaCat investors, beginning of period	172,200	0
Issuance of notes payable to AlphaCat investors	179,972	103,320
Redemption of notes payable to AlphaCat investors	0	0
Foreign exchange losses	0
Notes payable to AlphaCat investors, end of period	$ 352,172	$ 103,320

Variable interest entities (Ass

Variable interest entities (Assets and liabilities of consolidated VIEs) (Details) - Variable interest entities, primary beneficiary - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2016
AlphaCat sidecars
Variable Interest Entity [Line Items]
Total assets	$ 25,952	$ 25,975
Total liabilities	3,071	3,267
AlphaCat ILS funds - Lower Risk
Variable Interest Entity [Line Items]
Total assets	1,046,458	1,107,503
Total liabilities	11,156	259,630
AlphaCat ILS funds - Higher Risk
Variable Interest Entity [Line Items]
Total assets	1,431,945	1,310,071
Total liabilities	676,225	912,341
AlphaCat Re and AlphaCat Master Fund
Variable Interest Entity [Line Items]
Total assets	3,878,359	3,398,082
Total liabilities	3,878,189	3,397,912
BetaCat ILS funds
Variable Interest Entity [Line Items]
Total assets	104,857	77,221
Total liabilities	$ 2,207	$ 261

Variable interest entities (Nar

Variable interest entities (Narrative) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)funds	Mar. 31, 2017USD ($)	Dec. 31, 2017
Variable Interest Entity [Line Items]
Risk profile percentage	7.00%
Variable funding notes, typical minimum duration	12 months
(Income) attributable to AlphaCat investors	$ 10,862	$ 7,503
Accounts payable and accrued expenses
Variable Interest Entity [Line Items]
(Income) attributable to AlphaCat investors	43,442	18,054
AlphaCat ILS funds | Variable interest entities, primary beneficiary
Variable Interest Entity [Line Items]
Variable Interest Entity Redemption Of Notes Payable To AlphaCat Investors	$ 530,546	$ 208,956
ILS fund issuing structured notes
Variable Interest Entity [Line Items]
Structured notes interest rate percentage	6.50%		7.00%
BetaCat ILS funds
Variable Interest Entity [Line Items]
Number of BetaCat ILS funds | funds	3
BetaCat ILS funds | Variable interest entities, primary beneficiary
Variable Interest Entity [Line Items]
Number of BetaCat ILS funds | funds	2

Noncontrolling interest (Detail

Noncontrolling interest (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Balance, beginning of period	$ 1,020,812	$ 1,693,978
Issuance of shares	666,600	258,679
Income attributable to noncontrolling interests	64,712	42,572
Redemption of shares / Distributions	5,343	(7,002)
Balance, end of period	1,757,467	1,988,227
Redeemable noncontrolling interest
Noncontrolling Interest [Line Items]
Balance, beginning of period	1,004,094	1,528,001
Issuance of shares	385,300	103,699
Income attributable to noncontrolling interests	28,373	25,930
Redemption of shares	5,343	0
Balance, end of period	1,423,110	1,657,630
Balances payable to noncontrolling interests	0		$ 180,104
Noncontrolling interest
Noncontrolling Interest [Line Items]
Balance, beginning of period	16,718	165,977
Issuance of shares	281,300	154,980
Income attributable to noncontrolling interests	36,339	16,642
Distributions	0	(7,002)
Balance, end of period	$ 334,357	$ 330,597

Derivative instruments (Amount

Derivative instruments (Amount and balance sheet location) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Not designated as hedging instruments | Foreign currency forward contracts
Summary of derivatives
Net Notional Exposure	$ 239,398	$ 283,765
Not designated as hedging instruments | Foreign currency forward contracts | Other assets
Summary of derivatives
Fair value, derivative assets	1,945	1,147
Not designated as hedging instruments | Foreign currency forward contracts | Accounts payable and accrued expenses
Summary of derivatives
Fair value, derivative liabilities	433	906
Not designated as hedging instruments | Interest rate swap contracts
Summary of derivatives
Net Notional Exposure	200,000	200,000
Not designated as hedging instruments | Interest rate swap contracts | Other assets
Summary of derivatives
Fair value, derivative assets	7,357	1,589
Not designated as hedging instruments | Interest rate swap contracts | Accounts payable and accrued expenses
Summary of derivatives
Fair value, derivative liabilities	0	0
Not designated as hedging instruments | Weather derivative contracts
Summary of derivatives
Net Notional Exposure	4,825	4,825
Not designated as hedging instruments | Weather derivative contracts | Other assets
Summary of derivatives
Fair value, derivative assets	26,958	853
Not designated as hedging instruments | Weather derivative contracts | Accounts payable and accrued expenses
Summary of derivatives
Fair value, derivative liabilities	0	0
Designated as hedging instruments | Foreign currency forward contracts
Summary of derivatives
Net Notional Exposure	80,373	96,293
Designated as hedging instruments | Foreign currency forward contracts | Other assets
Summary of derivatives
Fair value, derivative assets	4,503	1,891
Designated as hedging instruments | Foreign currency forward contracts | Accounts payable and accrued expenses
Summary of derivatives
Fair value, derivative liabilities	0	0
Designated as hedging instruments | Interest rate swap contracts
Summary of derivatives
Net Notional Exposure	552,263	552,263
Designated as hedging instruments | Interest rate swap contracts | Other assets
Summary of derivatives
Fair value, derivative assets	23,256	9,806
Designated as hedging instruments | Interest rate swap contracts | Accounts payable and accrued expenses
Summary of derivatives
Fair value, derivative liabilities	$ 4,931	$ 18,840

Derivative instruments (Amoun58

Derivative instruments (Amount included in statement of operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Not designated as hedging instruments | Foreign currency forward contracts | Foreign exchange gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in earnings	$ (5,201)	$ 453
Not designated as hedging instruments | Foreign currency forward contracts | Other insurance related income and other income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in earnings	0	(105)
Not designated as hedging instruments | Interest rate swap contracts | Net realized gains on investments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in earnings	5,944	0
Not designated as hedging instruments | Weather derivative contracts | Other insurance related income and other income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in earnings	26,773	0
Designated as hedging instruments | Cash flow hedge | Foreign currency forward contracts | Other comprehensive income
Derivative instruments designated as a cash flow hedge
Amount of effective portion recognized in other comprehensive income	2,920	0
Designated as hedging instruments | Cash flow hedge | Foreign currency forward contracts | General and administrative expense
Derivative instruments designated as a cash flow hedge
Amount of effective portion subsequently reclassified to earnings	(308)	0
Designated as hedging instruments | Cash flow hedge | Interest rate swap contracts | Other comprehensive income
Derivative instruments designated as a cash flow hedge
Amount of effective portion recognized in other comprehensive income	25,843	98
Designated as hedging instruments | Cash flow hedge | Interest rate swap contracts | Finance expenses
Derivative instruments designated as a cash flow hedge
Amount of effective portion subsequently reclassified to earnings	$ 1,343	$ 0

Reserve for losses and loss e59

Reserve for losses and loss expenses (Components of reserves for losses and loss expenses) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Insurance Loss Reserves [Abstract]
Case reserves	$ 1,770,278	$ 1,753,844
IBNR	2,862,351	3,077,546
Reserve for losses and loss expenses	$ 4,632,629	$ 4,831,390	$ 3,052,745	$ 2,995,195

Reserve for losses and loss e60

Reserve for losses and loss expenses (Reserve rollforward) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reserve for paid losses and unpaid loss expenses
Reserve for losses and loss expenses, beginning of period	$ 4,831,390	$ 2,995,195
Loss reserves recoverable, beginning of period	(1,233,997)	(430,421)
Net reserves for losses and loss expenses, beginning of period	3,597,393	2,564,774
Increase (decrease) in net losses and loss expenses incurred in respect of losses occurring in:
Current year	329,115	330,816
Prior years	(7,570)	(61,231)
Total incurred losses and loss expenses	321,545	269,585
Foreign exchange losses (gains)	15,627	12,317
Less net losses and loss expenses paid in respect of losses occurring in:
Current year	(19,735)	(7,698)
Prior years	(262,145)	(238,089)
Total net paid losses	(281,880)	(245,787)
Net reserve for losses and loss expenses, end of period	3,652,685	2,600,889
Loss reserves recoverable, end of period	979,944	451,856
Reserve for losses and loss expenses, end of period	4,632,629	3,052,745
Components of incurred losses and loss expenses
Gross losses and loss expenses	248,781	336,442
Reinsurance recoverable	72,764	(66,857)
Net incurred losses and loss expenses	$ 321,545	$ 269,585

Reserve for losses and loss e61

Reserve for losses and loss expenses (Prior year development) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	$ (7,570)	$ (61,231)
Operating Segments
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(7,570)	(61,231)
Operating Segments | Reinsurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(17,838)	(31,124)
Operating Segments | Insurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(15,548)	(26,689)
Operating Segments | Asset management segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	25,816	(3,418)
Operating Segments | Property Line of Business [Member]
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	24,446	(17,123)
Operating Segments | Property Line of Business [Member] | Reinsurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(4,822)	(4,062)
Operating Segments | Property Line of Business [Member] | Insurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	4,068	(8,666)
Operating Segments | Property Line of Business [Member] | Asset management segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	25,200	(4,395)
Operating Segments | Specialty Short Tail Line of Business [Member]
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(25,036)	(37,534)
Operating Segments | Specialty Short Tail Line of Business [Member] | Reinsurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(13,451)	(26,748)
Operating Segments | Specialty Short Tail Line of Business [Member] | Insurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(12,201)	(11,763)
Operating Segments | Specialty Short Tail Line of Business [Member] | Asset management segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	616	977
Operating Segments | Specialty Other Line of Business [Member]
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(6,980)	(6,574)
Operating Segments | Specialty Other Line of Business [Member] | Reinsurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	435	(314)
Operating Segments | Specialty Other Line of Business [Member] | Insurance segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	(7,415)	(6,260)
Operating Segments | Specialty Other Line of Business [Member] | Asset management segment
Increase (decrease) in net reserves for losses and loss expenses in respect of losses occurring in:
Net (favorable) adverse development on prior years	$ 0	$ 0

Reinsurance (Components of rein

Reinsurance (Components of reinsurance) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Outstanding losses	$ 235,814	$ 275,450
IBNR	744,130	958,547
Total loss reserves recoverable	979,944	1,233,997	$ 451,856	$ 430,421
Paid losses recoverable	59,892	46,873
Total reinsurance balances recoverable	$ 1,039,836	$ 1,280,870

Reinsurance (Ceded credit risk)

Reinsurance (Ceded credit risk) (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Provision for uncollectible reinsurance relating to losses recoverable		$ 8,403	$ 8,848
Reinsurance Recoverable
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 1,039,836	$ 1,280,870
Percentage of total		100.00%	100.00%
Reinsurance Recoverable | A- or better
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 1,029,021	$ 1,270,503
Percentage of total		99.00%	99.20%
Reinsurance Recoverable | Top 10 reinsurers
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 878,685	$ 1,055,445
Percentage of total		84.50%	82.50%
Reinsurance Recoverable | Top 10 reinsurers | Fully collateralized reinsurers | NR
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 407,361	$ 459,339
Percentage of total		39.20%	35.90%
Reinsurance Recoverable | Top 10 reinsurers | Everest Re | A plus
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 128,360	$ 128,206
Percentage of total		12.30%	10.00%
Reinsurance Recoverable | Top 10 reinsurers | Lloyds Syndicates | A plus
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 69,885	$ 74,277
Percentage of total		6.70%	5.80%
Reinsurance Recoverable | Top 10 reinsurers | Swiss Re | AA- rating
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 56,892	$ 65,218
Percentage of total		5.50%	5.10%
Reinsurance Recoverable | Top 10 reinsurers | Munich Re | AA- rating
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 50,097	$ 94,180
Percentage of total		4.80%	7.40%
Reinsurance Recoverable | Top 10 reinsurers | Hannover Re | AA- rating
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 49,501	$ 53,523
Percentage of total		4.80%	4.20%
Reinsurance Recoverable | Top 10 reinsurers | Transatlantic Re | A plus
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 38,446	$ 33,729
Percentage of total		3.70%	2.60%
Reinsurance Recoverable | Top 10 reinsurers | Qatar Insurance Company | A rating
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 30,981	$ 50,160
Percentage of total		3.00%	3.90%
Reinsurance Recoverable | Top 10 reinsurers | Markel | A rating
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 25,893	$ 28,068
Percentage of total		2.50%	2.20%
Reinsurance Recoverable | Top 10 reinsurers | XL Catlin | A plus
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 21,269
Percentage of total		2.00%
Reinsurance Recoverable | Top 10 reinsurers | Federal Crop Insurance Corporation
Ceded Credit Risk [Line Items]
Reinsurance recoverable	[1]		$ 68,745
Percentage of total	[1]		5.40%
Reinsurance Recoverable | Other reinsurers' balances greater than $1 million
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 153,572	$ 218,226
Percentage of total		14.80%	17.00%
Reinsurance Recoverable | Other reinsurers' balances less than $1 million
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 7,579	$ 7,199
Percentage of total		0.70%	0.50%
[1]	The Company participates in a crop reinsurance program sponsored by the U.S. federal government. The Company remains obligated for amounts ceded in the event that its reinsurers or retrocessionaires do not meet their obligations, except for amounts ceded to the U.S. federal government in the Insurance segment agriculture line of business.

Share capital (Preferred stock)

Share capital (Preferred stock) (Details) $ / shares in Units, $ in Thousands	Jun. 12, 2017USD ($)$ / sharesshares	Jun. 13, 2016USD ($)$ / sharesshares	Mar. 31, 2018shares	Dec. 31, 2017shares
Preferred shares - Shareholders' Equity
Preferred shares, shares issued			16,000	16,000
Preferred shares, shares outstanding			16,000	16,000
Series A preferred shares
Preferred shares - Shareholders' Equity
Preferred shares, dividend rate, percentage		5.875%
Preferred shares, shares issued		6,000	6,000	6,000
Preferred shares, shares outstanding			6,000	6,000
Preferred stock, par or stated value per share | $ / shares		$ 0.175
Preferred stock, liquidation preference, per share | $ / shares		$ 25,000
Net proceeds on issuance of preferred shares | $		$ 144,852
Series A depositary share equivalent
Preferred shares - Shareholders' Equity
Preferred shares equivalent depositary shares number		6,000,000
Proportionate interest of preferred shares, per depositary share		0.001
Preferred stock, liquidation preference, per share | $ / shares		$ 25
Series B preferred shares
Preferred shares - Shareholders' Equity
Preferred shares, dividend rate, percentage	5.80%
Preferred shares, shares issued	10,000		10,000	10,000
Preferred shares, shares outstanding			10,000	10,000
Preferred stock, par or stated value per share | $ / shares	$ 0.175
Preferred stock, liquidation preference, per share | $ / shares	$ 25,000
Net proceeds on issuance of preferred shares | $	$ 241,686
Series B depositary share equivalent
Preferred shares - Shareholders' Equity
Preferred shares equivalent depositary shares number	10,000,000
Proportionate interest of preferred shares, per depositary share	0.001
Preferred stock, liquidation preference, per share | $ / shares	$ 25

Share capital (Common stock) (D

Share capital (Common stock) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share Capital (Narrative)
Authorized share capital	571,428,571
Common shares, par value	$ 0.175
Common stock voting rights	one vote per share
Maximum voting percent	9.09%
Share repurchases
Share repurchase program, cumulative shares repurchased	81,035,969
Shares repurchased, cumulative	$ 2,730,975
Remaining share repurchase authorization amount	$ 293,426
Summary of common shares issued and outstanding
Common shares issued, beginning balance	161,994,491	161,279,976
Common shares issued, ending balance	162,003,969	161,285,411
Treasury shares, end of period	(82,674,941)	(82,147,821)
Common shares outstanding, ending balance	79,329,028	79,137,590
Restricted share awards
Summary of common shares issued and outstanding
Vested, net of shares withheld	7,423	3,440
Restricted share units
Summary of common shares issued and outstanding
Vested, net of shares withheld	2,055	1,995

Share capital (Dividends) (Deta

Share capital (Dividends) (Details) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class of Stock [Line Items]
Cash dividends declared per share - common shares	$ 0.38	$ 0.38
Series A depositary share equivalent
Class of Stock [Line Items]
Cash dividends declared per share - preferred shares	0.3671875	$ 0.3671875
Series B depositary share equivalent
Class of Stock [Line Items]
Cash dividends declared per share - preferred shares	$ 0.3625000

Stock plans (Options activity)

Stock plans (Options activity) (Details)	Mar. 31, 2018$ / sharesshares
Options activities:
Options outstanding, beginning balance (in shares) | shares	26,136
Options outstanding, ending balance (in shares) | shares	26,136
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning balance (in dollars per share)	$ 6.78
Weighted average grant date fair value, ending balance (in dollars per share)	6.78
Weighted Average Grant Date Exercise Price
Weighted average grant date exercise price, beginning balance (in dollars per share)	23.48
Weighted average grant date exercise price, ending balance (in dollars per share)	$ 23.48

Stock plans (Other awards activ

Stock plans (Other awards activity) (Details) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Restricted share awards
Activities
Beginning balance (in shares)	2,080,397	2,469,982
Granted (in shares)	1,552	2,082
Vested (in shares)	(8,092)	(4,571)
Forfeited (in shares)	(6,138)	(513)
Ending balance (in shares)	2,067,719	2,466,980
Weighted average grant date fair value
Weighted average grant date fair value, beginning balance (in dollars per share)	$ 43.66	$ 40.89
Weighted average grant date fair value, granted (in dollars per share)	67.64	57.66
Weighted average grant date fair value, vested (in dollars per share)	44.49	37.93
Weighted average grant date fair value, forfeited (in dollars per share)	47.46	48.69
Weighted average grant date fair value, ending balance (in dollars per share)	$ 43.66	$ 40.91
Restricted share units
Activities
Beginning balance (in shares)	109,394	112,808
Vested (in shares)	(2,178)	(2,115)
Issued in lieu of cash dividends (in shares)	886	717
Forfeited (in shares)	(1)	0
Ending balance (in shares)	108,101	111,410
Weighted average grant date fair value
Weighted average grant date fair value, beginning balance (in dollars per share)	$ 42.20	$ 40.95
Weighted average grant date fair value, vested (in dollars per share)	38.24	38.24
Weighted average grant date fair value, issued in lieu of cash dividends (in dollars per share)	42.20	40.95
Weighted average grant date fair value, forfeited (in dollars per share)	38.24	0
Weighted average grant date fair value, ending balance (in dollars per share)	$ 42.28	$ 41.01
Performance shares
Activities
Beginning balance (in shares)	314,068	285,820
Conversion adjustment (in shares)	0	(26,322)
Ending balance (in shares)	314,068	259,498
Weighted average grant date fair value
Weighted average grant date fair value, beginning balance (in dollars per share)	$ 49.37	$ 44.53
Weighted average grant date fair value, conversion adjustment (in dollars per share)	0	36.82
Weighted average grant date fair value, ending balance (in dollars per share)	$ 49.37	$ 45.26

Stock plans (Components of shar

Stock plans (Components of share compensation expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Total share compensation expenses
Share compensation expenses	$ 9,729	$ 9,491
Restricted share awards
Total share compensation expenses
Share compensation expenses	8,113	9,044
Restricted share units
Total share compensation expenses
Share compensation expenses	332	315
Performance shares
Total share compensation expenses
Share compensation expenses	$ 1,284	$ 132

Stock plans (Narrative) (Detail

Stock plans (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Stock plans (other details)
Number of shares reserved for issuance under the LTIP and STIP	2,753,292
Remaining number of shares reserved for issuance	706,006
Share compensation expenses	$ 9,729	$ 9,491
Options
Stock plans (other details)
Life of options	10 years
Restricted share awards
Stock plans (other details)
Share compensation expenses	$ 8,113	9,044
Unrecognized share compensation expenses	$ 40,926		$ 48,907
Weighted average period of recognizing share based compensation expenses	2 years 2 months 12 days		2 years 3 months 18 days
Restricted share units
Stock plans (other details)
Share compensation expenses	$ 332	315
Unrecognized share compensation expenses	$ 1,592		$ 1,909
Weighted average period of recognizing share based compensation expenses	2 years 3 months 29 days		2 years 4 months 17 days
Performance shares
Stock plans (other details)
Share compensation expenses	$ 1,284	$ 132
Unrecognized share compensation expenses	$ 6,597		$ 7,813
Weighted average period of recognizing share based compensation expenses	1 year 9 months 3 days		1 year 11 months 4 days
Performance share awards performance period	3 years

Debt and financing arrangemen71

Debt and financing arrangements (Summary of outstanding debentures and senior notes payable) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instruments [Line Items]
Debentures payable	$ 539,572	$ 539,158
Face amount	250,000	250,000
Less: Unamortized debt issuance costs	(4,386)	(4,436)
Total senior notes payable	245,614	245,564
Debentures payable	785,186	784,722
2006 Junior Subordinated
Debt Instruments [Line Items]
Debentures payable	150,000	150,000
2007 Junior Subordinated
Debt Instruments [Line Items]
Debentures payable	139,800	139,800
Face amount	200,000
Flagstone 2006 Junior Subordinated
Debt Instruments [Line Items]
Debentures payable	136,022	135,608
Flagstone 2007 Due July 30 2037
Debt Instruments [Line Items]
Debentures payable	113,750	$ 113,750
Face amount	$ 100,000

Debt and financing arrangemen72

Debt and financing arrangements (Summary of key terms of senior notes and debentures) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Debt Instruments [Line Items]
Commitment		$ 250,000	$ 250,000
Debentures payable		$ 539,572	539,158
2006 Junior Subordinated
Debt Instruments [Line Items]
Issuance date		Jun. 15, 2006
Maturity date		Jun. 15, 2036
Interest payments due		Quarterly
Interest rate term		5 years
Debentures payable		$ 150,000	150,000
2006 Junior Subordinated | Three month LIBOR
Debt Instruments [Line Items]
Spread on variable rate (in percent)		3.55%
Flagstone 2006 Junior Subordinated
Debt Instruments [Line Items]
Issuance date		Aug. 23, 2006
Maturity date		Sep. 15, 2036
Interest payments due		Quarterly
Debentures payable		$ 136,022	135,608
2007 Junior Subordinated
Debt Instruments [Line Items]
Issuance date		Jun. 21, 2007
Commitment		$ 200,000
Maturity date		Jun. 15, 2037
Interest payments due		Quarterly
Interest rate term		5 years
Debentures payable		$ 139,800	139,800
2007 Junior Subordinated | Three month LIBOR
Debt Instruments [Line Items]
Spread on variable rate (in percent)		2.95%
Flagstone 2007 Due July 30 2037
Debt Instruments [Line Items]
Issuance date		Jun. 8, 2007
Commitment		$ 100,000
Maturity date		Jul. 30, 2037
Interest payments due		Quarterly
Debentures payable		$ 113,750	$ 113,750
Flagstone 2007 Due September 15 2037
Debt Instruments [Line Items]
Issuance date		Sep. 20, 2007
Commitment		$ 25,000
Maturity date		Sep. 15, 2037
Interest payments due		Quarterly
2010 Senior Notes Due 2040
Debt Instruments [Line Items]
Issuance date		Jan. 26, 2010
Commitment		$ 250,000
Maturity date		Jan. 26, 2040
Interest payments due		Semi-annually in arrears
At Issuance | 2006 Junior Subordinated
Debt Instruments [Line Items]
Fixed interest rate (in percent)	[1]	9.069%
At Issuance | Flagstone 2006 Junior Subordinated | Three month LIBOR
Debt Instruments [Line Items]
Spread on variable rate (in percent)	[2]	3.54%
At Issuance | 2007 Junior Subordinated
Debt Instruments [Line Items]
Fixed interest rate (in percent)	[3]	8.48%
At Issuance | Flagstone 2007 Due July 30 2037 | Three month LIBOR
Debt Instruments [Line Items]
Spread on variable rate (in percent)	[2]	3.00%
At Issuance | Flagstone 2007 Due September 15 2037 | Three month LIBOR
Debt Instruments [Line Items]
Spread on variable rate (in percent)	[2]	3.10%
At Issuance | 2010 Senior Notes Due 2040
Debt Instruments [Line Items]
Fixed interest rate (in percent)	[4]	8.875%
Outstanding | 2006 Junior Subordinated
Debt Instruments [Line Items]
Effective percentage	[5]	5.831%
Outstanding | Flagstone 2006 Junior Subordinated
Debt Instruments [Line Items]
Effective percentage	[5]	6.463%
Outstanding | 2007 Junior Subordinated
Debt Instruments [Line Items]
Effective percentage	[5]	5.18%
Outstanding | Flagstone 2007 Due July 30 2037
Debt Instruments [Line Items]
Effective percentage	[5]	5.90%
Outstanding | Flagstone 2007 Due September 15 2037
Debt Instruments [Line Items]
Effective percentage	[5]	5.983%
Outstanding | 2010 Senior Notes Due 2040
Debt Instruments [Line Items]
Fixed interest rate (in percent)	[4]	8.875%
[1]	Fixed interest rate for 5 years, floating interest rate of three-month LIBOR plus 3.550% thereafter, reset quarterly.
[2]	Floating interest rate of three-month LIBOR plus amount stated, reset quarterly
[3]	Fixed interest rate for 5 years, floating interest rate of three-month LIBOR plus 2.950% thereafter, reset quarterly.
[4]	Fixed interest rate.
[5]	Fixed interest rate as a result of interest rate swap contracts entered into by the Company.

Debt and financing arrangemen73

Debt and financing arrangements (Credit facilities outstanding) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Commitment		$ 1,344,165	$ 1,319,096
Outstanding		426,327	428,180
Drawn		206,000	206,000
Cash and investments pledged as collateral		540,239	576,864
$85,000 syndicated unsecured letter of credit facility
Line of Credit Facility [Line Items]
Commitment		85,000	85,000
Outstanding	[1]	0	0
$300,000 syndicated secured letter of credit facility
Line of Credit Facility [Line Items]
Commitment		300,000	300,000
Outstanding	[1]	98,419	92,979
Cash and investments pledged as collateral		123,468	118,188
$100,000 secured bi-lateral letter of credit facility
Line of Credit Facility [Line Items]
Commitment		100,000	24,000
Outstanding	[1]	4,407	5,765
Cash and investments pledged as collateral		22,364	22,340
$25,000 IPC bi-lateral facility
Line of Credit Facility [Line Items]
Commitment		25,000	25,000
Outstanding	[1]	7,705	7,754
$236,000 Flagstone bi-lateral facility
Line of Credit Facility [Line Items]
Commitment		236,000	236,000
Outstanding	[1]	109,796	115,682
Cash and investments pledged as collateral		156,058	184,569
$65,000 unsecured revolving credit facility
Line of Credit Facility [Line Items]
Commitment		65,000	65,000
Outstanding	[1]	0	0
Drawn	[2]	0	0
$100,000 unsecured revolving credit facility
Line of Credit Facility [Line Items]
Commitment		100,000	100,000
Outstanding	[1]	0	0
Drawn	[2]	0	0
FHLB secured facility
Line of Credit Facility [Line Items]
Commitment		433,165	484,096
Outstanding	[1]	206,000	206,000
Drawn	[2]	206,000	206,000
Cash and investments pledged as collateral		$ 238,349	$ 251,767
[1]	Indicates utilization of commitment amount.
[2]	Represents drawn borrowings included in accounts payable and accrued expenses.

Debt and financing arrangemen74

Debt and financing arrangements (Components of finance expenses) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Debt Instruments [Line Items]
Finance expenses		$ 14,263	$ 13,943
2006 Junior Subordinated
Debt Instruments [Line Items]
Finance expenses		2,186	2,187
2007 Junior Subordinated
Debt Instruments [Line Items]
Finance expenses		1,810	1,810
Flagstone 2006 Junior Subordinated
Debt Instruments [Line Items]
Finance expenses		2,227	2,221
Flagstone 2007 Junior Subordinated
Debt Instruments [Line Items]
Finance expenses		1,713	1,723
2010 Senior Notes Due 2040
Debt Instruments [Line Items]
Finance expenses		5,597	5,597
Credit facilities
Debt Instruments [Line Items]
Finance expenses		416	218
Bank and other charges
Debt Instruments [Line Items]
Finance expenses		263	151
AlphaCat fees
Debt Instruments [Line Items]
Finance expenses	[1]	$ 51	$ 36
[1]	Includes finance expenses incurred by AlphaCat Managers Ltd. in relation to fund raising for the AlphaCat sidecars, the AlphaCat ILS funds and AlphaCat direct.

Accumulated other comprehensi75

Accumulated other comprehensive loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance - Beginning of period	$ 3,895,072
Amounts reclassified from accumulated other comprehensive loss		$ 0
Balance - End of period	3,901,232	3,911,876
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance - Beginning of period	(22,192)	(23,216)
Other comprehensive income (loss), net of tax	30,562	763
Amounts reclassified from accumulated other comprehensive loss	1,035
Balance - End of period	9,405	(22,453)
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance - Beginning of period	(18,217)	(22,274)
Other comprehensive income (loss), net of tax	1,837	597
Amounts reclassified from accumulated other comprehensive loss	0
Balance - End of period	(16,380)	(21,677)
Minimum pension liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance - Beginning of period	2,719	(150)
Other comprehensive income (loss), net of tax	(38)	68
Amounts reclassified from accumulated other comprehensive loss	0
Balance - End of period	2,681	(82)
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance - Beginning of period	(6,694)	(792)
Other comprehensive income (loss), net of tax	28,763	98
Amounts reclassified from accumulated other comprehensive loss	1,035
Balance - End of period	$ 23,104	$ (694)

Commitments and contingencies76

Commitments and contingencies (Lloyd's syndicate) (Details) - Lloyd's Syndicate 1183 £ in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)	Mar. 31, 2018GBP (£)	Dec. 31, 2017USD ($)
Funds at Lloyd's and Lloyd's Central Fund
Maximum premium levies assessable, percent	3.00%	3.00%
Estimated underwriting capacity | £		£ 650,000
Exchange rate	£1 equals $1.40	£1 equals $1.40
Maximum premium levies assessable, amount	$ 27,300		$ 26,325
2018 Underwriting Year
Loss Contingencies [Line Items]
Components of required capital	$ 661,600
2017 Underwriting Year
Loss Contingencies [Line Items]
Components of required capital			$ 583,600

Commitments and contingencies77

Commitments and contingencies (Other commitments) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Remaining commitment		$ 222,806	$ 234,775
Capital commitment		268,000	268,000
Fixed maturity investments
Other Commitments [Line Items]
Remaining commitment	[1]	28,067	22,082
Other investments
Other Commitments [Line Items]
Remaining commitment	[2]	87,353	86,697
Investment affiliate
Other Commitments [Line Items]
Remaining commitment		$ 107,386	$ 125,996
[1]	The Company has an outstanding commitment to participate in certain secured loan facilities through participation agreements with an established loan originator
[2]	The Company’s total capital commitments related to other investments as at March 31, 2018 was $268,000 (December 31, 2017: $268,000).

Related party transactions (Det

Related party transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Investments in affiliates	$ 113,471		$ 100,137
Remaining commitment	222,806		234,775
Wellington Insurance Company
Related Party Transaction [Line Items]
Gross premiums written	782	$ 2,974
Earned premium adjustments	778	861
Premiums receivable	262		211
Investment affiliate
Related Party Transaction [Line Items]
Investments in affiliates	113,471	94,697	100,137	$ 100,431
Remaining commitment	107,386		$ 125,996
Partnership fees incurred	$ 132	$ 356

Earnings per share (Details)

Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Basic earnings per share
Net (loss) income (attributable) available to Validus common shareholders	$ (4,078)	$ 94,561
Weighted average number of common shares outstanding	79,325,688	79,133,671
Basic earnings per share available to common shareholders	$ (0.05)	$ 1.19
Earnings per diluted share
Net (loss) income (attributable) available to Validus common shareholders		$ 94,561	$ (4,078)
Weighted average number of common shares outstanding	79,325,688	79,133,671
Weighted average number of diluted common shares outstanding	79,325,688	80,739,142
Earnings per diluted share available to common shareholders	$ (0.05)	$ 1.17
Other details:
Anti-dilutive securities excluded from the calculation of diluted earnings per share		1,503
Stock options
Earnings per diluted share
Share equivalents	0	15,379
Unvested restricted shares
Earnings per diluted share
Share equivalents	0	1,590,092

Segment information (Segment re

Segment information (Segment reporting by segment - Underwriting activities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
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
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 (loss) income (attributable) available to Validus common shareholders	(4,078)	94,561
Operating Segments | Reinsurance segment
Segment Reporting Information [Line Items]
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
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
Net premiums written / Gross premiums written	75.20%	82.20%
Loss and loss expense ratio	46.00%	34.90%
Policy acquisition cost ratio	21.50%	18.80%
General and administrative expenses	14.10%	9.80%
Expense ratio	35.60%	28.60%
Combined ratio	81.60%	63.50%
Operating Segments | Insurance segment
Segment Reporting Information [Line Items]
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
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)
Net premiums written / Gross premiums written	75.60%	79.40%
Loss and loss expense ratio	61.20%	66.90%
Policy acquisition cost ratio	20.00%	21.90%
General and administrative expenses	23.70%	17.40%
Expense ratio	43.70%	39.30%
Combined ratio	104.90%	106.20%

Segment information (Segment 81

Segment information (Segment reporting by segment - Asset management activities (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Share compensation expenses		$ 9,729	$ 9,491
Finance expenses		14,263	13,943
Tax (benefit)		(6,833)	(3,549)
Foreign exchange gains		525	1,569
Net investment income		52,072	40,214
Gross premiums written		1,832,456	1,190,857
Operating Segments | Asset management segment
Segment Reporting Information [Line Items]
Third party management fees		6,209	4,644
Related party management fees		443	631
Asset Management Fee Revenue		6,652	5,275
Other General and Administrative Expense		4,547	3,844
Share compensation expenses		41	82
Finance expenses		78	31
Tax (benefit)		(7)	(1)
Foreign exchange gains		(1)	1
Operating Expenses		4,660	3,955
Income Before Investment Income From Funds And Sidecars		1,992	1,320
Net investment income		5,272	4,812
Validus share of segmental (loss) income		7,264	6,132
Gross premiums written		286,625	164,926
AlphaCat sidecars | Operating Segments | Asset management segment
Segment Reporting Information [Line Items]
Net investment income	[1]	32	(112)
Gross premiums written		(143)	66
AlphaCat ILS funds - Lower Risk | Operating Segments | Asset management segment
Segment Reporting Information [Line Items]
Net investment income	[1],[2]	1,234	2,189
Gross premiums written		109,950	52,908
AlphaCat ILS funds - Higher Risk | Operating Segments | Asset management segment
Segment Reporting Information [Line Items]
Net investment income	[1],[2]	3,820	2,367
Gross premiums written		165,896	93,536
BetaCat ILS funds | Operating Segments | Asset management segment
Segment Reporting Information [Line Items]
Net investment income	[1]	186	368
AlphaCat direct | Operating Segments | Asset management segment
Segment Reporting Information [Line Items]
Gross premiums written	[3]	$ 10,922	$ 18,416
[1]	The investment income (loss) from funds and sidecars is based on equity accounting.
[2]	Lower risk AlphaCat ILS funds have a maximum permitted portfolio expected loss of less than 7%, whereas higher risk AlphaCat ILS funds have a maximum permitted portfolio expected loss of 7% or greater. The portfolio expected loss represents the average annual loss over the set of simulation scenarios divided by the total limit.
[3]	AlphaCat Direct includes direct investments from a third party investor in AlphaCat Re.

Segment information (Segment 82

Segment information (Segment reporting by segment - Corporate and investments) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net investment income		$ 52,072	$ 40,214
Net realized gains (losses) on investments		2,200	(1,164)
Change in net unrealized (losses) gains on investments		(57,381)	13,348
Income from investment affiliates		13,068	5,188
Net investment return	[1]	9,959	57,586
General and administrative expenses		114,726	87,924
Share compensation expenses		9,729	9,491
Finance expenses		14,263	13,943
Preferred Stock Dividends, Income Statement Impact		5,828	2,203
Tax (benefit)		(6,833)	(3,549)
Foreign exchange gains		525	1,569
Transaction expenses		7,756	0
Net (loss) income (attributable) available to Validus common shareholders		(4,078)	94,561
Corporate & Investments
Segment Reporting Information [Line Items]
Net investment income	[2]	39,791	36,192
Net realized gains (losses) on investments	[2]	1,142	(2,892)
Change in net unrealized (losses) gains on investments	[2]	(56,777)	14,349
Income from investment affiliates		13,068	5,188
Net investment return	[1]	(2,776)	52,837
General and administrative expenses		12,309	17,961
Share compensation expenses		4,036	3,413
Finance expenses	[2]	14,090	13,864
Preferred Stock Dividends, Income Statement Impact		5,828	2,203
Tax (benefit)	[2]	(6,826)	(3,548)
Operating Expenses		29,437	33,893
Foreign exchange gains	[2]	(3)	1,103
Other Income Loss Corporate And Investments		44	94
Transaction expenses		7,756	0
Other Items Corporate And Investments		(7,715)	1,197
Net (loss) income (attributable) available to Validus common shareholders		$ (39,928)	$ 20,141
[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]	These items exclude the components which are included in the Asset Management segment income (loss) and amounts which are consolidated from VIEs.

Segment information (Segment co

Segment information (Segment consolidation) (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2018USD ($)segments	Mar. 31, 2017USD ($)
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).

Segment information (Gross prem

Segment information (Gross premiums written by geographic location and segment) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 1,832,456	$ 1,190,857
Percent of gross premiums written		100.00%	100.00%
United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 790,394	$ 442,319
Percent of gross premiums written		43.10%	37.10%
Worldwide excluding United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	$ 94,436	$ 74,781
Percent of gross premiums written	[1]	5.20%	6.30%
Australia and New Zealand
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 9,313	$ 3,963
Percent of gross premiums written		0.50%	0.30%
Europe
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 43,880	$ 41,092
Percent of gross premiums written		2.40%	3.50%
Latin America and Caribbean
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 24,984	$ 30,647
Percent of gross premiums written		1.40%	2.60%
Japan
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 3,447	$ 4,149
Percent of gross premiums written		0.20%	0.30%
Canada
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 4,668	$ 2,807
Percent of gross premiums written		0.30%	0.20%
Rest of the world
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[2]	$ 45,518	$ 35,495
Percent of gross premiums written	[2]	2.50%	3.00%
Sub-total, non United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 226,246	$ 192,934
Percent of gross premiums written		12.30%	16.20%
Worldwide including United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	$ 389,566	$ 246,297
Percent of gross premiums written	[1]	21.30%	20.70%
Other location non-specific
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[3]	$ 426,250	$ 309,307
Percent of gross premiums written	[3]	23.30%	26.00%
Operating Segments | Reinsurance segment
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		$ 765,573	$ 643,141
Operating Segments | Reinsurance segment | United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		200,174	223,928
Operating Segments | Reinsurance segment | Worldwide excluding United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	39,325	35,208
Operating Segments | Reinsurance segment | Australia and New Zealand
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		1,136	789
Operating Segments | Reinsurance segment | Europe
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		37,982	31,945
Operating Segments | Reinsurance segment | Latin America and Caribbean
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		6,539	9,960
Operating Segments | Reinsurance segment | Japan
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		2,100	1,951
Operating Segments | Reinsurance segment | Canada
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		3,735	2,358
Operating Segments | Reinsurance segment | Rest of the world
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[2]	18,298	15,103
Operating Segments | Reinsurance segment | Sub-total, non United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		109,115	97,314
Operating Segments | Reinsurance segment | Worldwide including United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	118,809	95,801
Operating Segments | Reinsurance segment | Other location non-specific
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[3]	337,475	226,098
Operating Segments | Insurance segment
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		785,795	382,790
Operating Segments | Insurance segment | United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		560,722	190,188
Operating Segments | Insurance segment | Worldwide excluding United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	52,232	32,538
Operating Segments | Insurance segment | Australia and New Zealand
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		8,177	3,174
Operating Segments | Insurance segment | Europe
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		5,560	8,681
Operating Segments | Insurance segment | Latin America and Caribbean
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		18,445	20,687
Operating Segments | Insurance segment | Japan
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		916	1,005
Operating Segments | Insurance segment | Canada
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		933	449
Operating Segments | Insurance segment | Rest of the world
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[2]	27,220	20,392
Operating Segments | Insurance segment | Sub-total, non United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		113,483	86,926
Operating Segments | Insurance segment | Worldwide including United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	26,655	27,187
Operating Segments | Insurance segment | Other location non-specific
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[3]	84,935	78,489
Operating Segments | Asset management segment
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		286,625	164,926
Operating Segments | Asset management segment | United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		31,023	28,203
Operating Segments | Asset management segment | Worldwide excluding United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	2,879	7,035
Operating Segments | Asset management segment | Australia and New Zealand
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Operating Segments | Asset management segment | Europe
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		338	466
Operating Segments | Asset management segment | Latin America and Caribbean
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Operating Segments | Asset management segment | Japan
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		431	1,193
Operating Segments | Asset management segment | Canada
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Operating Segments | Asset management segment | Rest of the world
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[2]	0	0
Operating Segments | Asset management segment | Sub-total, non United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		3,648	8,694
Operating Segments | Asset management segment | Worldwide including United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	248,114	123,309
Operating Segments | Asset management segment | Other location non-specific
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[3]	3,840	4,720
Eliminations
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		(5,537)	0
Eliminations | United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		(1,525)	0
Eliminations | Worldwide excluding United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	0	0
Eliminations | Australia and New Zealand
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Eliminations | Europe
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Eliminations | Latin America and Caribbean
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Eliminations | Japan
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Eliminations | Canada
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Eliminations | Rest of the world
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[2]	0	0
Eliminations | Sub-total, non United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written		0	0
Eliminations | Worldwide including United States
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[1]	(4,012)	0
Eliminations | Other location non-specific
Gross premiums written allocated to the territory of coverage exposure
Gross premiums written	[3]	$ 0	$ 0
[1]	Represents risks in two or more geographic zones.
[2]	Represents risks in one geographic zone.
[3]	The other locations non-specific category refers to business for which an analysis of exposure by geographic zone is not applicable since these exposures can span multiple geographic areas and, in some instances, are not fixed locations.