RenaissanceRe (RNR) 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. 27, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	RENAISSANCERE HOLDINGS LTD.
Trading Symbol	RNR
Entity Central Index Key	913,144
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding (in shares)		40,245,556

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Fixed maturity investments trading, at fair value – amortized cost $7,470,003 at March 31, 2018 (December 31, 2017 – $7,434,870)	$ 7,404,761	$ 7,426,555
Short term investments, at fair value	1,616,597	991,863
Equity investments trading, at fair value	387,462	388,254
Other investments, at fair value	692,652	594,793
Investments in other ventures, under equity method	120,232	101,974
Total investments	10,221,704	9,503,439
Cash and cash equivalents	647,973	1,361,592
Premiums receivable	1,684,630	1,304,622
Prepaid reinsurance premiums	794,921	533,546
Reinsurance recoverable	1,572,321	1,586,630
Accrued investment income	43,069	42,235
Deferred acquisition costs	477,010	426,551
Receivable for investments sold	111,431	103,145
Other assets	127,571	121,226
Goodwill and other intangible assets	241,572	243,145
Total assets	15,922,202	15,226,131
Liabilities
Reserve for claims and claim expenses	4,912,727	5,080,408
Unearned premiums	1,961,746	1,477,609
Debt	989,995	989,623
Reinsurance balances payable	1,758,948	989,090
Payable for investments purchased	306,664	208,749
Other liabilities	130,505	792,771
Total liabilities	10,060,585	9,538,250
Commitments and Contingencies
Redeemable noncontrolling interests	1,425,364	1,296,506
Shareholders’ Equity
Preference shares: $1.00 par value – 16,000,000 shares issued and outstanding at March 31, 2018 (December 31, 2017 – 16,000,000)	400,000	400,000
Common shares: $1.00 par value – 40,245,556 shares issued and outstanding at March 31, 2018 (December 31, 2017 – 40,023,789)	40,246	40,024
Additional paid-in capital	38,552	37,355
Accumulated other comprehensive income	194	224
Retained earnings	3,957,261	3,913,772
Total shareholders’ equity attributable to RenaissanceRe	4,436,253	4,391,375
Total liabilities, noncontrolling interests and shareholders’ equity	$ 15,922,202	$ 15,226,131

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Fixed maturity investments trading, amortized cost	$ 7,470,003	$ 7,434,870
Preference shares, par value (In dollars per share)	$ 1	$ 1
Preference shares, shares issued (In shares)	16,000,000	16,000,000
Preference shares, shares outstanding (In shares)	16,000,000	16,000,000
Common shares, par value (In dollars per share)	$ 1	$ 1
Common shares, Shares issued (In shares)	40,245,556	40,023,789
Common shares, shares outstanding (In shares)	40,245,556	40,023,789

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues
Gross premiums written	$ 1,159,652	$ 922,090
Net premiums written	663,044	544,136
Increase in unearned premiums	(222,762)	(178,091)
Net premiums earned	440,282	366,045
Net investment income	56,476	54,325
Net foreign exchange gains	3,757	8,165
Equity in earnings (losses) of other ventures	857	(1,507)
Other (loss) income	(1,242)	1,665
Net realized and unrealized (losses) gains on investments	(82,144)	43,373
Total revenues	417,986	472,066
Expenses
Net claims and claim expenses incurred	171,703	193,081
Acquisition expenses	97,711	83,282
Operational expenses	41,272	47,283
Corporate expenses	6,733	5,286
Interest expense	11,767	10,526
Total expenses	329,186	339,458
Income before taxes	88,800	132,608
Income tax benefit (expense)	3,407	(334)
Net income	92,207	132,274
Net income attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Net income attributable to RenaissanceRe	62,308	97,947
Dividends on preference shares	(5,595)	(5,595)
Net income available to RenaissanceRe common shareholders	$ 56,713	$ 92,352
Net income available to RenaissanceRe common shareholders per common share – basic (in dollars per share)	$ 1.42	$ 2.26
Net income available to RenaissanceRe common shareholders per common share – diluted (in dollars per share)	1.42	2.25
Dividends declared per common share (in dollars per share)	$ 0.33	$ 0.32

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Comprehensive income
Net income	$ 92,207	$ 132,274
Change in net unrealized gains on investments	(30)	(1,491)
Comprehensive income	92,177	130,783
Net income attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Comprehensive income attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Comprehensive income attributable to RenaissanceRe	$ 62,278	$ 96,456

Consolidated Statements Of Chan

Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Preference Shares	Common Shares	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Retained Earnings
Beginning balance at Dec. 31, 2016		$ 400,000	$ 41,187	$ 216,558	$ 1,133	$ 4,207,699
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of shares			(550)	(79,459)
Exercise of options and issuance of restricted stock awards			148	(5,840)
Change in redeemable noncontrolling interests				(86)
Change in net unrealized gains on investments					(1,491)
Cumulative effect of adoption of ASU 2016-09 (Note 2)						2,213
Net income	$ 97,947					132,274
Net income attributable to redeemable noncontrolling interests	(34,327)					(34,327)
Dividends on common shares						(13,027)
Dividends on preference shares	(5,595)					(5,595)
Ending balance at Mar. 31, 2017	4,860,837	400,000	40,785	131,173	(358)	4,289,237
Beginning balance at Dec. 31, 2017	4,391,375	400,000	40,024	37,355	224	3,913,772
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of shares			0	0
Exercise of options and issuance of restricted stock awards			222	1,141
Change in redeemable noncontrolling interests				56
Change in net unrealized gains on investments					(30)
Cumulative effect of adoption of ASU 2016-09 (Note 2)						0
Net income	62,308					92,207
Net income attributable to redeemable noncontrolling interests	(29,899)					(29,899)
Dividends on common shares						(13,224)
Dividends on preference shares	(5,595)					(5,595)
Ending balance at Mar. 31, 2018	$ 4,436,253	$ 400,000	$ 40,246	$ 38,552	$ 194	$ 3,957,261

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows (used in) provided by operating activities
Net income	$ 92,207	$ 132,274
Adjustments to reconcile net income to net cash (used in) provided by operating activities
Amortization, accretion and depreciation	13,740	6,390
Equity in undistributed earnings (losses) of other ventures	(314)	4,818
Net realized and unrealized losses (gains) on investments	82,144	(43,373)
Net unrealized (gains) losses included in net investment income	(1,465)	(6,863)
Change in:
Premiums receivable	(380,008)	(295,952)
Prepaid reinsurance premiums	(261,375)	(186,831)
Reinsurance recoverable	14,309	(46,255)
Deferred acquisition costs	(50,459)	(53,356)
Reserve for claims and claim expenses	(167,681)	86,394
Unearned premiums	484,137	364,922
Reinsurance balances payable	769,858	298,283
Other	(632,442)	(59,412)
Net cash (used in) provided by operating activities	(37,349)	201,039
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	2,318,859	2,682,386
Purchases of fixed maturity investments trading	(2,312,461)	(3,007,124)
Net sales of equity investments trading	137	13,747
Net (purchases) sales of short term investments	(594,641)	245,693
Net (purchases) sales of other investments	(98,639)	36,402
Net purchases of investments in other ventures	(17,974)	0
Return of investment from investment in other ventures	0	20,000
Net cash used in investing activities	(704,719)	(8,896)
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	(13,224)	(13,027)
Dividends paid – preference shares	(5,595)	(5,595)
RenaissanceRe common share repurchases	0	(80,009)
Net third party redeemable noncontrolling interest share transactions	52,759	(51,166)
Taxes paid on withholding shares	(7,034)	(11,018)
Net cash provided by (used in) financing activities	26,906	(160,815)
Effect of exchange rate changes on foreign currency cash	1,543	1,602
Net (decrease) increase in cash and cash equivalents	(713,619)	32,930
Cash and cash equivalents, beginning of period	1,361,592	421,157
Cash and cash equivalents, end of period	$ 647,973	$ 454,087

Organization

Organization	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	ORGANIZATION This report on Form 10-Q should be read in conjunction with the RenaissanceRe’s Annual Report on Form 10-K (“Form 10-K”) for the fiscal year ended December 31, 2017 . RenaissanceRe was formed under the laws of Bermuda on June 7, 1993. Together with its wholly owned and majority-owned subsidiaries and DaVinciRe (as defined below), the Company provides property, casualty and specialty reinsurance and certain insurance solutions to its customers. • Renaissance Reinsurance, a Bermuda-domiciled reinsurance company, is the Company’s principal reinsurance subsidiary and provides property,casualty and specialty reinsurance coverages to insurers and reinsurers on a worldwide basis. • Renaissance Reinsurance U.S. Inc. (“Renaissance Reinsurance U.S.”) is a reinsurance company domiciled in the state of Maryland that provides property,casualty and specialty reinsurance coverages to insurers and reinsurers, primarily in the Americas. • RenaissanceRe Underwriting Managers U.S. LLC, a specialty reinsurance agency domiciled in the state of Connecticut, provides specialty treaty reinsurance solutions on both a quota share and excess of loss basis; and writes business on behalf of RenaissanceRe Specialty U.S. Ltd. (“RenaissanceRe Specialty U.S.”), a Bermuda-domiciled reinsurer, which operates subject to U.S. federal income tax, and RenaissanceRe Syndicate 1458 (“Syndicate 1458”). • Syndicate 1458 is the Company’s Lloyd’s syndicate. RenaissanceRe Corporate Capital (UK) Limited (“RenaissanceRe CCL”), a wholly owned subsidiary of RenaissanceRe, is Syndicate 1458’s sole corporate member and RenaissanceRe Syndicate Management Ltd. (“RSML”), a wholly owned subsidiary of RenaissanceRe, is the managing agent for Syndicate 1458. • The Company also manages property, casualty and specialty reinsurance business written on behalf of joint ventures, which principally include Top Layer Reinsurance Ltd. (“Top Layer Re”), recorded under the equity method of accounting, and DaVinci Reinsurance Ltd. (“DaVinci”). Because the Company owns a noncontrolling equity interest in, but controls a majority of the outstanding voting power of DaVinci’s parent, DaVinciRe Holdings Ltd. (“DaVinciRe”), the results of DaVinci and DaVinciRe are consolidated in the Company’s financial statements and all significant intercompany transactions have been eliminated. Redeemable noncontrolling interest - DaVinciRe represents the interests of external parties with respect to the net income and shareholders’ equity of DaVinciRe. Renaissance Underwriting Managers, Ltd. (“RUM”), a wholly owned subsidiary of RenaissanceRe, acts as exclusive underwriting manager for these joint ventures in return for fee-based income and profit participation. • RenaissanceRe Medici Fund Ltd. (“Medici”) is an exempted fund, incorporated under the laws of Bermuda. Medici’s objective is to seek to invest substantially all of its assets in various insurance based investment instruments that have returns primarily tied to property catastrophe risk. Third-party investors have subscribed for a portion of the participating, non-voting common shares of Medici. Because the Company owns a noncontrolling equity interest in, but controls a majority of the outstanding voting power of Medici’s parent, RenaissanceRe Fund Holdings Ltd. (“Fund Holdings”), the results of Medici and Fund Holdings are consolidated in the Company’s financial statements and all significant inter-company transactions have been eliminated. Redeemable noncontrolling interest - Medici represents the interests of external parties with respect to the net income and shareholders’ equity of Medici. • Effective January 1, 2013, the Company formed and launched a managed joint venture, Upsilon RFO Re Ltd., formerly known as Upsilon Reinsurance II Ltd. (“Upsilon RFO”), a Bermuda domiciled special purpose insurer (“SPI”), to provide additional capacity to the worldwide aggregate and per-occurrence primary and retrocessional property catastrophe excess of loss market. Upsilon RFO is considered a variable interest entity (“VIE”) and the Company is considered the primary beneficiary. As a result, Upsilon RFO is consolidated by the Company and all significant inter-company transactions have been eliminated. • Effective November 13, 2014, the Company incorporated RenaissanceRe Upsilon Fund Ltd. (“Upsilon Fund”), an exempted Bermuda segregated accounts company. Upsilon Fund was formed to provide a fund structure through which third-party investors can invest in reinsurance risk managed by the Company. As a segregated accounts company, Upsilon Fund is permitted to establish segregated accounts to invest in and hold identified pools of assets and liabilities. Each pool of assets and liabilities in each segregated account is structured to be ring-fenced from any claims from the creditors of Upsilon Fund’s general account and from the creditors of other segregated accounts within Upsilon Fund. Third-party investors purchase redeemable, non-voting preference shares linked to specific segregated accounts of Upsilon Fund and own 100% of these shares. Upsilon Fund is an investment company and is considered a VIE. The Company is not considered the primary beneficiary of Upsilon Fund and, as a result, the Company does not consolidate the financial position and results of operations of Upsilon Fund. • Effective November 7, 2016, Fibonacci Reinsurance Ltd. ("Fibonacci Re"), a Bermuda-domiciled SPI, was formed to provide collateralized capacity to Renaissance Reinsurance and its affiliates. Fibonacci Re raised capital from third-party investors and the Company, via private placements of participating notes which are listed on the Bermuda Stock Exchange. Fibonacci Re is considered a VIE. The Company is not considered the primary beneficiary of Fibonacci Re and, as a result, the Company does not consolidate the financial position and results of operations of Fibonacci Re. • Effective December 22, 2017, the Company and Reinsurance Group of America, Incorporated closed an initiative (“Langhorne”) to source third party capital to support reinsurers targeting large in-force life and annuity blocks. Langhorne Holdings LLC (“Langhorne Holdings”) is a company that owns and manages certain reinsurance entities within Langhorne. Langhorne Partners LLC (“Langhorne Partners”) is the general partner for Langhorne and the entity which manages the third-party investors investing into Langhorne Holdings. The Company concluded that Langhorne Holdings meets the definition of a VIE. The Company is not the primary beneficiary of Langhorne Holdings and as a result, the Company does not consolidate the financial position or results of operations of Langhorne Holdings. The Company concluded that Langhorne Partners is not a VIE. The Company will account for its investments in Langhorne Holdings and Langhorne Partners under the equity method of accounting, one quarter in arrears.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES There have been no material changes to the Company’s significant accounting policies as described in its Form 10-K for the year ended December 31, 2017 , except as noted below. BASIS OF PRESENTATION These consolidated financial statements have been prepared on the basis of accounting principles generally accepted in the United States (“GAAP”) for interim financial information and in conformity with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. In the opinion of management, these unaudited consolidated financial statements reflect all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation 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 from these statements. Certain comparative information has been reclassified to conform to the current presentation. Because of the seasonality of the Company’s business, the results of operations and cash flows for any interim period will not necessarily be indicative of the results of operations and cash flows for the full fiscal year or subsequent quarters. USE OF ESTIMATES IN FINANCIAL STATEMENTS The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported and disclosed amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from those estimates. The major estimates reflected in the Company’s consolidated financial statements include, but are not limited to, the reserve for claims and claim expenses; reinsurance recoverables, including allowances for reinsurance recoverables deemed uncollectible; estimates of written and earned premiums; fair value, including the fair value of investments, financial instruments and derivatives; impairment charges; and the Company’s deferred tax valuation allowance. RECENTLY ADOPTED ACCOUNTING PRONOUNCEMENTS Revenue from Contracts with Customers In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 provides comprehensive guidance on the recognition of revenue from customers arising from the transfer of goods and services. The core principle 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. ASU 2014-09 also provides guidance on accounting for certain contract costs and will also require new disclosures. ASU 2014-09 was to be effective for public business entities in annual and interim periods beginning after December 15, 2016, however in July 2015, the FASB decided to defer by one year the effective dates of ASU 2014-09, and as a result, ASU 2014-09 is effective for public business entities in annual and interim periods beginning after December 15, 2017. ASU 2014-09 notably excludes the accounting for insurance contracts, leases, financial instruments and guarantees. The Company’s implementation efforts primarily focused on other income and operational expenses on its consolidated statements of operations. The adoption of ASU 2014-09 did not have a material impact on the Company’s consolidated statements of operations and financial position. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-01”). ASU 2016-01 requires equity investments (except those accounted for under the equity method of accounting or those that result in the consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income, simplifies the impairment assessment of equity investments without readily determinable values by requiring a qualitative assessment to identify impairment, eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost, requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes, requires separate presentation in other comprehensive income of the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the organization has elected to measure the liabilities in accordance with the fair value option, requires the separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or the accompanying notes to the financial statements and clarifies that the reporting organization should evaluate the need for a valuation allowance on a deferred tax asset related to available for sale securities in combination with the organization’s other deferred tax assets. ASU 2016-01 is effective for public business entities in annual and interim periods beginning after December 15, 2017. The adoption of ASU 2016-01 did not have a material impact on the Company’s consolidated statements of operations and financial position. Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). ASU 2016-15 clarifies the classification of receipts and payments in the statement of cash flows. ASU 2016-15 provides guidance related to (1) settlement and payment of zero coupon debt instruments, (2) contingent consideration, (3) proceeds from settlement of insurance claims, (4) proceeds from settlement of corporate and bank owned life insurance policies, (5) distributions from equity method investees, (6) cash receipts from beneficial interests obtained by a transferor, and (7) general guidelines for cash receipts and payments that have more than one aspect of classification. ASU 2016-15 is effective for public business entities for annual periods beginning after December 15, 2017, and interim periods within those fiscal years. The adoption of ASU 2016-15 resulted in the reclassification of $20.0 million of cash inflows from cash flows provided by operating activities, to cash flows used in investing activities for the three months ended March 31, 2017. This amount related to a return of investment associated with the Company’s investment in Top Layer Reinsurance Ltd, recorded under the equity method of accounting. Improvements to Employee Share-Based Payment Accounting In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 was issued to simplify several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and the classification of taxes paid on the statements of cash flows. ASU 2016-09 became effective for the Company in annual and interim periods beginning after December 15, 2016. The cumulative effect of the adoption of ASU 2016-09 was a $2.2 million increase to opening retained earnings as of January 1, 2017. RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS NOT YET ADOPTED Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 requires lessees to recognize lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous guidance. ASU 2016-02 is effective for public business entities for annual and interim periods beginning after December 15, 2018. Early application is permitted. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position. Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 modifies the recognition of credit losses by replacing the incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU 2016-13 is applicable to financial assets such as loans, debt securities, trade receivables, off-balance sheet credit exposures, reinsurance receivables, and other financial assets that have the contractual right to receive cash. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectibility of the reported amount. The Company's invested assets are measured at fair value through net income, and therefore those invested assets would not be impacted by the adoption of ASU 2016-13. The Company has other financial assets, such as reinsurance recoverables, that could be impacted by the adoption of ASU 2016-13. ASU 2016-13 is effective for public business entities that are SEC filers for annual and interim periods beginning after December 15, 2019. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position. Intra-Entity Transfers of Assets Other Than Inventory In October 2016, the FASB issued ASU No. 2016-16, Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). ASU 2016-16 requires entities to recognize the income tax consequences of intra-entity transfers of assets other than inventory when the transfers occur; this is a change from current guidance which prohibits the recognition of current and deferred income taxes until the underlying assets have been sold to outside entities. ASU 2016-16 is effective for public business entities for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position. Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment (“ASU 2017-04”). Among other things, ASU 2017-04 requires the following: (1) the elimination of step two of the goodwill impairment test; entities will no longer utilize the implied fair value of their assets and liabilities for purposes of testing goodwill for impairment, (2) the quantitative portion of the goodwill impairment test will be performed by comparing the fair value of a reporting unit with its carrying amount; an impairment charge is to be recognized for the excess of carrying amount over fair value, but only to the extent of the amount of goodwill allocated to that reporting unit, and (3) foreign currency translation adjustments are not to be allocated to a reporting unit from an entity’s accumulated other comprehensive income; the reporting unit’s carrying amount should include only the currently translated balances of the assets and liabilities assigned to the reporting unit. ASU 2017-04 is effective for public business entities that are SEC filers for annual periods, or any interim goodwill impairment tests in annual periods, beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position.

Investments

Investments	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Investments	INVESTMENTS Fixed Maturity Investments Trading The following table summarizes the fair value of fixed maturity investments trading: March 31, December 31, U.S. treasuries $ 2,834,487 $ 3,168,763 Agencies 45,365 47,646 Municipal 506,470 509,802 Non-U.S. government (Sovereign debt) 303,056 287,660 Non-U.S. government-backed corporate 191,202 163,651 Corporate 2,147,578 2,063,459 Agency mortgage-backed 693,377 500,456 Non-agency mortgage-backed 302,638 300,331 Commercial mortgage-backed 197,126 202,062 Asset-backed 183,462 182,725 Total fixed maturity investments trading $ 7,404,761 $ 7,426,555 Contractual maturities of fixed maturity investments trading are described in the following table. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. March 31, 2018 Amortized Cost Fair Value Due in less than one year $ 496,788 $ 495,143 Due after one through five years 4,381,056 4,324,744 Due after five through ten years 1,073,453 1,064,575 Due after ten years 145,438 143,696 Mortgage-backed 1,189,730 1,193,141 Asset-backed 183,538 183,462 Total $ 7,470,003 $ 7,404,761 Equity Investments Trading The following table summarizes the fair value of equity investments trading: March 31, December 31, Financials $ 253,905 $ 253,543 Communications and technology 51,400 49,526 Industrial, utilities and energy 32,790 34,325 Consumer 23,886 24,779 Healthcare 21,042 21,364 Basic materials 4,439 4,717 Total $ 387,462 $ 388,254 Pledged Investments At March 31, 2018 , $4.7 billion of cash and investments at fair value were on deposit with, or in trust accounts for the benefit of, various counterparties, including with respect to the Company’s letter of credit facilities ( December 31, 2017 - $3.3 billion ). Of this amount, $1.7 billion is on deposit with, or in trust accounts for the benefit of, U.S. state regulatory authorities ( December 31, 2017 - $1.4 billion ). Reverse Repurchase Agreements At March 31, 2018 , the Company held $65.3 million ( December 31, 2017 - $30.0 million ) of reverse repurchase agreements. These loans are fully collateralized, are generally outstanding for a short period of time and are presented on a gross basis as part of short term investments on the Company’s consolidated balance sheets. The required collateral for these loans typically includes high-quality, readily marketable instruments at a minimum amount of 102% of the loan principal. Upon maturity, the Company receives principal and interest income. Net Investment Income The components of net investment income are as follows: Three months ended March 31, March 31, Fixed maturity investments $ 45,643 $ 43,419 Short term investments 5,304 1,724 Equity investments 698 811 Other investments Private equity investments (434 ) 7,802 Other 8,023 4,072 Cash and cash equivalents 565 189 59,799 58,017 Investment expenses (3,323 ) (3,692 ) Net investment income $ 56,476 $ 54,325 Net Realized and Unrealized (Losses) Gains on Investments Net realized and unrealized (losses) gains on investments are as follows: Three months ended March 31, March 31, Gross realized gains $ 4,583 $ 11,461 Gross realized losses (25,853 ) (16,533 ) Net realized losses on fixed maturity investments (21,270 ) (5,072 ) Net unrealized (losses) gains on fixed maturity investments trading (55,372 ) 24,635 Net realized and unrealized losses on investments-related derivatives (4,364 ) (56 ) Net realized gains on equity investments trading sold during the period 234 20,915 Net unrealized (losses) gains on equity investments trading still held at reporting date (1,372 ) 2,951 Net realized and unrealized (losses) gains on equity investments trading (1,138 ) 23,866 Net realized and unrealized (losses) gains on investments $ (82,144 ) $ 43,373

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The use of fair value to measure certain assets and liabilities with resulting unrealized gains or losses is pervasive within the Company’s consolidated financial statements. Fair value is defined under accounting guidance currently applicable to the Company to be the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between open market participants at the measurement date. The Company recognizes the change in unrealized gains and losses arising from changes in fair value in its consolidated statements of operations. FASB ASC Topic Fair Value Measurements and Disclosures prescribes a fair value hierarchy that prioritizes the inputs to the respective valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to valuation techniques that use at least one significant input that is unobservable (Level 3). The three levels of the fair value hierarchy are described below: • Fair values determined by Level 1 inputs utilize unadjusted quoted prices obtained from active markets for identical assets or liabilities for which the Company has access. The fair value is determined by multiplying the quoted price by the quantity held by the Company; • Fair values determined by Level 2 inputs utilize inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, and inputs other than quoted prices that are observable for the asset or liability, such as interest rates and yield curves that are observable at commonly quoted intervals, broker quotes and certain pricing indices; and • Level 3 inputs are based all or in part on significant unobservable inputs for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. In these cases, significant management assumptions can be used to establish management’s best estimate of the assumptions used by other market participants in determining the fair value of the asset or liability. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, the level in the fair value hierarchy within which the fair value measurement in its entirety falls has been determined based on the lowest level input that is significant to the fair value measurement of the asset or liability. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and the Company considers factors specific to the asset or liability. In order to determine if a market is active or inactive for a security, the Company considers a number of factors, including, but not limited to, the spread between what a seller is asking for a security and what a buyer is bidding for the same security, the volume of trading activity for the security in question, the price of the security compared to its par value (for fixed maturity investments), and other factors that may be indicative of market activity. There have been no material changes in the Company’s valuation techniques, nor have there been any transfers between Level 1 and Level 2, or Level 2 and Level 3 during the period represented by these consolidated financial statements. Below is a summary of the assets and liabilities that are measured at fair value on a recurring basis and also represents the carrying amount on the Company’s consolidated balance sheets: At March 31, 2018 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fixed maturity investments U.S. treasuries $ 2,834,487 $ 2,834,487 $ — $ — Agencies 45,365 — 45,365 — Municipal 506,470 — 506,470 — Non-U.S. government (Sovereign debt) 303,056 — 303,056 — Non-U.S. government-backed corporate 191,202 — 191,202 — Corporate 2,147,578 — 2,147,578 — Agency mortgage-backed 693,377 — 693,377 — Non-agency mortgage-backed 302,638 — 302,638 — Commercial mortgage-backed 197,126 — 197,126 — Asset-backed 183,462 — 183,462 — Total fixed maturity investments 7,404,761 2,834,487 4,570,274 — Short term investments 1,616,597 — 1,616,597 — Equity investments trading 387,462 387,462 — — Other investments Catastrophe bonds 476,534 — 476,534 — Private equity partnerships (1) 190,067 — — — Senior secured bank loan funds (1) 13,771 — — — Hedge funds (1) 12,280 — — — Total other investments 692,652 — 476,534 — Other assets and (liabilities) Assumed and ceded (re)insurance contracts (2) (2,780 ) — — (2,780 ) Derivatives (3) 7,514 (229 ) 7,743 — Total other assets and (liabilities) 4,734 (229 ) 7,743 (2,780 ) $ 10,106,206 $ 3,221,720 $ 6,671,148 $ (2,780 ) (1) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the consolidated balance sheet. (2) Included in assumed and ceded (re)insurance contracts at March 31, 2018 was $2.5 million and $5.3 million of other assets and other liabilities, respectively. (3) See “Note 13 . Derivative Instruments” for additional information related to the fair value by type of contract, of derivatives entered into by the Company. At December 31, 2017 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fixed maturity investments U.S. treasuries $ 3,168,763 $ 3,168,763 $ — $ — Agencies 47,646 — 47,646 — Municipal 509,802 — 509,802 — Non-U.S. government (Sovereign debt) 287,660 — 287,660 — Non-U.S. government-backed corporate 163,651 — 163,651 — Corporate 2,063,459 — 2,063,459 — Agency mortgage-backed 500,456 — 500,456 — Non-agency mortgage-backed 300,331 — 300,331 — Commercial mortgage-backed 202,062 — 202,062 — Asset-backed 182,725 — 182,725 — Total fixed maturity investments 7,426,555 3,168,763 4,257,792 — Short term investments 991,863 — 991,863 — Equity investments trading 388,254 388,254 — — Other investments Catastrophe bonds 380,475 — 380,475 — Private equity partnerships (1) 196,220 — — — Senior secured bank loan funds (1) 17,574 — — — Hedge funds (1) 524 — — — Total other investments 594,793 — 380,475 — Other assets and (liabilities) Assumed and ceded (re)insurance contracts (2) (2,952 ) — — (2,952 ) Derivatives (3) 4,636 (45 ) 4,681 — Total other assets and (liabilities) 1,684 (45 ) 4,681 (2,952 ) $ 9,403,149 $ 3,556,972 $ 5,634,811 $ (2,952 ) (1) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the consolidated balance sheet. (2) Included in assumed and ceded (re)insurance contracts at December 31, 2017 was $2.5 million and $5.5 million of other assets and other liabilities, respectively. (3) See “Note 13 . Derivative Instruments” for additional information related to the fair value by type of contract, of derivatives entered into by the Company. Level 1 and Level 2 Assets and Liabilities Measured at Fair Value Fixed Maturity Investments Fixed maturity investments included in Level 1 consist of the Company’s investments in U.S. treasuries. Fixed maturity investments included in Level 2 are agencies, municipal, non-U.S. government, non-U.S. government-backed corporate, corporate, agency mortgage-backed, non-agency mortgage-backed, commercial mortgage-backed and asset-backed. The Company’s fixed maturity investments are primarily priced using pricing services, such as index providers and pricing vendors, as well as broker quotations. In general, the pricing vendors provide pricing 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. Observable inputs include benchmark yields, reported trades, broker-dealer quotes, issuer spreads, bids, offers, reference data and industry and economic events. Index pricing generally relies on market traders as the primary source for pricing; however, models are also utilized to provide prices for all index eligible securities. The models use a variety of observable inputs such as benchmark yields, transactional data, dealer runs, broker-dealer quotes and corporate actions. Prices are generally verified using third-party data. Securities which are priced by an index provider are generally included in the index. 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 broker quotations 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. treasuries Level 1 - At March 31, 2018 , the Company’s U.S. treasuries fixed maturity investments were primarily priced by pricing services and had a weighted average effective yield of 2.3% and a weighted average credit quality of AA ( December 31, 2017 - 1.9% and AA, respectively). When pricing these securities, the pricing services utilize daily data from many real time market sources, including active broker dealers. Certain data sources are regularly reviewed for accuracy to attempt to ensure the most reliable price source is used for each issue and maturity date. Agencies Level 2 - At March 31, 2018 , the Company’s agency fixed maturity investments had a weighted average effective yield of 2.4% and a weighted average credit quality of AA ( December 31, 2017 - 2.1% and AA, respectively). The issuers of the Company’s agency fixed maturity investments primarily consist of the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation and other agencies. Fixed maturity investments included in agencies 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. Municipal Level 2 - At March 31, 2018 , the Company’s municipal fixed maturity investments had a weighted average effective yield of 2.5% and a weighted average credit quality of AA ( December 31, 2017 - 2.2% and AA, respectively). The Company’s municipal fixed maturity investments are primarily priced by pricing services. When evaluating these securities, the pricing services gather information regarding the security from third-party sources such as trustees, paying agents or issuers. 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 over widely accepted market benchmarks. Non-U.S. government (Sovereign debt) Level 2 - At March 31, 2018 , the Company’s non-U.S. government fixed maturity investments had a weighted average effective yield of 2.4% and a weighted average credit quality of AAA ( December 31, 2017 - 2.0% and AAA, respectively). The issuers of securities in this sector are non-U.S. governments and their respective agencies as well as supranational organizations. 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. Non-U.S. government-backed corporate Level 2 - At March 31, 2018 , the Company’s non-U.S. government-backed corporate fixed maturity investments had a weighted average effective yield of 2.7% and a weighted average credit quality of AA ( December 31, 2017 - 2.3% and AA, respectively). Non-U.S. government-backed fixed maturity investments 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 to the respective curve 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. Corporate Level 2 - At March 31, 2018 , the Company’s corporate fixed maturity investments principally consisted of U.S. and international corporations and had a weighted average effective yield of 4.2% and a weighted average credit quality of BBB ( December 31, 2017 - 3.8% and BBB, respectively). 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. Agency mortgage-backed Level 2 - At March 31, 2018 , the Company’s agency mortgage-backed fixed maturity investments included agency residential mortgage-backed securities with a weighted average effective yield of 3.3% , a weighted average credit quality of AA and a weighted average life of 7.3 years ( December 31, 2017 - 3.0% , AA and 6.4 years, respectively). The Company’s agency mortgage-backed fixed maturity 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. Non-agency mortgage-backed Level 2 - The Company’s non-agency mortgage-backed fixed maturity investments include non-agency prime residential mortgage-backed and non-agency Alt-A fixed maturity investments. At March 31, 2018 , the Company’s non-agency prime residential mortgage-backed fixed maturity investments had a weighted average effective yield of 3.9% , a weighted average credit quality of non-investment grade, and a weighted average life of 5.3 years ( December 31, 2017 - 3.7% , BBB and 5.1 years, respectively). The Company’s non-agency Alt-A fixed maturity investments held at March 31, 2018 had a weighted average effective yield of 3.8% , a weighted average credit quality of non-investment grade and a weighted average life of 6.2 years ( December 31, 2017 - 3.7% , non-investment grade and 6.2 years, respectively). 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. Commercial mortgage-backed Level 2 - At March 31, 2018 , the Company’s commercial mortgage-backed fixed maturity investments had a weighted average effective yield of 3.3% , a weighted average credit quality of AAA, and a weighted average life of 4.7 years ( December 31, 2017 - 2.9% , AAA and 4.5 years, respectively). 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 discount the expected cash flows for each security held in this sector using a spread adjusted benchmark yield based on the characteristics of the security. Asset-backed Level 2 - At March 31, 2018 , the Company’s asset-backed fixed maturity investments had a weighted average effective yield of 3.5% , a weighted average credit quality of AAA and a weighted average life of 3.2 years ( December 31, 2017 - 2.8% , AAA and 3.0 years, respectively). The underlying collateral for the Company’s asset-backed fixed maturity investments primarily consists of bank loans, student loans, credit card receivables, auto loans and other receivables. 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 value of the securities held in this sector. Short Term Investments Level 2 - At March 31, 2018 , the Company’s short term investments had a weighted average effective yield of 1.7% and a weighted average credit quality of AAA ( December 31, 2017 - 1.4% and AAA, respectively). The fair value of the Company’s portfolio of short term investments is generally determined using amortized cost which approximates fair value and, in certain cases, in a manner similar to the Company’s fixed maturity investments noted above. Equity Investments, Classified as Trading Level 1 - The fair value of the Company’s portfolio of equity investments, classified as trading is primarily priced by pricing services, reflecting the closing price quoted for the final trading day of the period. When pricing these securities, the pricing services utilize daily data from many real time market sources, including applicable securities exchanges. All data sources are regularly reviewed for accuracy to attempt to ensure the most reliable price source was used for each security. Other investments Catastrophe bonds Level 2 - The Company’s other investments include investments in catastrophe bonds which are recorded at fair value based on broker or underwriter bid indications. Other assets and liabilities Derivatives Level 1 and Level 2 - Other assets and liabilities include certain derivatives entered into by the Company. The fair value of these transactions includes certain exchange traded futures contracts which are considered Level 1, and foreign currency contracts and certain credit derivatives, determined using standard industry valuation models and considered Level 2, as the inputs to the valuation model are based on observable market inputs. For credit derivatives, these inputs include credit spreads, credit ratings of the underlying referenced security, the risk free rate and the contract term. For foreign currency contracts, these inputs include spot rates and interest rate curves. Level 3 Assets and Liabilities Measured at Fair Value Below is a summary of quantitative information regarding the significant observable and unobservable inputs (Level 3) used in determining the fair value of assets and liabilities measured at fair value on a recurring basis: At March 31, 2018 Fair Value (Level 3) Valuation Technique Unobservable (U) and Observable (O) Inputs Low High Weighted Average or Actual Other assets and (liabilities) Assumed and ceded (re)insurance contracts $ 893 Internal valuation model Bond price (O) $ 101.46 $ 112.05 $ 107.31 Liquidity discount (U) n/a n/a 1.3 % Assumed and ceded (re)insurance contracts (3,673 ) Internal valuation model Net undiscounted cash flows (U) n/a n/a $ (4,706 ) Expected loss ratio (U) n/a n/a 20.4 % Net acquisition expense ratio (O) n/a n/a 13.7 % Contract period (O) 2.0 years 4.7 years 4.1 years Discount rate (U) n/a n/a 2.4 % Total other assets and (liabilities) $ (2,780 ) Below is a reconciliation of the beginning and ending balances, for the periods shown, of assets and liabilities measured at fair value on a recurring basis using Level 3 inputs. Interest and dividend income are included in net investment income and are excluded from the reconciliation. Other assets and (liabilities) Balance - January 1, 2018 $ (2,952 ) Total realized and unrealized gains Included in other (loss) income 206 Purchases (34 ) Balance - March 31, 2018 $ (2,780 ) Other assets and (liabilities) Balance - January 1, 2017 $ (13,004 ) Total realized and unrealized gains Included in other (losses) income 1,071 Purchases (202 ) Balance - March 31, 2017 $ (12,135 ) Other assets and liabilities Assumed and ceded (re)insurance contracts Level 3 - At March 31, 2018 , the Company had a $0.9 million net asset related to an assumed reinsurance contract accounted for at fair value, with the fair value obtained through the use of an internal valuation model. The inputs to the internal valuation model are principally based on indicative pricing obtained from independent brokers and pricing vendors for similarly structured marketable securities. The most significant unobservable inputs include prices for similar marketable securities and a liquidity premium. The Company considers the prices for similar securities to be unobservable, as there is little, if any market activity for these similar assets. In addition, the Company has estimated a liquidity premium that would be required if the Company attempted to effectively exit its position by executing a short sale of these securities. Generally, an increase in the prices for similar marketable securities or a decrease in the liquidity premium would result in an increase in the expected profit and ultimate fair value of this assumed reinsurance contract. Level 3 - At March 31, 2018 , the Company had a $3.7 million net liability related to assumed and ceded (re)insurance contracts accounted for at fair value, with the fair value obtained through the use of an internal valuation model. The inputs to the internal valuation model are principally based on proprietary data as observable market inputs are generally not available. The most significant unobservable inputs include the assumed and ceded expected net cash flows related to the contracts, including the expected premium, acquisition expenses and losses; the expected loss ratio and the relevant discount rate used to present value the net cash flows. The contract period and acquisition expense ratio are considered an observable input as each is defined in the contract. The negative acquisition expense ratio used to determine the fair value of the contracts at March 31, 2018 is the result of override commissions on the contracts being higher than the gross acquisition expenses. Generally, an increase in the net expected cash flows and expected term of the contract and a decrease in the discount rate, expected loss ratio or acquisition expense ratio, would result in an increase in the expected profit and ultimate fair value of these assumed and ceded (re)insurance contracts. Financial Instruments Disclosed, But Not Carried, at Fair Value The Company uses various financial instruments in the normal course of its business. The Company’s insurance contracts are excluded from the fair value of financial instruments accounting guidance, unless the Company elects the fair value option, and therefore, are not included in the amounts discussed herein. The carrying values of cash and cash equivalents, accrued investment income, receivables for investments sold, certain other assets, payables for investments purchased, certain other liabilities, and other financial instruments not included herein approximated their fair values. Debt Included on the Company’s consolidated balance sheet at March 31, 2018 were debt obligations of $990.0 million ( December 31, 2017 - $989.6 million ). At March 31, 2018 , the fair value of the Company’s debt obligations was $993.9 million ( December 31, 2017 – $1.0 billion ). The fair value of the Company’s debt obligations is determined using indicative market pricing obtained from third-party service providers, which the Company considers Level 2 in the fair value hierarchy. There have been no changes during the period in the Company’s valuation technique used to determine the fair value of the Company’s debt obligations. The Fair Value Option for Financial Assets and Financial Liabilities The Company has elected to account for certain financial assets and financial liabilities at fair value using the guidance under FASB ASC Topic Financial Instruments as the Company believes it represents the most meaningful measurement basis for these assets and liabilities. Below is a summary of the balances the Company has elected to account for at fair value: March 31, December 31, Other investments $ 692,652 $ 594,793 Other assets $ 2,533 $ 2,542 Other liabilities $ 5,313 $ 5,494 Included in net investment income for the three months ended March 31, 2018 were net unrealized gains of $1.5 million related to the changes in fair value of other investments ( 2017 – gains of $6.9 million ). Included in other income for the three months ended March 31, 2018 were net unrealized gains of $Nil related to the changes in the fair value of other assets and liabilities ( 2017 - $Nil ). Measuring the Fair Value of Other Investments Using Net Asset Valuations The table below shows the Company’s portfolio of other investments measured using net asset valuations as a practical expedient: At March 31, 2018 Fair Value Unfunded Redemption Frequency Redemption Redemption Private equity partnerships $ 190,067 $ 416,135 See below See below See below Senior secured bank loan funds 13,771 25,297 See below See below See below Hedge funds 12,280 — See below See below See below Total other investments measured using net asset valuations $ 216,118 $ 441,432 Private equity partnerships – The Company’s investments in private equity partnerships included alternative asset limited partnerships (or similar corporate structures) that invest in certain private equity asset classes, including U.S. and global leveraged buyouts, mezzanine investments, distressed securities, real estate, and oil, gas and power. The Company generally has no right to redeem its interest in any of these private equity partnerships in advance of dissolution of the applicable private equity partnership. Instead, the nature of these investments is that distributions are received by the Company in connection with the liquidation of the underlying assets of the respective private equity partnership. It is estimated that the majority of the underlying assets of the limited partnerships would liquidate over 7 to 10 years from inception of the respective limited partnership. Senior secured bank loan funds – At March 31, 2018 , the Company had $13.8 million invested in closed end funds which invest primarily in loans. The Company has no right to redeem its investment in these funds. It is estimated that the majority of the underlying assets in these closed end funds would begin to liquidate over 4 to 5 years from inception of the applicable fund. Hedge funds – The Company invests in hedge funds that pursue multiple strategies. At March 31, 2018 , the Company had $12.3 million of investments in hedge funds that pursue multiple strategies. This included an investment of $11.8 million in a fund primarily focused on global credit opportunities which is redeemable at the option of the shareholder. The remainder of the Company’s hedge fund investments consisted of so called “side pocket” investments which are not redeemable at the option of the shareholder.

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2018
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Reinsurance	REINSURANCE The Company purchases reinsurance and other protection to manage its risk portfolio and to reduce its exposure to large losses. The Company currently has in place contracts that provide for recovery of a portion of certain claims and claim expenses, generally in excess of various retentions or on a proportional basis. In addition to loss recoveries, certain of the Company’s ceded reinsurance contracts provide for payments of additional premiums, for reinstatement premiums and for lost no-claims bonuses, which are incurred when losses are ceded to the respective reinsurance contracts. The Company remains liable to the extent that any reinsurer fails to meet its obligations. The following table sets forth the effect of reinsurance and retrocessional activity on premiums written and earned and on net claims and claim expenses incurred: Three months ended March 31, March 31, Premiums written Direct $ 85,167 $ 73,408 Assumed 1,074,485 848,682 Ceded (496,608 ) (377,954 ) Net premiums written $ 663,044 $ 544,136 Premiums earned Direct $ 70,032 $ 58,168 Assumed 605,483 498,999 Ceded (235,233 ) (191,122 ) Net premiums earned $ 440,282 $ 366,045 Claims and claim expenses Gross claims and claim expenses incurred $ 225,742 $ 251,804 Claims and claim expenses recovered (54,039 ) (58,723 ) Net claims and claim expenses incurred $ 171,703 $ 193,081 At March 31, 2018 , the Company’s reinsurance recoverable balance was $1.6 billion ( 2017 - $1.6 billion ). Of this amount, 52.2% is fully collateralized by our reinsurers, 46.8% is recoverable from reinsurers rated A- or higher by major rating agencies and 1.0% is recoverable from reinsurers rated lower than A- by major rating agencies ( December 31, 2017 - 54.5% , 44.5% and 1.0% , respectively). The reinsurers with the three largest balances accounted for 9.3% , 8.1% and 6.7% , respectively, of the Company’s reinsurance recoverable balance at March 31, 2018 ( December 31, 2017 - 10.4% , 7.5% and 7.3% , respectively). The valuation allowance recorded against reinsurance recoverable was $7.8 million at March 31, 2018 ( December 31, 2017 - $7.0 million ). The three largest company-specific components of the valuation allowance represented 16.1% , 15.2% and 14.2% , respectively, of the Company’s total valuation allowance at March 31, 2018 ( December 31, 2017 - 11.1% , 9.2% and 8.4% , respectively).

Reserve for Claims and Claim Ex

Reserve for Claims and Claim Expenses	3 Months Ended
	Mar. 31, 2018
Insurance Loss Reserves [Abstract]
Reserve for Claims and Claim Expenses	RESERVE FOR CLAIMS AND CLAIM EXPENSES The Company believes the most significant accounting judgment made by management is its estimate of claims and claim expense reserves. Claims and claim expense reserves represent estimates, including actuarial and statistical projections at a given point in time, of the ultimate settlement and administration costs for unpaid claims and claim expenses arising from the insurance and reinsurance contracts the Company sells. The Company establishes its claims and claim expense reserves by taking claims reported to the Company by insureds and ceding companies, but which have not yet been paid (“case reserves”), adding estimates for the anticipated cost of claims incurred but not yet reported to the Company, or incurred but not enough reported to the Company (collectively referred to as “IBNR”) and, if deemed necessary, adding costs for additional case reserves which represent the Company’s estimates for claims related to specific contracts previously reported to the Company which it believes may not be adequately estimated by the client as of that date, or adequately covered in the application of IBNR. The following table summarizes the Company’s claims and claim expense reserves by segment, allocated between case reserves, additional case reserves and IBNR: At March 31, 2018 Case Reserves Additional Case Reserves IBNR Total Property $ 701,202 $ 850,498 $ 687,209 $ 2,238,909 Casualty and Specialty 740,809 118,380 1,801,361 2,660,550 Other 4,999 — 8,269 13,268 Total $ 1,447,010 $ 968,878 $ 2,496,839 $ 4,912,727 At December 31, 2017 Property $ 696,285 $ 896,522 $ 893,583 $ 2,486,390 Casualty and Specialty 689,962 124,923 1,760,607 2,575,492 Other 6,605 — 11,921 18,526 Total $ 1,392,852 $ 1,021,445 $ 2,666,111 $ 5,080,408 Activity in the liability for unpaid claims and claim expenses is summarized as follows: Three months ended March 31, 2018 2017 Net reserves as of January 1 $ 3,493,778 $ 2,568,730 Net incurred related to: Current year 203,038 164,075 Prior years (31,335 ) 29,006 Total net incurred 171,703 193,081 Net paid related to: Current year 9,050 7,729 Prior years 328,129 147,500 Total net paid 337,179 155,229 Foreign exchange 12,104 2,287 Net reserves as of March 31 3,340,406 2,608,869 Reinsurance recoverable as of March 31 1,572,321 325,819 Gross reserves as of March 31 $ 4,912,727 $ 2,934,688 Prior Year Development of the Reserve for Net Claims and Claim Expenses The Company’s estimates of claims and claim expense reserves are not precise in that, among other things, they are based on predictions of future developments and estimates of future trends and other variable factors. Some, but not all, of the Company’s reserves are further subject to the uncertainty inherent in actuarial methodologies and estimates. Because a reserve estimate is simply an insurer’s estimate at a point in time of its ultimate liability, and because there are numerous factors that affect reserves and claims payments that cannot be determined with certainty in advance, the Company’s ultimate payments will vary, perhaps materially, from its estimates of reserves. If the Company determines in a subsequent period that adjustments to its previously established reserves are appropriate, such adjustments are recorded in the period in which they are identified. On a net basis, the Company’s cumulative favorable or unfavorable development is generally reduced by offsetting changes in its reinsurance recoverables, as well as changes to loss related premiums such as reinstatement premiums and redeemable noncontrolling interest for changes in claims and claim expenses that impact DaVinciRe, all of which generally move in the opposite direction to changes in the Company’s ultimate claims and claim expenses. The following table details the Company’s prior year development by segment of its liability for unpaid claims and claim expenses: Three months ended March 31, 2018 2017 (Favorable) adverse development (Favorable) adverse development Property $ (27,562 ) $ (928 ) Casualty and Specialty (3,791 ) 30,262 Other 18 (328 ) Total favorable development of prior accident years net claims and claim expenses $ (31,335 ) $ 29,006 Changes to prior year estimated claims reserves increased the Company’s net income by $31.3 million during the three months ended March 31, 2018 , ( 2017 - decreased the Company’s net income by $29.0 million ), excluding the consideration of changes in reinstatement, adjustment or other premium changes, profit commissions, redeemable noncontrolling interest - DaVinciRe and income tax. Property Segment The following tables detail the development of the Company’s liability for unpaid claims and claim expenses for its Property segment, allocated between large and small catastrophe net claims and claim expenses and attritional net claims and claim expenses, included in the other line item: Three months ended March 31, 2018 (Favorable) adverse development Catastrophe net claims and claim expenses Large catastrophe events 2017 Catastrophe Events $ (27,109 ) Other (4,258 ) Total large catastrophe events (31,367 ) Small catastrophe events Other 3,805 Total small catastrophe events 3,805 Total catastrophe net claims and claim expenses (27,562 ) Total net favorable development of prior accident years net claims and claim expenses $ (27,562 ) The net favorable development of prior accident years net claims and claim expenses within the Company’s Property segment in the three months ended March 31, 2018 of $27.6 million was comprised of net favorable development of $31.4 million related to large catastrophe events and net adverse development of $3.8 million related to small catastrophe events. Included in net favorable development of prior accident years net claims and claim expenses from large events was $27.1 million of net decreases in the estimated ultimate losses associated with Hurricanes Harvey, Irma and Maria, the Mexico City Earthquake and the wildfires in California during the fourth quarter of 2017 (collectively, the “ 2017 Catastrophe Events ”). In addition, the Company’s Property segment experienced net favorable development of $0.5 million associated with a number of other large and small catastrophe events. Three months ended March 31, 2017 (Favorable) adverse development Catastrophe net claims and claim expenses Large catastrophe events Other $ 2,586 Total large catastrophe events 2,586 Small catastrophe events Fort McMurray Wildfire (2016) (5,850 ) Other 2,336 Total small catastrophe events (3,514 ) Total catastrophe net claims and claim expenses (928 ) Total net favorable development of prior accident years net claims and claim expenses $ (928 ) The net favorable development of prior accident years net claims and claim expenses within the Company’s Property segment in the three months ended March 31, 2017 of $0.9 million was principally comprised of net favorable development of $3.5 million associated with small catastrophe events related to a reduction in the estimated ultimate losses associated with the 2016 Fort McMurray Wildfire of $5.9 million , partially offset by net adverse development associated with a number of other large and small events. In addition, the Company experienced net favorable development of $2.6 million from large catastrophe events due principally to a decrease in the estimated ultimate losses associated with a number of other small catastrophe events. Casualty and Specialty Segment The following table details the development of the Company’s liability for unpaid claims and claim expenses for its Casualty and Specialty segment: Three months ended March 31, 2018 2017 (Favorable) adverse development (Favorable) adverse development Actuarial methods $ (3,791 ) $ (5,999 ) Ogden Rate change — 33,481 Actuarial assumption changes — 2,780 Total adverse (favorable) development of prior accident years net claims and claim expenses $ (3,791 ) $ 30,262 The net favorable development of prior accident years net claims and claim expenses within the Company’s Casualty and Specialty segment in the three months ended March 31, 2018 of $3.8 million was driven by reported losses generally coming in lower than expected on attritional net claims and claim expenses across a number of lines of business. The net adverse development of prior accident years net claims and claim expenses within the Company’s Casualty and Specialty segment in the three months ended March 31, 2017 of $30.3 million was driven by $33.5 million of adverse development associated with the change in the discount rate used to calculate lump sum awards in U.K. bodily injury cases (the “Ogden Rate”), from 2.5% , to minus 0.75% . Notwithstanding the impact of the Ogden Rate change, the Company experienced $6.0 million of net favorable development related to reported losses coming in lower than expected on attritional net claims and claim expenses across a number of lines of business, partially offset by $2.8 million of adverse development associated with actuarial assumption changes.

Debt and Credit Facilities

Debt and Credit Facilities	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt and Credit Facilities	DEBT AND CREDIT FACILITIES Except as noted below, there have been no material changes to the Company’s debt obligations and credit facilities as described in its Form 10-K for the year ended December 31, 2017 . Debt Obligations A summary of the Company’s debt obligations on its consolidated balance sheets is set forth below: March 31, 2018 December 31, 2017 Fair Value Carrying Value Fair Value Carrying Value 3.450% Senior Notes due 2027 $ 283,281 $ 295,425 $ 294,654 $ 295,303 3.700% Senior Notes due 2025 294,864 297,409 302,781 297,318 5.75% Senior Notes due 2020 262,188 249,353 263,750 249,272 4.750% Senior Notes due 2025 (DaVinciRe) (1) 153,546 147,808 157,050 147,730 $ 993,879 $ 989,995 $ 1,018,235 $ 989,623 (1) RenaissanceRe owns a noncontrolling economic interest in its joint venture DaVinciRe. Because RenaissanceRe controls a majority of DaVinciRe’s outstanding voting rights, the consolidated financial statements of DaVinciRe are included in the consolidated financial statements of RenaissanceRe. However, RenaissanceRe does not guarantee or provide credit support for DaVinciRe and RenaissanceRe’s financial exposure to DaVinciRe is limited to its investment in DaVinciRe’s shares and counterparty credit risk arising from reinsurance transactions. Credit Facilities The outstanding amounts issued or drawn under each of the Company’s significant credit facilities is set forth below: At March 31, 2018 Issued or Drawn RenaissanceRe Revolving Credit Facility $ — Uncommitted Standby Letter of Credit Facility with Wells Fargo 101,679 Bilateral Letter of Credit Facility with Citibank Europe 186,709 Funds at Lloyd’s Letter of Credit Facilities Renaissance Reinsurance FAL Facility 180,000 Total credit facilities in U.S. dollars $ 468,388 Funds at Lloyd’s Letter of Credit Facilities Specialty Risks FAL Facility £ 10,000 Total credit facilities in British Pounds £ 10,000 National Australia Bank Limited Standby Letter of Credit Agreement Effective as of March 23, 2018, the Company terminated the Standby Letter of Credit Agreement, dated as of May 19, 2015, among National Australia Bank Limited (“NAB”) and Renaissance Reinsurance, RenaissanceRe Specialty Risks Ltd., DaVinci and Platinum Underwriters Bermuda, Ltd. (collectively, the “NAB Facility Applicants”) (the “NAB Standby Letter of Credit Agreement”). The NAB Standby Letter of Credit Agreement provided for a secured, uncommitted facility under which letters of credit were issued from time to time for the respective accounts of the NAB Facility Applicants in multiple currencies. RenaissanceRe unconditionally guaranteed the payment obligations of the NAB Facility Applicants, other than DaVinci.

Noncontrolling Interests

Noncontrolling Interests	3 Months Ended
	Mar. 31, 2018
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest [Abstract]
Noncontrolling Interests	NONCONTROLLING INTERESTS A summary of the Company’s redeemable noncontrolling interests on its consolidated balance sheets is set forth below: March 31, December 31, 2017 Redeemable noncontrolling interest - DaVinciRe $ 1,032,543 $ 1,011,659 Redeemable noncontrolling interest - Medici 392,821 284,847 Redeemable noncontrolling interests $ 1,425,364 $ 1,296,506 A summary of the Company’s redeemable noncontrolling interests on its consolidated statements of operations is set forth below: Three months ended March 31, March 31, Redeemable noncontrolling interest - DaVinciRe $ 20,953 $ 31,909 Redeemable noncontrolling interest - Medici 8,946 2,418 Net income attributable to redeemable noncontrolling interests $ 29,899 $ 34,327 Redeemable Noncontrolling Interest – DaVinciRe In October 2001, the Company formed DaVinciRe and DaVinci with other equity investors. RenaissanceRe owns a noncontrolling economic interest in DaVinciRe; however, because RenaissanceRe controls a majority of DaVinciRe’s outstanding voting rights, the consolidated financial statements of DaVinciRe are included in the consolidated financial statements of the Company. The portion of DaVinciRe’s earnings owned by third parties is recorded in the consolidated statements of operations as net income attributable to redeemable noncontrolling interests. The Company’s noncontrolling economic ownership in DaVinciRe was 22.1% at March 31, 2018 ( December 31, 2017 - 22.1% ). DaVinciRe shareholders are party to a shareholders agreement which provides DaVinciRe shareholders, excluding RenaissanceRe, with certain redemption rights that enable each shareholder to notify DaVinciRe of such shareholder’s desire for DaVinciRe to repurchase up to half of such shareholder’s initial aggregate number of shares held, subject to certain limitations, such as limiting the aggregate of all share repurchase requests to 25% of DaVinciRe’s capital in any given year and satisfying all applicable regulatory requirements. If total shareholder requests exceed 25% of DaVinciRe’s capital, the number of shares repurchased will be reduced among the requesting shareholders pro-rata, based on the amounts desired to be repurchased. Shareholders desiring to have DaVinci repurchase their shares must notify DaVinciRe before March 1 of each year. The repurchase price will be based on GAAP book value as of the end of the year in which the shareholder notice is given, and the repurchase will be effective as of January 1 of the following year. The repurchase price is generally subject to a true-up for potential development on outstanding loss reserves after settlement of all claims relating to the applicable years. 2017 During January 2017, DaVinciRe redeemed $75.0 million of its outstanding shares from certain existing DaVinciRe shareholders, including RenaissanceRe. In connection with the redemption, DaVinciRe retained a $7.5 million holdback. In addition, RenaissanceRe sold an aggregate of $24.0 million of its shares in DaVinciRe to an existing shareholder and a new shareholder. The Company’s noncontrolling economic ownership in DaVinciRe subsequent to these transactions was 22.6% , effective January 1, 2017. During July 2017, RenaissanceRe purchased $12.0 million of DaVinciRe’s outstanding shares from an existing third-party shareholder. The Company’s noncontrolling economic ownership in DaVinciRe subsequent to these transactions was 23.5% , effective July 1, 2017. Effective October 1, 2017, DaVinciRe completed an equity capital raise of $248.6 million from third-party investors and RenaissanceRe. In addition, RenaissanceRe sold an aggregate of $49.7 million of its shares in DaVinciRe to third-party investors. The Company’s noncontrolling economic ownership in DaVinciRe subsequent to these transactions was 22.1% , effective October 1, 2017. The Company expects its noncontrolling economic ownership in DaVinciRe to fluctuate over time. The activity in redeemable noncontrolling interest – DaVinciRe is detailed in the table below: Three months ended March 31, March 31, Beginning balance $ 1,011,659 $ 994,458 Redemption of shares from redeemable noncontrolling interest, net of adjustments (69 ) (63,642 ) Sale of shares to redeemable noncontrolling interests — 23,921 Net income attributable to redeemable noncontrolling interest 20,953 31,909 Ending balance $ 1,032,543 $ 986,646 Redeemable Noncontrolling Interest - RenaissanceRe Medici Fund Ltd. (“Medici”) Medici is an exempted company incorporated under the laws of Bermuda and its objective is to seek to invest substantially all of its assets in various insurance-based investment instruments that have returns primarily tied to property catastrophe risk. RenaissanceRe owns a noncontrolling economic interest in Medici; however, because RenaissanceRe controls all of Medici’s outstanding voting rights, the financial statements of Medici are included in the consolidated financial statements of the Company. The portion of Medici’s earnings owned by third parties is recorded in the consolidated statements of operations as net income attributable to redeemable noncontrolling interests. Any shareholder may redeem all or any portion of its shares as of the last day of any calendar month, upon at least 30 calendar days’ prior irrevocable written notice to Medici. 2017 During 2017, third-party investors subscribed for $149.2 million and redeemed $48.0 million of the participating, non-voting common shares of Medici. As a result of these net subscriptions, the Company’s noncontrolling economic ownership in Medici was 26.8% , effective at December 31, 2017. 2018 During the three months ended March 31, 2018 , third-party investors subscribed for $99.7 million and redeemed $0.7 million of the participating, non-voting common shares of Medici. As a result of these net subscriptions, the Company’s noncontrolling economic ownership in Medici was 17.1% at March 31, 2018 . The Company expects its noncontrolling economic ownership in Medici to fluctuate over time. The activity in redeemable noncontrolling interest – Medici is detailed in the table below: Three months ended March 31, March 31, Beginning balance $ 284,847 $ 181,136 Redemption of shares from redeemable noncontrolling interest, net of adjustments (711 ) (10,625 ) Sale of shares to redeemable noncontrolling interests 99,739 28,416 Net income attributable to redeemable noncontrolling interest 8,946 2,418 Ending balance $ 392,821 $ 201,345

Variable Interest Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	VARIABLE INTEREST ENTITIES Upsilon RFO Effective January 1, 2013, the Company formed and launched Upsilon RFO, a managed joint venture, and a Bermuda domiciled SPI, to provide additional capacity to the worldwide aggregate and per-occurrence retrocessional property catastrophe excess of loss market. The shareholders (other than the Class A shareholder) participate in substantially all of the profits or losses of Upsilon RFO while their shares remain outstanding. The shareholders (other than the Class A shareholder) indemnify Upsilon RFO against losses relating to insurance risk and therefore these shares have been accounted for as prospective reinsurance under FASB ASC Topic Financial Services - Insurance . Upsilon RFO is considered a VIE as it has insufficient equity capital to finance its activities without additional financial support. The Company is the primary beneficiary of Upsilon RFO as it has the power over the activities that most significantly impact the economic performance of Upsilon RFO and has the obligation to absorb expected losses and the right to receive expected benefits that could be significant to Upsilon RFO, in accordance with the accounting guidance. As a result, the Company consolidates Upsilon RFO and all significant inter-company transactions have been eliminated. Other than its equity investment in Upsilon RFO, the Company has not provided financial or other support to Upsilon RFO that it was not contractually required to provide. 2017 During 2017, Upsilon RFO returned $84.3 million of capital to its investors, including $33.0 million to the Company. In addition, during 2017, $180.6 million of Upsilon RFO non-voting preference shares were issued to existing investors therein, including $27.2 million to the Company, and an existing third-party investor purchased $7.5 million of Upsilon RFO non-voting preference shares from the Company. At December 31, 2017, the Company’s participation in the risks assumed by Upsilon RFO was 20.8% . 2018 During the three months ended March 31, 2018 , $600.5 million of Upsilon RFO non-voting preference shares were issued to existing investors, including $75.0 million to the Company. This amount was received by the Company prior to December 31, 2017 and was included in other liabilities on the Company’s consolidated balance sheet at December 31, 2017, and also included in other operating cash flows on the Company’s consolidated statements of cash flows for the year ended December 31, 2017. During the three months ended March 31, 2018, in connection with the issuance of the non-voting preference shares of Upsilon RFO, other liabilities were reduced by this amount, and reinsurance balances payable were increased by an offsetting amount, with corresponding impacts to other operating cash flows and the change in reinsurance balances payable on the Company consolidated statements of cash flows for the three months ended March 31, 2018. At March 31, 2018 , the Company’s participation in the risks assumed by Upsilon RFO was 14.1% . At March 31, 2018 , the Company’s consolidated balance sheet included total assets and total liabilities of Upsilon RFO of $1.4 billion and $1.4 billion , respectively ( December 31, 2017 - $1.2 billion and $1.2 billion , respectively). See “Note 16 . Subsequent Events” for additional information related to Upsilon RFO’s non-voting preference shares subsequent to March 31, 2018 . Mona Lisa Re Ltd. (“Mona Lisa Re”) On March 14, 2013, Mona Lisa Re was licensed as a Bermuda domiciled special purpose insurer to provide reinsurance capacity to subsidiaries of RenaissanceRe, namely Renaissance Reinsurance and DaVinci, through reinsurance agreements which will be collateralized and funded by Mona Lisa Re through the issuance of one or more series of principal-at-risk variable rate notes to third-party investors. Upon issuance of a series of notes by Mona Lisa Re, all of the proceeds from the issuance were deposited into collateral accounts, separated by series, to fund any potential obligation under the reinsurance agreements entered into with Renaissance Reinsurance and/or DaVinci underlying such series of notes. The outstanding principal amount of each series of notes generally will be returned to holders of such notes upon the expiration of the risk period underlying such notes, unless an event occurs which causes a loss under the applicable series of notes, in which case the amount returned will be reduced by such noteholder’s pro rata share of such loss, as specified in the applicable governing documents of such notes. In addition, holders of such notes are generally entitled to interest payments, payable quarterly, as determined by the applicable governing documents of each series of notes. The Company concluded that Mona Lisa Re meets the definition of a VIE as it does not have sufficient equity capital to finance its activities. The Company evaluated its relationship with Mona Lisa Re and concluded it does not have a variable interest in Mona Lisa Re. As a result, the financial position and results of operations of Mona Lisa Re are not consolidated by the Company. The Company has not provided financial or other support to Mona Lisa Re that it was not contractually required to provide. At March 31, 2018 , the total assets and total liabilities of Mona Lisa Re were $25.6 million and $25.6 million , respectively ( December 31, 2017 - $25.9 million and $25.9 million , respectively). The only transactions related to Mona Lisa Re that are recorded in the Company’s consolidated financial statements are the ceded reinsurance agreements entered into by Renaissance Reinsurance and DaVinci which are accounted for as prospective reinsurance under FASB ASC Topic Financial Services - Insurance. Renaissance Reinsurance and DaVinci have together entered into ceded reinsurance contracts with Mona Lisa Re with gross premiums ceded of $0.2 million and $0.2 million , respectively, during the three months ended March 31, 2018 ( 2017 - $0.1 million and $37 thousand , respectively). In addition, Renaissance Reinsurance and DaVinci recognized ceded premiums earned related to the ceded reinsurance contracts with Mona Lisa Re of $0.1 million and $0.1 million , respectively, during the three months ended March 31, 2018 ( 2017 - $1.8 million and $1.3 million , respectively). Fibonacci Re Effective November 7, 2016 , Fibonacci Re, a Bermuda-domiciled SPI, was formed to provide collateralized capacity to Renaissance Reinsurance and its affiliates. Upon issuance of a series of notes by Fibonacci Re, all of the proceeds from the issuance are deposited into collateral accounts, separated by series, to fund any potential obligation under the reinsurance agreements entered into with Renaissance Reinsurance underlying such series of notes. The outstanding principal amount of each series of notes generally is expected to be returned to holders of such notes upon the expiration of the risk period underlying such notes, unless an event occurs which causes a loss under the applicable series of notes, in which case the amount returned is expected to be reduced by such noteholder’s pro rata share of such loss, as specified in the applicable governing documents of such notes. In addition, holders of such notes are generally entitled to interest payments, payable quarterly, as determined by the applicable governing documents of each series of notes. RUM receives an origination and structuring fee in connection with the formation and operation of Fibonacci Re. The Company concluded that Fibonacci Re meets the definition of a VIE as it does not have sufficient equity capital to finance its activities. The Company evaluated its relationship with Fibonacci Re and concluded it is not the primary beneficiary of Fibonacci Re as it does not have power over the activities that most significantly impact the economic performance of Fibonacci Re. As a result, the Company does not consolidate the financial position or results of operations of Fibonacci Re. The only transactions related to Fibonacci Re that will be recorded in the Company’s consolidated financial statements will be the ceded reinsurance agreements entered into by Renaissance Reinsurance that are accounted for as prospective reinsurance under FASB ASC Topic Financial Services - Insurance, and the fair value of the participating notes owned by the Company. Other than its investment in the participating notes of Fibonacci Re, the Company has not provided financial or other support to Fibonacci Re that it was not contractually required to provide. The fair value of the Company’s investment in the participating notes of Fibonacci Re is included in other investments. Net of third-party investors, the fair value of the Company’s investment in Fibonacci Re was $11.1 million at March 31, 2018 ( December 31, 2017 - $14.1 million ). Renaissance Reinsurance entered into ceded reinsurance contracts with Fibonacci Re with ceded premiums of $4.1 million and ceded premiums earned of $1.2 million during the three months ended March 31, 2018 ( 2017 - $7.4 million and $1.8 million , respectively). Langhorne Effective December 22, 2017, the Company and Reinsurance Group of America, Incorporated closed Langhorne, an initiative to source third party capital to support reinsurers targeting large in-force life and annuity blocks. In connection with Langhorne, as of March 31, 2018 the Company has invested $1.3 million in Langhorne Holdings ( December 31, 2017 - $0.6 million ), a company that owns and manages certain reinsurance entities within Langhorne. In addition, as of March 31, 2018 the Company has invested $0.1 million in Langhorne Partners ( December 31, 2017 - $Nil ), the general partner for Langhorne and the entity which manages the third-party investors investing into Langhorne Holdings. The Company concluded that Langhorne Holdings meets the definition of a VIE as the voting rights are not proportional with the obligations to absorb losses and rights to receive residual returns. The Company evaluated its relationship with Langhorne Holdings and concluded it is not the primary beneficiary of Langhorne Holdings, as it does not have power over the activities that most significantly impact the economic performance of Langhorne Holdings. As a result, the Company does not consolidate the financial position or results of operations of Langhorne Holdings. The Company separately evaluated Langhorne Partners and concluded that it was not a VIE. The Company accounts for its investments in Langhorne Holdings and Langhorne Partners under the equity method of accounting, one quarter in arrears. The Company anticipates that its investment in Langhorne will increase, perhaps materially, as in-force life and annuity blocks of businesses are written. Other than its current and committed future equity investment in Langhorne, the Company has not provided financial or other support to Langhorne that it was not contractually required to provide.

Shareholders' Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Shareholders' Equity	SHAREHOLDERS’ EQUITY Dividends The Board of Directors of RenaissanceRe declared a dividend of $0.33 per common share, payable on March 29, 2018 to common shareholders of record on March 15, 2018 and, accordingly, RenaissanceRe paid the dividend on March 29, 2018. The Board of Directors approved the payment of quarterly dividends on the Series C 6.08% Preference Shares and Series E 5.375% Preference Shares to preference shareholders of record in the amounts and on the quarterly record dates and dividend payment dates set forth in the prospectus supplement and Certificate of Designation for the applicable series of preference shares, unless and until further action is taken by the Board of Directors. The dividend payment dates for the preference shares will be the first day of March, June, September and December of each year (or if this date is not a business day, on the business day immediately following this date). The record dates for the preference share dividends are one day prior to the dividend payment dates. The amount of the dividend on the Series C 6.08% Preference Shares is an amount per share equal to 6.08% of the liquidation preference per annum (the equivalent to $1.52 per share per annum, or $0.38 per share per quarter). The amount of the dividend on the Series E 5.375% Preference Shares is an amount per share equal to 5.375% of the liquidation preference per annum (the equivalent to $1.34375 per share per annum, or $0.3359375 per share per quarter). During the three months ended March 31, 2018 , the Company paid $5.6 million in preference share dividends ( 2017 - $5.6 million ) and $13.2 million in common share dividends ( 2017 - $13.0 million ). Share Repurchases The Company’s share repurchase program may be effected from time to time, depending on market conditions and other factors, through open market purchases and privately negotiated transactions. On November 10, 2017 , RenaissanceRe’s Board of Directors approved a renewal of its authorized share repurchase program for an aggregate amount of up to $500.0 million . Unless terminated earlier by RenaissanceRe’s Board of Directors, the program will expire when the Company has repurchased the full value of the common shares authorized. The Company’s decision to repurchase common shares will depend on, among other matters, the market price of the common shares and the capital requirements of the Company. During the three months ended March 31, 2018 , the Company’s did not repurchase any of its common shares. At March 31, 2018 , $500.0 million remained available for repurchase under the share repurchase program.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE The following table sets forth the computation of basic and diluted earnings per common share: Three months ended (common shares in thousands) March 31, March 31, Numerator: Net income available to RenaissanceRe common shareholders $ 56,713 $ 92,352 Amount allocated to participating common shareholders (1) (546 ) (907 ) Net income allocated to RenaissanceRe common shareholders $ 56,167 $ 91,445 Denominator: Denominator for basic income per RenaissanceRe common share - weighted average common shares 39,552 40,408 Per common share equivalents of employee stock options and restricted shares 47 215 Denominator for diluted income per RenaissanceRe common share - adjusted weighted average common shares and assumed conversions 39,599 40,623 Net income available to RenaissanceRe common shareholders per common share – basic $ 1.42 $ 2.26 Net income available to RenaissanceRe common shareholders per common share – diluted $ 1.42 $ 2.25 (1) Represents earnings attributable to holders of unvested restricted shares issued pursuant to the Company’s 2001 Stock Incentive Plan, 2010 Performance-Based Equity Incentive Plan, 2016 Long-Term Incentive Plan and to the Company’s non-employee directors.

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2018
Segment Reporting, Measurement Disclosures [Abstract]
Segment Reporting	SEGMENT REPORTING The Company’s reportable segments are defined as follows: (1) Property, which is comprised of catastrophe and other property reinsurance and insurance written on behalf of the Company’s operating subsidiaries and certain joint ventures managed by the Company’s ventures unit, and (2) Casualty and Specialty, which is comprised of casualty and specialty reinsurance and insurance written on behalf of the Company’s operating subsidiaries and certain joint ventures managed by the Company’s ventures unit. In addition to its reportable segments, the Company has an Other category, which primarily includes its strategic investments, investments unit, corporate expenses, capital servicing costs, noncontrolling interests and the remnants of its former Bermuda-based insurance operations. The Company’s Property segment is managed by the Chief Underwriting Officer - Property and the Casualty and Specialty segment is managed by the Chief Underwriting Officer - Casualty and Specialty, each of whom operate under the direction of the Company’s Group Chief Underwriting Officer, who in turn reports to the Company’s President and Chief Executive Officer. The Company does not manage its assets by segment; accordingly, net investment income and total assets are not allocated to the segments. A summary of the significant components of the Company’s revenues and expenses by segment is as follows: Three months ended March 31, 2018 Property Casualty and Specialty Other Total Gross premiums written $ 706,968 $ 452,684 $ — $ 1,159,652 Net premiums written $ 354,077 $ 308,967 $ — $ 663,044 Net premiums earned $ 225,049 $ 215,233 $ — $ 440,282 Net claims and claim expenses incurred 30,607 141,078 18 171,703 Acquisition expenses 40,721 56,990 — 97,711 Operational expenses 26,546 14,593 133 41,272 Underwriting income (loss) $ 127,175 $ 2,572 $ (151 ) 129,596 Net investment income 56,476 56,476 Net foreign exchange gains 3,757 3,757 Equity in earnings of other ventures 857 857 Other loss (1,242 ) (1,242 ) Net realized and unrealized losses on investments (82,144 ) (82,144 ) Corporate expenses (6,733 ) (6,733 ) Interest expense (11,767 ) (11,767 ) Income before taxes 88,800 Income tax benefit 3,407 3,407 Net income attributable to redeemable noncontrolling interests (29,899 ) (29,899 ) Dividends on preference shares (5,595 ) (5,595 ) Net income available to RenaissanceRe common shareholders $ 56,713 Net claims and claim expenses incurred – current accident year $ 58,169 $ 144,869 $ — $ 203,038 Net claims and claim expenses incurred – prior accident years (27,562 ) (3,791 ) 18 (31,335 ) Net claims and claim expenses incurred – total $ 30,607 $ 141,078 $ 18 $ 171,703 Net claims and claim expense ratio – current accident year 25.8 % 67.3 % 46.1 % Net claims and claim expense ratio – prior accident years (12.2 )% (1.8 )% (7.1 )% Net claims and claim expense ratio – calendar year 13.6 % 65.5 % 39.0 % Underwriting expense ratio 29.9 % 33.3 % 31.6 % Combined ratio 43.5 % 98.8 % 70.6 % Three months ended March 31, 2017 Property Casualty and Specialty Other Total Gross premiums written $ 520,529 $ 401,561 $ — $ 922,090 Net premiums written $ 289,871 $ 254,265 $ — $ 544,136 Net premiums earned $ 186,988 $ 179,059 $ (2 ) $ 366,045 Net claims and claim expenses incurred 38,838 154,571 (328 ) 193,081 Acquisition expenses 29,103 54,179 — 83,282 Operational expenses 27,665 19,607 11 47,283 Underwriting income (loss) $ 91,382 $ (49,298 ) $ 315 42,399 Net investment income 54,325 54,325 Net foreign exchange gains 8,165 8,165 Equity in losses of other ventures (1,507 ) (1,507 ) Other income 1,665 1,665 Net realized and unrealized gains on investments 43,373 43,373 Corporate expenses (5,286 ) (5,286 ) Interest expense (10,526 ) (10,526 ) Income before taxes and noncontrolling interests 132,608 Income tax expense (334 ) (334 ) Net income attributable to noncontrolling interests (34,327 ) (34,327 ) Dividends on preference shares (5,595 ) (5,595 ) Net income available to RenaissanceRe common shareholders $ 92,352 Net claims and claim expenses incurred – current accident year $ 39,766 $ 124,309 $ — $ 164,075 Net claims and claim expenses incurred – prior accident years (928 ) 30,262 (328 ) 29,006 Net claims and claim expenses incurred – total $ 38,838 $ 154,571 $ (328 ) $ 193,081 Net claims and claim expense ratio – current accident year 21.3 % 69.4 % 44.8 % Net claims and claim expense ratio – prior accident years (0.5 )% 16.9 % 7.9 % Net claims and claim expense ratio – calendar year 20.8 % 86.3 % 52.7 % Underwriting expense ratio 30.3 % 41.2 % 35.7 % Combined ratio 51.1 % 127.5 % 88.4 %

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2018
Summary of Derivative Instruments [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS From time to time, the Company may enter into derivative instruments such as futures, options, swaps, forward contracts and other derivative contracts primarily to manage its foreign currency exposure, obtain exposure to a particular financial market, for yield enhancement, or for trading and speculation. The Company’s derivative instruments can be exchange traded or over-the-counter, with over-the-counter derivatives generally traded under International Swaps and Derivatives Association master agreements, which establish the terms of the transactions entered into with the Company’s derivative counterparties. In the event a party becomes insolvent or otherwise defaults on its obligations, a master agreement generally permits the non-defaulting party to accelerate and terminate all outstanding transactions and net the transactions’ marked-to-market values so that a single sum in a single currency will be owed by, or owed to, the non-defaulting party. Effectively, this contractual close-out netting reduces credit exposure from gross to net exposure. Where the Company has entered into master netting agreements with counterparties, or the Company has the legal and contractual right to offset positions, the derivative positions are generally netted by counterparty and are reported accordingly in other assets and other liabilities. The tables below show the gross and net amounts of recognized derivative assets and liabilities at fair value, including the location on the consolidated balance sheets of the Company’s principal derivative instruments: Derivative Assets At March 31, 2018 Gross Amounts of Recognized Assets Gross Amounts Offset in the Balance Sheet Net Amounts of Assets Presented in the Balance Sheet Balance Sheet Location Collateral Net Amount Interest rate futures $ 175 157 $ 18 Other assets $ — $ 18 Interest rate swaps 357 — 357 Other assets — 357 Foreign currency forward contracts (1) 7,070 175 6,895 Other assets — 6,895 Foreign currency forward contracts (2) 79 78 1 Other assets — 1 Credit default swaps 1,600 — 1,600 Other assets — 1,600 Total $ 9,281 $ 410 $ 8,871 $ — $ 8,871 Derivative Liabilities At March 31, 2018 Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Balance Sheet Net Amounts of Liabilities Presented in the Balance Sheet Balance Sheet Location Collateral Pledged Net Amount Interest rate futures $ 404 157 $ 247 Other liabilities $ 247 $ — Interest rate swaps 53 — 53 Other liabilities 53 — Foreign currency forward contracts (1) 479 — 479 Other liabilities — 479 Foreign currency forward contracts (2) 643 78 565 Other liabilities — 565 Credit default swaps 13 — 13 Other liabilities 13 — Total $ 1,592 $ 235 $ 1,357 $ 313 $ 1,044 (1) Contracts used to manage foreign currency risks in underwriting and non-investment operations. (2) Contracts used to manage foreign currency risks in investment operations. Derivative Assets At December 31, 2017 Gross Amounts of Recognized Assets Gross Amounts Offset in the Balance Sheet Net Amounts of Assets Presented in the Balance Sheet Balance Sheet Location Collateral Net Amount Interest rate futures $ 684 524 $ 160 Other assets $ — $ 160 Interest rate swaps 424 — 424 Other assets — 424 Foreign currency forward contracts (1) 3,865 358 3,507 Other assets — 3,507 Foreign currency forward contracts (2) 39 11 28 Other assets — 28 Credit default swaps 1,518 — 1,518 Other assets — 1,518 Total $ 6,530 $ 893 $ 5,637 $ — $ 5,637 Derivative Liabilities At December 31, 2017 Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Balance Sheet Net Amounts of Liabilities Presented in the Balance Sheet Balance Sheet Location Collateral Pledged Net Amount Interest rate futures $ 729 524 $ 205 Other liabilities $ 205 $ — Foreign currency forward contracts (1) 670 — 670 Other liabilities — 670 Foreign currency forward contracts (2) 115 11 104 Other liabilities — 104 Credit default swaps 22 — 22 Other liabilities 22 — Total $ 1,536 $ 535 $ 1,001 $ 227 $ 774 (1) Contracts used to manage foreign currency risks in underwriting and non-investment operations. (2) Contracts used to manage foreign currency risks in investment operations. Refer to “Note 3 . Investments” for information on reverse repurchase agreements. The location and amount of the gain (loss) recognized in the Company’s consolidated statements of operations related to its principal derivative instruments are shown in the following table: Location of gain (loss) recognized on derivatives Amount of gain (loss) recognized on derivatives Three months ended March 31, 2018 2017 Interest rate futures Net realized and unrealized (losses) gains on investments $ (2,337 ) $ (158 ) Interest rate swaps Net realized and unrealized (losses) gains on investments (106 ) — Foreign currency forward contracts (1) Net foreign exchange gains 6,743 1,060 Foreign currency forward contracts (2) Net foreign exchange gains (691 ) (633 ) Credit default swaps Net realized and unrealized (losses) gains on investments (1,921 ) 102 Total $ 1,688 $ 371 (1) Contracts used to manage foreign currency risks in underwriting and non-investment operations. (2) Contracts used to manage foreign currency risks in investment operations. The Company is not aware of the existence of any credit-risk related contingent features that it believes would be triggered in its derivative instruments that are in a net liability position at March 31, 2018 . Interest Rate Derivatives The Company uses interest rate futures and swaps within its portfolio of fixed maturity investments to manage its exposure to interest rate risk, which may result in increasing or decreasing its exposure to this risk. Interest Rate Futures The fair value of interest rate futures is determined using exchange traded prices. At March 31, 2018 , the Company had $1.5 billion of notional long positions and $812.7 million of notional short positions of primarily Eurodollar, U.S. treasury and non-U.S. dollar futures contracts ( December 31, 2017 - $1.5 billion and $801.1 million , respectively). Interest Rate Swaps The fair value of interest rate swaps is determined using the relevant exchange traded price where available or a discounted cash flow model based on the terms of the contract and inputs, including, where applicable, observable yield curves. At March 31, 2018 , the Company had $22.9 million of notional positions paying a fixed rate and $6.9 million receiving a fixed rate denominated in U.S. dollars ( December 31, 2017 - $40.3 million and $Nil , respectively). Foreign Currency Derivatives The Company’s functional currency is the U.S. dollar. The Company writes a portion of its business in currencies other than U.S. dollars and may, from time to time, experience foreign exchange gains and losses in the Company’s consolidated financial statements. All changes in exchange rates, with the exception of non-monetary assets and liabilities, are recognized in the Company’s consolidated statements of operations. Underwriting Operations Related Foreign Currency Contracts The Company’s foreign currency policy with regard to its underwriting operations is generally to hold foreign currency assets, including cash, investments and receivables that approximate the foreign currency liabilities, including claims and claim expense reserves and reinsurance balances payable. When necessary, the Company may use foreign currency forward and option contracts to minimize the effect of fluctuating foreign currencies on the value of non-U.S. dollar denominated assets and liabilities associated with its underwriting operations. The fair value of the Company’s underwriting operations related foreign currency contracts is determined using indicative pricing obtained from counterparties or broker quotes. At March 31, 2018 , the Company had outstanding underwriting related foreign currency contracts of $218.6 million in notional long positions and $25.4 million in notional short positions, denominated in U.S. dollars ( December 31, 2017 - $215.4 million and $44.2 million , respectively). Investment Portfolio Related Foreign Currency Forward Contracts The Company’s investment operations are exposed to currency fluctuations through its investments in non-U.S. dollar fixed maturity investments, short term investments and other investments. From time to time, the Company may employ foreign currency forward contracts in its investment portfolio to either assume foreign currency risk or to economically hedge its exposure to currency fluctuations from these investments. The fair value of the Company’s investment portfolio related foreign currency forward contracts is determined using an interpolated rate based on closing forward market rates. At March 31, 2018 , the Company had outstanding investment portfolio related foreign currency contracts of $66.4 million in notional long positions and $40.5 million in notional short positions, denominated in U.S. dollars ( December 31, 2017 - $16.6 million and $5.1 million , respectively). Credit Derivatives The Company’s exposure to credit risk is primarily due to its fixed maturity investments, short term investments, premiums receivable and reinsurance recoverable. From time to time, the Company may purchase credit derivatives to hedge its exposures in the insurance industry, and to assist in managing the credit risk associated with ceded reinsurance. The Company also employs credit derivatives in its investment portfolio to either assume credit risk or hedge its credit exposure. The fair value of credit derivatives is determined using industry valuation models, broker bid indications or internal pricing valuation techniques. The fair value of these credit derivatives can change based on a variety of factors including changes in credit spreads, default rates and recovery rates, the correlation of credit risk between the referenced credit and the counterparty, and market rate inputs such as interest rates. At March 31, 2018 , the Company had outstanding credit derivatives of $1.0 million in notional positions to hedge credit risk and $41.1 million in notional positions to assume credit risk, denominated in U.S. dollars ( December 31, 2017 - $1.0 million and $18.8 million , respectively).

Commitments, Contingencies and

Commitments, Contingencies and Other Items	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Other Items	COMMITMENTS, CONTINGENCIES AND OTHER ITEMS There are no material changes from the commitments and contingencies previously disclosed in the Company’s Form 10-K for the year ended December 31, 2017 . Legal Proceedings The Company and its subsidiaries are subject to lawsuits and regulatory actions in the normal course of business that do not arise from or directly relate to claims on reinsurance treaties or contracts or direct surplus lines insurance policies. In the Company’s industry, business litigation may involve allegations of underwriting or claims-handling errors or misconduct, disputes relating to the scope of, or compliance with, the terms of delegated underwriting agreements, employment claims, regulatory actions or disputes arising from the Company’s business ventures. The Company’s operating subsidiaries are subject to claims litigation involving, among other things, disputed interpretations of policy coverages. Generally, the Company’s direct surplus lines insurance operations are subject to greater frequency and diversity of claims and claims-related litigation than its reinsurance operations and, in some jurisdictions, may be subject to direct actions by allegedly injured persons or entities seeking damages from policyholders. These lawsuits, involving or arising out of claims on policies issued by the Company’s subsidiaries which are typical to the insurance industry in general and in the normal course of business, are considered in its loss and loss expense reserves. In addition, the Company may from time to time engage in litigation or arbitration related to its claims for payment in respect of ceded reinsurance, including disputes that challenge the Company’s ability to enforce its underwriting intent. Such matters could result, directly or indirectly, in providers of protection not meeting their obligations to the Company or not doing so on a timely basis. The Company may also be subject to other disputes from time to time, relating to operational or other matters distinct from insurance or reinsurance claims. Any litigation or arbitration, or regulatory process, contains an element of uncertainty, and the value of an exposure or a gain contingency related to a dispute is difficult to estimate accordingly. Currently, the Company believes that no individual litigation or arbitration to which it is presently a party is likely to have a material adverse effect on its financial condition, business or operations.

Condensed Consolidating Financi

Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries	3 Months Ended
	Mar. 31, 2018
Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries [Abstract]
Condensed Consolidating Financial Information Provided in Connection with Outstanding Debt of Subsidiaries	CONDENSED CONSOLIDATING FINANCIAL INFORMATION PROVIDED IN CONNECTION WITH OUTSTANDING DEBT OF SUBSIDIARIES The following tables present condensed consolidating balance sheets at March 31, 2018 and December 31, 2017 , condensed consolidating statements of operations and condensed consolidating statements of comprehensive income for the three months ended March 31, 2018 and 2017 , and condensed consolidating statements of cash flows for the three months ended March 31, 2018 . Each of RenRe North America Holdings Inc. and RenaissanceRe Finance, Inc. is a 100% owned subsidiary of RenaissanceRe. On June 1, 2017, the notes issued by Platinum Underwriters Finance, Inc. (“Platinum Finance”) matured and the Company repaid the aggregate principal amount plus applicable accrued interest in full. Platinum Finance was subsequently dissolved on November 30, 2017. Prior to the liquidation of Platinum Finance, it was a 100% owned subsidiary of RenaissanceRe. For additional information related to the terms of the Company’s outstanding debt securities, see “Note 9. Debt and Credit Facilities” in the “Notes to Consolidated Financial Statements” in the Company’s Form 10-K for the year ended December 31, 2017 and “Note 7 . Debt and Credit Facilities” in the “Notes to Consolidated Financial Statements” included herein. Condensed Consolidating Balance Sheet at March 31, 2018 RenaissanceRe RenRe North RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Assets Total investments $ 70,641 $ 112,716 $ 22,433 $ 10,015,914 $ — $ 10,221,704 Cash and cash equivalents 8,150 97 1,175 638,551 — 647,973 Investments in subsidiaries 4,090,065 53,476 1,137,922 — (5,281,463 ) — Due from subsidiaries and affiliates 137,639 91,891 — — (229,530 ) — Premiums receivable — — — 1,684,630 — 1,684,630 Prepaid reinsurance premiums — — — 794,921 — 794,921 Reinsurance recoverable — — — 1,572,321 — 1,572,321 Accrued investment income 16 223 46 42,784 — 43,069 Deferred acquisition costs — — — 477,010 — 477,010 Receivable for investments sold 48 — 6 111,377 — 111,431 Other assets 439,667 21,340 433,056 82,133 (848,625 ) 127,571 Goodwill and other intangible assets 123,728 — — 117,844 — 241,572 Total assets $ 4,869,954 $ 279,743 $ 1,594,638 $ 15,537,485 $ (6,359,618 ) $ 15,922,202 Liabilities, Noncontrolling Interests and Shareholders’ Equity Liabilities Reserve for claims and claim expenses $ — $ — $ — $ 4,912,727 $ — $ 4,912,727 Unearned premiums — — — 1,961,746 — 1,961,746 Debt 417,000 — 842,188 147,807 (417,000 ) 989,995 Amounts due to subsidiaries and affiliates 9,639 61 106,900 — (116,600 ) — Reinsurance balances payable — — — 1,758,948 — 1,758,948 Payable for investments purchased — — — 306,664 — 306,664 Other liabilities 7,062 793 9,457 119,676 (6,483 ) 130,505 Total liabilities 433,701 854 958,545 9,207,568 (540,083 ) 10,060,585 Redeemable noncontrolling interests — — — 1,425,364 — 1,425,364 Shareholders’ Equity Total shareholders’ equity 4,436,253 278,889 636,093 4,904,553 (5,819,535 ) 4,436,253 Total liabilities, noncontrolling interests and shareholders’ equity $ 4,869,954 $ 279,743 $ 1,594,638 $ 15,537,485 $ (6,359,618 ) $ 15,922,202 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor, Subsidiary Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Balance Sheet at December 31, 2017 RenaissanceRe Holdings Ltd. (Parent Guarantor) RenRe North RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other RenaissanceRe Holdings Ltd. Subsidiaries and Eliminations (Non-guarantor Subsidiaries) (1) Consolidating Adjustments (2) RenaissanceRe Consolidated Assets Total investments $ 225,266 $ 129,732 $ 31,255 $ 9,117,186 $ — $ 9,503,439 Cash and cash equivalents 14,656 139 1,469 1,345,328 — 1,361,592 Investments in subsidiaries 4,105,760 36,140 1,141,733 — (5,283,633 ) — Due from subsidiaries and affiliates 4,602 91,891 — — (96,493 ) — Premiums receivable — — — 1,304,622 — 1,304,622 Prepaid reinsurance premiums — — — 533,546 — 533,546 Reinsurance recoverable — — — 1,586,630 — 1,586,630 Accrued investment income 405 428 82 41,320 — 42,235 Deferred acquisition costs — — — 426,551 — 426,551 Receivable for investments sold 135 51 8 102,951 — 103,145 Other assets 433,468 21,342 430,481 76,703 (840,768 ) 121,226 Goodwill and other intangible assets 124,960 — — 118,185 — 243,145 Total assets $ 4,909,252 $ 279,723 $ 1,605,028 $ 14,653,022 $ (6,220,894 ) $ 15,226,131 Liabilities, Redeemable Noncontrolling Interest and Shareholders’ Equity Liabilities Reserve for claims and claim expenses $ — $ — $ — $ 5,080,408 $ — $ 5,080,408 Unearned premiums — — — 1,477,609 — 1,477,609 Debt 417,000 — 841,892 147,731 (417,000 ) 989,623 Amounts due to subsidiaries and affiliates 82,579 54 92,794 — (175,427 ) — Reinsurance balances payable — — — 989,090 — 989,090 Payable for investments purchased — — — 208,749 — 208,749 Other liabilities 18,298 1,053 14,117 764,432 (5,129 ) 792,771 Total liabilities 517,877 1,107 948,803 8,668,019 (597,556 ) 9,538,250 Redeemable noncontrolling interests — — — 1,296,506 — 1,296,506 Shareholders’ Equity Total shareholders’ equity 4,391,375 278,616 656,225 4,688,497 (5,623,338 ) 4,391,375 Total liabilities, redeemable noncontrolling interest and shareholders’ equity $ 4,909,252 $ 279,723 $ 1,605,028 $ 14,653,022 $ (6,220,894 ) $ 15,226,131 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Statement of Operations for RenaissanceRe RenRe North RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Revenues Net premiums earned $ — $ — $ — $ 440,282 $ — $ 440,282 Net investment income 6,035 513 1,234 56,305 (7,611 ) 56,476 Net foreign exchange (losses) gains (3 ) — — 3,760 — 3,757 Equity in earnings (losses) of other ventures — — 1,211 (354 ) — 857 Other loss — — — (1,242 ) — (1,242 ) Net realized and unrealized losses on investments (661 ) (1,286 ) (259 ) (79,938 ) — (82,144 ) Total revenues 5,371 (773 ) 2,186 418,813 (7,611 ) 417,986 Expenses Net claims and claim expenses incurred — — — 171,703 — 171,703 Acquisition expenses — — — 97,711 — 97,711 Operational expenses 1,313 10 11,070 37,933 (9,054 ) 41,272 Corporate expenses 3,684 — — 3,049 — 6,733 Interest expense 1,108 — 9,252 2,515 (1,108 ) 11,767 Total expenses 6,105 10 20,322 312,911 (10,162 ) 329,186 (Loss) income before equity in net income (loss) of subsidiaries and taxes (734 ) (783 ) (18,136 ) 105,902 2,551 88,800 Equity in net income (loss) of subsidiaries 62,426 834 (3,813 ) — (59,447 ) — Income (loss) before taxes 61,692 51 (21,949 ) 105,902 (56,896 ) 88,800 Income tax benefit 616 221 1,815 755 — 3,407 Net income (loss) 62,308 272 (20,134 ) 106,657 (56,896 ) 92,207 Net loss attributable to redeemable noncontrolling interests — — — (29,899 ) — (29,899 ) Net income (loss) attributable to RenaissanceRe 62,308 272 (20,134 ) 76,758 (56,896 ) 62,308 Dividends on preference shares (5,595 ) — — — — (5,595 ) Net income (loss) available (attributable) to RenaissanceRe common shareholders $ 56,713 $ 272 $ (20,134 ) $ 76,758 $ (56,896 ) $ 56,713 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor, Subsidiary Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Statement of Comprehensive Income (Loss) for the three months ended March 31, 2018 RenaissanceRe RenRe North RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Comprehensive income (loss) Net income (loss) $ 62,308 $ 272 $ (20,134 ) $ 106,657 $ (56,896 ) $ 92,207 Change in net unrealized gains on investments — — — (30 ) — (30 ) Comprehensive income (loss) 62,308 272 (20,134 ) 106,627 (56,896 ) 92,177 Net income attributable to redeemable noncontrolling interests — — — (29,899 ) — (29,899 ) Comprehensive income attributable to noncontrolling interests — — — (29,899 ) — (29,899 ) Comprehensive income (loss) attributable to RenaissanceRe $ 62,308 $ 272 $ (20,134 ) $ 76,728 $ (56,896 ) $ 62,278 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor, Subsidiary Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Statement of Operations for the three months ended March 31, 2017 RenaissanceRe RenRe North Inc. Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Revenues Net premiums earned $ — $ — $ — $ — $ 366,045 $ — $ 366,045 Net investment income 5,457 426 841 269 53,583 (6,251 ) 54,325 Net foreign exchange gains — — — — 8,165 — 8,165 Equity in losses of other ventures — — — (752 ) (755 ) — (1,507 ) Other (loss) income (1 ) — — — 1,666 — 1,665 Net realized and unrealized gains (losses) on investments 53 2,921 4,725 (26 ) 35,700 — 43,373 Total revenues 5,509 3,347 5,566 (509 ) 464,404 (6,251 ) 472,066 Expenses Net claims and claim expenses incurred — — — — 193,081 — 193,081 Acquisition expenses — — — — 83,282 — 83,282 Operational expenses 3,298 24 50 7,979 42,058 (6,126 ) 47,283 Corporate expenses 5,208 — — — 78 — 5,286 Interest expense 140 — 1,476 6,542 2,508 (140 ) 10,526 Total expenses 8,646 24 1,526 14,521 321,007 (6,266 ) 339,458 (Loss) income before equity in net income of subsidiaries and taxes (3,137 ) 3,323 4,040 (15,030 ) 143,397 15 132,608 Equity in net income of subsidiaries 101,353 1,086 9,843 16,498 — (128,780 ) — Income before taxes 98,216 4,409 13,883 1,468 143,397 (128,765 ) 132,608 Income tax (expense) benefit (269 ) (1,098 ) (1,308 ) 3,072 (731 ) — (334 ) Net income 97,947 3,311 12,575 4,540 142,666 (128,765 ) 132,274 Net income attributable to redeemable noncontrolling interests — — — — (34,327 ) — (34,327 ) Net income attributable to RenaissanceRe 97,947 3,311 12,575 4,540 108,339 (128,765 ) 97,947 Dividends on preference shares (5,595 ) — — — — — (5,595 ) Net income available to RenaissanceRe common shareholders $ 92,352 $ 3,311 $ 12,575 $ 4,540 $ 108,339 $ (128,765 ) $ 92,352 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Statement of Comprehensive Income for the three months ended March 31, 2017 RenaissanceRe RenRe North Inc. Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Comprehensive income Net income $ 97,947 $ 3,311 $ 12,575 $ 4,540 $ 142,666 $ (128,765 ) $ 132,274 Change in net unrealized gains on investments — — — — (1,491 ) — (1,491 ) Comprehensive income 97,947 3,311 12,575 4,540 141,175 (128,765 ) 130,783 Net income attributable to redeemable noncontrolling interests — — — — (34,327 ) — (34,327 ) Comprehensive income attributable to redeemable noncontrolling interests — — — — (34,327 ) — (34,327 ) Comprehensive income available to RenaissanceRe $ 97,947 $ 3,311 $ 12,575 $ 4,540 $ 106,848 $ (128,765 ) $ 96,456 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Statement of Cash Flows for the three months ended March 31, 2018 RenaissanceRe RenRe North Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other RenaissanceRe Consolidated Cash flows (used in) provided by operating activities Net cash (used in) provided by operating activities $ (6,875 ) $ 659 $ (23,449 ) $ (7,684 ) $ (37,349 ) Cash flows provided by (used in) investing activities Proceeds from sales and maturities of fixed maturity investments trading 119,542 42,793 27,672 2,128,852 2,318,859 Purchases of fixed maturity investments trading (20,216 ) (22,956 ) (12,698 ) (2,256,591 ) (2,312,461 ) Net (purchases) sales of equity investments trading — (21 ) — 158 137 Net sales (purchases) of short term investments 54,728 (4,024 ) (5,925 ) (639,420 ) (594,641 ) Net sales of other investments — — — (98,639 ) (98,639 ) Dividends and return of capital from subsidiaries 177,250 — — (177,250 ) — Contributions to subsidiaries (150,205 ) (16,500 ) — 166,705 — Due to (from) subsidiary (154,877 ) 7 14,106 140,764 — Net cash provided by (used in) investing activities 26,222 (701 ) — 23,155 (753,395 ) (704,719 ) Cash flows (used in) provided by financing activities Dividends paid – RenaissanceRe common shares (13,224 ) — — — — (13,224 ) Dividends paid – preference shares (5,595 ) — — — — (5,595 ) Net third party redeemable noncontrolling interest share transactions — — — 52,759 52,759 Taxes paid on withholding shares (7,034 ) — — — — (7,034 ) Net cash (used in) provided by financing activities (25,853 ) — — — 52,759 26,906 Effect of exchange rate changes on foreign currency cash — — — — 1,543 1,543 Net decrease in cash and cash equivalents (6,506 ) (42 ) — (294 ) (706,777 ) (713,619 ) Cash and cash equivalents, beginning of period 14,656 139 1,469 1,345,328 1,361,592 Cash and cash equivalents, end of period $ 8,150 $ 97 $ — $ 1,175 $ 638,551 $ 647,973 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. Condensed Consolidating Statement of Cash Flows for the three months ended March 31, 2017 RenaissanceRe RenRe North Inc. Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other RenaissanceRe Holdings Ltd. Subsidiaries and Eliminations (Non-guarantor Subsidiaries) (1) RenaissanceRe Consolidated Cash flows (used in) provided by operating activities Net cash (used in) provided by operating activities $ (12,358 ) $ (8,594 ) $ 5,188 $ (17,914 ) $ 234,717 $ 201,039 Cash flows provided by (used in) investing activities Proceeds from sales and maturities of fixed maturity investments trading 38,449 12,473 36,397 15,449 2,579,618 2,682,386 Purchases of fixed maturity investments trading (63,417 ) (12,438 ) (36,790 ) — (2,894,479 ) (3,007,124 ) Net (purchases) sales of equity investments trading — (74 ) (2,181 ) — 16,002 13,747 Net sales (purchases) of short term investments 269,585 (590 ) (5,087 ) (3,374 ) (14,841 ) 245,693 Net sales of other investments — — — — 36,402 36,402 Return of investment from investment in other ventures — — — — 20,000 20,000 Dividends and return of capital from subsidiaries 65,180 9,175 — 9,175 (83,530 ) — Contributions to subsidiaries (162,550 ) — — (9,175 ) 171,725 — Due (from) to subsidiaries (28,130 ) 50 (34 ) 2,522 25,592 — Net cash provided by (used in) investing activities 119,117 8,596 (7,695 ) 14,597 (143,511 ) (8,896 ) Cash flows used in financing activities Dividends paid – RenaissanceRe common shares (13,027 ) — — — — (13,027 ) Dividends paid – preference shares (5,595 ) — — — — (5,595 ) RenaissanceRe common share repurchases (80,009 ) — — — — (80,009 ) Net third party redeemable noncontrolling interest share transactions — — — — (51,166 ) (51,166 ) Taxes paid on withholding shares (11,018 ) — — — — (11,018 ) Net cash used in financing activities (109,649 ) — — — (51,166 ) (160,815 ) Effect of exchange rate changes on foreign currency cash — — — — 1,602 1,602 Net (decrease) increase in cash and cash equivalents (2,890 ) 2 (2,507 ) (3,317 ) 41,642 32,930 Cash and cash equivalents, beginning of period 7,067 162 6,671 9,397 397,860 421,157 Cash and cash equivalents, end of period $ 4,177 $ 164 $ 4,164 $ 6,080 $ 439,502 $ 454,087 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS Effective April 1, 2018, Upsilon RFO issued $31.7 million of non-voting preference shares to investors, including $26.5 million to the Company. Effective April 1, 2018, the Company’s participation in the risks assumed by Upsilon RFO was 16.9% .

Significant Accounting Polici24

Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	BASIS OF PRESENTATION These consolidated financial statements have been prepared on the basis of accounting principles generally accepted in the United States (“GAAP”) for interim financial information and in conformity with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. In the opinion of management, these unaudited consolidated financial statements reflect all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation 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 from these statements. Certain comparative information has been reclassified to conform to the current presentation. Because of the seasonality of the Company’s business, the results of operations and cash flows for any interim period will not necessarily be indicative of the results of operations and cash flows for the full fiscal year or subsequent quarters.
Use of Estimates in Financial Statements	USE OF ESTIMATES IN FINANCIAL STATEMENTS The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported and disclosed amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from those estimates. The major estimates reflected in the Company’s consolidated financial statements include, but are not limited to, the reserve for claims and claim expenses; reinsurance recoverables, including allowances for reinsurance recoverables deemed uncollectible; estimates of written and earned premiums; fair value, including the fair value of investments, financial instruments and derivatives; impairment charges; and the Company’s deferred tax valuation allowance.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Adopted	RECENTLY ADOPTED ACCOUNTING PRONOUNCEMENTS Revenue from Contracts with Customers In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 provides comprehensive guidance on the recognition of revenue from customers arising from the transfer of goods and services. The core principle 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. ASU 2014-09 also provides guidance on accounting for certain contract costs and will also require new disclosures. ASU 2014-09 was to be effective for public business entities in annual and interim periods beginning after December 15, 2016, however in July 2015, the FASB decided to defer by one year the effective dates of ASU 2014-09, and as a result, ASU 2014-09 is effective for public business entities in annual and interim periods beginning after December 15, 2017. ASU 2014-09 notably excludes the accounting for insurance contracts, leases, financial instruments and guarantees. The Company’s implementation efforts primarily focused on other income and operational expenses on its consolidated statements of operations. The adoption of ASU 2014-09 did not have a material impact on the Company’s consolidated statements of operations and financial position. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-01”). ASU 2016-01 requires equity investments (except those accounted for under the equity method of accounting or those that result in the consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income, simplifies the impairment assessment of equity investments without readily determinable values by requiring a qualitative assessment to identify impairment, eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost, requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes, requires separate presentation in other comprehensive income of the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the organization has elected to measure the liabilities in accordance with the fair value option, requires the separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or the accompanying notes to the financial statements and clarifies that the reporting organization should evaluate the need for a valuation allowance on a deferred tax asset related to available for sale securities in combination with the organization’s other deferred tax assets. ASU 2016-01 is effective for public business entities in annual and interim periods beginning after December 15, 2017. The adoption of ASU 2016-01 did not have a material impact on the Company’s consolidated statements of operations and financial position. Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). ASU 2016-15 clarifies the classification of receipts and payments in the statement of cash flows. ASU 2016-15 provides guidance related to (1) settlement and payment of zero coupon debt instruments, (2) contingent consideration, (3) proceeds from settlement of insurance claims, (4) proceeds from settlement of corporate and bank owned life insurance policies, (5) distributions from equity method investees, (6) cash receipts from beneficial interests obtained by a transferor, and (7) general guidelines for cash receipts and payments that have more than one aspect of classification. ASU 2016-15 is effective for public business entities for annual periods beginning after December 15, 2017, and interim periods within those fiscal years. The adoption of ASU 2016-15 resulted in the reclassification of $20.0 million of cash inflows from cash flows provided by operating activities, to cash flows used in investing activities for the three months ended March 31, 2017. This amount related to a return of investment associated with the Company’s investment in Top Layer Reinsurance Ltd, recorded under the equity method of accounting. Improvements to Employee Share-Based Payment Accounting In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 was issued to simplify several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and the classification of taxes paid on the statements of cash flows. ASU 2016-09 became effective for the Company in annual and interim periods beginning after December 15, 2016. The cumulative effect of the adoption of ASU 2016-09 was a $2.2 million increase to opening retained earnings as of January 1, 2017. RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS NOT YET ADOPTED Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 requires lessees to recognize lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous guidance. ASU 2016-02 is effective for public business entities for annual and interim periods beginning after December 15, 2018. Early application is permitted. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position. Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 modifies the recognition of credit losses by replacing the incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU 2016-13 is applicable to financial assets such as loans, debt securities, trade receivables, off-balance sheet credit exposures, reinsurance receivables, and other financial assets that have the contractual right to receive cash. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectibility of the reported amount. The Company's invested assets are measured at fair value through net income, and therefore those invested assets would not be impacted by the adoption of ASU 2016-13. The Company has other financial assets, such as reinsurance recoverables, that could be impacted by the adoption of ASU 2016-13. ASU 2016-13 is effective for public business entities that are SEC filers for annual and interim periods beginning after December 15, 2019. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position. Intra-Entity Transfers of Assets Other Than Inventory In October 2016, the FASB issued ASU No. 2016-16, Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). ASU 2016-16 requires entities to recognize the income tax consequences of intra-entity transfers of assets other than inventory when the transfers occur; this is a change from current guidance which prohibits the recognition of current and deferred income taxes until the underlying assets have been sold to outside entities. ASU 2016-16 is effective for public business entities for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position. Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment (“ASU 2017-04”). Among other things, ASU 2017-04 requires the following: (1) the elimination of step two of the goodwill impairment test; entities will no longer utilize the implied fair value of their assets and liabilities for purposes of testing goodwill for impairment, (2) the quantitative portion of the goodwill impairment test will be performed by comparing the fair value of a reporting unit with its carrying amount; an impairment charge is to be recognized for the excess of carrying amount over fair value, but only to the extent of the amount of goodwill allocated to that reporting unit, and (3) foreign currency translation adjustments are not to be allocated to a reporting unit from an entity’s accumulated other comprehensive income; the reporting unit’s carrying amount should include only the currently translated balances of the assets and liabilities assigned to the reporting unit. ASU 2017-04 is effective for public business entities that are SEC filers for annual periods, or any interim goodwill impairment tests in annual periods, beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently evaluating the impact of this guidance; however, it is not expected to have a material impact on the Company’s consolidated statements of operations and financial position.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Schedule of Fair Value of Fixed Maturity Investments Trading	The following table summarizes the fair value of fixed maturity investments trading: March 31, December 31, U.S. treasuries $ 2,834,487 $ 3,168,763 Agencies 45,365 47,646 Municipal 506,470 509,802 Non-U.S. government (Sovereign debt) 303,056 287,660 Non-U.S. government-backed corporate 191,202 163,651 Corporate 2,147,578 2,063,459 Agency mortgage-backed 693,377 500,456 Non-agency mortgage-backed 302,638 300,331 Commercial mortgage-backed 197,126 202,062 Asset-backed 183,462 182,725 Total fixed maturity investments trading $ 7,404,761 $ 7,426,555
Schedule of Contractual Maturities of Fixed Maturity Investments	Contractual maturities of fixed maturity investments trading are described in the following table. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. March 31, 2018 Amortized Cost Fair Value Due in less than one year $ 496,788 $ 495,143 Due after one through five years 4,381,056 4,324,744 Due after five through ten years 1,073,453 1,064,575 Due after ten years 145,438 143,696 Mortgage-backed 1,189,730 1,193,141 Asset-backed 183,538 183,462 Total $ 7,470,003 $ 7,404,761
Schedule of Fair Value of Equity Investments Trading	The following table summarizes the fair value of equity investments trading: March 31, December 31, Financials $ 253,905 $ 253,543 Communications and technology 51,400 49,526 Industrial, utilities and energy 32,790 34,325 Consumer 23,886 24,779 Healthcare 21,042 21,364 Basic materials 4,439 4,717 Total $ 387,462 $ 388,254
Schedule of Net Investment Income	The components of net investment income are as follows: Three months ended March 31, March 31, Fixed maturity investments $ 45,643 $ 43,419 Short term investments 5,304 1,724 Equity investments 698 811 Other investments Private equity investments (434 ) 7,802 Other 8,023 4,072 Cash and cash equivalents 565 189 59,799 58,017 Investment expenses (3,323 ) (3,692 ) Net investment income $ 56,476 $ 54,325
Schedule of Net Realized and Unrealized (Losses) Gains On Investments	Net realized and unrealized (losses) gains on investments are as follows: Three months ended March 31, March 31, Gross realized gains $ 4,583 $ 11,461 Gross realized losses (25,853 ) (16,533 ) Net realized losses on fixed maturity investments (21,270 ) (5,072 ) Net unrealized (losses) gains on fixed maturity investments trading (55,372 ) 24,635 Net realized and unrealized losses on investments-related derivatives (4,364 ) (56 ) Net realized gains on equity investments trading sold during the period 234 20,915 Net unrealized (losses) gains on equity investments trading still held at reporting date (1,372 ) 2,951 Net realized and unrealized (losses) gains on equity investments trading (1,138 ) 23,866 Net realized and unrealized (losses) gains on investments $ (82,144 ) $ 43,373

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis	Below is a summary of the assets and liabilities that are measured at fair value on a recurring basis and also represents the carrying amount on the Company’s consolidated balance sheets: At March 31, 2018 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fixed maturity investments U.S. treasuries $ 2,834,487 $ 2,834,487 $ — $ — Agencies 45,365 — 45,365 — Municipal 506,470 — 506,470 — Non-U.S. government (Sovereign debt) 303,056 — 303,056 — Non-U.S. government-backed corporate 191,202 — 191,202 — Corporate 2,147,578 — 2,147,578 — Agency mortgage-backed 693,377 — 693,377 — Non-agency mortgage-backed 302,638 — 302,638 — Commercial mortgage-backed 197,126 — 197,126 — Asset-backed 183,462 — 183,462 — Total fixed maturity investments 7,404,761 2,834,487 4,570,274 — Short term investments 1,616,597 — 1,616,597 — Equity investments trading 387,462 387,462 — — Other investments Catastrophe bonds 476,534 — 476,534 — Private equity partnerships (1) 190,067 — — — Senior secured bank loan funds (1) 13,771 — — — Hedge funds (1) 12,280 — — — Total other investments 692,652 — 476,534 — Other assets and (liabilities) Assumed and ceded (re)insurance contracts (2) (2,780 ) — — (2,780 ) Derivatives (3) 7,514 (229 ) 7,743 — Total other assets and (liabilities) 4,734 (229 ) 7,743 (2,780 ) $ 10,106,206 $ 3,221,720 $ 6,671,148 $ (2,780 ) (1) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the consolidated balance sheet. (2) Included in assumed and ceded (re)insurance contracts at March 31, 2018 was $2.5 million and $5.3 million of other assets and other liabilities, respectively. (3) See “Note 13 . Derivative Instruments” for additional information related to the fair value by type of contract, of derivatives entered into by the Company. At December 31, 2017 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fixed maturity investments U.S. treasuries $ 3,168,763 $ 3,168,763 $ — $ — Agencies 47,646 — 47,646 — Municipal 509,802 — 509,802 — Non-U.S. government (Sovereign debt) 287,660 — 287,660 — Non-U.S. government-backed corporate 163,651 — 163,651 — Corporate 2,063,459 — 2,063,459 — Agency mortgage-backed 500,456 — 500,456 — Non-agency mortgage-backed 300,331 — 300,331 — Commercial mortgage-backed 202,062 — 202,062 — Asset-backed 182,725 — 182,725 — Total fixed maturity investments 7,426,555 3,168,763 4,257,792 — Short term investments 991,863 — 991,863 — Equity investments trading 388,254 388,254 — — Other investments Catastrophe bonds 380,475 — 380,475 — Private equity partnerships (1) 196,220 — — — Senior secured bank loan funds (1) 17,574 — — — Hedge funds (1) 524 — — — Total other investments 594,793 — 380,475 — Other assets and (liabilities) Assumed and ceded (re)insurance contracts (2) (2,952 ) — — (2,952 ) Derivatives (3) 4,636 (45 ) 4,681 — Total other assets and (liabilities) 1,684 (45 ) 4,681 (2,952 ) $ 9,403,149 $ 3,556,972 $ 5,634,811 $ (2,952 ) (1) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the consolidated balance sheet. (2) Included in assumed and ceded (re)insurance contracts at December 31, 2017 was $2.5 million and $5.5 million of other assets and other liabilities, respectively. (3) See “Note 13 . Derivative Instruments” for additional information related to the fair value by type of contract, of derivatives entered into by the Company.
Schedule Of Quantitative Information Used As Level 3 Inputs	Below is a summary of quantitative information regarding the significant observable and unobservable inputs (Level 3) used in determining the fair value of assets and liabilities measured at fair value on a recurring basis: At March 31, 2018 Fair Value (Level 3) Valuation Technique Unobservable (U) and Observable (O) Inputs Low High Weighted Average or Actual Other assets and (liabilities) Assumed and ceded (re)insurance contracts $ 893 Internal valuation model Bond price (O) $ 101.46 $ 112.05 $ 107.31 Liquidity discount (U) n/a n/a 1.3 % Assumed and ceded (re)insurance contracts (3,673 ) Internal valuation model Net undiscounted cash flows (U) n/a n/a $ (4,706 ) Expected loss ratio (U) n/a n/a 20.4 % Net acquisition expense ratio (O) n/a n/a 13.7 % Contract period (O) 2.0 years 4.7 years 4.1 years Discount rate (U) n/a n/a 2.4 % Total other assets and (liabilities) $ (2,780 )
Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Level 3 Inputs	Below is a reconciliation of the beginning and ending balances, for the periods shown, of assets and liabilities measured at fair value on a recurring basis using Level 3 inputs. Interest and dividend income are included in net investment income and are excluded from the reconciliation. Other assets and (liabilities) Balance - January 1, 2018 $ (2,952 ) Total realized and unrealized gains Included in other (loss) income 206 Purchases (34 ) Balance - March 31, 2018 $ (2,780 ) Other assets and (liabilities) Balance - January 1, 2017 $ (13,004 ) Total realized and unrealized gains Included in other (losses) income 1,071 Purchases (202 ) Balance - March 31, 2017 $ (12,135 )
Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Level 3 Inputs	Below is a reconciliation of the beginning and ending balances, for the periods shown, of assets and liabilities measured at fair value on a recurring basis using Level 3 inputs. Interest and dividend income are included in net investment income and are excluded from the reconciliation. Other assets and (liabilities) Balance - January 1, 2018 $ (2,952 ) Total realized and unrealized gains Included in other (loss) income 206 Purchases (34 ) Balance - March 31, 2018 $ (2,780 ) Other assets and (liabilities) Balance - January 1, 2017 $ (13,004 ) Total realized and unrealized gains Included in other (losses) income 1,071 Purchases (202 ) Balance - March 31, 2017 $ (12,135 )
Schedule Of Balances Elected To Account For At Fair Value	Below is a summary of the balances the Company has elected to account for at fair value: March 31, December 31, Other investments $ 692,652 $ 594,793 Other assets $ 2,533 $ 2,542 Other liabilities $ 5,313 $ 5,494
Schedule Of Other Investments Measured Using Net Asset Valuations	The table below shows the Company’s portfolio of other investments measured using net asset valuations as a practical expedient: At March 31, 2018 Fair Value Unfunded Redemption Frequency Redemption Redemption Private equity partnerships $ 190,067 $ 416,135 See below See below See below Senior secured bank loan funds 13,771 25,297 See below See below See below Hedge funds 12,280 — See below See below See below Total other investments measured using net asset valuations $ 216,118 $ 441,432

Reinsurance (Tables)

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2018
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Effect Of Reinsurance And Retrocessional Activity On Premiums Written And Earned And On Net Claims And Claim Expenses Incurred	The following table sets forth the effect of reinsurance and retrocessional activity on premiums written and earned and on net claims and claim expenses incurred: Three months ended March 31, March 31, Premiums written Direct $ 85,167 $ 73,408 Assumed 1,074,485 848,682 Ceded (496,608 ) (377,954 ) Net premiums written $ 663,044 $ 544,136 Premiums earned Direct $ 70,032 $ 58,168 Assumed 605,483 498,999 Ceded (235,233 ) (191,122 ) Net premiums earned $ 440,282 $ 366,045 Claims and claim expenses Gross claims and claim expenses incurred $ 225,742 $ 251,804 Claims and claim expenses recovered (54,039 ) (58,723 ) Net claims and claim expenses incurred $ 171,703 $ 193,081

Reserve for Claims and Claim 28

Reserve for Claims and Claim Expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Insurance Loss Reserves [Abstract]
Schedule of Liability for Unpaid Claims and Claim Expenses	The following table details the Company’s prior year development by segment of its liability for unpaid claims and claim expenses: Three months ended March 31, 2018 2017 (Favorable) adverse development (Favorable) adverse development Property $ (27,562 ) $ (928 ) Casualty and Specialty (3,791 ) 30,262 Other 18 (328 ) Total favorable development of prior accident years net claims and claim expenses $ (31,335 ) $ 29,006 The following table details the development of the Company’s liability for unpaid claims and claim expenses for its Casualty and Specialty segment: Three months ended March 31, 2018 2017 (Favorable) adverse development (Favorable) adverse development Actuarial methods $ (3,791 ) $ (5,999 ) Ogden Rate change — 33,481 Actuarial assumption changes — 2,780 Total adverse (favorable) development of prior accident years net claims and claim expenses $ (3,791 ) $ 30,262 Three months ended March 31, 2017 (Favorable) adverse development Catastrophe net claims and claim expenses Large catastrophe events Other $ 2,586 Total large catastrophe events 2,586 Small catastrophe events Fort McMurray Wildfire (2016) (5,850 ) Other 2,336 Total small catastrophe events (3,514 ) Total catastrophe net claims and claim expenses (928 ) Total net favorable development of prior accident years net claims and claim expenses $ (928 ) The following tables detail the development of the Company’s liability for unpaid claims and claim expenses for its Property segment, allocated between large and small catastrophe net claims and claim expenses and attritional net claims and claim expenses, included in the other line item: Three months ended March 31, 2018 (Favorable) adverse development Catastrophe net claims and claim expenses Large catastrophe events 2017 Catastrophe Events $ (27,109 ) Other (4,258 ) Total large catastrophe events (31,367 ) Small catastrophe events Other 3,805 Total small catastrophe events 3,805 Total catastrophe net claims and claim expenses (27,562 ) Total net favorable development of prior accident years net claims and claim expenses $ (27,562 ) The following table summarizes the Company’s claims and claim expense reserves by segment, allocated between case reserves, additional case reserves and IBNR: At March 31, 2018 Case Reserves Additional Case Reserves IBNR Total Property $ 701,202 $ 850,498 $ 687,209 $ 2,238,909 Casualty and Specialty 740,809 118,380 1,801,361 2,660,550 Other 4,999 — 8,269 13,268 Total $ 1,447,010 $ 968,878 $ 2,496,839 $ 4,912,727 At December 31, 2017 Property $ 696,285 $ 896,522 $ 893,583 $ 2,486,390 Casualty and Specialty 689,962 124,923 1,760,607 2,575,492 Other 6,605 — 11,921 18,526 Total $ 1,392,852 $ 1,021,445 $ 2,666,111 $ 5,080,408 Activity in the liability for unpaid claims and claim expenses is summarized as follows: Three months ended March 31, 2018 2017 Net reserves as of January 1 $ 3,493,778 $ 2,568,730 Net incurred related to: Current year 203,038 164,075 Prior years (31,335 ) 29,006 Total net incurred 171,703 193,081 Net paid related to: Current year 9,050 7,729 Prior years 328,129 147,500 Total net paid 337,179 155,229 Foreign exchange 12,104 2,287 Net reserves as of March 31 3,340,406 2,608,869 Reinsurance recoverable as of March 31 1,572,321 325,819 Gross reserves as of March 31 $ 4,912,727 $ 2,934,688

Debt and Credit Facilities (Tab

Debt and Credit Facilities (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	A summary of the Company’s debt obligations on its consolidated balance sheets is set forth below: March 31, 2018 December 31, 2017 Fair Value Carrying Value Fair Value Carrying Value 3.450% Senior Notes due 2027 $ 283,281 $ 295,425 $ 294,654 $ 295,303 3.700% Senior Notes due 2025 294,864 297,409 302,781 297,318 5.75% Senior Notes due 2020 262,188 249,353 263,750 249,272 4.750% Senior Notes due 2025 (DaVinciRe) (1) 153,546 147,808 157,050 147,730 $ 993,879 $ 989,995 $ 1,018,235 $ 989,623 (1) RenaissanceRe owns a noncontrolling economic interest in its joint venture DaVinciRe. Because RenaissanceRe controls a majority of DaVinciRe’s outstanding voting rights, the consolidated financial statements of DaVinciRe are included in the consolidated financial statements of RenaissanceRe. However, RenaissanceRe does not guarantee or provide credit support for DaVinciRe and RenaissanceRe’s financial exposure to DaVinciRe is limited to its investment in DaVinciRe’s shares and counterparty credit risk arising from reinsurance transactions.
Schedule of Line of Credit Facilities	The outstanding amounts issued or drawn under each of the Company’s significant credit facilities is set forth below: At March 31, 2018 Issued or Drawn RenaissanceRe Revolving Credit Facility $ — Uncommitted Standby Letter of Credit Facility with Wells Fargo 101,679 Bilateral Letter of Credit Facility with Citibank Europe 186,709 Funds at Lloyd’s Letter of Credit Facilities Renaissance Reinsurance FAL Facility 180,000 Total credit facilities in U.S. dollars $ 468,388 Funds at Lloyd’s Letter of Credit Facilities Specialty Risks FAL Facility £ 10,000 Total credit facilities in British Pounds £ 10,000

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 2018
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest [Abstract]
Schedule Of Redeemable Noncontrolling Interest	The activity in redeemable noncontrolling interest – DaVinciRe is detailed in the table below: Three months ended March 31, March 31, Beginning balance $ 1,011,659 $ 994,458 Redemption of shares from redeemable noncontrolling interest, net of adjustments (69 ) (63,642 ) Sale of shares to redeemable noncontrolling interests — 23,921 Net income attributable to redeemable noncontrolling interest 20,953 31,909 Ending balance $ 1,032,543 $ 986,646 A summary of the Company’s redeemable noncontrolling interests on its consolidated balance sheets is set forth below: March 31, December 31, 2017 Redeemable noncontrolling interest - DaVinciRe $ 1,032,543 $ 1,011,659 Redeemable noncontrolling interest - Medici 392,821 284,847 Redeemable noncontrolling interests $ 1,425,364 $ 1,296,506 A summary of the Company’s redeemable noncontrolling interests on its consolidated statements of operations is set forth below: Three months ended March 31, March 31, Redeemable noncontrolling interest - DaVinciRe $ 20,953 $ 31,909 Redeemable noncontrolling interest - Medici 8,946 2,418 Net income attributable to redeemable noncontrolling interests $ 29,899 $ 34,327 The activity in redeemable noncontrolling interest – Medici is detailed in the table below: Three months ended March 31, March 31, Beginning balance $ 284,847 $ 181,136 Redemption of shares from redeemable noncontrolling interest, net of adjustments (711 ) (10,625 ) Sale of shares to redeemable noncontrolling interests 99,739 28,416 Net income attributable to redeemable noncontrolling interest 8,946 2,418 Ending balance $ 392,821 $ 201,345

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share	The following table sets forth the computation of basic and diluted earnings per common share: Three months ended (common shares in thousands) March 31, March 31, Numerator: Net income available to RenaissanceRe common shareholders $ 56,713 $ 92,352 Amount allocated to participating common shareholders (1) (546 ) (907 ) Net income allocated to RenaissanceRe common shareholders $ 56,167 $ 91,445 Denominator: Denominator for basic income per RenaissanceRe common share - weighted average common shares 39,552 40,408 Per common share equivalents of employee stock options and restricted shares 47 215 Denominator for diluted income per RenaissanceRe common share - adjusted weighted average common shares and assumed conversions 39,599 40,623 Net income available to RenaissanceRe common shareholders per common share – basic $ 1.42 $ 2.26 Net income available to RenaissanceRe common shareholders per common share – diluted $ 1.42 $ 2.25 (1) Represents earnings attributable to holders of unvested restricted shares issued pursuant to the Company’s 2001 Stock Incentive Plan, 2010 Performance-Based Equity Incentive Plan, 2016 Long-Term Incentive Plan and to the Company’s non-employee directors.

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting, Measurement Disclosures [Abstract]
Schedule Of Significant Components Of The Company's Revenues And Expenses By Segment	A summary of the significant components of the Company’s revenues and expenses by segment is as follows: Three months ended March 31, 2018 Property Casualty and Specialty Other Total Gross premiums written $ 706,968 $ 452,684 $ — $ 1,159,652 Net premiums written $ 354,077 $ 308,967 $ — $ 663,044 Net premiums earned $ 225,049 $ 215,233 $ — $ 440,282 Net claims and claim expenses incurred 30,607 141,078 18 171,703 Acquisition expenses 40,721 56,990 — 97,711 Operational expenses 26,546 14,593 133 41,272 Underwriting income (loss) $ 127,175 $ 2,572 $ (151 ) 129,596 Net investment income 56,476 56,476 Net foreign exchange gains 3,757 3,757 Equity in earnings of other ventures 857 857 Other loss (1,242 ) (1,242 ) Net realized and unrealized losses on investments (82,144 ) (82,144 ) Corporate expenses (6,733 ) (6,733 ) Interest expense (11,767 ) (11,767 ) Income before taxes 88,800 Income tax benefit 3,407 3,407 Net income attributable to redeemable noncontrolling interests (29,899 ) (29,899 ) Dividends on preference shares (5,595 ) (5,595 ) Net income available to RenaissanceRe common shareholders $ 56,713 Net claims and claim expenses incurred – current accident year $ 58,169 $ 144,869 $ — $ 203,038 Net claims and claim expenses incurred – prior accident years (27,562 ) (3,791 ) 18 (31,335 ) Net claims and claim expenses incurred – total $ 30,607 $ 141,078 $ 18 $ 171,703 Net claims and claim expense ratio – current accident year 25.8 % 67.3 % 46.1 % Net claims and claim expense ratio – prior accident years (12.2 )% (1.8 )% (7.1 )% Net claims and claim expense ratio – calendar year 13.6 % 65.5 % 39.0 % Underwriting expense ratio 29.9 % 33.3 % 31.6 % Combined ratio 43.5 % 98.8 % 70.6 % Three months ended March 31, 2017 Property Casualty and Specialty Other Total Gross premiums written $ 520,529 $ 401,561 $ — $ 922,090 Net premiums written $ 289,871 $ 254,265 $ — $ 544,136 Net premiums earned $ 186,988 $ 179,059 $ (2 ) $ 366,045 Net claims and claim expenses incurred 38,838 154,571 (328 ) 193,081 Acquisition expenses 29,103 54,179 — 83,282 Operational expenses 27,665 19,607 11 47,283 Underwriting income (loss) $ 91,382 $ (49,298 ) $ 315 42,399 Net investment income 54,325 54,325 Net foreign exchange gains 8,165 8,165 Equity in losses of other ventures (1,507 ) (1,507 ) Other income 1,665 1,665 Net realized and unrealized gains on investments 43,373 43,373 Corporate expenses (5,286 ) (5,286 ) Interest expense (10,526 ) (10,526 ) Income before taxes and noncontrolling interests 132,608 Income tax expense (334 ) (334 ) Net income attributable to noncontrolling interests (34,327 ) (34,327 ) Dividends on preference shares (5,595 ) (5,595 ) Net income available to RenaissanceRe common shareholders $ 92,352 Net claims and claim expenses incurred – current accident year $ 39,766 $ 124,309 $ — $ 164,075 Net claims and claim expenses incurred – prior accident years (928 ) 30,262 (328 ) 29,006 Net claims and claim expenses incurred – total $ 38,838 $ 154,571 $ (328 ) $ 193,081 Net claims and claim expense ratio – current accident year 21.3 % 69.4 % 44.8 % Net claims and claim expense ratio – prior accident years (0.5 )% 16.9 % 7.9 % Net claims and claim expense ratio – calendar year 20.8 % 86.3 % 52.7 % Underwriting expense ratio 30.3 % 41.2 % 35.7 % Combined ratio 51.1 % 127.5 % 88.4 %

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Summary of Derivative Instruments [Abstract]
Schedule of Location on Consolidated Balance Sheets and Fair Value Of Principal Derivative Instruments	The tables below show the gross and net amounts of recognized derivative assets and liabilities at fair value, including the location on the consolidated balance sheets of the Company’s principal derivative instruments: Derivative Assets At March 31, 2018 Gross Amounts of Recognized Assets Gross Amounts Offset in the Balance Sheet Net Amounts of Assets Presented in the Balance Sheet Balance Sheet Location Collateral Net Amount Interest rate futures $ 175 157 $ 18 Other assets $ — $ 18 Interest rate swaps 357 — 357 Other assets — 357 Foreign currency forward contracts (1) 7,070 175 6,895 Other assets — 6,895 Foreign currency forward contracts (2) 79 78 1 Other assets — 1 Credit default swaps 1,600 — 1,600 Other assets — 1,600 Total $ 9,281 $ 410 $ 8,871 $ — $ 8,871 Derivative Liabilities At March 31, 2018 Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Balance Sheet Net Amounts of Liabilities Presented in the Balance Sheet Balance Sheet Location Collateral Pledged Net Amount Interest rate futures $ 404 157 $ 247 Other liabilities $ 247 $ — Interest rate swaps 53 — 53 Other liabilities 53 — Foreign currency forward contracts (1) 479 — 479 Other liabilities — 479 Foreign currency forward contracts (2) 643 78 565 Other liabilities — 565 Credit default swaps 13 — 13 Other liabilities 13 — Total $ 1,592 $ 235 $ 1,357 $ 313 $ 1,044 (1) Contracts used to manage foreign currency risks in underwriting and non-investment operations. (2) Contracts used to manage foreign currency risks in investment operations. Derivative Assets At December 31, 2017 Gross Amounts of Recognized Assets Gross Amounts Offset in the Balance Sheet Net Amounts of Assets Presented in the Balance Sheet Balance Sheet Location Collateral Net Amount Interest rate futures $ 684 524 $ 160 Other assets $ — $ 160 Interest rate swaps 424 — 424 Other assets — 424 Foreign currency forward contracts (1) 3,865 358 3,507 Other assets — 3,507 Foreign currency forward contracts (2) 39 11 28 Other assets — 28 Credit default swaps 1,518 — 1,518 Other assets — 1,518 Total $ 6,530 $ 893 $ 5,637 $ — $ 5,637 Derivative Liabilities At December 31, 2017 Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Balance Sheet Net Amounts of Liabilities Presented in the Balance Sheet Balance Sheet Location Collateral Pledged Net Amount Interest rate futures $ 729 524 $ 205 Other liabilities $ 205 $ — Foreign currency forward contracts (1) 670 — 670 Other liabilities — 670 Foreign currency forward contracts (2) 115 11 104 Other liabilities — 104 Credit default swaps 22 — 22 Other liabilities 22 — Total $ 1,536 $ 535 $ 1,001 $ 227 $ 774 (1) Contracts used to manage foreign currency risks in underwriting and non-investment operations. (2) Contracts used to manage foreign currency risks in investment operations.
Schedule of Gain (Loss) Recognized In Consolidated Statements Of Operations Related To Principal Derivative Instruments	The location and amount of the gain (loss) recognized in the Company’s consolidated statements of operations related to its principal derivative instruments are shown in the following table: Location of gain (loss) recognized on derivatives Amount of gain (loss) recognized on derivatives Three months ended March 31, 2018 2017 Interest rate futures Net realized and unrealized (losses) gains on investments $ (2,337 ) $ (158 ) Interest rate swaps Net realized and unrealized (losses) gains on investments (106 ) — Foreign currency forward contracts (1) Net foreign exchange gains 6,743 1,060 Foreign currency forward contracts (2) Net foreign exchange gains (691 ) (633 ) Credit default swaps Net realized and unrealized (losses) gains on investments (1,921 ) 102 Total $ 1,688 $ 371 (1) Contracts used to manage foreign currency risks in underwriting and non-investment operations. (2) Contracts used to manage foreign currency risks in investment operations.

Condensed Consolidating Finan34

Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries (Tables)	3 Months Ended
	Mar. 31, 2018
Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries [Abstract]
Condensed Consolidating Balance Sheets	(1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor, Subsidiary Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Balance Sheet at December 31, 2017 RenaissanceRe Holdings Ltd. (Parent Guarantor) RenRe North RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other RenaissanceRe Holdings Ltd. Subsidiaries and Eliminations (Non-guarantor Subsidiaries) (1) Consolidating Adjustments (2) RenaissanceRe Consolidated Assets Total investments $ 225,266 $ 129,732 $ 31,255 $ 9,117,186 $ — $ 9,503,439 Cash and cash equivalents 14,656 139 1,469 1,345,328 — 1,361,592 Investments in subsidiaries 4,105,760 36,140 1,141,733 — (5,283,633 ) — Due from subsidiaries and affiliates 4,602 91,891 — — (96,493 ) — Premiums receivable — — — 1,304,622 — 1,304,622 Prepaid reinsurance premiums — — — 533,546 — 533,546 Reinsurance recoverable — — — 1,586,630 — 1,586,630 Accrued investment income 405 428 82 41,320 — 42,235 Deferred acquisition costs — — — 426,551 — 426,551 Receivable for investments sold 135 51 8 102,951 — 103,145 Other assets 433,468 21,342 430,481 76,703 (840,768 ) 121,226 Goodwill and other intangible assets 124,960 — — 118,185 — 243,145 Total assets $ 4,909,252 $ 279,723 $ 1,605,028 $ 14,653,022 $ (6,220,894 ) $ 15,226,131 Liabilities, Redeemable Noncontrolling Interest and Shareholders’ Equity Liabilities Reserve for claims and claim expenses $ — $ — $ — $ 5,080,408 $ — $ 5,080,408 Unearned premiums — — — 1,477,609 — 1,477,609 Debt 417,000 — 841,892 147,731 (417,000 ) 989,623 Amounts due to subsidiaries and affiliates 82,579 54 92,794 — (175,427 ) — Reinsurance balances payable — — — 989,090 — 989,090 Payable for investments purchased — — — 208,749 — 208,749 Other liabilities 18,298 1,053 14,117 764,432 (5,129 ) 792,771 Total liabilities 517,877 1,107 948,803 8,668,019 (597,556 ) 9,538,250 Redeemable noncontrolling interests — — — 1,296,506 — 1,296,506 Shareholders’ Equity Total shareholders’ equity 4,391,375 278,616 656,225 4,688,497 (5,623,338 ) 4,391,375 Total liabilities, redeemable noncontrolling interest and shareholders’ equity $ 4,909,252 $ 279,723 $ 1,605,028 $ 14,653,022 $ (6,220,894 ) $ 15,226,131 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor and Subsidiary Issuer consolidating adjustments.
Condensed Consolidating Statements of Operations	Condensed Consolidating Statement of Operations for RenaissanceRe RenRe North RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Revenues Net premiums earned $ — $ — $ — $ 440,282 $ — $ 440,282 Net investment income 6,035 513 1,234 56,305 (7,611 ) 56,476 Net foreign exchange (losses) gains (3 ) — — 3,760 — 3,757 Equity in earnings (losses) of other ventures — — 1,211 (354 ) — 857 Other loss — — — (1,242 ) — (1,242 ) Net realized and unrealized losses on investments (661 ) (1,286 ) (259 ) (79,938 ) — (82,144 ) Total revenues 5,371 (773 ) 2,186 418,813 (7,611 ) 417,986 Expenses Net claims and claim expenses incurred — — — 171,703 — 171,703 Acquisition expenses — — — 97,711 — 97,711 Operational expenses 1,313 10 11,070 37,933 (9,054 ) 41,272 Corporate expenses 3,684 — — 3,049 — 6,733 Interest expense 1,108 — 9,252 2,515 (1,108 ) 11,767 Total expenses 6,105 10 20,322 312,911 (10,162 ) 329,186 (Loss) income before equity in net income (loss) of subsidiaries and taxes (734 ) (783 ) (18,136 ) 105,902 2,551 88,800 Equity in net income (loss) of subsidiaries 62,426 834 (3,813 ) — (59,447 ) — Income (loss) before taxes 61,692 51 (21,949 ) 105,902 (56,896 ) 88,800 Income tax benefit 616 221 1,815 755 — 3,407 Net income (loss) 62,308 272 (20,134 ) 106,657 (56,896 ) 92,207 Net loss attributable to redeemable noncontrolling interests — — — (29,899 ) — (29,899 ) Net income (loss) attributable to RenaissanceRe 62,308 272 (20,134 ) 76,758 (56,896 ) 62,308 Dividends on preference shares (5,595 ) — — — — (5,595 ) Net income (loss) available (attributable) to RenaissanceRe common shareholders $ 56,713 $ 272 $ (20,134 ) $ 76,758 $ (56,896 ) $ 56,713 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor, Subsidiary Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Statement of Operations for the three months ended March 31, 2017 RenaissanceRe RenRe North Inc. Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Revenues Net premiums earned $ — $ — $ — $ — $ 366,045 $ — $ 366,045 Net investment income 5,457 426 841 269 53,583 (6,251 ) 54,325 Net foreign exchange gains — — — — 8,165 — 8,165 Equity in losses of other ventures — — — (752 ) (755 ) — (1,507 ) Other (loss) income (1 ) — — — 1,666 — 1,665 Net realized and unrealized gains (losses) on investments 53 2,921 4,725 (26 ) 35,700 — 43,373 Total revenues 5,509 3,347 5,566 (509 ) 464,404 (6,251 ) 472,066 Expenses Net claims and claim expenses incurred — — — — 193,081 — 193,081 Acquisition expenses — — — — 83,282 — 83,282 Operational expenses 3,298 24 50 7,979 42,058 (6,126 ) 47,283 Corporate expenses 5,208 — — — 78 — 5,286 Interest expense 140 — 1,476 6,542 2,508 (140 ) 10,526 Total expenses 8,646 24 1,526 14,521 321,007 (6,266 ) 339,458 (Loss) income before equity in net income of subsidiaries and taxes (3,137 ) 3,323 4,040 (15,030 ) 143,397 15 132,608 Equity in net income of subsidiaries 101,353 1,086 9,843 16,498 — (128,780 ) — Income before taxes 98,216 4,409 13,883 1,468 143,397 (128,765 ) 132,608 Income tax (expense) benefit (269 ) (1,098 ) (1,308 ) 3,072 (731 ) — (334 ) Net income 97,947 3,311 12,575 4,540 142,666 (128,765 ) 132,274 Net income attributable to redeemable noncontrolling interests — — — — (34,327 ) — (34,327 ) Net income attributable to RenaissanceRe 97,947 3,311 12,575 4,540 108,339 (128,765 ) 97,947 Dividends on preference shares (5,595 ) — — — — — (5,595 ) Net income available to RenaissanceRe common shareholders $ 92,352 $ 3,311 $ 12,575 $ 4,540 $ 108,339 $ (128,765 ) $ 92,352 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor and Subsidiary Issuer consolidating adjustments.
Condensed Consolidating Statement of Comprehensive Income (Loss)	Condensed Consolidating Statement of Comprehensive Income (Loss) for the three months ended March 31, 2018 RenaissanceRe RenRe North RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Comprehensive income (loss) Net income (loss) $ 62,308 $ 272 $ (20,134 ) $ 106,657 $ (56,896 ) $ 92,207 Change in net unrealized gains on investments — — — (30 ) — (30 ) Comprehensive income (loss) 62,308 272 (20,134 ) 106,627 (56,896 ) 92,177 Net income attributable to redeemable noncontrolling interests — — — (29,899 ) — (29,899 ) Comprehensive income attributable to noncontrolling interests — — — (29,899 ) — (29,899 ) Comprehensive income (loss) attributable to RenaissanceRe $ 62,308 $ 272 $ (20,134 ) $ 76,728 $ (56,896 ) $ 62,278 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor, Subsidiary Guarantor and Subsidiary Issuer consolidating adjustments. Condensed Consolidating Statement of Comprehensive Income for the three months ended March 31, 2017 RenaissanceRe RenRe North Inc. Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other Consolidating RenaissanceRe Comprehensive income Net income $ 97,947 $ 3,311 $ 12,575 $ 4,540 $ 142,666 $ (128,765 ) $ 132,274 Change in net unrealized gains on investments — — — — (1,491 ) — (1,491 ) Comprehensive income 97,947 3,311 12,575 4,540 141,175 (128,765 ) 130,783 Net income attributable to redeemable noncontrolling interests — — — — (34,327 ) — (34,327 ) Comprehensive income attributable to redeemable noncontrolling interests — — — — (34,327 ) — (34,327 ) Comprehensive income available to RenaissanceRe $ 97,947 $ 3,311 $ 12,575 $ 4,540 $ 106,848 $ (128,765 ) $ 96,456 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. (2) Includes Parent Guarantor and Subsidiary Issuer consolidating adjustments.
Condensed Consolidating Statements Of Cash Flows	Condensed Consolidating Statement of Cash Flows for the three months ended March 31, 2018 RenaissanceRe RenRe North Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other RenaissanceRe Consolidated Cash flows (used in) provided by operating activities Net cash (used in) provided by operating activities $ (6,875 ) $ 659 $ (23,449 ) $ (7,684 ) $ (37,349 ) Cash flows provided by (used in) investing activities Proceeds from sales and maturities of fixed maturity investments trading 119,542 42,793 27,672 2,128,852 2,318,859 Purchases of fixed maturity investments trading (20,216 ) (22,956 ) (12,698 ) (2,256,591 ) (2,312,461 ) Net (purchases) sales of equity investments trading — (21 ) — 158 137 Net sales (purchases) of short term investments 54,728 (4,024 ) (5,925 ) (639,420 ) (594,641 ) Net sales of other investments — — — (98,639 ) (98,639 ) Dividends and return of capital from subsidiaries 177,250 — — (177,250 ) — Contributions to subsidiaries (150,205 ) (16,500 ) — 166,705 — Due to (from) subsidiary (154,877 ) 7 14,106 140,764 — Net cash provided by (used in) investing activities 26,222 (701 ) — 23,155 (753,395 ) (704,719 ) Cash flows (used in) provided by financing activities Dividends paid – RenaissanceRe common shares (13,224 ) — — — — (13,224 ) Dividends paid – preference shares (5,595 ) — — — — (5,595 ) Net third party redeemable noncontrolling interest share transactions — — — 52,759 52,759 Taxes paid on withholding shares (7,034 ) — — — — (7,034 ) Net cash (used in) provided by financing activities (25,853 ) — — — 52,759 26,906 Effect of exchange rate changes on foreign currency cash — — — — 1,543 1,543 Net decrease in cash and cash equivalents (6,506 ) (42 ) — (294 ) (706,777 ) (713,619 ) Cash and cash equivalents, beginning of period 14,656 139 1,469 1,345,328 1,361,592 Cash and cash equivalents, end of period $ 8,150 $ 97 $ — $ 1,175 $ 638,551 $ 647,973 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations. Condensed Consolidating Statement of Cash Flows for the three months ended March 31, 2017 RenaissanceRe RenRe North Inc. Platinum Underwriters Finance, Inc. (Subsidiary Issuer) RenaissanceRe Finance, Inc. (Subsidiary Issuer) Other RenaissanceRe Holdings Ltd. Subsidiaries and Eliminations (Non-guarantor Subsidiaries) (1) RenaissanceRe Consolidated Cash flows (used in) provided by operating activities Net cash (used in) provided by operating activities $ (12,358 ) $ (8,594 ) $ 5,188 $ (17,914 ) $ 234,717 $ 201,039 Cash flows provided by (used in) investing activities Proceeds from sales and maturities of fixed maturity investments trading 38,449 12,473 36,397 15,449 2,579,618 2,682,386 Purchases of fixed maturity investments trading (63,417 ) (12,438 ) (36,790 ) — (2,894,479 ) (3,007,124 ) Net (purchases) sales of equity investments trading — (74 ) (2,181 ) — 16,002 13,747 Net sales (purchases) of short term investments 269,585 (590 ) (5,087 ) (3,374 ) (14,841 ) 245,693 Net sales of other investments — — — — 36,402 36,402 Return of investment from investment in other ventures — — — — 20,000 20,000 Dividends and return of capital from subsidiaries 65,180 9,175 — 9,175 (83,530 ) — Contributions to subsidiaries (162,550 ) — — (9,175 ) 171,725 — Due (from) to subsidiaries (28,130 ) 50 (34 ) 2,522 25,592 — Net cash provided by (used in) investing activities 119,117 8,596 (7,695 ) 14,597 (143,511 ) (8,896 ) Cash flows used in financing activities Dividends paid – RenaissanceRe common shares (13,027 ) — — — — (13,027 ) Dividends paid – preference shares (5,595 ) — — — — (5,595 ) RenaissanceRe common share repurchases (80,009 ) — — — — (80,009 ) Net third party redeemable noncontrolling interest share transactions — — — — (51,166 ) (51,166 ) Taxes paid on withholding shares (11,018 ) — — — — (11,018 ) Net cash used in financing activities (109,649 ) — — — (51,166 ) (160,815 ) Effect of exchange rate changes on foreign currency cash — — — — 1,602 1,602 Net (decrease) increase in cash and cash equivalents (2,890 ) 2 (2,507 ) (3,317 ) 41,642 32,930 Cash and cash equivalents, beginning of period 7,067 162 6,671 9,397 397,860 421,157 Cash and cash equivalents, end of period $ 4,177 $ 164 $ 4,164 $ 6,080 $ 439,502 $ 454,087 (1) Includes all other subsidiaries of RenaissanceRe Holdings Ltd. and eliminations.

Organization (Details)

Organization (Details)	Nov. 13, 2014
RenaissanceRe Upsilon Fund Ltd. | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Percent of segregated funds owned by third party investors	100.00%

Significant Accounting Polici36

Significant Accounting Policies Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in cash inflows from cash flows provided by operating activities	$ 37,349	$ (201,039)
Increase in cash flows used in investing activities	$ 704,719	8,896
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in cash inflows from cash flows provided by operating activities		20,000
Increase in cash flows used in investing activities		$ 20,000
Retained Earnings | Cumulative effect of adoption of ASU 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			$ 2,200

Investments (Schedule of Fair V

Investments (Schedule of Fair Value of Fixed Maturity Investments Trading) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Total fixed maturity investments trading	$ 7,404,761	$ 7,426,555
U.S. treasuries
Investment [Line Items]
Total fixed maturity investments trading	2,834,487	3,168,763
Agencies
Investment [Line Items]
Total fixed maturity investments trading	45,365	47,646
Municipal
Investment [Line Items]
Total fixed maturity investments trading	506,470	509,802
Non-U.S. government (Sovereign debt)
Investment [Line Items]
Total fixed maturity investments trading	303,056	287,660
Non-U.S. government-backed corporate
Investment [Line Items]
Total fixed maturity investments trading	191,202	163,651
Corporate
Investment [Line Items]
Total fixed maturity investments trading	2,147,578	2,063,459
Agency mortgage-backed
Investment [Line Items]
Total fixed maturity investments trading	693,377	500,456
Non-agency mortgage-backed
Investment [Line Items]
Total fixed maturity investments trading	302,638	300,331
Commercial mortgage-backed
Investment [Line Items]
Total fixed maturity investments trading	197,126	202,062
Asset-backed
Investment [Line Items]
Total fixed maturity investments trading	$ 183,462	$ 182,725

Investments (Schedule of Contra

Investments (Schedule of Contractual Maturities of Fixed Maturity Investments) (Details) $ in Thousands	Mar. 31, 2018USD ($)
Trading Securities [Abstract]
Amortized Cost, Due in less than one year	$ 496,788
Amortized Cost, Due after one through five years	4,381,056
Amortized Cost, Due after five through ten years	1,073,453
Amortized Cost, Due after ten years	145,438
Amortized Cost	7,470,003
Fair Value, Due in less than one year	495,143
Fair Value, Due after one through five years	4,324,744
Fair Value, Due after five through ten years	1,064,575
Fair Value, Due after ten years	143,696
Fair Value	7,404,761
Mortgage-backed
Trading Securities [Abstract]
Amortized Cost	1,189,730
Fair Value	1,193,141
Asset-backed
Trading Securities [Abstract]
Amortized Cost	183,538
Fair Value	$ 183,462

Investments (Schedule of Fair39

Investments (Schedule of Fair Value of Equity Investments Trading) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Equity investments trading	$ 387,462	$ 388,254
Financials
Schedule of Trading Securities and Other Trading Assets [Line Items]
Equity investments trading	253,905	253,543
Communications and technology
Schedule of Trading Securities and Other Trading Assets [Line Items]
Equity investments trading	51,400	49,526
Industrial, utilities and energy
Schedule of Trading Securities and Other Trading Assets [Line Items]
Equity investments trading	32,790	34,325
Consumer
Schedule of Trading Securities and Other Trading Assets [Line Items]
Equity investments trading	23,886	24,779
Healthcare
Schedule of Trading Securities and Other Trading Assets [Line Items]
Equity investments trading	21,042	21,364
Basic materials
Schedule of Trading Securities and Other Trading Assets [Line Items]
Equity investments trading	$ 4,439	$ 4,717

Investments (Pledged Investment

Investments (Pledged Investments) (Details) - USD ($) $ in Billions	Mar. 31, 2018	Dec. 31, 2017
Investments [Abstract]
Cash and investments at fair value on deposit with, or in trust accounts for the benefit of various counterparties	$ 4.7	$ 3.3
Cash and investments at fair value on deposit with, or in trust accounts for the benefit of U.S. state regulatory authorities	$ 1.7	$ 1.4

Investments (Reverse Purchase A

Investments (Reverse Purchase Agreements) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Value of reverse repurchase agreements	$ 65.3	$ 30
Minimum required collateral for reverse repurchase agreements, expressed as a percentage of loan principal	102.00%

Investments (Schedule of Net In

Investments (Schedule of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income before investment expenses	$ 59,799	$ 58,017
Investment expenses	(3,323)	(3,692)
Net investment income	56,476	54,325
Fixed maturity investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income before investment expenses	45,643	43,419
Short term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income before investment expenses	5,304	1,724
Equity investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income before investment expenses	698	811
Private equity investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income before investment expenses	(434)	7,802
Other
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income before investment expenses	8,023	4,072
Cash and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income before investment expenses	$ 565	$ 189

Investments (Schedule of Net Re

Investments (Schedule of Net Realized and Unrealized (Losses) Gains on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Gain (Loss) on Investments [Line Items]
Net realized and unrealized (losses) gains on investments	$ (82,144)	$ 43,373
Fixed maturity investments
Gain (Loss) on Investments [Line Items]
Gross realized gains	4,583	11,461
Gross realized losses	(25,853)	(16,533)
Net realized gains on fixed maturity investments	(21,270)	(5,072)
Net unrealized gains (losses) on investments trading	(55,372)	24,635
Derivatives
Gain (Loss) on Investments [Line Items]
Net realized and unrealized losses on investments-related derivatives	(4,364)	(56)
Equity investments
Gain (Loss) on Investments [Line Items]
Net realized gains on fixed maturity investments	234	20,915
Net unrealized gains (losses) on investments trading	(1,372)	2,951
Net realized and unrealized (losses) gains on equity investments trading	$ (1,138)	$ 23,866

Fair Value Measurements (Assets

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments trading	$ 387,462	$ 388,254
Other investments	692,652	594,793
Other assets	2,533	2,542
Other (liabilities)	(5,313)	(5,494)
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	7,404,761	7,426,555
Short term investments	1,616,597	991,863
Equity investments trading	387,462	388,254
Other investments	692,652	594,793
Other assets	4,734	1,684
Total assets and liabilities measured on recurring basis	10,106,206	9,403,149
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	2,834,487	3,168,763
Short term investments	0	0
Equity investments trading	387,462	388,254
Other investments	0	0
Other (liabilities)	(229)	(45)
Total assets and liabilities measured on recurring basis	3,221,720	3,556,972
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	4,570,274	4,257,792
Short term investments	1,616,597	991,863
Equity investments trading	0	0
Other investments	476,534	380,475
Other assets	7,743	4,681
Total assets and liabilities measured on recurring basis	6,671,148	5,634,811
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Short term investments	0	0
Equity investments trading	0	0
Other investments	0	0
Other (liabilities)	(2,780)	(2,952)
Total assets and liabilities measured on recurring basis	(2,780)	(2,952)
Fair Value, Measurements, Recurring | U.S. treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	2,834,487	3,168,763
Fair Value, Measurements, Recurring | U.S. treasuries | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	2,834,487	3,168,763
Fair Value, Measurements, Recurring | U.S. treasuries | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | U.S. treasuries | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	45,365	47,646
Fair Value, Measurements, Recurring | Agencies | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Agencies | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	45,365	47,646
Fair Value, Measurements, Recurring | Agencies | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	506,470	509,802
Fair Value, Measurements, Recurring | Municipal | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Municipal | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	506,470	509,802
Fair Value, Measurements, Recurring | Municipal | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Non-U.S. government (Sovereign debt)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	303,056	287,660
Fair Value, Measurements, Recurring | Non-U.S. government (Sovereign debt) | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Non-U.S. government (Sovereign debt) | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	303,056	287,660
Fair Value, Measurements, Recurring | Non-U.S. government (Sovereign debt) | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Non-U.S. government-backed corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	191,202	163,651
Fair Value, Measurements, Recurring | Non-U.S. government-backed corporate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Non-U.S. government-backed corporate | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	191,202	163,651
Fair Value, Measurements, Recurring | Non-U.S. government-backed corporate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	2,147,578	2,063,459
Fair Value, Measurements, Recurring | Corporate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Corporate | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	2,147,578	2,063,459
Fair Value, Measurements, Recurring | Corporate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Agency mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	693,377	500,456
Fair Value, Measurements, Recurring | Agency mortgage-backed | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Agency mortgage-backed | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	693,377	500,456
Fair Value, Measurements, Recurring | Agency mortgage-backed | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Non-agency mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	302,638	300,331
Fair Value, Measurements, Recurring | Non-agency mortgage-backed | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Non-agency mortgage-backed | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	302,638	300,331
Fair Value, Measurements, Recurring | Non-agency mortgage-backed | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Commercial mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	197,126	202,062
Fair Value, Measurements, Recurring | Commercial mortgage-backed | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Commercial mortgage-backed | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	197,126	202,062
Fair Value, Measurements, Recurring | Commercial mortgage-backed | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	183,462	182,725
Fair Value, Measurements, Recurring | Asset-backed | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Asset-backed | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	183,462	182,725
Fair Value, Measurements, Recurring | Asset-backed | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	476,534	380,475
Fair Value, Measurements, Recurring | Catastrophe bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Catastrophe bonds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	476,534	380,475
Fair Value, Measurements, Recurring | Catastrophe bonds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Private equity partnerships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	190,067	196,220
Fair Value, Measurements, Recurring | Private equity partnerships | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Private equity partnerships | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Private equity partnerships | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Senior secured bank loan funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	13,771	17,574
Fair Value, Measurements, Recurring | Senior secured bank loan funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Senior secured bank loan funds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Senior secured bank loan funds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	12,280	524
Fair Value, Measurements, Recurring | Hedge funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Hedge funds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Hedge funds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Fair Value, Measurements, Recurring | Assumed and ceded (re)insurance contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other (liabilities)	(2,780)	(2,952)
Fair Value, Measurements, Recurring | Assumed and ceded (re)insurance contracts | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other (liabilities)	0	0
Fair Value, Measurements, Recurring | Assumed and ceded (re)insurance contracts | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other (liabilities)	0	0
Fair Value, Measurements, Recurring | Assumed and ceded (re)insurance contracts | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other (liabilities)	(2,780)	(2,952)
Fair Value, Measurements, Recurring | Assumed and ceded (re)insurance contracts | Significant Unobservable Inputs (Level 3) | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	2,500	2,500
Fair Value, Measurements, Recurring | Assumed and ceded (re)insurance contracts | Significant Unobservable Inputs (Level 3) | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other (liabilities)	(5,300)	(5,500)
Fair Value, Measurements, Recurring | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	7,514	4,636
Fair Value, Measurements, Recurring | Derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other (liabilities)	(229)	(45)
Fair Value, Measurements, Recurring | Derivatives | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	7,743	4,681
Fair Value, Measurements, Recurring | Derivatives | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other (liabilities)	$ 0	$ 0

Reinsurance (Effect Of Reinsura

Reinsurance (Effect Of Reinsurance And Retrocessional Activity On Premiums Written And Earned And On Net Claims And Claim Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Premiums written
Direct	$ 85,167	$ 73,408
Assumed	1,074,485	848,682
Ceded	(496,608)	(377,954)
Net premiums written	663,044	544,136
Premiums earned
Direct	70,032	58,168
Assumed	605,483	498,999
Ceded	(235,233)	(191,122)
Net premiums earned	440,282	366,045
Claims and claim expenses
Gross claims and claim expenses incurred	225,742	251,804
Claims and claim expenses recovered	(54,039)	(58,723)
Net claims and claim expenses incurred	$ 171,703	$ 193,081

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other liabilities	$ 5,313,000		$ 5,494,000
Debt	989,995,000		989,623,000
Long-term debt, fair value	993,900,000		$ 1,000,000,000
Net unrealized gains recognized in earnings	1,465,000	$ 6,863,000
Investment balance	216,118,000
Other Investments | Net investment income
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized gains recognized in earnings	1,500,000	6,900,000
Other assets and (liabilities) | Other income (loss)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized gains recognized in earnings	0	$ 0
Significant Unobservable Inputs (Level 3) | Internal valuation model | Assumed reinsurance contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value	893,000
Significant Unobservable Inputs (Level 3) | Internal valuation model | Assumed and ceded (re)insurance contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, fair value	$ 3,673,000
U.S. treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.30%		1.90%
Agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.40%		2.10%
Municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.50%		2.20%
Non-U.S. government (Sovereign debt)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.40%		2.00%
Non-U.S. government-backed corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.70%		2.30%
Corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	4.20%		3.80%
Agency mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.30%		3.00%
Weighted average life	7 years 3 months 18 days	6 years 4 months 24 days
Non-agency prime residential mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.90%		3.70%
Weighted average life	5 years 3 months 18 days	5 years 1 month 6 days
Alt-A non-agency mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.80%		3.70%
Weighted average life	6 years 2 months 12 days	6 years 2 months 12 days
Commercial mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.30%		2.90%
Weighted average life	4 years 8 months	4 years 6 months
Asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.50%		2.80%
Weighted average life	3 years 2 months	3 years
Short term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	1.70%		1.40%
Private equity partnerships
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment balance	$ 190,067,000
Private equity partnerships | Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	7 years
Private equity partnerships | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	10 years
Senior secured bank loan funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment in closed end fund	$ 13,800,000
Investment balance	$ 13,771,000
Senior secured bank loan funds | Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	4 years
Senior secured bank loan funds | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	5 years
Hedge funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment balance	$ 12,280,000
Hedge funds redeemable at option of shareholder
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment balance	11,800,000
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	989,995,000		$ 989,623,000
Long-term debt, fair value	$ 993,879,000		$ 1,018,235,000

Reinsurance (Narrative) (Detail

Reinsurance (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Reinsurance recoverable	$ 1,572,321	$ 325,819	$ 1,586,630
Allowance for reinsurance recoverable
Ceded Credit Risk [Line Items]
Valuation allowances and reserves balance	$ 7,800		$ 7,000
Customer Concentration Risk, Customer One | Reinsurance recoverable
Ceded Credit Risk [Line Items]
Concentration risk, percentage	9.30%	10.40%
Customer Concentration Risk, Customer One | Allowance for reinsurance recoverable
Ceded Credit Risk [Line Items]
Concentration risk, percentage	16.10%	11.10%
Customer Concentration Risk, Customer Two | Reinsurance recoverable
Ceded Credit Risk [Line Items]
Concentration risk, percentage	8.10%	7.50%
Customer Concentration Risk, Customer Two | Allowance for reinsurance recoverable
Ceded Credit Risk [Line Items]
Concentration risk, percentage	15.20%	9.20%
Customer Concentration Risk, Customer Three | Reinsurance recoverable
Ceded Credit Risk [Line Items]
Concentration risk, percentage	6.70%	7.30%
Customer Concentration Risk, Customer Three | Allowance for reinsurance recoverable
Ceded Credit Risk [Line Items]
Concentration risk, percentage	14.20%	8.40%
Ceded Credit Risk, Secured | Reinsurer Concentration Risk | Reinsurance recoverable
Ceded Credit Risk [Line Items]
Concentration risk, percentage	52.20%	54.50%
Ceded Credit Risk, Unsecured | Reinsurer Concentration Risk | Reinsurance recoverable | Standard & Poor's, A- Rating
Ceded Credit Risk [Line Items]
Concentration risk, percentage	46.80%	44.50%
Ceded Credit Risk, Unsecured | Reinsurer Concentration Risk | Reinsurance recoverable | Standard & Poor's, BBB Rating
Ceded Credit Risk [Line Items]
Concentration risk, percentage	1.00%	1.00%

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Information Used As Level 3 Inputs) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Total other assets and (liabilities)	$ 2,533	$ 2,542
Internal valuation model | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Total other assets and (liabilities)	2,780
Assumed and ceded (re)insurance contracts, group one | Internal valuation model | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other assets	$ 893
Assumed and ceded (re)insurance contracts, group one | Internal valuation model | Fair Value (Level 3) | Low
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Bond price (in dollars per share)	$ 101.46
Assumed and ceded (re)insurance contracts, group one | Internal valuation model | Fair Value (Level 3) | High
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Bond price (in dollars per share)	112.05
Assumed and ceded (re)insurance contracts, group one | Internal valuation model | Fair Value (Level 3) | Weighted Average or Actual
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Bond price (in dollars per share)	$ 107.31
Liquidity discount	1.30%
Assumed and ceded (re)insurance contracts, group two | Internal valuation model | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other (liabilities)	$ (3,673)
Assumed and ceded (re)insurance contracts, group two | Internal valuation model | Fair Value (Level 3) | Low
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Contract period	2 years
Assumed and ceded (re)insurance contracts, group two | Internal valuation model | Fair Value (Level 3) | High
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Contract period	4 years 8 months 12 days
Assumed and ceded (re)insurance contracts, group two | Internal valuation model | Fair Value (Level 3) | Weighted Average or Actual
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Net undiscounted cash flows	$ (4,706)
Expected loss ratio	20.40%
Net acquisition expense ratio	13.70%
Contract period	4 years 1 month 6 days
Discount rate	2.40%

Fair Value Measurements (Asse49

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Level 3 Inputs) (Details) - Other assets and (liabilities) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	$ (2,952)	$ (13,004)
Total realized and unrealized gains
Purchases	(34)	(202)
Balance at end of the period	(2,780)	(12,135)
Other income (loss)
Total realized and unrealized gains
Included in other (loss) income	$ 206	$ 1,071

Fair Value Measurements (Summar

Fair Value Measurements (Summary Of The Balances Company Has Elected To Account For At Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Other investments	$ 692,652	$ 594,793
Other assets	2,533	2,542
Other liabilities	$ 5,313	$ 5,494

Fair Value Measurements (Compan

Fair Value Measurements (Company's Portfolio of Other Investments Measured Using Net Asset Valuations) (Details) $ in Thousands	Mar. 31, 2018USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 216,118
Unfunded Commitments	441,432
Private equity partnerships
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	190,067
Unfunded Commitments	416,135
Senior secured bank loan funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	13,771
Unfunded Commitments	25,297
Hedge funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	12,280
Unfunded Commitments	$ 0

Reserve for Claims and Claim 52

Reserve for Claims and Claim Expenses (Claims and Claim Expense Reserves by Segment) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Case Reserves	$ 1,447,010	$ 1,392,852
Additional Case Reserves	968,878	1,021,445
IBNR	2,496,839	2,666,111
Net reserve for claims and claim expenses	4,912,727	5,080,408	$ 2,934,688
Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Case Reserves	4,999	6,605
Additional Case Reserves	0	0
IBNR	8,269	11,921
Net reserve for claims and claim expenses	13,268	18,526
Property
Liability for Claims and Claims Adjustment Expense [Line Items]
Case Reserves	701,202	696,285
Additional Case Reserves	850,498	896,522
IBNR	687,209	893,583
Net reserve for claims and claim expenses	2,238,909	2,486,390
Casualty and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Case Reserves	740,809	689,962
Additional Case Reserves	118,380	124,923
IBNR	1,801,361	1,760,607
Net reserve for claims and claim expenses	$ 2,660,550	$ 2,575,492

Reserve for Claims and Claim 53

Reserve for Claims and Claim Expenses (Schedule of Liability for Unpaid Claims and Claims Adjustment Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Net reserves as of January 1	$ 3,493,778	$ 2,568,730
Net incurred related to:
Current year	203,038	164,075
Prior years	(31,335)	29,006
Total net incurred	171,703	193,081
Net paid related to:
Current year	9,050	7,729
Prior years	328,129	147,500
Total net paid	337,179	155,229
Foreign exchange	12,104	2,287
Net reserves as of March 31	3,340,406	2,608,869
Reinsurance recoverable as of March 31	1,572,321	325,819
Gross reserves as of March 31	$ 4,912,727	$ 2,934,688

Reserve for Claims and Claim 54

Reserve for Claims and Claim Expenses (Prior Year Development of the Reserve for Net Claims and Claim Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	$ (31,335)	$ 29,006
Ogden Rate | Maximum
Liability for Catastrophe Claims [Line Items]
Discount rate		2.50%
Ogden Rate | Minimum
Liability for Catastrophe Claims [Line Items]
Discount rate		(0.75%)
Other
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	18	$ (328)
Property
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(27,562)	(928)
Property | Large and Small Catastrophe Events
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(27,562)	(928)
Property | Large catastrophe events
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(31,367)	2,586
Property | 2017 Catastrophe Events
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(27,109)
Property | Other
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(4,258)	2,586
Property | Small catastrophe events
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	3,805	(3,514)
Property | Fort McMurray Wildfire (2016)
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years		(5,850)
Property | Other
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	3,805	2,336
Property | Other Large and Small Catastrophic Events
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(500)
Casualty and Specialty
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(3,791)	30,262
Casualty and Specialty | Actuarial methods
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	(3,791)	(5,999)
Casualty and Specialty | Ogden Rate change
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	0	33,481
Casualty and Specialty | Actuarial assumption changes
Liability for Catastrophe Claims [Line Items]
Net claims and claim expenses incurred – prior accident years	$ 0	$ 2,780

Debt and Credit Facilities (Sum

Debt and Credit Facilities (Summary of Debt Obligations) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Fair Value	$ 993,900	$ 1,000,000
Carrying Value	$ 989,995	989,623
3.450% Senior Notes due 2027
Debt Instrument [Line Items]
Debt instrument, Interest rate	3.45%
3.700% Senior Notes due 2025
Debt Instrument [Line Items]
Debt instrument, Interest rate	3.70%
5.75% Senior Notes due 2020
Debt Instrument [Line Items]
Debt instrument, Interest rate	5.75%
4.750% Senior Notes due 2025 (DaVinciRe)
Debt Instrument [Line Items]
Debt instrument, Interest rate	4.75%
Senior Notes
Debt Instrument [Line Items]
Fair Value	$ 993,879	1,018,235
Carrying Value	989,995	989,623
Senior Notes | 3.450% Senior Notes due 2027 | RenaissanceRe Finance, Inc.
Debt Instrument [Line Items]
Fair Value	283,281	294,654
Carrying Value	295,425	295,303
Senior Notes | 3.700% Senior Notes due 2025
Debt Instrument [Line Items]
Fair Value	294,864	302,781
Carrying Value	297,409	297,318
Senior Notes | 5.75% Senior Notes due 2020
Debt Instrument [Line Items]
Fair Value	262,188	263,750
Carrying Value	249,353	249,272
Senior Notes | 4.750% Senior Notes due 2025 (DaVinciRe) | DaVinciRe Holdings Ltd.
Debt Instrument [Line Items]
Fair Value	153,546	157,050
Carrying Value	$ 147,808	$ 147,730

Debt and Credit Facilities (Sch

Debt and Credit Facilities (Schedule of Credit Facilities) (Details) - Mar. 31, 2018 £ in Thousands, $ in Thousands	USD ($)	GBP (£)
Line of Credit Facility [Line Items]
Credit facilities outstanding	$ 468,388	£ 10,000
Wells Fargo | Uncommitted Standby Letter of Credit Facility | Letter of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	101,679
Citibank Europe PLC | Bilateral Facility | Letter of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	186,709
Bank Of Montreal, Citibank Europe and ING Bank | Renaissance Reinsurance FAL Facility | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	180,000
Bank Of Montreal, Citibank Europe and ING Bank | Specialty Risks FAL Facility | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding | £		£ 10,000
Revolving Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	$ 0

Noncontrolling Interests (Detai

Noncontrolling Interests (Details) - USD ($) $ in Thousands	Oct. 01, 2017	Jul. 31, 2017	Jan. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Jul. 01, 2017	Jan. 01, 2017	Dec. 31, 2016
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests				$ 1,425,364		$ 1,296,506
Net income attributable to redeemable noncontrolling interests				29,899	$ 34,327
DaVinciRe Holdings Ltd.
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests				1,032,543	986,646	$ 1,011,659			$ 994,458
Net income attributable to redeemable noncontrolling interests				$ 20,953	31,909
Parent company ownership in redeemable noncontrolling interest	22.10%			22.10%		22.10%	23.50%	22.60%
Redeemable noncontrolling interest, net redemptions			$ 75,000
Redeemable noncontrolling interest, reserve holdback			7,500
Noncontrolling interest, change from purchase or sale of interests	$ 49,700	$ 12,000	$ 24,000
Issuance of equity to third party investors	$ 248,600
Sale of shares to redeemable noncontrolling interest				$ 0	23,921
Redemption of shares from redeemable noncontrolling interest				$ 69	63,642
DaVinciRe Holdings Ltd. | Maximum
Redeemable Noncontrolling Interest [Line Items]
Share repurchase requests, limit				25.00%
RenaissanceRe Medici Fund Ltd.
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests				$ 392,821	201,345	$ 284,847			$ 181,136
Net income attributable to redeemable noncontrolling interests				$ 8,946	2,418
Parent company ownership in redeemable noncontrolling interest				17.10%		26.80%
Redemption provision, notice period				30 days
Sale of shares to redeemable noncontrolling interest				$ 99,739	28,416	$ 149,200
Redemption of shares from redeemable noncontrolling interest				$ 711	$ 10,625	$ 48,000

Noncontrolling Interests (Sched

Noncontrolling Interests (Schedule Of Redeemable Noncontrolling Interest) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Activity in redeemable noncontrolling interest
Beginning balance	$ 1,296,506
Net income attributable to redeemable noncontrolling interest	29,899	$ 34,327
Ending balance	1,425,364		$ 1,296,506
DaVinciRe Holdings Ltd.
Activity in redeemable noncontrolling interest
Beginning balance	1,011,659	994,458	994,458
Redemption of shares from redeemable noncontrolling interest, net of adjustments	(69)	(63,642)
Sale of shares to redeemable noncontrolling interests	0	23,921
Net income attributable to redeemable noncontrolling interest	20,953	31,909
Ending balance	1,032,543	986,646	1,011,659
RenaissanceRe Medici Fund Ltd.
Activity in redeemable noncontrolling interest
Beginning balance	284,847	181,136	181,136
Redemption of shares from redeemable noncontrolling interest, net of adjustments	(711)	(10,625)	(48,000)
Sale of shares to redeemable noncontrolling interests	99,739	28,416	149,200
Net income attributable to redeemable noncontrolling interest	8,946	2,418
Ending balance	$ 392,821	$ 201,345	$ 284,847

Variable Interest Entities (Det

Variable Interest Entities (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Variable Interest Entity [Line Items]
Assets	$ 15,922,202,000		$ 15,226,131,000
Liabilities	10,060,585,000		9,538,250,000
Ceded premiums written	496,608,000	$ 377,954,000
Ceded premiums earned	235,233,000	191,122,000
Investments in other ventures, under equity method	120,232,000		101,974,000
Upsilon RFO Re Ltd. | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Return of capital			84,300,000
Assets	1,400,000,000		1,200,000,000
Liabilities	1,400,000,000		1,200,000,000
Upsilon RFO Re Ltd. | Variable Interest Entity, Primary Beneficiary | Non-Voting Preference Shares
Variable Interest Entity [Line Items]
Issuance of equity to third party investors			180,600,000
Contributions to subsidiaries	$ 75,000,000		27,200,000
Upsilon RFO Re Ltd. | Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd.
Variable Interest Entity [Line Items]
Return of capital			$ 33,000,000
Variable interest entity, ownership percentage	14.10%		20.80%
Upsilon RFO Re Ltd. | Variable Interest Entity, Primary Beneficiary | Third party investor | Non-Voting Preference Shares
Variable Interest Entity [Line Items]
Contributions to subsidiaries	$ 600,500,000		$ 7,500,000
Renaissance Reinsurance Ltd. | Variable Interest Entity, Primary Beneficiary | Fibonacci Reinsurance Ltd.
Variable Interest Entity [Line Items]
Ceded premiums written	4,100,000	7,400,000
Ceded premiums earned	1,200,000	1,800,000
Mona Lisa Re Ltd | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	25,600,000		25,900,000
Liabilities	25,600,000		25,900,000
Mona Lisa Re Ltd | Variable Interest Entity, Not Primary Beneficiary | Renaissance Reinsurance Ltd.
Variable Interest Entity [Line Items]
Ceded premiums written	200,000	100,000
Ceded premiums earned	100,000	1,800,000
Mona Lisa Re Ltd | Variable Interest Entity, Not Primary Beneficiary | DaVinci Reinsurance Ltd.
Variable Interest Entity [Line Items]
Ceded premiums written	200,000	37,000
Ceded premiums earned	100,000	$ 1,300,000
Fibonacci Reinsurance Ltd. | Variable Interest Entity, Primary Beneficiary | Other Investments
Variable Interest Entity [Line Items]
Investment in participating notes	11,100,000		14,100,000
Langhorne Holdings LLC | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Investments in other ventures, under equity method	1,300,000		600,000
Langhorne Partners
Variable Interest Entity [Line Items]
Investments in other ventures, under equity method	$ 100,000
Langhorne Partners | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Investments in other ventures, under equity method			$ 0

Shareholders' Equity (Details)

Shareholders' Equity (Details) - USD ($)	Mar. 29, 2018	Mar. 15, 2018	Mar. 31, 2018	Mar. 31, 2017	Nov. 10, 2017
Class of Stock [Line Items]
Dividends declared per common share (in dollars per share)			$ 0.33	$ 0.32
Dividends declared and paid, preference shares			$ 5,595,000	$ 5,595,000
Retained Earnings
Class of Stock [Line Items]
Dividends declared and paid, preference shares			5,595,000	5,595,000
Dividends declared and paid, common shares			13,224,000	$ 13,027,000
Common Shares
Class of Stock [Line Items]
Dividends declared per common share (in dollars per share)		$ 0.33
Dividends paid per common share (in dollars per share)	$ 0.33
Share repurchase program, authorized amount					$ 500,000,000
Share repurchase program, remaining authorized aggregate amount			$ 500,000,000
Series C Preference Shares
Class of Stock [Line Items]
Dividend rate, percentage			6.08%
Liquidation preference per annum (in dollars per share)			$ 1.52
Liquidation preference quarterly (in dollars per share)			$ 0.38
Series E Preference Shares
Class of Stock [Line Items]
Dividend rate, percentage			5.375%
Liquidation preference per annum (in dollars per share)			$ 1.34375
Liquidation preference quarterly (in dollars per share)			$ 0.3359375

Earnings Per Share (Computation

Earnings Per Share (Computation Of Basic And Diluted Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income available to RenaissanceRe common shareholders	$ 56,713	$ 92,352
Amount allocated to participating common shareholders	(546)	(907)
Net income allocated to RenaissanceRe common shareholders	$ 56,167	$ 91,445
Denominator:
Denominator for basic income per RenaissanceRe common share - weighted average common shares (in shares)	39,552	40,408
Per common share equivalents of employee stock options and restricted shares (in shares)	47	215
Denominator for diluted income per RenaissanceRe common share - adjusted weighted average common shares and assumed conversions (in shares)	39,599	40,623
Net income available to RenaissanceRe common shareholders per common share – basic (in dollars per share)	$ 1.42	$ 2.26
Net income available to RenaissanceRe common shareholders per common share – diluted (in dollars per share)	$ 1.42	$ 2.25

Segment Reporting (Schedule Of

Segment Reporting (Schedule Of Significant Components Of The Company's Revenues And Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Gross premiums written	$ 1,159,652	$ 922,090
Net premiums written	663,044	544,136
Net premiums earned	440,282	366,045
Net claims and claim expenses incurred	171,703	193,081
Acquisition expenses	97,711	83,282
Operational expenses	41,272	47,283
Underwriting income (loss)	129,596	42,399
Net investment income	56,476	54,325
Net foreign exchange gains	3,757	8,165
Equity in earnings (losses) of other ventures	857	(1,507)
Other (loss) income	(1,242)	1,665
Net realized and unrealized (losses) gains on investments	(82,144)	43,373
Corporate expenses	(6,733)	(5,286)
Interest expense	(11,767)	(10,526)
Income before taxes	88,800	132,608
Income tax benefit (expense)	3,407	(334)
Net income attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Dividends on preference shares	(5,595)	(5,595)
Net income available to RenaissanceRe common shareholders	56,713	92,352
Net claims and claim expenses incurred – current accident year	203,038	164,075
Net claims and claim expenses incurred – prior accident years	(31,335)	29,006
Total net incurred	$ 171,703	$ 193,081
Net claims and claim expense ratio – current accident year	46.10%	44.80%
Net claims and claim expense ratio – prior accident years	(7.10%)	7.90%
Net claims and claim expense ratio – calendar year	39.00%	52.70%
Underwriting expense ratio	31.60%	35.70%
Combined ratio	70.60%	88.40%
Other
Segment Reporting Information [Line Items]
Gross premiums written	$ 0	$ 0
Net premiums written	0	0
Net premiums earned	0	(2)
Net claims and claim expenses incurred	18	(328)
Acquisition expenses	0	0
Operational expenses	133	11
Underwriting income (loss)	(151)	315
Net investment income	56,476	54,325
Net foreign exchange gains	3,757	8,165
Equity in earnings (losses) of other ventures	857	(1,507)
Other (loss) income	(1,242)	1,665
Net realized and unrealized (losses) gains on investments	(82,144)	43,373
Corporate expenses	(6,733)	(5,286)
Interest expense	(11,767)	(10,526)
Income tax benefit (expense)	3,407	(334)
Net income attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Dividends on preference shares	(5,595)	(5,595)
Net claims and claim expenses incurred – current accident year	0	0
Net claims and claim expenses incurred – prior accident years	18	(328)
Total net incurred	18	(328)
Property
Segment Reporting Information [Line Items]
Net claims and claim expenses incurred – prior accident years	(27,562)	(928)
Property | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written	706,968	520,529
Net premiums written	354,077	289,871
Net premiums earned	225,049	186,988
Net claims and claim expenses incurred	30,607	38,838
Acquisition expenses	40,721	29,103
Operational expenses	26,546	27,665
Underwriting income (loss)	127,175	91,382
Net claims and claim expenses incurred – current accident year	58,169	39,766
Net claims and claim expenses incurred – prior accident years	(27,562)	(928)
Total net incurred	$ 30,607	$ 38,838
Net claims and claim expense ratio – current accident year	25.80%	21.30%
Net claims and claim expense ratio – prior accident years	(12.20%)	(0.50%)
Net claims and claim expense ratio – calendar year	13.60%	20.80%
Underwriting expense ratio	29.90%	30.30%
Combined ratio	43.50%	51.10%
Casualty and Specialty
Segment Reporting Information [Line Items]
Net claims and claim expenses incurred – prior accident years	$ (3,791)	$ 30,262
Casualty and Specialty | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written	452,684	401,561
Net premiums written	308,967	254,265
Net premiums earned	215,233	179,059
Net claims and claim expenses incurred	141,078	154,571
Acquisition expenses	56,990	54,179
Operational expenses	14,593	19,607
Underwriting income (loss)	2,572	(49,298)
Net claims and claim expenses incurred – current accident year	144,869	124,309
Net claims and claim expenses incurred – prior accident years	(3,791)	30,262
Total net incurred	$ 141,078	$ 154,571
Net claims and claim expense ratio – current accident year	67.30%	69.40%
Net claims and claim expense ratio – prior accident years	(1.80%)	16.90%
Net claims and claim expense ratio – calendar year	65.50%	86.30%
Underwriting expense ratio	33.30%	41.20%
Combined ratio	98.80%	127.50%

Derivative Instruments (Consoli

Derivative Instruments (Consolidated Balance Sheets And Fair Value Of The Principal Derivative Instruments) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other assets
Derivative Assets
Gross Amounts of Recognized Assets	$ 9,281	$ 6,530
Gross Amounts Offset in the Balance Sheet	410	893
Net Amounts of Assets Presented in the Balance Sheet	8,871	5,637
Collateral	0	0
Net Amount	8,871	5,637
Other assets | Interest rate futures
Derivative Assets
Gross Amounts of Recognized Assets	175	684
Gross Amounts Offset in the Balance Sheet	157	524
Net Amounts of Assets Presented in the Balance Sheet	18	160
Collateral	0	0
Net Amount	18	160
Other assets | Interest rate swaps
Derivative Assets
Gross Amounts of Recognized Assets	357	424
Gross Amounts Offset in the Balance Sheet	0	0
Net Amounts of Assets Presented in the Balance Sheet	357	424
Collateral	0	0
Net Amount	357	424
Other assets | Foreign currency forward contracts, underwriting and non-investment operations
Derivative Assets
Gross Amounts of Recognized Assets	7,070	3,865
Gross Amounts Offset in the Balance Sheet	175	358
Net Amounts of Assets Presented in the Balance Sheet	6,895	3,507
Collateral	0	0
Net Amount	6,895	3,507
Other assets | Foreign currency forward contracts, investment operations
Derivative Assets
Gross Amounts of Recognized Assets	79	39
Gross Amounts Offset in the Balance Sheet	78	11
Net Amounts of Assets Presented in the Balance Sheet	1	28
Collateral	0	0
Net Amount	1	28
Other assets | Credit default swaps
Derivative Assets
Gross Amounts of Recognized Assets	1,600	1,518
Gross Amounts Offset in the Balance Sheet	0	0
Net Amounts of Assets Presented in the Balance Sheet	1,600	1,518
Collateral	0	0
Net Amount	1,600	1,518
Other liabilities
Derivative Liabilities
Gross Amounts of Recognized Liabilities	1,592	1,536
Gross Amounts Offset in the Balance Sheet	235	535
Net Amounts of Liabilities Presented in the Balance Sheet	1,357	1,001
Collateral Pledged	313	227
Net Amount	1,044	774
Other liabilities | Interest rate futures
Derivative Liabilities
Gross Amounts of Recognized Liabilities	404	729
Gross Amounts Offset in the Balance Sheet	157	524
Net Amounts of Liabilities Presented in the Balance Sheet	247	205
Collateral Pledged	247	205
Net Amount	0	0
Other liabilities | Interest rate swaps
Derivative Liabilities
Gross Amounts of Recognized Liabilities	53
Gross Amounts Offset in the Balance Sheet	0
Net Amounts of Liabilities Presented in the Balance Sheet	53
Collateral Pledged	53
Net Amount	0
Other liabilities | Foreign currency forward contracts, underwriting and non-investment operations
Derivative Liabilities
Gross Amounts of Recognized Liabilities	479	670
Gross Amounts Offset in the Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Balance Sheet	479	670
Collateral Pledged	0	0
Net Amount	479	670
Other liabilities | Foreign currency forward contracts, investment operations
Derivative Liabilities
Gross Amounts of Recognized Liabilities	643	115
Gross Amounts Offset in the Balance Sheet	78	11
Net Amounts of Liabilities Presented in the Balance Sheet	565	104
Collateral Pledged	0	0
Net Amount	565	104
Other liabilities | Credit default swaps
Derivative Liabilities
Gross Amounts of Recognized Liabilities	13	22
Gross Amounts Offset in the Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Balance Sheet	13	22
Collateral Pledged	13	22
Net Amount	$ 0	$ 0

Derivative Instruments (Gain (L

Derivative Instruments (Gain (Loss) Recognized In The Consolidated Statements Of Operations Related To Its Derivative Instruments) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	$ 1,688	$ 371
Net realized and unrealized (losses) gains on investments | Interest rate futures
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	(2,337)	(158)
Net realized and unrealized (losses) gains on investments | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	(106)	0
Net realized and unrealized (losses) gains on investments | Credit default swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	(1,921)	102
Net foreign exchange gains | Foreign currency forward contracts, underwriting and non-investment operations
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	6,743	1,060
Net foreign exchange gains | Foreign currency forward contracts, investment operations
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	$ (691)	$ (633)

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - Not Designated as Hedging Instrument - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Interest rate futures | Long
Derivative [Line Items]
Notional amount	$ 1,500,000,000	$ 1,500,000,000
Interest rate futures | Short
Derivative [Line Items]
Notional amount	812,700,000	801,100,000
Interest rate swaps | US Dollars | Paying a Fixed Rate
Derivative [Line Items]
Notional amount	22,900,000	40,300,000
Interest rate swaps | US Dollars | Receiving a Fixed Rate
Derivative [Line Items]
Notional amount	6,900,000	0
Foreign currency forward contracts, underwriting and non-investment operations | Long
Derivative [Line Items]
Notional amount	218,600,000	215,400,000
Foreign currency forward contracts, underwriting and non-investment operations | Short
Derivative [Line Items]
Notional amount	25,400,000	44,200,000
Foreign currency forward contracts, investment operations | Long
Derivative [Line Items]
Notional amount	66,400,000	16,600,000
Foreign currency forward contracts, investment operations | Short
Derivative [Line Items]
Notional amount	40,500,000	5,100,000
Credit default swaps | Long
Derivative [Line Items]
Notional amount	1,000,000	1,000,000
Credit default swaps | Short
Derivative [Line Items]
Notional amount	$ 41,100,000	$ 18,800,000

Condensed Consolidating Finan66

Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Assets
Total investments	$ 10,221,704	$ 9,503,439
Cash and cash equivalents	647,973	1,361,592	$ 454,087	$ 421,157
Investments in subsidiaries	0	0
Due from subsidiaries and affiliates	0	0
Premiums receivable	1,684,630	1,304,622
Prepaid reinsurance premiums	794,921	533,546
Reinsurance recoverable	1,572,321	1,586,630	325,819
Accrued investment income	43,069	42,235
Deferred acquisition costs	477,010	426,551
Receivable for investments sold	111,431	103,145
Other assets	127,571	121,226
Goodwill and other intangible assets	241,572	243,145
Total assets	15,922,202	15,226,131
Liabilities
Reserve for claims and claim expenses	4,912,727	5,080,408	2,934,688
Unearned premiums	1,961,746	1,477,609
Debt	989,995	989,623
Amounts due to subsidiaries and affiliates	0	0
Reinsurance balances payable	1,758,948	989,090
Payable for investments purchased	306,664	208,749
Other liabilities	130,505	792,771
Total liabilities	10,060,585	9,538,250
Redeemable noncontrolling interests	1,425,364	1,296,506
Shareholders’ Equity
Total shareholders’ equity	4,436,253	4,391,375	4,860,837
Total liabilities, noncontrolling interests and shareholders’ equity	15,922,202	15,226,131
Reportable Legal Entities | RenRe North America Holdings Inc. (Subsidiary Issuer)
Assets
Total investments	112,716	129,732
Cash and cash equivalents	97	139	164	162
Investments in subsidiaries	53,476	36,140
Due from subsidiaries and affiliates	91,891	91,891
Premiums receivable	0	0
Prepaid reinsurance premiums	0	0
Reinsurance recoverable	0	0
Accrued investment income	223	428
Deferred acquisition costs	0	0
Receivable for investments sold	0	51
Other assets	21,340	21,342
Goodwill and other intangible assets	0	0
Total assets	279,743	279,723
Liabilities
Reserve for claims and claim expenses	0	0
Unearned premiums	0	0
Debt	0	0
Amounts due to subsidiaries and affiliates	61	54
Reinsurance balances payable	0	0
Payable for investments purchased	0	0
Other liabilities	793	1,053
Total liabilities	854	1,107
Redeemable noncontrolling interests	0	0
Shareholders’ Equity
Total shareholders’ equity	278,889	278,616
Total liabilities, noncontrolling interests and shareholders’ equity	279,743	279,723
Reportable Legal Entities | RenaissanceRe Finance, Inc. (Subsidiary Issuer)
Assets
Total investments	22,433	31,255
Cash and cash equivalents	1,175	1,469	6,080	9,397
Investments in subsidiaries	1,137,922	1,141,733
Due from subsidiaries and affiliates	0	0
Premiums receivable	0	0
Prepaid reinsurance premiums	0	0
Reinsurance recoverable	0	0
Accrued investment income	46	82
Deferred acquisition costs	0	0
Receivable for investments sold	6	8
Other assets	433,056	430,481
Goodwill and other intangible assets	0	0
Total assets	1,594,638	1,605,028
Liabilities
Reserve for claims and claim expenses	0	0
Unearned premiums	0	0
Debt	842,188	841,892
Amounts due to subsidiaries and affiliates	106,900	92,794
Reinsurance balances payable	0	0
Payable for investments purchased	0	0
Other liabilities	9,457	14,117
Total liabilities	958,545	948,803
Redeemable noncontrolling interests	0	0
Shareholders’ Equity
Total shareholders’ equity	636,093	656,225
Total liabilities, noncontrolling interests and shareholders’ equity	1,594,638	1,605,028
Reportable Legal Entities | RenaissanceRe Holdings Ltd. (Parent Guarantor)
Assets
Total investments	70,641	225,266
Cash and cash equivalents	8,150	14,656	4,177	7,067
Investments in subsidiaries	4,090,065	4,105,760
Due from subsidiaries and affiliates	137,639	4,602
Premiums receivable	0	0
Prepaid reinsurance premiums	0	0
Reinsurance recoverable	0	0
Accrued investment income	16	405
Deferred acquisition costs	0	0
Receivable for investments sold	48	135
Other assets	439,667	433,468
Goodwill and other intangible assets	123,728	124,960
Total assets	4,869,954	4,909,252
Liabilities
Reserve for claims and claim expenses	0	0
Unearned premiums	0	0
Debt	417,000	417,000
Amounts due to subsidiaries and affiliates	9,639	82,579
Reinsurance balances payable	0	0
Payable for investments purchased	0	0
Other liabilities	7,062	18,298
Total liabilities	433,701	517,877
Redeemable noncontrolling interests	0	0
Shareholders’ Equity
Total shareholders’ equity	4,436,253	4,391,375
Total liabilities, noncontrolling interests and shareholders’ equity	4,869,954	4,909,252
Reportable Legal Entities | Other RenaissanceRe Holdings Ltd. Subsidiaries And Eliminations (Non-Guarantor Subsidiaries)
Assets
Total investments	10,015,914	9,117,186
Cash and cash equivalents	638,551	1,345,328	$ 439,502	$ 397,860
Investments in subsidiaries	0	0
Due from subsidiaries and affiliates	0	0
Premiums receivable	1,684,630	1,304,622
Prepaid reinsurance premiums	794,921	533,546
Reinsurance recoverable	1,572,321	1,586,630
Accrued investment income	42,784	41,320
Deferred acquisition costs	477,010	426,551
Receivable for investments sold	111,377	102,951
Other assets	82,133	76,703
Goodwill and other intangible assets	117,844	118,185
Total assets	15,537,485	14,653,022
Liabilities
Reserve for claims and claim expenses	4,912,727	5,080,408
Unearned premiums	1,961,746	1,477,609
Debt	147,807	147,731
Amounts due to subsidiaries and affiliates	0	0
Reinsurance balances payable	1,758,948	989,090
Payable for investments purchased	306,664	208,749
Other liabilities	119,676	764,432
Total liabilities	9,207,568	8,668,019
Redeemable noncontrolling interests	1,425,364	1,296,506
Shareholders’ Equity
Total shareholders’ equity	4,904,553	4,688,497
Total liabilities, noncontrolling interests and shareholders’ equity	15,537,485	14,653,022
Consolidating Adjustments
Assets
Total investments	0	0
Cash and cash equivalents	0	0
Investments in subsidiaries	(5,281,463)	(5,283,633)
Due from subsidiaries and affiliates	(229,530)	(96,493)
Premiums receivable	0	0
Prepaid reinsurance premiums	0	0
Reinsurance recoverable	0	0
Accrued investment income	0	0
Deferred acquisition costs	0	0
Receivable for investments sold	0	0
Other assets	(848,625)	(840,768)
Goodwill and other intangible assets	0	0
Total assets	(6,359,618)	(6,220,894)
Liabilities
Reserve for claims and claim expenses	0	0
Unearned premiums	0	0
Debt	(417,000)	(417,000)
Amounts due to subsidiaries and affiliates	(116,600)	(175,427)
Reinsurance balances payable	0	0
Payable for investments purchased	0	0
Other liabilities	(6,483)	(5,129)
Total liabilities	(540,083)	(597,556)
Redeemable noncontrolling interests	0	0
Shareholders’ Equity
Total shareholders’ equity	(5,819,535)	(5,623,338)
Total liabilities, noncontrolling interests and shareholders’ equity	$ (6,359,618)	$ (6,220,894)

Condensed Consolidating Finan67

Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues
Net premiums earned	$ 440,282	$ 366,045
Net investment income	56,476	54,325
Net foreign exchange (losses) gains	3,757	8,165
Equity in earnings (losses) of other ventures	857	(1,507)
Other (loss) income	(1,242)	1,665
Net realized and unrealized (losses) gains on investments	(82,144)	43,373
Total revenues	417,986	472,066
Expenses
Net claims and claim expenses incurred	171,703	193,081
Acquisition expenses	97,711	83,282
Operational expenses	41,272	47,283
Corporate expenses	6,733	5,286
Interest expense	11,767	10,526
Total expenses	329,186	339,458
(Loss) income before equity in net income (loss) of subsidiaries and taxes	88,800	132,608
Equity in net income (loss) of subsidiaries	0	0
Income before taxes	88,800	132,608
Income tax benefit (expense)	3,407	(334)
Net income	92,207	132,274
Net (income) loss attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Net income attributable to RenaissanceRe	62,308	97,947
Dividends on preference shares	(5,595)	(5,595)
Net income available to RenaissanceRe common shareholders	56,713	92,352
Reportable Legal Entities | RenRe North America Holdings Inc. (Subsidiary Issuer)
Revenues
Net premiums earned	0	0
Net investment income	513	426
Net foreign exchange (losses) gains	0	0
Equity in earnings (losses) of other ventures	0	0
Other (loss) income	0	0
Net realized and unrealized (losses) gains on investments	(1,286)	2,921
Total revenues	(773)	3,347
Expenses
Net claims and claim expenses incurred	0	0
Acquisition expenses	0	0
Operational expenses	10	24
Corporate expenses	0	0
Interest expense	0	0
Total expenses	10	24
(Loss) income before equity in net income (loss) of subsidiaries and taxes	(783)	3,323
Equity in net income (loss) of subsidiaries	834	1,086
Income before taxes	51	4,409
Income tax benefit (expense)	221	(1,098)
Net income	272	3,311
Net (income) loss attributable to redeemable noncontrolling interests	0	0
Net income attributable to RenaissanceRe	272	3,311
Dividends on preference shares	0	0
Net income available to RenaissanceRe common shareholders	272	3,311
Reportable Legal Entities | Platinum Underwriters Finance, Inc. (Subsidiary Issuer)
Revenues
Net premiums earned		0
Net investment income		841
Net foreign exchange (losses) gains		0
Equity in earnings (losses) of other ventures		0
Other (loss) income		0
Net realized and unrealized (losses) gains on investments		4,725
Total revenues		5,566
Expenses
Net claims and claim expenses incurred		0
Acquisition expenses		0
Operational expenses		50
Corporate expenses		0
Interest expense		1,476
Total expenses		1,526
(Loss) income before equity in net income (loss) of subsidiaries and taxes		4,040
Equity in net income (loss) of subsidiaries		9,843
Income before taxes		13,883
Income tax benefit (expense)		(1,308)
Net income		12,575
Net (income) loss attributable to redeemable noncontrolling interests		0
Net income attributable to RenaissanceRe		12,575
Dividends on preference shares		0
Net income available to RenaissanceRe common shareholders		12,575
Reportable Legal Entities | RenaissanceRe Finance, Inc. (Subsidiary Issuer)
Revenues
Net premiums earned	0	0
Net investment income	1,234	269
Net foreign exchange (losses) gains	0	0
Equity in earnings (losses) of other ventures	1,211	(752)
Other (loss) income	0	0
Net realized and unrealized (losses) gains on investments	(259)	(26)
Total revenues	2,186	(509)
Expenses
Net claims and claim expenses incurred	0	0
Acquisition expenses	0	0
Operational expenses	11,070	7,979
Corporate expenses	0	0
Interest expense	9,252	6,542
Total expenses	20,322	14,521
(Loss) income before equity in net income (loss) of subsidiaries and taxes	(18,136)	(15,030)
Equity in net income (loss) of subsidiaries	(3,813)	16,498
Income before taxes	(21,949)	1,468
Income tax benefit (expense)	1,815	3,072
Net income	(20,134)	4,540
Net (income) loss attributable to redeemable noncontrolling interests	0	0
Net income attributable to RenaissanceRe	(20,134)	4,540
Dividends on preference shares	0	0
Net income available to RenaissanceRe common shareholders	(20,134)	4,540
Reportable Legal Entities | RenaissanceRe Holdings Ltd. (Parent Guarantor)
Revenues
Net premiums earned	0	0
Net investment income	6,035	5,457
Net foreign exchange (losses) gains	(3)	0
Equity in earnings (losses) of other ventures	0	0
Other (loss) income	0	(1)
Net realized and unrealized (losses) gains on investments	(661)	53
Total revenues	5,371	5,509
Expenses
Net claims and claim expenses incurred	0	0
Acquisition expenses	0	0
Operational expenses	1,313	3,298
Corporate expenses	3,684	5,208
Interest expense	1,108	140
Total expenses	6,105	8,646
(Loss) income before equity in net income (loss) of subsidiaries and taxes	(734)	(3,137)
Equity in net income (loss) of subsidiaries	62,426	101,353
Income before taxes	61,692	98,216
Income tax benefit (expense)	616	(269)
Net income	62,308	97,947
Net (income) loss attributable to redeemable noncontrolling interests	0	0
Net income attributable to RenaissanceRe	62,308	97,947
Dividends on preference shares	(5,595)	(5,595)
Net income available to RenaissanceRe common shareholders	56,713	92,352
Reportable Legal Entities | Other RenaissanceRe Holdings Ltd. Subsidiaries And Eliminations (Non-Guarantor Subsidiaries)
Revenues
Net premiums earned	440,282	366,045
Net investment income	56,305	53,583
Net foreign exchange (losses) gains	3,760	8,165
Equity in earnings (losses) of other ventures	(354)	(755)
Other (loss) income	(1,242)	1,666
Net realized and unrealized (losses) gains on investments	(79,938)	35,700
Total revenues	418,813	464,404
Expenses
Net claims and claim expenses incurred	171,703	193,081
Acquisition expenses	97,711	83,282
Operational expenses	37,933	42,058
Corporate expenses	3,049	78
Interest expense	2,515	2,508
Total expenses	312,911	321,007
(Loss) income before equity in net income (loss) of subsidiaries and taxes	105,902	143,397
Equity in net income (loss) of subsidiaries	0	0
Income before taxes	105,902	143,397
Income tax benefit (expense)	755	(731)
Net income	106,657	142,666
Net (income) loss attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Net income attributable to RenaissanceRe	76,758	108,339
Dividends on preference shares	0	0
Net income available to RenaissanceRe common shareholders	76,758	108,339
Consolidating Adjustments
Revenues
Net premiums earned	0	0
Net investment income	(7,611)	(6,251)
Net foreign exchange (losses) gains	0	0
Equity in earnings (losses) of other ventures	0	0
Other (loss) income	0	0
Net realized and unrealized (losses) gains on investments	0	0
Total revenues	(7,611)	(6,251)
Expenses
Net claims and claim expenses incurred	0	0
Acquisition expenses	0	0
Operational expenses	(9,054)	(6,126)
Corporate expenses	0	0
Interest expense	(1,108)	(140)
Total expenses	(10,162)	(6,266)
(Loss) income before equity in net income (loss) of subsidiaries and taxes	2,551	15
Equity in net income (loss) of subsidiaries	(59,447)	(128,780)
Income before taxes	(56,896)	(128,765)
Income tax benefit (expense)	0	0
Net income	(56,896)	(128,765)
Net (income) loss attributable to redeemable noncontrolling interests	0	0
Net income attributable to RenaissanceRe	(56,896)	(128,765)
Dividends on preference shares	0	0
Net income available to RenaissanceRe common shareholders	$ (56,896)	$ (128,765)

Condensed Consolidating Finan68

Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Net income	$ 92,207	$ 132,274
Change in net unrealized gains on investments	(30)	(1,491)
Comprehensive income	92,177	130,783
Net income attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Comprehensive loss attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Comprehensive income attributable to RenaissanceRe	62,278	96,456
Reportable Legal Entities | RenRe North America Holdings Inc. (Subsidiary Issuer)
Condensed Financial Statements, Captions [Line Items]
Net income	272	3,311
Change in net unrealized gains on investments	0	0
Comprehensive income	272	3,311
Net income attributable to redeemable noncontrolling interests	0	0
Comprehensive loss attributable to redeemable noncontrolling interests	0	0
Comprehensive income attributable to RenaissanceRe	272	3,311
Reportable Legal Entities | Platinum Underwriters Finance, Inc. (Subsidiary Issuer)
Condensed Financial Statements, Captions [Line Items]
Net income		12,575
Change in net unrealized gains on investments		0
Comprehensive income		12,575
Net income attributable to redeemable noncontrolling interests		0
Comprehensive loss attributable to redeemable noncontrolling interests		0
Comprehensive income attributable to RenaissanceRe		12,575
Reportable Legal Entities | RenaissanceRe Finance, Inc. (Subsidiary Issuer)
Condensed Financial Statements, Captions [Line Items]
Net income	(20,134)	4,540
Change in net unrealized gains on investments	0	0
Comprehensive income	(20,134)	4,540
Net income attributable to redeemable noncontrolling interests	0	0
Comprehensive loss attributable to redeemable noncontrolling interests	0	0
Comprehensive income attributable to RenaissanceRe	(20,134)	4,540
Reportable Legal Entities | RenaissanceRe Holdings Ltd. (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Net income	62,308	97,947
Change in net unrealized gains on investments	0	0
Comprehensive income	62,308	97,947
Net income attributable to redeemable noncontrolling interests	0	0
Comprehensive loss attributable to redeemable noncontrolling interests	0	0
Comprehensive income attributable to RenaissanceRe	62,308	97,947
Reportable Legal Entities | Other RenaissanceRe Holdings Ltd. Subsidiaries And Eliminations (Non-Guarantor Subsidiaries)
Condensed Financial Statements, Captions [Line Items]
Net income	106,657	142,666
Change in net unrealized gains on investments	(30)	(1,491)
Comprehensive income	106,627	141,175
Net income attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Comprehensive loss attributable to redeemable noncontrolling interests	(29,899)	(34,327)
Comprehensive income attributable to RenaissanceRe	76,728	106,848
Consolidating Adjustments
Condensed Financial Statements, Captions [Line Items]
Net income	(56,896)	(128,765)
Change in net unrealized gains on investments	0	0
Comprehensive income	(56,896)	(128,765)
Net income attributable to redeemable noncontrolling interests	0	0
Comprehensive loss attributable to redeemable noncontrolling interests	0	0
Comprehensive income attributable to RenaissanceRe	$ (56,896)	$ (128,765)

Condensed Consolidating Finan69

Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	$ (37,349)	$ 201,039
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	2,318,859	2,682,386
Purchases of fixed maturity investments trading	(2,312,461)	(3,007,124)
Net (purchases) sales of equity investments trading	137	13,747
Net (purchases) sales of short term investments	(594,641)	245,693
Net sales of other investments	(98,639)	36,402
Return of investment from investment in other ventures	0	20,000
Dividends and return of capital from subsidiaries	0	0
Contributions to subsidiaries	0	0
Due to (from) subsidiary	0	0
Net cash used in investing activities	(704,719)	(8,896)
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	(13,224)	(13,027)
Dividends paid – preference shares	(5,595)	(5,595)
RenaissanceRe common share repurchases	0	(80,009)
Net third party redeemable noncontrolling interest share transactions	52,759	(51,166)
Taxes paid on withholding shares	(7,034)	(11,018)
Net cash provided by (used in) financing activities	26,906	(160,815)
Effect of exchange rate changes on foreign currency cash	1,543	1,602
Net (decrease) increase in cash and cash equivalents	(713,619)	32,930
Cash and cash equivalents, beginning of period	1,361,592	421,157
Cash and cash equivalents, end of period	647,973	454,087
Reportable Legal Entities | RenRe North America Holdings Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	659	(8,594)
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	42,793	12,473
Purchases of fixed maturity investments trading	(22,956)	(12,438)
Net (purchases) sales of equity investments trading	(21)	(74)
Net (purchases) sales of short term investments	(4,024)	(590)
Net sales of other investments	0	0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries	0	9,175
Contributions to subsidiaries	(16,500)	0
Due to (from) subsidiary	7	50
Net cash used in investing activities	(701)	8,596
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions	0	0
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	0	0
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	(42)	2
Cash and cash equivalents, beginning of period	139	162
Cash and cash equivalents, end of period	97	164
Reportable Legal Entities | Platinum Underwriters Finance, Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities		5,188
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading		36,397
Purchases of fixed maturity investments trading		(36,790)
Net (purchases) sales of equity investments trading		(2,181)
Net (purchases) sales of short term investments		(5,087)
Net sales of other investments		0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries		0
Contributions to subsidiaries		0
Due to (from) subsidiary		(34)
Net cash used in investing activities	0	(7,695)
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions		0
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	0	0
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	0	(2,507)
Cash and cash equivalents, beginning of period		6,671
Cash and cash equivalents, end of period	0	4,164
Reportable Legal Entities | RenaissanceRe Finance, Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	(23,449)	(17,914)
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	27,672	15,449
Purchases of fixed maturity investments trading	(12,698)	0
Net (purchases) sales of equity investments trading	0	0
Net (purchases) sales of short term investments	(5,925)	(3,374)
Net sales of other investments	0	0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries	0	9,175
Contributions to subsidiaries	0	(9,175)
Due to (from) subsidiary	14,106	2,522
Net cash used in investing activities	23,155	14,597
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions	0	0
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	0	0
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	(294)	(3,317)
Cash and cash equivalents, beginning of period	1,469	9,397
Cash and cash equivalents, end of period	1,175	6,080
Reportable Legal Entities | RenaissanceRe Holdings Ltd. (Parent Guarantor)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	(6,875)	(12,358)
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	119,542	38,449
Purchases of fixed maturity investments trading	(20,216)	(63,417)
Net (purchases) sales of equity investments trading	0	0
Net (purchases) sales of short term investments	54,728	269,585
Net sales of other investments	0	0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries	177,250	65,180
Contributions to subsidiaries	(150,205)	(162,550)
Due to (from) subsidiary	(154,877)	(28,130)
Net cash used in investing activities	26,222	119,117
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	(13,224)	(13,027)
Dividends paid – preference shares	(5,595)	(5,595)
RenaissanceRe common share repurchases		(80,009)
Net third party redeemable noncontrolling interest share transactions	0	0
Taxes paid on withholding shares	(7,034)	(11,018)
Net cash provided by (used in) financing activities	(25,853)	(109,649)
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	(6,506)	(2,890)
Cash and cash equivalents, beginning of period	14,656	7,067
Cash and cash equivalents, end of period	8,150	4,177
Reportable Legal Entities | Other RenaissanceRe Holdings Ltd. Subsidiaries And Eliminations (Non-Guarantor Subsidiaries)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	(7,684)	234,717
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	2,128,852	2,579,618
Purchases of fixed maturity investments trading	(2,256,591)	(2,894,479)
Net (purchases) sales of equity investments trading	158	16,002
Net (purchases) sales of short term investments	(639,420)	(14,841)
Net sales of other investments	(98,639)	36,402
Return of investment from investment in other ventures		20,000
Dividends and return of capital from subsidiaries	(177,250)	(83,530)
Contributions to subsidiaries	166,705	171,725
Due to (from) subsidiary	140,764	25,592
Net cash used in investing activities	(753,395)	(143,511)
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions	52,759	(51,166)
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	52,759	(51,166)
Effect of exchange rate changes on foreign currency cash	1,543	1,602
Net (decrease) increase in cash and cash equivalents	(706,777)	41,642
Cash and cash equivalents, beginning of period	1,345,328	397,860
Cash and cash equivalents, end of period	$ 638,551	$ 439,502

Subsequent Events (Details)

Subsequent Events (Details) - Upsilon RFO Re Ltd. - Variable Interest Entity, Primary Beneficiary - USD ($) $ in Millions	Apr. 01, 2018	Mar. 31, 2018	Dec. 31, 2017
Non-Voting Preference Shares
Subsequent Event [Line Items]
Issuance of equity to third party investors			$ 180.6
Contributions to subsidiaries		$ 75	$ 27.2
Subsequent Event
Subsequent Event [Line Items]
Contributions to subsidiaries	$ 26.5
Variable interest entity, ownership percentage	16.90%
Subsequent Event | Non-Voting Preference Shares
Subsequent Event [Line Items]
Issuance of equity to third party investors	$ 31.7