Arch Capital (ACGL) 10-Q 9 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 30, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	ARCH CAPITAL GROUP LTD.
Entity Central Index Key	947,484
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		122,450,741

Unaudited Consolidated Balance

Unaudited Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investments:
Fixed maturities available for sale, at fair value (amortized cost: $10,550,931 and $10,701,557)	$ 10,560,635	$ 10,750,770
Short-term investments available for sale, at fair value (amortized cost: $711,390 and $801,758)	708,428	797,226
Collateral received under securities lending, at fair value (amortized cost: $282,783 and $40,473)	286,659	44,301
Equity securities available for sale, at fair value (cost: $575,292 and $562,534)	606,259	658,182
Other investments available for sale, at fair value (cost: $245,356 and $264,747)	281,014	296,224
Investments accounted for using the fair value option	2,783,165	2,425,053
Investments accounted for using the equity method	589,277	349,014
Total investments	15,815,437	15,320,770
Cash	649,779	485,702
Accrued investment income	76,142	74,316
Securities pledged under securities lending, at fair value (amortized cost: $285,979 and $52,076)	285,632	50,802
Premiums receivable	1,074,884	948,695
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	1,832,386	1,812,845
Contractholder receivables	1,436,154	1,309,192
Prepaid reinsurance premiums	442,346	377,078
Deferred acquisition costs, net	448,893	414,525
Receivable for securities sold	705,821	78,170
Goodwill and intangible assets	103,620	109,539
Other assets	899,498	1,024,447
Total assets	23,770,592	22,006,081
Liabilities
Reserve for losses and loss adjustment expenses	9,084,855	9,036,448
Unearned premiums	2,467,691	2,231,578
Reinsurance balances payable	235,562	219,312
Contractholder payables	1,436,154	1,309,192
Collateral held for insured obligations	242,928	184,219
Deposit accounting liabilities	270,876	327,384
Senior notes	791,264	791,141
Revolving credit agreement borrowings	339,077	100,000
Securities lending payable	292,838	50,529
Payable for securities purchased	817,371	128,413
Other liabilities	649,910	509,219
Total liabilities	$ 16,628,526	$ 14,887,435
Commitments and Contingencies
Redeemable noncontrolling interests	$ 205,089	$ 219,512
Shareholders' Equity
Non-cumulative preferred shares	325,000	325,000
Common shares ($0.0033 par, shares issued: 172,903,518 and 171,672,408)	576	572
Additional paid-in capital	450,948	383,073
Retained earnings	7,317,277	6,854,571
Accumulated other comprehensive income, net of deferred income tax	9,809	128,856
Common shares held in treasury, at cost (shares: 50,464,964 and 44,304,474)	(1,940,795)	(1,562,019)
Total shareholders' equity available to Arch	6,162,815	6,130,053
Non-redeemable noncontrolling interests	774,162	769,081
Total shareholders' equity	6,936,977	6,899,134
Total liabilities, noncontrolling interests and shareholders' equity	$ 23,770,592	$ 22,006,081

Unaudited Consolidated Balance3

Unaudited Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fixed maturities available for sale, at amortized cost	$ 10,550,931	$ 10,701,557
Short-term investments available for sale, at amortized cost	711,390	801,758
Collateral received under securities lending, at amortized cost	282,783	40,473
Equity securities available for sale, at cost	575,292	562,534
Other investments available for sale, at cost	245,356	264,747
Securities pledged under securities lending, at amortized cost	$ 285,979	$ 52,076
Common shares, par value per share	$ 0.0033	$ 0.0033
Common shares issued (shares)	172,903,518	171,672,408
Common shares held in treasury (shares)	50,464,964	44,304,474

Unaudited Consolidated Statemen

Unaudited Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues
Net premiums written	$ 971,972	$ 959,539	$ 2,982,547	$ 2,996,457
Change in unearned premiums	(35,289)	(55,888)	(192,162)	(325,874)
Net premiums earned	936,683	903,651	2,790,385	2,670,583
Net investment income	86,233	80,105	252,190	220,089
Net realized gains (losses)	(89,698)	18,515	(42,075)	92,356
Other-than-temporary impairment losses	(8,901)	(8,593)	(17,274)	(26,313)
Less investment impairments recognized in other comprehensive income, before taxes	3,033	0	4,494	0
Net impairment losses recognized in earnings	(5,868)	(8,593)	(12,780)	(26,313)
Other underwriting income	7,623	1,702	26,876	5,317
Equity in net income (loss) of investment funds accounted for using the equity method	(2,118)	4,966	19,938	17,459
Other income (loss)	(265)	(7,815)	52	(5,069)
Total revenues	932,590	992,531	3,034,586	2,974,422
Expenses
Losses and loss adjustment expenses	531,741	501,673	1,544,883	1,423,431
Acquisition expenses	171,566	163,547	510,067	482,047
Other operating expenses	156,959	149,480	483,449	451,629
Interest expense	13,300	4,152	30,047	32,890
Net foreign exchange gains	(14,680)	(56,031)	(61,598)	(47,174)
Total expenses	858,886	762,821	2,506,848	2,342,823
Income before income taxes	73,704	229,710	527,738	631,599
Income tax expense	(9,704)	(6,446)	(29,162)	(17,473)
Net income	64,000	223,264	498,576	614,126
Amounts attributable to noncontrolling interests	16,033	5,411	(19,417)	5,065
Net income available to Arch	80,033	228,675	479,159	619,191
Preferred dividends	(5,484)	(5,484)	(16,453)	(16,453)
Net income available to Arch common shareholders	$ 74,549	$ 223,191	$ 462,706	$ 602,738
Net income per common share
Basic (per share)	$ 0.62	$ 1.69	$ 3.79	$ 4.56
Diluted (per share)	$ 0.60	$ 1.64	$ 3.66	$ 4.42
Weighted average common shares and common share equivalents outstanding
Basic (shares)	120,567,410	131,945,962	122,151,971	132,151,824
Diluted (shares)	125,011,773	135,876,605	126,354,759	136,354,172

Unaudited Consolidated Stateme5

Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Comprehensive Income
Net income	$ 64,000	$ 223,264	$ 498,576	$ 614,126
Unrealized appreciation (decline) in value of available-for-sale investments:
Unrealized holding gains (losses) arising during period	(53,891)	(90,619)	(51,522)	89,162
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(3,033)	0	(4,494)	0
Reclassification of net realized (gains) losses, net of income taxes, included in net income	12,278	(17,483)	(39,868)	(47,017)
Foreign currency translation adjustments	(12,082)	(23,595)	(23,259)	(14,923)
Comprehensive income	7,272	91,567	379,433	641,348
Amounts attributable to noncontrolling interests	16,129	5,411	(19,321)	5,065
Comprehensive income available to Arch	$ 23,401	$ 96,978	$ 360,112	$ 646,413

Unaudited Consolidated Stateme6

Unaudited Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Non-cumulative preferred shares	Common shares	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income	Unrealized gains on available-for-sale securities	Foreign currency translation adjustments	Common shares held in treasury, at cost
Balance at beginning of year at Dec. 31, 2013		$ 325,000	$ 565	$ 299,517	$ 6,042,154	$ 74,964	$ 80,692	$ (5,728)	$ (1,094,704)
Common shares issued, net			6	6,401
Exercise of stock options				14,891
Amortization of share-based compensation				45,118
Other				481
Net income	$ 614,126				614,126
Amounts attributable to noncontrolling interests	5,065				5,065
Preferred share dividends	(16,453)				(16,453)
Unrealized holding (losses) gains arising during period, net of reclassification adjustment							42,145
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	0						0
Foreign currency translation adjustments	(14,923)							(14,923)
Shares repurchased for treasury									(263,307)
Balance at end of period at Sep. 30, 2014	6,081,046	325,000	571	366,408	6,644,892	102,186	122,837	(20,651)	(1,358,011)
Non-redeemable noncontrolling interests, end of period at Sep. 30, 2014	782,020
Total shareholders’ equity at Sep. 30, 2014	6,863,066
Net income	223,264
Amounts attributable to noncontrolling interests	5,411
Preferred share dividends	(5,484)
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	0
Foreign currency translation adjustments	(23,595)
Balance at end of period at Sep. 30, 2014	6,081,046	325,000	571	366,408	6,644,892	102,186	122,837	(20,651)	(1,358,011)
Non-redeemable noncontrolling interests, end of period at Sep. 30, 2014	782,020
Total shareholders’ equity at Sep. 30, 2014	6,863,066
Balance at beginning of year at Dec. 31, 2014	6,130,053	325,000	572	383,073	6,854,571	128,856	161,598	(32,742)	(1,562,019)
Common shares issued, net			4	7,440
Exercise of stock options				12,363
Amortization of share-based compensation				46,575
Other				1,497
Net income	498,576				498,576
Amounts attributable to noncontrolling interests	(19,417)				(19,417)
Preferred share dividends	(16,453)				(16,453)
Unrealized holding (losses) gains arising during period, net of reclassification adjustment							(91,390)
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(4,494)						(4,494)
Foreign currency translation adjustments	(23,259)							(23,163)
Shares repurchased for treasury									(378,776)
Balance at end of period at Sep. 30, 2015	6,162,815	325,000	576	450,948	7,317,277	9,809	65,714	(55,905)	(1,940,795)
Non-redeemable noncontrolling interests, end of period at Sep. 30, 2015	774,162
Total shareholders’ equity at Sep. 30, 2015	6,936,977
Net income	64,000
Amounts attributable to noncontrolling interests	16,033
Preferred share dividends	(5,484)
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(3,033)
Foreign currency translation adjustments	(12,082)
Balance at end of period at Sep. 30, 2015	6,162,815	$ 325,000	$ 576	$ 450,948	$ 7,317,277	$ 9,809	$ 65,714	$ (55,905)	$ (1,940,795)
Non-redeemable noncontrolling interests, end of period at Sep. 30, 2015	774,162
Total shareholders’ equity at Sep. 30, 2015	$ 6,936,977

Unaudited Consolidated Stateme7

Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating Activities
Net income	$ 498,576	$ 614,126
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized losses (gains)	21,980	(113,033)
Net impairment losses recognized in earnings	12,780	26,313
Equity in net income or loss of investment funds accounted for using the equity method and other income or loss	3,983	3,784
Share-based compensation	46,575	45,118
Changes in:
Reserve for losses and loss adjustment expenses, net of unpaid losses and loss adjustment expenses recoverable	139,577	94,255
Unearned premiums, net of prepaid reinsurance premiums	192,162	325,874
Premiums receivable	(108,741)	(279,766)
Deferred acquisition costs, net	(41,722)	(72,120)
Reinsurance balances payable	4,242	49,621
Other liabilities	6,638	117,889
Other items	31,529	(12,402)
Net Cash Provided By Operating Activities	807,579	799,659
Investing Activities
Purchases of fixed maturity investments	(22,382,104)	(22,030,862)
Purchases of equity securities	(485,526)	(366,578)
Purchases of other investments	(1,320,250)	(1,136,285)
Proceeds from the sale of fixed maturity investments	21,411,554	20,273,351
Proceeds from the sale of equity securities	509,008	305,034
Proceeds from sales, redemptions and maturities of other investments	858,368	566,518
Proceeds from redemptions and maturities of fixed maturity investments	630,397	636,729
Net settlements of derivative instruments	81,114	15,495
Proceeds from investment in joint venture	40,000	0
Net sales of short-term investments	181,741	678,388
Change in cash collateral related to securities lending	28,685	(2,737)
Purchase of business, net of cash acquired	818	(235,578)
Purchases of fixed assets	(10,901)	(14,575)
Change in other assets	(43,654)	0
Net Cash Used For Investing Activities	(500,750)	(1,311,100)
Financing Activities
Purchases of common shares under share repurchase program	(365,383)	(251,919)
Proceeds from common shares issued, net	697	3,248
Proceeds from borrowings	239,077	0
Change in cash collateral related to securities lending	(28,685)	2,737
Third party investment in non-redeemable noncontrolling interests	0	796,903
Third party investment in redeemable noncontrolling interests	0	219,233
Dividends paid to redeemable noncontrolling interests	(13,810)	(9,632)
Other	50,463	6,559
Preferred dividends paid	(16,453)	(16,453)
Net Cash Provided By (Used For) Financing Activities	(134,094)	750,676
Effects of exchange rate changes on foreign currency cash	(8,658)	(9,566)
Increase in cash	164,077	229,669
Cash beginning of year	485,702	434,057
Cash end of period	649,779	663,726
Income taxes paid	35,460	13,335
Interest paid	$ 25,195	$ 22,111

General

General	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	General Arch Capital Group Ltd. (“ACGL”) is a Bermuda public limited liability company which provides insurance and reinsurance on a worldwide basis through its subsidiaries (together with ACGL, the “Company”). The Company’s consolidated financial statements include the results of Watford Holdings Ltd., the parent of Watford Re Ltd. (see Note 3 ). The interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and assumptions. In the opinion of management, the accompanying unaudited interim consolidated financial statements reflect all adjustments (consisting of normally recurring accruals) necessary for a fair statement of results on an interim basis. The results of any interim period are not necessarily indicative of the results for a full year or any future periods. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted; however, management believes that the disclosures are adequate to make the information presented not misleading. This report should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 (“2014 Form 10-K”), including the Company’s audited consolidated financial statements and related notes. The Company has reclassified the presentation of certain prior year information to conform to the current presentation. Such reclassifications had no effect on the Company’s net income, comprehensive income, shareholders’ equity or cash flows. Tabular amounts are in U.S. Dollars in thousands, except share amounts, unless otherwise noted. Acquisition of Gulf Reinsurance Limited In May 2008, the Company provided $100.0 million of funding to Gulf Reinsurance Limited, a wholly owned subsidiary of Gulf Re Holdings Limited (collectively, “Gulf Re”), pursuant to the joint venture agreement with Gulf Investment Corporation GSC (“GIC”). Under the agreement, Arch Re Bermuda and GIC each owned 50% of Gulf Re. The Company entered into a number of strategic initiatives related to Gulf Re in the 2014 fourth quarter, including an agreement to acquire complete ownership and effective control of Gulf Re. Such agreement was approved by the Dubai Financial Services Authority in April 2015 and the transaction closed on May 14, 2015. Pursuant to the agreement, Gulf Re distributed $130.6 million in total to the Company and GIC, and Gulf Re maintained $50.7 million of equity capital. The Company purchased GIC’s remaining investment in Gulf Re for $25.6 million through a transfer of fixed maturity investments. GIC will continue to participate equally with the Company in the financial results of Gulf Re and have the ability to purchase shares in Gulf Re over the next seven years . The acquisition resulted in no goodwill or other intangible assets as the fair value of Gulf Re was equal to its book value at closing.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Issued Accounting Standards Adopted The Company adopted accounting guidance in the 2015 second quarter which changes the accounting for repurchase and resale-to-maturity agreements by requiring that such agreements be recognized as financing arrangements, and requires that a transfer of a financial asset and a repurchase agreement entered into contemporaneously be accounted for separately. The new accounting guidance also requires additional disclosures about certain transferred financial assets accounted for as sales and certain securities lending transactions. Disclosures are not required to be presented for comparative periods before the effective date. See Note 6 , “Investment Information—Securities Lending Agreements.” The Company adopted accounting guidance in the 2015 second quarter which relates to the presentation of debt issuance costs. Such guidance requires presentation of debt issuance costs in the balance sheet as a deduction from the carrying amount of the related debt liability instead of a deferred charge. The Company previously included its debt issuance costs within ‘other assets.’ The guidance was applied retrospectively and resulted in reductions in ‘other assets’ and ‘senior notes’ at June 30, 2015 of $8.8 million , respectively, and $8.9 million at December 31, 2014, respectively. The adoption of this change in accounting principle did not impact the Company’s shareholders’ equity or net income. The Company adopted accounting guidance pertaining to the categorization within the fair value hierarchy of certain investments measured at fair value using the net asset value per share as a practical expedient. These investments are no longer required to be categorized within the fair value hierarchy but are still required to be reported in the fair value hierarchy table to permit reconciliation back to the consolidated balance sheet. Additionally, certain disclosures are no longer applicable for investments that are eligible to be measured using the practical expedient, but for which the practical expedient was not elected. The guidance was applied retrospectively and only impacted the Company’s disclosures. See Note 7 , “Fair Value.” Recently Issued Accounting Standards Not Yet Adopted An accounting standard was issued in the 2014 second quarter which will change the manner in which most companies recognize revenue. The standard requires that revenue reflect the transfer of goods or services to customers based on the consideration or payment the company expects to be entitled to in exchange for those goods or services; however, the standard does not change the accounting for insurance contracts or financial instruments. The new standard also requires enhanced disclosures about revenue. This accounting guidance is effective in the 2018 first quarter and may be applied on a full retrospective or modified retrospective approach. The Company is assessing the impact the implementation of this standard will have on its consolidated financial statements. An accounting standard was issued in the 2015 first quarter providing targeted improvements to consolidation guidance for limited partnerships and other similarly structured entities. The new standard addresses instances where a reporting entity consolidates another entity when the reporting entity is simply acting on the behalf of others, amongst other related issues. While the standard is targeted, the application is relevant for all companies that are required to assess whether or not to consolidate certain entities. The standard is effective in the 2016 first quarter and early adoption is permitted. The Company is assessing the impact the implementation of this standard will have on its consolidated financial statements. A new accounting standard was issued in the 2015 second quarter requiring new disclosures about the reserve for losses and loss adjustment expenses for short-duration insurance contracts. These disclosures will provide additional insight into an insurance entity’s ability to underwrite and anticipate costs associated with claims. This accounting guidance is effective for the 2016 annual reporting period and interim periods thereafter and should be applied retrospectively. The Company is assessing the impact the implementation of this standard will have on its consolidated financial statements.

Variable Interest Entities and

Variable Interest Entities and Noncontrolling Interests	9 Months Ended
	Sep. 30, 2015
Noncontrolling Interest [Abstract]
Variable Interest Entity and Noncontrolling Interests	Variable Interest Entity and Noncontrolling Interests Variable interest entity On March 20, 2014, the Company invested $100.0 million and acquired approximately 11% of Watford Holdings Ltd.’s common equity and a warrant to purchase additional common equity. Watford Holdings Ltd. is the parent of Watford Re Ltd., a multi-line Bermuda reinsurance company (together with Watford Holdings Ltd., “Watford Re”). Watford Re is considered a variable interest entity (“VIE”) and the Company concluded that it is the primary beneficiary of Watford Re. As such, the results of Watford Re are included in the Company’s consolidated financial statements. The Company concluded that Watford Re represents a separate operating segment and provides the income statement and total investable assets, total assets and total liabilities of Watford Re within Note 5 . At September 30, 2015 , Watford Re’s liabilities included unearned premiums of $274.7 million and reserves for losses and loss adjustment expenses of $223.9 million , some of which is related to transactions with the Company, along with $239.1 million of revolving credit agreement borrowings (see Note 9 ). For the nine months ended September 30, 2015 , Watford Re generated $204.3 million of cash provided by operating activities and $268.3 million of cash provided by financing activities, partially offset by $354.5 million of cash used for investing activities. The Company does not guarantee or provide credit support for Watford Re, and the Company’s financial exposure to Watford Re is limited to its investment in Watford Re’s common and preferred shares and counterparty credit risk (mitigated by collateral) arising from the reinsurance transactions. Non-redeemable noncontrolling interests The Company accounts for the portion of Watford Re’s common equity attributable to third party investors in the shareholders’ equity section of its consolidated balance sheets. The noncontrolling ownership in Watford Re’s common shares was approximately 89% at September 30, 2015 . The portion of Watford Re’s income or loss attributable to third party investors is recorded in the consolidated statements of income in ‘amounts attributable to noncontrolling interests.’ The following table sets forth activity in the non-redeemable noncontrolling interests: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Balance, beginning of period $ 794,880 $ 792,340 $ 769,081 $ — Sale of shares to noncontrolling interests — — — 796,903 Amounts attributable to noncontrolling interests (20,621 ) (10,320 ) 5,178 (14,883 ) Foreign currency translation adjustments (97 ) — (97 ) — Balance, end of period $ 774,162 $ 782,020 $ 774,162 $ 782,020 Redeemable noncontrolling interests The Company accounts for redeemable noncontrolling interests in the mezzanine section of its consolidated balance sheets in accordance with applicable accounting guidance. Such redeemable noncontrolling interests relate to the 9,065,200 cumulative redeemable preference shares (“Watford Preference Shares”) issued in late March 2014 with a par value of $0.01 per share and a liquidation preference of $25.00 per share. Preferred dividends, including the accretion of the discount and issuance costs, are included in ‘amounts attributable to noncontrolling interests’ in the Company’s consolidated statements of income. The following table sets forth activity in the redeemable non-controlling interests: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Balance, beginning of period $ 204,996 $ 219,326 $ 219,512 $ — Sale of shares to noncontrolling interests — — — 219,233 Shares acquired by the Company (1) — — (14,700 ) — Accretion of preference share issuance costs 93 93 277 186 Balance, end of period $ 205,089 $ 219,419 $ 205,089 $ 219,419 _________________________________________________ (1) During the 2015 second quarter, the Company acquired Gulf Re, which owns 600,000 Watford Preference Shares. Such shares, net of a discount, along with related dividends and accretion of the discount, are eliminated in consolidation. The portion of Watford Re’s income or loss attributable to third party investors is recorded in the consolidated statements of income in ‘amounts attributable to noncontrolling interests’ as summarized in the table below: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Amounts attributable to non-redeemable noncontrolling interests $ 20,621 $ 10,320 $ (5,178 ) $ 14,883 Dividends attributable to redeemable noncontrolling interests (4,588 ) (4,909 ) (14,239 ) (9,818 ) Amounts attributable to noncontrolling interests $ 16,033 $ 5,411 $ (19,417 ) $ 5,065

Earnings Per Common Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share The following table sets forth the computation of basic and diluted earnings per common share: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Numerator: Net income $ 64,000 $ 223,264 $ 498,576 $ 614,126 Amounts attributable to noncontrolling interests 16,033 5,411 (19,417 ) 5,065 Net income available to Arch 80,033 228,675 479,159 619,191 Preferred dividends (5,484 ) (5,484 ) (16,453 ) (16,453 ) Net income available to Arch common shareholders $ 74,549 $ 223,191 $ 462,706 $ 602,738 Denominator: Weighted average common shares outstanding — basic 120,567,410 131,945,962 122,151,971 132,151,824 Effect of dilutive common share equivalents: Nonvested restricted shares 1,322,053 1,156,790 1,260,247 1,134,481 Stock options (1) 3,122,310 2,773,853 2,942,541 3,067,867 Weighted average common shares and common share equivalents outstanding — diluted 125,011,773 135,876,605 126,354,759 136,354,172 Earnings per common share: Basic $ 0.62 $ 1.69 $ 3.79 $ 4.56 Diluted $ 0.60 $ 1.64 $ 3.66 $ 4.42 _________________________________________________ (1) Certain stock options were not included in the computation of diluted earnings per share where the exercise price of the stock options exceeded the average market price and would have been anti-dilutive or where, when applying the treasury stock method to in-the-money options, the sum of the proceeds, including unrecognized compensation, exceeded the average market price and would have been anti-dilutive. For the 2015 third quarter and 2014 third quarter , the number of stock options excluded were 390,406 and 1,355,087 , respectively. For the nine months ended September 30, 2015 and 2014 , the number of stock options excluded were 957,838 and 1,378,249 , respectively.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Segment Information	Segment Information The Company classifies its businesses into three underwriting segments — insurance, reinsurance and mortgage — and two other operating segments — ‘other’ and corporate (non-underwriting). The Company determined its reportable segments using the management approach described in accounting guidance regarding disclosures about segments of an enterprise and related information. The accounting policies of the segments are the same as those used for the preparation of the Company’s consolidated financial statements. Intersegment business is allocated to the segment accountable for the underwriting results. The Company’s insurance, reinsurance and mortgage segments each have managers who are responsible for the overall profitability of their respective segments and who are directly accountable to the Company’s chief operating decision makers, the Chairman, President and Chief Executive Officer of ACGL and the Chief Financial Officer of ACGL. The chief operating decision makers do not assess performance, measure return on equity or make resource allocation decisions on a line of business basis. Management measures segment performance for its three underwriting segments based on underwriting income or loss. The Company does not manage its assets by underwriting segment, with the exception of goodwill and intangible assets, and, accordingly, investment income is not allocated to each underwriting segment. The insurance segment consists of the Company’s insurance underwriting units which offer specialty product lines on a worldwide basis. Product lines include: construction and national accounts; excess and surplus casualty; lenders products; professional lines; programs; property, energy, marine and aviation; travel, accident and health; and other (consisting of alternative markets, excess workers' compensation and surety business). The reinsurance segment consists of the Company’s reinsurance underwriting units which offer specialty product lines on a worldwide basis. Product lines include: casualty; marine and aviation; other specialty; property catastrophe; property excluding property catastrophe (losses on a single risk, both excess of loss and pro rata); and other (consisting of life reinsurance, casualty clash and other). The mortgage segment includes the results of Arch Mortgage Insurance Company (“Arch MI U.S.”) and Arch Mortgage Insurance Limited, leading providers of mortgage insurance products and services to the U.S. and European markets, respectively. Arch MI U.S. is approved as an eligible mortgage insurer by Federal National Mortgage Association (“Fannie Mae”) and Federal Home Loan Mortgage Corporation (“Freddie Mac”), each a government sponsored enterprise, or “GSE.” The mortgage segment also includes GSE credit risk-sharing transactions and mortgage reinsurance for the U.S. and Australian markets. The corporate (non-underwriting) segment results include net investment income, other income (loss), other expenses incurred by the Company, interest expense, net realized gains or losses, net impairment losses included in earnings, equity in net income or loss of investment funds accounted for using the equity method, net foreign exchange gains or losses, income taxes and items related to the Company’s non-cumulative preferred shares. Such amounts exclude the results of the ‘other’ segment. The ‘other’ segment includes the results of Watford Re (see Note 3 ). Watford Re has its own management and board of directors that is responsible for the overall profitability of the ‘other’ segment. For the ‘other’ segment, performance is measured based on net income or loss. The following tables summarize the Company’s underwriting income or loss by segment, together with a reconciliation of underwriting income or loss to net income available to common shareholders: Three Months Ended September 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 752,438 $ 329,327 $ 74,657 $ 1,158,451 $ 131,165 $ 1,189,192 Premiums ceded (209,443 ) (92,182 ) (7,832 ) (311,486 ) (6,158 ) (217,220 ) Net premiums written 542,995 237,145 66,825 846,965 125,007 971,972 Change in unearned premiums (20,451 ) 23,286 (12,277 ) (9,442 ) (25,847 ) (35,289 ) Net premiums earned 522,544 260,431 54,548 837,523 99,160 936,683 Other underwriting income 519 2,783 3,565 6,867 756 7,623 Losses and loss adjustment expenses (339,859 ) (115,780 ) (9,562 ) (465,201 ) (66,540 ) (531,741 ) Acquisition expenses, net (77,076 ) (55,416 ) (10,428 ) (142,920 ) (28,646 ) (171,566 ) Other operating expenses (84,620 ) (37,131 ) (21,048 ) (142,799 ) (3,421 ) (146,220 ) Underwriting income (loss) $ 21,508 $ 54,887 $ 17,075 93,470 1,309 94,779 Net investment income 67,251 18,982 86,233 Net realized gains (losses) (53,480 ) (36,218 ) (89,698 ) Net impairment losses recognized in earnings (5,868 ) — (5,868 ) Equity in net income (loss) of investment funds accounted for using the equity method (2,118 ) — (2,118 ) Other income (loss) (265 ) — (265 ) Other expenses (10,739 ) — (10,739 ) Interest expense (12,014 ) (1,286 ) (13,300 ) Net foreign exchange gains (losses) 16,056 (1,376 ) 14,680 Income (loss) before income taxes 92,293 (18,589 ) 73,704 Income tax expense (9,704 ) — (9,704 ) Net income (loss) 82,589 (18,589 ) 64,000 Dividends attributable to redeemable noncontrolling interests — (4,588 ) (4,588 ) Amounts attributable to noncontrolling interests — 20,621 20,621 Net income (loss) available to Arch 82,589 (2,556 ) 80,033 Preferred dividends (5,484 ) — (5,484 ) Net income (loss) available to Arch common shareholders $ 77,105 $ (2,556 ) $ 74,549 Underwriting Ratios Loss ratio 65.0 % 44.5 % 17.5 % 55.5 % 67.1 % 56.8 % Acquisition expense ratio 14.8 % 21.3 % 19.1 % 17.1 % 28.9 % 18.3 % Other operating expense ratio 16.2 % 14.3 % 38.6 % 17.1 % 3.4 % 15.6 % Combined ratio 96.0 % 80.1 % 75.2 % 89.7 % 99.4 % 90.7 % Goodwill and intangible assets $ 29,834 $ 2,149 $ 71,637 $ 103,620 $ — $ 103,620 Total investable assets $ 14,733,732 $ 1,593,523 $ 16,327,255 Total assets 21,679,795 2,090,797 23,770,592 Total liabilities 15,627,574 1,000,952 16,628,526 _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total. Three Months Ended September 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 726,683 $ 345,747 $ 66,389 $ 1,138,392 $ 103,483 $ 1,159,907 Premiums ceded (187,689 ) (83,502 ) (7,904 ) (278,668 ) (3,668 ) (200,368 ) Net premiums written 538,994 262,245 58,485 859,724 99,815 959,539 Change in unearned premiums (19,607 ) 34,303 (5,539 ) 9,157 (65,045 ) (55,888 ) Net premiums earned 519,387 296,548 52,946 868,881 34,770 903,651 Other underwriting income 499 215 988 1,702 — 1,702 Losses and loss adjustment expenses (338,319 ) (123,784 ) (15,987 ) (478,090 ) (23,583 ) (501,673 ) Acquisition expenses, net (81,775 ) (60,205 ) (11,958 ) (153,938 ) (9,609 ) (163,547 ) Other operating expenses (83,138 ) (36,337 ) (17,913 ) (137,388 ) (1,658 ) (139,046 ) Underwriting income (loss) $ 16,654 $ 76,437 $ 8,076 101,167 (80 ) 101,087 Net investment income 72,239 7,866 80,105 Net realized gains (losses) 31,411 (12,896 ) 18,515 Net impairment losses recognized in earnings (8,593 ) — (8,593 ) Equity in net income (loss) of investment funds accounted for using the equity method 4,966 — 4,966 Other income (loss) (7,815 ) — (7,815 ) Other expenses (10,434 ) — (10,434 ) Interest expense (4,152 ) — (4,152 ) Net foreign exchange gains (losses) 57,611 (1,580 ) 56,031 Income (loss) before income taxes 236,400 (6,690 ) 229,710 Income tax expense (6,446 ) — (6,446 ) Net income (loss) 229,954 (6,690 ) 223,264 Dividends attributable to redeemable noncontrolling interests — (4,909 ) (4,909 ) Amounts attributable to noncontrolling interests — 10,320 10,320 Net income (loss) available to Arch 229,954 (1,279 ) 228,675 Preferred dividends (5,484 ) — (5,484 ) Net income (loss) available to Arch common shareholders $ 224,470 $ (1,279 ) $ 223,191 Underwriting Ratios Loss ratio 65.1 % 41.7 % 30.2 % 55.0 % 67.8 % 55.5 % Acquisition expense ratio 15.7 % 20.3 % 22.6 % 17.7 % 27.6 % 18.1 % Other operating expense ratio 16.0 % 12.3 % 33.8 % 15.8 % 4.8 % 15.4 % Combined ratio 96.8 % 74.3 % 86.6 % 88.5 % 100.2 % 89.0 % Goodwill and intangible assets $ 24,024 $ 3,939 $ 83,565 $ 111,528 $ — $ 111,528 Total investable assets $ 14,580,425 $ 1,124,048 $ 15,704,473 Total assets 21,205,209 1,403,018 22,608,227 Total liabilities 15,221,030 304,712 15,525,742 _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total. Nine Months Ended September 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 2,263,401 $ 1,156,540 $ 203,770 $ 3,625,382 $ 387,752 $ 3,730,423 Premiums ceded (669,336 ) (318,197 ) (23,404 ) (1,012,608 ) (17,979 ) (747,876 ) Net premiums written 1,594,065 838,343 180,366 2,612,774 369,773 2,982,547 Change in unearned premiums (53,782 ) (24,230 ) (22,992 ) (101,004 ) (91,158 ) (192,162 ) Net premiums earned 1,540,283 814,113 157,374 2,511,770 278,615 2,790,385 Other underwriting income 1,467 6,870 14,969 23,306 3,570 26,876 Losses and loss adjustment expenses (978,681 ) (339,495 ) (33,010 ) (1,351,186 ) (193,697 ) (1,544,883 ) Acquisition expenses, net (228,877 ) (170,380 ) (31,046 ) (430,303 ) (79,764 ) (510,067 ) Other operating expenses (261,793 ) (114,182 ) (61,096 ) (437,071 ) (8,876 ) (445,947 ) Underwriting income (loss) $ 72,399 $ 196,926 $ 47,191 316,516 (152 ) 316,364 Net investment income 204,710 47,480 252,190 Net realized gains (losses) (14,831 ) (27,244 ) (42,075 ) Net impairment losses recognized in earnings (12,780 ) — (12,780 ) Equity in net income (loss) of investment funds accounted for using the equity method 19,938 — 19,938 Other income (loss) 52 — 52 Other expenses (37,502 ) — (37,502 ) Interest expense (28,761 ) (1,286 ) (30,047 ) Net foreign exchange gains (losses) 60,338 1,260 61,598 Income (loss) before income taxes 507,680 20,058 527,738 Income tax expense (29,162 ) — (29,162 ) Net income (loss) 478,518 20,058 498,576 Dividends attributable to redeemable noncontrolling interests — (14,239 ) (14,239 ) Amounts attributable to noncontrolling interests — (5,178 ) (5,178 ) Net income (loss) available to Arch 478,518 641 479,159 Preferred dividends (16,453 ) — (16,453 ) Net income (loss) available to Arch common shareholders $ 462,065 $ 641 $ 462,706 Underwriting Ratios Loss ratio 63.5 % 41.7 % 21.0 % 53.8 % 69.5 % 55.4 % Acquisition expense ratio 14.9 % 20.9 % 19.7 % 17.1 % 28.6 % 18.3 % Other operating expense ratio 17.0 % 14.0 % 38.8 % 17.4 % 3.2 % 16.0 % Combined ratio 95.4 % 76.6 % 79.5 % 88.3 % 101.3 % 89.7 % _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total. Nine Months Ended September 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 2,309,560 $ 1,212,641 $ 169,772 $ 3,690,462 $ 190,239 $ 3,726,804 Premiums ceded (646,082 ) (215,623 ) (17,622 ) (877,816 ) (6,428 ) (730,347 ) Net premiums written 1,663,478 997,018 152,150 2,812,646 183,811 2,996,457 Change in unearned premiums (158,878 ) (23,495 ) (9,606 ) (191,979 ) (133,895 ) (325,874 ) Net premiums earned 1,504,600 973,523 142,544 2,620,667 49,916 2,670,583 Other underwriting income 1,513 834 2,970 5,317 — 5,317 Losses and loss adjustment expenses (936,615 ) (413,745 ) (39,938 ) (1,390,298 ) (33,133 ) (1,423,431 ) Acquisition expenses, net (235,156 ) (199,673 ) (32,593 ) (467,422 ) (14,625 ) (482,047 ) Other operating expenses (250,111 ) (110,198 ) (48,077 ) (408,386 ) (4,402 ) (412,788 ) Underwriting income (loss) $ 84,231 $ 250,741 $ 24,906 359,878 (2,244 ) 357,634 Net investment income 211,690 8,399 220,089 Net realized gains (losses) 102,074 (9,718 ) 92,356 Net impairment losses recognized in earnings (26,313 ) — (26,313 ) Equity in net income (loss) of investment funds accounted for using the equity method 17,459 — 17,459 Other income (loss) (5,069 ) — (5,069 ) Other expenses (36,512 ) (2,329 ) (38,841 ) Interest expense (32,890 ) — (32,890 ) Net foreign exchange gains (losses) 48,191 (1,017 ) 47,174 Income (loss) before income taxes 638,508 (6,909 ) 631,599 Income tax expense (17,473 ) — (17,473 ) Net income (loss) 621,035 (6,909 ) 614,126 Dividends attributable to redeemable noncontrolling interests — (9,818 ) (9,818 ) Amounts attributable to noncontrolling interests — 14,883 14,883 Net income (loss) available to Arch 621,035 (1,844 ) 619,191 Preferred dividends (16,453 ) — (16,453 ) Net income (loss) available to Arch common shareholders $ 604,582 $ (1,844 ) $ 602,738 Underwriting Ratios Loss ratio 62.3 % 42.5 % 28.0 % 53.1 % 66.4 % 53.3 % Acquisition expense ratio 15.6 % 20.5 % 22.9 % 17.8 % 29.3 % 18.1 % Other operating expense ratio 16.6 % 11.3 % 33.7 % 15.6 % 8.8 % 15.5 % Combined ratio 94.5 % 74.3 % 84.6 % 86.5 % 104.5 % 86.9 % _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total.

Investment Information

Investment Information	9 Months Ended
	Sep. 30, 2015
Disclosure Investment Information [Abstract]
Investment Information	Investment Information At September 30, 2015 , total investable assets of $16.33 billion included $14.73 billion managed by the Company and $1.59 billion attributable to Watford Re. Available For Sale Investments The following table summarizes the fair value and cost or amortized cost of the Company’s investments classified as available for sale: Estimated Fair Value Gross Unrealized Gains Gross Unrealized Losses Cost or Amortized Cost OTTI Unrealized Losses (2) September 30, 2015 Fixed maturities (1): Corporate bonds $ 2,796,038 $ 28,418 $ (54,489 ) $ 2,822,109 $ (3,033 ) Mortgage backed securities 809,876 13,155 (2,998 ) 799,719 (3,554 ) Municipal bonds 1,830,987 27,600 (2,771 ) 1,806,158 — Commercial mortgage backed securities 810,973 10,058 (2,594 ) 803,509 — U.S. government and government agencies 2,338,724 14,352 (2,138 ) 2,326,510 — Non-U.S. government securities 887,120 13,070 (36,488 ) 910,538 — Asset backed securities 1,372,549 9,032 (4,850 ) 1,368,367 (22 ) Total 10,846,267 115,685 (106,328 ) 10,836,910 (6,609 ) Equity securities 606,259 68,494 (37,527 ) 575,292 — Other investments 281,014 39,287 (3,629 ) 245,356 — Short-term investments 708,428 166 (3,128 ) 711,390 — Total $ 12,441,968 $ 223,632 $ (150,612 ) $ 12,368,948 $ (6,609 ) December 31, 2014 Fixed maturities (1): Corporate bonds $ 3,108,513 $ 37,928 $ (38,974 ) $ 3,109,559 $ (317 ) Mortgage backed securities 943,343 18,843 (3,842 ) 928,342 (3,307 ) Municipal bonds 1,494,122 31,227 (1,044 ) 1,463,939 — Commercial mortgage backed securities 1,114,528 14,594 (3,822 ) 1,103,756 — U.S. government and government agencies 1,447,972 8,345 (1,760 ) 1,441,387 — Non-U.S. government securities 1,015,153 21,311 (37,203 ) 1,031,045 — Asset backed securities 1,677,941 8,425 (6,089 ) 1,675,605 (22 ) Total 10,801,572 140,673 (92,734 ) 10,753,633 (3,646 ) Equity securities 658,182 109,012 (13,364 ) 562,534 — Other investments 296,224 31,839 (362 ) 264,747 — Short-term investments 797,226 738 (5,270 ) 801,758 — Total $ 12,553,204 $ 282,262 $ (111,730 ) $ 12,382,672 $ (3,646 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.” (2) Represents the total other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income (“AOCI”). It does not include the change in fair value subsequent to the impairment measurement date. At September 30, 2015 , the net unrealized loss related to securities for which a non-credit OTTI was recognized in AOCI was $2.3 million , compared to a net unrealized gain of $0.9 million at December 31, 2014 . The following table summarizes, for all available for sale securities in an unrealized loss position, the fair value and gross unrealized loss by length of time the security has been in a continual unrealized loss position: Less than 12 Months 12 Months or More Total Estimated Gross Unrealized Losses Estimated Gross Unrealized Losses Estimated Gross Unrealized Losses September 30, 2015 Fixed maturities (1): Corporate bonds $ 1,208,894 $ (37,606 ) $ 135,135 $ (16,883 ) $ 1,344,029 $ (54,489 ) Mortgage backed securities 235,252 (1,986 ) 52,621 (1,012 ) 287,873 (2,998 ) Municipal bonds 219,610 (2,567 ) 9,717 (204 ) 229,327 (2,771 ) Commercial mortgage backed securities 263,779 (2,376 ) 19,774 (218 ) 283,553 (2,594 ) U.S. government and government agencies 283,534 (2,138 ) — — 283,534 (2,138 ) Non-U.S. government securities 391,631 (23,526 ) 52,976 (12,962 ) 444,607 (36,488 ) Asset backed securities 467,485 (3,262 ) 126,982 (1,588 ) 594,467 (4,850 ) Total 3,070,185 (73,461 ) 397,205 (32,867 ) 3,467,390 (106,328 ) Equity securities 311,608 (37,527 ) — — 311,608 (37,527 ) Other investments 45,151 (3,629 ) — — 45,151 (3,629 ) Short-term investments 33,873 (3,128 ) — — 33,873 (3,128 ) Total $ 3,460,817 $ (117,745 ) $ 397,205 $ (32,867 ) $ 3,858,022 $ (150,612 ) December 31, 2014 Fixed maturities (1): Corporate bonds $ 1,309,637 $ (32,903 ) $ 148,963 $ (6,071 ) $ 1,458,600 $ (38,974 ) Mortgage backed securities 293,624 (1,476 ) 59,107 (2,366 ) 352,731 (3,842 ) Municipal bonds 210,614 (588 ) 13,643 (456 ) 224,257 (1,044 ) Commercial mortgage backed securities 232,147 (770 ) 125,894 (3,052 ) 358,041 (3,822 ) U.S. government and government agencies 618,381 (1,626 ) 3,438 (134 ) 621,819 (1,760 ) Non-U.S. government securities 510,766 (31,172 ) 46,910 (6,031 ) 557,676 (37,203 ) Asset backed securities 612,950 (2,486 ) 243,452 (3,603 ) 856,402 (6,089 ) Total 3,788,119 (71,021 ) 641,407 (21,713 ) 4,429,526 (92,734 ) Equity securities 181,002 (13,364 ) — — 181,002 (13,364 ) Other investments 59,638 (362 ) — — 59,638 (362 ) Short-term investments 79,271 (5,270 ) — — 79,271 (5,270 ) Total $ 4,108,030 $ (90,017 ) $ 641,407 $ (21,713 ) $ 4,749,437 $ (111,730 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.” At September 30, 2015 , on a lot level basis, approximately 2,300 security lots out of a total of approximately 5,540 security lots were in an unrealized loss position and the largest single unrealized loss from a single lot in the Company’s fixed maturity portfolio was $3.6 million . At December 31, 2014 , on a lot level basis, approximately 1,900 security lots out of a total of approximately 4,790 security lots were in an unrealized loss position and the largest single unrealized loss from a single lot in the Company’s fixed maturity portfolio was $2.9 million . The contractual maturities of the Company’s fixed maturities are shown in the following table. Expected maturities, which are management’s best estimates, will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. September 30, 2015 December 31, 2014 Maturity Estimated Fair Value Amortized Cost Estimated Amortized Cost Due in one year or less $ 329,589 $ 331,322 $ 235,930 $ 233,794 Due after one year through five years 4,510,824 4,518,625 4,074,562 4,077,408 Due after five years through 10 years 2,583,000 2,585,634 2,475,726 2,461,356 Due after 10 years 429,456 429,734 279,542 273,372 7,852,869 7,865,315 7,065,760 7,045,930 Mortgage backed securities 809,876 799,719 943,343 928,342 Commercial mortgage backed securities 810,973 803,509 1,114,528 1,103,756 Asset backed securities 1,372,549 1,368,367 1,677,941 1,675,605 Total (1) $ 10,846,267 $ 10,836,910 $ 10,801,572 $ 10,753,633 _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.” Securities Lending Agreements From time to time, the Company enters into securities lending agreements with financial institutions to enhance investment income. The Company loans certain of its securities to third parties, primarily major brokerage firms, for short periods of time through a lending agent. The Company maintains legal control over the securities it lends, retains the earnings and cash flows associated with the loaned securities and receives a fee from the borrower for the temporary use of the securities. An indemnification agreement with the lending agent protects the Company in the event a borrower becomes insolvent or fails to return any of the securities on loan to the Company. The Company receives collateral in the form of cash or securities. Cash collateral primarily consists of short-term investments. At September 30, 2015 , the fair value of the cash collateral received on securities lending was $15.7 million , which included $5.4 million that was reinvested in sub-prime mortgage backed securities, and the fair value of security collateral received was $271.0 million . At December 31, 2014 , the fair value of the cash collateral received on securities lending was $44.3 million , which included $5.8 million that was reinvested in sub-prime mortgage backed securities, and the fair value of security collateral received was nil . The Company’s securities lending transactions were accounted for as secured borrowings with significant investment categories as follows: September 30, 2015 Remaining Contractual Maturity of the Agreements Securities Lending Transactions Overnight and Continuous Less than 30 Days 30-90 Days 90 Days or More Total U.S. government and government agencies $ 225,898 $ — $ 22,784 $ 3,569 $ 252,251 Corporate bonds 35,266 — — — 35,266 Equity securities 5,321 — — — 5,321 Total $ 266,485 $ — $ 22,784 $ 3,569 $ 292,838 Gross amount of recognized liabilities for securities lending in offsetting disclosure in Note 8 $ — Amounts related to securities lending not included in offsetting disclosure in Note 8 $ 292,838 Other Investments The following table summarizes the Company’s other investments, including available for sale and fair value option components: September 30, December 31, Available for sale: Asian and emerging markets $ 210,680 $ 236,586 Investment grade fixed income 31,429 59,638 Credit related funds 13,722 — Other 25,183 — Total available for sale 281,014 296,224 Fair value option: Term loan investments (par value: $1,188,216 and $1,094,337) 1,152,693 1,073,649 Mezzanine debt funds 112,782 121,341 Credit related funds 194,957 114,436 Investment grade fixed income 58,204 69,108 Asian and emerging markets 59,667 25,800 Other (1) 124,591 137,094 Total fair value option 1,702,894 1,541,428 Total $ 1,983,908 $ 1,837,652 _________________________________________________ (1) Includes fund investments with strategies in mortgage servicing rights, transportation and infrastructure assets and other. Certain of the Company’s other investments are in investment funds for which the Company has the option to redeem at agreed upon values as described in each investment fund’s subscription agreement. Depending on the terms of the various subscription agreements, investments in investment funds may be redeemed daily, monthly, quarterly or on other terms. Two common redemption restrictions which may impact the Company’s ability to redeem these investment funds are gates and lockups. A gate is a suspension of redemptions which may be implemented by the general partner or investment manager of the fund in order to defer, in whole or in part, the redemption request in the event the aggregate amount of redemption requests exceeds a predetermined percentage of the investment fund’s net assets which may otherwise hinder the general partner or investment manager’s ability to liquidate holdings in an orderly fashion in order to generate the cash necessary to fund extraordinarily large redemption payouts. A lockup period is the initial amount of time an investor is contractually required to hold the security before having the ability to redeem. If the investment funds are eligible to be redeemed, the time to redeem such fund can take weeks or months following the notification. Fair Value Option The following table summarizes the Company’s assets and liabilities which are accounted for using the fair value option: September 30, December 31, Fixed maturities $ 926,589 $ 632,024 Other investments 1,702,894 1,541,428 Short-term investments 153,604 251,601 Equity securities 78 — Investments accounted for using the fair value option $ 2,783,165 $ 2,425,053 Net Investment Income The components of net investment income were derived from the following sources: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Fixed maturities $ 70,626 $ 66,052 $ 210,497 $ 194,370 Term loan investments 16,922 14,066 49,699 26,643 Equity securities (dividends) 3,486 2,779 8,743 8,971 Short-term investments 127 905 548 1,417 Other (1) 10,277 7,913 33,513 21,732 Gross investment income 101,438 91,715 303,000 253,133 Investment expenses (15,205 ) (11,610 ) (50,810 ) (33,044 ) Net investment income $ 86,233 $ 80,105 $ 252,190 $ 220,089 _________________________________________________ (1) Includes income distributions from investment funds and other items. Net Realized Gains (Losses) Net realized gains (losses) were as follows, excluding other-than-temporary impairment provisions: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Available for sale securities: Gross gains on investment sales $ 51,933 $ 62,727 $ 231,757 $ 185,541 Gross losses on investment sales (53,953 ) (35,012 ) (168,087 ) (108,053 ) Change in fair value of assets and liabilities accounted for using the fair value option: Fixed maturities (41,236 ) (9,023 ) (49,729 ) 318 Other investments (75,251 ) (1,085 ) (68,179 ) 27,676 Equity securities 71 — — — Short-term investments (9 ) 638 1,462 638 Derivative instruments (1) 35,889 7,449 31,069 7,083 Other (2) (7,142 ) (7,179 ) (20,368 ) (20,847 ) Net realized gains (losses) $ (89,698 ) $ 18,515 $ (42,075 ) $ 92,356 _________________________________________________ (1) See Note 8 for information on the Company’s derivative instruments. (2) Includes the re-measurement of contingent consideration liability amounts. Other-Than-Temporary Impairments The Company performs quarterly reviews of its available for sale investments in order to determine whether declines in fair value below the amortized cost basis were considered other-than-temporary in accordance with applicable guidance. The following table details the net impairment losses recognized in earnings by asset class: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Fixed maturities: Mortgage backed securities $ (85 ) $ (2 ) $ (1,483 ) $ (2 ) Corporate bonds (4,282 ) (147 ) (6,268 ) (811 ) Commercial mortgage backed securities — (7 ) — (7 ) Asset backed securities — (29 ) — (40 ) Total (4,367 ) (185 ) (7,751 ) (860 ) Short-term investments — — (2,341 ) — Equity securities (1,501 ) (95 ) (1,754 ) (373 ) Other investments — (8,313 ) (934 ) (25,080 ) Net impairment losses recognized in earnings $ (5,868 ) $ (8,593 ) $ (12,780 ) $ (26,313 ) A description of the methodology and significant inputs used to measure the amount of net impairment losses recognized in earnings 2015 third quarter is as follows: • Corporate bonds — the Company reviewed the business prospects, credit ratings, estimated loss given default factors, foreign currency impacts and information received from asset managers and rating agencies for certain corporate bonds. Approximately half of the impairment losses for the 2015 third quarter resulted from non-investment grade corporate bonds in the energy sector, reflecting current market conditions, with the remaining half related to foreign currency fluctuations on non-U.S. Dollar denominated investments based on the remaining time to maturity. The amortized cost basis of the corporate bonds were adjusted down, if required, to the expected recovery value calculated in the OTTI review process; • Equity securities – the Company utilized information received from asset managers on common stocks, including the business prospects, recent events, industry and market data and other factors. For certain equities which were in an unrealized loss position and where the Company determined that it did not have the intent or ability to hold such securities for a reasonable period of time by which the fair value of the securities would increase and the Company would recover its cost, the cost basis of such securities was adjusted down accordingly. The Company believes that the $6.6 million of OTTI included in accumulated other comprehensive income at September 30, 2015 on the securities which were considered by the Company to be impaired was due to market and sector-related factors ( i.e. , not credit losses). At September 30, 2015 , the Company did not intend to sell these securities, or any other securities which were in an unrealized loss position, and determined that it is more likely than not that the Company will not be required to sell such securities before recovery of their cost basis. The following table provides a roll forward of the amount related to credit losses recognized in earnings for which a portion of an OTTI was recognized in accumulated other comprehensive income: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Balance at start of period $ 20,906 $ 21,441 $ 20,196 $ 60,062 Credit loss impairments recognized on securities not previously impaired 4,024 — 8,794 — Credit loss impairments recognized on securities previously impaired 41 151 175 162 Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security — — — — Reductions for securities sold during the period — (217 ) (4,194 ) (38,849 ) Balance at end of period $ 24,971 $ 21,375 $ 24,971 $ 21,375 Restricted Assets The Company is required to maintain assets on deposit, which primarily consist of fixed maturities, with various regulatory authorities to support its insurance and reinsurance operations. The Company’s insurance and reinsurance subsidiaries maintain assets in trust accounts as collateral for insurance and reinsurance transactions with affiliated companies and also have investments in segregated portfolios primarily to provide collateral or guarantees for letters of credit to third parties. See Note 9 for further details. The following table details the value of the Company’s restricted assets: September 30, December 31, Assets used for collateral or guarantees: Affiliated transactions $ 3,737,514 $ 4,138,527 Third party agreements 1,071,260 970,120 Deposits with U.S. regulatory authorities 405,817 337,981 Deposits with non-U.S. regulatory authorities 40,365 — Trust funds 100,789 72,461 Total restricted assets $ 5,355,745 $ 5,519,089

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value	Fair Value Accounting guidance regarding fair value measurements addresses how companies should measure fair value when they are required to use a fair value measure for recognition or disclosure purposes under GAAP and provides a common definition of fair value to be used throughout GAAP. It defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly fashion between market participants at the measurement date. In addition, it establishes a three-level valuation hierarchy for the disclosure of fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. The level in the hierarchy within which a given fair value measurement falls is determined based on the lowest level input that is significant to the measurement (Level 1 being the highest priority and Level 3 being the lowest priority). The levels in the hierarchy are defined as follows: Level 1: Inputs to the valuation methodology are observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets Level 2: Inputs to the valuation methodology include quoted prices for similar assets and liabilities in active markets, and inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the financial instrument Level 3: Inputs to the valuation methodology are unobservable and significant to the fair value measurement Following is a description of the valuation methodologies used for securities measured at fair value, as well as the general classification of such securities pursuant to the valuation hierarchy. The Company reviews its securities measured at fair value and discusses the proper classification of such investments with investment advisers and others. The Company determines the existence of an active market based on its judgment as to whether transactions for the financial instrument occur in such market with sufficient frequency and volume to provide reliable pricing information. The independent pricing sources obtain market quotations and actual transaction prices for securities that have quoted prices in active markets. The Company uses quoted values and other data provided by nationally recognized independent pricing sources as inputs into its process for determining fair values of its fixed maturity investments. To validate the techniques or models used by pricing sources, the Company's review process includes, but is not limited to: (i) quantitative analysis (e.g., comparing the quarterly return for each managed portfolio to its target benchmark, with significant differences identified and investigated); (ii) a review of the average number of prices obtained in the pricing process and the range of resulting fair values; (iii) initial and ongoing evaluation of methodologies used by outside parties to calculate fair value; (iv) a comparison of the fair value estimates to the Company’s knowledge of the current market; (v) a comparison of the pricing services' fair values to other pricing services' fair values for the same investments; and (vi) periodic back-testing, which includes randomly selecting purchased or sold securities and comparing the executed prices to the fair value estimates from the pricing service. A price source hierarchy was maintained in order to determine which price source would be used (i.e., a price obtained from a pricing service with more seniority in the hierarchy will be used over a less senior one in all cases). The hierarchy prioritizes pricing services based on availability and reliability and assigns the highest priority to index providers. Based on the above review, the Company will challenge any prices for a security or portfolio which are considered not to be representative of fair value. The Company did not adjust any of the prices obtained from the independent pricing sources at September 30, 2015 . In certain circumstances, when fair values are unavailable from these independent pricing sources, quotes are obtained directly from broker-dealers who are active in the corresponding markets. Such quotes are subject to the validation procedures noted above. Of the $15.36 billion of financial assets and liabilities measured at fair value at September 30, 2015 , approximately $300.7 million , or 2.0% , were priced using non-binding broker-dealer quotes. Of the $15.06 billion of financial assets and liabilities measured at fair value at December 31, 2014 , approximately $260.8 million , or 1.7% , were priced using non-binding broker-dealer quotes. Fixed maturities . The Company uses the market approach valuation technique to estimate the fair value of its fixed maturity securities, when possible. The market approach includes obtaining prices from independent pricing services, such as index providers and pricing vendors, as well as to a lesser extent quotes from broker-dealers. The independent pricing sources obtain market quotations and actual transaction prices for securities that have quoted prices in active markets. Each source has its own proprietary method for determining the fair value of securities that are not actively traded. In general, these methods involve the use of “matrix pricing” in which the independent pricing source uses observable market inputs including, but not limited to, investment yields, credit risks and spreads, benchmarking of like securities, broker-dealer quotes, reported trades and sector groupings to determine a reasonable fair value. The following describes the significant inputs generally used to determine the fair value of the Company’s fixed maturity securities by asset class: • U.S. government and government agencies — valuations provided by independent pricing services, with all prices provided through index providers and pricing vendors. The Company determined that all U.S. Treasuries would be classified as Level 1 securities due to observed levels of trading activity, the high number of strongly correlated pricing quotes received on U.S. Treasuries and other factors. The fair values of U.S. government agency securities are generally determined using the spread above the risk-free yield curve. As the yields for the risk-free yield curve and the spreads for these securities are observable market inputs, the fair values of U.S. government agency securities are classified within Level 2. • Corporate bonds — valuations provided by independent pricing services, substantially all through index providers and pricing vendors with a small amount through broker-dealers. The fair values of these securities are generally determined using the spread above the risk-free yield curve. These spreads are generally obtained from the new issue market, secondary trading and from broker-dealers who trade in the relevant security market. As the significant inputs used in the pricing process for corporate bonds are observable market inputs, the fair value of these securities are classified within Level 2. • Mortgage-backed securities — valuations provided by independent pricing services, substantially all through pricing vendors and index providers with a small amount through broker-dealers. The fair values of these securities are generally determined through the use of pricing models (including Option Adjusted Spread) which use spreads to determine the expected average life of the securities. These spreads are generally obtained from the new issue market, secondary trading and from broker-dealers who trade in the relevant security market. The pricing services also review prepayment speeds and other indicators, when applicable. As the significant inputs used in the pricing process for mortgage-backed securities are observable market inputs, the fair value of these securities are classified within Level 2. • Municipal bonds — valuations provided by independent pricing services, with all prices provided through index providers and pricing vendors. The fair values of these securities are generally determined using spreads obtained from broker-dealers who trade in the relevant security market, trade prices and the new issue market. As the significant inputs used in the pricing process for municipal bonds are observable market inputs, the fair value of these securities are classified within Level 2. • Commercial mortgage-backed securities — valuations provided by independent pricing services, substantially all through index providers and pricing vendors with a small amount through broker-dealers. The fair values of these securities are generally determined through the use of pricing models which use spreads to determine the appropriate average life of the securities. These spreads are generally obtained from the new issue market, secondary trading and from broker-dealers who trade in the relevant security market. The pricing services also review prepayment speeds and other indicators, when applicable. As the significant inputs used in the pricing process for commercial mortgage-backed securities are observable market inputs, the fair value of these securities are classified within Level 2. • Non-U.S. government securities — valuations provided by independent pricing services, with all prices provided through index providers and pricing vendors. The fair values of these securities are generally based on international indices or valuation models which include daily observed yield curves, cross-currency basis index spreads and country credit spreads. As the significant inputs used in the pricing process for non-U.S. government securities are observable market inputs, the fair value of these securities are classified within Level 2. • Asset-backed securities — valuations provided by independent pricing services, substantially all through index providers and pricing vendors with a small amount through broker-dealers. The fair values of these securities generally determined through the use of pricing models (including Option Adjusted Spread) which use spreads to determine the appropriate average life of the securities. These spreads are generally obtained from the new issue market, secondary trading and from broker-dealers who trade in the relevant security market. The pricing services also review prepayment speeds and other indicators, when applicable. As the significant inputs used in the pricing process for asset-backed securities are observable market inputs, the fair value of these securities are classified within Level 2. During the 2015 second quarter, the Company transferred $44.6 million of U.S. government agency securities from Level 1 to Level 2 based on a review of the pricing of such securities, as described above. Equity securities . The Company determined that exchange-traded equity securities would be included in Level 1 as their fair values are based on quoted market prices in active markets. Other equity securities are included in Level 2 of the valuation hierarchy. Other investments . The Company determined that exchange-traded investments in mutual funds would be included in Level 1 as their fair values are based on quoted market prices in active markets. Other investments also include term loan investments for which fair values are estimated by using quoted prices of term loan investments with similar characteristics, pricing models or matrix pricing. Such investments are generally classified within Level 2. The fair values for certain of the Company’s other investments are determined using net asset values as advised by external fund managers. The net asset value is based on the fund manager’s valuation of the underlying holdings in accordance with the fund’s governing documents. In accordance with applicable accounting guidance, 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. During the 2015 second quarter, the Company transferred $99.7 million of other investments from Level 2 to Level 1 based on a review of the pricing of such securities, as described above. Derivative instruments. The Company’s futures contracts, foreign currency forward contracts, interest rate swaps and other derivatives trade in the over-the-counter derivative market. The Company uses the market approach valuation technique to estimate the fair value for these derivatives based on significant observable market inputs from third party pricing vendors, non-binding broker-dealer quotes and/or recent trading activity. As the significant inputs used in the pricing process for these derivative instruments are observable market inputs, the fair value of these securities are classified within Level 2. Short-term investments . The Company determined that certain of its short-term investments held in highly liquid money market-type funds would be included in Level 1 as their fair values are based on quoted market prices in active markets. The fair values of other short-term investments are generally determined using the spread above the risk-free yield curve and are classified within Level 2. Contingent consideration liabilities . Contingent consideration liabilities (included in ‘other liabilities’ in the consolidated balance sheets) includes amounts related to the acquisition of CMG Mortgage Insurance Company and its affiliated mortgage insurance companies and other acquisitions. Such amounts are remeasured at fair value at each balance sheet date with changes in fair value recognized in ‘net realized gains (losses).’ To determine the fair value of contingent consideration liabilities, the Company estimates future payments using an income approach based on modeled inputs which include a weighted average cost of capital. The Company determined that contingent consideration liabilities would be included within Level 3. The following table presents the Company’s financial assets and liabilities measured at fair value by level at September 30, 2015 : Estimated Fair Value Measurements Using: Estimated Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets measured at fair value: Available for sale securities: Fixed maturities (1): Corporate bonds $ 2,796,038 $ — $ 2,796,038 $ — Mortgage backed securities 809,876 — 809,876 — Municipal bonds 1,830,987 — 1,830,987 — Commercial mortgage backed securities 810,973 — 810,973 — U.S. government and government agencies 2,338,724 2,292,409 46,315 — Non-U.S. government securities 887,120 — 887,120 — Asset backed securities 1,372,549 — 1,315,049 57,500 Total 10,846,267 2,292,409 8,496,358 57,500 Equity securities 606,259 605,677 582 — Short-term investments 708,428 703,316 5,112 — Other investments 60,526 60,526 — — Other investments measured at net asset value (2) 220,488 Total other investments 281,014 60,526 — — Derivative instruments (4) 16,865 — 16,865 — Fair value option: Corporate bonds 767,567 — 767,567 — Non-U.S. government bonds 76,973 — 76,973 — Mortgage backed securities 59,435 — 59,435 — Asset backed securities 22,499 — 22,499 — U.S. government and government agencies 115 115 — — Short-term investments 153,604 153,604 — — Equity securities 78 78 — — Other investments 1,221,194 68,501 1,152,693 — Other investments measured at net asset value (2) 481,700 Total 2,783,165 222,298 2,079,167 — Total assets measured at fair value $ 15,241,998 $ 3,884,226 $ 10,598,084 $ 57,500 Liabilities measured at fair value: Contingent consideration liabilities $ (80,852 ) $ — $ — $ (80,852 ) Securities sold but not yet purchased (3) (25,384 ) — (25,384 ) — Derivative instruments (4) (38,027 ) — (38,027 ) — Total liabilities measured at fair value $ (144,263 ) $ — $ (63,411 ) $ (80,852 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See Note 6 , “Investment Information—Securities Lending Agreements.” (2) In accordance with applicable accounting guidance, 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 sheets. (3) Represents the Company’s obligations to deliver securities that it did not own at the time of sale. Such amounts are included in “other liabilities” on the Company’s consolidated balance sheets. (4) See Note 8 , “Derivative Instruments.” The following table presents the Company’s financial assets and liabilities measured at fair value by level at December 31, 2014 : Estimated Fair Value Measurements Using: Estimated Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets measured at fair value: Available for sale securities: Fixed maturities (1): Corporate bonds $ 3,108,513 $ — $ 3,108,513 $ — Mortgage backed securities 943,343 — 943,343 — Municipal bonds 1,494,122 — 1,494,122 — Commercial mortgage backed securities 1,114,528 — 1,114,528 — U.S. government and government agencies 1,447,972 1,447,972 — — Non-U.S. government securities 1,015,153 — 1,015,153 — Asset backed securities 1,677,941 — 1,620,441 57,500 Total 10,801,572 1,447,972 9,296,100 57,500 Equity securities 658,182 658,182 — — Short-term investments 797,226 759,621 37,605 — Other investments 97,372 — 97,372 — Other investments measured at net asset value (2) 198,852 Total other investments 296,224 — 97,372 — Derivative instruments (3) 15,876 — 15,876 — Fair value option: Corporate bonds 497,101 — 497,101 — Non-U.S. government bonds 88,411 — 88,411 — Mortgage backed securities 22,190 — 22,190 — Asset backed securities 24,322 — 24,322 — Short-term investments 251,601 250,580 1,021 — Other investments 1,140,266 — 1,140,266 — Other investments measured at net asset value (2) 401,162 Total 2,425,053 250,580 1,773,311 — Total assets measured at fair value $ 14,994,133 $ 3,116,355 $ 11,220,264 $ 57,500 Liabilities measured at fair value: Contingent consideration liabilities $ (61,845 ) $ — $ — $ (61,845 ) Derivative instruments (3) (5,397 ) — (5,397 ) — Total liabilities measured at fair value $ (67,242 ) $ — $ (5,397 ) $ (61,845 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See Note 6 , “Investment Information—Securities Lending Agreements.” (2) In accordance with applicable accounting guidance, 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 sheets. (3) See Note 8 , “Derivative Instruments.” The following table presents a reconciliation of the beginning and ending balances for all financial assets and liabilities measured at fair value on a recurring basis using Level 3 inputs: Assets Liabilities s Available For Sale Fair Value Option Asset Backed Securities Corporate Bonds Other Investments Other Investments Total Contingent Consideration Liabilities Three Months Ended September 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (71,256 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (9,596 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — — Sales — — — — — — Settlements — — — — — — Transfers in and/or out of Level 3 — — — — — — Balance at end of period $ 57,500 $ — $ — $ — $ 57,500 $ (80,852 ) Three Months Ended September 30, 2014 Balance at beginning of period $ — $ — $ — $ — $ — $ (53,099 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (5,562 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — — Sales — — — — — — Settlements — — — — — — Transfers in and/or out of Level 3 — — — — — — Balance at end of period $ — $ — $ — $ — $ — $ (58,661 ) Nine Months Ended September 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (61,845 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (17,939 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — (1,068 ) Sales — — — — — — Settlements — — — — — — Transfers in and/or out of Level 3 — — — — — — Balance at end of period $ 57,500 $ — $ — $ — $ 57,500 $ (80,852 ) Nine Months Ended September 30, 2014 Balance at beginning of period $ — $ 2,045 $ 170,420 $ 377,525 $ 549,990 $ — Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (16,899 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — (41,762 ) Sales — (2,045 ) — — (2,045 ) — Settlements — — — — — — Transfers in and/or out of Level 3 (2) — — (170,420 ) (377,525 ) (547,945 ) — Balance at end of period $ — $ — $ — $ — $ — $ (58,661 ) _________________________________________________ (1) Gains or losses on fixed maturities available for sale were included in net realized gains (losses) while gains or losses on other investments were included in net realized gains (losses) or net investment income. Gains or losses on contingent consideration liabilities were included in net realized gains (losses). (2) In accordance with applicable accounting guidance, 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 transfers out of Level 3 presented in this table are intended to permit reconciliation to information previously presented. Financial Instruments Disclosed, But Not Carried, At Fair Value The Company uses various financial instruments in the normal course of its business. The carrying values of cash, accrued investment income, receivable for securities sold, certain other assets, payable for securities purchased and certain other liabilities approximated their fair values at September 30, 2015 , due to their respective short maturities. As these financial instruments are not actively traded, their respective fair values are classified within Level 2. At September 30, 2015 , the senior notes of ACGL were carried at their cost, net of debt issuance costs, of $296.9 million and had a fair value of $387.6 million while the senior notes of Arch-U.S. were carried at their cost, net of debt issuance costs, of $494.4 million and had a fair value of $543.7 million . The fair values of the senior notes were obtained from a third party pricing service and are based on observable market inputs. As such, the fair value of the senior notes is classified within Level 2.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The Company’s investment strategy allows for the use of derivative securities. The Company’s derivative instruments are recorded on its consolidated balance sheets at fair value. The Company utilizes exchange traded U.S. Treasury note, Eurodollar and other futures contracts and commodity futures to manage portfolio duration or replicate investment positions in its portfolios and the Company routinely utilizes foreign currency forward contracts, currency options, index futures contracts and other derivatives as part of its total return objective. In addition, certain of the Company’s investments are managed in portfolios which incorporate the use of foreign currency forward contracts which are intended to provide an economic hedge against foreign currency movements. In addition, the Company purchases to-be-announced mortgage backed securities (“TBAs”) as part of its investment strategy. TBAs represent commitments to purchase a future issuance of agency mortgage backed securities. For the period between purchase of a TBA and issuance of the underlying security, the Company’s position is accounted for as a derivative. The Company purchases TBAs in both long and short positions to enhance investment performance and as part of its overall investment strategy. The Company did not hold any derivatives which were designated as hedging instruments at September 30, 2015 or December 31, 2014 . The following table summarizes information on the fair values and notional values of the Company’s derivative instruments. Estimated Fair Value Asset Liability Derivatives Net Notional Value (1) September 30, 2015 Futures contracts (2) $ 189 $ (3,528 ) $ (3,339 ) $ 1,702,327 Foreign currency forward contracts (2) 10,678 (7,235 ) 3,443 1,018,620 TBAs (3) 307,356 (290,865 ) 16,491 568,463 Other (2) 5,998 (27,264 ) (21,266 ) 1,446,622 Total $ 324,221 $ (328,892 ) $ (4,671 ) December 31, 2014 Futures contracts (2) $ 2,156 $ (1,907 ) $ 249 $ 2,549,027 Foreign currency forward contracts (2) 10,511 (1,145 ) 9,366 397,106 TBAs (3) 10,592 — 10,592 10,056 Other (2) 3,209 (2,345 ) 864 735,684 Total $ 26,468 $ (5,397 ) $ 21,071 _________________________________________________ (1) Represents the absolute notional value of all outstanding contracts, consisting of long and short positions. (2) The fair value of asset derivatives are included in ‘other assets’ and the fair value of liability derivatives are included in ‘other liabilities.’ (3) The fair value of TBAs are included in ‘fixed maturities available for sale, at fair value.’ The Company’s derivative instruments can be traded under master netting agreements, which establish terms that apply to all derivative transactions with a counterparty. In the event of a bankruptcy or other stipulated event of default, such agreements provide that the non-defaulting party may elect to terminate all outstanding derivative transactions, in which case all individual derivative positions (loss or gain) with a counterparty are closed out and netted and replaced with a single amount, usually referred to as the termination amount, which is expressed in a single currency. The resulting single net amount, where positive, is payable to the party “in-the-money” regardless of whether or not it is the defaulting party, unless the parties have agreed that only the non-defaulting party is entitled to receive a termination payment where the net amount is positive and is in its favor. Effectively, contractual close-out netting reduces derivatives credit exposure from gross to net exposure. At September 30, 2015 , asset derivatives and liability derivatives of $298.4 million and $309.6 million , respectively, were subject to a master netting agreement, compared to $25.3 million and $5.4 million , respectively, at December 31, 2014 . The remaining derivatives included in the table above were not subject to a master netting agreement. All realized and unrealized contract gains and losses on the Company’s derivative instruments are reflected in net realized gains (losses) in the consolidated statements of income, as summarized in the following table: Three Months Ended Nine Months Ended Derivatives not designated as September 30, September 30, hedging instruments: 2015 2014 2015 2014 Net realized gains (losses): Futures contracts $ 28,562 $ (354 ) $ 16,442 $ 4,969 Foreign currency forward contracts 5,395 6,558 13,490 2,490 TBAs 1,064 660 1,368 353 Other 868 585 (231 ) (729 ) Total $ 35,889 $ 7,449 $ 31,069 $ 7,083

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Letter of Credit and Revolving Credit Facilities As of September 30, 2015 , the Company had a $300 million unsecured revolving loan and letter of credit facility and a $500 million secured letter of credit facility (the “Credit Agreement”). The Credit Agreement expires on June 30, 2019 . In addition, the Company had access to secured letter of credit facilities of approximately $228.6 million as of September 30, 2015 , which are available on a limited basis and for limited purposes (together with the secured portion of the Credit Agreement and these letter of credit facilities, the “LOC Facilities”). At September 30, 2015 , the Company had $451.8 million in outstanding letters of credit under the LOC Facilities, which were secured by investments with a fair value of $517.4 million , and had $100.0 million of borrowings outstanding under the Credit Agreement. The Company was in compliance with all covenants contained in the LOC Facilities at September 30, 2015 . As of September 30, 2015 , Watford Re had a $100 million letter of credit facility expiring on May 19, 2016 and an $800 million secured credit facility expiring on June 4, 2018 , that provides for borrowings and the issuance of letters of credit not to exceed $400 million . At September 30, 2015 , Watford Re had $102.8 million in outstanding letters of credit under the two facilities and $239.1 million of borrowings outstanding under the secured credit facility, backed by Watford Re’s investment portfolio. Watford Re was in compliance with all covenants contained in both of its credit facilities at September 30, 2015 . The Company does not guarantee or provide credit support for Watford Re, and the Company’s financial exposure to Watford Re is limited to its investment in Watford Re’s common and preferred shares and counterparty credit risk (mitigated by collateral) arising from the reinsurance transactions. Investment Commitments The Company’s investment commitments, which are primarily related to agreements entered into by the Company to invest in funds and separately managed accounts when called upon, were approximately $1.23 billion at September 30, 2015 , compared to $968.9 million at December 31, 2014 .

Share Transactions

Share Transactions	9 Months Ended
	Sep. 30, 2015
Stockholders' Equity Note [Abstract]
Share Transactions	Share Transactions Share Repurchases The board of directors of ACGL has authorized the investment in ACGL’s common shares through a share repurchase program. Since the inception of the share repurchase program, ACGL has repurchased approximately 124.1 million common shares for an aggregate purchase price of $3.61 billion . During the nine months ended September 30, 2015 , ACGL repurchased 5.9 million common shares for an aggregate purchase price of $365.4 million , compared to 4.6 million common shares repurchased for an aggregate purchase price of $251.9 million during the 2014 period. At September 30, 2015 , $521.8 million of share repurchases were available under the program. The timing and amount of the repurchase transactions under this program will depend on a variety of factors, including market conditions and corporate and regulatory considerations.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes ACGL is incorporated under the laws of Bermuda and, under current Bermuda law, is not obligated to pay any taxes in Bermuda based upon income or capital gains. The Company has received a written undertaking from the Minister of Finance in Bermuda under the Exempted Undertakings Tax Protection Act 1966 that, in the event that any legislation is enacted in Bermuda imposing any tax computed on profits, income, gain or appreciation on any capital asset, or any tax in the nature of estate duty or inheritance tax, such tax will not be applicable to ACGL or any of its operations until March 31, 2035. This undertaking does not, however, prevent the imposition of taxes on any person ordinarily resident in Bermuda or any company in respect of its ownership of real property or leasehold interests in Bermuda. ACGL and its non-U.S. subsidiaries will be subject to U.S. federal income tax only to the extent that they derive U.S. source income that is subject to U.S. withholding tax or income that is effectively connected with the conduct of a trade or business within the U.S. and is not exempt from U.S. tax under an applicable income tax treaty with the U.S. ACGL and its non-U.S. subsidiaries will be subject to a withholding tax on dividends from U.S. investments and interest from certain U.S. payors (subject to reduction by any applicable income tax treaty). ACGL and its non-U.S. subsidiaries intend to conduct their operations in a manner that will not cause them to be treated as engaged in a trade or business in the United States and, therefore, will not be required to pay U.S. federal income taxes (other than U.S. excise taxes on insurance and reinsurance premium and withholding taxes on dividends and certain other U.S. source investment income). However, because there is uncertainty as to the activities which constitute being engaged in a trade or business within the United States, there can be no assurances that the U.S. Internal Revenue Service will not contend successfully that ACGL or its non-U.S. subsidiaries are engaged in a trade or business in the United States. If ACGL or any of its non-U.S. subsidiaries were subject to U.S. income tax, ACGL’s shareholders’ equity and earnings could be materially adversely affected. ACGL has subsidiaries and branches that operate in various jurisdictions around the world that are subject to tax in the jurisdictions in which they operate. The significant jurisdictions in which ACGL’s subsidiaries and branches are subject to tax are the United States, United Kingdom, Ireland, Canada, Switzerland and Denmark. The Company’s income tax provision on income before income taxes resulted in an expense of 5.5% for the nine months ended September 30, 2015 , compared to an expense of 2.8% for the 2014 period. The Company’s effective tax rate, which is based upon the expected annual effective tax rate, may fluctuate from period to period based on the relative mix of income or loss reported by jurisdiction and the varying tax rates in each jurisdiction. The Company had a net deferred tax asset of $139.9 million at September 30, 2015 , compared to $131.0 million at December 31, 2014 . In addition, the Company paid $35.5 million in income taxes for the nine months ended September 30, 2015 , while the Company paid $13.3 million for the 2014 period.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2015
Comprehensive Income Note Disclosure [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) The following tables present details about amounts reclassified from accumulated other comprehensive income and the tax effects allocated to each component of other comprehensive income (loss): Amounts Reclassified from AOCI Consolidated Statement of Income Three Months Ended Nine Months Ended Details About Line Item That Includes September 30, September 30, AOCI Components Reclassification 2015 2014 2015 2014 Unrealized appreciation on available-for-sale investments Net realized gains (losses) $ (2,019 ) $ 27,715 $ 63,671 $ 77,488 Other-than-temporary impairment losses (8,901 ) (8,593 ) (17,274 ) (26,313 ) Total before tax (10,920 ) 19,122 46,397 51,175 Income tax (expense) benefit (1,358 ) (1,639 ) (6,529 ) (4,158 ) Net of tax $ (12,278 ) $ 17,483 $ 39,868 $ 47,017 Before Tax Amount Tax Expense (Benefit) Net of Tax Amount Three Months Ended September 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (44,687 ) $ 9,204 $ (53,891 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (3,033 ) — (3,033 ) Less reclassification of net realized gains (losses) included in net income (10,920 ) 1,358 (12,278 ) Foreign currency translation adjustments (12,638 ) (556 ) (12,082 ) Other comprehensive income (loss) $ (49,438 ) $ 7,290 $ (56,728 ) Three Months Ended September 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (90,276 ) $ 343 $ (90,619 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 19,122 1,639 17,483 Foreign currency translation adjustments (23,595 ) — (23,595 ) Other comprehensive income (loss) $ (132,993 ) $ (1,296 ) $ (131,697 ) Nine Months Ended September 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (46,929 ) $ 4,593 $ (51,522 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (4,494 ) — (4,494 ) Less reclassification of net realized gains (losses) included in net income 46,397 6,529 39,868 Foreign currency translation adjustments (24,567 ) (1,308 ) (23,259 ) Other comprehensive income (loss) $ (122,387 ) $ (3,244 ) $ (119,143 ) Nine Months Ended September 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ 100,274 $ 11,112 $ 89,162 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 51,175 4,158 47,017 Foreign currency translation adjustments (14,923 ) — (14,923 ) Other comprehensive income (loss) $ 34,176 $ 6,954 $ 27,222

Guarantor Financial Information

Guarantor Financial Information	9 Months Ended
	Sep. 30, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Guarantor Financial Information	Guarantor Financial Information The following tables present condensed financial information for ACGL, Arch Capital Group (U.S.) Inc. (“Arch-U.S.”), a 100% owned subsidiary of ACGL, and ACGL’s other subsidiaries. September 30, 2015 Condensed Consolidating Balance Sheet ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Assets Total investments $ 34 $ 55,053 $ 15,775,050 $ (14,700 ) $ 15,815,437 Cash 10,381 9,256 630,142 — 649,779 Investments in subsidiaries 6,579,718 1,715,121 — (8,294,839 ) — Due from subsidiaries and affiliates — 48,548 442,508 (491,056 ) — Premiums receivable — — 1,521,960 (447,076 ) 1,074,884 Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses — — 5,739,246 (3,906,860 ) 1,832,386 Contractholder receivables — — 1,436,154 — 1,436,154 Prepaid reinsurance premiums — — 1,602,870 (1,160,524 ) 442,346 Deferred acquisition costs, net — — 448,893 — 448,893 Other assets 3,534 43,860 2,644,143 (620,824 ) 2,070,713 Total assets $ 6,593,667 $ 1,871,838 $ 30,240,966 $ (14,935,879 ) $ 23,770,592 Liabilities Reserve for losses and loss adjustment expenses $ — $ — $ 12,969,850 $ (3,884,995 ) $ 9,084,855 Unearned premiums — — 3,628,215 (1,160,524 ) 2,467,691 Reinsurance balances payable — — 669,285 (433,723 ) 235,562 Contractholder payables — — 1,436,154 — 1,436,154 Collateral held for insured obligations — — 242,928 — 242,928 Deposit accounting liabilities — — 482,756 (211,880 ) 270,876 Senior notes 296,854 494,410 — — 791,264 Revolving credit agreement borrowings 100,000 — 239,077 — 339,077 Due to subsidiaries and affiliates 14,080 35,000 441,976 (491,056 ) — Other liabilities 19,918 49,904 2,134,460 (444,163 ) 1,760,119 Total liabilities 430,852 579,314 22,244,701 (6,626,341 ) 16,628,526 Redeemable noncontrolling interests — — 219,789 (14,700 ) 205,089 Shareholders’ Equity Total shareholders’ equity available to Arch 6,162,815 1,292,524 7,002,314 (8,294,838 ) 6,162,815 Non-redeemable noncontrolling interests — — 774,162 — 774,162 Total shareholders’ equity 6,162,815 1,292,524 7,776,476 (8,294,838 ) 6,936,977 Total liabilities, noncontrolling interests and shareholders’ equity $ 6,593,667 $ 1,871,838 $ 30,240,966 $ (14,935,879 ) $ 23,770,592 December 31, 2014 Condensed Consolidating Balance Sheet ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Assets Total investments $ 107 $ 62,867 $ 15,257,796 $ — $ 15,320,770 Cash 3,218 2,787 479,697 — 485,702 Investments in subsidiaries 6,536,644 1,685,185 — (8,221,829 ) — Due from subsidiaries and affiliates 48 7,517 370,429 (377,994 ) — Premiums receivable — — 1,331,511 (382,816 ) 948,695 Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses — — 5,584,973 (3,772,128 ) 1,812,845 Contractholder receivables — — 1,309,192 — 1,309,192 Prepaid reinsurance premiums — — 1,373,008 (995,930 ) 377,078 Deferred acquisition costs, net — — 414,525 — 414,525 Other assets 4,386 43,921 1,705,546 (416,579 ) 1,337,274 Total assets $ 6,544,403 $ 1,802,277 $ 27,826,677 $ (14,167,276 ) $ 22,006,081 Liabilities Reserve for losses and loss adjustment expenses $ — $ — $ 12,784,030 $ (3,747,582 ) $ 9,036,448 Unearned premiums — — 3,227,508 (995,930 ) 2,231,578 Reinsurance balances payable — — 589,289 (369,977 ) 219,312 Contractholder payables — — 1,309,192 — 1,309,192 Collateral held for insured obligations — — 184,219 — 184,219 Deposit accounting liabilities — — 587,050 (259,666 ) 327,384 Senior notes 296,796 494,345 — — 791,141 Revolving credit agreement borrowings 100,000 — — — 100,000 Due to subsidiaries and affiliates 417 7,505 370,072 (377,994 ) — Other liabilities 17,137 49,403 815,919 (194,298 ) 688,161 Total liabilities 414,350 551,253 19,867,279 (5,945,447 ) 14,887,435 Redeemable noncontrolling interests — — 219,512 — 219,512 Shareholders’ Equity Total shareholders’ equity available to Arch 6,130,053 1,251,024 6,970,805 (8,221,829 ) 6,130,053 Non-redeemable noncontrolling interests — — 769,081 — 769,081 Total shareholders’ equity 6,130,053 1,251,024 7,739,886 (8,221,829 ) 6,899,134 Total liabilities, noncontrolling interests and shareholders’ equity $ 6,544,403 $ 1,802,277 $ 27,826,677 $ (14,167,276 ) $ 22,006,081 Three Months Ended September 30, 2015 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 936,683 $ — $ 936,683 Net investment income — 764 92,773 (7,304 ) 86,233 Net realized gains (losses) — — (89,698 ) — (89,698 ) Net impairment losses recognized in earnings — — (5,868 ) — (5,868 ) Other underwriting income — — 7,623 — 7,623 Equity in net income (loss) of investment funds accounted for using the equity method — — (2,118 ) — (2,118 ) Other income (loss) — — (265 ) — (265 ) Total revenues — 764 939,130 (7,304 ) 932,590 Expenses Losses and loss adjustment expenses — — 531,741 — 531,741 Acquisition expenses — — 171,566 — 171,566 Other operating expenses 10,536 720 145,703 — 156,959 Interest expense 5,863 6,689 7,734 (6,986 ) 13,300 Net foreign exchange (gains) losses — — (11,762 ) (2,918 ) (14,680 ) Total expenses 16,399 7,409 844,982 (9,904 ) 858,886 Income (loss) before income taxes (16,399 ) (6,645 ) 94,148 2,600 73,704 Income tax (expense) benefit — 2,324 (12,028 ) — (9,704 ) Income (loss) before equity in net income of subsidiaries (16,399 ) (4,321 ) 82,120 2,600 64,000 Equity in net income of subsidiaries 96,432 13,620 — (110,052 ) — Net income 80,033 9,299 82,120 (107,452 ) 64,000 Amounts attributable to noncontrolling interests — — 15,712 321 16,033 Net income available to Arch 80,033 9,299 97,832 (107,131 ) 80,033 Preferred dividends (5,484 ) — — — (5,484 ) Net income available to Arch common shareholders $ 74,549 $ 9,299 $ 97,832 $ (107,131 ) $ 74,549 Comprehensive income (loss) available to Arch $ 23,401 $ 15,705 $ 44,127 $ (59,832 ) $ 23,401 Three Months Ended September 30, 2014 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 903,651 $ — $ 903,651 Net investment income — — 79,936 169 80,105 Net realized gains (losses) — — 18,515 — 18,515 Net impairment losses recognized in earnings — — (8,593 ) — (8,593 ) Other underwriting income — — 1,702 — 1,702 Equity in net income (loss) of investment funds accounted for using the equity method — — 4,966 — 4,966 Other income (loss) — — (7,815 ) — (7,815 ) Total revenues — — 992,362 169 992,531 Expenses Losses and loss adjustment expenses — — 501,673 — 501,673 Acquisition expenses — — 163,547 — 163,547 Other operating expenses 10,056 810 138,614 — 149,480 Interest expense 5,858 6,433 (8,308 ) 169 4,152 Net foreign exchange (gains) losses — — (35,244 ) (20,787 ) (56,031 ) Total expenses 15,914 7,243 760,282 (20,618 ) 762,821 Income (loss) before income taxes (15,914 ) (7,243 ) 232,080 20,787 229,710 Income tax (expense) benefit — 2,097 (8,543 ) — (6,446 ) Income (loss) before equity in net income of subsidiaries (15,914 ) (5,146 ) 223,537 20,787 223,264 Equity in net income of subsidiaries 244,589 10,459 — (255,048 ) — Net income 228,675 5,313 223,537 (234,261 ) 223,264 Amounts attributable to noncontrolling interests — — 5,411 — 5,411 Net income available to Arch 228,675 5,313 228,948 (234,261 ) 228,675 Preferred dividends (5,484 ) — — — (5,484 ) Net income available to Arch common shareholders $ 223,191 $ 5,313 $ 228,948 $ (234,261 ) $ 223,191 Comprehensive income (loss) available to Arch $ 96,978 $ (10,614 ) $ 104,501 $ (93,887 ) $ 96,978 Nine Months Ended September 30, 2015 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 2,790,385 $ — $ 2,790,385 Net investment income — 1,569 265,937 (15,316 ) 252,190 Net realized gains (losses) — 1 (42,076 ) — (42,075 ) Net impairment losses recognized in earnings — — (12,780 ) — (12,780 ) Other underwriting income — — 26,876 — 26,876 Equity in net income (loss) of investment funds accounted for using the equity method — — 19,938 — 19,938 Other income (loss) — — 52 — 52 Total revenues — 1,570 3,048,332 (15,316 ) 3,034,586 Expenses Losses and loss adjustment expenses — — 1,544,883 — 1,544,883 Acquisition expenses — — 510,067 — 510,067 Other operating expenses 36,068 2,991 444,390 — 483,449 Interest expense 17,581 19,824 7,476 (14,834 ) 30,047 Net foreign exchange (gains) losses — — (44,450 ) (17,148 ) (61,598 ) Total expenses 53,649 22,815 2,462,366 (31,982 ) 2,506,848 Income (loss) before income taxes (53,649 ) (21,245 ) 585,966 16,666 527,738 Income tax (expense) benefit — 7,434 (36,596 ) — (29,162 ) Income (loss) before equity in net income of subsidiaries (53,649 ) (13,811 ) 549,370 16,666 498,576 Equity in net income of subsidiaries 532,808 42,192 — (575,000 ) — Net income 479,159 28,381 549,370 (558,334 ) 498,576 Amounts attributable to noncontrolling interests — — (19,902 ) 485 (19,417 ) Net income available to Arch 479,159 28,381 529,468 (557,849 ) 479,159 Preferred dividends (16,453 ) — — — (16,453 ) Net income available to Arch common shareholders $ 462,706 $ 28,381 $ 529,468 $ (557,849 ) $ 462,706 Comprehensive income (loss) available to Arch $ 360,112 $ 13,950 $ 427,569 $ (441,519 ) $ 360,112 Nine Months Ended September 30, 2014 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 2,670,583 $ — $ 2,670,583 Net investment income — — 237,317 (17,228 ) 220,089 Net realized gains (losses) — — 92,356 — 92,356 Net impairment losses recognized in earnings — — (26,313 ) — (26,313 ) Other underwriting income — — 5,317 — 5,317 Equity in net income (loss) of investment funds accounted for using the equity method — — 17,459 — 17,459 Other income (loss) — — (5,069 ) — (5,069 ) Total revenues — — 2,991,650 (17,228 ) 2,974,422 Expenses Losses and loss adjustment expenses — — 1,423,431 — 1,423,431 Acquisition expenses — — 482,047 — 482,047 Other operating expenses 35,613 2,281 413,735 — 451,629 Interest expense 17,565 19,395 13,158 (17,228 ) 32,890 Net foreign exchange (gains) losses — — (28,449 ) (18,725 ) (47,174 ) Total expenses 53,178 21,676 2,303,922 (35,953 ) 2,342,823 Income (loss) before income taxes (53,178 ) (21,676 ) 687,728 18,725 631,599 Income tax (expense) benefit — 8,179 (25,652 ) — (17,473 ) Income (loss) before equity in net income of subsidiaries (53,178 ) (13,497 ) 662,076 18,725 614,126 Equity in net income of subsidiaries 672,369 41,945 — (714,314 ) — Net income 619,191 28,448 662,076 (695,589 ) 614,126 Amounts attributable to noncontrolling interests — — 5,065 — 5,065 Net income available to Arch 619,191 28,448 667,141 (695,589 ) 619,191 Preferred dividends (16,453 ) — — — (16,453 ) Net income available to Arch common shareholders $ 602,738 $ 28,448 $ 667,141 $ (695,589 ) $ 602,738 Comprehensive income (loss) available to Arch $ 646,413 $ 29,792 $ 691,968 $ (721,760 ) $ 646,413 Nine Months Ended September 30, 2015 Condensed Consolidating Statement of Cash Flows ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Operating Activities Net Cash Provided By (Used For) Operating Activities $ 382,329 $ 10,622 $ 859,525 $ (444,897 ) $ 807,579 Investing Activities Purchases of fixed maturity investments — (3,505 ) (22,378,599 ) — (22,382,104 ) Purchases of equity securities (8,070 ) — (477,456 ) — (485,526 ) Purchases of other investments — — (1,320,250 ) — (1,320,250 ) Proceeds from the sales of fixed maturity investments — 23,507 21,388,047 — 21,411,554 Proceeds from the sales of equity securities — — 509,008 — 509,008 Proceeds from the sales, redemptions and maturities of other investments — — 858,368 — 858,368 Proceeds from redemptions and maturities of fixed maturity investments — — 630,397 — 630,397 Net settlements of derivative instruments — — 81,114 — 81,114 Proceeds from investment in joint venture — — 40,000 — 40,000 Net (purchases) sales of short-term investments 73 (12,183 ) 193,851 — 181,741 Change in cash collateral related to securities lending — — 28,685 — 28,685 Contributions to subsidiaries — — (9,290 ) 9,290 — Intercompany loans issued — (39,500 ) (41,523 ) 81,023 — Purchase of business, net of cash acquired — — 818 — 818 Purchases of fixed assets (53 ) — (10,848 ) — (10,901 ) Change in other assets — — (43,654 ) — (43,654 ) Net Cash Provided By (Used For) Investing Activities (8,050 ) (31,681 ) (551,332 ) 90,313 (500,750 ) Financing Activities Purchases of common shares under share repurchase program (365,383 ) — — — (365,383 ) Proceeds from common shares issued, net 697 — 9,290 (9,290 ) 697 Proceeds from intercompany borrowings 14,023 27,500 39,500 (81,023 ) — Proceeds from borrowings — — 239,077 — 239,077 Change in cash collateral related to securities lending — — (28,685 ) — (28,685 ) Dividends paid to redeemable noncontrolling interests — — (14,447 ) 637 (13,810 ) Dividends paid to parent — — (444,260 ) 444,260 — Other — 28 50,435 — 50,463 Preferred dividends paid (16,453 ) — — — (16,453 ) Net Cash Provided By (Used For) Financing Activities (367,116 ) 27,528 (149,090 ) 354,584 (134,094 ) Effects of exchange rates changes on foreign currency cash — — (8,658 ) — (8,658 ) Increase (decrease) in cash 7,163 6,469 150,445 — 164,077 Cash beginning of year 3,218 2,787 479,697 — 485,702 Cash end of period $ 10,381 $ 9,256 $ 630,142 $ — $ 649,779 Nine Months Ended September 30, 2014 Condensed Consolidating Statement of Cash Flows ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Operating Activities Net Cash Provided By (Used For) Operating Activities $ 265,694 $ 8,407 $ 822,558 $ (297,000 ) $ 799,659 Investing Activities Purchases of fixed maturity investments — (78,509 ) (21,952,353 ) — (22,030,862 ) Purchases of equity securities — — (366,578 ) — (366,578 ) Purchases of other investments — — (1,136,285 ) — (1,136,285 ) Proceeds from the sales of fixed maturity investments — — 20,273,351 — 20,273,351 Proceeds from the sales of equity securities — — 305,034 — 305,034 Proceeds from the sales, redemptions and maturities of other investments — — 566,518 — 566,518 Proceeds from redemptions and maturities of fixed maturity investments — — 636,729 — 636,729 Net settlements of derivative instruments — — 15,495 — 15,495 Net (purchases) sales of short-term investments 2,396 408,760 267,232 — 678,388 Change in cash collateral related to securities lending — — (2,737 ) — (2,737 ) Contributions to subsidiaries — (313,207 ) (100,000 ) 413,207 — Intercompany loans issued — — 10,250 (10,250 ) — Purchase of business, net of cash acquired — — (235,578 ) — (235,578 ) Purchases of fixed assets (220 ) — (14,355 ) — (14,575 ) Change in other assets — — — — — Net Cash Provided By (Used For) Investing Activities 2,176 17,044 (1,733,277 ) 402,957 (1,311,100 ) Financing Activities Purchases of common shares under share repurchase program (251,919 ) — — — (251,919 ) Proceeds from common shares issued, net 3,248 — 413,207 (413,207 ) 3,248 Repayments of intercompany borrowings — (10,250 ) — 10,250 — Change in cash collateral related to securities lending — — 2,737 — 2,737 Third party investment in non-redeemable noncontrolling interests — — 796,903 — 796,903 Third party investment in redeemable noncontrolling interests — — 219,233 — 219,233 Dividends paid to redeemable noncontrolling interests — — (9,632 ) — (9,632 ) Dividends paid to parent — — (297,000 ) 297,000 — Other — — 6,559 — 6,559 Preferred dividends paid (16,453 ) — — — (16,453 ) Net Cash Provided By (Used For) Financing Activities (265,124 ) (10,250 ) 1,132,007 (105,957 ) 750,676 Effects of exchange rates changes on foreign currency cash — — (9,566 ) — (9,566 ) Increase (decrease) in cash 2,746 15,201 211,722 — 229,669 Cash beginning of year 3,223 509 430,325 — 434,057 Cash end of period $ 5,969 $ 15,710 $ 642,047 $ — $ 663,726

Legal Proceedings

Legal Proceedings	9 Months Ended
	Sep. 30, 2015
Disclosure Legal Proceedings [Abstract]
Legal Proceedings	Legal Proceedings The Company, in common with the insurance industry in general, is subject to litigation and arbitration in the normal course of its business. As of September 30, 2015 , the Company was not a party to any litigation or arbitration which is expected by management to have a material adverse effect on the Company’s results of operations and financial condition and liquidity.

Transactions with Related Parti

Transactions with Related Parties	9 Months Ended
	Sep. 30, 2015
Related Party Transactions [Abstract]
Transactions with Related Parties	Transactions with Related Parties Kewsong Lee, a director of ACGL, is a Managing Director and Deputy Chief Investment Officer for Corporate Private Equity of The Carlyle Group (“Carlyle”). As part of its investment philosophy, the Company invests a portion of its investment portfolio in alternative investment funds. As of September 30, 2015 , the Company had aggregate commitments of $670.9 million to funds managed by Carlyle, of which $462.4 million was unfunded. The Company may make additional commitments to funds managed by Carlyle from time to time. During the nine months ended September 30, 2015 and 2014 , the Company made aggregate capital contributions to funds managed by Carlyle of $97.7 million and $55.5 million , respectively. During the nine months ended September 30, 2015 and 2014 , the Company received aggregate cash distributions from funds managed by Carlyle of $30.3 million and $41.0 million , respectively, of which $25.5 million and $32.8 million , respectively, represented a return of capital.

General (Policies)

General (Policies)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). All significant intercompany transactions and balances have been eliminated in consolidation.
Use of estimates	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and assumptions. In the opinion of management, the accompanying unaudited interim consolidated financial statements reflect all adjustments (consisting of normally recurring accruals) necessary for a fair statement of results on an interim basis. The results of any interim period are not necessarily indicative of the results for a full year or any future periods.

Variable Interest Entities an24

Variable Interest Entities and Noncontrolling Interests (Tables)	9 Months Ended
	Sep. 30, 2015
Noncontrolling Interest [Abstract]
Activity in non-redeemable noncontrolling interests	The following table sets forth activity in the non-redeemable noncontrolling interests: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Balance, beginning of period $ 794,880 $ 792,340 $ 769,081 $ — Sale of shares to noncontrolling interests — — — 796,903 Amounts attributable to noncontrolling interests (20,621 ) (10,320 ) 5,178 (14,883 ) Foreign currency translation adjustments (97 ) — (97 ) — Balance, end of period $ 774,162 $ 782,020 $ 774,162 $ 782,020
Activity in redeemable noncontrolling interests	The following table sets forth activity in the redeemable non-controlling interests: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Balance, beginning of period $ 204,996 $ 219,326 $ 219,512 $ — Sale of shares to noncontrolling interests — — — 219,233 Shares acquired by the Company (1) — — (14,700 ) — Accretion of preference share issuance costs 93 93 277 186 Balance, end of period $ 205,089 $ 219,419 $ 205,089 $ 219,419 _________________________________________________ (1) During the 2015 second quarter, the Company acquired Gulf Re, which owns 600,000 Watford Preference Shares. Such shares, net of a discount, along with related dividends and accretion of the discount, are eliminated in consolidation.
Portion of income or loss attributable to third party investors	The portion of Watford Re’s income or loss attributable to third party investors is recorded in the consolidated statements of income in ‘amounts attributable to noncontrolling interests’ as summarized in the table below: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Amounts attributable to non-redeemable noncontrolling interests $ 20,621 $ 10,320 $ (5,178 ) $ 14,883 Dividends attributable to redeemable noncontrolling interests (4,588 ) (4,909 ) (14,239 ) (9,818 ) Amounts attributable to noncontrolling interests $ 16,033 $ 5,411 $ (19,417 ) $ 5,065

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2015
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 Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Numerator: Net income $ 64,000 $ 223,264 $ 498,576 $ 614,126 Amounts attributable to noncontrolling interests 16,033 5,411 (19,417 ) 5,065 Net income available to Arch 80,033 228,675 479,159 619,191 Preferred dividends (5,484 ) (5,484 ) (16,453 ) (16,453 ) Net income available to Arch common shareholders $ 74,549 $ 223,191 $ 462,706 $ 602,738 Denominator: Weighted average common shares outstanding — basic 120,567,410 131,945,962 122,151,971 132,151,824 Effect of dilutive common share equivalents: Nonvested restricted shares 1,322,053 1,156,790 1,260,247 1,134,481 Stock options (1) 3,122,310 2,773,853 2,942,541 3,067,867 Weighted average common shares and common share equivalents outstanding — diluted 125,011,773 135,876,605 126,354,759 136,354,172 Earnings per common share: Basic $ 0.62 $ 1.69 $ 3.79 $ 4.56 Diluted $ 0.60 $ 1.64 $ 3.66 $ 4.42 _________________________________________________ (1) Certain stock options were not included in the computation of diluted earnings per share where the exercise price of the stock options exceeded the average market price and would have been anti-dilutive or where, when applying the treasury stock method to in-the-money options, the sum of the proceeds, including unrecognized compensation, exceeded the average market price and would have been anti-dilutive. For the 2015 third quarter and 2014 third quarter , the number of stock options excluded were 390,406 and 1,355,087 , respectively. For the nine months ended September 30, 2015 and 2014 , the number of stock options excluded were 957,838 and 1,378,249 , respectively.

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Analysis of underwriting income or loss by segment and reconciliation to net income available to common shareholders	The following tables summarize the Company’s underwriting income or loss by segment, together with a reconciliation of underwriting income or loss to net income available to common shareholders: Three Months Ended September 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 752,438 $ 329,327 $ 74,657 $ 1,158,451 $ 131,165 $ 1,189,192 Premiums ceded (209,443 ) (92,182 ) (7,832 ) (311,486 ) (6,158 ) (217,220 ) Net premiums written 542,995 237,145 66,825 846,965 125,007 971,972 Change in unearned premiums (20,451 ) 23,286 (12,277 ) (9,442 ) (25,847 ) (35,289 ) Net premiums earned 522,544 260,431 54,548 837,523 99,160 936,683 Other underwriting income 519 2,783 3,565 6,867 756 7,623 Losses and loss adjustment expenses (339,859 ) (115,780 ) (9,562 ) (465,201 ) (66,540 ) (531,741 ) Acquisition expenses, net (77,076 ) (55,416 ) (10,428 ) (142,920 ) (28,646 ) (171,566 ) Other operating expenses (84,620 ) (37,131 ) (21,048 ) (142,799 ) (3,421 ) (146,220 ) Underwriting income (loss) $ 21,508 $ 54,887 $ 17,075 93,470 1,309 94,779 Net investment income 67,251 18,982 86,233 Net realized gains (losses) (53,480 ) (36,218 ) (89,698 ) Net impairment losses recognized in earnings (5,868 ) — (5,868 ) Equity in net income (loss) of investment funds accounted for using the equity method (2,118 ) — (2,118 ) Other income (loss) (265 ) — (265 ) Other expenses (10,739 ) — (10,739 ) Interest expense (12,014 ) (1,286 ) (13,300 ) Net foreign exchange gains (losses) 16,056 (1,376 ) 14,680 Income (loss) before income taxes 92,293 (18,589 ) 73,704 Income tax expense (9,704 ) — (9,704 ) Net income (loss) 82,589 (18,589 ) 64,000 Dividends attributable to redeemable noncontrolling interests — (4,588 ) (4,588 ) Amounts attributable to noncontrolling interests — 20,621 20,621 Net income (loss) available to Arch 82,589 (2,556 ) 80,033 Preferred dividends (5,484 ) — (5,484 ) Net income (loss) available to Arch common shareholders $ 77,105 $ (2,556 ) $ 74,549 Underwriting Ratios Loss ratio 65.0 % 44.5 % 17.5 % 55.5 % 67.1 % 56.8 % Acquisition expense ratio 14.8 % 21.3 % 19.1 % 17.1 % 28.9 % 18.3 % Other operating expense ratio 16.2 % 14.3 % 38.6 % 17.1 % 3.4 % 15.6 % Combined ratio 96.0 % 80.1 % 75.2 % 89.7 % 99.4 % 90.7 % Goodwill and intangible assets $ 29,834 $ 2,149 $ 71,637 $ 103,620 $ — $ 103,620 Total investable assets $ 14,733,732 $ 1,593,523 $ 16,327,255 Total assets 21,679,795 2,090,797 23,770,592 Total liabilities 15,627,574 1,000,952 16,628,526 _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total. Three Months Ended September 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 726,683 $ 345,747 $ 66,389 $ 1,138,392 $ 103,483 $ 1,159,907 Premiums ceded (187,689 ) (83,502 ) (7,904 ) (278,668 ) (3,668 ) (200,368 ) Net premiums written 538,994 262,245 58,485 859,724 99,815 959,539 Change in unearned premiums (19,607 ) 34,303 (5,539 ) 9,157 (65,045 ) (55,888 ) Net premiums earned 519,387 296,548 52,946 868,881 34,770 903,651 Other underwriting income 499 215 988 1,702 — 1,702 Losses and loss adjustment expenses (338,319 ) (123,784 ) (15,987 ) (478,090 ) (23,583 ) (501,673 ) Acquisition expenses, net (81,775 ) (60,205 ) (11,958 ) (153,938 ) (9,609 ) (163,547 ) Other operating expenses (83,138 ) (36,337 ) (17,913 ) (137,388 ) (1,658 ) (139,046 ) Underwriting income (loss) $ 16,654 $ 76,437 $ 8,076 101,167 (80 ) 101,087 Net investment income 72,239 7,866 80,105 Net realized gains (losses) 31,411 (12,896 ) 18,515 Net impairment losses recognized in earnings (8,593 ) — (8,593 ) Equity in net income (loss) of investment funds accounted for using the equity method 4,966 — 4,966 Other income (loss) (7,815 ) — (7,815 ) Other expenses (10,434 ) — (10,434 ) Interest expense (4,152 ) — (4,152 ) Net foreign exchange gains (losses) 57,611 (1,580 ) 56,031 Income (loss) before income taxes 236,400 (6,690 ) 229,710 Income tax expense (6,446 ) — (6,446 ) Net income (loss) 229,954 (6,690 ) 223,264 Dividends attributable to redeemable noncontrolling interests — (4,909 ) (4,909 ) Amounts attributable to noncontrolling interests — 10,320 10,320 Net income (loss) available to Arch 229,954 (1,279 ) 228,675 Preferred dividends (5,484 ) — (5,484 ) Net income (loss) available to Arch common shareholders $ 224,470 $ (1,279 ) $ 223,191 Underwriting Ratios Loss ratio 65.1 % 41.7 % 30.2 % 55.0 % 67.8 % 55.5 % Acquisition expense ratio 15.7 % 20.3 % 22.6 % 17.7 % 27.6 % 18.1 % Other operating expense ratio 16.0 % 12.3 % 33.8 % 15.8 % 4.8 % 15.4 % Combined ratio 96.8 % 74.3 % 86.6 % 88.5 % 100.2 % 89.0 % Goodwill and intangible assets $ 24,024 $ 3,939 $ 83,565 $ 111,528 $ — $ 111,528 Total investable assets $ 14,580,425 $ 1,124,048 $ 15,704,473 Total assets 21,205,209 1,403,018 22,608,227 Total liabilities 15,221,030 304,712 15,525,742 _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total. Nine Months Ended September 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 2,263,401 $ 1,156,540 $ 203,770 $ 3,625,382 $ 387,752 $ 3,730,423 Premiums ceded (669,336 ) (318,197 ) (23,404 ) (1,012,608 ) (17,979 ) (747,876 ) Net premiums written 1,594,065 838,343 180,366 2,612,774 369,773 2,982,547 Change in unearned premiums (53,782 ) (24,230 ) (22,992 ) (101,004 ) (91,158 ) (192,162 ) Net premiums earned 1,540,283 814,113 157,374 2,511,770 278,615 2,790,385 Other underwriting income 1,467 6,870 14,969 23,306 3,570 26,876 Losses and loss adjustment expenses (978,681 ) (339,495 ) (33,010 ) (1,351,186 ) (193,697 ) (1,544,883 ) Acquisition expenses, net (228,877 ) (170,380 ) (31,046 ) (430,303 ) (79,764 ) (510,067 ) Other operating expenses (261,793 ) (114,182 ) (61,096 ) (437,071 ) (8,876 ) (445,947 ) Underwriting income (loss) $ 72,399 $ 196,926 $ 47,191 316,516 (152 ) 316,364 Net investment income 204,710 47,480 252,190 Net realized gains (losses) (14,831 ) (27,244 ) (42,075 ) Net impairment losses recognized in earnings (12,780 ) — (12,780 ) Equity in net income (loss) of investment funds accounted for using the equity method 19,938 — 19,938 Other income (loss) 52 — 52 Other expenses (37,502 ) — (37,502 ) Interest expense (28,761 ) (1,286 ) (30,047 ) Net foreign exchange gains (losses) 60,338 1,260 61,598 Income (loss) before income taxes 507,680 20,058 527,738 Income tax expense (29,162 ) — (29,162 ) Net income (loss) 478,518 20,058 498,576 Dividends attributable to redeemable noncontrolling interests — (14,239 ) (14,239 ) Amounts attributable to noncontrolling interests — (5,178 ) (5,178 ) Net income (loss) available to Arch 478,518 641 479,159 Preferred dividends (16,453 ) — (16,453 ) Net income (loss) available to Arch common shareholders $ 462,065 $ 641 $ 462,706 Underwriting Ratios Loss ratio 63.5 % 41.7 % 21.0 % 53.8 % 69.5 % 55.4 % Acquisition expense ratio 14.9 % 20.9 % 19.7 % 17.1 % 28.6 % 18.3 % Other operating expense ratio 17.0 % 14.0 % 38.8 % 17.4 % 3.2 % 16.0 % Combined ratio 95.4 % 76.6 % 79.5 % 88.3 % 101.3 % 89.7 % _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total. Nine Months Ended September 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 2,309,560 $ 1,212,641 $ 169,772 $ 3,690,462 $ 190,239 $ 3,726,804 Premiums ceded (646,082 ) (215,623 ) (17,622 ) (877,816 ) (6,428 ) (730,347 ) Net premiums written 1,663,478 997,018 152,150 2,812,646 183,811 2,996,457 Change in unearned premiums (158,878 ) (23,495 ) (9,606 ) (191,979 ) (133,895 ) (325,874 ) Net premiums earned 1,504,600 973,523 142,544 2,620,667 49,916 2,670,583 Other underwriting income 1,513 834 2,970 5,317 — 5,317 Losses and loss adjustment expenses (936,615 ) (413,745 ) (39,938 ) (1,390,298 ) (33,133 ) (1,423,431 ) Acquisition expenses, net (235,156 ) (199,673 ) (32,593 ) (467,422 ) (14,625 ) (482,047 ) Other operating expenses (250,111 ) (110,198 ) (48,077 ) (408,386 ) (4,402 ) (412,788 ) Underwriting income (loss) $ 84,231 $ 250,741 $ 24,906 359,878 (2,244 ) 357,634 Net investment income 211,690 8,399 220,089 Net realized gains (losses) 102,074 (9,718 ) 92,356 Net impairment losses recognized in earnings (26,313 ) — (26,313 ) Equity in net income (loss) of investment funds accounted for using the equity method 17,459 — 17,459 Other income (loss) (5,069 ) — (5,069 ) Other expenses (36,512 ) (2,329 ) (38,841 ) Interest expense (32,890 ) — (32,890 ) Net foreign exchange gains (losses) 48,191 (1,017 ) 47,174 Income (loss) before income taxes 638,508 (6,909 ) 631,599 Income tax expense (17,473 ) — (17,473 ) Net income (loss) 621,035 (6,909 ) 614,126 Dividends attributable to redeemable noncontrolling interests — (9,818 ) (9,818 ) Amounts attributable to noncontrolling interests — 14,883 14,883 Net income (loss) available to Arch 621,035 (1,844 ) 619,191 Preferred dividends (16,453 ) — (16,453 ) Net income (loss) available to Arch common shareholders $ 604,582 $ (1,844 ) $ 602,738 Underwriting Ratios Loss ratio 62.3 % 42.5 % 28.0 % 53.1 % 66.4 % 53.3 % Acquisition expense ratio 15.6 % 20.5 % 22.9 % 17.8 % 29.3 % 18.1 % Other operating expense ratio 16.6 % 11.3 % 33.7 % 15.6 % 8.8 % 15.5 % Combined ratio 94.5 % 74.3 % 84.6 % 86.5 % 104.5 % 86.9 % _________________________________________________ (1) Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total.

Investment Information (Tables)

Investment Information (Tables)	9 Months Ended
	Sep. 30, 2015
Disclosure Investment Information [Abstract]
Summary of fair value and cost or amortized cost of available for sale securities	The following table summarizes the fair value and cost or amortized cost of the Company’s investments classified as available for sale: Estimated Fair Value Gross Unrealized Gains Gross Unrealized Losses Cost or Amortized Cost OTTI Unrealized Losses (2) September 30, 2015 Fixed maturities (1): Corporate bonds $ 2,796,038 $ 28,418 $ (54,489 ) $ 2,822,109 $ (3,033 ) Mortgage backed securities 809,876 13,155 (2,998 ) 799,719 (3,554 ) Municipal bonds 1,830,987 27,600 (2,771 ) 1,806,158 — Commercial mortgage backed securities 810,973 10,058 (2,594 ) 803,509 — U.S. government and government agencies 2,338,724 14,352 (2,138 ) 2,326,510 — Non-U.S. government securities 887,120 13,070 (36,488 ) 910,538 — Asset backed securities 1,372,549 9,032 (4,850 ) 1,368,367 (22 ) Total 10,846,267 115,685 (106,328 ) 10,836,910 (6,609 ) Equity securities 606,259 68,494 (37,527 ) 575,292 — Other investments 281,014 39,287 (3,629 ) 245,356 — Short-term investments 708,428 166 (3,128 ) 711,390 — Total $ 12,441,968 $ 223,632 $ (150,612 ) $ 12,368,948 $ (6,609 ) December 31, 2014 Fixed maturities (1): Corporate bonds $ 3,108,513 $ 37,928 $ (38,974 ) $ 3,109,559 $ (317 ) Mortgage backed securities 943,343 18,843 (3,842 ) 928,342 (3,307 ) Municipal bonds 1,494,122 31,227 (1,044 ) 1,463,939 — Commercial mortgage backed securities 1,114,528 14,594 (3,822 ) 1,103,756 — U.S. government and government agencies 1,447,972 8,345 (1,760 ) 1,441,387 — Non-U.S. government securities 1,015,153 21,311 (37,203 ) 1,031,045 — Asset backed securities 1,677,941 8,425 (6,089 ) 1,675,605 (22 ) Total 10,801,572 140,673 (92,734 ) 10,753,633 (3,646 ) Equity securities 658,182 109,012 (13,364 ) 562,534 — Other investments 296,224 31,839 (362 ) 264,747 — Short-term investments 797,226 738 (5,270 ) 801,758 — Total $ 12,553,204 $ 282,262 $ (111,730 ) $ 12,382,672 $ (3,646 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.” (2) Represents the total other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income (“AOCI”). It does not include the change in fair value subsequent to the impairment measurement date. At September 30, 2015 , the net unrealized loss related to securities for which a non-credit OTTI was recognized in AOCI was $2.3 million , compared to a net unrealized gain of $0.9 million at December 31, 2014 .
Summary of available for sale securities in a continual unrealized loss position	The following table summarizes, for all available for sale securities in an unrealized loss position, the fair value and gross unrealized loss by length of time the security has been in a continual unrealized loss position: Less than 12 Months 12 Months or More Total Estimated Gross Unrealized Losses Estimated Gross Unrealized Losses Estimated Gross Unrealized Losses September 30, 2015 Fixed maturities (1): Corporate bonds $ 1,208,894 $ (37,606 ) $ 135,135 $ (16,883 ) $ 1,344,029 $ (54,489 ) Mortgage backed securities 235,252 (1,986 ) 52,621 (1,012 ) 287,873 (2,998 ) Municipal bonds 219,610 (2,567 ) 9,717 (204 ) 229,327 (2,771 ) Commercial mortgage backed securities 263,779 (2,376 ) 19,774 (218 ) 283,553 (2,594 ) U.S. government and government agencies 283,534 (2,138 ) — — 283,534 (2,138 ) Non-U.S. government securities 391,631 (23,526 ) 52,976 (12,962 ) 444,607 (36,488 ) Asset backed securities 467,485 (3,262 ) 126,982 (1,588 ) 594,467 (4,850 ) Total 3,070,185 (73,461 ) 397,205 (32,867 ) 3,467,390 (106,328 ) Equity securities 311,608 (37,527 ) — — 311,608 (37,527 ) Other investments 45,151 (3,629 ) — — 45,151 (3,629 ) Short-term investments 33,873 (3,128 ) — — 33,873 (3,128 ) Total $ 3,460,817 $ (117,745 ) $ 397,205 $ (32,867 ) $ 3,858,022 $ (150,612 ) December 31, 2014 Fixed maturities (1): Corporate bonds $ 1,309,637 $ (32,903 ) $ 148,963 $ (6,071 ) $ 1,458,600 $ (38,974 ) Mortgage backed securities 293,624 (1,476 ) 59,107 (2,366 ) 352,731 (3,842 ) Municipal bonds 210,614 (588 ) 13,643 (456 ) 224,257 (1,044 ) Commercial mortgage backed securities 232,147 (770 ) 125,894 (3,052 ) 358,041 (3,822 ) U.S. government and government agencies 618,381 (1,626 ) 3,438 (134 ) 621,819 (1,760 ) Non-U.S. government securities 510,766 (31,172 ) 46,910 (6,031 ) 557,676 (37,203 ) Asset backed securities 612,950 (2,486 ) 243,452 (3,603 ) 856,402 (6,089 ) Total 3,788,119 (71,021 ) 641,407 (21,713 ) 4,429,526 (92,734 ) Equity securities 181,002 (13,364 ) — — 181,002 (13,364 ) Other investments 59,638 (362 ) — — 59,638 (362 ) Short-term investments 79,271 (5,270 ) — — 79,271 (5,270 ) Total $ 4,108,030 $ (90,017 ) $ 641,407 $ (21,713 ) $ 4,749,437 $ (111,730 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.”
Contractual maturities of the Company's fixed maturities and fixed maturities pledged under securities lending arrangements	The contractual maturities of the Company’s fixed maturities are shown in the following table. Expected maturities, which are management’s best estimates, will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. September 30, 2015 December 31, 2014 Maturity Estimated Fair Value Amortized Cost Estimated Amortized Cost Due in one year or less $ 329,589 $ 331,322 $ 235,930 $ 233,794 Due after one year through five years 4,510,824 4,518,625 4,074,562 4,077,408 Due after five years through 10 years 2,583,000 2,585,634 2,475,726 2,461,356 Due after 10 years 429,456 429,734 279,542 273,372 7,852,869 7,865,315 7,065,760 7,045,930 Mortgage backed securities 809,876 799,719 943,343 928,342 Commercial mortgage backed securities 810,973 803,509 1,114,528 1,103,756 Asset backed securities 1,372,549 1,368,367 1,677,941 1,675,605 Total (1) $ 10,846,267 $ 10,836,910 $ 10,801,572 $ 10,753,633 _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.”
Securities lending transactions accounted for as secured borrowings, by significant investment category	The Company’s securities lending transactions were accounted for as secured borrowings with significant investment categories as follows: September 30, 2015 Remaining Contractual Maturity of the Agreements Securities Lending Transactions Overnight and Continuous Less than 30 Days 30-90 Days 90 Days or More Total U.S. government and government agencies $ 225,898 $ — $ 22,784 $ 3,569 $ 252,251 Corporate bonds 35,266 — — — 35,266 Equity securities 5,321 — — — 5,321 Total $ 266,485 $ — $ 22,784 $ 3,569 $ 292,838 Gross amount of recognized liabilities for securities lending in offsetting disclosure in Note 8 $ — Amounts related to securities lending not included in offsetting disclosure in Note 8 $ 292,838
Summary of other investments, including available for sale and fair value option components	The following table summarizes the Company’s other investments, including available for sale and fair value option components: September 30, December 31, Available for sale: Asian and emerging markets $ 210,680 $ 236,586 Investment grade fixed income 31,429 59,638 Credit related funds 13,722 — Other 25,183 — Total available for sale 281,014 296,224 Fair value option: Term loan investments (par value: $1,188,216 and $1,094,337) 1,152,693 1,073,649 Mezzanine debt funds 112,782 121,341 Credit related funds 194,957 114,436 Investment grade fixed income 58,204 69,108 Asian and emerging markets 59,667 25,800 Other (1) 124,591 137,094 Total fair value option 1,702,894 1,541,428 Total $ 1,983,908 $ 1,837,652 _________________________________________________ (1) Includes fund investments with strategies in mortgage servicing rights, transportation and infrastructure assets and other.
Summary of assets and liabilities accounted for using the fair value option	The following table summarizes the Company’s assets and liabilities which are accounted for using the fair value option: September 30, December 31, Fixed maturities $ 926,589 $ 632,024 Other investments 1,702,894 1,541,428 Short-term investments 153,604 251,601 Equity securities 78 — Investments accounted for using the fair value option $ 2,783,165 $ 2,425,053
Components of net investment income	The components of net investment income were derived from the following sources: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Fixed maturities $ 70,626 $ 66,052 $ 210,497 $ 194,370 Term loan investments 16,922 14,066 49,699 26,643 Equity securities (dividends) 3,486 2,779 8,743 8,971 Short-term investments 127 905 548 1,417 Other (1) 10,277 7,913 33,513 21,732 Gross investment income 101,438 91,715 303,000 253,133 Investment expenses (15,205 ) (11,610 ) (50,810 ) (33,044 ) Net investment income $ 86,233 $ 80,105 $ 252,190 $ 220,089 _________________________________________________ (1) Includes income distributions from investment funds and other items.
Summary of net realized gains (losses), excluding other-than-temporary impairment provisions	Net realized gains (losses) were as follows, excluding other-than-temporary impairment provisions: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Available for sale securities: Gross gains on investment sales $ 51,933 $ 62,727 $ 231,757 $ 185,541 Gross losses on investment sales (53,953 ) (35,012 ) (168,087 ) (108,053 ) Change in fair value of assets and liabilities accounted for using the fair value option: Fixed maturities (41,236 ) (9,023 ) (49,729 ) 318 Other investments (75,251 ) (1,085 ) (68,179 ) 27,676 Equity securities 71 — — — Short-term investments (9 ) 638 1,462 638 Derivative instruments (1) 35,889 7,449 31,069 7,083 Other (2) (7,142 ) (7,179 ) (20,368 ) (20,847 ) Net realized gains (losses) $ (89,698 ) $ 18,515 $ (42,075 ) $ 92,356 _________________________________________________ (1) See Note 8 for information on the Company’s derivative instruments. (2) Includes the re-measurement of contingent consideration liability amounts.
Summary of OTTI recognized in earnings by asset class	The following table details the net impairment losses recognized in earnings by asset class: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Fixed maturities: Mortgage backed securities $ (85 ) $ (2 ) $ (1,483 ) $ (2 ) Corporate bonds (4,282 ) (147 ) (6,268 ) (811 ) Commercial mortgage backed securities — (7 ) — (7 ) Asset backed securities — (29 ) — (40 ) Total (4,367 ) (185 ) (7,751 ) (860 ) Short-term investments — — (2,341 ) — Equity securities (1,501 ) (95 ) (1,754 ) (373 ) Other investments — (8,313 ) (934 ) (25,080 ) Net impairment losses recognized in earnings $ (5,868 ) $ (8,593 ) $ (12,780 ) $ (26,313 )
Rollforward of the amount related to credit losses recognized in earnings for which a portion was recognized in AOCI	The following table provides a roll forward of the amount related to credit losses recognized in earnings for which a portion of an OTTI was recognized in accumulated other comprehensive income: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Balance at start of period $ 20,906 $ 21,441 $ 20,196 $ 60,062 Credit loss impairments recognized on securities not previously impaired 4,024 — 8,794 — Credit loss impairments recognized on securities previously impaired 41 151 175 162 Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security — — — — Reductions for securities sold during the period — (217 ) (4,194 ) (38,849 ) Balance at end of period $ 24,971 $ 21,375 $ 24,971 $ 21,375
Summary of restricted assets	The following table details the value of the Company’s restricted assets: September 30, December 31, Assets used for collateral or guarantees: Affiliated transactions $ 3,737,514 $ 4,138,527 Third party agreements 1,071,260 970,120 Deposits with U.S. regulatory authorities 405,817 337,981 Deposits with non-U.S. regulatory authorities 40,365 — Trust funds 100,789 72,461 Total restricted assets $ 5,355,745 $ 5,519,089

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair value hierarchy	The following table presents the Company’s financial assets and liabilities measured at fair value by level at September 30, 2015 : Estimated Fair Value Measurements Using: Estimated Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets measured at fair value: Available for sale securities: Fixed maturities (1): Corporate bonds $ 2,796,038 $ — $ 2,796,038 $ — Mortgage backed securities 809,876 — 809,876 — Municipal bonds 1,830,987 — 1,830,987 — Commercial mortgage backed securities 810,973 — 810,973 — U.S. government and government agencies 2,338,724 2,292,409 46,315 — Non-U.S. government securities 887,120 — 887,120 — Asset backed securities 1,372,549 — 1,315,049 57,500 Total 10,846,267 2,292,409 8,496,358 57,500 Equity securities 606,259 605,677 582 — Short-term investments 708,428 703,316 5,112 — Other investments 60,526 60,526 — — Other investments measured at net asset value (2) 220,488 Total other investments 281,014 60,526 — — Derivative instruments (4) 16,865 — 16,865 — Fair value option: Corporate bonds 767,567 — 767,567 — Non-U.S. government bonds 76,973 — 76,973 — Mortgage backed securities 59,435 — 59,435 — Asset backed securities 22,499 — 22,499 — U.S. government and government agencies 115 115 — — Short-term investments 153,604 153,604 — — Equity securities 78 78 — — Other investments 1,221,194 68,501 1,152,693 — Other investments measured at net asset value (2) 481,700 Total 2,783,165 222,298 2,079,167 — Total assets measured at fair value $ 15,241,998 $ 3,884,226 $ 10,598,084 $ 57,500 Liabilities measured at fair value: Contingent consideration liabilities $ (80,852 ) $ — $ — $ (80,852 ) Securities sold but not yet purchased (3) (25,384 ) — (25,384 ) — Derivative instruments (4) (38,027 ) — (38,027 ) — Total liabilities measured at fair value $ (144,263 ) $ — $ (63,411 ) $ (80,852 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See Note 6 , “Investment Information—Securities Lending Agreements.” (2) In accordance with applicable accounting guidance, 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 sheets. (3) Represents the Company’s obligations to deliver securities that it did not own at the time of sale. Such amounts are included in “other liabilities” on the Company’s consolidated balance sheets. (4) See Note 8 , “Derivative Instruments.” The following table presents the Company’s financial assets and liabilities measured at fair value by level at December 31, 2014 : Estimated Fair Value Measurements Using: Estimated Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets measured at fair value: Available for sale securities: Fixed maturities (1): Corporate bonds $ 3,108,513 $ — $ 3,108,513 $ — Mortgage backed securities 943,343 — 943,343 — Municipal bonds 1,494,122 — 1,494,122 — Commercial mortgage backed securities 1,114,528 — 1,114,528 — U.S. government and government agencies 1,447,972 1,447,972 — — Non-U.S. government securities 1,015,153 — 1,015,153 — Asset backed securities 1,677,941 — 1,620,441 57,500 Total 10,801,572 1,447,972 9,296,100 57,500 Equity securities 658,182 658,182 — — Short-term investments 797,226 759,621 37,605 — Other investments 97,372 — 97,372 — Other investments measured at net asset value (2) 198,852 Total other investments 296,224 — 97,372 — Derivative instruments (3) 15,876 — 15,876 — Fair value option: Corporate bonds 497,101 — 497,101 — Non-U.S. government bonds 88,411 — 88,411 — Mortgage backed securities 22,190 — 22,190 — Asset backed securities 24,322 — 24,322 — Short-term investments 251,601 250,580 1,021 — Other investments 1,140,266 — 1,140,266 — Other investments measured at net asset value (2) 401,162 Total 2,425,053 250,580 1,773,311 — Total assets measured at fair value $ 14,994,133 $ 3,116,355 $ 11,220,264 $ 57,500 Liabilities measured at fair value: Contingent consideration liabilities $ (61,845 ) $ — $ — $ (61,845 ) Derivative instruments (3) (5,397 ) — (5,397 ) — Total liabilities measured at fair value $ (67,242 ) $ — $ (5,397 ) $ (61,845 ) _________________________________________________ (1) In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See Note 6 , “Investment Information—Securities Lending Agreements.” (2) In accordance with applicable accounting guidance, 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 sheets. (3) See Note 8 , “Derivative Instruments.”
Rollforward of Level 3 investments	The following table presents a reconciliation of the beginning and ending balances for all financial assets and liabilities measured at fair value on a recurring basis using Level 3 inputs: Assets Liabilities s Available For Sale Fair Value Option Asset Backed Securities Corporate Bonds Other Investments Other Investments Total Contingent Consideration Liabilities Three Months Ended September 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (71,256 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (9,596 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — — Sales — — — — — — Settlements — — — — — — Transfers in and/or out of Level 3 — — — — — — Balance at end of period $ 57,500 $ — $ — $ — $ 57,500 $ (80,852 ) Three Months Ended September 30, 2014 Balance at beginning of period $ — $ — $ — $ — $ — $ (53,099 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (5,562 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — — Sales — — — — — — Settlements — — — — — — Transfers in and/or out of Level 3 — — — — — — Balance at end of period $ — $ — $ — $ — $ — $ (58,661 ) Nine Months Ended September 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (61,845 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (17,939 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — (1,068 ) Sales — — — — — — Settlements — — — — — — Transfers in and/or out of Level 3 — — — — — — Balance at end of period $ 57,500 $ — $ — $ — $ 57,500 $ (80,852 ) Nine Months Ended September 30, 2014 Balance at beginning of period $ — $ 2,045 $ 170,420 $ 377,525 $ 549,990 $ — Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (16,899 ) Included in other comprehensive income — — — — — — Purchases, issuances, sales and settlements Purchases — — — — — — Issuances — — — — — (41,762 ) Sales — (2,045 ) — — (2,045 ) — Settlements — — — — — — Transfers in and/or out of Level 3 (2) — — (170,420 ) (377,525 ) (547,945 ) — Balance at end of period $ — $ — $ — $ — $ — $ (58,661 ) _________________________________________________ (1) Gains or losses on fixed maturities available for sale were included in net realized gains (losses) while gains or losses on other investments were included in net realized gains (losses) or net investment income. Gains or losses on contingent consideration liabilities were included in net realized gains (losses). (2) In accordance with applicable accounting guidance, 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 transfers out of Level 3 presented in this table are intended to permit reconciliation to information previously presented.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair value and notional amount of derivatives	The following table summarizes information on the fair values and notional values of the Company’s derivative instruments. Estimated Fair Value Asset Liability Derivatives Net Notional Value (1) September 30, 2015 Futures contracts (2) $ 189 $ (3,528 ) $ (3,339 ) $ 1,702,327 Foreign currency forward contracts (2) 10,678 (7,235 ) 3,443 1,018,620 TBAs (3) 307,356 (290,865 ) 16,491 568,463 Other (2) 5,998 (27,264 ) (21,266 ) 1,446,622 Total $ 324,221 $ (328,892 ) $ (4,671 ) December 31, 2014 Futures contracts (2) $ 2,156 $ (1,907 ) $ 249 $ 2,549,027 Foreign currency forward contracts (2) 10,511 (1,145 ) 9,366 397,106 TBAs (3) 10,592 — 10,592 10,056 Other (2) 3,209 (2,345 ) 864 735,684 Total $ 26,468 $ (5,397 ) $ 21,071 _________________________________________________ (1) Represents the absolute notional value of all outstanding contracts, consisting of long and short positions. (2) The fair value of asset derivatives are included in ‘other assets’ and the fair value of liability derivatives are included in ‘other liabilities.’ (3) The fair value of TBAs are included in ‘fixed maturities available for sale, at fair value.’
Summary of net realized gains (losses) recorded in the consolidated statements of income	All realized and unrealized contract gains and losses on the Company’s derivative instruments are reflected in net realized gains (losses) in the consolidated statements of income, as summarized in the following table: Three Months Ended Nine Months Ended Derivatives not designated as September 30, September 30, hedging instruments: 2015 2014 2015 2014 Net realized gains (losses): Futures contracts $ 28,562 $ (354 ) $ 16,442 $ 4,969 Foreign currency forward contracts 5,395 6,558 13,490 2,490 TBAs 1,064 660 1,368 353 Other 868 585 (231 ) (729 ) Total $ 35,889 $ 7,449 $ 31,069 $ 7,083

Other Comprehensive Income (L30

Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2015
Comprehensive Income Note Disclosure [Abstract]
Details about amounts reclassified from AOCI	The following tables present details about amounts reclassified from accumulated other comprehensive income and the tax effects allocated to each component of other comprehensive income (loss): Amounts Reclassified from AOCI Consolidated Statement of Income Three Months Ended Nine Months Ended Details About Line Item That Includes September 30, September 30, AOCI Components Reclassification 2015 2014 2015 2014 Unrealized appreciation on available-for-sale investments Net realized gains (losses) $ (2,019 ) $ 27,715 $ 63,671 $ 77,488 Other-than-temporary impairment losses (8,901 ) (8,593 ) (17,274 ) (26,313 ) Total before tax (10,920 ) 19,122 46,397 51,175 Income tax (expense) benefit (1,358 ) (1,639 ) (6,529 ) (4,158 ) Net of tax $ (12,278 ) $ 17,483 $ 39,868 $ 47,017
Schedule of comprehensive income (loss)	Before Tax Amount Tax Expense (Benefit) Net of Tax Amount Three Months Ended September 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (44,687 ) $ 9,204 $ (53,891 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (3,033 ) — (3,033 ) Less reclassification of net realized gains (losses) included in net income (10,920 ) 1,358 (12,278 ) Foreign currency translation adjustments (12,638 ) (556 ) (12,082 ) Other comprehensive income (loss) $ (49,438 ) $ 7,290 $ (56,728 ) Three Months Ended September 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (90,276 ) $ 343 $ (90,619 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 19,122 1,639 17,483 Foreign currency translation adjustments (23,595 ) — (23,595 ) Other comprehensive income (loss) $ (132,993 ) $ (1,296 ) $ (131,697 ) Nine Months Ended September 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (46,929 ) $ 4,593 $ (51,522 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (4,494 ) — (4,494 ) Less reclassification of net realized gains (losses) included in net income 46,397 6,529 39,868 Foreign currency translation adjustments (24,567 ) (1,308 ) (23,259 ) Other comprehensive income (loss) $ (122,387 ) $ (3,244 ) $ (119,143 ) Nine Months Ended September 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ 100,274 $ 11,112 $ 89,162 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 51,175 4,158 47,017 Foreign currency translation adjustments (14,923 ) — (14,923 ) Other comprehensive income (loss) $ 34,176 $ 6,954 $ 27,222

Guarantor Financial Informati31

Guarantor Financial Information (Tables)	9 Months Ended
	Sep. 30, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed consolidating balance sheet	September 30, 2015 Condensed Consolidating Balance Sheet ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Assets Total investments $ 34 $ 55,053 $ 15,775,050 $ (14,700 ) $ 15,815,437 Cash 10,381 9,256 630,142 — 649,779 Investments in subsidiaries 6,579,718 1,715,121 — (8,294,839 ) — Due from subsidiaries and affiliates — 48,548 442,508 (491,056 ) — Premiums receivable — — 1,521,960 (447,076 ) 1,074,884 Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses — — 5,739,246 (3,906,860 ) 1,832,386 Contractholder receivables — — 1,436,154 — 1,436,154 Prepaid reinsurance premiums — — 1,602,870 (1,160,524 ) 442,346 Deferred acquisition costs, net — — 448,893 — 448,893 Other assets 3,534 43,860 2,644,143 (620,824 ) 2,070,713 Total assets $ 6,593,667 $ 1,871,838 $ 30,240,966 $ (14,935,879 ) $ 23,770,592 Liabilities Reserve for losses and loss adjustment expenses $ — $ — $ 12,969,850 $ (3,884,995 ) $ 9,084,855 Unearned premiums — — 3,628,215 (1,160,524 ) 2,467,691 Reinsurance balances payable — — 669,285 (433,723 ) 235,562 Contractholder payables — — 1,436,154 — 1,436,154 Collateral held for insured obligations — — 242,928 — 242,928 Deposit accounting liabilities — — 482,756 (211,880 ) 270,876 Senior notes 296,854 494,410 — — 791,264 Revolving credit agreement borrowings 100,000 — 239,077 — 339,077 Due to subsidiaries and affiliates 14,080 35,000 441,976 (491,056 ) — Other liabilities 19,918 49,904 2,134,460 (444,163 ) 1,760,119 Total liabilities 430,852 579,314 22,244,701 (6,626,341 ) 16,628,526 Redeemable noncontrolling interests — — 219,789 (14,700 ) 205,089 Shareholders’ Equity Total shareholders’ equity available to Arch 6,162,815 1,292,524 7,002,314 (8,294,838 ) 6,162,815 Non-redeemable noncontrolling interests — — 774,162 — 774,162 Total shareholders’ equity 6,162,815 1,292,524 7,776,476 (8,294,838 ) 6,936,977 Total liabilities, noncontrolling interests and shareholders’ equity $ 6,593,667 $ 1,871,838 $ 30,240,966 $ (14,935,879 ) $ 23,770,592 December 31, 2014 Condensed Consolidating Balance Sheet ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Assets Total investments $ 107 $ 62,867 $ 15,257,796 $ — $ 15,320,770 Cash 3,218 2,787 479,697 — 485,702 Investments in subsidiaries 6,536,644 1,685,185 — (8,221,829 ) — Due from subsidiaries and affiliates 48 7,517 370,429 (377,994 ) — Premiums receivable — — 1,331,511 (382,816 ) 948,695 Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses — — 5,584,973 (3,772,128 ) 1,812,845 Contractholder receivables — — 1,309,192 — 1,309,192 Prepaid reinsurance premiums — — 1,373,008 (995,930 ) 377,078 Deferred acquisition costs, net — — 414,525 — 414,525 Other assets 4,386 43,921 1,705,546 (416,579 ) 1,337,274 Total assets $ 6,544,403 $ 1,802,277 $ 27,826,677 $ (14,167,276 ) $ 22,006,081 Liabilities Reserve for losses and loss adjustment expenses $ — $ — $ 12,784,030 $ (3,747,582 ) $ 9,036,448 Unearned premiums — — 3,227,508 (995,930 ) 2,231,578 Reinsurance balances payable — — 589,289 (369,977 ) 219,312 Contractholder payables — — 1,309,192 — 1,309,192 Collateral held for insured obligations — — 184,219 — 184,219 Deposit accounting liabilities — — 587,050 (259,666 ) 327,384 Senior notes 296,796 494,345 — — 791,141 Revolving credit agreement borrowings 100,000 — — — 100,000 Due to subsidiaries and affiliates 417 7,505 370,072 (377,994 ) — Other liabilities 17,137 49,403 815,919 (194,298 ) 688,161 Total liabilities 414,350 551,253 19,867,279 (5,945,447 ) 14,887,435 Redeemable noncontrolling interests — — 219,512 — 219,512 Shareholders’ Equity Total shareholders’ equity available to Arch 6,130,053 1,251,024 6,970,805 (8,221,829 ) 6,130,053 Non-redeemable noncontrolling interests — — 769,081 — 769,081 Total shareholders’ equity 6,130,053 1,251,024 7,739,886 (8,221,829 ) 6,899,134 Total liabilities, noncontrolling interests and shareholders’ equity $ 6,544,403 $ 1,802,277 $ 27,826,677 $ (14,167,276 ) $ 22,006,081
Condensed consolidating statement of income and comprehensive income	Three Months Ended September 30, 2015 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 936,683 $ — $ 936,683 Net investment income — 764 92,773 (7,304 ) 86,233 Net realized gains (losses) — — (89,698 ) — (89,698 ) Net impairment losses recognized in earnings — — (5,868 ) — (5,868 ) Other underwriting income — — 7,623 — 7,623 Equity in net income (loss) of investment funds accounted for using the equity method — — (2,118 ) — (2,118 ) Other income (loss) — — (265 ) — (265 ) Total revenues — 764 939,130 (7,304 ) 932,590 Expenses Losses and loss adjustment expenses — — 531,741 — 531,741 Acquisition expenses — — 171,566 — 171,566 Other operating expenses 10,536 720 145,703 — 156,959 Interest expense 5,863 6,689 7,734 (6,986 ) 13,300 Net foreign exchange (gains) losses — — (11,762 ) (2,918 ) (14,680 ) Total expenses 16,399 7,409 844,982 (9,904 ) 858,886 Income (loss) before income taxes (16,399 ) (6,645 ) 94,148 2,600 73,704 Income tax (expense) benefit — 2,324 (12,028 ) — (9,704 ) Income (loss) before equity in net income of subsidiaries (16,399 ) (4,321 ) 82,120 2,600 64,000 Equity in net income of subsidiaries 96,432 13,620 — (110,052 ) — Net income 80,033 9,299 82,120 (107,452 ) 64,000 Amounts attributable to noncontrolling interests — — 15,712 321 16,033 Net income available to Arch 80,033 9,299 97,832 (107,131 ) 80,033 Preferred dividends (5,484 ) — — — (5,484 ) Net income available to Arch common shareholders $ 74,549 $ 9,299 $ 97,832 $ (107,131 ) $ 74,549 Comprehensive income (loss) available to Arch $ 23,401 $ 15,705 $ 44,127 $ (59,832 ) $ 23,401 Three Months Ended September 30, 2014 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 903,651 $ — $ 903,651 Net investment income — — 79,936 169 80,105 Net realized gains (losses) — — 18,515 — 18,515 Net impairment losses recognized in earnings — — (8,593 ) — (8,593 ) Other underwriting income — — 1,702 — 1,702 Equity in net income (loss) of investment funds accounted for using the equity method — — 4,966 — 4,966 Other income (loss) — — (7,815 ) — (7,815 ) Total revenues — — 992,362 169 992,531 Expenses Losses and loss adjustment expenses — — 501,673 — 501,673 Acquisition expenses — — 163,547 — 163,547 Other operating expenses 10,056 810 138,614 — 149,480 Interest expense 5,858 6,433 (8,308 ) 169 4,152 Net foreign exchange (gains) losses — — (35,244 ) (20,787 ) (56,031 ) Total expenses 15,914 7,243 760,282 (20,618 ) 762,821 Income (loss) before income taxes (15,914 ) (7,243 ) 232,080 20,787 229,710 Income tax (expense) benefit — 2,097 (8,543 ) — (6,446 ) Income (loss) before equity in net income of subsidiaries (15,914 ) (5,146 ) 223,537 20,787 223,264 Equity in net income of subsidiaries 244,589 10,459 — (255,048 ) — Net income 228,675 5,313 223,537 (234,261 ) 223,264 Amounts attributable to noncontrolling interests — — 5,411 — 5,411 Net income available to Arch 228,675 5,313 228,948 (234,261 ) 228,675 Preferred dividends (5,484 ) — — — (5,484 ) Net income available to Arch common shareholders $ 223,191 $ 5,313 $ 228,948 $ (234,261 ) $ 223,191 Comprehensive income (loss) available to Arch $ 96,978 $ (10,614 ) $ 104,501 $ (93,887 ) $ 96,978 Nine Months Ended September 30, 2015 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 2,790,385 $ — $ 2,790,385 Net investment income — 1,569 265,937 (15,316 ) 252,190 Net realized gains (losses) — 1 (42,076 ) — (42,075 ) Net impairment losses recognized in earnings — — (12,780 ) — (12,780 ) Other underwriting income — — 26,876 — 26,876 Equity in net income (loss) of investment funds accounted for using the equity method — — 19,938 — 19,938 Other income (loss) — — 52 — 52 Total revenues — 1,570 3,048,332 (15,316 ) 3,034,586 Expenses Losses and loss adjustment expenses — — 1,544,883 — 1,544,883 Acquisition expenses — — 510,067 — 510,067 Other operating expenses 36,068 2,991 444,390 — 483,449 Interest expense 17,581 19,824 7,476 (14,834 ) 30,047 Net foreign exchange (gains) losses — — (44,450 ) (17,148 ) (61,598 ) Total expenses 53,649 22,815 2,462,366 (31,982 ) 2,506,848 Income (loss) before income taxes (53,649 ) (21,245 ) 585,966 16,666 527,738 Income tax (expense) benefit — 7,434 (36,596 ) — (29,162 ) Income (loss) before equity in net income of subsidiaries (53,649 ) (13,811 ) 549,370 16,666 498,576 Equity in net income of subsidiaries 532,808 42,192 — (575,000 ) — Net income 479,159 28,381 549,370 (558,334 ) 498,576 Amounts attributable to noncontrolling interests — — (19,902 ) 485 (19,417 ) Net income available to Arch 479,159 28,381 529,468 (557,849 ) 479,159 Preferred dividends (16,453 ) — — — (16,453 ) Net income available to Arch common shareholders $ 462,706 $ 28,381 $ 529,468 $ (557,849 ) $ 462,706 Comprehensive income (loss) available to Arch $ 360,112 $ 13,950 $ 427,569 $ (441,519 ) $ 360,112 Nine Months Ended September 30, 2014 Condensed Consolidating Statement of Income and Comprehensive Income ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Revenues Net premiums earned $ — $ — $ 2,670,583 $ — $ 2,670,583 Net investment income — — 237,317 (17,228 ) 220,089 Net realized gains (losses) — — 92,356 — 92,356 Net impairment losses recognized in earnings — — (26,313 ) — (26,313 ) Other underwriting income — — 5,317 — 5,317 Equity in net income (loss) of investment funds accounted for using the equity method — — 17,459 — 17,459 Other income (loss) — — (5,069 ) — (5,069 ) Total revenues — — 2,991,650 (17,228 ) 2,974,422 Expenses Losses and loss adjustment expenses — — 1,423,431 — 1,423,431 Acquisition expenses — — 482,047 — 482,047 Other operating expenses 35,613 2,281 413,735 — 451,629 Interest expense 17,565 19,395 13,158 (17,228 ) 32,890 Net foreign exchange (gains) losses — — (28,449 ) (18,725 ) (47,174 ) Total expenses 53,178 21,676 2,303,922 (35,953 ) 2,342,823 Income (loss) before income taxes (53,178 ) (21,676 ) 687,728 18,725 631,599 Income tax (expense) benefit — 8,179 (25,652 ) — (17,473 ) Income (loss) before equity in net income of subsidiaries (53,178 ) (13,497 ) 662,076 18,725 614,126 Equity in net income of subsidiaries 672,369 41,945 — (714,314 ) — Net income 619,191 28,448 662,076 (695,589 ) 614,126 Amounts attributable to noncontrolling interests — — 5,065 — 5,065 Net income available to Arch 619,191 28,448 667,141 (695,589 ) 619,191 Preferred dividends (16,453 ) — — — (16,453 ) Net income available to Arch common shareholders $ 602,738 $ 28,448 $ 667,141 $ (695,589 ) $ 602,738 Comprehensive income (loss) available to Arch $ 646,413 $ 29,792 $ 691,968 $ (721,760 ) $ 646,413
Condensed consolidating statement of cash flows	Nine Months Ended September 30, 2015 Condensed Consolidating Statement of Cash Flows ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Operating Activities Net Cash Provided By (Used For) Operating Activities $ 382,329 $ 10,622 $ 859,525 $ (444,897 ) $ 807,579 Investing Activities Purchases of fixed maturity investments — (3,505 ) (22,378,599 ) — (22,382,104 ) Purchases of equity securities (8,070 ) — (477,456 ) — (485,526 ) Purchases of other investments — — (1,320,250 ) — (1,320,250 ) Proceeds from the sales of fixed maturity investments — 23,507 21,388,047 — 21,411,554 Proceeds from the sales of equity securities — — 509,008 — 509,008 Proceeds from the sales, redemptions and maturities of other investments — — 858,368 — 858,368 Proceeds from redemptions and maturities of fixed maturity investments — — 630,397 — 630,397 Net settlements of derivative instruments — — 81,114 — 81,114 Proceeds from investment in joint venture — — 40,000 — 40,000 Net (purchases) sales of short-term investments 73 (12,183 ) 193,851 — 181,741 Change in cash collateral related to securities lending — — 28,685 — 28,685 Contributions to subsidiaries — — (9,290 ) 9,290 — Intercompany loans issued — (39,500 ) (41,523 ) 81,023 — Purchase of business, net of cash acquired — — 818 — 818 Purchases of fixed assets (53 ) — (10,848 ) — (10,901 ) Change in other assets — — (43,654 ) — (43,654 ) Net Cash Provided By (Used For) Investing Activities (8,050 ) (31,681 ) (551,332 ) 90,313 (500,750 ) Financing Activities Purchases of common shares under share repurchase program (365,383 ) — — — (365,383 ) Proceeds from common shares issued, net 697 — 9,290 (9,290 ) 697 Proceeds from intercompany borrowings 14,023 27,500 39,500 (81,023 ) — Proceeds from borrowings — — 239,077 — 239,077 Change in cash collateral related to securities lending — — (28,685 ) — (28,685 ) Dividends paid to redeemable noncontrolling interests — — (14,447 ) 637 (13,810 ) Dividends paid to parent — — (444,260 ) 444,260 — Other — 28 50,435 — 50,463 Preferred dividends paid (16,453 ) — — — (16,453 ) Net Cash Provided By (Used For) Financing Activities (367,116 ) 27,528 (149,090 ) 354,584 (134,094 ) Effects of exchange rates changes on foreign currency cash — — (8,658 ) — (8,658 ) Increase (decrease) in cash 7,163 6,469 150,445 — 164,077 Cash beginning of year 3,218 2,787 479,697 — 485,702 Cash end of period $ 10,381 $ 9,256 $ 630,142 $ — $ 649,779 Nine Months Ended September 30, 2014 Condensed Consolidating Statement of Cash Flows ACGL (Parent Guarantor) Arch-U.S. (Subsidiary Issuer) Other ACGL Subsidiaries Consolidating Adjustments and Eliminations ACGL Consolidated Operating Activities Net Cash Provided By (Used For) Operating Activities $ 265,694 $ 8,407 $ 822,558 $ (297,000 ) $ 799,659 Investing Activities Purchases of fixed maturity investments — (78,509 ) (21,952,353 ) — (22,030,862 ) Purchases of equity securities — — (366,578 ) — (366,578 ) Purchases of other investments — — (1,136,285 ) — (1,136,285 ) Proceeds from the sales of fixed maturity investments — — 20,273,351 — 20,273,351 Proceeds from the sales of equity securities — — 305,034 — 305,034 Proceeds from the sales, redemptions and maturities of other investments — — 566,518 — 566,518 Proceeds from redemptions and maturities of fixed maturity investments — — 636,729 — 636,729 Net settlements of derivative instruments — — 15,495 — 15,495 Net (purchases) sales of short-term investments 2,396 408,760 267,232 — 678,388 Change in cash collateral related to securities lending — — (2,737 ) — (2,737 ) Contributions to subsidiaries — (313,207 ) (100,000 ) 413,207 — Intercompany loans issued — — 10,250 (10,250 ) — Purchase of business, net of cash acquired — — (235,578 ) — (235,578 ) Purchases of fixed assets (220 ) — (14,355 ) — (14,575 ) Change in other assets — — — — — Net Cash Provided By (Used For) Investing Activities 2,176 17,044 (1,733,277 ) 402,957 (1,311,100 ) Financing Activities Purchases of common shares under share repurchase program (251,919 ) — — — (251,919 ) Proceeds from common shares issued, net 3,248 — 413,207 (413,207 ) 3,248 Repayments of intercompany borrowings — (10,250 ) — 10,250 — Change in cash collateral related to securities lending — — 2,737 — 2,737 Third party investment in non-redeemable noncontrolling interests — — 796,903 — 796,903 Third party investment in redeemable noncontrolling interests — — 219,233 — 219,233 Dividends paid to redeemable noncontrolling interests — — (9,632 ) — (9,632 ) Dividends paid to parent — — (297,000 ) 297,000 — Other — — 6,559 — 6,559 Preferred dividends paid (16,453 ) — — — (16,453 ) Net Cash Provided By (Used For) Financing Activities (265,124 ) (10,250 ) 1,132,007 (105,957 ) 750,676 Effects of exchange rates changes on foreign currency cash — — (9,566 ) — (9,566 ) Increase (decrease) in cash 2,746 15,201 211,722 — 229,669 Cash beginning of year 3,223 509 430,325 — 434,057 Cash end of period $ 5,969 $ 15,710 $ 642,047 $ — $ 663,726

General (Details)

General (Details) - Gulf Re - USD ($) $ in Millions	May. 14, 2015	May. 31, 2008
Business Acquisition [Line Items]
Investment in joint venture, at cost		$ 100
Joint venture, ownership percentage		50.00%
Total distributions paid by investee	$ 130.6
Equity capital of investee	50.7
Transfer of securities	$ 25.6
Co-venturer share purchase option period	7 years

Recent Accounting Pronounceme33

Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Accounting Standards Update 2015-03 | Other assets and senior notes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of adoption	$ 8.8	$ 8.9

Variable Interest Entities an34

Variable Interest Entities and Noncontrolling Interests - Variable interest entity (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Variable Interest Entity [Line Items]
Unearned premiums		$ 2,467,691		$ 2,231,578
Reserve for losses and loss adjustment expenses		9,084,855		9,036,448
Revolving credit agreement borrowings		339,077		$ 100,000
Net cash provided by operating activities		807,579	$ 799,659
Net cash provided by financing activities		(134,094)	750,676
Net cash provided by (used in) investing activities		(500,750)	$ (1,311,100)
Variable Interest Entity, Primary Beneficiary | Watford Holdings Ltd
Variable Interest Entity [Line Items]
Initial investment contribution amount	$ 100,000
Ownership percentage	11.00%
Variable Interest Entity, Primary Beneficiary | Watford Re
Variable Interest Entity [Line Items]
Unearned premiums		274,700
Reserve for losses and loss adjustment expenses		223,900
Revolving credit agreement borrowings		239,100
Net cash provided by operating activities		204,300
Net cash provided by financing activities		268,300
Net cash provided by (used in) investing activities		$ (354,500)

Variable Interest Entities an35

Variable Interest Entities and Noncontrolling Interests - Non-redeemable noncontrolling interests (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Noncontrolling Interest [Line Items]
Non-redeemable noncontrolling interests, beginning of period			$ 769,081
Amounts attributable to noncontrolling interests	$ (20,621)	$ (10,320)	5,178	$ (14,883)
Non-redeemable noncontrolling interests, end of period	774,162	782,020	774,162	782,020
Watford Re
Noncontrolling Interest [Line Items]
Non-redeemable noncontrolling interests, beginning of period	794,880	792,340	769,081	0
Sale of shares to noncontrolling interests	0	0	0	796,903
Amounts attributable to noncontrolling interests	(20,621)	(10,320)	5,178	(14,883)
Foreign currency translation adjustments	(97)	0	(97)	0
Non-redeemable noncontrolling interests, end of period	$ 774,162	$ 782,020	$ 774,162	$ 782,020
Common shares | Watford Re
Noncontrolling Interest [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	89.00%		89.00%

Variable Interest Entities an36

Variable Interest Entities and Noncontrolling Interests - Redeemable noncontrolling interests (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests, beginning of period			$ 219,512
Redeemable noncontrolling interests, end of period	$ 205,089		205,089
Watford Re
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests, beginning of period	204,996	$ 219,326	219,512	$ 0
Sale of shares to noncontrolling interests	0	0	0	219,233
Shares acquired by the Company	0	0	(14,700)	0
Accretion of preference share issuance costs	93	93	277	186
Redeemable noncontrolling interests, end of period	$ 205,089	$ 219,419	$ 205,089	$ 219,419
Cumulative redeemable preference shares | Watford Re
Redeemable Noncontrolling Interest [Line Items]
Preference shares, number of shares issued	9,065,200		9,065,200
Par value per share	$ 0.01		$ 0.01
Liquidation preference per share	$ 25		$ 25
Gulf Re | Cumulative redeemable preference shares | Watford Re
Redeemable Noncontrolling Interest [Line Items]
Number of shares in VIE owned by acquired company	600,000

Variable Interest Entities an37

Variable Interest Entities and Noncontrolling Interests - Income or loss attributable to third party investors (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Noncontrolling Interest [Line Items]
Amounts attributable to non-redeemable noncontrolling interests	$ 20,621	$ 10,320	$ (5,178)	$ 14,883
Amounts attributable to redeemable noncontrolling interests	(4,588)	(4,909)	(14,239)	(9,818)
Amounts attributable to noncontrolling interests	$ 16,033	$ 5,411	$ (19,417)	$ 5,065

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015	Sep. 30, 2014
Numerator:
Net income	$ 64,000		$ 223,264		$ 498,576	$ 614,126
Amounts attributable to noncontrolling interests	16,033		5,411		(19,417)	5,065
Net income available to Arch	80,033		228,675		479,159	619,191
Preferred dividends	(5,484)		(5,484)		(16,453)	(16,453)
Net income (loss) available to Arch common shareholders	$ 74,549		$ 223,191		$ 462,706	$ 602,738
Denominator:
Weighted average common shares outstanding — basic	120,567,410		131,945,962		122,151,971	132,151,824
Effect of dilutive common share equivalents:
Nonvested restricted shares	1,322,053		1,156,790		1,260,247	1,134,481
Stock options	3,122,310	[1]	2,773,853	[1]	2,942,541	3,067,867
Weighted average common shares and common share equivalents outstanding — diluted	125,011,773		135,876,605		126,354,759	136,354,172
Earnings per common share:
Basic (per share)	$ 0.62		$ 1.69		$ 3.79	$ 4.56
Diluted (per share)	$ 0.60		$ 1.64		$ 3.66	$ 4.42
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per common share (shares)	390,406		1,355,087		957,838	1,378,249
[1]	Certain stock options were not included in the computation of diluted earnings per share where the exercise price of the stock options exceeded the average market price and would have been anti-dilutive or where, when applying the treasury stock method to in-the-money options, the sum of the proceeds, including unrecognized compensation, exceeded the average market price and would have been anti-dilutive. For the 2015 third quarter and 2014 third quarter, the number of stock options excluded were 390,406 and 1,355,087, respectively. For the nine months ended September 30, 2015 and 2014, the number of stock options excluded were 957,838 and 1,378,249, respectively.

Segment Information - Summary o

Segment Information - Summary of underwriting income or loss by segment (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Gross premiums written		$ 1,189,192	$ 1,159,907	$ 3,730,423	$ 3,726,804
Premiums ceded		(217,220)	(200,368)	(747,876)	(730,347)
Net premiums written		971,972	959,539	2,982,547	2,996,457
Change in unearned premiums		(35,289)	(55,888)	(192,162)	(325,874)
Net premiums earned		936,683	903,651	2,790,385	2,670,583
Other underwriting income		7,623	1,702	26,876	5,317
Losses and loss adjustment expenses		(531,741)	(501,673)	(1,544,883)	(1,423,431)
Acquisition expenses, net		(171,566)	(163,547)	(510,067)	(482,047)
Other operating expenses		(146,220)	(139,046)	(445,947)	(412,788)
Underwriting income (loss)		94,779	101,087	316,364	357,634
Net investment income		86,233	80,105	252,190	220,089
Net realized gains (losses)		(89,698)	18,515	(42,075)	92,356
Net impairment losses recognized in earnings		(5,868)	(8,593)	(12,780)	(26,313)
Equity in net income (loss) of investment funds accounted for using the equity method		(2,118)	4,966	19,938	17,459
Other income (loss)		(265)	(7,815)	52	(5,069)
Other expenses		(10,739)	(10,434)	(37,502)	(38,841)
Interest expense		(13,300)	(4,152)	(30,047)	(32,890)
Net foreign exchange gains (losses)		14,680	56,031	61,598	47,174
Income before income taxes		73,704	229,710	527,738	631,599
Income tax expense		(9,704)	(6,446)	(29,162)	(17,473)
Net income (loss)		64,000	223,264	498,576	614,126
Dividends attributable to redeemable noncontrolling interests		(4,588)	(4,909)	(14,239)	(9,818)
Amounts attributable to non-redeemable noncontrolling interests		20,621	10,320	(5,178)	14,883
Net income available to Arch		80,033	228,675	479,159	619,191
Preferred dividends		(5,484)	(5,484)	(16,453)	(16,453)
Net income (loss) available to Arch common shareholders		$ 74,549	$ 223,191	$ 462,706	$ 602,738
Underwriting Ratios
Loss ratio		56.80%	55.50%	55.40%	53.30%
Acquisition expense ratio		18.30%	18.10%	18.30%	18.10%
Other operating expense ratio		15.60%	15.40%	16.00%	15.50%
Combined ratio		90.70%	89.00%	89.70%	86.90%
Goodwill and intangible assets		$ 103,620	$ 111,528	$ 103,620	$ 111,528	$ 109,539
Total investable assets		16,327,255	15,704,473	16,327,255	15,704,473
Total assets		23,770,592	22,608,227	23,770,592	22,608,227	22,006,081
Total liabilities		16,628,526	15,525,742	16,628,526	15,525,742	$ 14,887,435
Sub-Total
Segment Reporting Information [Line Items]
Gross premiums written	[1]	1,158,451	1,138,392	3,625,382	3,690,462
Premiums ceded		(311,486)	(278,668)	(1,012,608)	(877,816)
Net premiums written		846,965	859,724	2,612,774	2,812,646
Change in unearned premiums		(9,442)	9,157	(101,004)	(191,979)
Net premiums earned		837,523	868,881	2,511,770	2,620,667
Other underwriting income		6,867	1,702	23,306	5,317
Losses and loss adjustment expenses		(465,201)	(478,090)	(1,351,186)	(1,390,298)
Acquisition expenses, net		(142,920)	(153,938)	(430,303)	(467,422)
Other operating expenses		(142,799)	(137,388)	(437,071)	(408,386)
Underwriting income (loss)		93,470	101,167	316,516	359,878
Net investment income		67,251	72,239	204,710	211,690
Net realized gains (losses)		(53,480)	31,411	(14,831)	102,074
Net impairment losses recognized in earnings		(5,868)	(8,593)	(12,780)	(26,313)
Equity in net income (loss) of investment funds accounted for using the equity method		(2,118)	4,966	19,938	17,459
Other income (loss)		(265)	(7,815)	52	(5,069)
Other expenses		(10,739)	(10,434)	(37,502)	(36,512)
Interest expense		(12,014)	(4,152)	(28,761)	(32,890)
Net foreign exchange gains (losses)		16,056	57,611	60,338	48,191
Income before income taxes		92,293	236,400	507,680	638,508
Income tax expense		(9,704)	(6,446)	(29,162)	(17,473)
Net income (loss)		82,589	229,954	478,518	621,035
Dividends attributable to redeemable noncontrolling interests		0	0	0	0
Amounts attributable to non-redeemable noncontrolling interests		0	0	0	0
Net income available to Arch		82,589	229,954	478,518	621,035
Preferred dividends		(5,484)	(5,484)	(16,453)	(16,453)
Net income (loss) available to Arch common shareholders		$ 77,105	$ 224,470	$ 462,065	$ 604,582
Underwriting Ratios
Loss ratio		55.50%	55.00%	53.80%	53.10%
Acquisition expense ratio		17.10%	17.70%	17.10%	17.80%
Other operating expense ratio		17.10%	15.80%	17.40%	15.60%
Combined ratio		89.70%	88.50%	88.30%	86.50%
Goodwill and intangible assets		$ 103,620	$ 111,528	$ 103,620	$ 111,528
Total investable assets		14,733,732	14,580,425	14,733,732	14,580,425
Total assets		21,679,795	21,205,209	21,679,795	21,205,209
Total liabilities		15,627,574	15,221,030	15,627,574	15,221,030
Sub-Total | Insurance
Segment Reporting Information [Line Items]
Gross premiums written	[1]	752,438	726,683	2,263,401	2,309,560
Premiums ceded		(209,443)	(187,689)	(669,336)	(646,082)
Net premiums written		542,995	538,994	1,594,065	1,663,478
Change in unearned premiums		(20,451)	(19,607)	(53,782)	(158,878)
Net premiums earned		522,544	519,387	1,540,283	1,504,600
Other underwriting income		519	499	1,467	1,513
Losses and loss adjustment expenses		(339,859)	(338,319)	(978,681)	(936,615)
Acquisition expenses, net		(77,076)	(81,775)	(228,877)	(235,156)
Other operating expenses		(84,620)	(83,138)	(261,793)	(250,111)
Underwriting income (loss)		$ 21,508	$ 16,654	$ 72,399	$ 84,231
Underwriting Ratios
Loss ratio		65.00%	65.10%	63.50%	62.30%
Acquisition expense ratio		14.80%	15.70%	14.90%	15.60%
Other operating expense ratio		16.20%	16.00%	17.00%	16.60%
Combined ratio		96.00%	96.80%	95.40%	94.50%
Goodwill and intangible assets		$ 29,834	$ 24,024	$ 29,834	$ 24,024
Sub-Total | Reinsurance
Segment Reporting Information [Line Items]
Gross premiums written	[1]	329,327	345,747	1,156,540	1,212,641
Premiums ceded		(92,182)	(83,502)	(318,197)	(215,623)
Net premiums written		237,145	262,245	838,343	997,018
Change in unearned premiums		23,286	34,303	(24,230)	(23,495)
Net premiums earned		260,431	296,548	814,113	973,523
Other underwriting income		2,783	215	6,870	834
Losses and loss adjustment expenses		(115,780)	(123,784)	(339,495)	(413,745)
Acquisition expenses, net		(55,416)	(60,205)	(170,380)	(199,673)
Other operating expenses		(37,131)	(36,337)	(114,182)	(110,198)
Underwriting income (loss)		$ 54,887	$ 76,437	$ 196,926	$ 250,741
Underwriting Ratios
Loss ratio		44.50%	41.70%	41.70%	42.50%
Acquisition expense ratio		21.30%	20.30%	20.90%	20.50%
Other operating expense ratio		14.30%	12.30%	14.00%	11.30%
Combined ratio		80.10%	74.30%	76.60%	74.30%
Goodwill and intangible assets		$ 2,149	$ 3,939	$ 2,149	$ 3,939
Sub-Total | Mortgage
Segment Reporting Information [Line Items]
Gross premiums written	[1]	74,657	66,389	203,770	169,772
Premiums ceded		(7,832)	(7,904)	(23,404)	(17,622)
Net premiums written		66,825	58,485	180,366	152,150
Change in unearned premiums		(12,277)	(5,539)	(22,992)	(9,606)
Net premiums earned		54,548	52,946	157,374	142,544
Other underwriting income		3,565	988	14,969	2,970
Losses and loss adjustment expenses		(9,562)	(15,987)	(33,010)	(39,938)
Acquisition expenses, net		(10,428)	(11,958)	(31,046)	(32,593)
Other operating expenses		(21,048)	(17,913)	(61,096)	(48,077)
Underwriting income (loss)		$ 17,075	$ 8,076	$ 47,191	$ 24,906
Underwriting Ratios
Loss ratio		17.50%	30.20%	21.00%	28.00%
Acquisition expense ratio		19.10%	22.60%	19.70%	22.90%
Other operating expense ratio		38.60%	33.80%	38.80%	33.70%
Combined ratio		75.20%	86.60%	79.50%	84.60%
Goodwill and intangible assets		$ 71,637	$ 83,565	$ 71,637	$ 83,565
Other
Segment Reporting Information [Line Items]
Gross premiums written	[1]	131,165	103,483	387,752	190,239
Premiums ceded		(6,158)	(3,668)	(17,979)	(6,428)
Net premiums written		125,007	99,815	369,773	183,811
Change in unearned premiums		(25,847)	(65,045)	(91,158)	(133,895)
Net premiums earned		99,160	34,770	278,615	49,916
Other underwriting income		756	0	3,570	0
Losses and loss adjustment expenses		(66,540)	(23,583)	(193,697)	(33,133)
Acquisition expenses, net		(28,646)	(9,609)	(79,764)	(14,625)
Other operating expenses		(3,421)	(1,658)	(8,876)	(4,402)
Underwriting income (loss)		1,309	(80)	(152)	(2,244)
Net investment income		18,982	7,866	47,480	8,399
Net realized gains (losses)		(36,218)	(12,896)	(27,244)	(9,718)
Net impairment losses recognized in earnings		0	0	0	0
Equity in net income (loss) of investment funds accounted for using the equity method		0	0	0	0
Other income (loss)		0	0	0	0
Other expenses		0	0	0	(2,329)
Interest expense		(1,286)	0	(1,286)	0
Net foreign exchange gains (losses)		(1,376)	(1,580)	1,260	(1,017)
Income before income taxes		(18,589)	(6,690)	20,058	(6,909)
Income tax expense		0	0	0	0
Net income (loss)		(18,589)	(6,690)	20,058	(6,909)
Dividends attributable to redeemable noncontrolling interests		(4,588)	(4,909)	(14,239)	(9,818)
Amounts attributable to non-redeemable noncontrolling interests		20,621	10,320	(5,178)	14,883
Net income available to Arch		(2,556)	(1,279)	641	(1,844)
Preferred dividends		0	0	0	0
Net income (loss) available to Arch common shareholders		$ (2,556)	$ (1,279)	$ 641	$ (1,844)
Underwriting Ratios
Loss ratio		67.10%	67.80%	69.50%	66.40%
Acquisition expense ratio		28.90%	27.60%	28.60%	29.30%
Other operating expense ratio		3.40%	4.80%	3.20%	8.80%
Combined ratio		99.40%	100.20%	101.30%	104.50%
Goodwill and intangible assets		$ 0	$ 0	$ 0	$ 0
Total investable assets		1,593,523	1,124,048	1,593,523	1,124,048
Total assets		2,090,797	1,403,018	2,090,797	1,403,018
Total liabilities		$ 1,000,952	$ 304,712	$ 1,000,952	$ 304,712
[1]	Certain amounts included in the gross premiums written of each segment are related to intersegment transactions. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total.

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2015segment
Underwriting segments
Segment Reporting Information [Line Items]
Number of underwriting segments	3
Other
Segment Reporting Information [Line Items]
Number of underwriting segments	2

Investment Information - Summar

Investment Information - Summary of available for sale securities (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Available for sale securities:
Estimated Fair Value		$ 12,441,968	$ 12,553,204
Gross Unrealized Gains		223,632	282,262
Gross Unrealized Losses		(150,612)	(111,730)
Cost or Amortized Cost		12,368,948	12,382,672
OTTI Unrealized Losses	[1]	(6,609)	(3,646)
Fixed maturities
Available for sale securities:
Estimated Fair Value		10,846,267	10,801,572
Gross Unrealized Gains	[2]	115,685	140,673
Gross Unrealized Losses	[2]	(106,328)	(92,734)
Cost or Amortized Cost	[2]	10,836,910	10,753,633
OTTI Unrealized Losses	[1],[2]	(6,609)	(3,646)
Fixed maturities | Corporate bonds
Available for sale securities:
Estimated Fair Value		2,796,038	3,108,513
Gross Unrealized Gains	[2]	28,418	37,928
Gross Unrealized Losses	[2]	(54,489)	(38,974)
Cost or Amortized Cost	[2]	2,822,109	3,109,559
OTTI Unrealized Losses	[1],[2]	(3,033)	(317)
Fixed maturities | Mortgage backed securities
Available for sale securities:
Estimated Fair Value		809,876	943,343
Gross Unrealized Gains	[2]	13,155	18,843
Gross Unrealized Losses	[2]	(2,998)	(3,842)
Cost or Amortized Cost	[2]	799,719	928,342
OTTI Unrealized Losses	[1],[2]	(3,554)	(3,307)
Fixed maturities | Municipal bonds
Available for sale securities:
Estimated Fair Value		1,830,987	1,494,122
Gross Unrealized Gains	[2]	27,600	31,227
Gross Unrealized Losses	[2]	(2,771)	(1,044)
Cost or Amortized Cost	[2]	1,806,158	1,463,939
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | Commercial mortgage backed securities
Available for sale securities:
Estimated Fair Value		810,973	1,114,528
Gross Unrealized Gains	[2]	10,058	14,594
Gross Unrealized Losses	[2]	(2,594)	(3,822)
Cost or Amortized Cost	[2]	803,509	1,103,756
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | US government and government agencies
Available for sale securities:
Estimated Fair Value		2,338,724	1,447,972
Gross Unrealized Gains	[2]	14,352	8,345
Gross Unrealized Losses	[2]	(2,138)	(1,760)
Cost or Amortized Cost	[2]	2,326,510	1,441,387
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | Non-US government securities
Available for sale securities:
Estimated Fair Value		887,120	1,015,153
Gross Unrealized Gains	[2]	13,070	21,311
Gross Unrealized Losses	[2]	(36,488)	(37,203)
Cost or Amortized Cost	[2]	910,538	1,031,045
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | Asset backed securities
Available for sale securities:
Estimated Fair Value		1,372,549	1,677,941
Gross Unrealized Gains	[2]	9,032	8,425
Gross Unrealized Losses	[2]	(4,850)	(6,089)
Cost or Amortized Cost	[2]	1,368,367	1,675,605
OTTI Unrealized Losses	[1],[2]	(22)	(22)
Equity securities
Available for sale securities:
Estimated Fair Value		606,259	658,182
Gross Unrealized Gains		68,494	109,012
Gross Unrealized Losses		(37,527)	(13,364)
Cost or Amortized Cost		575,292	562,534
OTTI Unrealized Losses	[1]	0	0
Other investments
Available for sale securities:
Estimated Fair Value		281,014	296,224
Gross Unrealized Gains		39,287	31,839
Gross Unrealized Losses		(3,629)	(362)
Cost or Amortized Cost		245,356	264,747
OTTI Unrealized Losses	[1]	0	0
Short-term investments
Available for sale securities:
Estimated Fair Value		708,428	797,226
Gross Unrealized Gains		166	738
Gross Unrealized Losses		(3,128)	(5,270)
Cost or Amortized Cost		711,390	801,758
OTTI Unrealized Losses	[1]	$ 0	$ 0
[1]	Represents the total other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income (“AOCI”). It does not include the change in fair value subsequent to the impairment measurement date. At September 30, 2015, the net unrealized loss related to securities for which a non-credit OTTI was recognized in AOCI was $2.3 million, compared to a net unrealized gain of $0.9 million at December 31, 2014.
[2]	In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.”

Investment Information - Aging

Investment Information - Aging of available for sale securities in an unrealized loss position (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Available for sale securities:
Estimated Fair Value - Less than 12 Months		$ 3,460,817	$ 4,108,030
Gross Unrealized Losses - Less than 12 Months		(117,745)	(90,017)
Estimated Fair Value - 12 Months or More		397,205	641,407
Gross Unrealized Losses - 12 Months or More		(32,867)	(21,713)
Estimated Fair Value - Total		3,858,022	4,749,437
Gross Unrealized Losses - Total		(150,612)	(111,730)
Fixed maturities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	3,070,185	3,788,119
Gross Unrealized Losses - Less than 12 Months	[1]	(73,461)	(71,021)
Estimated Fair Value - 12 Months or More	[1]	397,205	641,407
Gross Unrealized Losses - 12 Months or More	[1]	(32,867)	(21,713)
Estimated Fair Value - Total	[1]	3,467,390	4,429,526
Gross Unrealized Losses - Total	[1]	(106,328)	(92,734)
Fixed maturities | Corporate bonds
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	1,208,894	1,309,637
Gross Unrealized Losses - Less than 12 Months	[1]	(37,606)	(32,903)
Estimated Fair Value - 12 Months or More	[1]	135,135	148,963
Gross Unrealized Losses - 12 Months or More	[1]	(16,883)	(6,071)
Estimated Fair Value - Total	[1]	1,344,029	1,458,600
Gross Unrealized Losses - Total	[1]	(54,489)	(38,974)
Fixed maturities | Mortgage backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	235,252	293,624
Gross Unrealized Losses - Less than 12 Months	[1]	(1,986)	(1,476)
Estimated Fair Value - 12 Months or More	[1]	52,621	59,107
Gross Unrealized Losses - 12 Months or More	[1]	(1,012)	(2,366)
Estimated Fair Value - Total	[1]	287,873	352,731
Gross Unrealized Losses - Total	[1]	(2,998)	(3,842)
Fixed maturities | Municipal bonds
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	219,610	210,614
Gross Unrealized Losses - Less than 12 Months	[1]	(2,567)	(588)
Estimated Fair Value - 12 Months or More	[1]	9,717	13,643
Gross Unrealized Losses - 12 Months or More	[1]	(204)	(456)
Estimated Fair Value - Total	[1]	229,327	224,257
Gross Unrealized Losses - Total	[1]	(2,771)	(1,044)
Fixed maturities | Commercial mortgage backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	263,779	232,147
Gross Unrealized Losses - Less than 12 Months	[1]	(2,376)	(770)
Estimated Fair Value - 12 Months or More	[1]	19,774	125,894
Gross Unrealized Losses - 12 Months or More	[1]	(218)	(3,052)
Estimated Fair Value - Total	[1]	283,553	358,041
Gross Unrealized Losses - Total	[1]	(2,594)	(3,822)
Fixed maturities | US government and government agencies
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	283,534	618,381
Gross Unrealized Losses - Less than 12 Months	[1]	(2,138)	(1,626)
Estimated Fair Value - 12 Months or More	[1]	0	3,438
Gross Unrealized Losses - 12 Months or More	[1]	0	(134)
Estimated Fair Value - Total	[1]	283,534	621,819
Gross Unrealized Losses - Total	[1]	(2,138)	(1,760)
Fixed maturities | Non-US government securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	391,631	510,766
Gross Unrealized Losses - Less than 12 Months	[1]	(23,526)	(31,172)
Estimated Fair Value - 12 Months or More	[1]	52,976	46,910
Gross Unrealized Losses - 12 Months or More	[1]	(12,962)	(6,031)
Estimated Fair Value - Total	[1]	444,607	557,676
Gross Unrealized Losses - Total	[1]	(36,488)	(37,203)
Fixed maturities | Asset backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	467,485	612,950
Gross Unrealized Losses - Less than 12 Months	[1]	(3,262)	(2,486)
Estimated Fair Value - 12 Months or More	[1]	126,982	243,452
Gross Unrealized Losses - 12 Months or More	[1]	(1,588)	(3,603)
Estimated Fair Value - Total	[1]	594,467	856,402
Gross Unrealized Losses - Total	[1]	(4,850)	(6,089)
Equity securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months		311,608	181,002
Gross Unrealized Losses - Less than 12 Months		(37,527)	(13,364)
Estimated Fair Value - 12 Months or More		0	0
Gross Unrealized Losses - 12 Months or More		0	0
Estimated Fair Value - Total		311,608	181,002
Gross Unrealized Losses - Total		(37,527)	(13,364)
Other investments
Available for sale securities:
Estimated Fair Value - Less than 12 Months		45,151	59,638
Gross Unrealized Losses - Less than 12 Months		(3,629)	(362)
Estimated Fair Value - 12 Months or More		0	0
Gross Unrealized Losses - 12 Months or More		0	0
Estimated Fair Value - Total		45,151	59,638
Gross Unrealized Losses - Total		(3,629)	(362)
Short-term investments
Available for sale securities:
Estimated Fair Value - Less than 12 Months		33,873	79,271
Gross Unrealized Losses - Less than 12 Months		(3,128)	(5,270)
Estimated Fair Value - 12 Months or More		0	0
Gross Unrealized Losses - 12 Months or More		0	0
Estimated Fair Value - Total		33,873	79,271
Gross Unrealized Losses - Total		$ (3,128)	$ (5,270)
[1]	In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.”

Investment Information - Maturi

Investment Information - Maturity profile of available for sale securities) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Estimated Fair Value:
Estimated fair value		$ 10,560,635	$ 10,750,770
Amortized Cost:
Amortized cost		10,550,931	10,701,557
Fixed maturities
Estimated Fair Value:
Due in one year or less		329,589	235,930
Due after one year through five years		4,510,824	4,074,562
Due after five years through 10 years		2,583,000	2,475,726
Due after 10 years		429,456	279,542
Single maturity date		7,852,869	7,065,760
Estimated fair value	[1]	10,846,267	10,801,572
Amortized Cost:
Due in one year or less		331,322	233,794
Due after one year through five years		4,518,625	4,077,408
Due after five years through 10 years		2,585,634	2,461,356
Due after 10 years		429,734	273,372
Single maturity date		7,865,315	7,045,930
Amortized cost	[1]	10,836,910	10,753,633
Fixed maturities | Mortgage backed securities
Estimated Fair Value:
Securities without single maturity date		809,876	943,343
Amortized Cost:
Securities without single maturity date		799,719	928,342
Fixed maturities | Commercial mortgage backed securities
Estimated Fair Value:
Securities without single maturity date		810,973	1,114,528
Amortized Cost:
Securities without single maturity date		803,509	1,103,756
Fixed maturities | Asset backed securities
Estimated Fair Value:
Securities without single maturity date		1,372,549	1,677,941
Amortized Cost:
Securities without single maturity date		$ 1,368,367	$ 1,675,605
[1]	In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.”

Investment Information - Securi

Investment Information - Securities lending agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Disclosure Investment Information [Abstract]
Fair value of cash collateral received on securities lending	$ 15,700
Approximate fair value of sub-prime securities backing the securities lending program	5,400	$ 5,800
Fair value of non-cash collateral received on securities lending	271,000	0
Collateral received under securities lending, at fair value (amortized cost: $282,783 and $40,473)	286,659	44,301
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	292,838	$ 50,529
Gross amount of recognized liabilities for securities lending in offsetting disclosure in Note 8	0
Amounts related to securities lending not included in offsetting disclosure in Note 8	292,838
US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	252,251
Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	35,266
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	5,321
Overnight and continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	266,485
Overnight and continuous | US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	225,898
Overnight and continuous | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	35,266
Overnight and continuous | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	5,321
Less than 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
Less than 30 days | US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
Less than 30 days | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
Less than 30 days | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
30 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	22,784
30 - 90 days | US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	22,784
30 - 90 days | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
30 - 90 days | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
90 days or more
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	3,569
90 days or more | US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	3,569
90 days or more | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
90 days or more | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	$ 0

Investment Information - Other

Investment Information - Other investments (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		$ 1,983,908	$ 1,837,652
Available for sale
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		281,014	296,224
Available for sale | Asian and emerging markets
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		210,680	236,586
Available for sale | Investment grade fixed income
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		31,429	59,638
Available for sale | Credit related funds
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		13,722	0
Available for sale | Other
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		25,183	0
Fair value option
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		1,702,894	1,541,428
Fair value option | Asian and emerging markets
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		59,667	25,800
Fair value option | Investment grade fixed income
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		58,204	69,108
Fair value option | Credit related funds
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		194,957	114,436
Fair value option | Other
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	[1]	124,591	137,094
Fair value option | Term loan investments
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		1,152,693	1,073,649
Other investments par		1,188,216	1,094,337
Fair value option | Mezzanine debt funds
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		$ 112,782	$ 121,341
[1]	Includes fund investments with strategies in mortgage servicing rights, transportation and infrastructure assets and other.

Investment Information - Fair v

Investment Information - Fair value option (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	$ 2,783,165	$ 2,425,053
Fixed Maturities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	926,589	632,024
Other investments
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	1,702,894	1,541,428
Short-term investments
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	153,604	251,601
Equity securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	$ 78	$ 0

Investment Information - Net in

Investment Information - Net investment income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net investment income:
Gross investment income		$ 101,438	$ 91,715	$ 303,000	$ 253,133
Investment expenses		(15,205)	(11,610)	(50,810)	(33,044)
Net investment income		86,233	80,105	252,190	220,089
Fixed Maturities
Net investment income:
Gross investment income		70,626	66,052	210,497	194,370
Term loan investments
Net investment income:
Gross investment income		16,922	14,066	49,699	26,643
Equity securities (dividends)
Net investment income:
Gross investment income		3,486	2,779	8,743	8,971
Short-term investments
Net investment income:
Gross investment income		127	905	548	1,417
Other
Net investment income:
Gross investment income	[1]	$ 10,277	$ 7,913	$ 33,513	$ 21,732
[1]	Includes income distributions from investment funds and other items.

Investment Information - Net re

Investment Information - Net realized gains and losses (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net realized gains and losses:
Available for sale securities, gross gains on investment sales		$ 51,933	$ 62,727	$ 231,757	$ 185,541
Available for sale securities, gross losses on investment sales		(53,953)	(35,012)	(168,087)	(108,053)
Derivative instruments	[1]	35,889	7,449	31,069	7,083
Other	[2]	(7,142)	(7,179)	(20,368)	(20,847)
Net realized gains (losses)		(89,698)	18,515	(42,075)	92,356
Fixed Maturities
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		(41,236)	(9,023)	(49,729)	318
Other investments
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		(75,251)	(1,085)	(68,179)	27,676
Equity securities
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		71	0	0	0
Short-term investments
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		$ (9)	$ 638	$ 1,462	$ 638
[1]	See Note 8 for information on the Company’s derivative instruments.
[2]	Includes the re-measurement of contingent consideration liability amounts.

Investment Information - Othe49

Investment Information - Other than temporary impairments recognized in earnings (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	$ (5,868)	$ (8,593)	$ (12,780)	$ (26,313)
Fixed Maturities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	(4,367)	(185)	(7,751)	(860)
Fixed Maturities | Mortgage backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	(85)	(2)	(1,483)	(2)
Fixed Maturities | Corporate bonds
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	(4,282)	(147)	(6,268)	(811)
Fixed Maturities | Commercial mortgage backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	0	(7)	0	(7)
Fixed Maturities | Asset backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	0	(29)	0	(40)
Short-term investments
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	0	0	(2,341)	0
Equity securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	(1,501)	(95)	(1,754)	(373)
Other investments
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	$ 0	$ (8,313)	$ (934)	$ (25,080)

Investment Information - Othe50

Investment Information - Other than temporary impairments rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Rollforward:
Balance at start of period	$ 20,906	$ 21,441	$ 20,196	$ 60,062
Credit loss impairments recognized on securities not previously impaired	4,024	0	8,794	0
Credit loss impairments recognized on securities previously impaired	41	151	175	162
Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security	0	0	0	0
Reductions for securities sold during the period	0	(217)	(4,194)	(38,849)
Balance at end of period	$ 24,971	$ 21,375	$ 24,971	$ 21,375

Investment Information - Restri

Investment Information - Restricted assets (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Restricted Assets [Line Items]
Restricted assets	$ 5,355,745	$ 5,519,089
Collateral or guarantees - affiliated transactions
Restricted Assets [Line Items]
Restricted assets	3,737,514	4,138,527
Collateral or guarantees - third party agreements
Restricted Assets [Line Items]
Restricted assets	1,071,260	970,120
Deposits with US regulatory authorities
Restricted Assets [Line Items]
Restricted assets	405,817	337,981
Deposits with non-US regulatory authorities
Restricted Assets [Line Items]
Restricted assets	40,365	0
Trust funds
Restricted Assets [Line Items]
Restricted assets	$ 100,789	$ 72,461

Investment Information - Narrat

Investment Information - Narrative (Details) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2015USD ($)lots	Dec. 31, 2014USD ($)lots	Sep. 30, 2014USD ($)
Narrative items:
Investable assets		$ 16,327,255		$ 15,704,473
OTTI unrealized (losses) gains at current fair value		$ (2,300)	$ 900
Continuous unrealized loss, qualitative disclosures:
Number of positions in an unrealized loss position (lots) | lots		2,300	1,900
Total number of positions (lots) | lots		5,540	4,790
Largest single loss		$ 3,600	$ 2,900
OTTI unrealized losses (gains)	[1]	6,609	$ 3,646
Underwriting segments
Narrative items:
Investable assets		14,733,732		14,580,425
Other
Narrative items:
Investable assets		$ 1,593,523		$ 1,124,048
[1]	Represents the total other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income (“AOCI”). It does not include the change in fair value subsequent to the impairment measurement date. At September 30, 2015, the net unrealized loss related to securities for which a non-credit OTTI was recognized in AOCI was $2.3 million, compared to a net unrealized gain of $0.9 million at December 31, 2014.

Fair Value - Fair Value Hierarc

Fair Value - Fair Value Hierarchy (Details) - Recurring - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		$ 3,884,226	$ 3,116,355
Liabilities measured at fair value		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Securities sold but not yet purchased
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	[1]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	2,292,409	1,447,972
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities | Commercial mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	2,292,409	1,447,972
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturities | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		605,677	658,182
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		703,316	759,621
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		60,526	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		60,526	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[1]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		222,298	250,580
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		115
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		153,604	250,580
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		78
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value option | Other investments fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		68,501	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		10,598,084	11,220,264
Liabilities measured at fair value		(63,411)	(5,397)
Significant Other Observable Inputs (Level 2) | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		0	0
Significant Other Observable Inputs (Level 2) | Securities sold but not yet purchased
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		(25,384)
Significant Other Observable Inputs (Level 2) | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	[1]	(38,027)	(5,397)
Significant Other Observable Inputs (Level 2) | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	8,496,358	9,296,100
Significant Other Observable Inputs (Level 2) | Fixed maturities | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	2,796,038	3,108,513
Significant Other Observable Inputs (Level 2) | Fixed maturities | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	809,876	943,343
Significant Other Observable Inputs (Level 2) | Fixed maturities | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	1,830,987	1,494,122
Significant Other Observable Inputs (Level 2) | Fixed maturities | Commercial mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	810,973	1,114,528
Significant Other Observable Inputs (Level 2) | Fixed maturities | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	46,315	0
Significant Other Observable Inputs (Level 2) | Fixed maturities | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	887,120	1,015,153
Significant Other Observable Inputs (Level 2) | Fixed maturities | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	1,315,049	1,620,441
Significant Other Observable Inputs (Level 2) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		582	0
Significant Other Observable Inputs (Level 2) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		5,112	37,605
Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	97,372
Significant Other Observable Inputs (Level 2) | Other investments at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	97,372
Significant Other Observable Inputs (Level 2) | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[1]	16,865	15,876
Significant Other Observable Inputs (Level 2) | Fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		2,079,167	1,773,311
Significant Other Observable Inputs (Level 2) | Fair value option | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		767,567	497,101
Significant Other Observable Inputs (Level 2) | Fair value option | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		59,435	22,190
Significant Other Observable Inputs (Level 2) | Fair value option | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Significant Other Observable Inputs (Level 2) | Fair value option | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		76,973	88,411
Significant Other Observable Inputs (Level 2) | Fair value option | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		22,499	24,322
Significant Other Observable Inputs (Level 2) | Fair value option | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	1,021
Significant Other Observable Inputs (Level 2) | Fair value option | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Significant Other Observable Inputs (Level 2) | Fair value option | Other investments fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		1,152,693	1,140,266
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		57,500	57,500
Liabilities measured at fair value		(80,852)	(61,845)
Significant Unobservable Inputs (Level 3) | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		(80,852)	(61,845)
Significant Unobservable Inputs (Level 3) | Securities sold but not yet purchased
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		0
Significant Unobservable Inputs (Level 3) | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	[1]	0	0
Significant Unobservable Inputs (Level 3) | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	57,500	57,500
Significant Unobservable Inputs (Level 3) | Fixed maturities | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Significant Unobservable Inputs (Level 3) | Fixed maturities | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Significant Unobservable Inputs (Level 3) | Fixed maturities | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Significant Unobservable Inputs (Level 3) | Fixed maturities | Commercial mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Significant Unobservable Inputs (Level 3) | Fixed maturities | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Significant Unobservable Inputs (Level 3) | Fixed maturities | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	0	0
Significant Unobservable Inputs (Level 3) | Fixed maturities | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[2]	57,500	57,500
Significant Unobservable Inputs (Level 3) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Other investments at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[1]	0	0
Significant Unobservable Inputs (Level 3) | Fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Fair value option | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Fair value option | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Fair value option | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Significant Unobservable Inputs (Level 3) | Fair value option | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Fair value option | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Fair value option | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Significant Unobservable Inputs (Level 3) | Fair value option | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Significant Unobservable Inputs (Level 3) | Fair value option | Other investments fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		0	0
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		15,241,998	14,994,133
Liabilities measured at fair value		(144,263)	(67,242)
Estimated Fair Value | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		(80,852)	(61,845)
Estimated Fair Value | Securities sold but not yet purchased
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value		(25,384)
Estimated Fair Value | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	[1]	(38,027)	(5,397)
Estimated Fair Value | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		10,846,267	10,801,572
Estimated Fair Value | Fixed maturities | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		2,796,038	3,108,513
Estimated Fair Value | Fixed maturities | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		809,876	943,343
Estimated Fair Value | Fixed maturities | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		1,830,987	1,494,122
Estimated Fair Value | Fixed maturities | Commercial mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		810,973	1,114,528
Estimated Fair Value | Fixed maturities | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		2,338,724	1,447,972
Estimated Fair Value | Fixed maturities | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		887,120	1,015,153
Estimated Fair Value | Fixed maturities | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		1,372,549	1,677,941
Estimated Fair Value | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		606,259	658,182
Estimated Fair Value | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		708,428	797,226
Estimated Fair Value | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		281,014	296,224
Estimated Fair Value | Other investments at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		60,526	97,372
Estimated Fair Value | Other investments measured at net asset value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[3]	220,488	198,852
Estimated Fair Value | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[1]	16,865	15,876
Estimated Fair Value | Fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		2,783,165	2,425,053
Estimated Fair Value | Fair value option | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		767,567	497,101
Estimated Fair Value | Fair value option | Mortgage backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		59,435	22,190
Estimated Fair Value | Fair value option | US government and government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		115
Estimated Fair Value | Fair value option | Non-US government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		76,973	88,411
Estimated Fair Value | Fair value option | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		22,499	24,322
Estimated Fair Value | Fair value option | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		153,604	251,601
Estimated Fair Value | Fair value option | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		78
Estimated Fair Value | Fair value option | Other investments fair value option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value		1,221,194	1,140,266
Estimated Fair Value | Fair value option | Other investments measured at net asset value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	[3]	$ 481,700	$ 401,162
[1]	See Note 8, “Derivative Instruments.”
[2]	In securities lending transactions, the Company receives collateral in excess of the fair value of the securities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See Note 6, “Investment Information—Securities Lending Agreements.”
[3]	In accordance with applicable accounting guidance, 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 sheets.

Fair Value - Rollforward of Lev

Fair Value - Rollforward of Level 3 assets and liabilities (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		$ 57,500	$ 0	$ 57,500	$ 549,990
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0	0	0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0	0	0
Purchases, issuances, sales and settlements
Purchases		0	0	0	0
Issuances		0	0	0	0
Sales		0	0	0	(2,045)
Settlements		0	0	0	0
Transfers in and/or out of Level 3		0	0	0	(547,945)	[2]
Balance at end of period		57,500	0	57,500	0
Contingent consideration liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		(71,256)	(53,099)	(61,845)	0
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	(9,596)	(5,562)	(17,939)	(16,899)
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0	0	0
Purchases, issuances, sales and settlements
Purchases		0	0	0	0
Issuances		0	0	(1,068)	(41,762)
Sales		0	0	0	0
Settlements		0	0	0	0
Transfers in and/or out of Level 3		0	0	0	0	[2]
Balance at end of period		(80,852)	(58,661)	(80,852)	(58,661)
Available for sale | Asset backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		57,500	0	57,500	0
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0	0	0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0	0	0
Purchases, issuances, sales and settlements
Purchases		0	0	0	0
Issuances		0	0	0	0
Sales		0	0	0	0
Settlements		0	0	0	0
Transfers in and/or out of Level 3		0	0	0	0	[2]
Balance at end of period		57,500	0	57,500	0
Available for sale | Corporate bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		0	0	0	2,045
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0	0	0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0	0	0
Purchases, issuances, sales and settlements
Purchases		0	0	0	0
Issuances		0	0	0	0
Sales		0	0	0	(2,045)
Settlements		0	0	0	0
Transfers in and/or out of Level 3		0	0	0	0	[2]
Balance at end of period		0	0	0	0
Available for sale | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		0	0	0	170,420
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0	0	0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0	0	0
Purchases, issuances, sales and settlements
Purchases		0	0	0	0
Issuances		0	0	0	0
Sales		0	0	0	0
Settlements		0	0	0	0
Transfers in and/or out of Level 3		0	0	0	(170,420)	[2]
Balance at end of period		0	0	0	0
Fair value option | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		0	0	0	377,525
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0	0	0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0	0	0
Purchases, issuances, sales and settlements
Purchases		0	0	0	0
Issuances		0	0	0	0
Sales		0	0	0	0
Settlements		0	0	0	0
Transfers in and/or out of Level 3		0	0	0	(377,525)	[2]
Balance at end of period		$ 0	$ 0	$ 0	$ 0
[1]	Gains or losses on fixed maturities available for sale were included in net realized gains (losses) while gains or losses on other investments were included in net realized gains (losses) or net investment income. Gains or losses on contingent consideration liabilities were included in net realized gains (losses).
[2]	In accordance with applicable accounting guidance, 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 transfers out of Level 3 presented in this table are intended to permit reconciliation to information previously presented.

Fair Value - Narrative (Details

Fair Value - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Total assets and liabilities measured at fair value	$ 15,360,000		$ 15,060,000
Total assets and liabilities measured at fair value priced using non-binding broker quotes	$ 300,700		$ 260,800
Total assets and liabilities measured at fair value priced using non-binding broker quotes (percentage)	2.00%		1.70%
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 791,264		$ 791,141
Reportable Legal Entities | ACGL (Parent Guarantor)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	296,854		296,796
Estimated fair value of senior notes	387,600
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	494,410		$ 494,345
Estimated fair value of senior notes	$ 543,700
US government agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers from Level 1 to Level 2		$ 44,600
Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount		$ 99,700

Derivative Instruments (Details

Derivative Instruments (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Derivative offsetting [Abstract]
Derivative assets subject to master netting agreements		$ 298,400		$ 298,400		$ 25,300
Derivative liabilities subject to master netting agreements		309,600		309,600		5,400
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments	[1]	35,889	$ 7,449	31,069	$ 7,083
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives - fair value		324,221		324,221		26,468
Liability derivatives - fair value		(328,892)		(328,892)		(5,397)
Net derivatives - fair value		(4,671)		(4,671)		21,071
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		35,889	7,449	31,069	7,083
Not Designated as Hedging Instrument [Member] | Futures contracts
Derivative [Line Items]
Net derivatives - fair value	[2]	(3,339)		(3,339)		249
Net derivatives - notional value	[2],[3]	1,702,327		1,702,327		2,549,027
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		28,562	(354)	16,442	4,969
Not Designated as Hedging Instrument [Member] | Futures contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	189		189		2,156
Not Designated as Hedging Instrument [Member] | Futures contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(3,528)		(3,528)		(1,907)
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts
Derivative [Line Items]
Net derivatives - fair value	[2]	3,443		3,443		9,366
Net derivatives - notional value	[2],[3]	1,018,620		1,018,620		397,106
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		5,395	6,558	13,490	2,490
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	10,678		10,678		10,511
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(7,235)		(7,235)		(1,145)
Not Designated as Hedging Instrument [Member] | TBAs
Derivative [Line Items]
Net derivatives - fair value	[4]	16,491		16,491		10,592
Net derivatives - notional value	[3],[4]	568,463		568,463		10,056
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		1,064	660	1,368	353
Not Designated as Hedging Instrument [Member] | TBAs | Fixed maturities available for sale
Derivative [Line Items]
Asset derivatives - fair value	[4]	307,356		307,356		10,592
Liability derivatives - fair value	[4]	(290,865)		(290,865)		0
Not Designated as Hedging Instrument [Member] | Other
Derivative [Line Items]
Net derivatives - fair value	[2]	(21,266)		(21,266)		864
Net derivatives - notional value	[2],[3]	1,446,622		1,446,622		735,684
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		868	$ 585	(231)	$ (729)
Not Designated as Hedging Instrument [Member] | Other | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	5,998		5,998		3,209
Not Designated as Hedging Instrument [Member] | Other | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	$ (27,264)		$ (27,264)		$ (2,345)
[1]	See Note 8 for information on the Company’s derivative instruments.
[2]	The fair value of asset derivatives are included in ‘other assets’ and the fair value of liability derivatives are included in ‘other liabilities.’
[3]	Represents the absolute notional value of all outstanding contracts, consisting of long and short positions.
[4]	The fair value of TBAs are included in ‘fixed maturities available for sale, at fair value.’

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Line of Credit Facility [Abstract]
Revolving credit agreement borrowings	$ 339,077	$ 100,000
Unfunded Investment Commitments [Abstract]
Investment commitments	1,230,000	$ 968,900
LOC Facilities [Member]
Line of Credit Facility [Abstract]
Letters of credit outstanding, amount	451,800
Investments pledged as collateral	517,400
Other secured letter of credit facilities
Line of Credit Facility [Abstract]
Maximum borrowing capacity	$ 228,600
Credit Agreement
Line of Credit Facility [Abstract]
Credit facility expiration date	Jun. 30, 2019
Revolving credit agreement borrowings	$ 100,000
Unsecured revolving loan and letter of credit facility
Line of Credit Facility [Abstract]
Maximum borrowing capacity	300,000
Secured letter of credit facility
Line of Credit Facility [Abstract]
Maximum borrowing capacity	500,000
Watford Re | Line of credit
Line of Credit Facility [Abstract]
Maximum borrowing capacity	$ 100,000
Credit facility expiration date	May 19, 2016
Letters of credit outstanding, amount	$ 102,800
Watford Re | Letter of credit
Line of Credit Facility [Abstract]
Maximum borrowing capacity	400,000
Watford Re | Other secured letter of credit facilities
Line of Credit Facility [Abstract]
Maximum borrowing capacity	$ 800,000
Credit facility expiration date	Jun. 4, 2018
Variable Interest Entity, Primary Beneficiary | Watford Re
Line of Credit Facility [Abstract]
Revolving credit agreement borrowings	$ 239,100

Share Transactions - Share repu

Share Transactions - Share repurchases (Details) - Common shares - USD ($) shares in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Class of Stock [Line Items]
Cumulative number of shares acquired since inception of share repurchase program	124.1
Aggregate purchase price of shares acquired since inception of share repurchase program	$ 3,610
Treasury stock, shares acquired (shares)	5.9	4.6
Treasury stock, value of shares acquired	$ 365.4	$ 251.9
Remaining authorized repurchase amount	$ 521.8

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective tax rate on income before income taxes (percentage)	5.50%	2.80%
Net deferred tax assets	$ 139.9		$ 131
Income taxes paid	$ 35.5	$ 13.3

Other Comprehensive Income (L60

Other Comprehensive Income (Loss) - Amounts reclassified from accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses	$ (8,901)	$ (8,593)	$ (17,274)	$ (26,313)
Income before income taxes	73,704	229,710	527,738	631,599
Income tax expense	(9,704)	(6,446)	(29,162)	(17,473)
Net of tax	80,033	228,675	479,159	619,191
Reclassification out of accumulated other comprehensive income | Unrealized appreciation on available-for-sale investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses)	(2,019)	27,715	63,671	77,488
Other-than-temporary impairment losses	(8,901)	(8,593)	(17,274)	(26,313)
Income before income taxes	(10,920)	19,122	46,397	51,175
Income tax expense	(1,358)	(1,639)	(6,529)	(4,158)
Net of tax	$ (12,278)	$ 17,483	$ 39,868	$ 47,017

Other Comprehensive Income (L61

Other Comprehensive Income (Loss) - Components of other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Before tax amount:
Unrealized holding gains (losses) arising during period, before tax	$ (44,687)	$ (90,276)	$ (46,929)	$ 100,274
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), before tax	(3,033)	0	(4,494)	0
Less reclassification of net realized gains included in net income, before tax	(10,920)	19,122	46,397	51,175
Foreign currency translation adjustments, before tax	(12,638)	(23,595)	(24,567)	(14,923)
Other comprehensive income (loss), before tax	(49,438)	(132,993)	(122,387)	34,176
Tax expense (benefit):
Unrealized holding gains (losses) arising during period, tax	9,204	343	4,593	11,112
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), tax	0	0	0	0
Less reclassification of net realized gains included in net income, tax	1,358	1,639	6,529	4,158
Foreign currency translation adjustments, tax	(556)	0	(1,308)	0
Other comprehensive income (loss), tax	7,290	(1,296)	(3,244)	6,954
Net of tax amount:
Unrealized holding gains (losses) arising during period, net of tax	(53,891)	(90,619)	(51,522)	89,162
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), net of tax	(3,033)	0	(4,494)	0
Less reclassification of net realized gains included in net income, net of tax	(12,278)	17,483	39,868	47,017
Foreign currency translation adjustments, net of tax	(12,082)	(23,595)	(23,259)	(14,923)
Net current period other comprehensive income (loss)	$ (56,728)	$ (131,697)	$ (119,143)	$ 27,222

Guarantor Financial Informati62

Guarantor Financial Information - Condensed consolidating balance sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Assets
Total investments	$ 15,815,437	$ 15,320,770
Cash	649,779	485,702	$ 663,726	$ 434,057
Investments in subsidiaries	0	0
Due from subsidiaries and affiliates	0	0
Premiums receivable	1,074,884	948,695
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	1,832,386	1,812,845
Contractholder receivables	1,436,154	1,309,192
Prepaid reinsurance premiums	442,346	377,078
Deferred acquisition costs, net	448,893	414,525
Other assets	2,070,713	1,337,274
Total assets	23,770,592	22,006,081	22,608,227
Liabilities
Reserve for losses and loss adjustment expenses	9,084,855	9,036,448
Unearned premiums	2,467,691	2,231,578
Reinsurance balances payable	235,562	219,312
Contractholder payables	1,436,154	1,309,192
Collateral held for insured obligations	242,928	184,219
Deposit accounting liabilities	270,876	327,384
Senior notes	791,264	791,141
Revolving credit agreement borrowings	339,077	100,000
Due to subsidiaries and affiliates	0	0
Other liabilities	1,760,119	688,161
Total liabilities	16,628,526	14,887,435	15,525,742
Redeemable noncontrolling interests	205,089	219,512
Shareholders' Equity
Total shareholders’ equity available to Arch	6,162,815	6,130,053	6,081,046
Non-redeemable noncontrolling interests	774,162	769,081	782,020
Total shareholders’ equity	6,936,977	6,899,134	6,863,066
Total liabilities, noncontrolling interests and shareholders’ equity	23,770,592	22,006,081
Reportable Legal Entities | ACGL (Parent Guarantor)
Assets
Total investments	34	107
Cash	10,381	3,218	5,969	3,223
Investments in subsidiaries	6,579,718	6,536,644
Due from subsidiaries and affiliates	0	48
Premiums receivable	0	0
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	0	0
Contractholder receivables	0	0
Prepaid reinsurance premiums	0	0
Deferred acquisition costs, net	0	0
Other assets	3,534	4,386
Total assets	6,593,667	6,544,403
Liabilities
Reserve for losses and loss adjustment expenses	0	0
Unearned premiums	0	0
Reinsurance balances payable	0	0
Contractholder payables	0	0
Collateral held for insured obligations	0	0
Deposit accounting liabilities	0	0
Senior notes	296,854	296,796
Revolving credit agreement borrowings	100,000	100,000
Due to subsidiaries and affiliates	14,080	417
Other liabilities	19,918	17,137
Total liabilities	430,852	414,350
Redeemable noncontrolling interests	0	0
Shareholders' Equity
Total shareholders’ equity available to Arch	6,162,815	6,130,053
Non-redeemable noncontrolling interests	0	0
Total shareholders’ equity	6,162,815	6,130,053
Total liabilities, noncontrolling interests and shareholders’ equity	6,593,667	6,544,403
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Assets
Total investments	55,053	62,867
Cash	9,256	2,787	15,710	509
Investments in subsidiaries	1,715,121	1,685,185
Due from subsidiaries and affiliates	48,548	7,517
Premiums receivable	0	0
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	0	0
Contractholder receivables	0	0
Prepaid reinsurance premiums	0	0
Deferred acquisition costs, net	0	0
Other assets	43,860	43,921
Total assets	1,871,838	1,802,277
Liabilities
Reserve for losses and loss adjustment expenses	0	0
Unearned premiums	0	0
Reinsurance balances payable	0	0
Contractholder payables	0	0
Collateral held for insured obligations	0	0
Deposit accounting liabilities	0	0
Senior notes	494,410	494,345
Revolving credit agreement borrowings	0	0
Due to subsidiaries and affiliates	35,000	7,505
Other liabilities	49,904	49,403
Total liabilities	579,314	551,253
Redeemable noncontrolling interests	0	0
Shareholders' Equity
Total shareholders’ equity available to Arch	1,292,524	1,251,024
Non-redeemable noncontrolling interests	0	0
Total shareholders’ equity	1,292,524	1,251,024
Total liabilities, noncontrolling interests and shareholders’ equity	1,871,838	1,802,277
Reportable Legal Entities | Other ACGL Subsidiaries
Assets
Total investments	15,775,050	15,257,796
Cash	630,142	479,697	642,047	430,325
Investments in subsidiaries	0	0
Due from subsidiaries and affiliates	442,508	370,429
Premiums receivable	1,521,960	1,331,511
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	5,739,246	5,584,973
Contractholder receivables	1,436,154	1,309,192
Prepaid reinsurance premiums	1,602,870	1,373,008
Deferred acquisition costs, net	448,893	414,525
Other assets	2,644,143	1,705,546
Total assets	30,240,966	27,826,677
Liabilities
Reserve for losses and loss adjustment expenses	12,969,850	12,784,030
Unearned premiums	3,628,215	3,227,508
Reinsurance balances payable	669,285	589,289
Contractholder payables	1,436,154	1,309,192
Collateral held for insured obligations	242,928	184,219
Deposit accounting liabilities	482,756	587,050
Senior notes	0	0
Revolving credit agreement borrowings	239,077	0
Due to subsidiaries and affiliates	441,976	370,072
Other liabilities	2,134,460	815,919
Total liabilities	22,244,701	19,867,279
Redeemable noncontrolling interests	219,789	219,512
Shareholders' Equity
Total shareholders’ equity available to Arch	7,002,314	6,970,805
Non-redeemable noncontrolling interests	774,162	769,081
Total shareholders’ equity	7,776,476	7,739,886
Total liabilities, noncontrolling interests and shareholders’ equity	30,240,966	27,826,677
Consolidating Adjustments and Eliminations
Assets
Total investments	(14,700)	0
Cash	0	0	$ 0	$ 0
Investments in subsidiaries	(8,294,839)	(8,221,829)
Due from subsidiaries and affiliates	(491,056)	(377,994)
Premiums receivable	(447,076)	(382,816)
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	(3,906,860)	(3,772,128)
Contractholder receivables	0	0
Prepaid reinsurance premiums	(1,160,524)	(995,930)
Deferred acquisition costs, net	0	0
Other assets	(620,824)	(416,579)
Total assets	(14,935,879)	(14,167,276)
Liabilities
Reserve for losses and loss adjustment expenses	(3,884,995)	(3,747,582)
Unearned premiums	(1,160,524)	(995,930)
Reinsurance balances payable	(433,723)	(369,977)
Contractholder payables	0	0
Collateral held for insured obligations	0	0
Deposit accounting liabilities	(211,880)	(259,666)
Senior notes	0	0
Revolving credit agreement borrowings	0	0
Due to subsidiaries and affiliates	(491,056)	(377,994)
Other liabilities	(444,163)	(194,298)
Total liabilities	(6,626,341)	(5,945,447)
Redeemable noncontrolling interests	(14,700)	0
Shareholders' Equity
Total shareholders’ equity available to Arch	(8,294,838)	(8,221,829)
Non-redeemable noncontrolling interests	0	0
Total shareholders’ equity	(8,294,838)	(8,221,829)
Total liabilities, noncontrolling interests and shareholders’ equity	$ (14,935,879)	$ (14,167,276)

Guarantor Financial Informati63

Guarantor Financial Information - Condensed consolidating statement of income and comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues
Net premiums earned	$ 936,683	$ 903,651	$ 2,790,385	$ 2,670,583
Net investment income	86,233	80,105	252,190	220,089
Net realized gains (losses)	(89,698)	18,515	(42,075)	92,356
Net impairment losses recognized in earnings	(5,868)	(8,593)	(12,780)	(26,313)
Other underwriting income	7,623	1,702	26,876	5,317
Equity in net income (loss) of investment funds accounted for using the equity method	(2,118)	4,966	19,938	17,459
Other income (loss)	(265)	(7,815)	52	(5,069)
Total revenues	932,590	992,531	3,034,586	2,974,422
Expenses
Losses and loss adjustment expenses	531,741	501,673	1,544,883	1,423,431
Acquisition expenses	171,566	163,547	510,067	482,047
Other operating expenses	156,959	149,480	483,449	451,629
Interest expense	13,300	4,152	30,047	32,890
Net foreign exchange (gains) losses	(14,680)	(56,031)	(61,598)	(47,174)
Total expenses	858,886	762,821	2,506,848	2,342,823
Income (loss) before income taxes	73,704	229,710	527,738	631,599
Income tax (expense) benefit	(9,704)	(6,446)	(29,162)	(17,473)
Income (loss) before equity in net income of subsidiaries	64,000	223,264	498,576	614,126
Equity in net income of subsidiaries	0	0	0	0
Net income	64,000	223,264	498,576	614,126
Amounts attributable to noncontrolling interests	16,033	5,411	(19,417)	5,065
Net income available to Arch	80,033	228,675	479,159	619,191
Preferred dividends	(5,484)	(5,484)	(16,453)	(16,453)
Net income (loss) available to Arch common shareholders	74,549	223,191	462,706	602,738
Comprehensive income (loss) available to Arch	23,401	96,978	360,112	646,413
Reportable Legal Entities | ACGL (Parent Guarantor)
Revenues
Net premiums earned	0	0	0	0
Net investment income	0	0	0	0
Net realized gains (losses)	0	0	0	0
Net impairment losses recognized in earnings	0	0	0	0
Other underwriting income	0	0	0	0
Equity in net income (loss) of investment funds accounted for using the equity method	0	0	0	0
Other income (loss)	0	0	0	0
Total revenues	0	0	0	0
Expenses
Losses and loss adjustment expenses	0	0	0	0
Acquisition expenses	0	0	0	0
Other operating expenses	10,536	10,056	36,068	35,613
Interest expense	5,863	5,858	17,581	17,565
Net foreign exchange (gains) losses	0	0	0	0
Total expenses	16,399	15,914	53,649	53,178
Income (loss) before income taxes	(16,399)	(15,914)	(53,649)	(53,178)
Income tax (expense) benefit	0	0	0	0
Income (loss) before equity in net income of subsidiaries	(16,399)	(15,914)	(53,649)	(53,178)
Equity in net income of subsidiaries	96,432	244,589	532,808	672,369
Net income	80,033	228,675	479,159	619,191
Amounts attributable to noncontrolling interests	0	0	0	0
Net income available to Arch	80,033	228,675	479,159	619,191
Preferred dividends	(5,484)	(5,484)	(16,453)	(16,453)
Net income (loss) available to Arch common shareholders	74,549	223,191	462,706	602,738
Comprehensive income (loss) available to Arch	23,401	96,978	360,112	646,413
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Revenues
Net premiums earned	0	0	0	0
Net investment income	764	0	1,569	0
Net realized gains (losses)	0	0	1	0
Net impairment losses recognized in earnings	0	0	0	0
Other underwriting income	0	0	0	0
Equity in net income (loss) of investment funds accounted for using the equity method	0	0	0	0
Other income (loss)	0	0	0	0
Total revenues	764	0	1,570	0
Expenses
Losses and loss adjustment expenses	0	0	0	0
Acquisition expenses	0	0	0	0
Other operating expenses	720	810	2,991	2,281
Interest expense	6,689	6,433	19,824	19,395
Net foreign exchange (gains) losses	0	0	0	0
Total expenses	7,409	7,243	22,815	21,676
Income (loss) before income taxes	(6,645)	(7,243)	(21,245)	(21,676)
Income tax (expense) benefit	2,324	2,097	7,434	8,179
Income (loss) before equity in net income of subsidiaries	(4,321)	(5,146)	(13,811)	(13,497)
Equity in net income of subsidiaries	13,620	10,459	42,192	41,945
Net income	9,299	5,313	28,381	28,448
Amounts attributable to noncontrolling interests	0	0	0	0
Net income available to Arch	9,299	5,313	28,381	28,448
Preferred dividends	0	0	0	0
Net income (loss) available to Arch common shareholders	9,299	5,313	28,381	28,448
Comprehensive income (loss) available to Arch	15,705	(10,614)	13,950	29,792
Reportable Legal Entities | Other ACGL Subsidiaries
Revenues
Net premiums earned	936,683	903,651	2,790,385	2,670,583
Net investment income	92,773	79,936	265,937	237,317
Net realized gains (losses)	(89,698)	18,515	(42,076)	92,356
Net impairment losses recognized in earnings	(5,868)	(8,593)	(12,780)	(26,313)
Other underwriting income	7,623	1,702	26,876	5,317
Equity in net income (loss) of investment funds accounted for using the equity method	(2,118)	4,966	19,938	17,459
Other income (loss)	(265)	(7,815)	52	(5,069)
Total revenues	939,130	992,362	3,048,332	2,991,650
Expenses
Losses and loss adjustment expenses	531,741	501,673	1,544,883	1,423,431
Acquisition expenses	171,566	163,547	510,067	482,047
Other operating expenses	145,703	138,614	444,390	413,735
Interest expense	7,734	(8,308)	7,476	13,158
Net foreign exchange (gains) losses	(11,762)	(35,244)	(44,450)	(28,449)
Total expenses	844,982	760,282	2,462,366	2,303,922
Income (loss) before income taxes	94,148	232,080	585,966	687,728
Income tax (expense) benefit	(12,028)	(8,543)	(36,596)	(25,652)
Income (loss) before equity in net income of subsidiaries	82,120	223,537	549,370	662,076
Equity in net income of subsidiaries	0	0	0	0
Net income	82,120	223,537	549,370	662,076
Amounts attributable to noncontrolling interests	15,712	5,411	(19,902)	5,065
Net income available to Arch	97,832	228,948	529,468	667,141
Preferred dividends	0	0	0	0
Net income (loss) available to Arch common shareholders	97,832	228,948	529,468	667,141
Comprehensive income (loss) available to Arch	44,127	104,501	427,569	691,968
Consolidating Adjustments and Eliminations
Revenues
Net premiums earned	0	0	0	0
Net investment income	(7,304)	169	(15,316)	(17,228)
Net realized gains (losses)	0	0	0	0
Net impairment losses recognized in earnings	0	0	0	0
Other underwriting income	0	0	0	0
Equity in net income (loss) of investment funds accounted for using the equity method	0	0	0	0
Other income (loss)	0	0	0	0
Total revenues	(7,304)	169	(15,316)	(17,228)
Expenses
Losses and loss adjustment expenses	0	0	0	0
Acquisition expenses	0	0	0	0
Other operating expenses	0	0	0	0
Interest expense	(6,986)	169	(14,834)	(17,228)
Net foreign exchange (gains) losses	(2,918)	(20,787)	(17,148)	(18,725)
Total expenses	(9,904)	(20,618)	(31,982)	(35,953)
Income (loss) before income taxes	2,600	20,787	16,666	18,725
Income tax (expense) benefit	0	0	0	0
Income (loss) before equity in net income of subsidiaries	2,600	20,787	16,666	18,725
Equity in net income of subsidiaries	(110,052)	(255,048)	(575,000)	(714,314)
Net income	(107,452)	(234,261)	(558,334)	(695,589)
Amounts attributable to noncontrolling interests	321	0	485	0
Net income available to Arch	(107,131)	(234,261)	(557,849)	(695,589)
Preferred dividends	0	0	0	0
Net income (loss) available to Arch common shareholders	(107,131)	(234,261)	(557,849)	(695,589)
Comprehensive income (loss) available to Arch	$ (59,832)	$ (93,887)	$ (441,519)	$ (721,760)

Guarantor Financial Informati64

Guarantor Financial Information - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 807,579	$ 799,659
Investing Activities
Purchases of fixed maturity investments	(22,382,104)	(22,030,862)
Purchases of equity securities	(485,526)	(366,578)
Purchases of other investments	(1,320,250)	(1,136,285)
Proceeds from the sale of fixed maturity investments	21,411,554	20,273,351
Proceeds from the sale of equity securities	509,008	305,034
Proceeds from sales, redemptions and maturities of other investments	858,368	566,518
Proceeds from redemptions and maturities of fixed maturity investments	630,397	636,729
Net settlements of derivative instruments	81,114	15,495
Proceeds from investment in joint venture	40,000	0
Net (purchases) sales of short-term investments	181,741	678,388
Change in cash collateral related to securities lending	28,685	(2,737)
Contributions to subsidiaries	0	0
Intercompany loans issued	0	0
Purchase of business, net of cash acquired	818	(235,578)
Purchases of fixed assets	(10,901)	(14,575)
Change in other assets	(43,654)	0
Net Cash Used For Investing Activities	(500,750)	(1,311,100)
Financing Activities
Purchases of common shares under share repurchase program	(365,383)	(251,919)
Proceeds from common shares issued, net	697	3,248
Proceeds from intercompany borrowings	0
Proceeds from borrowings	239,077	0
Repayments of intercompany borrowings		0
Change in cash collateral related to securities lending	(28,685)	2,737
Third party investment in non-redeemable noncontrolling interests	0	796,903
Third party investment in redeemable noncontrolling interests	0	219,233
Dividends paid to redeemable noncontrolling interests	(13,810)	(9,632)
Dividends paid to parent	0	0
Other	50,463	6,559
Preferred dividends paid	(16,453)	(16,453)
Net Cash Provided By (Used For) Financing Activities	(134,094)	750,676
Effects of exchange rate changes on foreign currency cash	(8,658)	(9,566)
Increase (decrease) in cash	164,077	229,669
Cash beginning of year	485,702	434,057
Cash end of period	649,779	663,726
Reportable Legal Entities | ACGL (Parent Guarantor)
Operating Activities
Net Cash Provided by (Used in) Operating Activities	382,329	265,694
Investing Activities
Purchases of fixed maturity investments	0	0
Purchases of equity securities	(8,070)	0
Purchases of other investments	0	0
Proceeds from the sale of fixed maturity investments	0	0
Proceeds from the sale of equity securities	0	0
Proceeds from sales, redemptions and maturities of other investments	0	0
Proceeds from redemptions and maturities of fixed maturity investments	0	0
Net settlements of derivative instruments	0	0
Proceeds from investment in joint venture	0
Net (purchases) sales of short-term investments	73	2,396
Change in cash collateral related to securities lending	0	0
Contributions to subsidiaries	0	0
Intercompany loans issued	0	0
Purchase of business, net of cash acquired	0	0
Purchases of fixed assets	(53)	(220)
Change in other assets	0	0
Net Cash Used For Investing Activities	(8,050)	2,176
Financing Activities
Purchases of common shares under share repurchase program	(365,383)	(251,919)
Proceeds from common shares issued, net	697	3,248
Proceeds from intercompany borrowings	14,023
Proceeds from borrowings	0
Repayments of intercompany borrowings		0
Change in cash collateral related to securities lending	0	0
Third party investment in non-redeemable noncontrolling interests		0
Third party investment in redeemable noncontrolling interests		0
Dividends paid to redeemable noncontrolling interests	0	0
Dividends paid to parent	0	0
Other	0	0
Preferred dividends paid	(16,453)	(16,453)
Net Cash Provided By (Used For) Financing Activities	(367,116)	(265,124)
Effects of exchange rate changes on foreign currency cash	0	0
Increase (decrease) in cash	7,163	2,746
Cash beginning of year	3,218	3,223
Cash end of period	10,381	5,969
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Operating Activities
Net Cash Provided by (Used in) Operating Activities	10,622	8,407
Investing Activities
Purchases of fixed maturity investments	(3,505)	(78,509)
Purchases of equity securities	0	0
Purchases of other investments	0	0
Proceeds from the sale of fixed maturity investments	23,507	0
Proceeds from the sale of equity securities	0	0
Proceeds from sales, redemptions and maturities of other investments	0	0
Proceeds from redemptions and maturities of fixed maturity investments	0	0
Net settlements of derivative instruments	0	0
Proceeds from investment in joint venture	0
Net (purchases) sales of short-term investments	(12,183)	408,760
Change in cash collateral related to securities lending	0	0
Contributions to subsidiaries	0	(313,207)
Intercompany loans issued	(39,500)	0
Purchase of business, net of cash acquired	0	0
Purchases of fixed assets	0	0
Change in other assets	0	0
Net Cash Used For Investing Activities	(31,681)	17,044
Financing Activities
Purchases of common shares under share repurchase program	0	0
Proceeds from common shares issued, net	0	0
Proceeds from intercompany borrowings	27,500
Proceeds from borrowings	0
Repayments of intercompany borrowings		(10,250)
Change in cash collateral related to securities lending	0	0
Third party investment in non-redeemable noncontrolling interests		0
Third party investment in redeemable noncontrolling interests		0
Dividends paid to redeemable noncontrolling interests	0	0
Dividends paid to parent	0	0
Other	28	0
Preferred dividends paid	0	0
Net Cash Provided By (Used For) Financing Activities	27,528	(10,250)
Effects of exchange rate changes on foreign currency cash	0	0
Increase (decrease) in cash	6,469	15,201
Cash beginning of year	2,787	509
Cash end of period	9,256	15,710
Reportable Legal Entities | Other ACGL Subsidiaries
Operating Activities
Net Cash Provided by (Used in) Operating Activities	859,525	822,558
Investing Activities
Purchases of fixed maturity investments	(22,378,599)	(21,952,353)
Purchases of equity securities	(477,456)	(366,578)
Purchases of other investments	(1,320,250)	(1,136,285)
Proceeds from the sale of fixed maturity investments	21,388,047	20,273,351
Proceeds from the sale of equity securities	509,008	305,034
Proceeds from sales, redemptions and maturities of other investments	858,368	566,518
Proceeds from redemptions and maturities of fixed maturity investments	630,397	636,729
Net settlements of derivative instruments	81,114	15,495
Proceeds from investment in joint venture	40,000
Net (purchases) sales of short-term investments	193,851	267,232
Change in cash collateral related to securities lending	28,685	(2,737)
Contributions to subsidiaries	(9,290)	(100,000)
Intercompany loans issued	(41,523)	10,250
Purchase of business, net of cash acquired	818	(235,578)
Purchases of fixed assets	(10,848)	(14,355)
Change in other assets	(43,654)	0
Net Cash Used For Investing Activities	(551,332)	(1,733,277)
Financing Activities
Purchases of common shares under share repurchase program	0	0
Proceeds from common shares issued, net	9,290	413,207
Proceeds from intercompany borrowings	39,500
Proceeds from borrowings	239,077
Repayments of intercompany borrowings		0
Change in cash collateral related to securities lending	(28,685)	2,737
Third party investment in non-redeemable noncontrolling interests		796,903
Third party investment in redeemable noncontrolling interests		219,233
Dividends paid to redeemable noncontrolling interests	(14,447)	(9,632)
Dividends paid to parent	(444,260)	(297,000)
Other	50,435	6,559
Preferred dividends paid	0	0
Net Cash Provided By (Used For) Financing Activities	(149,090)	1,132,007
Effects of exchange rate changes on foreign currency cash	(8,658)	(9,566)
Increase (decrease) in cash	150,445	211,722
Cash beginning of year	479,697	430,325
Cash end of period	630,142	642,047
Consolidating Adjustments and Eliminations
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(444,897)	(297,000)
Investing Activities
Purchases of fixed maturity investments	0	0
Purchases of equity securities	0	0
Purchases of other investments	0	0
Proceeds from the sale of fixed maturity investments	0	0
Proceeds from the sale of equity securities	0	0
Proceeds from sales, redemptions and maturities of other investments	0	0
Proceeds from redemptions and maturities of fixed maturity investments	0	0
Net settlements of derivative instruments	0	0
Proceeds from investment in joint venture	0
Net (purchases) sales of short-term investments	0	0
Change in cash collateral related to securities lending	0	0
Contributions to subsidiaries	9,290	413,207
Intercompany loans issued	81,023	(10,250)
Purchase of business, net of cash acquired	0	0
Purchases of fixed assets	0	0
Change in other assets	0	0
Net Cash Used For Investing Activities	90,313	402,957
Financing Activities
Purchases of common shares under share repurchase program	0	0
Proceeds from common shares issued, net	(9,290)	(413,207)
Proceeds from intercompany borrowings	(81,023)
Proceeds from borrowings	0
Repayments of intercompany borrowings		10,250
Change in cash collateral related to securities lending	0	0
Third party investment in non-redeemable noncontrolling interests		0
Third party investment in redeemable noncontrolling interests		0
Dividends paid to redeemable noncontrolling interests	637	0
Dividends paid to parent	444,260	297,000
Other	0	0
Preferred dividends paid	0	0
Net Cash Provided By (Used For) Financing Activities	354,584	(105,957)
Effects of exchange rate changes on foreign currency cash	0	0
Increase (decrease) in cash	0	0
Cash beginning of year	0	0
Cash end of period	$ 0	$ 0

Transactions with Related Par65

Transactions with Related Parties (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Related Party Transaction [Line Items]
Investment commitments	$ 1,230,000		$ 1,230,000		$ 968,900
Purchases of other investments			1,320,250	$ 1,136,285
Common director | The Carlyle Group
Related Party Transaction [Line Items]
Investment commitments	670,900		670,900
Unfunded commitments	462,400		462,400
Purchases of other investments	97,700	$ 55,500
Aggregate distributions received	$ 30,300	$ 41,000
Return of capital from other investments			$ 25,500	$ 32,800