Arch Capital (ACGL) 10-Q 7 Aug 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Jul. 31, 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	Jun. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		122,441,665

Unaudited Consolidated Balance

Unaudited Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Investments:
Fixed maturities available for sale, at fair value (amortized cost: $9,945,598 and $10,701,557)	$ 9,927,603	$ 10,750,770
Short-term investments available for sale, at fair value (amortized cost: $878,437 and $801,758)	875,727	797,226
Collateral received under securities lending, at fair value (amortized cost: $373,909 and $40,473)	377,897	44,301
Equity securities available for sale, at fair value (cost: $615,055 and $562,534)	701,623	658,182
Other investments available for sale, at fair value (cost: $333,438 and $264,747)	377,677	296,224
Investments accounted for using the fair value option	2,613,487	2,425,053
Investments accounted for using the equity method	472,926	349,014
Total investments	15,346,940	15,320,770
Cash	525,074	485,702
Accrued investment income	80,129	74,316
Securities pledged under securities lending, at fair value (amortized cost: $374,447 and $52,076)	373,969	50,802
Premiums receivable	1,181,636	948,695
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	1,831,227	1,812,845
Contractholder receivables	1,393,138	1,309,192
Prepaid reinsurance premiums	442,141	377,078
Deferred acquisition costs, net	448,647	414,525
Receivable for securities sold	454,057	78,170
Goodwill and intangible assets	102,518	109,539
Other assets	905,449	1,024,447
Total assets	23,084,925	22,006,081
Liabilities
Reserve for losses and loss adjustment expenses	9,082,281	9,036,448
Unearned premiums	2,442,923	2,231,578
Reinsurance balances payable	252,462	219,312
Contractholder payables	1,393,138	1,309,192
Deposit accounting liabilities	277,523	327,384
Senior notes	791,222	791,141
Revolving credit agreement borrowings	100,000	100,000
Securities lending payable	383,965	50,529
Payable for securities purchased	468,015	128,413
Other liabilities	756,005	693,438
Total liabilities	$ 15,947,534	$ 14,887,435
Commitments and Contingencies
Redeemable noncontrolling interests	$ 204,996	$ 219,512
Shareholders' Equity
Non-cumulative preferred shares	325,000	325,000
Common shares ($0.0033 par, shares issued: 172,780,590 and 171,672,408)	576	572
Additional paid-in capital	437,533	383,073
Retained earnings	7,242,728	6,854,571
Accumulated other comprehensive income, net of deferred income tax	66,441	128,856
Common shares held in treasury, at cost (shares: 50,376,681 and 44,304,474)	(1,934,763)	(1,562,019)
Total shareholders' equity available to Arch	6,137,515	6,130,053
Non-redeemable noncontrolling interests	794,880	769,081
Total shareholders' equity	6,932,395	6,899,134
Total liabilities, noncontrolling interests and shareholders' equity	$ 23,084,925	$ 22,006,081

Unaudited Consolidated Balance3

Unaudited Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fixed maturities available for sale, at amortized cost	$ 9,945,598	$ 10,701,557
Short-term investments available for sale, at amortized cost	878,437	801,758
Collateral received under securities lending, at amortized cost	373,909	40,473
Equity securities, at cost	615,055	562,534
Other investments available for sale, at cost	333,438	264,747
Securities pledged under securities lending, at amortized cost	$ 374,447	$ 52,076
Common shares, par value per share	$ 0.0033	$ 0.0033
Common shares issued (shares)	172,780,590	171,672,408
Common shares held in treasury (shares)	50,376,681	44,304,474

Unaudited Consolidated Statemen

Unaudited Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues
Net premiums written	$ 943,580	$ 971,928	$ 2,010,575	$ 2,036,918
Change in unearned premiums	(142)	(64,776)	(156,873)	(269,986)
Net premiums earned	943,438	907,152	1,853,702	1,766,932
Net investment income	86,963	72,990	165,957	139,984
Net realized gains (losses)	(35,725)	54,144	47,623	73,841
Other-than-temporary impairment losses	(1,126)	(14,749)	(8,373)	(17,720)
Less investment impairments recognized in other comprehensive income, before taxes	13	0	1,461	0
Net impairment losses recognized in earnings	(1,113)	(14,749)	(6,912)	(17,720)
Other underwriting income	7,717	2,033	19,253	3,615
Equity in net income of investment funds accounted for using the equity method	16,167	9,240	22,056	12,493
Other income	2,205	4,850	317	2,746
Total revenues	1,019,652	1,035,660	2,101,996	1,981,891
Expenses
Losses and loss adjustment expenses	519,426	485,518	1,013,142	921,758
Acquisition expenses	175,425	158,158	338,501	318,500
Other operating expenses	168,608	156,350	326,490	302,149
Interest expense	4,011	14,334	16,747	28,738
Net foreign exchange losses (gains)	19,583	2,294	(46,918)	8,857
Total expenses	887,053	816,654	1,647,962	1,580,002
Income before income taxes	132,599	219,006	454,034	401,889
Income tax expense	(6,780)	(7,289)	(19,458)	(11,027)
Net income	125,819	211,717	434,576	390,862
Amounts attributable to noncontrolling interests	(10,029)	(3,701)	(35,450)	(346)
Net income available to Arch	115,790	208,016	399,126	390,516
Preferred dividends	(5,485)	(5,485)	(10,969)	(10,969)
Net income available to Arch common shareholders	$ 110,305	$ 202,531	$ 388,157	$ 379,547
Net income per common share
Basic (per share)	$ 0.91	$ 1.53	$ 3.16	$ 2.87
Diluted (per share)	$ 0.88	$ 1.48	$ 3.05	$ 2.78
Weighted average common shares and common share equivalents outstanding
Basic (shares)	121,719,214	132,650,634	122,957,384	132,256,462
Diluted (shares)	125,885,420	136,889,944	127,156,713	136,716,889

Unaudited Consolidated Stateme5

Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Comprehensive Income
Net income	$ 125,819	$ 211,717	$ 434,576	$ 390,862
Unrealized appreciation (decline) in value of available-for-sale investments:
Unrealized holding gains (losses) arising during period	(81,935)	108,428	2,369	179,781
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(13)	0	(1,461)	0
Reclassification of net realized gains, net of income taxes, included in net income	(21,214)	(8,285)	(52,146)	(29,534)
Foreign currency translation adjustments	11,580	10,021	(11,177)	8,672
Comprehensive income	34,237	321,881	372,161	549,781
Amounts attributable to noncontrolling interests	(10,029)	(3,701)	(35,450)	(346)
Comprehensive income available to Arch	$ 24,208	$ 318,180	$ 336,711	$ 549,435

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			5	6,360
Exercise of stock options				11,233
Amortization of share-based compensation				35,627
Other				471
Net income	$ 390,862				390,862
Amounts attributable to noncontrolling interests	(346)				(346)
Preferred share dividends	(10,969)				(10,969)
Unrealized holding (losses) gains arising during period, net of reclassification adjustment							150,247
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	0						0
Foreign currency translation adjustments	8,672							8,672
Shares repurchased for treasury									(10,259)
Balance at end of period at Jun. 30, 2014	6,229,399	325,000	570	353,208	6,421,701	233,883	230,939	2,944	(1,104,963)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2014	792,340
Total shareholders’ equity at Jun. 30, 2014	7,021,739
Net income	211,717
Amounts attributable to noncontrolling interests	(3,701)
Preferred share dividends	(5,485)
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	0
Foreign currency translation adjustments	10,021
Balance at end of period at Jun. 30, 2014	6,229,399	325,000	570	353,208	6,421,701	233,883	230,939	2,944	(1,104,963)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2014	792,340
Total shareholders’ equity at Jun. 30, 2014	7,021,739
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	7,378
Exercise of stock options				9,624
Amortization of share-based compensation				36,044
Other				1,414
Net income	434,576				434,576
Amounts attributable to noncontrolling interests	(35,450)				(35,450)
Preferred share dividends	(10,969)				(10,969)
Unrealized holding (losses) gains arising during period, net of reclassification adjustment							(49,777)
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(1,461)						(1,461)
Foreign currency translation adjustments	(11,177)							(11,177)
Shares repurchased for treasury									(372,744)
Balance at end of period at Jun. 30, 2015	6,137,515	325,000	576	437,533	7,242,728	66,441	110,360	(43,919)	(1,934,763)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2015	794,880
Total shareholders’ equity at Jun. 30, 2015	6,932,395
Net income	125,819
Amounts attributable to noncontrolling interests	(10,029)
Preferred share dividends	(5,485)
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(13)
Foreign currency translation adjustments	11,580
Balance at end of period at Jun. 30, 2015	6,137,515	$ 325,000	$ 576	$ 437,533	$ 7,242,728	$ 66,441	$ 110,360	$ (43,919)	$ (1,934,763)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2015	794,880
Total shareholders’ equity at Jun. 30, 2015	$ 6,932,395

Unaudited Consolidated Stateme7

Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating Activities
Net income	$ 434,576	$ 390,862
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized gains	(60,818)	(87,520)
Net impairment losses recognized in earnings	6,912	17,720
Equity in net income or loss of investment funds accounted for using the equity method and other income or loss	(10,349)	(135)
Share-based compensation	36,044	35,627
Changes in:
Reserve for losses and loss adjustment expenses, net of unpaid losses and loss adjustment expenses recoverable	91,616	60,474
Unearned premiums, net of prepaid reinsurance premiums	156,873	269,986
Premiums receivable	(206,642)	(325,953)
Deferred acquisition costs, net	(39,009)	(55,822)
Reinsurance balances payable	19,657	65,803
Other liabilities	(94,841)	43,133
Other items	51,180	38,888
Net Cash Provided By Operating Activities	385,199	453,063
Investing Activities
Purchases of fixed maturity investments	(14,641,391)	(14,311,748)
Purchases of equity securities	(288,535)	(174,687)
Purchases of other investments	(1,273,780)	(1,022,987)
Proceeds from the sale of fixed maturity investments	14,355,519	13,204,854
Proceeds from the sale of equity securities	272,343	98,687
Proceeds from sales, redemptions and maturities of other investments	1,078,675	618,707
Proceeds from redemptions and maturities of fixed maturity investments	474,984	432,040
Proceeds from investment in joint venture	40,000	0
Net sales of short-term investments	3,707	430,304
Change in cash collateral related to securities lending	(18,329)	18,701
Purchase of business, net of cash acquired	818	(235,578)
Purchases of furniture, equipment and other assets	(43,165)	(10,360)
Net Cash Used For Investing Activities	(39,154)	(952,067)
Financing Activities
Purchases of common shares under share repurchase program	(361,877)	0
Proceeds from common shares issued, net	2,178	2,521
Change in cash collateral related to securities lending	18,329	(18,701)
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	(9,313)	(4,816)
Other	55,018	4,706
Preferred dividends paid	(10,969)	(10,969)
Net Cash Provided By (Used For) Financing Activities	(306,634)	988,877
Effects of exchange rate changes on foreign currency cash	(39)	2,513
Increase in cash	39,372	492,386
Cash beginning of year	485,702	434,057
Cash end of period	525,074	926,443
Income taxes paid	25,992	8,279
Interest paid	$ 25,076	$ 21,696

General

General	6 Months Ended
	Jun. 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	6 Months Ended
	Jun. 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	6 Months Ended
	Jun. 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 June 30, 2015 , Watford Re’s liabilities included unearned premiums of $247.6 million and reserves for losses and loss adjustment expenses of $173.2 million , some of which is related to transactions with the Company. For the six months ended June 30, 2015 , Watford Re generated $137.8 million of cash provided by operating activities and $40.3 million of cash provided by financing activities, partially offset by $134.9 million of cash used for investing activities. Because Watford Re is an independent company, the assets of Watford Re can be used only to settle obligations of Watford Re and Watford Re is solely responsible for its own liabilities and commitments. The Company’s financial exposure to Watford Re is limited to its investment in Watford Re’s common 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 June 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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Balance, beginning of period $ 789,594 $ 793,496 $ 769,081 $ — Sale of shares to noncontrolling interests — — — 796,903 Amounts attributable to noncontrolling interests 5,286 (1,156 ) 25,799 (4,563 ) Balance, end of period $ 794,880 $ 792,340 $ 794,880 $ 792,340 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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Balance, beginning of period $ 219,604 $ 219,234 $ 219,512 $ — Sale of shares to noncontrolling interests — — — 219,233 Shares acquired by the Company (1) (14,700 ) — (14,700 ) — Accretion of preference share issuance costs 92 92 184 93 Balance, end of period $ 204,996 $ 219,326 $ 204,996 $ 219,326 _________________________________________________ (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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Amounts attributable to non-redeemable noncontrolling interests $ (5,286 ) $ 1,156 $ (25,799 ) $ 4,563 Dividends attributable to redeemable noncontrolling interests (4,743 ) (4,857 ) (9,651 ) (4,909 ) Amounts attributable to noncontrolling interests $ (10,029 ) $ (3,701 ) $ (35,450 ) $ (346 )

Earnings Per Common Share

Earnings Per Common Share	6 Months Ended
	Jun. 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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Numerator: Net income $ 125,819 $ 211,717 $ 434,576 $ 390,862 Amounts attributable to noncontrolling interests (10,029 ) (3,701 ) (35,450 ) (346 ) Net income available to Arch 115,790 208,016 399,126 390,516 Preferred dividends (5,485 ) (5,485 ) (10,969 ) (10,969 ) Net income available to Arch common shareholders $ 110,305 $ 202,531 $ 388,157 $ 379,547 Denominator: Weighted average common shares outstanding — basic 121,719,214 132,650,634 122,957,384 132,256,462 Effect of dilutive common share equivalents: Nonvested restricted shares 1,258,741 1,144,621 1,334,633 1,236,408 Stock options (1) 2,907,465 3,094,689 2,864,696 3,224,019 Weighted average common shares and common share equivalents outstanding — diluted 125,885,420 136,889,944 127,156,713 136,716,889 Earnings per common share: Basic $ 0.91 $ 1.53 $ 3.16 $ 2.87 Diluted $ 0.88 $ 1.48 $ 3.05 $ 2.78 _________________________________________________ (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 second quarter and 2014 second quarter , the number of stock options excluded were 1,009,113 and 978,237 , respectively. For the six months ended June 30, 2015 and 2014 , the number of stock options excluded were 1,187,162 and 1,318,662 , respectively.

Segment Information

Segment Information	6 Months Ended
	Jun. 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 consists of the Company’s mortgage insurance and reinsurance business and includes the results of Arch Mortgage Insurance Company (“Arch MI U.S.”). 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.” Arch MI U.S. provides mortgage insurance to banks, credit unions and other lenders nationwide. The mortgage segment also provides reinsurance on a global basis, direct mortgage insurance in Europe and various risk-sharing products to government agencies and mortgage lenders. 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 June 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 744,810 $ 342,101 $ 68,572 $ 1,155,253 $ 127,954 $ 1,199,209 Premiums ceded (235,743 ) (89,446 ) (6,902 ) (331,861 ) (7,766 ) (255,629 ) Net premiums written 509,067 252,655 61,670 823,392 120,188 943,580 Change in unearned premiums 758 21,310 (9,211 ) 12,857 (12,999 ) (142 ) Net premiums earned 509,825 273,965 52,459 836,249 107,189 943,438 Other underwriting income 521 2,658 3,686 6,865 852 7,717 Losses and loss adjustment expenses (320,926 ) (111,183 ) (9,639 ) (441,748 ) (77,678 ) (519,426 ) Acquisition expenses, net (76,723 ) (58,360 ) (10,200 ) (145,283 ) (30,142 ) (175,425 ) Other operating expenses (89,054 ) (39,007 ) (19,679 ) (147,740 ) (3,450 ) (151,190 ) Underwriting income (loss) $ 23,643 $ 68,073 $ 16,627 108,343 (3,229 ) 105,114 Net investment income 67,171 19,792 86,963 Net realized gains (losses) (26,860 ) (8,865 ) (35,725 ) Net impairment losses recognized in earnings (1,113 ) — (1,113 ) Equity in net income of investment funds accounted for using the equity method 16,167 — 16,167 Other income (loss) 2,205 — 2,205 Other expenses (17,418 ) — (17,418 ) Interest expense (4,011 ) — (4,011 ) Net foreign exchange gains (losses) (22,571 ) 2,988 (19,583 ) Income (loss) before income taxes 121,913 10,686 132,599 Income tax expense (6,780 ) — (6,780 ) Net income (loss) 115,133 10,686 125,819 Dividends attributable to redeemable noncontrolling interests — (4,743 ) (4,743 ) Amounts attributable to noncontrolling interests — (5,286 ) (5,286 ) Net income (loss) available to Arch 115,133 657 115,790 Preferred dividends (5,485 ) — (5,485 ) Net income (loss) available to Arch common shareholders $ 109,648 $ 657 $ 110,305 Underwriting Ratios Loss ratio 62.9 % 40.6 % 18.4 % 52.8 % 72.5 % 55.1 % Acquisition expense ratio 15.0 % 21.3 % 19.4 % 17.4 % 28.1 % 18.6 % Other operating expense ratio 17.5 % 14.2 % 37.5 % 17.7 % 3.2 % 16.0 % Combined ratio 95.4 % 76.1 % 75.3 % 87.9 % 103.8 % 89.7 % Goodwill and intangible assets $ 30,968 $ 2,420 $ 69,130 $ 102,518 $ — $ 102,518 Total investable assets $ 14,513,554 $ 1,340,574 $ 15,854,128 Total assets 21,323,611 1,761,314 23,084,925 Total liabilities 15,299,256 648,278 15,947,534 _________________________________________________ (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 June 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 852,231 $ 349,841 $ 55,476 $ 1,256,934 $ 54,562 $ 1,271,761 Premiums ceded (273,349 ) (58,994 ) (5,079 ) (336,808 ) (2,760 ) (299,833 ) Net premiums written 578,882 290,847 50,397 920,126 51,802 971,928 Change in unearned premiums (71,170 ) 44,780 436 (25,954 ) (38,822 ) (64,776 ) Net premiums earned 507,712 335,627 50,833 894,172 12,980 907,152 Other underwriting income 514 303 1,216 2,033 — 2,033 Losses and loss adjustment expenses (311,526 ) (150,325 ) (15,473 ) (477,324 ) (8,194 ) (485,518 ) Acquisition expenses, net (76,449 ) (66,035 ) (11,481 ) (153,965 ) (4,193 ) (158,158 ) Other operating expenses (85,829 ) (37,666 ) (16,288 ) (139,783 ) (1,635 ) (141,418 ) Underwriting income (loss) $ 34,422 $ 81,904 $ 8,807 125,133 (1,042 ) 124,091 Net investment income 72,458 532 72,990 Net realized gains (losses) 50,966 3,178 54,144 Net impairment losses recognized in earnings (14,749 ) — (14,749 ) Equity in net income of investment funds accounted for using the equity method 9,240 — 9,240 Other income (loss) 4,850 — 4,850 Other expenses (15,279 ) 347 (14,932 ) Interest expense (14,334 ) — (14,334 ) Net foreign exchange gains (losses) (2,764 ) 470 (2,294 ) Income (loss) before income taxes 215,521 3,485 219,006 Income tax expense (7,289 ) — (7,289 ) Net income (loss) 208,232 3,485 211,717 Dividends attributable to redeemable noncontrolling interests — (4,857 ) (4,857 ) Amounts attributable to noncontrolling interests — 1,156 1,156 Net income (loss) available to Arch 208,232 (216 ) 208,016 Preferred dividends (5,485 ) — (5,485 ) Net income (loss) available to Arch common shareholders $ 202,747 $ (216 ) $ 202,531 Underwriting Ratios Loss ratio 61.4 % 44.8 % 30.4 % 53.4 % 63.1 % 53.5 % Acquisition expense ratio 15.1 % 19.7 % 22.6 % 17.2 % 32.3 % 17.4 % Other operating expense ratio 16.9 % 11.2 % 32.0 % 15.6 % 12.6 % 15.6 % Combined ratio 93.4 % 75.7 % 85.0 % 86.2 % 108.0 % 86.5 % Goodwill and intangible assets $ 24,498 $ 4,942 $ 89,281 $ 118,721 $ — $ 118,721 Total investable assets $ 14,688,808 $ 1,114,719 $ 15,803,527 Total assets 21,204,129 1,363,318 22,567,447 Total liabilities 15,072,875 253,507 15,326,382 _________________________________________________ (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. Six Months Ended June 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 1,510,963 $ 827,213 $ 129,113 $ 2,466,931 $ 256,587 $ 2,541,231 Premiums ceded (459,893 ) (226,015 ) (15,572 ) (701,122 ) (11,821 ) (530,656 ) Net premiums written 1,051,070 601,198 113,541 1,765,809 244,766 2,010,575 Change in unearned premiums (33,331 ) (47,516 ) (10,715 ) (91,562 ) (65,311 ) (156,873 ) Net premiums earned 1,017,739 553,682 102,826 1,674,247 179,455 1,853,702 Other underwriting income 948 4,087 11,404 16,439 2,814 19,253 Losses and loss adjustment expenses (638,822 ) (223,715 ) (23,448 ) (885,985 ) (127,157 ) (1,013,142 ) Acquisition expenses, net (151,801 ) (114,964 ) (20,618 ) (287,383 ) (51,118 ) (338,501 ) Other operating expenses (177,173 ) (77,051 ) (40,048 ) (294,272 ) (5,455 ) (299,727 ) Underwriting income (loss) $ 50,891 $ 142,039 $ 30,116 223,046 (1,461 ) 221,585 Net investment income 137,459 28,498 165,957 Net realized gains (losses) 38,649 8,974 47,623 Net impairment losses recognized in earnings (6,912 ) — (6,912 ) Equity in net income of investment funds accounted for using the equity method 22,056 — 22,056 Other income (loss) 317 — 317 Other expenses (26,763 ) — (26,763 ) Interest expense (16,747 ) — (16,747 ) Net foreign exchange gains (losses) 44,282 2,636 46,918 Income (loss) before income taxes 415,387 38,647 454,034 Income tax expense (19,458 ) — (19,458 ) Net income (loss) 395,929 38,647 434,576 Dividends attributable to redeemable noncontrolling interests — (9,651 ) (9,651 ) Amounts attributable to noncontrolling interests — (25,799 ) (25,799 ) Net income (loss) available to Arch 395,929 3,197 399,126 Preferred dividends (10,969 ) — (10,969 ) Net income (loss) available to Arch common shareholders $ 384,960 $ 3,197 $ 388,157 Underwriting Ratios Loss ratio 62.8 % 40.4 % 22.8 % 52.9 % 70.9 % 54.7 % Acquisition expense ratio 14.9 % 20.8 % 20.1 % 17.2 % 28.5 % 18.3 % Other operating expense ratio 17.4 % 13.9 % 38.9 % 17.6 % 3.0 % 16.2 % Combined ratio 95.1 % 75.1 % 81.8 % 87.7 % 102.4 % 89.2 % _________________________________________________ (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. Six Months Ended June 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 1,582,877 $ 866,894 $ 103,383 $ 2,552,070 $ 86,756 $ 2,566,897 Premiums ceded (458,393 ) (132,121 ) (9,718 ) (599,148 ) (2,760 ) (529,979 ) Net premiums written 1,124,484 734,773 93,665 1,952,922 83,996 2,036,918 Change in unearned premiums (139,271 ) (57,798 ) (4,067 ) (201,136 ) (68,850 ) (269,986 ) Net premiums earned 985,213 676,975 89,598 1,751,786 15,146 1,766,932 Other underwriting income 1,014 619 1,982 3,615 — 3,615 Losses and loss adjustment expenses (598,296 ) (289,961 ) (23,951 ) (912,208 ) (9,550 ) (921,758 ) Acquisition expenses, net (153,381 ) (139,468 ) (20,635 ) (313,484 ) (5,016 ) (318,500 ) Other operating expenses (166,973 ) (73,861 ) (30,164 ) (270,998 ) (2,744 ) (273,742 ) Underwriting income (loss) $ 67,577 $ 174,304 $ 16,830 258,711 (2,164 ) 256,547 Net investment income 139,451 533 139,984 Net realized gains (losses) 70,663 3,178 73,841 Net impairment losses recognized in earnings (17,720 ) — (17,720 ) Equity in net income of investment funds accounted for using the equity method 12,493 — 12,493 Other income (loss) 2,746 — 2,746 Other expenses (26,078 ) (2,329 ) (28,407 ) Interest expense (28,738 ) — (28,738 ) Net foreign exchange gains (losses) (9,420 ) 563 (8,857 ) Income (loss) before income taxes 402,108 (219 ) 401,889 Income tax expense (11,027 ) — (11,027 ) Net income (loss) 391,081 (219 ) 390,862 Dividends attributable to redeemable noncontrolling interests — (4,909 ) (4,909 ) Amounts attributable to noncontrolling interests — 4,563 4,563 Net income (loss) available to Arch 391,081 (565 ) 390,516 Preferred dividends (10,969 ) — (10,969 ) Net income (loss) available to Arch common shareholders $ 380,112 $ (565 ) $ 379,547 Underwriting Ratios Loss ratio 60.7 % 42.8 % 26.7 % 52.1 % 63.1 % 52.2 % Acquisition expense ratio 15.6 % 20.6 % 23.0 % 17.9 % 33.1 % 18.0 % Other operating expense ratio 16.9 % 10.9 % 33.7 % 15.5 % 18.1 % 15.5 % Combined ratio 93.2 % 74.3 % 83.4 % 85.5 % 114.3 % 85.7 % _________________________________________________ (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.

Investment Information

Investment Information	6 Months Ended
	Jun. 30, 2015
Disclosure Investment Information [Abstract]
Investment Information	Investment Information At June 30, 2015 , total investable assets of $15.85 billion included $14.51 billion managed by the Company and $1.34 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) June 30, 2015 Fixed maturities (1): Corporate bonds $ 2,833,849 $ 26,401 $ (51,717 ) $ 2,859,165 $ (681 ) Mortgage backed securities 837,680 12,315 (4,231 ) 829,596 (3,564 ) Municipal bonds 1,760,384 19,601 (9,004 ) 1,749,787 — Commercial mortgage backed securities 832,159 6,760 (4,922 ) 830,321 — U.S. government and government agencies 1,899,868 8,463 (3,720 ) 1,895,125 — Non-U.S. government securities 786,276 10,343 (32,720 ) 808,653 — Asset backed securities 1,351,356 7,324 (3,364 ) 1,347,396 (22 ) Total 10,301,572 91,207 (109,678 ) 10,320,043 (4,267 ) Equity securities 701,623 105,174 (18,606 ) 615,055 — Other investments 377,677 46,166 (1,927 ) 333,438 — Short-term investments 875,727 55 (2,767 ) 878,439 — Total $ 12,256,599 $ 242,602 $ (132,978 ) $ 12,146,975 $ (4,267 ) 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 June 30, 2015 , the net unrealized gain related to securities for which a non-credit OTTI was recognized in AOCI was $0.3 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 June 30, 2015 Fixed maturities (1): Corporate bonds $ 1,659,276 $ (40,616 ) $ 92,244 $ (11,101 ) $ 1,751,520 $ (51,717 ) Mortgage backed securities 437,043 (3,574 ) 45,082 (657 ) 482,125 (4,231 ) Municipal bonds 784,691 (8,562 ) 3,530 (442 ) 788,221 (9,004 ) Commercial mortgage backed securities 374,338 (4,912 ) 2,893 (10 ) 377,231 (4,922 ) U.S. government and government agencies 426,224 (3,720 ) — — 426,224 (3,720 ) Non-U.S. government securities 431,360 (16,841 ) 77,314 (15,879 ) 508,674 (32,720 ) Asset backed securities 281,650 (2,161 ) 130,987 (1,203 ) 412,637 (3,364 ) Total 4,394,582 (80,386 ) 352,050 (29,292 ) 4,746,632 (109,678 ) Equity securities 286,325 (18,606 ) — — 286,325 (18,606 ) Other investments 89,863 (1,927 ) — — 89,863 (1,927 ) Short-term investments 60,287 (2,767 ) — — 60,287 (2,767 ) Total $ 4,831,057 $ (103,686 ) $ 352,050 $ (29,292 ) $ 5,183,107 $ (132,978 ) 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 June 30, 2015 , on a lot level basis, approximately 2,620 security lots out of a total of approximately 5,580 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 . 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. June 30, 2015 December 31, 2014 Maturity Estimated Fair Value Amortized Cost Estimated Amortized Cost Due in one year or less $ 369,356 $ 374,710 $ 235,930 $ 233,794 Due after one year through five years 4,101,484 4,106,002 4,074,562 4,077,408 Due after five years through 10 years 2,468,013 2,487,840 2,475,726 2,461,356 Due after 10 years 341,524 344,178 279,542 273,372 7,280,377 7,312,730 7,065,760 7,045,930 Mortgage backed securities 837,680 829,596 943,343 928,342 Commercial mortgage backed securities 832,159 830,321 1,114,528 1,103,756 Asset backed securities 1,351,356 1,347,396 1,677,941 1,675,605 Total (1) $ 10,301,572 $ 10,320,043 $ 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 June 30, 2015 , the fair value of the cash collateral received on securities lending was $62.6 million , which included $5.7 million that was reinvested in sub-prime mortgage backed securities, and the fair value of security collateral received was $315.1 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: June 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 $ 335,233 $ — $ — $ — $ 335,233 Corporate bonds 44,139 — — — 44,139 Equity securities 4,593 — — — 4,593 Total $ 383,965 $ — $ — $ — $ 383,965 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 $ 383,965 Other Investments The following table summarizes the Company’s other investments, including available for sale and fair value option components: June 30, December 31, Available for sale: Asian and emerging markets $ 287,666 $ 236,586 Investment grade fixed income 58,829 59,638 Credit related funds 13,773 — Other 17,409 — Total available for sale 377,677 296,224 Fair value option: Term loan investments (par value: $1,077,945 and $1,094,337) 1,061,696 1,073,649 Mezzanine debt funds 115,019 121,341 Credit related funds 138,070 114,436 Investment grade fixed income 60,383 69,108 Asian and emerging markets 26,494 25,800 Other (1) 189,709 137,094 Total fair value option 1,591,371 1,541,428 Total $ 1,969,048 $ 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: June 30, December 31, Fixed maturities $ 854,170 $ 632,024 Other investments 1,591,371 1,541,428 Short-term investments 167,698 251,601 Equity securities 248 — Investments accounted for using the fair value option $ 2,613,487 $ 2,425,053 Net Investment Income The components of net investment income were derived from the following sources: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Fixed maturities $ 71,275 $ 65,869 $ 139,871 $ 128,318 Term loan investments 18,033 6,908 32,777 12,577 Equity securities (dividends) 2,578 3,271 5,257 6,192 Short-term investments 225 107 421 512 Other (1) 10,489 9,100 23,236 13,819 Gross investment income 102,600 85,255 201,562 161,418 Investment expenses (15,637 ) (12,265 ) (35,605 ) (21,434 ) Net investment income $ 86,963 $ 72,990 $ 165,957 $ 139,984 _________________________________________________ (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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Available for sale securities: Gross gains on investment sales $ 82,233 $ 56,763 $ 179,824 $ 122,814 Gross losses on investment sales (58,974 ) (33,028 ) (114,134 ) (73,041 ) Change in fair value of assets and liabilities accounted for using the fair value option: Fixed maturities (5,191 ) 10,984 (8,493 ) 9,341 Other investments 785 17,985 7,072 28,761 Equity securities (69 ) — (71 ) — Short-term investments (4,375 ) — 1,471 — Derivative instruments (1) (41,496 ) 12,402 (4,820 ) (366 ) Other (2) (8,638 ) (10,962 ) (13,226 ) (13,668 ) Net realized gains (losses) $ (35,725 ) $ 54,144 $ 47,623 $ 73,841 _________________________________________________ (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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Fixed maturities: Mortgage backed securities $ (326 ) $ — $ (1,398 ) $ — Corporate bonds (10 ) (664 ) (1,986 ) (664 ) Asset backed securities — (5 ) — (11 ) Total (336 ) (669 ) (3,384 ) (675 ) Short-term investments — — (2,341 ) — Equity securities (124 ) (278 ) (253 ) (278 ) Other investments (653 ) (13,802 ) (934 ) (16,767 ) Net impairment losses recognized in earnings $ (1,113 ) $ (14,749 ) $ (6,912 ) $ (17,720 ) A description of the methodology and significant inputs used to measure the amount of net impairment losses recognized in earnings 2015 second quarter is as follows: • Other investments — the Company utilized information received from fund managers and positive and negative evidence, including the business prospects, recent events, industry and market data and other factors. Net impairment losses for the 2015 second quarter related to a reduction in the carrying value of one fund investment; • Mortgage backed securities — the Company utilized underlying data provided by asset managers, cash flow projections and additional information from credit agencies in order to determine an expected recovery value for each security. The analysis includes expected cash flow projections under base case and stress case scenarios which modify the expected default expectations and loss severities and slow down prepayment assumptions. The significant inputs in the models include the expected default rates, delinquency rates and foreclosure costs. Net impairment losses for the 2015 second quarter primarily resulted from small adjustments in a number of holdings. The amortized cost basis of the mortgage backed securities 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 $4.3 million of OTTI included in accumulated other comprehensive income at June 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 June 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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Balance at start of period $ 24,344 $ 47,256 $ 20,196 $ 60,062 Credit loss impairments recognized on securities not previously impaired 281 — 4,770 — Credit loss impairments recognized on securities previously impaired 55 5 134 11 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 (3,774 ) (25,820 ) (4,194 ) (38,632 ) Balance at end of period $ 20,906 $ 21,441 $ 20,906 $ 21,441 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: June 30, December 31, Assets used for collateral or guarantees: Affiliated transactions $ 3,651,244 $ 4,138,527 Third party agreements 1,040,156 970,120 Deposits with U.S. regulatory authorities 406,777 337,981 Trust funds 60,864 72,461 Total restricted assets $ 5,159,041 $ 5,519,089

Fair Value

Fair Value	6 Months Ended
	Jun. 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 June 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 $14.97 billion of financial assets and liabilities measured at fair value at June 30, 2015 , approximately $301.7 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 liability . The contingent consideration liability (included in ‘other liabilities’ in the consolidated balance sheets) resulted from the acquisition of CMG Mortgage Insurance Company and its affiliated mortgage insurance companies and is remeasured at fair value at each balance sheet date. Changes in fair value are recognized in ‘net realized gains (losses).’ To determine the fair value of the contingent consideration liability, 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 the contingent consideration liability would be included within Level 3. The following table presents the Company’s financial assets and liabilities measured at fair value by level at June 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 $ 2,833,849 $ — $ 2,833,849 $ — Mortgage backed securities 837,680 — 837,680 — Municipal bonds 1,760,384 — 1,760,384 — Commercial mortgage backed securities 832,159 — 832,159 — U.S. government and government agencies 1,899,868 1,878,893 20,975 — Non-U.S. government securities 786,276 — 786,276 — Asset backed securities 1,351,356 — 1,293,856 57,500 Total 10,301,572 1,878,893 8,365,179 57,500 Equity securities 701,623 698,078 3,545 — Short-term investments 875,727 870,738 4,989 — Other investments 89,611 89,611 — — Other investments measured at net asset value (2) 288,066 Total other investments 377,677 89,611 — — Derivative instruments (3) 20,142 — 20,142 — Fair value option: Corporate bonds 682,569 — 682,569 — Non-U.S. government bonds 89,168 — 89,168 — Mortgage backed securities 58,565 — 58,565 — Asset backed securities 23,868 — 23,868 — Short-term investments 167,698 167,698 — — Equity securities 248 248 — — Other investments 1,158,567 96,871 1,061,696 — Other investments measured at net asset value (2) 432,804 Total 2,613,487 264,817 1,915,866 — Total assets measured at fair value $ 14,890,228 $ 3,802,137 $ 10,309,721 $ 57,500 Liabilities measured at fair value: Contingent consideration liability $ (71,256 ) $ — $ — $ (71,256 ) Derivative instruments (3) (11,731 ) — (11,731 ) — Total liabilities measured at fair value $ (82,987 ) $ — $ (11,731 ) $ (71,256 ) _________________________________________________ (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 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 — Equity securities — — — — 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 liability $ (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 Liability Three Months Ended June 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (66,461 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (4,795 ) 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 $ (71,256 ) Three Months Ended June 30, 2014 Balance at beginning of period $ — $ — $ — $ — $ — $ (43,156 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (9,943 ) 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 $ — $ — $ — $ — $ — $ (53,099 ) Six Months Ended June 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (61,845 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (8,343 ) 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 $ (71,256 ) Six Months Ended June 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) — — — — — (11,337 ) 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 $ — $ — $ — $ — $ — $ (53,099 ) _________________________________________________ (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 the contingent consideration liability 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 June 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 June 30, 2015 , the senior notes of ACGL were carried at their cost, net of debt issuance costs, of $296.8 million and had a fair value of $382.5 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 $514.2 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	6 Months Ended
	Jun. 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 June 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) June 30, 2015 Futures contracts (2) $ 192 $ (1,064 ) $ (872 ) $ 1,683,928 Foreign currency forward contracts (2) 14,452 (7,403 ) 7,049 1,180,054 TBAs (3) 203,522 (158,718 ) 44,804 344,758 Other (2) 5,498 (3,264 ) 2,234 1,624,187 Total $ 223,664 $ (170,449 ) $ 53,215 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 June 30, 2015 , asset derivatives and liability derivatives of $204.3 million and $159.0 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 Six Months Ended Derivatives not designated as June 30, June 30, hedging instruments: 2015 2014 2015 2014 Net realized gains (losses): Futures contracts $ (31,446 ) $ 15,185 $ (12,120 ) $ 5,323 Foreign currency forward contracts (8,724 ) (1,811 ) 8,095 (4,068 ) TBAs (182 ) (270 ) 304 (307 ) Other (1,144 ) (702 ) (1,099 ) (1,314 ) Total $ (41,496 ) $ 12,402 $ (4,820 ) $ (366 )

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Letter of Credit and Revolving Credit Facilities As of June 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 $229.4 million as of June 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 June 30, 2015 , the Company had $456.3 million in outstanding letters of credit under the LOC Facilities, which were secured by investments with a fair value of $521.9 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 June 30, 2015 . As of June 30, 2015 , Watford Re reduced its $200 million letter of credit facility to $100 million and extended the term of the facility an additional year expiring on May 19, 2016 . Watford Re also entered into an $800 million secured credit facility on June 2, 2015 , that provides for borrowings and the issuance of letters of credit not to exceed $400 million . That credit facility expires on June 4, 2018 . At June 30, 2015 , Watford Re had $36.5 million in outstanding letters of credit. Watford Re was in compliance with all covenants contained in both of its credit facilities at June 30, 2015 . 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 $1.12 billion at June 30, 2015 , compared to $968.9 million at December 31, 2014 .

Share Transactions

Share Transactions	6 Months Ended
	Jun. 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 124.0 million common shares for an aggregate purchase price of $3.60 billion . During the 2015 second quarter and six months ended June 30, 2015 , ACGL repurchased 3.2 million and 5.9 million common shares, respectively, for an aggregate purchase price of $199.0 million and $361.9 million , respectively. During the 2014 second quarter and six months ended June 30, 2014 , ACGL did not repurchase any common shares. At June 30, 2015 , $525.3 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. Share-Based Compensation During the 2015 second quarter , the Company made a stock grant of 534,267 stock appreciation rights and stock options and 559,332 restricted shares and units to certain employees and directors with weighted average grant-date fair values of $16.09 and $62.51 , respectively. During the 2014 second quarter , the Company made a stock grant of 551,836 stock appreciation rights and stock options and 571,108 restricted shares and units to certain employees and directors with weighted average grant-date fair values of $15.23 and $57.25 , respectively. The stock appreciation rights and stock options were valued at the grant date using the Black-Scholes option pricing model. Such values are being amortized over the respective substantive vesting period. For awards granted to retirement-eligible employees where no service is required for the employee to retain the award, the grant date fair value is immediately recognized as compensation expense at the grant date because the employee is able to retain the award without continuing to provide service. For employees near retirement eligibility, attribution of compensation cost is over the period from the grant date to the retirement eligibility date. 2015 Long Term Incentive and Share Award Plan (the “2015 Plan”) The 2015 Plan became effective as of May 13, 2015 following approval by shareholders of the Company. The 2015 Plan is intended to provide for competitive compensation opportunities, to encourage long-term service, to recognize individual contributions and reward achievement of performance goals and to promote the creation of long-term value for shareholders by aligning the interests of such persons with those of shareholders. The 2015 Plan provides for the grant to eligible employees and directors stock options, stock appreciation rights, restricted shares, restricted share units payable in common shares or cash, share awards in lieu of cash awards, dividend equivalents and other share-based awards. The 2015 Plan will terminate as to future awards on February 26, 2025. The number of common shares reserved for grants of awards under the 2015 Plan, subject to anti-dilution adjustments in the event of certain changes in the Company’s capital structure, is 4,300,000 . In addition, no more than 50% of such common shares may be issued in connection with full value awards ( i.e. , awards other than stock options or stock appreciation rights) and no more than 2,000,000 common shares may be issued as incentive stock options under Section 422 of the Internal Revenue Code of 1986, as amended. At June 30, 2015 , 3,235,680 shares are available for grant under the 2015 Plan.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 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 4.3% for the six months ended June 30, 2015 , compared to an expense of 2.7% 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 $143.9 million at June 30, 2015 , compared to $131.0 million at December 31, 2014 . In addition, the Company paid $26.0 million in income taxes for the six months ended June 30, 2015 , while the Company paid $8.3 million for the 2014 period.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	6 Months Ended
	Jun. 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 Six Months Ended Details About Line Item That Includes June 30, June 30, AOCI Components Reclassification 2015 2014 2015 2014 Unrealized appreciation on available-for-sale investments Net realized gains (losses) $ 23,259 $ 23,735 $ 65,690 $ 49,773 Other-than-temporary impairment losses (1,126 ) (14,749 ) (8,373 ) (17,720 ) Total before tax 22,133 8,986 57,317 32,053 Income tax (expense) benefit (919 ) (701 ) (5,171 ) (2,519 ) Net of tax $ 21,214 $ 8,285 $ 52,146 $ 29,534 Before Tax Amount Tax Expense (Benefit) Net of Tax Amount Three Months Ended June 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (96,629 ) $ (14,694 ) $ (81,935 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (13 ) — (13 ) Less reclassification of net realized gains (losses) included in net income 22,133 919 21,214 Foreign currency translation adjustments 11,697 117 11,580 Other comprehensive income (loss) $ (107,078 ) $ (15,496 ) $ (91,582 ) Three Months Ended June 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ 115,150 $ 6,722 $ 108,428 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 8,986 701 8,285 Foreign currency translation adjustments 10,021 — 10,021 Other comprehensive income (loss) $ 116,185 $ 6,021 $ 110,164 Six Months Ended June 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (2,242 ) $ (4,611 ) $ 2,369 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (1,461 ) — (1,461 ) Less reclassification of net realized gains (losses) included in net income 57,317 5,171 52,146 Foreign currency translation adjustments (11,929 ) (752 ) (11,177 ) Other comprehensive income (loss) $ (72,949 ) $ (10,534 ) $ (62,415 ) Six Months Ended June 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ 190,550 $ 10,769 $ 179,781 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 32,053 2,519 29,534 Foreign currency translation adjustments 8,672 — 8,672 Other comprehensive income (loss) $ 167,169 $ 8,250 $ 158,919

Guarantor Financial Information

Guarantor Financial Information	6 Months Ended
	Jun. 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. June 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 $ 471 $ 55,047 $ 15,306,122 $ (14,700 ) $ 15,346,940 Cash 10,864 6,928 507,282 — 525,074 Investments in subsidiaries 6,530,452 1,688,419 — (8,218,871 ) — Due from subsidiaries and affiliates 11 47,798 417,231 (465,040 ) — Premiums receivable — — 1,620,756 (439,120 ) 1,181,636 Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses — — 5,741,646 (3,910,419 ) 1,831,227 Contractholder receivables — — 1,393,138 — 1,393,138 Prepaid reinsurance premiums — — 1,595,550 (1,153,409 ) 442,141 Deferred acquisition costs, net — — 448,647 — 448,647 Other assets 4,208 46,157 2,274,796 (409,039 ) 1,916,122 Total assets $ 6,546,006 $ 1,844,349 $ 29,305,168 $ (14,610,598 ) $ 23,084,925 Liabilities Reserve for losses and loss adjustment expenses $ — $ — $ 12,970,720 $ (3,888,439 ) $ 9,082,281 Unearned premiums — — 3,596,332 (1,153,409 ) 2,442,923 Reinsurance balances payable — — 678,216 (425,754 ) 252,462 Contractholder payables — — 1,393,138 — 1,393,138 Deposit accounting liabilities — — 495,121 (217,598 ) 277,523 Senior notes 296,834 494,388 — — 791,222 Revolving credit agreement borrowings 100,000 — — — 100,000 Due to subsidiaries and affiliates 402 35,000 429,638 (465,040 ) — Other liabilities 11,255 44,917 1,778,600 (226,787 ) 1,607,985 Total liabilities 408,491 574,305 21,341,765 (6,377,027 ) 15,947,534 Redeemable noncontrolling interests — — 219,696 (14,700 ) 204,996 Shareholders’ Equity Total shareholders’ equity available to Arch 6,137,515 1,270,044 6,948,827 (8,218,871 ) 6,137,515 Non-redeemable noncontrolling interests — — 794,880 — 794,880 Total shareholders’ equity 6,137,515 1,270,044 7,743,707 (8,218,871 ) 6,932,395 Total liabilities, noncontrolling interests and shareholders’ equity $ 6,546,006 $ 1,844,349 $ 29,305,168 $ (14,610,598 ) $ 23,084,925 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 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 1,000,138 (194,298 ) 872,380 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 June 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 $ — $ — $ 943,438 $ — $ 943,438 Net investment income — 800 87,154 (991 ) 86,963 Net realized gains (losses) — 1 (35,726 ) — (35,725 ) Net impairment losses recognized in earnings — — (1,113 ) — (1,113 ) Other underwriting income — — 7,717 — 7,717 Equity in net income of investment funds accounted for using the equity method — — 16,167 — 16,167 Other income (loss) — — 2,205 — 2,205 Total revenues — 801 1,019,842 (991 ) 1,019,652 Expenses Losses and loss adjustment expenses — — 519,426 — 519,426 Acquisition expenses — — 175,425 — 175,425 Other operating expenses 16,900 1,012 150,696 — 168,608 Interest expense 5,862 6,769 (7,793 ) (827 ) 4,011 Net foreign exchange losses (gains) — — 6,942 12,641 19,583 Total expenses 22,762 7,781 844,696 11,814 887,053 Income (loss) before income taxes (22,762 ) (6,980 ) 175,146 (12,805 ) 132,599 Income tax (expense) benefit — 3,697 (10,477 ) — (6,780 ) Income (loss) before equity in net income of subsidiaries (22,762 ) (3,283 ) 164,669 (12,805 ) 125,819 Equity in net income of subsidiaries 138,552 14,077 — (152,629 ) — Net income 115,790 10,794 164,669 (165,434 ) 125,819 Amounts attributable to noncontrolling interests — — (10,193 ) 164 (10,029 ) Net income available to Arch 115,790 10,794 154,476 (165,270 ) 115,790 Preferred dividends (5,485 ) — — — (5,485 ) Net income available to Arch common shareholders $ 110,305 $ 10,794 $ 154,476 $ (165,270 ) $ 110,305 Comprehensive income (loss) available to Arch $ 24,208 $ (13,505 ) $ 50,249 $ (36,744 ) $ 24,208 Three Months Ended June 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 $ — $ — $ 907,152 $ — $ 907,152 Net investment income — — 80,380 (7,390 ) 72,990 Net realized gains (losses) — — 54,144 — 54,144 Net impairment losses recognized in earnings — — (14,749 ) — (14,749 ) Other underwriting income — — 2,033 — 2,033 Equity in net income of investment funds accounted for using the equity method — — 9,240 — 9,240 Other income (loss) — — 4,850 — 4,850 Total revenues — — 1,043,050 (7,390 ) 1,035,660 Expenses Losses and loss adjustment expenses — — 485,518 — 485,518 Acquisition expenses — — 158,158 — 158,158 Other operating expenses 15,250 494 140,606 — 156,350 Interest expense 5,854 6,448 9,422 (7,390 ) 14,334 Net foreign exchange losses (gains) — — 1,054 1,240 2,294 Total expenses 21,104 6,942 794,758 (6,150 ) 816,654 Income (loss) before income taxes (21,104 ) (6,942 ) 248,292 (1,240 ) 219,006 Income tax (expense) benefit — 3,294 (10,583 ) — (7,289 ) Income (loss) before equity in net income of subsidiaries (21,104 ) (3,648 ) 237,709 (1,240 ) 211,717 Equity in net income of subsidiaries 229,120 9,334 — (238,454 ) — Net income 208,016 5,686 237,709 (239,694 ) 211,717 Amounts attributable to noncontrolling interests — — (3,701 ) — (3,701 ) Net income available to Arch 208,016 5,686 234,008 (239,694 ) 208,016 Preferred dividends (5,485 ) — — — (5,485 ) Net income available to Arch common shareholders $ 202,531 $ 5,686 $ 234,008 $ (239,694 ) $ 202,531 Comprehensive income (loss) available to Arch $ 318,180 $ 23,186 $ 335,348 $ (358,534 ) $ 318,180 Six Months Ended June 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 $ — $ — $ 1,853,702 $ — $ 1,853,702 Net investment income — 805 173,164 (8,012 ) 165,957 Net realized gains (losses) — 1 47,622 — 47,623 Net impairment losses recognized in earnings — — (6,912 ) — (6,912 ) Other underwriting income — — 19,253 — 19,253 Equity in net income of investment funds accounted for using the equity method — — 22,056 — 22,056 Other income (loss) — — 317 — 317 Total revenues — 806 2,109,202 (8,012 ) 2,101,996 Expenses Losses and loss adjustment expenses — — 1,013,142 — 1,013,142 Acquisition expenses — — 338,501 — 338,501 Other operating expenses 25,532 2,271 298,687 — 326,490 Interest expense 11,718 13,135 (258 ) (7,848 ) 16,747 Net foreign exchange losses (gains) — — (32,688 ) (14,230 ) (46,918 ) Total expenses 37,250 15,406 1,617,384 (22,078 ) 1,647,962 Income (loss) before income taxes (37,250 ) (14,600 ) 491,818 14,066 454,034 Income tax (expense) benefit — 5,110 (24,568 ) — (19,458 ) Income (loss) before equity in net income of subsidiaries (37,250 ) (9,490 ) 467,250 14,066 434,576 Equity in net income of subsidiaries 436,376 28,572 — (464,948 ) — Net income 399,126 19,082 467,250 (450,882 ) 434,576 Amounts attributable to noncontrolling interests — — (35,614 ) 164 (35,450 ) Net income available to Arch 399,126 19,082 431,636 (450,718 ) 399,126 Preferred dividends (10,969 ) — — — (10,969 ) Net income available to Arch common shareholders $ 388,157 $ 19,082 $ 431,636 $ (450,718 ) $ 388,157 Comprehensive income (loss) available to Arch $ 336,711 $ (1,755 ) $ 383,442 $ (381,687 ) $ 336,711 Six Months Ended June 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 $ — $ — $ 1,766,932 $ — $ 1,766,932 Net investment income — — 157,381 (17,397 ) 139,984 Net realized gains (losses) — — 73,841 — 73,841 Net impairment losses recognized in earnings — — (17,720 ) — (17,720 ) Other underwriting income — — 3,615 — 3,615 Equity in net income of investment funds accounted for using the equity method — — 12,493 — 12,493 Other income (loss) — — 2,746 — 2,746 Total revenues — — 1,999,288 (17,397 ) 1,981,891 Expenses Losses and loss adjustment expenses — — 921,758 — 921,758 Acquisition expenses — — 318,500 — 318,500 Other operating expenses 25,557 1,471 275,121 — 302,149 Interest expense 11,707 12,962 21,466 (17,397 ) 28,738 Net foreign exchange losses (gains) — — 6,795 2,062 8,857 Total expenses 37,264 14,433 1,543,640 (15,335 ) 1,580,002 Income (loss) before income taxes (37,264 ) (14,433 ) 455,648 (2,062 ) 401,889 Income tax (expense) benefit — 6,082 (17,109 ) — (11,027 ) Income (loss) before equity in net income of subsidiaries (37,264 ) (8,351 ) 438,539 (2,062 ) 390,862 Equity in net income of subsidiaries 427,780 31,486 — (459,266 ) — Net income 390,516 23,135 438,539 (461,328 ) 390,862 Amounts attributable to noncontrolling interests — — (346 ) — (346 ) Net income available to Arch 390,516 23,135 438,193 (461,328 ) 390,516 Preferred dividends (10,969 ) — — — (10,969 ) Net income available to Arch common shareholders $ 379,547 $ 23,135 $ 438,193 $ (461,328 ) $ 379,547 Comprehensive income (loss) available to Arch $ 549,435 $ 40,406 $ 587,467 $ (627,873 ) $ 549,435 Six Months Ended June 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 $ 378,703 $ 8,282 $ 433,833 $ (435,619 ) $ 385,199 Investing Activities Purchases of fixed maturity investments — — (14,641,391 ) — (14,641,391 ) Purchases of equity securities — — (288,535 ) — (288,535 ) Purchases of other investments — — (1,273,780 ) — (1,273,780 ) Proceeds from the sales of fixed maturity investments — 20,002 14,335,517 — 14,355,519 Proceeds from the sales of equity securities — — 272,343 — 272,343 Proceeds from the sales, redemptions and maturities of other investments — — 1,078,675 — 1,078,675 Proceeds from redemptions and maturities of fixed maturity investments — — 474,984 — 474,984 Proceeds from investment in joint venture — — 40,000 — 40,000 Net purchases (sales) of short-term investments (365 ) (12,171 ) 16,243 — 3,707 Change in cash collateral related to securities lending — — (18,329 ) — (18,329 ) Contributions to subsidiaries — — (9,290 ) 9,290 — Intercompany loans issued — (39,500 ) (27,500 ) 67,000 — Purchase of business, net of cash acquired — — 818 — 818 Purchases of furniture, equipment and other assets (24 ) — (43,141 ) — (43,165 ) Net Cash Provided By (Used For) Investing Activities (389 ) (31,669 ) (83,386 ) 76,290 (39,154 ) Financing Activities Purchases of common shares under share repurchase program (361,877 ) — — — (361,877 ) Proceeds from common shares issued, net 2,178 — 9,290 (9,290 ) 2,178 Proceeds from intercompany borrowings — 27,500 39,500 (67,000 ) — Change in cash collateral related to securities lending — — 18,329 — 18,329 Dividends paid to redeemable noncontrolling interests — — (9,632 ) 319 (9,313 ) Dividends paid to parent — — (435,300 ) 435,300 — Other — 28 54,990 — 55,018 Preferred dividends paid (10,969 ) — — — (10,969 ) Net Cash Provided By (Used For) Financing Activities (370,668 ) 27,528 (322,823 ) 359,329 (306,634 ) Effects of exchange rates changes on foreign currency cash — — (39 ) — (39 ) Increase (decrease) in cash 7,646 4,141 27,585 — 39,372 Cash beginning of year 3,218 2,787 479,697 — 485,702 Cash end of period $ 10,864 $ 6,928 $ 507,282 $ — $ 525,074 Six Months Ended June 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 $ 10,099 $ 424 $ 474,565 $ (32,025 ) $ 453,063 Investing Activities Purchases of fixed maturity investments — (78,509 ) (14,233,239 ) — (14,311,748 ) Purchases of equity securities — — (174,687 ) — (174,687 ) Purchases of other investments — — (1,022,987 ) — (1,022,987 ) Proceeds from the sales of fixed maturity investments — — 13,204,854 — 13,204,854 Proceeds from the sales of equity securities — — 98,687 — 98,687 Proceeds from the sales of other investments — — 618,707 — 618,707 Proceeds from redemptions and maturities of fixed maturity investments — — 432,040 — 432,040 Net (purchases) sales of short-term investments (31 ) 408,779 21,556 — 430,304 Change in cash collateral related to securities lending — — 18,701 — 18,701 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 furniture, equipment and other assets (128 ) — (10,232 ) — (10,360 ) Net Cash Provided By (Used For) Investing Activities (159 ) 17,063 (1,371,928 ) 402,957 (952,067 ) Financing Activities Proceeds from common shares issued, net 2,521 — 413,207 (413,207 ) 2,521 Repayments of intercompany borrowings — (10,250 ) — 10,250 — Change in cash collateral related to securities lending — — (18,701 ) — (18,701 ) 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 — — (4,816 ) — (4,816 ) Dividends paid to parent — — (32,025 ) 32,025 — Other — — 4,706 — 4,706 Preferred dividends paid (10,969 ) — — — (10,969 ) Net Cash Provided By (Used For) Financing Activities (8,448 ) (10,250 ) 1,378,507 (370,932 ) 988,877 Effects of exchange rates changes on foreign currency cash — — 2,513 — 2,513 Increase in cash 1,492 7,237 483,657 — 492,386 Cash beginning of year 3,223 509 430,325 — 434,057 Cash end of period $ 4,715 $ 7,746 $ 913,982 $ — $ 926,443

Legal Proceedings

Legal Proceedings	6 Months Ended
	Jun. 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 June 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 (Notes)	6 Months Ended
	Jun. 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’s investment portfolio includes investments in funds managed by Carlyle. As of June 30, 2015 , the Company had aggregate commitments of $670.9 million to funds managed by Carlyle, of which $374.1 million was unfunded. The Company may make additional commitments to funds managed by Carlyle from time to time. During the six months ended June 30, 2015 and 2014 , the Company made aggregate capital contributions to funds managed by Carlyle of $25.6 million and $29.8 million , respectively, and received aggregate cash distributions from funds managed by Carlyle of $19.8 million and $37.2 million , respectively.

General (Policies)

General (Policies)	6 Months Ended
	Jun. 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)	6 Months Ended
	Jun. 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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Balance, beginning of period $ 789,594 $ 793,496 $ 769,081 $ — Sale of shares to noncontrolling interests — — — 796,903 Amounts attributable to noncontrolling interests 5,286 (1,156 ) 25,799 (4,563 ) Balance, end of period $ 794,880 $ 792,340 $ 794,880 $ 792,340
Activity in redeemable noncontrolling interests	The following table sets forth activity in the redeemable non-controlling interests: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Balance, beginning of period $ 219,604 $ 219,234 $ 219,512 $ — Sale of shares to noncontrolling interests — — — 219,233 Shares acquired by the Company (1) (14,700 ) — (14,700 ) — Accretion of preference share issuance costs 92 92 184 93 Balance, end of period $ 204,996 $ 219,326 $ 204,996 $ 219,326 _________________________________________________ (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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Amounts attributable to non-redeemable noncontrolling interests $ (5,286 ) $ 1,156 $ (25,799 ) $ 4,563 Dividends attributable to redeemable noncontrolling interests (4,743 ) (4,857 ) (9,651 ) (4,909 ) Amounts attributable to noncontrolling interests $ (10,029 ) $ (3,701 ) $ (35,450 ) $ (346 )

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	6 Months Ended
	Jun. 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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Numerator: Net income $ 125,819 $ 211,717 $ 434,576 $ 390,862 Amounts attributable to noncontrolling interests (10,029 ) (3,701 ) (35,450 ) (346 ) Net income available to Arch 115,790 208,016 399,126 390,516 Preferred dividends (5,485 ) (5,485 ) (10,969 ) (10,969 ) Net income available to Arch common shareholders $ 110,305 $ 202,531 $ 388,157 $ 379,547 Denominator: Weighted average common shares outstanding — basic 121,719,214 132,650,634 122,957,384 132,256,462 Effect of dilutive common share equivalents: Nonvested restricted shares 1,258,741 1,144,621 1,334,633 1,236,408 Stock options (1) 2,907,465 3,094,689 2,864,696 3,224,019 Weighted average common shares and common share equivalents outstanding — diluted 125,885,420 136,889,944 127,156,713 136,716,889 Earnings per common share: Basic $ 0.91 $ 1.53 $ 3.16 $ 2.87 Diluted $ 0.88 $ 1.48 $ 3.05 $ 2.78 _________________________________________________ (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 second quarter and 2014 second quarter , the number of stock options excluded were 1,009,113 and 978,237 , respectively. For the six months ended June 30, 2015 and 2014 , the number of stock options excluded were 1,187,162 and 1,318,662 , respectively.

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2015
Segment Reporting [Abstract]
Analysis of underwriting income 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 June 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 744,810 $ 342,101 $ 68,572 $ 1,155,253 $ 127,954 $ 1,199,209 Premiums ceded (235,743 ) (89,446 ) (6,902 ) (331,861 ) (7,766 ) (255,629 ) Net premiums written 509,067 252,655 61,670 823,392 120,188 943,580 Change in unearned premiums 758 21,310 (9,211 ) 12,857 (12,999 ) (142 ) Net premiums earned 509,825 273,965 52,459 836,249 107,189 943,438 Other underwriting income 521 2,658 3,686 6,865 852 7,717 Losses and loss adjustment expenses (320,926 ) (111,183 ) (9,639 ) (441,748 ) (77,678 ) (519,426 ) Acquisition expenses, net (76,723 ) (58,360 ) (10,200 ) (145,283 ) (30,142 ) (175,425 ) Other operating expenses (89,054 ) (39,007 ) (19,679 ) (147,740 ) (3,450 ) (151,190 ) Underwriting income (loss) $ 23,643 $ 68,073 $ 16,627 108,343 (3,229 ) 105,114 Net investment income 67,171 19,792 86,963 Net realized gains (losses) (26,860 ) (8,865 ) (35,725 ) Net impairment losses recognized in earnings (1,113 ) — (1,113 ) Equity in net income of investment funds accounted for using the equity method 16,167 — 16,167 Other income (loss) 2,205 — 2,205 Other expenses (17,418 ) — (17,418 ) Interest expense (4,011 ) — (4,011 ) Net foreign exchange gains (losses) (22,571 ) 2,988 (19,583 ) Income (loss) before income taxes 121,913 10,686 132,599 Income tax expense (6,780 ) — (6,780 ) Net income (loss) 115,133 10,686 125,819 Dividends attributable to redeemable noncontrolling interests — (4,743 ) (4,743 ) Amounts attributable to noncontrolling interests — (5,286 ) (5,286 ) Net income (loss) available to Arch 115,133 657 115,790 Preferred dividends (5,485 ) — (5,485 ) Net income (loss) available to Arch common shareholders $ 109,648 $ 657 $ 110,305 Underwriting Ratios Loss ratio 62.9 % 40.6 % 18.4 % 52.8 % 72.5 % 55.1 % Acquisition expense ratio 15.0 % 21.3 % 19.4 % 17.4 % 28.1 % 18.6 % Other operating expense ratio 17.5 % 14.2 % 37.5 % 17.7 % 3.2 % 16.0 % Combined ratio 95.4 % 76.1 % 75.3 % 87.9 % 103.8 % 89.7 % Goodwill and intangible assets $ 30,968 $ 2,420 $ 69,130 $ 102,518 $ — $ 102,518 Total investable assets $ 14,513,554 $ 1,340,574 $ 15,854,128 Total assets 21,323,611 1,761,314 23,084,925 Total liabilities 15,299,256 648,278 15,947,534 _________________________________________________ (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 June 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 852,231 $ 349,841 $ 55,476 $ 1,256,934 $ 54,562 $ 1,271,761 Premiums ceded (273,349 ) (58,994 ) (5,079 ) (336,808 ) (2,760 ) (299,833 ) Net premiums written 578,882 290,847 50,397 920,126 51,802 971,928 Change in unearned premiums (71,170 ) 44,780 436 (25,954 ) (38,822 ) (64,776 ) Net premiums earned 507,712 335,627 50,833 894,172 12,980 907,152 Other underwriting income 514 303 1,216 2,033 — 2,033 Losses and loss adjustment expenses (311,526 ) (150,325 ) (15,473 ) (477,324 ) (8,194 ) (485,518 ) Acquisition expenses, net (76,449 ) (66,035 ) (11,481 ) (153,965 ) (4,193 ) (158,158 ) Other operating expenses (85,829 ) (37,666 ) (16,288 ) (139,783 ) (1,635 ) (141,418 ) Underwriting income (loss) $ 34,422 $ 81,904 $ 8,807 125,133 (1,042 ) 124,091 Net investment income 72,458 532 72,990 Net realized gains (losses) 50,966 3,178 54,144 Net impairment losses recognized in earnings (14,749 ) — (14,749 ) Equity in net income of investment funds accounted for using the equity method 9,240 — 9,240 Other income (loss) 4,850 — 4,850 Other expenses (15,279 ) 347 (14,932 ) Interest expense (14,334 ) — (14,334 ) Net foreign exchange gains (losses) (2,764 ) 470 (2,294 ) Income (loss) before income taxes 215,521 3,485 219,006 Income tax expense (7,289 ) — (7,289 ) Net income (loss) 208,232 3,485 211,717 Dividends attributable to redeemable noncontrolling interests — (4,857 ) (4,857 ) Amounts attributable to noncontrolling interests — 1,156 1,156 Net income (loss) available to Arch 208,232 (216 ) 208,016 Preferred dividends (5,485 ) — (5,485 ) Net income (loss) available to Arch common shareholders $ 202,747 $ (216 ) $ 202,531 Underwriting Ratios Loss ratio 61.4 % 44.8 % 30.4 % 53.4 % 63.1 % 53.5 % Acquisition expense ratio 15.1 % 19.7 % 22.6 % 17.2 % 32.3 % 17.4 % Other operating expense ratio 16.9 % 11.2 % 32.0 % 15.6 % 12.6 % 15.6 % Combined ratio 93.4 % 75.7 % 85.0 % 86.2 % 108.0 % 86.5 % Goodwill and intangible assets $ 24,498 $ 4,942 $ 89,281 $ 118,721 $ — $ 118,721 Total investable assets $ 14,688,808 $ 1,114,719 $ 15,803,527 Total assets 21,204,129 1,363,318 22,567,447 Total liabilities 15,072,875 253,507 15,326,382 _________________________________________________ (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. Six Months Ended June 30, 2015 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 1,510,963 $ 827,213 $ 129,113 $ 2,466,931 $ 256,587 $ 2,541,231 Premiums ceded (459,893 ) (226,015 ) (15,572 ) (701,122 ) (11,821 ) (530,656 ) Net premiums written 1,051,070 601,198 113,541 1,765,809 244,766 2,010,575 Change in unearned premiums (33,331 ) (47,516 ) (10,715 ) (91,562 ) (65,311 ) (156,873 ) Net premiums earned 1,017,739 553,682 102,826 1,674,247 179,455 1,853,702 Other underwriting income 948 4,087 11,404 16,439 2,814 19,253 Losses and loss adjustment expenses (638,822 ) (223,715 ) (23,448 ) (885,985 ) (127,157 ) (1,013,142 ) Acquisition expenses, net (151,801 ) (114,964 ) (20,618 ) (287,383 ) (51,118 ) (338,501 ) Other operating expenses (177,173 ) (77,051 ) (40,048 ) (294,272 ) (5,455 ) (299,727 ) Underwriting income (loss) $ 50,891 $ 142,039 $ 30,116 223,046 (1,461 ) 221,585 Net investment income 137,459 28,498 165,957 Net realized gains (losses) 38,649 8,974 47,623 Net impairment losses recognized in earnings (6,912 ) — (6,912 ) Equity in net income of investment funds accounted for using the equity method 22,056 — 22,056 Other income (loss) 317 — 317 Other expenses (26,763 ) — (26,763 ) Interest expense (16,747 ) — (16,747 ) Net foreign exchange gains (losses) 44,282 2,636 46,918 Income (loss) before income taxes 415,387 38,647 454,034 Income tax expense (19,458 ) — (19,458 ) Net income (loss) 395,929 38,647 434,576 Dividends attributable to redeemable noncontrolling interests — (9,651 ) (9,651 ) Amounts attributable to noncontrolling interests — (25,799 ) (25,799 ) Net income (loss) available to Arch 395,929 3,197 399,126 Preferred dividends (10,969 ) — (10,969 ) Net income (loss) available to Arch common shareholders $ 384,960 $ 3,197 $ 388,157 Underwriting Ratios Loss ratio 62.8 % 40.4 % 22.8 % 52.9 % 70.9 % 54.7 % Acquisition expense ratio 14.9 % 20.8 % 20.1 % 17.2 % 28.5 % 18.3 % Other operating expense ratio 17.4 % 13.9 % 38.9 % 17.6 % 3.0 % 16.2 % Combined ratio 95.1 % 75.1 % 81.8 % 87.7 % 102.4 % 89.2 % _________________________________________________ (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. Six Months Ended June 30, 2014 Insurance Reinsurance Mortgage Sub-Total Other Total Gross premiums written (1) $ 1,582,877 $ 866,894 $ 103,383 $ 2,552,070 $ 86,756 $ 2,566,897 Premiums ceded (458,393 ) (132,121 ) (9,718 ) (599,148 ) (2,760 ) (529,979 ) Net premiums written 1,124,484 734,773 93,665 1,952,922 83,996 2,036,918 Change in unearned premiums (139,271 ) (57,798 ) (4,067 ) (201,136 ) (68,850 ) (269,986 ) Net premiums earned 985,213 676,975 89,598 1,751,786 15,146 1,766,932 Other underwriting income 1,014 619 1,982 3,615 — 3,615 Losses and loss adjustment expenses (598,296 ) (289,961 ) (23,951 ) (912,208 ) (9,550 ) (921,758 ) Acquisition expenses, net (153,381 ) (139,468 ) (20,635 ) (313,484 ) (5,016 ) (318,500 ) Other operating expenses (166,973 ) (73,861 ) (30,164 ) (270,998 ) (2,744 ) (273,742 ) Underwriting income (loss) $ 67,577 $ 174,304 $ 16,830 258,711 (2,164 ) 256,547 Net investment income 139,451 533 139,984 Net realized gains (losses) 70,663 3,178 73,841 Net impairment losses recognized in earnings (17,720 ) — (17,720 ) Equity in net income of investment funds accounted for using the equity method 12,493 — 12,493 Other income (loss) 2,746 — 2,746 Other expenses (26,078 ) (2,329 ) (28,407 ) Interest expense (28,738 ) — (28,738 ) Net foreign exchange gains (losses) (9,420 ) 563 (8,857 ) Income (loss) before income taxes 402,108 (219 ) 401,889 Income tax expense (11,027 ) — (11,027 ) Net income (loss) 391,081 (219 ) 390,862 Dividends attributable to redeemable noncontrolling interests — (4,909 ) (4,909 ) Amounts attributable to noncontrolling interests — 4,563 4,563 Net income (loss) available to Arch 391,081 (565 ) 390,516 Preferred dividends (10,969 ) — (10,969 ) Net income (loss) available to Arch common shareholders $ 380,112 $ (565 ) $ 379,547 Underwriting Ratios Loss ratio 60.7 % 42.8 % 26.7 % 52.1 % 63.1 % 52.2 % Acquisition expense ratio 15.6 % 20.6 % 23.0 % 17.9 % 33.1 % 18.0 % Other operating expense ratio 16.9 % 10.9 % 33.7 % 15.5 % 18.1 % 15.5 % Combined ratio 93.2 % 74.3 % 83.4 % 85.5 % 114.3 % 85.7 % _________________________________________________ (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.

Investment Information (Tables)

Investment Information (Tables)	6 Months Ended
	Jun. 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) June 30, 2015 Fixed maturities (1): Corporate bonds $ 2,833,849 $ 26,401 $ (51,717 ) $ 2,859,165 $ (681 ) Mortgage backed securities 837,680 12,315 (4,231 ) 829,596 (3,564 ) Municipal bonds 1,760,384 19,601 (9,004 ) 1,749,787 — Commercial mortgage backed securities 832,159 6,760 (4,922 ) 830,321 — U.S. government and government agencies 1,899,868 8,463 (3,720 ) 1,895,125 — Non-U.S. government securities 786,276 10,343 (32,720 ) 808,653 — Asset backed securities 1,351,356 7,324 (3,364 ) 1,347,396 (22 ) Total 10,301,572 91,207 (109,678 ) 10,320,043 (4,267 ) Equity securities 701,623 105,174 (18,606 ) 615,055 — Other investments 377,677 46,166 (1,927 ) 333,438 — Short-term investments 875,727 55 (2,767 ) 878,439 — Total $ 12,256,599 $ 242,602 $ (132,978 ) $ 12,146,975 $ (4,267 ) 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 June 30, 2015 , the net unrealized gain related to securities for which a non-credit OTTI was recognized in AOCI was $0.3 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 June 30, 2015 Fixed maturities (1): Corporate bonds $ 1,659,276 $ (40,616 ) $ 92,244 $ (11,101 ) $ 1,751,520 $ (51,717 ) Mortgage backed securities 437,043 (3,574 ) 45,082 (657 ) 482,125 (4,231 ) Municipal bonds 784,691 (8,562 ) 3,530 (442 ) 788,221 (9,004 ) Commercial mortgage backed securities 374,338 (4,912 ) 2,893 (10 ) 377,231 (4,922 ) U.S. government and government agencies 426,224 (3,720 ) — — 426,224 (3,720 ) Non-U.S. government securities 431,360 (16,841 ) 77,314 (15,879 ) 508,674 (32,720 ) Asset backed securities 281,650 (2,161 ) 130,987 (1,203 ) 412,637 (3,364 ) Total 4,394,582 (80,386 ) 352,050 (29,292 ) 4,746,632 (109,678 ) Equity securities 286,325 (18,606 ) — — 286,325 (18,606 ) Other investments 89,863 (1,927 ) — — 89,863 (1,927 ) Short-term investments 60,287 (2,767 ) — — 60,287 (2,767 ) Total $ 4,831,057 $ (103,686 ) $ 352,050 $ (29,292 ) $ 5,183,107 $ (132,978 ) 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. June 30, 2015 December 31, 2014 Maturity Estimated Fair Value Amortized Cost Estimated Amortized Cost Due in one year or less $ 369,356 $ 374,710 $ 235,930 $ 233,794 Due after one year through five years 4,101,484 4,106,002 4,074,562 4,077,408 Due after five years through 10 years 2,468,013 2,487,840 2,475,726 2,461,356 Due after 10 years 341,524 344,178 279,542 273,372 7,280,377 7,312,730 7,065,760 7,045,930 Mortgage backed securities 837,680 829,596 943,343 928,342 Commercial mortgage backed securities 832,159 830,321 1,114,528 1,103,756 Asset backed securities 1,351,356 1,347,396 1,677,941 1,675,605 Total (1) $ 10,301,572 $ 10,320,043 $ 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: June 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 $ 335,233 $ — $ — $ — $ 335,233 Corporate bonds 44,139 — — — 44,139 Equity securities 4,593 — — — 4,593 Total $ 383,965 $ — $ — $ — $ 383,965 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 $ 383,965
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: June 30, December 31, Available for sale: Asian and emerging markets $ 287,666 $ 236,586 Investment grade fixed income 58,829 59,638 Credit related funds 13,773 — Other 17,409 — Total available for sale 377,677 296,224 Fair value option: Term loan investments (par value: $1,077,945 and $1,094,337) 1,061,696 1,073,649 Mezzanine debt funds 115,019 121,341 Credit related funds 138,070 114,436 Investment grade fixed income 60,383 69,108 Asian and emerging markets 26,494 25,800 Other (1) 189,709 137,094 Total fair value option 1,591,371 1,541,428 Total $ 1,969,048 $ 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: June 30, December 31, Fixed maturities $ 854,170 $ 632,024 Other investments 1,591,371 1,541,428 Short-term investments 167,698 251,601 Equity securities 248 — Investments accounted for using the fair value option $ 2,613,487 $ 2,425,053
Components of net investment income	The components of net investment income were derived from the following sources: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Fixed maturities $ 71,275 $ 65,869 $ 139,871 $ 128,318 Term loan investments 18,033 6,908 32,777 12,577 Equity securities (dividends) 2,578 3,271 5,257 6,192 Short-term investments 225 107 421 512 Other (1) 10,489 9,100 23,236 13,819 Gross investment income 102,600 85,255 201,562 161,418 Investment expenses (15,637 ) (12,265 ) (35,605 ) (21,434 ) Net investment income $ 86,963 $ 72,990 $ 165,957 $ 139,984 _________________________________________________ (1) Includes income distributions from investment funds and other items.
Summary of net realized gains (losses)	Net realized gains (losses) were as follows, excluding other-than-temporary impairment provisions: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Available for sale securities: Gross gains on investment sales $ 82,233 $ 56,763 $ 179,824 $ 122,814 Gross losses on investment sales (58,974 ) (33,028 ) (114,134 ) (73,041 ) Change in fair value of assets and liabilities accounted for using the fair value option: Fixed maturities (5,191 ) 10,984 (8,493 ) 9,341 Other investments 785 17,985 7,072 28,761 Equity securities (69 ) — (71 ) — Short-term investments (4,375 ) — 1,471 — Derivative instruments (1) (41,496 ) 12,402 (4,820 ) (366 ) Other (2) (8,638 ) (10,962 ) (13,226 ) (13,668 ) Net realized gains (losses) $ (35,725 ) $ 54,144 $ 47,623 $ 73,841 _________________________________________________ (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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Fixed maturities: Mortgage backed securities $ (326 ) $ — $ (1,398 ) $ — Corporate bonds (10 ) (664 ) (1,986 ) (664 ) Asset backed securities — (5 ) — (11 ) Total (336 ) (669 ) (3,384 ) (675 ) Short-term investments — — (2,341 ) — Equity securities (124 ) (278 ) (253 ) (278 ) Other investments (653 ) (13,802 ) (934 ) (16,767 ) Net impairment losses recognized in earnings $ (1,113 ) $ (14,749 ) $ (6,912 ) $ (17,720 )
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 Six Months Ended June 30, June 30, 2015 2014 2015 2014 Balance at start of period $ 24,344 $ 47,256 $ 20,196 $ 60,062 Credit loss impairments recognized on securities not previously impaired 281 — 4,770 — Credit loss impairments recognized on securities previously impaired 55 5 134 11 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 (3,774 ) (25,820 ) (4,194 ) (38,632 ) Balance at end of period $ 20,906 $ 21,441 $ 20,906 $ 21,441
Summary of restricted assets	The following table details the value of the Company’s restricted assets: June 30, December 31, Assets used for collateral or guarantees: Affiliated transactions $ 3,651,244 $ 4,138,527 Third party agreements 1,040,156 970,120 Deposits with U.S. regulatory authorities 406,777 337,981 Trust funds 60,864 72,461 Total restricted assets $ 5,159,041 $ 5,519,089

Fair Value (Tables)

Fair Value (Tables)	6 Months Ended
	Jun. 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 June 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 $ 2,833,849 $ — $ 2,833,849 $ — Mortgage backed securities 837,680 — 837,680 — Municipal bonds 1,760,384 — 1,760,384 — Commercial mortgage backed securities 832,159 — 832,159 — U.S. government and government agencies 1,899,868 1,878,893 20,975 — Non-U.S. government securities 786,276 — 786,276 — Asset backed securities 1,351,356 — 1,293,856 57,500 Total 10,301,572 1,878,893 8,365,179 57,500 Equity securities 701,623 698,078 3,545 — Short-term investments 875,727 870,738 4,989 — Other investments 89,611 89,611 — — Other investments measured at net asset value (2) 288,066 Total other investments 377,677 89,611 — — Derivative instruments (3) 20,142 — 20,142 — Fair value option: Corporate bonds 682,569 — 682,569 — Non-U.S. government bonds 89,168 — 89,168 — Mortgage backed securities 58,565 — 58,565 — Asset backed securities 23,868 — 23,868 — Short-term investments 167,698 167,698 — — Equity securities 248 248 — — Other investments 1,158,567 96,871 1,061,696 — Other investments measured at net asset value (2) 432,804 Total 2,613,487 264,817 1,915,866 — Total assets measured at fair value $ 14,890,228 $ 3,802,137 $ 10,309,721 $ 57,500 Liabilities measured at fair value: Contingent consideration liability $ (71,256 ) $ — $ — $ (71,256 ) Derivative instruments (3) (11,731 ) — (11,731 ) — Total liabilities measured at fair value $ (82,987 ) $ — $ (11,731 ) $ (71,256 ) _________________________________________________ (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 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 — Equity securities — — — — 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 liability $ (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 Liability Three Months Ended June 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (66,461 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (4,795 ) 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 $ (71,256 ) Three Months Ended June 30, 2014 Balance at beginning of period $ — $ — $ — $ — $ — $ (43,156 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (9,943 ) 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 $ — $ — $ — $ — $ — $ (53,099 ) Six Months Ended June 30, 2015 Balance at beginning of period $ 57,500 $ — $ — $ — $ 57,500 $ (61,845 ) Total gains or (losses) (realized/unrealized) Included in earnings (1) — — — — — (8,343 ) 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 $ (71,256 ) Six Months Ended June 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) — — — — — (11,337 ) 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 $ — $ — $ — $ — $ — $ (53,099 ) _________________________________________________ (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 the contingent consideration liability 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)	6 Months Ended
	Jun. 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) June 30, 2015 Futures contracts (2) $ 192 $ (1,064 ) $ (872 ) $ 1,683,928 Foreign currency forward contracts (2) 14,452 (7,403 ) 7,049 1,180,054 TBAs (3) 203,522 (158,718 ) 44,804 344,758 Other (2) 5,498 (3,264 ) 2,234 1,624,187 Total $ 223,664 $ (170,449 ) $ 53,215 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 Six Months Ended Derivatives not designated as June 30, June 30, hedging instruments: 2015 2014 2015 2014 Net realized gains (losses): Futures contracts $ (31,446 ) $ 15,185 $ (12,120 ) $ 5,323 Foreign currency forward contracts (8,724 ) (1,811 ) 8,095 (4,068 ) TBAs (182 ) (270 ) 304 (307 ) Other (1,144 ) (702 ) (1,099 ) (1,314 ) Total $ (41,496 ) $ 12,402 $ (4,820 ) $ (366 )

Other Comprehensive Income (L30

Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 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 Six Months Ended Details About Line Item That Includes June 30, June 30, AOCI Components Reclassification 2015 2014 2015 2014 Unrealized appreciation on available-for-sale investments Net realized gains (losses) $ 23,259 $ 23,735 $ 65,690 $ 49,773 Other-than-temporary impairment losses (1,126 ) (14,749 ) (8,373 ) (17,720 ) Total before tax 22,133 8,986 57,317 32,053 Income tax (expense) benefit (919 ) (701 ) (5,171 ) (2,519 ) Net of tax $ 21,214 $ 8,285 $ 52,146 $ 29,534
Schedule of comprehensive income (loss)	Before Tax Amount Tax Expense (Benefit) Net of Tax Amount Three Months Ended June 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (96,629 ) $ (14,694 ) $ (81,935 ) Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (13 ) — (13 ) Less reclassification of net realized gains (losses) included in net income 22,133 919 21,214 Foreign currency translation adjustments 11,697 117 11,580 Other comprehensive income (loss) $ (107,078 ) $ (15,496 ) $ (91,582 ) Three Months Ended June 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ 115,150 $ 6,722 $ 108,428 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 8,986 701 8,285 Foreign currency translation adjustments 10,021 — 10,021 Other comprehensive income (loss) $ 116,185 $ 6,021 $ 110,164 Six Months Ended June 30, 2015 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ (2,242 ) $ (4,611 ) $ 2,369 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) (1,461 ) — (1,461 ) Less reclassification of net realized gains (losses) included in net income 57,317 5,171 52,146 Foreign currency translation adjustments (11,929 ) (752 ) (11,177 ) Other comprehensive income (loss) $ (72,949 ) $ (10,534 ) $ (62,415 ) Six Months Ended June 30, 2014 Unrealized appreciation (decline) in value of investments: Unrealized holding gains (losses) arising during period $ 190,550 $ 10,769 $ 179,781 Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss) — — — Less reclassification of net realized gains (losses) included in net income 32,053 2,519 29,534 Foreign currency translation adjustments 8,672 — 8,672 Other comprehensive income (loss) $ 167,169 $ 8,250 $ 158,919

Guarantor Financial Informati31

Guarantor Financial Information (Tables)	6 Months Ended
	Jun. 30, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed consolidating balance sheet	June 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 $ 471 $ 55,047 $ 15,306,122 $ (14,700 ) $ 15,346,940 Cash 10,864 6,928 507,282 — 525,074 Investments in subsidiaries 6,530,452 1,688,419 — (8,218,871 ) — Due from subsidiaries and affiliates 11 47,798 417,231 (465,040 ) — Premiums receivable — — 1,620,756 (439,120 ) 1,181,636 Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses — — 5,741,646 (3,910,419 ) 1,831,227 Contractholder receivables — — 1,393,138 — 1,393,138 Prepaid reinsurance premiums — — 1,595,550 (1,153,409 ) 442,141 Deferred acquisition costs, net — — 448,647 — 448,647 Other assets 4,208 46,157 2,274,796 (409,039 ) 1,916,122 Total assets $ 6,546,006 $ 1,844,349 $ 29,305,168 $ (14,610,598 ) $ 23,084,925 Liabilities Reserve for losses and loss adjustment expenses $ — $ — $ 12,970,720 $ (3,888,439 ) $ 9,082,281 Unearned premiums — — 3,596,332 (1,153,409 ) 2,442,923 Reinsurance balances payable — — 678,216 (425,754 ) 252,462 Contractholder payables — — 1,393,138 — 1,393,138 Deposit accounting liabilities — — 495,121 (217,598 ) 277,523 Senior notes 296,834 494,388 — — 791,222 Revolving credit agreement borrowings 100,000 — — — 100,000 Due to subsidiaries and affiliates 402 35,000 429,638 (465,040 ) — Other liabilities 11,255 44,917 1,778,600 (226,787 ) 1,607,985 Total liabilities 408,491 574,305 21,341,765 (6,377,027 ) 15,947,534 Redeemable noncontrolling interests — — 219,696 (14,700 ) 204,996 Shareholders’ Equity Total shareholders’ equity available to Arch 6,137,515 1,270,044 6,948,827 (8,218,871 ) 6,137,515 Non-redeemable noncontrolling interests — — 794,880 — 794,880 Total shareholders’ equity 6,137,515 1,270,044 7,743,707 (8,218,871 ) 6,932,395 Total liabilities, noncontrolling interests and shareholders’ equity $ 6,546,006 $ 1,844,349 $ 29,305,168 $ (14,610,598 ) $ 23,084,925 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 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 1,000,138 (194,298 ) 872,380 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 June 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 $ — $ — $ 943,438 $ — $ 943,438 Net investment income — 800 87,154 (991 ) 86,963 Net realized gains (losses) — 1 (35,726 ) — (35,725 ) Net impairment losses recognized in earnings — — (1,113 ) — (1,113 ) Other underwriting income — — 7,717 — 7,717 Equity in net income of investment funds accounted for using the equity method — — 16,167 — 16,167 Other income (loss) — — 2,205 — 2,205 Total revenues — 801 1,019,842 (991 ) 1,019,652 Expenses Losses and loss adjustment expenses — — 519,426 — 519,426 Acquisition expenses — — 175,425 — 175,425 Other operating expenses 16,900 1,012 150,696 — 168,608 Interest expense 5,862 6,769 (7,793 ) (827 ) 4,011 Net foreign exchange losses (gains) — — 6,942 12,641 19,583 Total expenses 22,762 7,781 844,696 11,814 887,053 Income (loss) before income taxes (22,762 ) (6,980 ) 175,146 (12,805 ) 132,599 Income tax (expense) benefit — 3,697 (10,477 ) — (6,780 ) Income (loss) before equity in net income of subsidiaries (22,762 ) (3,283 ) 164,669 (12,805 ) 125,819 Equity in net income of subsidiaries 138,552 14,077 — (152,629 ) — Net income 115,790 10,794 164,669 (165,434 ) 125,819 Amounts attributable to noncontrolling interests — — (10,193 ) 164 (10,029 ) Net income available to Arch 115,790 10,794 154,476 (165,270 ) 115,790 Preferred dividends (5,485 ) — — — (5,485 ) Net income available to Arch common shareholders $ 110,305 $ 10,794 $ 154,476 $ (165,270 ) $ 110,305 Comprehensive income (loss) available to Arch $ 24,208 $ (13,505 ) $ 50,249 $ (36,744 ) $ 24,208 Three Months Ended June 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 $ — $ — $ 907,152 $ — $ 907,152 Net investment income — — 80,380 (7,390 ) 72,990 Net realized gains (losses) — — 54,144 — 54,144 Net impairment losses recognized in earnings — — (14,749 ) — (14,749 ) Other underwriting income — — 2,033 — 2,033 Equity in net income of investment funds accounted for using the equity method — — 9,240 — 9,240 Other income (loss) — — 4,850 — 4,850 Total revenues — — 1,043,050 (7,390 ) 1,035,660 Expenses Losses and loss adjustment expenses — — 485,518 — 485,518 Acquisition expenses — — 158,158 — 158,158 Other operating expenses 15,250 494 140,606 — 156,350 Interest expense 5,854 6,448 9,422 (7,390 ) 14,334 Net foreign exchange losses (gains) — — 1,054 1,240 2,294 Total expenses 21,104 6,942 794,758 (6,150 ) 816,654 Income (loss) before income taxes (21,104 ) (6,942 ) 248,292 (1,240 ) 219,006 Income tax (expense) benefit — 3,294 (10,583 ) — (7,289 ) Income (loss) before equity in net income of subsidiaries (21,104 ) (3,648 ) 237,709 (1,240 ) 211,717 Equity in net income of subsidiaries 229,120 9,334 — (238,454 ) — Net income 208,016 5,686 237,709 (239,694 ) 211,717 Amounts attributable to noncontrolling interests — — (3,701 ) — (3,701 ) Net income available to Arch 208,016 5,686 234,008 (239,694 ) 208,016 Preferred dividends (5,485 ) — — — (5,485 ) Net income available to Arch common shareholders $ 202,531 $ 5,686 $ 234,008 $ (239,694 ) $ 202,531 Comprehensive income (loss) available to Arch $ 318,180 $ 23,186 $ 335,348 $ (358,534 ) $ 318,180 Six Months Ended June 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 $ — $ — $ 1,853,702 $ — $ 1,853,702 Net investment income — 805 173,164 (8,012 ) 165,957 Net realized gains (losses) — 1 47,622 — 47,623 Net impairment losses recognized in earnings — — (6,912 ) — (6,912 ) Other underwriting income — — 19,253 — 19,253 Equity in net income of investment funds accounted for using the equity method — — 22,056 — 22,056 Other income (loss) — — 317 — 317 Total revenues — 806 2,109,202 (8,012 ) 2,101,996 Expenses Losses and loss adjustment expenses — — 1,013,142 — 1,013,142 Acquisition expenses — — 338,501 — 338,501 Other operating expenses 25,532 2,271 298,687 — 326,490 Interest expense 11,718 13,135 (258 ) (7,848 ) 16,747 Net foreign exchange losses (gains) — — (32,688 ) (14,230 ) (46,918 ) Total expenses 37,250 15,406 1,617,384 (22,078 ) 1,647,962 Income (loss) before income taxes (37,250 ) (14,600 ) 491,818 14,066 454,034 Income tax (expense) benefit — 5,110 (24,568 ) — (19,458 ) Income (loss) before equity in net income of subsidiaries (37,250 ) (9,490 ) 467,250 14,066 434,576 Equity in net income of subsidiaries 436,376 28,572 — (464,948 ) — Net income 399,126 19,082 467,250 (450,882 ) 434,576 Amounts attributable to noncontrolling interests — — (35,614 ) 164 (35,450 ) Net income available to Arch 399,126 19,082 431,636 (450,718 ) 399,126 Preferred dividends (10,969 ) — — — (10,969 ) Net income available to Arch common shareholders $ 388,157 $ 19,082 $ 431,636 $ (450,718 ) $ 388,157 Comprehensive income (loss) available to Arch $ 336,711 $ (1,755 ) $ 383,442 $ (381,687 ) $ 336,711 Six Months Ended June 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 $ — $ — $ 1,766,932 $ — $ 1,766,932 Net investment income — — 157,381 (17,397 ) 139,984 Net realized gains (losses) — — 73,841 — 73,841 Net impairment losses recognized in earnings — — (17,720 ) — (17,720 ) Other underwriting income — — 3,615 — 3,615 Equity in net income of investment funds accounted for using the equity method — — 12,493 — 12,493 Other income (loss) — — 2,746 — 2,746 Total revenues — — 1,999,288 (17,397 ) 1,981,891 Expenses Losses and loss adjustment expenses — — 921,758 — 921,758 Acquisition expenses — — 318,500 — 318,500 Other operating expenses 25,557 1,471 275,121 — 302,149 Interest expense 11,707 12,962 21,466 (17,397 ) 28,738 Net foreign exchange losses (gains) — — 6,795 2,062 8,857 Total expenses 37,264 14,433 1,543,640 (15,335 ) 1,580,002 Income (loss) before income taxes (37,264 ) (14,433 ) 455,648 (2,062 ) 401,889 Income tax (expense) benefit — 6,082 (17,109 ) — (11,027 ) Income (loss) before equity in net income of subsidiaries (37,264 ) (8,351 ) 438,539 (2,062 ) 390,862 Equity in net income of subsidiaries 427,780 31,486 — (459,266 ) — Net income 390,516 23,135 438,539 (461,328 ) 390,862 Amounts attributable to noncontrolling interests — — (346 ) — (346 ) Net income available to Arch 390,516 23,135 438,193 (461,328 ) 390,516 Preferred dividends (10,969 ) — — — (10,969 ) Net income available to Arch common shareholders $ 379,547 $ 23,135 $ 438,193 $ (461,328 ) $ 379,547 Comprehensive income (loss) available to Arch $ 549,435 $ 40,406 $ 587,467 $ (627,873 ) $ 549,435
Condensed consolidating statement of cash flows	Six Months Ended June 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 $ 378,703 $ 8,282 $ 433,833 $ (435,619 ) $ 385,199 Investing Activities Purchases of fixed maturity investments — — (14,641,391 ) — (14,641,391 ) Purchases of equity securities — — (288,535 ) — (288,535 ) Purchases of other investments — — (1,273,780 ) — (1,273,780 ) Proceeds from the sales of fixed maturity investments — 20,002 14,335,517 — 14,355,519 Proceeds from the sales of equity securities — — 272,343 — 272,343 Proceeds from the sales, redemptions and maturities of other investments — — 1,078,675 — 1,078,675 Proceeds from redemptions and maturities of fixed maturity investments — — 474,984 — 474,984 Proceeds from investment in joint venture — — 40,000 — 40,000 Net purchases (sales) of short-term investments (365 ) (12,171 ) 16,243 — 3,707 Change in cash collateral related to securities lending — — (18,329 ) — (18,329 ) Contributions to subsidiaries — — (9,290 ) 9,290 — Intercompany loans issued — (39,500 ) (27,500 ) 67,000 — Purchase of business, net of cash acquired — — 818 — 818 Purchases of furniture, equipment and other assets (24 ) — (43,141 ) — (43,165 ) Net Cash Provided By (Used For) Investing Activities (389 ) (31,669 ) (83,386 ) 76,290 (39,154 ) Financing Activities Purchases of common shares under share repurchase program (361,877 ) — — — (361,877 ) Proceeds from common shares issued, net 2,178 — 9,290 (9,290 ) 2,178 Proceeds from intercompany borrowings — 27,500 39,500 (67,000 ) — Change in cash collateral related to securities lending — — 18,329 — 18,329 Dividends paid to redeemable noncontrolling interests — — (9,632 ) 319 (9,313 ) Dividends paid to parent — — (435,300 ) 435,300 — Other — 28 54,990 — 55,018 Preferred dividends paid (10,969 ) — — — (10,969 ) Net Cash Provided By (Used For) Financing Activities (370,668 ) 27,528 (322,823 ) 359,329 (306,634 ) Effects of exchange rates changes on foreign currency cash — — (39 ) — (39 ) Increase (decrease) in cash 7,646 4,141 27,585 — 39,372 Cash beginning of year 3,218 2,787 479,697 — 485,702 Cash end of period $ 10,864 $ 6,928 $ 507,282 $ — $ 525,074 Six Months Ended June 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 $ 10,099 $ 424 $ 474,565 $ (32,025 ) $ 453,063 Investing Activities Purchases of fixed maturity investments — (78,509 ) (14,233,239 ) — (14,311,748 ) Purchases of equity securities — — (174,687 ) — (174,687 ) Purchases of other investments — — (1,022,987 ) — (1,022,987 ) Proceeds from the sales of fixed maturity investments — — 13,204,854 — 13,204,854 Proceeds from the sales of equity securities — — 98,687 — 98,687 Proceeds from the sales of other investments — — 618,707 — 618,707 Proceeds from redemptions and maturities of fixed maturity investments — — 432,040 — 432,040 Net (purchases) sales of short-term investments (31 ) 408,779 21,556 — 430,304 Change in cash collateral related to securities lending — — 18,701 — 18,701 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 furniture, equipment and other assets (128 ) — (10,232 ) — (10,360 ) Net Cash Provided By (Used For) Investing Activities (159 ) 17,063 (1,371,928 ) 402,957 (952,067 ) Financing Activities Proceeds from common shares issued, net 2,521 — 413,207 (413,207 ) 2,521 Repayments of intercompany borrowings — (10,250 ) — 10,250 — Change in cash collateral related to securities lending — — (18,701 ) — (18,701 ) 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 — — (4,816 ) — (4,816 ) Dividends paid to parent — — (32,025 ) 32,025 — Other — — 4,706 — 4,706 Preferred dividends paid (10,969 ) — — — (10,969 ) Net Cash Provided By (Used For) Financing Activities (8,448 ) (10,250 ) 1,378,507 (370,932 ) 988,877 Effects of exchange rates changes on foreign currency cash — — 2,513 — 2,513 Increase in cash 1,492 7,237 483,657 — 492,386 Cash beginning of year 3,223 509 430,325 — 434,057 Cash end of period $ 4,715 $ 7,746 $ 913,982 $ — $ 926,443

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	6 Months Ended
	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Variable Interest Entity [Line Items]
Unearned premiums		$ 2,442,923		$ 2,231,578
Reserve for losses and loss adjustment expenses		9,082,281		$ 9,036,448
Net cash provided by operating activities		385,199	$ 453,063
Net cash provided by financing activities		(306,634)	988,877
Net cash provided by (used in) investing activities		(39,154)	$ (952,067)
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		247,600
Reserve for losses and loss adjustment expenses		173,200
Net cash provided by operating activities		137,800
Net cash provided by financing activities		40,300
Net cash provided by (used in) investing activities		$ (134,900)

Variable Interest Entities an35

Variable Interest Entities and Noncontrolling Interests - Non-redeemable noncontrolling interests (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Noncontrolling Interest [Line Items]
Non-redeemable noncontrolling interests, beginning of period			$ 769,081
Amounts attributable to noncontrolling interests	$ 5,286	$ (1,156)	25,799	$ (4,563)
Non-redeemable noncontrolling interests, end of period	794,880	792,340	794,880	792,340
Watford Re
Noncontrolling Interest [Line Items]
Non-redeemable noncontrolling interests, beginning of period	789,594	793,496	769,081	0
Sale of shares to noncontrolling interests	0	0	0	796,903
Amounts attributable to noncontrolling interests	5,286	(1,156)	25,799	(4,563)
Non-redeemable noncontrolling interests, end of period	$ 794,880	$ 792,340	$ 794,880	$ 792,340
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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests, beginning of period			$ 219,512
Redeemable noncontrolling interests, end of period	$ 204,996		204,996
Watford Re
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests, beginning of period	219,604	$ 219,234	219,512	$ 0
Sale of shares to noncontrolling interests	0	0	0	219,233
Shares acquired by the Company	(14,700)	0	(14,700)	0
Accretion of preference share issuance costs	92	92	184	93
Redeemable noncontrolling interests, end of period	$ 204,996	$ 219,326	$ 204,996	$ 219,326
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) - Consolidation Items [Domain] - Entity [Domain] - Equity Component [Domain] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Noncontrolling Interest [Line Items]
Amounts attributable to non-redeemable noncontrolling interests	$ (5,286)	$ 1,156	$ (25,799)	$ 4,563
Amounts attributable to redeemable noncontrolling interests	(4,743)	(4,857)	(9,651)	(4,909)
Amounts attributable to noncontrolling interests	$ (10,029)	$ (3,701)	$ (35,450)	$ (346)

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net income	$ 125,819		$ 211,717		$ 434,576	$ 390,862
Amounts attributable to noncontrolling interests	(10,029)		(3,701)		(35,450)	(346)
Net income available to Arch	115,790		208,016		399,126	390,516
Preferred dividends	(5,485)		(5,485)		(10,969)	(10,969)
Net income (loss) available to Arch common shareholders	$ 110,305		$ 202,531		$ 388,157	$ 379,547
Denominator:
Weighted average common shares outstanding — basic	121,719,214		132,650,634		122,957,384	132,256,462
Effect of dilutive common share equivalents:
Nonvested restricted shares	1,258,741		1,144,621		1,334,633	1,236,408
Stock options	2,907,465	[1]	3,094,689	[1]	2,864,696	3,224,019
Weighted average common shares and common share equivalents outstanding — diluted	125,885,420		136,889,944		127,156,713	136,716,889
Earnings per common share:
Basic (per share)	$ 0.91		$ 1.53		$ 3.16	$ 2.87
Diluted (per share)	$ 0.88		$ 1.48		$ 3.05	$ 2.78
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per common share (shares)	1,009,113		978,237		1,187,162	1,318,662
[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 second quarter and 2014 second quarter, the number of stock options excluded were 1,009,113 and 978,237, respectively. For the six months ended June 30, 2015 and 2014, the number of stock options excluded were 1,187,162 and 1,318,662, respectively.

Segment Information - Summary o

Segment Information - Summary of underwriting income or loss by segment (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Gross premiums written		$ 1,199,209	$ 1,271,761	$ 2,541,231	$ 2,566,897
Premiums ceded		(255,629)	(299,833)	(530,656)	(529,979)
Net premiums written		943,580	971,928	2,010,575	2,036,918
Change in unearned premiums		(142)	(64,776)	(156,873)	(269,986)
Net premiums earned		943,438	907,152	1,853,702	1,766,932
Other underwriting income		7,717	2,033	19,253	3,615
Losses and loss adjustment expenses		(519,426)	(485,518)	(1,013,142)	(921,758)
Acquisition expenses, net		(175,425)	(158,158)	(338,501)	(318,500)
Other operating expenses		(151,190)	(141,418)	(299,727)	(273,742)
Underwriting income (loss)		105,114	124,091	221,585	256,547
Net investment income		86,963	72,990	165,957	139,984
Net realized gains (losses)		(35,725)	54,144	47,623	73,841
Net impairment losses recognized in earnings		(1,113)	(14,749)	(6,912)	(17,720)
Equity in net income (loss) of investment funds accounted for using the equity method		16,167	9,240	22,056	12,493
Other income (loss)		2,205	4,850	317	2,746
Other expenses		(17,418)	(14,932)	(26,763)	(28,407)
Interest expense		(4,011)	(14,334)	(16,747)	(28,738)
Net foreign exchange gains (losses)		(19,583)	(2,294)	46,918	(8,857)
Income before income taxes		132,599	219,006	454,034	401,889
Income tax expense		(6,780)	(7,289)	(19,458)	(11,027)
Net income (loss)		125,819	211,717	434,576	390,862
Dividends attributable to redeemable noncontrolling interests		(4,743)	(4,857)	(9,651)	(4,909)
Amounts attributable to non-redeemable noncontrolling interests		(5,286)	1,156	(25,799)	4,563
Net income available to Arch		115,790	208,016	399,126	390,516
Preferred dividends		(5,485)	(5,485)	(10,969)	(10,969)
Net income (loss) available to Arch common shareholders		$ 110,305	$ 202,531	$ 388,157	$ 379,547
Underwriting Ratios
Loss ratio		55.10%	53.50%	54.70%	52.20%
Acquisition expense ratio		18.60%	17.40%	18.30%	18.00%
Other operating expense ratio		16.00%	15.60%	16.20%	15.50%
Combined ratio		89.70%	86.50%	89.20%	85.70%
Goodwill and intangible assets		$ 102,518	$ 118,721	$ 102,518	$ 118,721	$ 109,539
Total investable assets		15,854,128	15,803,527	15,854,128	15,803,527
Total assets		23,084,925	22,567,447	23,084,925	22,567,447	22,006,081
Total liabilities		15,947,534	15,326,382	15,947,534	15,326,382	$ 14,887,435
Sub-Total
Segment Reporting Information [Line Items]
Gross premiums written	[1]	1,155,253	1,256,934	2,466,931	2,552,070
Premiums ceded		(331,861)	(336,808)	(701,122)	(599,148)
Net premiums written		823,392	920,126	1,765,809	1,952,922
Change in unearned premiums		12,857	(25,954)	(91,562)	(201,136)
Net premiums earned		836,249	894,172	1,674,247	1,751,786
Other underwriting income		6,865	2,033	16,439	3,615
Losses and loss adjustment expenses		(441,748)	(477,324)	(885,985)	(912,208)
Acquisition expenses, net		(145,283)	(153,965)	(287,383)	(313,484)
Other operating expenses		(147,740)	(139,783)	(294,272)	(270,998)
Underwriting income (loss)		108,343	125,133	223,046	258,711
Net investment income		67,171	72,458	137,459	139,451
Net realized gains (losses)		(26,860)	50,966	38,649	70,663
Net impairment losses recognized in earnings		(1,113)	(14,749)	(6,912)	(17,720)
Equity in net income (loss) of investment funds accounted for using the equity method		16,167	9,240	22,056	12,493
Other income (loss)		2,205	4,850	317	2,746
Other expenses		(17,418)	(15,279)	(26,763)	(26,078)
Interest expense		(4,011)	(14,334)	(16,747)	(28,738)
Net foreign exchange gains (losses)		(22,571)	(2,764)	44,282	(9,420)
Income before income taxes		121,913	215,521	415,387	402,108
Income tax expense		(6,780)	(7,289)	(19,458)	(11,027)
Net income (loss)		115,133	208,232	395,929	391,081
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		115,133	208,232	395,929	391,081
Preferred dividends		(5,485)	(5,485)	(10,969)	(10,969)
Net income (loss) available to Arch common shareholders		$ 109,648	$ 202,747	$ 384,960	$ 380,112
Underwriting Ratios
Loss ratio		52.80%	53.40%	52.90%	52.10%
Acquisition expense ratio		17.40%	17.20%	17.20%	17.90%
Other operating expense ratio		17.70%	15.60%	17.60%	15.50%
Combined ratio		87.90%	86.20%	87.70%	85.50%
Goodwill and intangible assets		$ 102,518	$ 118,721	$ 102,518	$ 118,721
Total investable assets		14,513,554	14,688,808	14,513,554	14,688,808
Total assets		21,323,611	21,204,129	21,323,611	21,204,129
Total liabilities		15,299,256	15,072,875	15,299,256	15,072,875
Sub-Total | Insurance
Segment Reporting Information [Line Items]
Gross premiums written	[1]	744,810	852,231	1,510,963	1,582,877
Premiums ceded		(235,743)	(273,349)	(459,893)	(458,393)
Net premiums written		509,067	578,882	1,051,070	1,124,484
Change in unearned premiums		758	(71,170)	(33,331)	(139,271)
Net premiums earned		509,825	507,712	1,017,739	985,213
Other underwriting income		521	514	948	1,014
Losses and loss adjustment expenses		(320,926)	(311,526)	(638,822)	(598,296)
Acquisition expenses, net		(76,723)	(76,449)	(151,801)	(153,381)
Other operating expenses		(89,054)	(85,829)	(177,173)	(166,973)
Underwriting income (loss)		$ 23,643	$ 34,422	$ 50,891	$ 67,577
Underwriting Ratios
Loss ratio		62.90%	61.40%	62.80%	60.70%
Acquisition expense ratio		15.00%	15.10%	14.90%	15.60%
Other operating expense ratio		17.50%	16.90%	17.40%	16.90%
Combined ratio		95.40%	93.40%	95.10%	93.20%
Goodwill and intangible assets		$ 30,968	$ 24,498	$ 30,968	$ 24,498
Sub-Total | Reinsurance
Segment Reporting Information [Line Items]
Gross premiums written	[1]	342,101	349,841	827,213	866,894
Premiums ceded		(89,446)	(58,994)	(226,015)	(132,121)
Net premiums written		252,655	290,847	601,198	734,773
Change in unearned premiums		21,310	44,780	(47,516)	(57,798)
Net premiums earned		273,965	335,627	553,682	676,975
Other underwriting income		2,658	303	4,087	619
Losses and loss adjustment expenses		(111,183)	(150,325)	(223,715)	(289,961)
Acquisition expenses, net		(58,360)	(66,035)	(114,964)	(139,468)
Other operating expenses		(39,007)	(37,666)	(77,051)	(73,861)
Underwriting income (loss)		$ 68,073	$ 81,904	$ 142,039	$ 174,304
Underwriting Ratios
Loss ratio		40.60%	44.80%	40.40%	42.80%
Acquisition expense ratio		21.30%	19.70%	20.80%	20.60%
Other operating expense ratio		14.20%	11.20%	13.90%	10.90%
Combined ratio		76.10%	75.70%	75.10%	74.30%
Goodwill and intangible assets		$ 2,420	$ 4,942	$ 2,420	$ 4,942
Sub-Total | Mortgage
Segment Reporting Information [Line Items]
Gross premiums written	[1]	68,572	55,476	129,113	103,383
Premiums ceded		(6,902)	(5,079)	(15,572)	(9,718)
Net premiums written		61,670	50,397	113,541	93,665
Change in unearned premiums		(9,211)	436	(10,715)	(4,067)
Net premiums earned		52,459	50,833	102,826	89,598
Other underwriting income		3,686	1,216	11,404	1,982
Losses and loss adjustment expenses		(9,639)	(15,473)	(23,448)	(23,951)
Acquisition expenses, net		(10,200)	(11,481)	(20,618)	(20,635)
Other operating expenses		(19,679)	(16,288)	(40,048)	(30,164)
Underwriting income (loss)		$ 16,627	$ 8,807	$ 30,116	$ 16,830
Underwriting Ratios
Loss ratio		18.40%	30.40%	22.80%	26.70%
Acquisition expense ratio		19.40%	22.60%	20.10%	23.00%
Other operating expense ratio		37.50%	32.00%	38.90%	33.70%
Combined ratio		75.30%	85.00%	81.80%	83.40%
Goodwill and intangible assets		$ 69,130	$ 89,281	$ 69,130	$ 89,281
Other
Segment Reporting Information [Line Items]
Gross premiums written	[1]	127,954	54,562	256,587	86,756
Premiums ceded		(7,766)	(2,760)	(11,821)	(2,760)
Net premiums written		120,188	51,802	244,766	83,996
Change in unearned premiums		(12,999)	(38,822)	(65,311)	(68,850)
Net premiums earned		107,189	12,980	179,455	15,146
Other underwriting income		852	0	2,814	0
Losses and loss adjustment expenses		(77,678)	(8,194)	(127,157)	(9,550)
Acquisition expenses, net		(30,142)	(4,193)	(51,118)	(5,016)
Other operating expenses		(3,450)	(1,635)	(5,455)	(2,744)
Underwriting income (loss)		(3,229)	(1,042)	(1,461)	(2,164)
Net investment income		19,792	532	28,498	533
Net realized gains (losses)		(8,865)	3,178	8,974	3,178
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	347	0	(2,329)
Interest expense		0	0	0	0
Net foreign exchange gains (losses)		2,988	470	2,636	563
Income before income taxes		10,686	3,485	38,647	(219)
Income tax expense		0	0	0	0
Net income (loss)		10,686	3,485	38,647	(219)
Dividends attributable to redeemable noncontrolling interests		(4,743)	(4,857)	(9,651)	(4,909)
Amounts attributable to non-redeemable noncontrolling interests		(5,286)	1,156	(25,799)	4,563
Net income available to Arch		657	(216)	3,197	(565)
Preferred dividends		0	0	0	0
Net income (loss) available to Arch common shareholders		$ 657	$ (216)	$ 3,197	$ (565)
Underwriting Ratios
Loss ratio		72.50%	63.10%	70.90%	63.10%
Acquisition expense ratio		28.10%	32.30%	28.50%	33.10%
Other operating expense ratio		3.20%	12.60%	3.00%	18.10%
Combined ratio		103.80%	108.00%	102.40%	114.30%
Goodwill and intangible assets		$ 0	$ 0	$ 0	$ 0
Total investable assets		1,340,574	1,114,719	1,340,574	1,114,719
Total assets		1,761,314	1,363,318	1,761,314	1,363,318
Total liabilities		$ 648,278	$ 253,507	$ 648,278	$ 253,507
[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)	6 Months Ended
	Jun. 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		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Available for sale securities:
Estimated Fair Value		$ 12,256,599	$ 12,553,204
Gross Unrealized Gains		242,602	282,262
Gross Unrealized Losses		(132,978)	(111,730)
Cost or Amortized Cost		12,146,975	12,382,672
OTTI Unrealized Losses	[1]	(4,267)	(3,646)
Fixed maturities
Available for sale securities:
Estimated Fair Value		10,301,572	10,801,572
Gross Unrealized Gains	[2]	91,207	140,673
Gross Unrealized Losses	[2]	(109,678)	(92,734)
Cost or Amortized Cost	[2]	10,320,043	10,753,633
OTTI Unrealized Losses	[1],[2]	(4,267)	(3,646)
Fixed maturities | Corporate bonds
Available for sale securities:
Estimated Fair Value		2,833,849	3,108,513
Gross Unrealized Gains	[2]	26,401	37,928
Gross Unrealized Losses	[2]	(51,717)	(38,974)
Cost or Amortized Cost	[2]	2,859,165	3,109,559
OTTI Unrealized Losses	[1],[2]	(681)	(317)
Fixed maturities | Mortgage backed securities
Available for sale securities:
Estimated Fair Value		837,680	943,343
Gross Unrealized Gains	[2]	12,315	18,843
Gross Unrealized Losses	[2]	(4,231)	(3,842)
Cost or Amortized Cost	[2]	829,596	928,342
OTTI Unrealized Losses	[1],[2]	(3,564)	(3,307)
Fixed maturities | Municipal bonds
Available for sale securities:
Estimated Fair Value		1,760,384	1,494,122
Gross Unrealized Gains	[2]	19,601	31,227
Gross Unrealized Losses	[2]	(9,004)	(1,044)
Cost or Amortized Cost	[2]	1,749,787	1,463,939
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | Commercial mortgage backed securities
Available for sale securities:
Estimated Fair Value		832,159	1,114,528
Gross Unrealized Gains	[2]	6,760	14,594
Gross Unrealized Losses	[2]	(4,922)	(3,822)
Cost or Amortized Cost	[2]	830,321	1,103,756
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | US government and government agencies
Available for sale securities:
Estimated Fair Value		1,899,868	1,447,972
Gross Unrealized Gains	[2]	8,463	8,345
Gross Unrealized Losses	[2]	(3,720)	(1,760)
Cost or Amortized Cost	[2]	1,895,125	1,441,387
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | Non-US government securities
Available for sale securities:
Estimated Fair Value		786,276	1,015,153
Gross Unrealized Gains	[2]	10,343	21,311
Gross Unrealized Losses	[2]	(32,720)	(37,203)
Cost or Amortized Cost	[2]	808,653	1,031,045
OTTI Unrealized Losses	[1],[2]	0	0
Fixed maturities | Asset backed securities
Available for sale securities:
Estimated Fair Value		1,351,356	1,677,941
Gross Unrealized Gains	[2]	7,324	8,425
Gross Unrealized Losses	[2]	(3,364)	(6,089)
Cost or Amortized Cost	[2]	1,347,396	1,675,605
OTTI Unrealized Losses	[1],[2]	(22)	(22)
Equity securities
Available for sale securities:
Estimated Fair Value		701,623	658,182
Gross Unrealized Gains		105,174	109,012
Gross Unrealized Losses		(18,606)	(13,364)
Cost or Amortized Cost		615,055	562,534
OTTI Unrealized Losses	[1]	0	0
Other investments
Available for sale securities:
Estimated Fair Value		377,677	296,224
Gross Unrealized Gains		46,166	31,839
Gross Unrealized Losses		(1,927)	(362)
Cost or Amortized Cost		333,438	264,747
OTTI Unrealized Losses	[1]	0	0
Short-term investments
Available for sale securities:
Estimated Fair Value		875,727	797,226
Gross Unrealized Gains		55	738
Gross Unrealized Losses		(2,767)	(5,270)
Cost or Amortized Cost		878,439	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 June 30, 2015, the net unrealized gain related to securities for which a non-credit OTTI was recognized in AOCI was $0.3 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		Jun. 30, 2015	Dec. 31, 2014
Available for sale securities:
Estimated Fair Value - Less than 12 Months		$ 4,831,057	$ 4,108,030
Gross Unrealized Losses - Less than 12 Months		(103,686)	(90,017)
Estimated Fair Value - 12 Months or More		352,050	641,407
Gross Unrealized Losses - 12 Months or More		(29,292)	(21,713)
Estimated Fair Value - Total		5,183,107	4,749,437
Gross Unrealized Losses - Total		(132,978)	(111,730)
Fixed maturities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	4,394,582	3,788,119
Gross Unrealized Losses - Less than 12 Months	[1]	(80,386)	(71,021)
Estimated Fair Value - 12 Months or More	[1]	352,050	641,407
Gross Unrealized Losses - 12 Months or More	[1]	(29,292)	(21,713)
Estimated Fair Value - Total	[1]	4,746,632	4,429,526
Gross Unrealized Losses - Total	[1]	(109,678)	(92,734)
Fixed maturities | Corporate bonds
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	1,659,276	1,309,637
Gross Unrealized Losses - Less than 12 Months	[1]	(40,616)	(32,903)
Estimated Fair Value - 12 Months or More	[1]	92,244	148,963
Gross Unrealized Losses - 12 Months or More	[1]	(11,101)	(6,071)
Estimated Fair Value - Total	[1]	1,751,520	1,458,600
Gross Unrealized Losses - Total	[1]	(51,717)	(38,974)
Fixed maturities | Mortgage backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	437,043	293,624
Gross Unrealized Losses - Less than 12 Months	[1]	(3,574)	(1,476)
Estimated Fair Value - 12 Months or More	[1]	45,082	59,107
Gross Unrealized Losses - 12 Months or More	[1]	(657)	(2,366)
Estimated Fair Value - Total	[1]	482,125	352,731
Gross Unrealized Losses - Total	[1]	(4,231)	(3,842)
Fixed maturities | Municipal bonds
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	784,691	210,614
Gross Unrealized Losses - Less than 12 Months	[1]	(8,562)	(588)
Estimated Fair Value - 12 Months or More	[1]	3,530	13,643
Gross Unrealized Losses - 12 Months or More	[1]	(442)	(456)
Estimated Fair Value - Total	[1]	788,221	224,257
Gross Unrealized Losses - Total	[1]	(9,004)	(1,044)
Fixed maturities | Commercial mortgage backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	374,338	232,147
Gross Unrealized Losses - Less than 12 Months	[1]	(4,912)	(770)
Estimated Fair Value - 12 Months or More	[1]	2,893	125,894
Gross Unrealized Losses - 12 Months or More	[1]	(10)	(3,052)
Estimated Fair Value - Total	[1]	377,231	358,041
Gross Unrealized Losses - Total	[1]	(4,922)	(3,822)
Fixed maturities | US government and government agencies
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	426,224	618,381
Gross Unrealized Losses - Less than 12 Months	[1]	(3,720)	(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]	426,224	621,819
Gross Unrealized Losses - Total	[1]	(3,720)	(1,760)
Fixed maturities | Non-US government securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	431,360	510,766
Gross Unrealized Losses - Less than 12 Months	[1]	(16,841)	(31,172)
Estimated Fair Value - 12 Months or More	[1]	77,314	46,910
Gross Unrealized Losses - 12 Months or More	[1]	(15,879)	(6,031)
Estimated Fair Value - Total	[1]	508,674	557,676
Gross Unrealized Losses - Total	[1]	(32,720)	(37,203)
Fixed maturities | Asset backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	281,650	612,950
Gross Unrealized Losses - Less than 12 Months	[1]	(2,161)	(2,486)
Estimated Fair Value - 12 Months or More	[1]	130,987	243,452
Gross Unrealized Losses - 12 Months or More	[1]	(1,203)	(3,603)
Estimated Fair Value - Total	[1]	412,637	856,402
Gross Unrealized Losses - Total	[1]	(3,364)	(6,089)
Equity securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months		286,325	181,002
Gross Unrealized Losses - Less than 12 Months		(18,606)	(13,364)
Estimated Fair Value - 12 Months or More		0	0
Gross Unrealized Losses - 12 Months or More		0	0
Estimated Fair Value - Total		286,325	181,002
Gross Unrealized Losses - Total		(18,606)	(13,364)
Other investments
Available for sale securities:
Estimated Fair Value - Less than 12 Months		89,863	59,638
Gross Unrealized Losses - Less than 12 Months		(1,927)	(362)
Estimated Fair Value - 12 Months or More		0	0
Gross Unrealized Losses - 12 Months or More		0	0
Estimated Fair Value - Total		89,863	59,638
Gross Unrealized Losses - Total		(1,927)	(362)
Short-term investments
Available for sale securities:
Estimated Fair Value - Less than 12 Months		60,287	79,271
Gross Unrealized Losses - Less than 12 Months		(2,767)	(5,270)
Estimated Fair Value - 12 Months or More		0	0
Gross Unrealized Losses - 12 Months or More		0	0
Estimated Fair Value - Total		60,287	79,271
Gross Unrealized Losses - Total		$ (2,767)	$ (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		Jun. 30, 2015	Dec. 31, 2014
Estimated Fair Value:
Estimated fair value		$ 9,927,603	$ 10,750,770
Amortized Cost:
Amortized cost		9,945,598	10,701,557
Fixed maturities
Estimated Fair Value:
Due in one year or less		369,356	235,930
Due after one year through five years		4,101,484	4,074,562
Due after five years through 10 years		2,468,013	2,475,726
Due after 10 years		341,524	279,542
Single maturity date		7,280,377	7,065,760
Estimated fair value	[1]	10,301,572	10,801,572
Amortized Cost:
Due in one year or less		374,710	233,794
Due after one year through five years		4,106,002	4,077,408
Due after five years through 10 years		2,487,840	2,461,356
Due after 10 years		344,178	273,372
Single maturity date		7,312,730	7,045,930
Amortized cost	[1]	10,320,043	10,753,633
Fixed maturities | Mortgage backed securities
Estimated Fair Value:
Securities without single maturity date		837,680	943,343
Amortized Cost:
Securities without single maturity date		829,596	928,342
Fixed maturities | Commercial mortgage backed securities
Estimated Fair Value:
Securities without single maturity date		832,159	1,114,528
Amortized Cost:
Securities without single maturity date		830,321	1,103,756
Fixed maturities | Asset backed securities
Estimated Fair Value:
Securities without single maturity date		1,351,356	1,677,941
Amortized Cost:
Securities without single maturity date		$ 1,347,396	$ 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	Jun. 30, 2015	Dec. 31, 2014
Disclosure Investment Information [Abstract]
Fair value of cash collateral received on securities lending	$ 62,600
Approximate fair value of sub-prime securities backing the securities lending program	5,700	$ 5,800
Fair value of non-cash collateral received on securities lending	315,100	0
Collateral received under securities lending, at fair value (amortized cost: $373,909 and $40,473)	377,897	44,301
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	383,965	$ 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	383,965
US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	335,233
Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	44,139
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	4,593
Overnight and continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	383,965
Overnight and continuous | US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	335,233
Overnight and continuous | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	44,139
Overnight and continuous | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	4,593
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	0
30 - 90 days | US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
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	0
90 days or more | US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0
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		Jun. 30, 2015	Dec. 31, 2014
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		$ 1,969,048	$ 1,837,652
Available for sale
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		377,677	296,224
Available for sale | Investment grade fixed income
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		58,829	59,638
Available for sale | Non-investment grade fixed income
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		13,773	0
Available for sale | Asian and emerging markets
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		287,666	236,586
Available for sale | Other
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		17,409	0
Fair value option
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		1,591,371	1,541,428
Fair value option | Term loan investments
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		1,061,696	1,073,649
Other investments par		1,077,945	1,094,337
Fair value option | Mezzanine debt funds
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		115,019	121,341
Fair value option | Credit related funds
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		138,070	114,436
Fair value option | Investment grade fixed income
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		60,383	69,108
Fair value option | Asian and emerging markets
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments		26,494	25,800
Fair value option | Other
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	[1]	$ 189,709	$ 137,094
[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	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	$ 2,613,487	$ 2,425,053
Fixed Maturities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	854,170	632,024
Other investments
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	1,591,371	1,541,428
Short-term investments
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	167,698	251,601
Equity securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	$ 248	$ 0

Investment Information - Net in

Investment Information - Net investment income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net investment income:
Gross investment income		$ 102,600	$ 85,255	$ 201,562	$ 161,418
Investment expenses		(15,637)	(12,265)	(35,605)	(21,434)
Net investment income		86,963	72,990	165,957	139,984
Fixed Maturities
Net investment income:
Gross investment income		71,275	65,869	139,871	128,318
Term loan investments
Net investment income:
Gross investment income		18,033	6,908	32,777	12,577
Equity securities (dividends)
Net investment income:
Gross investment income		2,578	3,271	5,257	6,192
Short-term investments
Net investment income:
Gross investment income		225	107	421	512
Other
Net investment income:
Gross investment income	[1]	$ 10,489	$ 9,100	$ 23,236	$ 13,819
[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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net realized gains and losses:
Available for sale securities, gross gains on investment sales		$ 82,233	$ 56,763	$ 179,824	$ 122,814
Available for sale securities, gross losses on investment sales		(58,974)	(33,028)	(114,134)	(73,041)
Derivative instruments	[1]	(41,496)	12,402	(4,820)	(366)
Other	[2]	(8,638)	(10,962)	(13,226)	(13,668)
Net realized gains (losses)		(35,725)	54,144	47,623	73,841
Fixed Maturities
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		(5,191)	10,984	(8,493)	9,341
Other investments
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		785	17,985	7,072	28,761
Equity securities
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		(69)	0	(71)	0
Short-term investments
Net realized gains and losses:
Change in fair value of assets and liabilities accounted for using the fair value option		$ (4,375)	$ 0	$ 1,471	$ 0
[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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	$ (1,113)	$ (14,749)	$ (6,912)	$ (17,720)
Fixed Maturities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	(336)	(669)	(3,384)	(675)
Fixed Maturities | Mortgage backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	(326)	0	(1,398)	0
Fixed Maturities | Corporate bonds
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	(10)	(664)	(1,986)	(664)
Fixed Maturities | Asset backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	0	(5)	0	(11)
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	(124)	(278)	(253)	(278)
Other investments
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses recognized in earnings	$ (653)	$ (13,802)	$ (934)	$ (16,767)

Investment Information - Othe50

Investment Information - Other than temporary impairments rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Rollforward:
Balance at start of period	$ 24,344	$ 47,256	$ 20,196	$ 60,062
Credit loss impairments recognized on securities not previously impaired	281	0	4,770	0
Credit loss impairments recognized on securities previously impaired	55	5	134	11
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	(3,774)	(25,820)	(4,194)	(38,632)
Balance at end of period	$ 20,906	$ 21,441	$ 20,906	$ 21,441

Investment Information - Restri

Investment Information - Restricted assets (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Restricted Assets [Line Items]
Restricted assets	$ 5,159,041	$ 5,519,089
Collateral or guarantees - affiliated transactions
Restricted Assets [Line Items]
Restricted assets	3,651,244	4,138,527
Collateral or guarantees - third party agreements
Restricted Assets [Line Items]
Restricted assets	1,040,156	970,120
Deposits with US regulatory authorities
Restricted Assets [Line Items]
Restricted assets	406,777	337,981
Trust funds
Restricted Assets [Line Items]
Restricted assets	$ 60,864	$ 72,461

Investment Information - Narrat

Investment Information - Narrative (Details) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2015USD ($)lots	Dec. 31, 2014USD ($)lots	Jun. 30, 2014USD ($)
Narrative items:
Investable assets		$ 15,854,128		$ 15,803,527
OTTI unrealized losses at current fair value		$ 300	$ 900
Continuous unrealized loss, qualitative disclosures:
Number of positions in an unrealized loss position (lots) | lots		2,620	1,900
Total number of positions (lots) | lots		5,580	4,790
Largest single loss		$ 2,900	$ 2,900
OTTI unrealized losses (gains)	[1]	4,267	$ 3,646
Underwriting segments
Narrative items:
Investable assets		14,513,554		14,688,808
Other
Narrative items:
Investable assets		$ 1,340,574		$ 1,114,719
[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 June 30, 2015, the net unrealized gain related to securities for which a non-credit OTTI was recognized in AOCI was $0.3 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		Jun. 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		$ 3,802,137	$ 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) | 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]	1,878,893	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]	1,878,893	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		698,078	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		870,738	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		89,611	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		89,611	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		264,817	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 | 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		167,698	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		248
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		96,871	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		10,309,721	11,220,264
Liabilities measured at fair value		(11,731)	(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) | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	[1]	(11,731)	(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]	8,365,179	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]	2,833,849	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]	837,680	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]	1,760,384	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]	832,159	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]	20,975	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]	786,276	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]	1,293,856	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		3,545	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		4,989	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]	20,142	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		1,915,866	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		682,569	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		58,565	22,190
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		89,168	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		23,868	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		1,061,696	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		(71,256)	(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		(71,256)	(61,845)
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 | 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		14,890,228	14,994,133
Liabilities measured at fair value		(82,987)	(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		(71,256)	(61,845)
Estimated Fair Value | Derivative instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	[1]	(11,731)	(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		10,301,572	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		2,833,849	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		837,680	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		1,760,384	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		832,159	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		1,899,868	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		786,276	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		1,351,356	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		701,623	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		875,727	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		377,677	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		89,611	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]	288,066	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]	20,142	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		2,613,487	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		682,569	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		58,565	22,190
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		89,168	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		23,868	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		167,698	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		248
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		1,158,567	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]	$ 432,804	$ 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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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		(66,461)	(43,156)	(61,845)	0
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	(4,795)	(9,943)	(8,343)	(11,337)
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		(71,256)	(53,099)	(71,256)	(53,099)
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 the contingent consideration liability 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	Jun. 30, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Total assets and liabilities measured at fair value	$ 14,970,000	$ 15,060,000
Total assets and liabilities measured at fair value priced using non-binding broker quotes	$ 301,700	$ 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	$ 791,222	$ 791,141
Reportable Legal Entities | ACGL (Parent Guarantor)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	296,834	296,796
Estimated fair value of senior notes	382,500
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	494,388	$ 494,345
Estimated fair value of senior notes	514,200
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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Derivative offsetting [Abstract]
Derivative assets subject to master netting agreements		$ 204,300		$ 204,300		$ 25,300
Derivative liabilities subject to master netting agreements		159,000		159,000		5,400
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments	[1]	(41,496)	$ 12,402	(4,820)	$ (366)
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives - fair value		223,664		223,664		26,468
Liability derivatives - fair value		(170,449)		(170,449)		(5,397)
Net derivatives - fair value		53,215		53,215		21,071
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(41,496)	12,402	(4,820)	(366)
Not Designated as Hedging Instrument [Member] | Futures contracts
Derivative [Line Items]
Net derivatives - fair value	[2]	(872)		(872)		249
Net derivatives - notional value	[2],[3]	1,683,928		1,683,928		2,549,027
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(31,446)	15,185	(12,120)	5,323
Not Designated as Hedging Instrument [Member] | Futures contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	192		192		2,156
Not Designated as Hedging Instrument [Member] | Futures contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(1,064)		(1,064)		(1,907)
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts
Derivative [Line Items]
Net derivatives - fair value	[2]	7,049		7,049		9,366
Net derivatives - notional value	[2],[3]	1,180,054		1,180,054		397,106
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(8,724)	(1,811)	8,095	(4,068)
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	14,452		14,452		10,511
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(7,403)		(7,403)		(1,145)
Not Designated as Hedging Instrument [Member] | TBAs
Derivative [Line Items]
Net derivatives - fair value	[4]	44,804		44,804		10,592
Net derivatives - notional value	[3],[4]	344,758		344,758		10,056
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(182)	(270)	304	(307)
Not Designated as Hedging Instrument [Member] | TBAs | Fixed maturities available for sale
Derivative [Line Items]
Asset derivatives - fair value	[4]	203,522		203,522		10,592
Liability derivatives - fair value	[4]	(158,718)		(158,718)		0
Not Designated as Hedging Instrument [Member] | Other
Derivative [Line Items]
Net derivatives - fair value	[2]	2,234		2,234		864
Net derivatives - notional value	[2],[3]	1,624,187		1,624,187		735,684
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(1,144)	$ (702)	(1,099)	$ (1,314)
Not Designated as Hedging Instrument [Member] | Other | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	5,498		5,498		3,209
Not Designated as Hedging Instrument [Member] | Other | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	$ (3,264)		$ (3,264)		$ (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	6 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Abstract]
Revolving credit agreement borrowings	$ 100,000		$ 100,000
Unfunded Investment Commitments [Abstract]
Investment commitments	1,120,000		$ 968,900
LOC Facilities [Member]
Line of Credit Facility [Abstract]
Letters of credit outstanding, amount	456,300
Investments pledged as collateral	521,900
Other secured letter of credit facilities
Line of Credit Facility [Abstract]
Maximum borrowing capacity	$ 229,400
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 Holdings Ltd | Line of credit
Line of Credit Facility [Abstract]
Maximum borrowing capacity	$ 100,000	$ 200,000
Credit facility expiration date	May 19, 2016
Letters of credit outstanding, amount	$ 36,500
Watford Holdings Ltd | Letter of credit
Line of Credit Facility [Abstract]
Maximum borrowing capacity	400,000
Watford Holdings Ltd | Other secured letter of credit facilities
Line of Credit Facility [Abstract]
Maximum borrowing capacity	$ 800,000
Line of Credit Facility, Initiation Date	Jun. 2, 2015
Credit facility expiration date	Jun. 4, 2018

Share Transactions - Share repu

Share Transactions - Share repurchases (Details) - Jun. 30, 2015 - Common shares - USD ($) shares in Millions, $ in Millions	Total	Total
Class of Stock [Line Items]
Cumulative number of shares acquired since inception of share repurchase program		124
Aggregate purchase price of shares acquired since inception of share repurchase program		$ 3,600
Treasury stock, shares acquired (shares)	3.2	5.9
Treasury stock, value of shares acquired	$ 199	$ 361.9
Remaining authorized repurchase amount	$ 525.3	$ 525.3

Share Transactions - Share-base

Share Transactions - Share-based compensation and LTIP (Details) - $ / shares	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Stock appreciation rights and options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock grant amount (in shares)	534,267	551,836
Weighted average grant date fair value (in dollars per share)	$ 16.09	$ 15.23
Restricted shares and units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock grant amount (in shares)	559,332	571,108
Weighted average grant date fair value (in dollars per share)	$ 62.51	$ 57.25
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for grants of awards	4,300,000
Maximum number of incentive stock options	2,000,000
Shares available for grant	3,235,680

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective tax rate on income before income taxes (percentage)	4.30%	2.70%
Net deferred tax assets	$ 143.9		$ 131
Income taxes paid	$ 26	$ 8.3

Other Comprehensive Income (L61

Other Comprehensive Income (Loss) - Amounts reclassified from accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses	$ (1,126)	$ (14,749)	$ (8,373)	$ (17,720)
Income before income taxes	132,599	219,006	454,034	401,889
Income tax expense	(6,780)	(7,289)	(19,458)	(11,027)
Net of tax	115,790	208,016	399,126	390,516
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	23,259	23,735	65,690	49,773
Other-than-temporary impairment losses	(1,126)	(14,749)	(8,373)	(17,720)
Income before income taxes	22,133	8,986	57,317	32,053
Income tax expense	(919)	(701)	(5,171)	(2,519)
Net of tax	$ 21,214	$ 8,285	$ 52,146	$ 29,534

Other Comprehensive Income (L62

Other Comprehensive Income (Loss) - Components of other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Before tax amount:
Unrealized holding gains (losses) arising during period, before tax	$ (96,629)	$ 115,150	$ (2,242)	$ 190,550
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), before tax	(13)	0	(1,461)	0
Less reclassification of net realized gains included in net income, before tax	22,133	8,986	57,317	32,053
Foreign currency translation adjustments, before tax	11,697	10,021	(11,929)	8,672
Other comprehensive income (loss), before tax	(107,078)	116,185	(72,949)	167,169
Tax expense (benefit):
Unrealized holding gains (losses) arising during period, tax	(14,694)	6,722	(4,611)	10,769
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	919	701	5,171	2,519
Foreign currency translation adjustments, tax	117	0	(752)	0
Other comprehensive income (loss), tax	(15,496)	6,021	(10,534)	8,250
Net of tax amount:
Unrealized holding gains (losses) arising during period, net of tax	(81,935)	108,428	2,369	179,781
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), net of tax	(13)	0	(1,461)	0
Less reclassification of net realized gains included in net income, net of tax	21,214	8,285	52,146	29,534
Foreign currency translation adjustments, net of tax	11,580	10,021	(11,177)	8,672
Net current period other comprehensive income (loss)	$ (91,582)	$ 110,164	$ (62,415)	$ 158,919

Guarantor Financial Informati63

Guarantor Financial Information - Condensed consolidating balance sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Assets
Total investments	$ 15,346,940	$ 15,320,770
Cash	525,074	485,702	$ 926,443	$ 434,057
Investments in subsidiaries	0	0
Due from subsidiaries and affiliates	0	0
Premiums receivable	1,181,636	948,695
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	1,831,227	1,812,845
Contractholder receivables	1,393,138	1,309,192
Prepaid reinsurance premiums	442,141	377,078
Deferred acquisition costs, net	448,647	414,525
Other assets	1,916,122	1,337,274
Total assets	23,084,925	22,006,081	22,567,447
Liabilities
Reserve for losses and loss adjustment expenses	9,082,281	9,036,448
Unearned premiums	2,442,923	2,231,578
Reinsurance balances payable	252,462	219,312
Contractholder payables	1,393,138	1,309,192
Deposit accounting liabilities	277,523	327,384
Senior notes	791,222	791,141
Revolving credit agreement borrowings	100,000	100,000
Due to subsidiaries and affiliates	0	0
Other liabilities	1,607,985	872,380
Total liabilities	15,947,534	14,887,435	15,326,382
Redeemable noncontrolling interests	204,996	219,512
Shareholders' Equity
Total shareholders’ equity available to Arch	6,137,515	6,130,053	6,229,399
Non-redeemable noncontrolling interests	794,880	769,081	792,340
Total shareholders’ equity	6,932,395	6,899,134	7,021,739
Total liabilities, noncontrolling interests and shareholders’ equity	23,084,925	22,006,081
Reportable Legal Entities | ACGL (Parent Guarantor)
Assets
Total investments	471	107
Cash	10,864	3,218	4,715	3,223
Investments in subsidiaries	6,530,452	6,536,644
Due from subsidiaries and affiliates	11	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	4,208	4,386
Total assets	6,546,006	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
Deposit accounting liabilities	0	0
Senior notes	296,834	296,796
Revolving credit agreement borrowings	100,000	100,000
Due to subsidiaries and affiliates	402	417
Other liabilities	11,255	17,137
Total liabilities	408,491	414,350
Redeemable noncontrolling interests	0	0
Shareholders' Equity
Total shareholders’ equity available to Arch	6,137,515	6,130,053
Non-redeemable noncontrolling interests	0	0
Total shareholders’ equity	6,137,515	6,130,053
Total liabilities, noncontrolling interests and shareholders’ equity	6,546,006	6,544,403
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Assets
Total investments	55,047	62,867
Cash	6,928	2,787	7,746	509
Investments in subsidiaries	1,688,419	1,685,185
Due from subsidiaries and affiliates	47,798	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	46,157	43,921
Total assets	1,844,349	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
Deposit accounting liabilities	0	0
Senior notes	494,388	494,345
Revolving credit agreement borrowings	0	0
Due to subsidiaries and affiliates	35,000	7,505
Other liabilities	44,917	49,403
Total liabilities	574,305	551,253
Redeemable noncontrolling interests	0	0
Shareholders' Equity
Total shareholders’ equity available to Arch	1,270,044	1,251,024
Non-redeemable noncontrolling interests	0	0
Total shareholders’ equity	1,270,044	1,251,024
Total liabilities, noncontrolling interests and shareholders’ equity	1,844,349	1,802,277
Reportable Legal Entities | Other ACGL Subsidiaries
Assets
Total investments	15,306,122	15,257,796
Cash	507,282	479,697	913,982	430,325
Investments in subsidiaries	0	0
Due from subsidiaries and affiliates	417,231	370,429
Premiums receivable	1,620,756	1,331,511
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	5,741,646	5,584,973
Contractholder receivables	1,393,138	1,309,192
Prepaid reinsurance premiums	1,595,550	1,373,008
Deferred acquisition costs, net	448,647	414,525
Other assets	2,274,796	1,705,546
Total assets	29,305,168	27,826,677
Liabilities
Reserve for losses and loss adjustment expenses	12,970,720	12,784,030
Unearned premiums	3,596,332	3,227,508
Reinsurance balances payable	678,216	589,289
Contractholder payables	1,393,138	1,309,192
Deposit accounting liabilities	495,121	587,050
Senior notes	0	0
Revolving credit agreement borrowings	0	0
Due to subsidiaries and affiliates	429,638	370,072
Other liabilities	1,778,600	1,000,138
Total liabilities	21,341,765	19,867,279
Redeemable noncontrolling interests	219,696	219,512
Shareholders' Equity
Total shareholders’ equity available to Arch	6,948,827	6,970,805
Non-redeemable noncontrolling interests	794,880	769,081
Total shareholders’ equity	7,743,707	7,739,886
Total liabilities, noncontrolling interests and shareholders’ equity	29,305,168	27,826,677
Consolidating Adjustments and Eliminations
Assets
Total investments	(14,700)	0
Cash	0	0	$ 0	$ 0
Investments in subsidiaries	(8,218,871)	(8,221,829)
Due from subsidiaries and affiliates	(465,040)	(377,994)
Premiums receivable	(439,120)	(382,816)
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses	(3,910,419)	(3,772,128)
Contractholder receivables	0	0
Prepaid reinsurance premiums	(1,153,409)	(995,930)
Deferred acquisition costs, net	0	0
Other assets	(409,039)	(416,579)
Total assets	(14,610,598)	(14,167,276)
Liabilities
Reserve for losses and loss adjustment expenses	(3,888,439)	(3,747,582)
Unearned premiums	(1,153,409)	(995,930)
Reinsurance balances payable	(425,754)	(369,977)
Contractholder payables	0	0
Deposit accounting liabilities	(217,598)	(259,666)
Senior notes	0	0
Revolving credit agreement borrowings	0	0
Due to subsidiaries and affiliates	(465,040)	(377,994)
Other liabilities	(226,787)	(194,298)
Total liabilities	(6,377,027)	(5,945,447)
Redeemable noncontrolling interests	(14,700)	0
Shareholders' Equity
Total shareholders’ equity available to Arch	(8,218,871)	(8,221,829)
Non-redeemable noncontrolling interests	0	0
Total shareholders’ equity	(8,218,871)	(8,221,829)
Total liabilities, noncontrolling interests and shareholders’ equity	$ (14,610,598)	$ (14,167,276)

Guarantor Financial Informati64

Guarantor Financial Information - Condensed consolidating statement of income and comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues
Net premiums earned	$ 943,438	$ 907,152	$ 1,853,702	$ 1,766,932
Net investment income	86,963	72,990	165,957	139,984
Net realized gains (losses)	(35,725)	54,144	47,623	73,841
Net impairment losses recognized in earnings	(1,113)	(14,749)	(6,912)	(17,720)
Other underwriting income	7,717	2,033	19,253	3,615
Equity in net income of investment funds accounted for using the equity method	16,167	9,240	22,056	12,493
Other income (loss)	2,205	4,850	317	2,746
Total revenues	1,019,652	1,035,660	2,101,996	1,981,891
Expenses
Losses and loss adjustment expenses	519,426	485,518	1,013,142	921,758
Acquisition expenses	175,425	158,158	338,501	318,500
Other operating expenses	168,608	156,350	326,490	302,149
Interest expense	4,011	14,334	16,747	28,738
Net foreign exchange losses (gains)	19,583	2,294	(46,918)	8,857
Total expenses	887,053	816,654	1,647,962	1,580,002
Income (loss) before income taxes	132,599	219,006	454,034	401,889
Income tax expense (benefit)	(6,780)	(7,289)	(19,458)	(11,027)
Income (loss) before equity in net income of subsidiaries	125,819	211,717	434,576	390,862
Equity in net income of subsidiaries	0	0	0	0
Net income	125,819	211,717	434,576	390,862
Amounts attributable to noncontrolling interests	(10,029)	(3,701)	(35,450)	(346)
Net income available to Arch	115,790	208,016	399,126	390,516
Preferred dividends	(5,485)	(5,485)	(10,969)	(10,969)
Net income (loss) available to Arch common shareholders	110,305	202,531	388,157	379,547
Comprehensive income (loss) available to Arch	24,208	318,180	336,711	549,435
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 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	16,900	15,250	25,532	25,557
Interest expense	5,862	5,854	11,718	11,707
Net foreign exchange losses (gains)	0	0	0	0
Total expenses	22,762	21,104	37,250	37,264
Income (loss) before income taxes	(22,762)	(21,104)	(37,250)	(37,264)
Income tax expense (benefit)	0	0	0	0
Income (loss) before equity in net income of subsidiaries	(22,762)	(21,104)	(37,250)	(37,264)
Equity in net income of subsidiaries	138,552	229,120	436,376	427,780
Net income	115,790	208,016	399,126	390,516
Amounts attributable to noncontrolling interests	0	0	0	0
Net income available to Arch	115,790	208,016	399,126	390,516
Preferred dividends	(5,485)	(5,485)	(10,969)	(10,969)
Net income (loss) available to Arch common shareholders	110,305	202,531	388,157	379,547
Comprehensive income (loss) available to Arch	24,208	318,180	336,711	549,435
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Revenues
Net premiums earned	0	0	0	0
Net investment income	800	0	805	0
Net realized gains (losses)	1	0	1	0
Net impairment losses recognized in earnings	0	0	0	0
Other underwriting income	0	0	0	0
Equity in net income of investment funds accounted for using the equity method	0	0	0	0
Other income (loss)	0	0	0	0
Total revenues	801	0	806	0
Expenses
Losses and loss adjustment expenses	0	0	0	0
Acquisition expenses	0	0	0	0
Other operating expenses	1,012	494	2,271	1,471
Interest expense	6,769	6,448	13,135	12,962
Net foreign exchange losses (gains)	0	0	0	0
Total expenses	7,781	6,942	15,406	14,433
Income (loss) before income taxes	(6,980)	(6,942)	(14,600)	(14,433)
Income tax expense (benefit)	3,697	3,294	5,110	6,082
Income (loss) before equity in net income of subsidiaries	(3,283)	(3,648)	(9,490)	(8,351)
Equity in net income of subsidiaries	14,077	9,334	28,572	31,486
Net income	10,794	5,686	19,082	23,135
Amounts attributable to noncontrolling interests	0	0	0	0
Net income available to Arch	10,794	5,686	19,082	23,135
Preferred dividends	0	0	0	0
Net income (loss) available to Arch common shareholders	10,794	5,686	19,082	23,135
Comprehensive income (loss) available to Arch	(13,505)	23,186	(1,755)	40,406
Reportable Legal Entities | Other ACGL Subsidiaries
Revenues
Net premiums earned	943,438	907,152	1,853,702	1,766,932
Net investment income	87,154	80,380	173,164	157,381
Net realized gains (losses)	(35,726)	54,144	47,622	73,841
Net impairment losses recognized in earnings	(1,113)	(14,749)	(6,912)	(17,720)
Other underwriting income	7,717	2,033	19,253	3,615
Equity in net income of investment funds accounted for using the equity method	16,167	9,240	22,056	12,493
Other income (loss)	2,205	4,850	317	2,746
Total revenues	1,019,842	1,043,050	2,109,202	1,999,288
Expenses
Losses and loss adjustment expenses	519,426	485,518	1,013,142	921,758
Acquisition expenses	175,425	158,158	338,501	318,500
Other operating expenses	150,696	140,606	298,687	275,121
Interest expense	(7,793)	9,422	(258)	21,466
Net foreign exchange losses (gains)	6,942	1,054	(32,688)	6,795
Total expenses	844,696	794,758	1,617,384	1,543,640
Income (loss) before income taxes	175,146	248,292	491,818	455,648
Income tax expense (benefit)	(10,477)	(10,583)	(24,568)	(17,109)
Income (loss) before equity in net income of subsidiaries	164,669	237,709	467,250	438,539
Equity in net income of subsidiaries	0	0	0	0
Net income	164,669	237,709	467,250	438,539
Amounts attributable to noncontrolling interests	(10,193)	(3,701)	(35,614)	(346)
Net income available to Arch	154,476	234,008	431,636	438,193
Preferred dividends	0	0	0	0
Net income (loss) available to Arch common shareholders	154,476	234,008	431,636	438,193
Comprehensive income (loss) available to Arch	50,249	335,348	383,442	587,467
Consolidating Adjustments and Eliminations
Revenues
Net premiums earned	0	0	0	0
Net investment income	(991)	(7,390)	(8,012)	(17,397)
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 of investment funds accounted for using the equity method	0	0	0	0
Other income (loss)	0	0	0	0
Total revenues	(991)	(7,390)	(8,012)	(17,397)
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	(827)	(7,390)	(7,848)	(17,397)
Net foreign exchange losses (gains)	12,641	1,240	(14,230)	2,062
Total expenses	11,814	(6,150)	(22,078)	(15,335)
Income (loss) before income taxes	(12,805)	(1,240)	14,066	(2,062)
Income tax expense (benefit)	0	0	0	0
Income (loss) before equity in net income of subsidiaries	(12,805)	(1,240)	14,066	(2,062)
Equity in net income of subsidiaries	(152,629)	(238,454)	(464,948)	(459,266)
Net income	(165,434)	(239,694)	(450,882)	(461,328)
Amounts attributable to noncontrolling interests	164	0	164	0
Net income available to Arch	(165,270)	(239,694)	(450,718)	(461,328)
Preferred dividends	0	0	0	0
Net income (loss) available to Arch common shareholders	(165,270)	(239,694)	(450,718)	(461,328)
Comprehensive income (loss) available to Arch	$ (36,744)	$ (358,534)	$ (381,687)	$ (627,873)

Guarantor Financial Informati65

Guarantor Financial Information - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 385,199	$ 453,063
Investing Activities
Purchases of fixed maturity investments	(14,641,391)	(14,311,748)
Purchases of equity securities	(288,535)	(174,687)
Purchases of other investments	(1,273,780)	(1,022,987)
Proceeds from the sale of fixed maturity investments	14,355,519	13,204,854
Proceeds from the sale of equity securities	272,343	98,687
Proceeds from sales, redemptions and maturities of other investments	1,078,675	618,707
Proceeds from redemptions and maturities of fixed maturity investments	474,984	432,040
Proceeds from investment in joint venture	40,000	0
Net (purchases) sales of short-term investments	3,707	430,304
Change in cash collateral related to securities lending	(18,329)	18,701
Contributions to subsidiaries	0	0
Intercompany loans issued	0	0
Purchase of business, net of cash acquired	818	(235,578)
Purchases of furniture, equipment and other assets	(43,165)	(10,360)
Net Cash Used For Investing Activities	(39,154)	(952,067)
Financing Activities
Purchases of common shares under share repurchase program	(361,877)	0
Proceeds from common shares issued, net	2,178	2,521
Proceeds from intercompany borrowings	0
Repayments of intercompany borrowings		0
Change in cash collateral related to securities lending	18,329	(18,701)
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	(9,313)	(4,816)
Dividends paid to parent	0	0
Other	55,018	4,706
Preferred dividends paid	(10,969)	(10,969)
Net Cash Provided By (Used For) Financing Activities	(306,634)	988,877
Effects of exchange rate changes on foreign currency cash	(39)	2,513
Increase (decrease) in cash	39,372	492,386
Cash beginning of year	485,702	434,057
Cash end of period	525,074	926,443
Reportable Legal Entities | ACGL (Parent Guarantor)
Operating Activities
Net Cash Provided by (Used in) Operating Activities	378,703	10,099
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
Proceeds from investment in joint venture	0
Net (purchases) sales of short-term investments	(365)	(31)
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 furniture, equipment and other assets	(24)	(128)
Net Cash Used For Investing Activities	(389)	(159)
Financing Activities
Purchases of common shares under share repurchase program	(361,877)
Proceeds from common shares issued, net	2,178	2,521
Proceeds from intercompany 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	(10,969)	(10,969)
Net Cash Provided By (Used For) Financing Activities	(370,668)	(8,448)
Effects of exchange rate changes on foreign currency cash	0	0
Increase (decrease) in cash	7,646	1,492
Cash beginning of year	3,218	3,223
Cash end of period	10,864	4,715
Reportable Legal Entities | Arch-U.S. (Subsidiary Issuer)
Operating Activities
Net Cash Provided by (Used in) Operating Activities	8,282	424
Investing Activities
Purchases of fixed maturity investments	0	(78,509)
Purchases of equity securities	0	0
Purchases of other investments	0	0
Proceeds from the sale of fixed maturity investments	20,002	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
Proceeds from investment in joint venture	0
Net (purchases) sales of short-term investments	(12,171)	408,779
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 furniture, equipment and other assets	0	0
Net Cash Used For Investing Activities	(31,669)	17,063
Financing Activities
Purchases of common shares under share repurchase program	0
Proceeds from common shares issued, net	0	0
Proceeds from intercompany borrowings	27,500
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	4,141	7,237
Cash beginning of year	2,787	509
Cash end of period	6,928	7,746
Reportable Legal Entities | Other ACGL Subsidiaries
Operating Activities
Net Cash Provided by (Used in) Operating Activities	433,833	474,565
Investing Activities
Purchases of fixed maturity investments	(14,641,391)	(14,233,239)
Purchases of equity securities	(288,535)	(174,687)
Purchases of other investments	(1,273,780)	(1,022,987)
Proceeds from the sale of fixed maturity investments	14,335,517	13,204,854
Proceeds from the sale of equity securities	272,343	98,687
Proceeds from sales, redemptions and maturities of other investments	1,078,675	618,707
Proceeds from redemptions and maturities of fixed maturity investments	474,984	432,040
Proceeds from investment in joint venture	40,000
Net (purchases) sales of short-term investments	16,243	21,556
Change in cash collateral related to securities lending	(18,329)	18,701
Contributions to subsidiaries	(9,290)	(100,000)
Intercompany loans issued	(27,500)	10,250
Purchase of business, net of cash acquired	818	(235,578)
Purchases of furniture, equipment and other assets	(43,141)	(10,232)
Net Cash Used For Investing Activities	(83,386)	(1,371,928)
Financing Activities
Purchases of common shares under share repurchase program	0
Proceeds from common shares issued, net	9,290	413,207
Proceeds from intercompany borrowings	39,500
Repayments of intercompany borrowings		0
Change in cash collateral related to securities lending	18,329	(18,701)
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	(9,632)	(4,816)
Dividends paid to parent	(435,300)	(32,025)
Other	54,990	4,706
Preferred dividends paid	0	0
Net Cash Provided By (Used For) Financing Activities	(322,823)	1,378,507
Effects of exchange rate changes on foreign currency cash	(39)	2,513
Increase (decrease) in cash	27,585	483,657
Cash beginning of year	479,697	430,325
Cash end of period	507,282	913,982
Consolidating Adjustments and Eliminations
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(435,619)	(32,025)
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
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	67,000	(10,250)
Purchase of business, net of cash acquired	0	0
Purchases of furniture, equipment and other assets	0	0
Net Cash Used For Investing Activities	76,290	402,957
Financing Activities
Purchases of common shares under share repurchase program	0
Proceeds from common shares issued, net	(9,290)	(413,207)
Proceeds from intercompany borrowings	(67,000)
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	319	0
Dividends paid to parent	435,300	32,025
Other	0	0
Preferred dividends paid	0	0
Net Cash Provided By (Used For) Financing Activities	359,329	(370,932)
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 Par66

Transactions with Related Parties (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Related Party Transaction [Line Items]
Investment commitments	$ 1,120,000		$ 1,120,000		$ 968,900
Purchases of other investments			1,273,780	$ 1,022,987
Common director | The Carlyle Group
Related Party Transaction [Line Items]
Investment commitments	670,900		670,900
Unfunded commitments	374,100		$ 374,100
Purchases of other investments	25,600	$ 29,800
Aggregate distributions received	$ 19,800	$ 37,200