James River (JRVR) 10-K 27 Feb 20 2019 FY Annual report Financial data

Cover

Cover - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 25, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Entity File Number	001-36777
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity Registrant Name	JAMES RIVER GROUP HOLDINGS, LTD.
Title of 12(b) Security	Common Shares, par value $0.0002 per share
City Area Code	441
Entity Incorporation, State or Country Code	D0
Entity Central Index Key	0001620459
Trading Symbol	JRVR
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding		30,520,337
Entity Public Float			$ 1,383,652,430
Amendment Flag	false
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Entity Tax Identification Number	98-0585280
Local Phone Number	278-4580
Security Exchange Name	NASDAQ
Entity Address, Address Line Three	Wellesley House
Entity Address, Address Line Two	2nd Floor
Entity Address, Address Line One	90 Pitts Bay Road
Entity Address, City or Town	Pembroke
Entity Address, Postal Zip Code	HM08
Entity Address, Country	BM
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE: Portions of the James River Group Holdings, Ltd. Proxy Statement to be filed with the Securities and Exchange Commission within 120 days after the year covered by this Form 10-K with respect to the 2020 Annual General Meeting of Shareholders are incorporated by reference into Part III hereof.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fixed maturity securities:
Available-for-sale, at fair value (amortized cost: 2019 – $1,398,533; 2018 – $1,199,409)	$ 1,433,626	$ 1,184,202
Equity securities, at fair value (cost: 2019 – $73,244; 2018 – $77,152)	80,735	78,385
Bank loan participations held-for-investment, at amortized cost, net of allowance	260,864	260,972
Short-term investments	156,925	81,966
Other invested assets	61,210	72,321
Total invested assets	1,993,360	1,677,846
Cash and cash equivalents	206,912	172,457
Restricted cash equivalents	1,199,164	0
Accrued investment income	13,597	11,110
Premiums receivable and agents’ balances, net	369,462	307,899
Reinsurance recoverable on unpaid losses	668,045	467,371
Reinsurance recoverable on paid losses	33,221	18,344
Prepaid reinsurance premiums	178,976	112,498
Deferred policy acquisition costs	62,006	54,450
Intangible assets, net	36,940	37,537
Goodwill	181,831	181,831
Deferred tax assets, net	664	1,054
Other assets	80,227	94,379
Total assets	5,024,405	3,136,776
Liabilities:
Reserve for losses and loss adjustment expenses	2,045,506	1,661,459
Unearned premiums	524,377	386,473
Payables to reinsurers	108,059	61,662
Funds held	1,199,164	0
Senior debt	158,300	118,300
Junior subordinated debt	104,055	104,055
Accrued expenses	58,416	51,792
Income taxes payable	1,483	1,915
Other liabilities	46,464	41,879
Total liabilities	4,245,824	2,427,535
Commitments and contingent liabilities
Shareholders’ equity:
Common Shares – $0.0002 par value; 200,000,000 shares authorized. 2019 and 2018: 30,424,391 and 29,988,460 shares issued and outstanding, respectively	6	6
Preferred Shares – 2019 and 2018: $0.00125 par value; 20,000,000 shares authorized; no shares issued and outstanding	0	0
Additional paid-in capital	657,875	645,310
Retained earnings	89,586	79,753
Accumulated other comprehensive income (loss)	31,114	(15,828)
Total shareholders’ equity	778,581	709,241
Total liabilities and shareholders’ equity	$ 5,024,405	$ 3,136,776

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Available-for-sale debt securities, amortized cost (in dollars)	$ 1,398,533	$ 1,199,409
Equity securities, amortized cost	$ 73,244	$ 77,512
Common stock, par value (in dollars per share)	$ 0.0002	$ 0.0002
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	30,424,391	29,988,460
Common stock, shares outstanding	30,424,391	29,988,460
Preferred stock par value (in dollars per share)	$ 0.00125	$ 0.00125
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Consolidated Statements of Inco

Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Gross written premiums	$ 1,470,735	$ 1,166,773	$ 1,081,905
Ceded written premiums	(574,585)	(404,101)	(315,279)
Net written premiums	896,150	762,672	766,626
Change in net unearned premiums	(72,404)	52,726	(25,517)
Net earned premiums	823,746	815,398	741,109
Net investment income	75,652	61,256	61,119
Net realized and unrealized losses on investments	(2,919)	(5,479)	(1,989)
Other income	10,646	14,424	17,386
Total revenues	907,125	885,599	817,625
Expenses:
Losses and loss adjustment expenses	672,102	600,276	555,377
Other operating expenses	170,908	201,035	196,993
Other expenses	1,055	1,300	539
Interest expense	10,596	11,553	8,974
Amortization of intangible assets	597	597	597
Total expenses	855,258	814,761	762,480
Income before income taxes	51,867	70,838	55,145
Income tax expense (benefit):
Current	18,453	12,867	11,943
Deferred	(4,925)	(5,859)	(364)
Total income tax expense	13,528	7,008	11,579
Net income	38,339	63,830	43,566
Other comprehensive income (losses):
Net unrealized gains (losses), net of taxes of $3,358 in 2019, $(444) in 2018, and $2,707 in 2017	46,942	(22,203)	9,219
Total comprehensive income	$ 85,281	$ 41,627	$ 52,785
Per share data:
Basic earnings per share (in dollars per share)	$ 1.27	$ 2.14	$ 1.48
Diluted earnings per share (in dollars per share)	1.25	2.11	1.44
Dividend declared per share (in dollars per share)	$ 1.20	$ 1.20	$ 1.70
Weighted-average common shares outstanding:
Basic (in shares)	30,275,184	29,887,990	29,461,717
Diluted (in shares)	30,673,924	30,307,101	30,273,149

Consolidated Statements of In_2

Consolidated Statements of Income and Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Tax on net unrealized gains (losses)	$ 3,358	$ (444)	$ 2,707

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($)	Total	Common Shares	Preferred stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balances at Dec. 31, 2016	$ 693,221,000	$ 6,000	$ 0	$ 636,856,000	$ 55,232,000	$ 1,127,000
Balances (in shares) at Dec. 31, 2016		29,257,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,566,000				43,566,000
Other comprehensive income (loss)	9,219,000					9,219,000
Dividends	(50,600,000)				(50,600,000)
Exercise of stock options	(6,213,000)			(6,213,000)
Vesting of RSUs and related excess tax benefits (in shares)		80,149
Vesting of RSUs and related excess tax benefits	(2,182,000)			(2,182,000)
Exercise of stock options (in shares)		358,967
Compensation expense under share incentive plans	7,688,000			7,688,000
Balances at Dec. 31, 2017	$ 694,699,000	$ 6,000	0	636,149,000	48,198,000	10,346,000
Balances (in shares) at Dec. 31, 2017	29,696,682	29,696,682
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 15,633,000
Balances at Dec. 31, 2017	$ 694,699,000	$ 6,000	0	636,149,000	48,198,000	10,346,000
Balances (in shares) at Dec. 31, 2017	29,696,682	29,696,682
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 63,830,000				63,830,000
Other comprehensive income (loss)	(22,203,000)					(22,203,000)
Dividends	(36,246,000)				(36,246,000)
Exercise of stock options	4,045,000			4,045,000
Exercise of stock options (in shares)		237,319
Vesting of RSUs	(1,112,000)			(1,112,000)
Vesting of RSUs (in shares)		54,459
Compensation expense under share incentive plans	6,228,000			6,228,000
Balances at Dec. 31, 2018	$ 709,241,000	$ 6,000	0	645,310,000	79,753,000	(15,828,000)
Balances (in shares) at Dec. 31, 2018	29,988,460	29,988,460
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 38,339,000				38,339,000
Other comprehensive income (loss)	46,942,000					46,942,000
Dividends	(36,786,000)				(36,786,000)
Exercise of stock options	7,124,000			7,124,000
Exercise of stock options (in shares)		345,434
Vesting of RSUs	(1,737,000)			(1,737,000)
Vesting of RSUs (in shares)		90,497
Compensation expense under share incentive plans	7,178,000			7,178,000
Balances at Dec. 31, 2019	$ 778,581,000	$ 6,000	$ 0	$ 657,875,000	$ 89,586,000	$ 31,114,000
Balances (in shares) at Dec. 31, 2019	30,424,391	30,424,391

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 38,339,000	$ 63,830,000	$ 43,566,000
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred policy acquisition costs	(91,449,000)	(93,188,000)	(123,577,000)
Amortization of policy acquisition costs	83,893,000	111,103,000	116,001,000
Net realized investment losses	2,919,000	5,479,000	1,989,000
Impairment of intangible assets	0	200,000	0
Distributions from equity method investments	2,834,000	7,499,000	7,333,000
Income from equity method investments	(4,598,000)	(3,540,000)	(13,209,000)
Trading securities purchases, sales, and maturities, net	0	3,804,000	1,250,000
Deferred U.S. federal income tax benefit	(4,925,000)	(5,859,000)	(364,000)
Provision for depreciation and amortization	4,063,000	4,215,000	2,123,000
Share based compensation expense	7,178,000	6,228,000	7,688,000
Excess tax benefits from equity incentive plan transactions	(1,099,000)	(2,699,000)	(2,115,000)
Change in operating assets and liabilities:
Reserve for losses and loss adjustment expenses	384,047,000	369,110,000	348,484,000
Unearned premiums	137,904,000	(31,641,000)	27,551,000
Premiums receivable and agents’ balances	(61,563,000)	44,537,000	(87,121,000)
Reinsurance balances	(235,632,000)	(187,024,000)	(113,665,000)
Funds held	1,199,164,000	0	0
Payable to insurance companies	263,000	(2,029,000)	445,000
Other	27,684,000	3,000	(8,563,000)
Net cash provided by operating activities	1,489,022,000	290,028,000	207,816,000
Securities available-for-sale:
Purchases – fixed maturity securities	(450,793,000)	(418,011,000)	(270,014,000)
Sales – fixed maturity securities	121,245,000	95,793,000	77,781,000
Maturities and calls – fixed maturity securities	128,809,000	129,139,000	121,890,000
Purchases – equity securities	(4,975,000)	(7,507,000)	(5,540,000)
Sales – equity securities	8,656,000	5,578,000	3,522,000
Bank loan participations:
Purchases	(102,794,000)	(203,328,000)	(240,799,000)
Sales	48,415,000	123,114,000	138,214,000
Maturities	45,277,000	58,742,000	69,740,000
Other invested assets:
Purchases	0	(6,993,000)	(8,913,000)
Return of capital	1,877,000	921,000	0
Redemptions	10,998,000	0	0
Securities receivable or payable, net	5,404,000	2,268,000	(2,525,000)
Short-term investments, net	(74,959,000)	(45,162,000)	14,040,000
Other	(519,000)	(1,326,000)	(2,137,000)
Net cash used in investing activities	(263,359,000)	(266,772,000)	(104,741,000)
Financing activities
Senior debt issuances	60,000,000	20,000,000	10,000,000
Senior debt repayments	(20,000,000)	0	0
Dividends paid	(36,720,000)	(36,123,000)	(50,832,000)
Issuances of common shares under equity incentive plans	8,286,000	5,172,000	1,708,000
Common share repurchases	(2,899,000)	(2,239,000)	(9,448,000)
Other financing activities	(711,000)	(1,104,000)	(792,000)
Net cash provided by (used in) financing activities	7,956,000	(14,294,000)	(49,364,000)
Change in cash, cash equivalents, and restricted cash equivalents	1,233,619,000	8,962,000	53,711,000
Cash and cash equivalents at beginning of year	172,457,000	163,495,000	109,784,000
Cash, cash equivalents ($206,912), and restricted cash equivalents ($1,199,164) at end of year	1,406,076,000	172,457,000	163,495,000
Supplemental information
U.S. federal income taxes paid, net	18,719,000	8,174,000	9,848,000
Interest paid	$ 12,354,000	$ 11,269,000	$ 8,909,000

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) $ in Thousands	Dec. 31, 2019USD ($)
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 206,912
Restricted equivalents	$ 1,199,164

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies ​ Organization James River Group Holdings, Ltd. (referred to as “JRG Holdings” or, with its subsidiaries, the “Company”) is an exempted holding company registered in Bermuda, organized for the purpose of acquiring and managing insurance and reinsurance entities. The Company owns five insurance companies based in the United States (“U.S.”) focused on specialty insurance niches and two Bermuda-based reinsurance companies as described below: • James River Group Holdings UK Limited (“James River UK”) is an insurance holding company formed in 2015 in the United Kingdom (“U.K.”). The Company contributed James River Group, Inc. (“James River Group”), a U.S. insurance holding company, to James River UK in 2015. ​ • James River Group is a Delaware domiciled insurance holding company formed in 2002, which owns all of the Company’s U.S.-based subsidiaries, either directly or indirectly through one of its wholly-owned U.S. subsidiaries. James River Group oversees the Company’s U.S. insurance operations and maintains all of the outstanding debt in the U.S. ​ • James River Insurance Company (“James River Insurance”) is an Ohio domiciled excess and surplus lines insurance company that, with its wholly-owned insurance subsidiary, James River Casualty Company, is authorized to write business in every state and the District of Columbia. ​ • Falls Lake National Insurance Company (“Falls Lake National”) is an Ohio domiciled insurance company which wholly owns Stonewood Insurance Company (“Stonewood Insurance”), a North Carolina domiciled company, and Falls Lake Fire and Casualty Company, a California domiciled company. Falls Lake National began writing specialty admitted fronting and program business in late 2013. Falls Lake Fire and Casualty Company began operations in 2016. ​​ • JRG Reinsurance Company Ltd. (“JRG Re”) was formed in 2007 and commenced operations in 2008. JRG Re, a Bermuda domiciled reinsurer, primarily provides non-catastrophe casualty reinsurance to U.S. third parties and to the Company’s U.S.-based insurance subsidiaries. • Carolina Re Ltd ("Carolina Re") was formed in 2018 and provides reinsurance to the Company's U.S.-based insurance subsidiaries. Carolina Re is also the cedent on a stop loss reinsurance treaty with JRG Re. ​ Basis of Presentation and Principles of Consolidation The consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“GAAP”), which vary in some respects from statutory accounting practices (“SAP”) which are prescribed or permitted by the various state insurance departments in the U.S. or by insurance regulators in Bermuda. The accompanying consolidated financial statements include the accounts and operations of the Company and its subsidiaries. Intercompany transactions and balances have been eliminated. Estimates and Assumptions Preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying disclosures. Those estimates are inherently subject to change, and actual results may ultimately differ from those estimates. Fixed Maturity and Equity Securities Fixed maturity securities classified as “available-for-sale” are carried at fair value, and unrealized gains and losses on such securities, net of any deferred taxes, are reported as a separate component of accumulated other comprehensive income. Fixed maturity securities purchased for short-term resale are classified as “trading” and are carried at fair value with unrealized gains and losses included in earnings as a component of net investment income. The Company does not have any securities classified as “held-to-maturity”. Fair value generally represents quoted market value prices for securities traded in the public marketplace or prices analytically determined using bid or closing prices for securities not traded in the public marketplace. Premiums and discounts on mortgage-backed securities and asset-backed securities are amortized or accrued using the constant yield method which considers anticipated prepayments at the date of purchase. To the extent that the estimated lives of such securities change as a result of changes in estimated prepayment rates, the adjustments are included in net investment income using the retrospective method. Realized investment gains or losses are determined on a specific identification basis. Interest income is recognized as earned, and dividend income is recognized on the ex-dividend date. The Company evaluates its available-for-sale fixed maturity securities regularly to determine whether there are declines in value that are other-than-temporary. The Company’s outside investment managers assist the Company in this evaluation. When the Company determines that a security has experienced an other-than-temporary impairment, the impairment loss is recognized as a realized investment loss. The factors that the Company considers in evaluating whether such an other-than-temporary impairment has occurred include the amount and percentage that fair value is below amortized cost and the length of time that fair value has been below amortized cost. In addition, the Company considers the credit quality rating of the security, with a special emphasis on securities downgraded below investment grade. Management does not intend to sell available-for-sale fixed maturity securities in an unrealized loss position, and it is not “more likely than not” that the Company will be required to sell these securities before a recovery in fair value to their amortized cost basis occurs. Effective January 1, 2018, with the adoption of ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , equity securities (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) are measured at fair value with changes in fair value recognized in net realized and unrealized gains or losses. Prior to the adoption of ASU 2016-01, changes in the fair value of equity securities were recognized net of taxes as a component of accumulated other comprehensive income. Bank Loan Participations Held-for-Investment and Allowance for Credit Losses Bank loan participations held-for-investment are managed by a specialized outside investment manager and are generally stated at their outstanding unpaid principal balances net of unamortized premiums or discounts and net of any allowance for credit losses. Interest income is accrued on the unpaid principal balance. Discounts and premiums are amortized to income using the interest method. Generally, the accrual of interest on a bank loan participation is discontinued when the contractual payment of principal or interest has become 90 days past due or management has serious doubts about further collectability of principal or interest. A bank loan participation may remain on accrual status if it is in the process of collection and is either guaranteed or well secured. Interest received on nonaccrual loans generally is reported as investment income. There were no bank loans on nonaccrual status at December 31, 2019 or 2018 . Generally, bank loan participations are restored to accrual status when the obligation is brought current, has performed in accordance with the contractual terms for a reasonable period of time, and the ultimate collectability of the total contractual principal and interest is no longer in doubt. ​ The allowance for credit losses is maintained at a level believed adequate by management to absorb estimated probable credit losses. Management’s periodic evaluation of the adequacy of the allowance is based on consultations and advice of the Company’s specialized investment manager, known and inherent risks in the portfolio, adverse situations that may affect the borrower’s ability to repay, the estimated value of any underlying collateral, current economic conditions, and other relevant factors. When an observable market price for a loan is available, the Company has recorded an allowance equal to the difference between the fair value and the amortized cost of bank loans that it has determined to be impaired as a practical expedient for an estimate of probable future cash flows to be collected on those bank loans. If an observable market price for a loan is not available, the Company records an allowance equal to the difference between the present value of expected future cash flows discounted at the loan’s effective interest rate and the amortized cost of the loan. Bank loans are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. Other Invested Assets Other invested assets at December 31, 2019 and 2018 include the Company’s interests in private debt and equity investments. The investments are primarily focused in renewable energy, limited partnerships, and bank holding companies. Equity interests in various limited liability companies (“LLCs”) and limited partnerships are accounted for under the equity method, as the Company has determined that the equity method best reflects its economic interest in the underlying equity investment. Short-Term Investments Short-term investments are carried at amortized cost, which approximates fair value. Short-term investments have maturities greater than three months but less than one year at the date of purchase. Cash Equivalents The Company considers highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. Restricted Cash Equivalents The Company considers highly liquid investments with maturities of three months or less at the date of purchase that are segregated for a specific use to be restricted cash equivalents. Direct Written Premiums Direct written premiums are earned on a pro rata basis over the terms of the policies, generally 12 months. The portion of premiums written applicable to the unexpired terms of the policies in force is recorded as unearned premiums. Policies are accounted for on an individual basis, with no aggregation by counterparty. Assumed Reinsurance Premiums Assumed reinsurance written premiums include amounts reported by brokers and ceding companies, supplemented by the Company’s own estimates of premiums when reports have not been received. Premiums on the Company’s excess of loss and pro rata reinsurance contracts are estimated when the business is underwritten. For excess of loss contracts, the deposit premium, as defined in the contract, is generally recorded as an estimate of premiums written at the inception date of the treaty. Estimates of premiums written under pro rata contracts are recorded in the period in which the underlying risks are expected to begin and are based on information provided by the brokers and the ceding companies. Reinsurance premium estimates are reviewed by management periodically. Any adjustment to these estimates is recorded in the period in which it becomes known. ​ Reinsurance premiums assumed are earned over the terms of the underlying policies or reinsurance contracts. Contracts and policies written on a “losses occurring” basis cover claims that may occur during the term of the contract or policy, which is typically 12 months. Accordingly, the premium is earned evenly over the term. Contracts which are written on a “risks attaching” basis cover claims which attach to the underlying insurance policies written during the terms of such contracts. Premiums earned on such contracts usually extend beyond the original term of the reinsurance contract, typically resulting in recognition of premiums earned over a 24-month period in proportion to the level of underlying exposure. Contracts are accounted for on an individual basis, with no aggregation by counterparty. Premiums Receivable and Agents’ Balances, Net Premiums receivable and agents’ balances are carried at face value net of any allowance for doubtful accounts. The allowance for doubtful accounts represents an estimate of amounts considered uncollectible based on the Company’s assessment of the collectability of receivables that are past due. Receivables greater than 90 days past due were $3.3 million and $4.5 million at December 31, 2019 and 2018 , respectively. The allowance for doubtful accounts was $5.7 million and $3.9 million at December 31, 2019 and 2018 , respectively. Bad debt expense was $2.5 million for the year ended December 31, 2019 , $1.5 million for the year ended December 31, 2018 , and $1.0 million for the year ended December 31, 2017 . Receivables written off against the allowance for doubtful accounts totaled $812,000 for the year ended December 31, 2019 , $313,000 for the year ended December 31, 2018 , and $408,000 for the year ended December 31, 2017 . Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. Deferred Policy Acquisition Costs Costs which are incrementally or directly related to the successful acquisition of new or renewal insurance business are deferred. These deferred costs are primarily commissions to agents, ceding commissions paid on reinsurance assumed, premium taxes, and the portion of underwriting fixed compensation and payroll related fringe benefits directly related to an insurance contract that has been acquired, net of ceding commissions related to reinsurance ceded. Amortization of such policy acquisition costs is charged to expense in proportion to premium earned over the estimated policy life. To the extent that unearned premiums on existing policies are not adequate to cover projected related costs and expenses, deferred policy acquisition costs are charged to earnings. The Company considers anticipated investment income in determining whether a premium deficiency exists. Reinsurance and Adjustable Features of Insurance and Reinsurance Contracts Certain premiums and losses are ceded to other insurance companies or assumed from other insurance companies under various excess of loss and quota-share reinsurance contracts. The Company enters into ceded reinsurance contracts to limit its exposure to large losses, to limit exposure on new lines of insurance written by the Company, and to provide additional capacity for growth. Premiums, commissions, and losses and loss adjustment expenses on reinsured business are accounted for on a basis consistent with that used in accounting for the original policies issued and the terms of the reinsurance contracts. Reinsurance recoverables and prepaid reinsurance premiums are reported as assets. Other amounts payable to insurance companies and reinsurers or receivable from insurance companies and reinsurers are netted where the right of offset exists. The Company receives ceding commissions in connection with certain ceded reinsurance. The ceding commissions are recorded as a reduction of other operating expenses. Certain reinsurance contracts include provisions that adjust premiums or acquisition expenses based upon the loss experience under the contracts. Premiums written and earned, as well as related acquisition expenses are recorded based upon the projected loss experience under the contracts. The Company’s Specialty Admitted Insurance segment writes insurance under specialty admitted fronting and program arrangements. The fronting and program arrangements may contain contractual provisions that adjust acquisition expenses based upon loss experience under the contracts. The specialty admitted fronting and program arrangements are significantly reinsured. These reinsurance contracts may also contain provisions that adjust premiums or acquisition expenses based upon the loss experience under the contracts. Premiums written and earned, as well as related acquisition expenses, are recorded based upon the projected experience under the contracts. Other Income Other income is principally comprised of fee income earned on policies for which the Company has no exposure to underwriting risk. Fee income of $9.1 million , $13.9 million , and $17.0 million is included in other income for the years ended December 31, 2019 , 2018 , and 2017 , respectively. Fees are earned on a pro rata basis over the service period of the underlying business. Policies are accounted for on an individual basis, with no aggregation by counterparty. Income Taxes Deferred tax assets and deferred tax liabilities are provided for the future tax consequences attributable to temporary differences between the financial statement carrying amounts of assets and liabilities and their respective U.S. tax basis. Deferred tax assets and liabilities are measured using enacted U.S. corporate tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Deferred tax assets are reduced by a valuation allowance only when management believes it is more likely than not that some, or all, of the deferred tax assets will not be realized. Effective January 1, 2018, the Company adopted ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This update was issued as a result of the enactment of Public Law No. 115-97, informally titled the Tax Cuts and Jobs Act (the "Tax Act"), on December 22, 2017. The ASU allows for the option to reclassify the stranded tax effects resulting from the implementation of the Tax Act out of accumulated other comprehensive income and into retained earnings. The reclassification resulted in a $711,000 decrease to the Company's retained earnings with a corresponding increase to accumulated other comprehensive income in the first quarter of 2018. Goodwill Goodwill is tested annually for impairment in the fourth quarter of each calendar year, or more frequently if events or changes in circumstances indicate that the carrying amount of the Company’s reporting units, including goodwill, may exceed their fair values. The Company first assesses qualitative factors in determining whether it is necessary to perform the quantitative goodwill impairment test. If management determines that it is more likely than not that the fair value of a reporting unit is less than the carrying value based on qualitative factors then they will perform the quantitative goodwill impairment test. For the quantitative goodwill impairment testing, the fair value of the reporting units is determined using a combination of a market approach and an income approach which projects the future cash flows produced by the reporting units and discounts those cash flows to their present value. The projection of future cash flows is necessarily dependent upon assumptions on the future levels of income as well as business trends, prospects, market, and economic conditions. The results of the two approaches are weighted to determine the fair value of each reporting unit. When the fair value is less than the carrying value of the net assets of the reporting unit, including goodwill, an impairment loss is charged to operations. To determine the amount of any goodwill impairment, the implied fair value of reporting unit goodwill is compared to the carrying amount of that goodwill. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination is determined. That is, the fair value of a reporting unit is assigned to all of the assets and liabilities of that unit (including any unrecognized intangible assets) as if the reporting unit had been acquired in a business combination. The excess of the fair value of a reporting unit over the amounts assigned to its assets and liabilities is the implied fair value of goodwill. Intangible Assets, Net Intangible assets are initially recognized and measured at fair value. Specifically identified intangible assets with indefinite lives include trademarks and state insurance licenses and authorities. Other specifically identified intangible assets with lives ranging from 7.0 to 27.5 years represent relationships with brokers. These intangible assets are amortized on a straight-line basis over their estimated useful lives. Intangible assets with indefinite useful lives are reviewed for impairment at least annually. In evaluating whether there has been impairment to the intangible asset, management determines the fair value of the intangible asset and compares the resulting fair value to the carrying value of the intangible asset. If the carrying value exceeds the fair value, the intangible asset is written down to fair value, and the impairment is reported through earnings. The Company evaluates intangible assets with definite lives for impairment when impairment indicators are noted. Impairment of Long-Lived Assets Long-lived assets with finite lives are tested for impairment whenever recognized events or changes in circumstances indicate the carrying value of these assets may not be recoverable. If indicators of impairment are present, fair value is calculated using estimated future cash flows expected to be generated from the use of those assets. An impairment loss is recognized only if the carrying amount of a long-lived asset or asset group is not recoverable and exceeds its fair value. The carrying amount of a long-lived asset or asset group is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset or asset group. That assessment is based on the carrying amount of the asset or asset group at the date it is tested for recoverability. An impairment loss is measured as the amount by which the carrying amount of a long-lived asset or asset group exceeds its fair value. Property and Equipment, Net Property and equipment, which is included in “other assets” in the accompanying consolidated balance sheets, is reported at cost less accumulated depreciation and is depreciated principally on a straight-line basis over the estimated useful lives of the depreciable assets, generally three to ten years . Reserve for Losses and Loss Adjustment Expenses The reserve for losses and loss adjustment expenses represents the estimated ultimate cost of all reported and unreported losses and loss adjustment expenses incurred and unpaid at the balance sheet date. The Company does not discount this reserve. The process of estimating the reserve for losses and loss adjustment expenses requires a high degree of judgment and is subject to a number of variables. The reserve for losses and loss adjustment expenses is estimated using individual case-basis valuations and statistical analyses. Those estimates are subject to the effects of trends in loss severity and frequency. The Company utilizes various actuarially-accepted reserving methodologies in determining the continuum of expected outcomes for its reserves. These methodologies utilize various inputs, including management’s initial expected loss ratio (the ratio of losses and loss adjustment expenses incurred to net earned premiums), expected reporting patterns and payment patterns for losses and loss adjustment expenses (based on insurance industry data and the Company’s own experience), and the Company’s actual paid and reported losses and loss adjustment expenses. An internal actuary reviews these results and (after applying appropriate professional judgment and other actuarial techniques that are considered necessary) presents recommendations to the Company’s management. Management uses this information and its judgment to make decisions on the final recorded reserve for losses and loss adjustment expenses. Management believes that the use of judgment is necessary to arrive at a best estimate for the reserve for losses and loss adjustment expenses given the long-tailed nature of the business generally written by the Company and the limited operating experience of the Casualty Reinsurance segment, the fronting and program business in the Specialty Admitted Insurance segment, and the commercial auto business in the Excess and Surplus Lines segment. Catastrophes of significant magnitude, including hurricanes and earthquakes, involve complex coverage issues. In estimating the reserve for losses and loss adjustment expenses for these catastrophes, management uses case reserve estimates based on information obtained from site inspections by the Company’s adjustors and the terms of coverage provided in the policies. Management estimates reserves for incurred but not reported claims for these catastrophes using judgment based on an assessment of the Company’s property insurance exposures where the catastrophes occur and the Company’s progress in settling claims. Although management believes that the reserve for losses and loss adjustment expenses is reasonable, it is possible that the Company’s actual incurred losses and loss adjustment expenses will not develop in a manner consistent with the assumptions inherent in the determination of these reserves. Specifically, the Company’s actual ultimate loss ratio could differ from management’s initial expected loss ratio and/or the Company’s actual reporting patterns for losses could differ from the expected reporting patterns. Accordingly, the ultimate settlement of losses and the related loss adjustment expenses may vary significantly from the estimates included in the Company’s consolidated financial statements. These estimates are reviewed continually by management and are adjusted as necessary as experience develops or new information becomes known; such adjustments are included in current operations. Share Based Compensation The Company expenses the fair value of share equity awards over the vesting period of the award on a straight-line basis. The Black-Scholes-Merton option pricing model is used to value the options granted (see Note 12). Forfeitures of share-based awards are recognized as they occur. As the share based compensation expense is incurred, a corresponding increase to additional paid-in capital in shareholders’ equity is recognized. Share based compensation expense is reflected in “other operating expenses” in the accompanying consolidated statements of income and comprehensive income. Variable Interest Entities Entities that do not have sufficient equity at risk to allow the entity to finance its activities without additional financial support or in which the equity investors, as a group, do not have the characteristic of a controlling financial interest are referred to as variable interest entities (“VIE”). A VIE is consolidated by the variable interest holder that is determined to have the controlling financial interest (primary beneficiary) as a result of having both the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance and the obligation to absorb losses or right to receive benefits from the VIE that could potentially be significant to the VIE. The Company determines whether it is the primary beneficiary of an entity subject to consolidation based on a qualitative assessment of the VIE’s capital structure, contractual terms, nature of the VIE’s operations and purpose, and the Company’s relative exposure to the related risks of the VIE on the date it becomes initially involved in the VIE. The Company reassesses its VIE determination with respect to an entity on an ongoing basis. The Company holds interests in VIEs through certain equity method investments included in “other invested assets” in the accompanying consolidated balance sheets. The Company has determined that it should not consolidate any of the VIEs as it is not the primary beneficiary in any of the relationships. Although the investments resulted in the Company holding variable interests in the entities, they did not empower the Company to direct the activities that most significantly impact the economic performance of the entities. The Company’s investments related to these VIEs totaled $31.2 million and $29.8 million as of December 31, 2019 and 2018 , respectively, representing the Company’s maximum exposure to loss. Earnings Per Share Basic earnings per share excludes dilution and is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted earnings per share reflects the dilution that could occur if securities or other contracts to issue common shares or common share equivalents were exercised or converted into common shares as calculated using the treasury stock method. When inclusion of common share equivalents increases the earnings per share or reduces the loss per share, the effect on earnings is anti-dilutive, and the diluted net earnings or net loss per share is computed excluding these common share equivalents. The following represents a reconciliation of the numerator and denominator of the basic and diluted earnings per share computations contained in the consolidated financial statements. ​ Net Income Weighted-Average Earnings ​ (in thousands, except per share data) Year ended December 31, 2019 ​ ​ ​ Basic $ 38,339 30,275,184 $ 1.27 Common share equivalents — 398,740 (0.02 ) Diluted $ 38,339 30,673,924 $ 1.25 Year ended December 31, 2018 Basic $ 63,830 29,887,990 $ 2.14 Common share equivalents — 419,111 (0.03 ) Diluted $ 63,830 30,307,101 $ 2.11 Year ended December 31, 2017 Basic $ 43,566 29,461,717 $ 1.48 Common share equivalents — 811,432 (0.04 ) Diluted $ 43,566 30,273,149 $ 1.44 Common share equivalents relate to our outstanding equity awards (stock options and RSUs). For the years ended December 31, 2019 , 2018 , and 2017 , common share equivalents of 9,735 shares, 180,329 shares, and 174,380 shares, respectively, are excluded from the calculations of diluted earnings per share as their effects are anti-dilutive. Adopted Accounting Standards Effective January 1, 2019, the Company adopted ASU 2016-02, Leases (Topic 842) . This update requires the recognition of a right-of-use asset and a corresponding lease liability, discounted to the present value, for all leases that extend beyond 12 months. The Company adopted the new standard using a modified retrospective transition method, applying the transition provisions at the beginning of the period of adoption. The Company elected the package of practical expedients permitted under the transition guidance within the new standard and did not elect to use hindsight in determining the lease term. Upon adoption of the new standard, the Company derecognized assets of $22.6 million and liabilities of $30.9 million associated with a lease that was designated as build-to-suit under the previous guidance, and recorded a cumulative-effect adjustment to increase retained earnings by $8.3 million . The Company recorded right-of-use assets of $17.2 million and lease liabilities of $17.8 million at adoption of the new standard associated with operating leases for office space in Bermuda, North Carolina, Virginia, Arizona, and Georgia. The new standard did not materially impact the Company's results of operations, earnings per share, or cash flows, and did not impact compliance under the covenants of the Company's current credit agreements. Prospective Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Current GAAP requires the recognition of credit losses when it is probable a loss has been incurred. The update will require financial assets measured at amortized cost, such as bank loan participations held for investment, to be presented at the net amount expected to be collected by means of an allowance for credit losses that is reflected in net income. Credit losses relating to available-for-sale debt securities will also be recorded through an allowance for credit losses, with the amount of the allowance limited to the amount by which fair value is below amortized cost. This ASU is effective for annual and interim reporting periods beginning after December 15, 2019. The Company will adopt the ASU on January 1, 2020 using the modified-retrospective approach, by which a cumulative-effect adjustment will be made to retained earnings as of the date of adoption. In connection with the adoption of this ASU, the Company will elect the fair value option in accounting for bank loan participations effective January 1, 2020. We will also use the targeted tr

Investments

Investments	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The Company’s available-for-sale fixed maturity securities are summarized as follows: Cost or Gross Gross Fair (in thousands) December 31, 2019 Fixed maturity securities: State and municipal $ 159,894 $ 7,949 $ (742 ) $ 167,101 Residential mortgage-backed 261,524 3,244 (622 ) 264,146 Corporate 611,304 21,306 (389 ) 632,221 Commercial mortgage and asset-backed 249,309 3,954 (806 ) 252,457 U.S. Treasury securities and obligations guaranteed by the U.S. government 114,477 1,229 (39 ) 115,667 Redeemable preferred stock 2,025 9 — 2,034 Total fixed maturity securities, available-for-sale $ 1,398,533 $ 37,691 $ (2,598 ) $ 1,433,626 December 31, 2018 Fixed maturity securities: State and municipal $ 147,160 $ 3,422 $ (1,287 ) $ 149,295 Residential mortgage-backed 208,869 577 (5,337 ) 204,109 Corporate 534,024 1,516 (10,772 ) 524,768 Commercial mortgage and asset-backed 199,528 310 (2,813 ) 197,025 U.S. Treasury securities and obligations guaranteed by the U.S. government 107,803 235 (845 ) 107,193 Redeemable preferred stock 2,025 — (213 ) 1,812 Total fixed maturity securities, available-for-sale $ 1,199,409 $ 6,060 $ (21,267 ) $ 1,184,202 The amortized cost and fair value of available-for-sale investments in fixed maturity securities at December 31, 2019 are summarized, by contractual maturity, as follows: Cost or Fair (in thousands) One year or less $ 81,705 $ 82,048 After one year through five years 456,076 466,952 After five years through ten years 219,717 228,596 After ten years 128,177 137,393 Residential mortgage-backed 261,524 264,146 Commercial mortgage and asset-backed 249,309 252,457 Redeemable preferred stock 2,025 2,034 Total $ 1,398,533 $ 1,433,626 Actual maturities may differ for some securities because borrowers have the right to call or prepay obligations with or without penalties. The following table shows the Company’s gross unrealized losses and fair value for available-for-sale securities aggregated by investment category and the length of time that individual securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total Fair Gross Fair Gross Fair Gross (in thousands) December 31, 2019 Fixed maturity securities: State and municipal $ 30,028 $ (741 ) $ 667 $ (1 ) $ 30,695 $ (742 ) Residential mortgage-backed 23,632 (78 ) 37,363 (544 ) 60,995 (622 ) Corporate 45,550 (365 ) 9,933 (24 ) 55,483 (389 ) Commercial mortgage and asset-backed 46,434 (406 ) 56,720 (400 ) 103,154 (806 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 8,474 (22 ) 7,168 (17 ) 15,642 (39 ) Total fixed maturity securities, available-for-sale $ 154,118 $ (1,612 ) $ 111,851 $ (986 ) $ 265,969 $ (2,598 ) December 31, 2018 Fixed maturity securities: State and municipal $ 19,733 $ (284 ) $ 47,018 $ (1,003 ) $ 66,751 $ (1,287 ) Residential mortgage-backed 49,180 (743 ) 105,778 (4,594 ) 154,958 (5,337 ) Corporate 243,384 (5,089 ) 155,902 (5,683 ) 399,286 (10,772 ) Commercial mortgage and asset-backed 106,423 (1,229 ) 51,805 (1,584 ) 158,228 (2,813 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 17,618 (51 ) 54,201 (794 ) 71,819 (845 ) Redeemable preferred stock 1,812 (213 ) — — 1,812 (213 ) Total fixed maturity securities, available-for-sale $ 438,150 $ (7,609 ) $ 414,704 $ (13,658 ) $ 852,854 $ (21,267 ) The Company held securities of 112 issuers that were in an unrealized loss position at December 31, 2019 with a total fair value of $266.0 million and gross unrealized losses of $2.6 million . None of the fixed maturity securities with unrealized losses has ever missed, or been delinquent on, a scheduled principal or interest payment. At December 31, 2019 , 99.6% of the Company’s fixed maturity security portfolio was rated “BBB-” or better (“investment grade”) by Standard & Poor’s or received an equivalent rating from another nationally recognized rating agency. Management concluded that none of the fixed maturity securities with an unrealized loss at December 31, 2019 , 2018 , and 2017 experienced an other-than-temporary impairment. Management does not intend to sell available-for-sale securities in an unrealized loss position, and it is not “more likely than not” that the Company will be required to sell these securities before a recovery in their value to their amortized cost basis occurs. At December 31, 2017 , management concluded that one equity security, based on the severity and duration of impairment, had experienced an other-than-temporary impairment. Accordingly, the Company recorded an impairment loss of $1.5 million in 2017. Management concluded that none of the other equity securities with an unrealized loss at December 31, 2017 had experienced an other-than-temporary impairment. Bank loan participations generally have a credit rating that is below investment grade (i.e. below “BBB-” for Standard & Poor’s) at the date of purchase. These bank loans are primarily senior, secured floating-rate debt rated “BB”, “B”, or “CCC” by Standard & Poor’s or an equivalent rating from another nationally recognized rating agency. These bank loans include assignments of, and participations in, performing and non-performing senior corporate debt generally acquired through primary bank syndications and in secondary markets. Bank loans consist of, but are not limited to, term loans, the funded and unfunded portions of revolving credit loans, and other similar loans and investments. Management believed that it was probable at the time that these loans were acquired that the Company would be able to collect all contractually required payments receivable. Management concluded that seven loans from six issuers in the Company's bank loan portfolio were impaired at December 31, 2019 . At December 31, 2019 , the impaired loans had a carrying value of $6.9 million , unpaid principal of $14.3 million , and an allowance for credit losses of $7.2 million , $5.1 million of which related to two loans from one issuer who is experiencing liquidity concerns resulting from revenue declines and poor growth prospects in its most profitable segment. Management concluded that none of the loans in the Company's bank loan portfolio were impaired as of December 31, 2018 . At December 31, 2017 , the aggregate allowance for credit losses was $3.2 million on five impaired loans with a total carrying value of $5.1 million and unpaid principal of $8.4 million . At December 31, 2017 , impairments in the bank loan portfolio largely reflect the impact of declining energy prices on the market values of loans to oil and gas companies in the energy sector. At December 31, 2017 , the Company held a participation in a loan with unpaid principal of $807,000 issued by a company that produces and supplies power to Puerto Rico. Management concluded that an allowance for credit losses should be established on the loan at December 31, 2017 to reduce its carrying value to zero . In the first quarter of 2018, the full outstanding principal on the loan was repaid and the Company recognized a realized gain of $807,000 on the repayment. The average recorded investment in impaired bank loans was $3.5 million , $2.6 million , and $5.8 million during the years ended December 31, 2019 , 2018 , and 2017 , respectively, and investment income of $293,000 , $125,000 , and $300,000 was recognized during the time that the loans were impaired. The Company recorded losses of $8.9 million , $858,000 , and $2.4 million during the years ended December 31, 2019 , 2018 , and 2017 , respectively, for changes in the fair value of impaired bank loans. At December 31, 2019 , unamortized discounts on bank loan participations were $2.4 million , and unamortized premiums were $4,000 . At December 31, 2018 , unamortized discounts on bank loan participations were $1.8 million , and unamortized premiums were $17,000 . Major categories of the Company’s net investment income are summarized as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Fixed maturity securities $ 39,875 $ 34,129 $ 26,833 Bank loan participations 19,772 18,279 17,388 Equity securities 5,262 5,240 5,045 Other invested assets 6,254 5,165 14,079 Cash, cash equivalents, restricted cash equivalents, and short-term investments 9,210 2,677 1,704 Gross investment income 80,373 65,490 65,049 Investment expense (4,721 ) (4,234 ) (3,930 ) Net investment income $ 75,652 $ 61,256 $ 61,119   The Company’s net realized and unrealized losses and gains on investments are summarized as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Fixed maturity securities: Gross realized gains $ 1,575 $ 422 $ 840 Gross realized losses (494 ) (976 ) (512 ) ​ 1,081 (554 ) 328 Equity securities: Gross realized gains 11 — 429 Gross realized losses (232 ) (62 ) (1,591 ) Changes in fair values of equity securities 6,257 (5,970 ) — ​ 6,036 (6,032 ) (1,162 ) Bank loan participations: Gross realized gains 846 2,279 2,407 Gross realized losses (10,902 ) (1,166 ) (3,557 ) ​ (10,056 ) 1,113 (1,150 ) Short-term investments and other: Gross realized gains 21 — 1 Gross realized losses (1 ) (6 ) (6 ) ​ 20 (6 ) (5 ) Total $ (2,919 ) $ (5,479 ) $ (1,989 ) The following table summarizes the change in the Company’s available-for-sale gross unrealized gains or losses by investment type: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Change in gross unrealized gains (losses): Fixed maturity securities $ 50,300 $ (22,643 ) $ 6,571 Equity securities — — 5,356 Total $ 50,300 $ (22,643 ) $ 11,927   The Company invests selectively in private debt and equity opportunities. These investments, which together comprise the Company’s other invested assets, are primarily focused in renewable energy, limited partnerships, and bank holding companies. ​ Carrying Value Investment Income ​ December 31, Year Ended December 31, ​ 2019 2018 2019 2018 2017 ​ (in thousands) (in thousands) Renewable energy LLCs (a) $ 31,219 $ 29,795 $ 2,181 $ 2,974 $ 10,578 Renewable energy notes receivable (b) 8,750 8,750 1,313 1,282 526 Limited partnerships (c) 16,741 29,276 2,417 566 2,632 Bank holding companies (d) 4,500 4,500 343 343 343 Total other invested assets $ 61,210 $ 72,321 $ 6,254 $ 5,165 $ 14,079 (a) The Company’s Corporate and Other segment owns equity interests ranging from 2.6% to 32.2% in various LLCs whose principal objective is capital appreciation and income generation from owning and operating renewable energy production facilities (wind and solar). The LLCs are managed by an entity for which one of our directors and one of our recent former directors serve as officers, and the Company’s Executive Chairman and Chief Executive Officer has invested in certain of these LLCs. The equity method is used to account for the Company’s LLC investments. Income for the LLCs primarily reflects adjustments to the carrying values of investments in renewable energy projects to their determined fair values. The fair value adjustments are included in revenues for the LLCs. Expenses for the LLCs are not significant and are comprised of administrative and interest expenses. The Company received cash distributions from these investments totaling $757,000 and $5.8 million for the years ended December 31, 2019 and 2018 , respectively. ​ (b) The Company's Corporate and Other segment has invested in notes receivable for renewable energy projects. At December 31, 2019 and 2018 , the Company held one $8.8 million note issued by an entity for which one of our directors and one of our recent former directors serve as officers . Interest on the note, which matures in 2021, is fixed at 15% . Interest income on the note was $1.3 million , $1.3 million , and $526,000 for the years ended December 31, 2019 , 2018 , and 2017 , respectively. ​ (c) The Company owns investments in limited partnerships that invest in concentrated portfolios including publicly-traded small cap equities, loans of middle market private equity sponsored companies, equity tranches of collateralized loan obligations ("CLOs"), and tranches of distressed home loans. Income from the partnerships is recognized under the equity method of accounting. The Company’s Corporate and Other segment held an investment in a limited partnership with a carrying value of $3.4 million and $3.1 million at December 31, 2019 and 2018 , and recognized investment income of $327,000 , $70,000 , and $394,000 for the years ended December 31, 2019 , 2018 and 2017 , respectively. The Company’s Excess and Surplus Lines segment holds investments in limited partnerships of $13.3 million and $26.2 million at December 31, 2019 and 2018 , respectively. Investment income of $2.1 million , $496,000 , and $2.2 million were recognized on these investments for the years ended December 31, 2019 , 2018 , and 2017 , respectively. At December 31, 2019 , the Company’s Excess and Surplus Lines segment has outstanding commitments to invest another $625,000 in these limited partnerships. (d) The Company's Corporate and Other segment holds $4.5 million of subordinated notes issued by a bank holding company for which the Company’s Executive Chairman and Chief Executive Officer was previously the Lead Independent Director and an investor and for which one of the Company’s directors was an investor and is currently a lender (the "Bank Holding Company"). Interest on the notes, which mature in 2023, is fixed at 7.6% per annum. Interest income on the notes was $343,000 in each of the years ended December 31, 2019 , 2018 and 2017 . The Company previously held common shares issued by the Bank Holding Company. Realized gains of $409,000 were recognized on the sale of the common shares for the year ended December 31, 2017 . At December 31, 2019 and 2018 , the Company held an investment in a collateralized loan obligation (CLO) where one of the underlying loans was issued by the Bank Holding Company. The investment, with a carrying value of $3.2 million and $4.2 million at December 31, 2019 and 2018 , is classified as an available-for-sale fixed maturity. The Company maintains fixed maturity securities, short-term investments, accrued investment income, and cash and cash equivalents amounting to $464.5 million at December 31, 2019 in trust accounts or on deposit as collateral for outstanding letters of credit issued as security to third-party reinsureds on reinsurance assumed by JRG Re. At December 31, 2019 and 2018 , cash and investments with a fair value of $36.6 million and $25.5 million , respectively, were on deposit with state insurance departments to satisfy regulatory requirements. At December 31, 2019 , the Company held no investments in securitizations of alternative-A mortgages or sub-prime mortgages.

Deferred Policy Acquisition Cos

Deferred Policy Acquisition Costs	12 Months Ended
	Dec. 31, 2019
Deferred Policy Acquisition Costs Disclosures [Abstract]
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs ​ An analysis of deferred policy acquisition costs is as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Balance at beginning of period $ 54,450 $ 72,365 $ 64,789 Policy acquisition costs deferred: Commissions 67,303 72,473 107,387 Underwriting and other issue expenses 24,146 20,715 16,190 ​ 91,449 93,188 123,577 Amortization of policy acquisition costs (83,893 ) (111,103 ) (116,001 ) Net change 7,556 (17,915 ) 7,576 Balance at end of period $ 62,006 $ 54,450 $ 72,365

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets ​ On December 11, 2007, the Company completed an acquisition of James River Group by acquiring 100% of the outstanding shares of James River Group common stock, referred to herein as the “Merger”. The transaction was accounted for under the purchase method of accounting, and goodwill and intangible assets were recognized by the Company as a result of the transaction. All of the Company’s goodwill is an asset of the Excess and Surplus Lines segment. The Company’s annual testing performed in the fourth quarter of 2019 , 2018 and 2017 indicated that no impairment of goodwill had occurred. The carrying amount of goodwill at December 31, 2019 and 2018 was $181.8 million . Accumulated goodwill impairment losses were $99.6 million at December 31, 2019 and 2018 . The most recent goodwill impairment losses occurred in 2010. Specifically identifiable intangible assets were acquired in the Merger. During the fourth quarters of 2019 , 2018 and 2017 , the indefinite-lived intangible assets for trademarks and insurance licenses and authorities were tested for impairment. Intangible assets for broker relationships that have specific lives and are subject to amortization were also reviewed for impairment. In the Specialty Admitted Insurance segment, Falls Lake General Insurance Company was merged into Falls Lake National in the fourth quarter of 2018. In connection with this merger, Falls Lake General Insurance Company surrendered its licenses to the various state insurance departments and reduced the carrying value of its intangible asset for "State Licenses" to $0 . This caused a $200,000 impairment in 2018 in the Specialty Admitted Insurance segment. There were no impairments recognized in 2019 or 2017 . The gross carrying amounts and accumulated amortization for each major specifically identifiable intangible asset class were as follows: ​ December 31, ​ 2019 2018 Weighted- Average Life (Years) Gross Accumulated Gross Accumulated ​ ​ (in thousands) Trademarks Indefinite $ 22,200 $ — $ 22,200 $ — Insurance licenses and authorities Indefinite 8,964 — 8,964 — Identifiable intangibles not subject to amortization ​ 31,164 — 31,164 — Broker relationships 24.6 11,611 5,835 11,611 5,238 Identifiable intangible assets subject to amortization ​ 11,611 5,835 11,611 5,238 ​ ​ $ 42,775 $ 5,835 $ 42,775 $ 5,238 Future estimated amortization of specifically identifiable intangible assets as of December 31, 2019 is as follows ( in thousands) : 2020 $ 538 2021 363 2022 363 2023 363 2024 363 Thereafter 3,786 Total $ 5,776 The table below summarizes the changes in the net carrying values of intangible assets by segment for 2019 : December 31, 2018 December 31, 2019 ​ Net Carrying Amortization Impairment Net Carrying ​ (in thousands) Excess and Surplus Lines Trademarks $ 19,700 $ — $ — $ 19,700 Insurance licenses and authorities 4,900 — — 4,900 Broker relationships 5,965 (362 ) — 5,603 ​ 30,565 (362 ) — 30,203 Specialty Admitted Insurance Trademarks 2,500 — — 2,500 Insurance licenses and authorities 4,065 — — 4,065 Broker relationships 407 (235 ) — 172 ​ 6,972 (235 ) — 6,737 Total identifiable intangible assets $ 37,537 $ (597 ) $ — $ 36,940   ​ The table below summarizes the changes in the net carrying values of intangible assets by segment for 2018 : December 31, 2017 December 31, 2018 ​ Net Carrying Amortization Impairment Net Carrying ​ (in thousands) Excess and Surplus Lines Trademarks $ 19,700 $ — $ — $ 19,700 Insurance licenses and authorities 4,900 — — 4,900 Broker relationships 6,327 (362 ) — 5,965 ​ 30,927 (362 ) — 30,565 Specialty Admitted Insurance Trademarks 2,500 — — 2,500 Insurance licenses and authorities 4,265 — (200 ) 4,065 Broker relationships 642 (235 ) — 407 ​ 7,407 (235 ) (200 ) 6,972 Total identifiable intangible assets $ 38,334 $ (597 ) $ (200 ) $ 37,537 Amortization of intangible assets was $362,000 for the Excess and Surplus Lines segment and $235,000 for the Specialty Admitted Insurance segment for the year ended December 31, 2017 .

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net ​ Property and equipment, net of accumulated depreciation, is included in "other assets" on the consolidated balance sheets and consists of the following: ​ December 31, ​ 2019 2018 ​ (in thousands) Building, leased for which the Company was previously deemed the owner for accounting purposes $ — $ 30,971 Electronic data processing hardware and software 7,522 7,423 Furniture and equipment 2,180 2,662 Property and equipment, cost basis 9,702 41,056 Accumulated depreciation (7,934 ) (17,745 ) Property and equipment, net $ 1,768 $ 23,311

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	Leases The Company has entered into operating leases for office space in Bermuda, North Carolina, Virginia, Arizona, and Georgia. Following the adoption of ASU 2016-02, Leases (Topic 842) , effective January 1, 2019, the present value of future lease payments for the Company’s leases with terms greater than 12 months are included on the consolidated balance sheet as lease liabilities and right-of-use lease assets. Total expected lease payments are based on the lease payments specified in the contract and the stated term, including any options to extend or terminate that the Company is reasonably certain to exercise. The Company has elected the practical expedient to account for lease components and any associated non-lease components as a single lease component, and therefore allocates all of the expected lease payments to the lease component. The lease liability, which represents the Company’s obligation to make lease payments arising from the lease, is calculated based on the present value of expected lease payments over the remaining lease term, discounted using the Company’s collateralized incremental borrowing rate at the commencement date. The lease liability is then adjusted for any prepaid rent, lease incentives received or capitalized initial direct costs to determine the lease asset, which represents the Company's right to use the underlying asset for the lease term. Lease liabilities and right-of-use assets are included in other liabilities and other assets, respectively, on the Company's consolidated balance sheet. At December 31, 2019 , lease liabilities and right-of-use assets associated with the Company's operating leases were $18.2 million and $17.2 million , respectively. The weighted-average discount rate and weighted average remaining lease term for operating leases was 4.3% and 5.3 years , respectively, as of December 31, 2019 . The table below summarizes maturities of the Company’s operating lease liabilities as of December 31, 2019 , which reconciles to total lease liabilities included in other liabilities on the Company’s consolidated balance sheet: Years ending December 31, (in thousands) 2020 $ 4,024 2021 3,993 2022 3,800 2023 3,619 2024 2,422 Thereafter 2,546 Total lease payments 20,404 Less imputed interest (2,172 ) Total operating lease liabilities $ 18,232 Operating lease liabilities include $11.9 million associated with office space in a building that is owned by a partnership in which the Company has a minority interest. Operating lease costs were $5.2 million , $4.6 million , and $4.2 million for the years ended December 31, 2019 , 2018 , and 2017 , respectively. Operating lease costs are primarily comprised of rental expense for operating leases. Rental expense is recognized on a straight line basis over the lease term and includes amortization of the right-of-use lease asset and imputed interest on the lease liability. Operating lease costs are included in other operating expenses in the Company's consolidated statements of income and comprehensive income.

Reserve for Losses and Loss Adj

Reserve for Losses and Loss Adjustment Expenses	12 Months Ended
	Dec. 31, 2019
Liability for Claims and Claims Adjustment Expense [Abstract]
Reserve for Losses and Loss Adjustment Expenses	Reserve for Losses and Loss Adjustment Expenses ​ In establishing the reserve for losses and loss adjustment expenses, the Company’s internal actuaries estimate an initial expected ultimate loss ratio for each of our lines of business by accident year (or for our Casualty Reinsurance segment, on a contract by contract basis). Input from the Company’s underwriting and claims departments, including premium pricing assumptions and historical experience, are considered by the Company’s internal actuaries in estimating the initial expected loss ratios. The Company’s internal actuaries generally utilize five actuarial methods in their estimation process for the reserve for losses and loss adjustment expenses. These five methods utilize, to varying degrees, the initial expected loss ratio, detailed statistical analysis of past claims reporting and payment patterns, claims frequency and severity, paid loss experience, industry loss experience, and changes in market conditions, policy forms, exclusions, and exposures. In applying these methods to develop an estimate of the reserve for losses and loss adjustment expenses, our internal actuaries use judgment to determine three key parameters for each accident year and line of business: the initial expected loss ratios, the incurred and paid loss development factors and the weighting of the five actuarial methods to be used for each accident year and line of business. For the Excess and Surplus Lines and Specialty Admitted Insurance segments, the internal actuaries perform a study on each of these parameters annually and make recommendations for the initial expected loss ratios, the incurred and paid loss development factors and the weighting of the five actuarial methods by accident year and line of business. Members of management’s Reserve Committee review and approve the parameter review actuarial recommendations, and these approved parameters are used in the reserve estimation process for the next four quarters at which time a new parameter study is performed. For the Casualty Reinsurance segment, periodic assessments are made on a contract by contract basis with the goal of keeping the initial expected loss ratios and the incurred and paid loss development factors as constant as possible until sufficient evidence presents itself to support adjustments. Method weights are generally less rigid for the Casualty Reinsurance segment given the heterogeneous nature of the various contracts, and the potential for significant changes in mix of business within individual treaties. Different reserving methods are appropriate in different situations, and the Company’s internal actuaries use their judgment and experience to determine the weighting of the methods to use for each accident year and each line of business and, for our Casualty Reinsurance segment, on a contract by contract basis. For example, the current accident year has very little incurred and paid loss development data on which to base reserve projections. As a result, the Company relies heavily on the initial expected loss ratio in estimating reserves for the current accident year. The Company generally sets the initial expected loss ratio for the current accident year consistent with the internal actuaries’ pricing assumptions. We believe that this is a reasonable and appropriate reserving assumption for the current accident year since our pricing assumptions are actuarially driven and since the Company expects to make an acceptable return on the new business written. If actual loss emergence is better than our initial expected loss ratio assumptions, we will experience favorable development and if it is worse than our initial expected loss ratio assumptions, we will experience adverse development. Conversely, sufficient incurred and paid loss development data is available for the oldest accident years, so more weight is given to this development data and less weight is given to the initial expected loss ratio. The following table provides a reconciliation of the beginning and ending reserve balances for losses and loss adjustment expenses, net of reinsurance, to the gross amounts reported in the consolidated balance sheets: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Reserve for losses and loss adjustment expenses net of reinsurance recoverables at beginning of period $ 1,194,088 $ 989,825 $ 761,128 Add: Incurred losses and loss adjustment expenses net of reinsurance: ​ ​ ​ Current year 603,094 582,604 533,905 Prior years 69,008 17,672 21,472 Total incurred losses and loss and adjustment expenses 672,102 600,276 555,377 Deduct: Loss and loss adjustment expense payments net of reinsurance: ​ ​ ​ Current year 75,249 86,355 103,205 Prior years 413,480 309,658 223,475 Total loss and loss adjustment expense payments 488,729 396,013 326,680 Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period 1,377,461 1,194,088 989,825 Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period 668,045 467,371 302,524 Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period $ 2,045,506 $ 1,661,459 $ 1,292,349 The foregoing reconciliation shows that $69.0 million of adverse development was experienced in 2019 on the reserve for losses and loss adjustment expenses held at December 31, 2018. This adverse reserve development included $51.2 million of adverse development in the Excess and Surplus Lines segment including $57.4 million of adverse development in the commercial auto line of business that was primarily related to the 2016 and 2017 accident years with Rasier LLC and its affiliates (collectively, “Rasier”) . Rasier's business was new, complex, and rapidly changing, and the Company's underwriting assumptions and the related pricing of this risk did not keep pace with the insured's escalating loss trends. As a result of changes in the risk, including most recently the enactment of California Assembly Bill 5 (AB5) and its anticipated impact on the Rasier business, unsatisfactory underwriting profits from the Rasier business, and a desire to refocus on the Company’s growing E&S core (non-commercial auto) lines of business where the Company has experienced many years of profitable underwriting results, on October 8, 2019, the Company delivered a notice of early cancellation to Rasier, effective December 31, 2019. The adverse development for commercial auto was partially offset by $6.2 million of favorable development in other Excess and Surplus Lines underwriting divisions. The Company also experienced $5.3 million of favorable development on prior accident years in the Specialty Admitted Insurance segment, as losses on our workers’ compensation business written prior to 2018 continued to develop more favorably than we had anticipated. The Casualty Reinsurance segment experienced $23.1 million of adverse development on prior accident years primarily in accident years 2011 through 2016. This adverse development was mainly in the general liability and commercial auto lines of business. The foregoing reconciliation shows that $17.7 million of adverse development was experienced in 2018 on the reserve for losses and loss adjustment expenses held at December 31, 2017. This adverse reserve development included $15.0 million of adverse development in the Excess and Surplus Lines segment, including $20.7 million of adverse development in the commercial auto line of business that was primarily related to the 2016 contract year with Rasier. The adverse development for commercial auto was partially offset by $5.7 million of favorable development in other Excess and Surplus Lines underwriting divisions primarily from favorable development in the Excess Property underwriting division related to the 2017 hurricanes. Favorable reserve development in the Specialty Admitted Insurance segment was $5.6 million and primarily came from accident years 2014 through 2016, as loss emergence on our workers’ compensation business written prior to 2016 continued to develop more favorably than we had anticipated. In addition, $8.2 million of adverse development occurred in the Casualty Reinsurance segment, with a majority of this adverse development coming from accident years at least four years old and treaties the Company has since non-renewed. The foregoing reconciliation shows that $21.5 million of adverse development was experienced in 2017 on the reserve for losses and loss adjustment expenses held at December 31, 2016. This adverse reserve development included $20.0 million of adverse development in the Excess and Surplus Lines segment, including $38.7 million of adverse development in the commercial auto line of business that was primarily related to the 2016 contract year with Rasier. The adverse development for commercial auto was partially offset by favorable development of $18.6 million in other Excess and Surplus Lines underwriting divisions primarily from the 2014 through 2016 accident years. This favorable development occurred because our actuarial studies at December 31, 2017 for the Excess and Surplus Lines segment indicated that our loss experience on our casualty business excluding commercial auto continued to be below our initial expected ultimate loss ratios. The Company also experienced $2.7 million of favorable development on prior accident years in the Specialty Admitted Insurance segment primarily from accident years 2010 through 2015, as losses on our workers’ compensation business written prior to 2016 continued to develop more favorably than we had anticipated. The Casualty Reinsurance segment experienced $4.2 million of adverse development on prior accident years primarily from two contracts from 2010 through 2013 that had higher than expected reported losses in 2017. The following tables present incurred and paid losses and loss adjustment expenses, net of reinsurance as of December 31, 2019 for: (1) the Excess and Surplus Lines segment split between all excess and surplus lines business excluding commercial auto and commercial auto, (2) the Specialty Admitted Insurance segment split between individual risk workers’ compensation and fronting and programs, and (3) the Casualty Reinsurance segment. The information provided herein about incurred and paid accident year claims development for the years ended December 31, 2018 and prior is presented as unaudited supplementary information. Excess and Surplus Lines — Excluding Commercial Auto Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 78,424 $ 80,569 $ 78,117 $ 73,035 $ 69,080 $ 69,964 $ 70,294 $ 70,913 $ 71,312 $ 69,594 2011 111,190 119,927 114,473 106,564 106,381 106,130 106,643 106,536 105,173 2012 97,908 98,672 97,829 96,497 97,306 99,619 101,271 103,061 2013 96,729 96,064 85,433 81,009 82,830 83,855 82,732 2014 114,942 104,092 90,267 82,232 84,074 88,904 2015 126,443 113,417 104,847 102,434 103,688 2016 138,507 125,093 126,050 126,971 2017 144,349 131,897 132,136 2018 167,004 158,458 2019 214,653 Total $ 1,185,370   Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 13,673 $ 26,418 $ 35,812 $ 45,641 $ 52,071 $ 57,371 $ 61,307 $ 64,214 $ 65,246 $ 65,915 2011 27,684 53,109 72,732 81,696 90,884 94,998 98,684 99,798 101,728 2012 6,944 33,757 49,604 63,216 74,869 82,545 88,812 94,588 2013 3,867 14,509 30,382 44,421 59,641 66,553 71,035 2014 3,412 16,969 28,212 43,891 58,774 71,549 2015 4,048 17,164 34,801 55,911 73,455 2016 5,180 22,852 46,045 70,105 2017 5,290 22,956 42,764 2018 6,000 26,160 2019 8,235 Total $ 625,534 All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance (60 claims outstanding) $ 8,978 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 568,814 Excess and Surplus Lines — Commercial Auto Incurred losses and adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 1,255 $ 1,300 $ 1,451 $ 1,351 $ 1,301 $ 1,277 $ 1,277 2014 20,487 14,071 17,233 18,953 19,779 18,303 2015 30,109 33,113 35,149 36,139 36,636 2016 74,340 109,286 126,791 147,122 2017 207,355 208,743 272,421 2018 255,881 230,220 2019 262,306 Total $ 968,285 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 60 $ 1,182 $ 1,285 $ 1,291 $ 1,275 $ 1,275 $ 1,275 2014 6,166 8,645 12,679 16,359 18,678 17,745 2015 8,356 15,234 24,282 31,592 34,819 2016 18,295 54,054 89,381 125,108 2017 41,467 107,377 192,961 2018 45,136 119,099 2019 44,225 Total $ 535,232 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 433,053 Specialty Admitted — Individual Risk Workers’ Compensation Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 27,209 $ 28,736 $ 30,464 $ 30,373 $ 28,963 $ 28,938 $ 27,590 $ 27,098 $ 27,099 $ 27,099 2011 37,834 41,421 40,154 38,999 38,311 37,455 36,594 36,593 36,593 2012 32,116 32,420 31,490 29,689 28,255 28,174 28,186 28,186 2013 12,525 13,668 12,786 11,578 10,907 10,909 10,909 2014 16,638 16,652 14,620 13,890 12,704 12,704 2015 20,938 21,274 19,741 18,376 17,626 2016 21,678 20,299 18,050 15,800 2017 24,869 22,071 19,779 2018 16,432 16,288 2019 20,253 Total $ 205,237 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 7,157 $ 16,245 $ 21,805 $ 23,898 $ 25,210 $ 25,477 $ 26,345 $ 26,352 $ 26,358 $ 26,365 2011 10,123 23,127 29,021 33,204 34,240 34,287 34,334 34,614 34,638 2012 9,222 20,308 24,755 26,435 26,897 26,932 26,963 26,994 2013 4,487 8,723 9,846 10,246 10,263 10,309 10,337 2014 4,633 10,648 12,041 12,236 12,282 12,282 2015 6,604 13,285 15,118 15,889 15,901 2016 4,664 10,227 12,135 12,432 2017 6,546 12,782 14,285 2018 4,497 9,034 2019 5,473 Total $ 167,741 All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance (4 claims outstanding) $ 1,039 Outstanding losses and loss adjustment expenses assumed from involuntary workers’ compensation pools $ 4,656 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 43,191 Specialty Admitted — Fronting and Programs Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 104 $ 80 $ 52 $ 52 $ 52 $ 52 52 2014 3,460 3,468 3,818 3,425 3,228 3,083 2015 7,136 9,632 9,358 8,974 8,384 2016 11,542 15,670 14,682 15,522 2017 21,229 24,271 25,201 2018 21,758 20,677 2019 18,832 Total $ 91,751 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 28 $ 52 $ 52 $ 52 $ 52 $ 52 52 2014 883 1,687 2,369 2,728 2,854 2,916 2015 2,058 4,666 6,165 6,919 7,329 2016 1,894 5,123 6,888 10,732 2017 1,223 6,682 13,065 2018 885 4,972 2019 4,358 Total $ 43,424 All outstanding losses and loss adjustment expenses, net of reinsurance $ 48,327 Outstanding losses and loss adjustment expenses, assumed from involuntary pools $ 400 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 48,727 Casualty Reinsurance Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 64,413 $ 60,476 $ 61,068 $ 62,714 $ 61,344 $ 60,949 $ 60,978 $ 61,619 $ 62,605 $ 63,357 2011 114,908 103,123 97,366 97,812 98,993 99,282 101,276 103,196 105,333 2012 148,251 132,388 131,281 135,594 136,813 139,978 143,305 146,045 2013 133,230 130,361 131,352 134,446 137,801 143,124 146,760 2014 118,881 115,927 114,636 116,981 121,200 126,160 2015 119,157 108,870 108,699 109,117 114,517 2016 112,759 105,533 103,544 108,222 2017 134,628 128,472 129,800 2018 121,529 119,098 2019 86,022 Total $ 1,145,314 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 21,918 $ 31,500 $ 38,430 $ 44,921 $ 49,263 $ 52,761 $ 54,659 $ 57,013 $ 58,707 $ 59,634 2011 48,688 61,922 68,616 78,164 87,267 90,287 94,627 97,715 99,511 2012 73,124 81,859 97,215 113,943 121,026 128,567 133,606 137,430 2013 59,756 75,094 93,902 108,396 119,256 127,732 134,644 2014 41,421 58,601 76,302 89,899 101,366 110,374 2015 40,021 53,986 68,002 80,208 90,661 2016 36,268 50,905 65,409 78,145 2017 47,739 72,891 90,117 2018 30,903 50,274 2019 12,646 Total $ 863,436 All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance $ 1,798 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 283,676 The reconciliation of the net incurred and paid claims development tables to the reserve for losses and loss adjustment expenses in the consolidated balance sheet at December 31, 2019 is as follows (in thousands): E&S – excluding commercial auto $ 568,814 E&S – commercial auto 433,053 Specialty Admitted – individual risk workers’ compensation 43,191 Specialty Admitted – fronting and programs 48,727 Casualty Reinsurance 283,676 Net reserve for losses and loss adjustment expenses 1,377,461 Reinsurance recoverables on unpaid losses 668,045 Gross reserve for losses and loss adjustment expenses $ 2,045,506 The following is unaudited supplementary information about average annual percentage payouts of incurred claims by age, net of reinsurance, for the Excess and Surplus Lines segment and the Specialty Admitted Insurance segments as of December 31, 2019 . ​ Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 E&S – excluding commercial auto 9.5 % 15.7 % 17.2 % 18.5 % 14.5 % 8.0 % 5.4 % 3.8 % 2.0 % 1.1 % E&S – commercial auto 20.4 % 38.1 % 16.0 % 14.1 % 7.2 % 2.6 % 1.5 % Specialty Admitted – individual risk workers’ compensation 27.9 % 30.9 % 16.0 % 10.2 % 7.2 % 1.2 % 1.7 % 0.9 % 0.1 % 1.3 % Specialty Admitted – fronting and programs 18.7 % 22.4 % 24.3 % 16.1 % 10.5 % 5.3 % Casualty Reinsurance 21.1 % 16.4 % 12.2 % 8.9 % 6.4 % 5.3 % 4.3 % 3.6 % 3.5 % 3.2 % In determining the cumulative number of reported claims, the Company measures claim counts by individual claimant for individual risk workers’ compensation policies in the Specialty Admitted Insurance segment. In the Excess and Surplus Lines insurance segment and for fronting and programs in the Specialty Admitted Insurance segment, the Company measures claim counts by claim event. The claim counts include all claims reported, even if the Company does not establish a liability for the claim (i.e. reserve for loss and loss adjustment expenses). The Casualty Reinsurance segment typically assumes written premium under quota share arrangements. The Company typically does not have direct access to claim frequency information underlying its assumed quota arrangements given the nature of that business. In addition, multiple claims are often aggregated by the ceding company before being reported to the Company. We do not use claim frequency information in the Casualty Reinsurance segment in the determination of loss reserves or for other internal purposes. Based on these considerations, the Company does not believe providing claims frequency information is practicable as it relates to the Casualty Reinsurance segment. The table below provides information on IBNR liabilities and claims frequency for: (1) the Excess and Surplus Lines segment split between commercial auto and all non commercial auto, and (2) the Specialty Admitted Insurance segment split between individual risk workers’ compensation and fronting and programs: Excess and Surplus Lines — Excluding Commercial Auto Accident Year Incurred Losses IBNR Cumulative # of ​ ($ in thousands) 2010 $ 69,594 $ 1,347 1,429 2011 105,173 2,380 1,480 2012 103,061 2,042 1,806 2013 82,732 5,493 2,396 2014 88,904 9,855 2,162 2015 103,688 7,681 2,531 2016 126,971 23,882 2,933 2017 132,136 53,525 2,898 2018 158,458 95,477 3,935 2019 214,653 178,172 4,038 Excess and Surplus Lines — Commercial Auto Accident Year Incurred Losses and Loss Adj Expenses IBNR Cumulative # of Reported Claims ​ ($ in thousands) 2013 $ 1,277 $ 1 54 2014 18,303 150 7,763 2015 36,636 337 41,757 2016 147,122 5,258 89,003 2017 272,421 11,473 133,654 2018 230,220 34,896 95,889 2019 262,306 167,476 67,380 Specialty Admitted - Individual Risk Workers’ Compensation Accident Year Incurred Losses IBNR Cumulative # of ​ ($ in thousands) 2010 $ 27,099 $ 698 $ 1,604 2011 36,593 1,879 1,814 2012 28,186 1,090 1,323 2013 10,909 572 540 2014 12,704 423 850 2015 17,626 1,440 975 2016 15,800 3,245 836 2017 19,779 3,888 1,092 2018 16,288 3,495 1,230 2019 20,253 2,965 1,482   Specialty Admitted — Fronting and Programs Accident Year Incurred Losses IBNR Cumulative # of ​ ($ in thousands) 2013 $ 52 $ — 22 2014 3,083 147 857 2015 8,384 432 1,362 2016 15,522 1,861 2,807 2017 25,201 6,751 6,706 2018 20,677 10,142 7,158 2019 18,832 10,961 5,695 The table below provides information on IBNR liabilities for the Casualty Reinsurance segment: Accident Year Incurred Losses IBNR ​ ($ in thousands) 2010 $ 63,357 $ 723 2011 105,333 1,184 2012 146,045 2,025 2013 146,760 2,631 2014 126,160 3,487 2015 114,517 9,957 2016 108,222 18,720 2017 129,800 36,167 2018 119,098 29,472 2019 86,022 68,499 The Company has not provided insurance coverage that could reasonably be expected to produce material levels of asbestos claims activity. In addition, management does not believe that the Company is exposed to environmental liability claims other than those which it has specifically underwritten and priced as an environmental exposure.

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance The Company remains liable to policyholders if its reinsurers are unable to meet their contractual obligations under applicable reinsurance agreements. To minimize exposure to significant losses from reinsurance insolvencies, the Company evaluates the financial condition of its reinsurers and monitors concentrations of credit risk. The Company’s reinsurance contracts generally require reinsurers that are not authorized as reinsurers under U.S. state insurance regulations or that experience rating downgrades from rating agencies below specified levels to fund their share of the Company’s ceded outstanding losses and loss adjustment expense reserves, typically through the use of irrevocable and unconditional letters of credit. In fronting arrangements, which the Company conducts through its Specialty Admitted Insurance segment, the Company is subject to credit risk with regard to insurance companies who act as reinsurers for the Company in such arrangements. The Company customarily requires a collateral trust arrangement to secure the obligations of the insurance entity for whom it is fronting. At December 31, 2019 , the Company had reinsurance recoverables on unpaid losses of $668.0 million and reinsurance recoverables on paid losses of $33.2 million . All material reinsurance recoverables are from companies with A.M. Best Company ratings of “A-” (Excellent) or better, or are collateralized with letters of credit or by a trust agreement. At December 31, 2019 , reinsurance recoverables on unpaid losses from the Company’s three largest reinsurers were $191.4 million , $59.6 million , and $58.0 million , representing 46.3% of the total balance. At December 31, 2019 , prepaid reinsurance premiums ceded to three reinsurers totaled $27.2 million , $24.5 million , and $22.3 million , representing 41.3% of the total balance. Premiums written, premiums earned, and losses and loss adjustment expenses incurred are summarized as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Written premiums: ​ ​ ​ Direct $ 1,305,948 $ 1,027,222 $ 843,719 Assumed 164,787 139,551 238,186 Ceded (574,585 ) (404,101 ) (315,279 ) Net $ 896,150 $ 762,672 $ 766,626 Earned premiums: ​ ​ ​ Direct $ 1,182,501 $ 990,221 $ 842,182 Assumed 150,330 208,192 173,472 Ceded (509,085 ) (383,015 ) (274,545 ) Net $ 823,746 $ 815,398 $ 741,109 Losses and loss adjustment expenses: ​ ​ ​ Direct $ 953,548 $ 769,490 $ 626,318 Assumed 113,843 131,346 142,818 Ceded (395,289 ) (300,560 ) (213,759 ) Net $ 672,102 $ 600,276 $ 555,377

Senior Debt

Senior Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Senior Debt	Senior Debt ​ The Company has a $315.0 million senior revolving credit facility (as amended or amended and restated, the "2013 Facility”). The 2013 Facility is comprised of the following at December 31, 2019 : • A $102.5 million secured revolving facility utilized by JRG Re to issue letters of credit for the benefit of third-party reinsureds. This portion of our credit facility is secured by our investment securities. At December 31, 2019 , the Company had $77.6 million of letters of credit issued under the secured facility. ​ • A $212.5 million unsecured revolving facility to meet the working capital needs of the Company. All unpaid principal on the revolver is due at maturity. Interest accrues quarterly and is payable in arrears at LIBOR plus a margin which at December 31, 2019 was 1.375% , which is subject to change according to terms in the credit agreement. At December 31, 2019 and 2018 , the Company had a drawn balance of $133.3 million and $73.3 million , respectively, outstanding on the unsecured revolver. ​ James River Group Holdings, Ltd. and JRG Re are borrowers on the 2013 Facility. The 2013 Facility has been amended from time to time since its inception in 2013. On November 8, 2019, the Company entered into a Second Amended and Restated Credit Agreement for the 2013 Facility which, among other things, extended the maturity date of the 2013 Facility until November 8, 2024 , increased the amount available under the unsecured revolving credit facility to $212.5 million , lowered the applicable interest rate and letter of credit fees, and modified certain negative covenants to be less restrictive. A subsidiary of the Bank Holding Company is one of the lenders for the 2013 Facility, with a $36.0 million commitment allocation on the total $315.0 million 2013 Facility. The 2013 Facility contains certain financial and other covenants (including minimum net worth, maximum ratio of total adjusted debt outstanding to total capitalization, and financial strength ratings) with which the Company was in compliance, at December 31, 2019 . On August 2, 2017, the Company and its wholly-owned subsidiary, JRG Re, together as borrowers, entered into a credit agreement (the "2017 Facility") that provides the Company with a revolving line of credit of up to $100.0 million , which may be used for loans and letters of credit made or issued, at the borrowers' option, on a secured or ​unsecured basis. The loans and letters of credit made or issued under the revolving line of credit may be used to finance the Borrowers’ general corporate purposes. On November 8, 2019, the Company entered into a First Amendment to Credit Agreement which, among other things, lowered the applicable interest rate and modified certain negative covenants to be less restrictive. Obligations under the 2017 Facility carry a variable rate of interest subject to terms in the credit agreement and will mature 30 days after notice of termination from the lender. Interest accrues quarterly and is payable in arrears at variable rates which are subject to change according to terms in the credit agreement. At December 31, 2019 , unsecured loans of $10.0 million and secured letters of credit totaling $21.9 million were outstanding under the facility. In order to secure borrowings and letters of credit made or issued under the secured portion of the revolving line of credit, JRG Re entered into a pledge and security agreement on August 2, 2017 with the lender, pursuant to which JRG Re will pledge certain investment securities. In the event the Company elects to pledge investment securities as collateral for the secured portion of the revolving credit facility, the Company will enter into a similar pledge and security agreement. The lender under the credit agreement and its affiliate is a joint bookrunner and joint lead arranger under the Company’s Second Amended and Restated Credit Agreement dated as of November 8, 2019, as amended, and its affiliate was also an underwriter in the December 2014 initial public offering of the Company’s common shares. The 2017 Facility contains certain financial and other covenants which we are in compliance with at December 31, 2019 . On May 26, 2004, James River Group issued $15.0 million of unsecured, floating rate senior debentures (the “Senior Debt”), due April 29, 2034 unless accelerated earlier, through an indenture. The Senior Debt is not redeemable by the holder and is not subject to sinking fund requirements. Interest accrues quarterly and is payable in arrears at a per annum rate of the three-month LIBOR on the Determination Date (as defined in the indenture) plus 3.85% . The Senior Debt is redeemable prior to its stated maturity in whole or in part, at the option of James River Group. The terms of the indenture generally provide that so long as the Senior Debt is outstanding, neither James River Group nor any of its subsidiaries may: • assume or permit to exist any indebtedness that is secured by any encumbrance on the capital stock of James River Group or any of its subsidiaries which is senior to the Senior Debt; or ​ • issue, sell, transfer or otherwise dispose of any shares of, securities convertible into, or warrants, rights or options to subscribe for or purchase shares of, capital stock of any subsidiary.​ The terms of the Senior Debt contain certain covenants, with which we are in compliance at December 31, 2019 , and which, among other things, restrict our ability to assume senior indebtedness secured by our U.S. holding company's common stock or its subsidiaries' capital stock or to issue shares of its subsidiaries' capital stock. Interest payable is included in “accrued expenses” in the accompanying consolidated balance sheets.

Junior Subordinated Debt

Junior Subordinated Debt	12 Months Ended
	Dec. 31, 2019
Subordinated Borrowings [Abstract]
Junior Subordinated Debt	Junior Subordinated Debt ​ The Company issued trust preferred securities (“Trust Preferred Securities”) through James River Capital Trust I, James River Capital Trust II, James River Capital Trust III, James River Capital Trust IV, and Franklin Holdings II (Bermuda) Capital Trust I, (each, a “Trust”; collectively, the “Trusts”). These Delaware statutory trusts are sponsored and wholly-owned by the Company. Each Trust was created solely for the purpose of issuing the Trust Preferred Securities. Each Trust used proceeds from the sale of its Trust Preferred Securities to purchase the Company’s floating rate junior subordinated debentures (the “Junior Subordinated Debt”) issued to the Trust under an indenture (each, an “Indenture”; collectively, the “Indentures”). The Junior Subordinated Debt is the sole asset of each Trust, and the Trust Preferred Securities are the sole liabilities of each Trust. The Company purchased all of the outstanding common stock of the Trusts, and the investment in the Trusts is included in “other assets” in the accompanying consolidated balance sheets.   The following table summarizes the nature and terms of the Junior Subordinated Debt and Trust Preferred Securities: ​ James River Capital Trust I James River James River Capital Trust III James River Franklin ​ ($ in thousands) Issue date May 26, 2004 December 15, 2004 June 15, 2006 December 11, 2007 January 10, 2008 Principal amount of Trust Preferred Securities $7,000 $15,000 $20,000 $54,000 $30,000 Principal amount of Junior Subordinated Debt $7,217 $15,464 $20,619 $55,670 $30,928 Carrying amount of Junior Subordinated Debt net of repurchases $7,217 $15,464 $20,619 $44,827 $15,928 Maturity date of Junior Subordinated Debt, unless accelerated earlier May 24, 2034 December 15, 2034 June 15, 2036 December 15, 2037 March 15, 2038 Trust common stock $217 $464 $619 $1,670 $928 Interest rate, per annum Three-Month LIBOR plus 4.0% Three-Month LIBOR plus 3.4% Three-Month LIBOR plus 3.0% Three-Month LIBOR plus 3.1% Three-Month LIBOR plus 4.0% All of the Junior Subordinated Debt is currently redeemable at 100.0% of the unpaid principal amount at the Company’s option. Interest on the Trust Preferred Securities and interest paid to the Trusts on the Junior Subordinated Debt is payable quarterly in arrears at a per annum rate as described in the table above. The Company has the right to defer interest payments on the Junior Subordinated Debt for up to five years without triggering an event of default. The Trust Preferred Securities are subject to mandatory redemption in a like amount (a) upon repayment of all of the Junior Subordinated Debt on the stated maturity date, (b) contemporaneously with the optional prepayment of all of the Junior Subordinated Debt in conjunction with a special event (as defined), and (c) five years or more after the issue date, contemporaneously with the optional prepayment, in whole or in part, of the Junior Subordinated Debt. The Indentures contain certain covenants which the Company is in compliance with as of December 31, 2019 . Interest payable is included in “accrued expenses” on the accompanying consolidated balance sheets.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Capital Stock	Capital Stock ​ The Company’s authorized share capital consists of 200,000,000 common shares, par value $0.0002 per share ( 30,424,391 shares issued and outstanding at December 31, 2019 ) and 20,000,000 undesignated preferred shares, par value $0.00125 per share ( no shares issued or outstanding). Share activity in 2018 and 2019 includes issuances from stock option exercises and RSU vesting, increasing the number of common shares outstanding from 29,696,682 at December 31, 2017 to 29,988,460 at December 31, 2018 and 30,424,391 at December 31, 2019 . The Company has 4,325,963 common shares reserved for future issuance upon exercise or vesting of equity awards, as applicable. The Board of Directors declared the following cash dividends in 2019 , 2018 , and 2017 : Date of Declaration Dividend per Common Share Payable to Shareholders of Record on Payment Date Total Amount 2019 February 20, 2019 $0.30 March 11, 2019 March 29, 2019 $ 9,146,357 April 30, 2019 $0.30 June 10, 2019 June 28, 2019 $ 9,204,804 July 30, 2019 $0.30 September 16, 2019 September 30, 2019 $ 9,230,801 November 5, 2019 $0.30 December 16, 2019 December 31, 2019 $ 9,228,656 Total $1.20 $ 36,810,618 2018 ​ ​ ​ February 22, 2018 $0.30 March 12, 2018 March 30, 2018 $ 9,049,476 May 1, 2018 $0.30 June 11, 2018 June 29, 2018 $ 9,066,023 August 1, 2018 $0.30 September 10, 2018 September 28, 2018 $ 9,080,519 November 7, 2018 $0.30 December 14, 2018 December 28, 2018 $ 9,088,542 Total $1.20 $ 36,284,560 2017 February 14, 2017 $0.30 March 13, 2017 March 31, 2017 $ 8,878,147 May 2, 2017 $0.30 June 12, 2017 June 30, 2017 $ 8,917,471 August 1, 2017 $0.30 September 11, 2017 September 29, 2017 $ 8,943,279 November 1, 2017 $0.30 December 15, 2017 December 28, 2017 $ 8,974,196 November 1, 2017 $0.50 December 15, 2017 December 28, 2017 $ 14,956,994 Total $1.70 $ 50,670,087 Included in the dividends are $433,000 , $391,000 and $450,000 of dividend equivalents on RSUs, of which $623,000 , $557,000 and $434,000 were payable as of December 31, 2019 , 2018 , and 2017 , respectively.

Equity Awards

Equity Awards	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Equity Awards	Equity Awards ​ Equity Incentive Plans The Company’s shareholders have approved various equity incentive plans, including the Amended and Restated 2009 Equity Incentive Plan (the “Legacy Plan”), the 2014 Long Term Incentive Plan (“2014 LTIP”), and the 2014 Non-Employee Director Incentive Plan (“2014 Director Plan”) (collectively, the “Plans”). All awards issued under the Plans are issued at the discretion of the Board of Directors. Under the Legacy Plan, employees received non-qualified stock options. Options are outstanding under the Legacy Plan; however, no additional awards may be granted. Employees are eligible to receive non-qualified stock options, incentive stock options, share appreciation rights, performance shares, restricted shares, RSUs, and other awards under the 2014 LTIP. The maximum number of shares available for issuance under the 2014 LTIP is 4,171,150 , and at December 31, 2019 , 1,575,359 shares are available for grant. Non-employee directors of the Company are eligible to receive non-qualified stock options, share appreciation rights, performance shares, restricted shares, RSUs, and other awards under the 2014 Director Plan. At the 2019 Annual General Meeting of Shareholders of the Company held on April 30, 2019, the Company's shareholders approved an amendment to the 2014 Director Plan. The Board of Directors of the Company had previously approved the amendment. The amendment increased the number of the Company's common shares authorized for issuance under the 2014 Director Plan by 100,000 shares. The maximum number of shares available for issuance under the 2014 Director Plan is 150,000 , and at December 31, 2019 , 108,594 shares are available for grant. Generally, awards issued under the 2014 LTIP and 2014 Director Plan vest immediately in the event that an award recipient is terminated without Cause (as defined), and in the case of the 2014 LTIP for Good Reason (as defined), at any time following a Change in Control (as defined in the applicable plans). Options The following table summarizes the option activity: ​ Year Ended December 31, ​ 2019 2018 2017 ​ Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Outstanding: ​ ​ ​ ​ ​ ​ Beginning of year 1,115,324 $ 29.02 1,479,236 $ 27.81 2,234,699 $ 22.84 Granted — $ — — $ — 205,244 $ 42.24 Exercised (459,415 ) $ 26.87 (308,025 ) $ 22.01 (898,218 ) $ 18.53 Forfeited (12,058 ) $ 36.84 (55,887 ) $ 35.69 (62,489 ) $ 30.80 End of year 643,851 $ 30.41 1,115,324 $ 29.02 1,479,236 $ 27.81 Exercisable, end of year 590,340 $ 29.34 814,421 $ 26.46 846,371 $ 22.35 All of the outstanding options vest over three years and have a contractual life of seven years from the original date of grant. All of the outstanding options have an exercise price equal to the fair value of the underlying shares at the date of grant. The intrinsic value of each option is determined based on the difference between the fair value of the underlying share and the exercise price of the underlying option. The total intrinsic value of options exercised during 2019 , 2018 and 2017 was $8.2 million , $4.6 million and $20.4 million , respectively. The aggregate intrinsic value of options outstanding at December 31, 2019 , 2018 and 2017 was $7.1 million , $9.4 million and $18.5 million , respectively. The aggregate intrinsic value of options exercisable at December 31, 2019 , 2018 and 2017 was $7.1 million , $8.5 million and $14.9 million , respectively. The fair value used for calculating intrinsic values was $41.21 , $36.54 and $40.01 at December 31, 2019 , 2018 and 2017 , respectively. The weighted-average remaining contractual life of the options outstanding and options exercisable at December 31, 2019 is 2.9 years and 2.8 years , respectively. There were no options granted in 2019 or 2018 . The weighted-average fair value of options granted during 2017 was $8.21 . The value of the options granted was estimated at the date of grant using the Black-Scholes-Merton option pricing model using the following assumptions: ​ Year Ended December 31, ​ 2017 Risk-free interest rate 1.97 % Dividend yield 2.85 % Expected share price volatility 27.39 % Expected life 5.0 years The risk-free interest rate assumption is based on the five-year U.S. Treasury rate at the date of the grant. The dividend yield assumption was based upon dividends expected to be declared over the life of the options at the date of grant. The share price volatility assumption was based upon the Company's 100-day realized volatility. The expected life is determined using the simplified method, which factors in the average of the midpoint and the contractual term of each tranche in determining a single expected life. The simplified method is used as the Company does not have sufficient historical exercise data to estimate an expected term. The Black-Scholes-Merton option pricing model was developed for use in estimating the fair value of traded options that have no vesting restrictions and are fully transferable. In addition, option valuation models require the input of highly subjective assumptions including expected share price volatility. Because the Company’s share options have characteristics significantly different from those of traded options and because changes in the subjective input assumptions can materially affect the fair value estimate, the existing models do not necessarily provide a reliable single measure of the fair value of such share options. RSUs The following table summarizes RSU activity: ​ Year Ended December 31, ​ 2019 2018 2017 ​ Shares Weighted- Average Grant Date Fair Value Shares Weighted- Average Grant Date Fair Value Shares Weighted- Average Grant Date Fair Value Unvested, beginning of year 300,142 $ 39.22 178,882 $ 37.93 196,800 $ 24.38 Granted 197,078 $ 42.56 227,481 $ 39.74 137,034 $ 42.20 Vested (134,407 ) $ 37.99 (83,384 ) $ 37.61 (132,764 ) $ 24.24 Forfeited (22,445 ) $ 41.32 (22,837 ) $ 40.21 (22,188 ) $ 26.06 Unvested, end of year 340,368 $ 41.50 300,142 $ 39.22 178,882 $ 37.93 The vesting period of RSUs granted to employees range from one to five years and vest ratably over the respective vesting period, with the majority vesting in three years . All RSUs granted to date to non-employee directors had a one year vesting period. The total fair value of shares vested in 2019 , 2018 and 2017 was $5.3 million , $3.2 million and $5.5 million , respectively. The holders of RSUs are entitled to dividend equivalents. The dividend equivalents are settled in cash at the same time that the underlying RSUs vest and are subject to the same risk of forfeiture as the underlying shares. The fair value of the RSUs granted is based on the market price of the underlying shares. Compensation Expense Share based compensation expense is recognized on a straight line basis over the vesting period. The amount of expense and related tax benefit is summarized below: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Share based compensation expense $ 7,178 $ 6,228 $ 7,688 U.S. tax benefit on share based compensation expense $ 872 $ 716 $ 2,093 As of December 31, 2019 , the Company had $8.6 million of unrecognized share based compensation expense expected to be charged to earnings over a weighted-average period of 1.7 years .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes ​ Under current Bermuda law, James River Group Holdings, Ltd. and its Bermuda based subsidiaries, JRG Re and Carolina Re, are not required to pay any Bermuda taxes on their income or capital gains. Those companies have received an undertaking from the Minister of Finance in Bermuda that, in the event of any taxes being imposed, the Company will be exempt from taxation in Bermuda until March 2035. Distributions from the Company’s U.S. subsidiaries to its U.K. intermediate holding company, James River UK, are generally subject to a 5% dividend withholding tax. James River Group paid a $21.1 million dividend to James River UK during 2017 and remitted $1.1 million of dividend withholding taxes to the U.S. tax authorities for the year ending December 31, 2017 . No similar distributions occurred in 2019 or 2018. The Company’s U.S. subsidiaries are subject to federal, state and local corporate income taxes, and other taxes applicable to U.S. corporations. In addition, Carolina Re is subject to Federal income taxes as a result of its irrevocable election to be taxed as a U.S. domestic corporation under Section 953(d) of the Code. The Company’s U.S.-domiciled subsidiaries and Carolina Re file a consolidated U.S. federal income tax return. The Company’s U.S.-based subsidiaries are generally no longer subject to income tax examination by U.S. income tax authorities for the tax years ending before January 1, 2016. Financial results for 2017 reflect provisional amounts related to the December 2017 enactment of the Tax Act. The Company did not record any amounts related to the changes in loss reserve discounting required by the Tax Act during 2017. These changes required the Internal Revenue Service to publish new discount factors based on loss payment patterns and interest rates determined under the Tax Act. During 2018, factors were published that allowed the Company to adjust its current and deferred tax liabilities based on the provisions of the Tax Act. The Tax Act has specific transition provisions associated with reserve discounting. The initial impact of the proposed regulations in 2018 was an increase to our deferred tax asset for the additional discount as of December 31, 2017 of $8.8 million offset by an increase to our deferred tax liability of $8.8 million representing the 8 year transition provision required by the Tax Act. During 2018, $1.1 million of this transition provision was recognized in our current provision and adjusted out of our deferred tax liability. The regulations were finalized in 2019, and the remaining reserve adjustment at December 31, 2019 based on these final regulations is $5.7 million to be recognized over the next six years at $950,000 per year. There were other provisions of the Tax Act for which the Company finalized its estimates during 2018, and the impact of these was immaterial. The expected income tax provision computed from pre-tax income at the weighted-average tax rate has been calculated as the sum of the pre-tax income in each jurisdiction multiplied by that jurisdiction’s applicable Federal statutory tax rate. Federal statutory tax rates of 0% and 21% have been used in 2019 and 2018 for Bermuda and the U.S., respectively. A Federal statutory rate of 35% has been used for the U.S. in 2017. U.S. deferred taxes were remeasured at 21% at December 31, 2017. U.S. income before Federal income taxes was $70.7 million , $37.5 million , and $50.1 million for the years ending December 31, 2019 , 2018 , and 2017 , respectively. A reconciliation of the difference between the Company’s Federal income tax provision on U.S. income and the expected Federal tax provision on U.S. income using the weighted-average tax rate as well as a reconciliation to total tax expense is as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Federal income tax expense at applicable statutory rates $ 14,843 $ 7,875 $ 17,541 Tax-exempt investment income (230 ) (272 ) (586 ) Dividends received deduction (307 ) (307 ) (792 ) Excess tax benefits on share based compensation (1,099 ) (567 ) (2,114 ) Effect of tax rate reduction on deferred tax liability — 220 (3,498 ) Other 99 145 (90 ) Federal income tax expense $ 13,306 $ 7,094 $ 10,461 U.S. state income tax expense (benefit) 222 (86 ) 65 U.S. dividend withholding tax — — 1,053 Total income tax expense $ 13,528 $ 7,008 $ 11,579 The significant components of net deferred tax assets (liabilities) at the corporate income tax rate of 21% for the years ended December 31, 2019 and 2018 are summarized as follows: ​ December 31, ​ 2019 2018 ​ (in thousands) Deferred tax assets: ​ ​ Accrued compensation expenses $ 2,563 $ 2,456 Reserve for losses and loss adjustment expenses 12,286 7,482 Unearned premiums 8,226 5,711 Share based compensation 1,482 1,352 Allowance for doubtful accounts 1,188 829 Property and equipment 16 1,909 Other 1,974 1,903 Total deferred tax assets 27,735 21,642 Deferred tax liabilities: Intangible assets 7,381 7,461 Net unrealized gains 5,792 887 Deferred policy acquisition costs 4,448 3,491 Equity method investments 9,316 8,582 Other 134 167 Total deferred tax liabilities 27,071 20,588 Net deferred tax assets $ 664 $ 1,054 Deferred income taxes have not been accrued with respect to certain undistributed earnings of foreign subsidiaries. If the earnings were to be distributed, as dividends or otherwise, such amounts may be subject to withholding taxation in the jurisdiction of the paying entity. The Company asserts that U.S. unremitted earnings as of December 31, 2019 will be permanently reinvested in the U.S. and, accordingly, no provision for withholding taxes arising in respect to U.S. unremitted earnings has been made. The Company had no reserve for future tax contingencies or liabilities (“unrecognized tax benefits”) at December 31, 2019 or 2018 . The U.S. imposes a 1% excise tax on reinsurance premiums paid to non-U.S. reinsurers with respect to risks located in the U.S. The rates of tax are established based on the nature of the risk, unless reduced by an applicable U.S. tax treaty. For the years ended December 31, 2019 , 2018 , and 2017 , the Company paid $586,000 , $823,000 , and $3.4 million , respectively, of federal excise taxes on its intercompany reinsurance transactions. The Company also paid excise taxes of $1.5 million , $2.1 million , and $2.2 million for the years ended December 31, 2019 , 2018 , and 2017 , respectively, on written premiums assumed from third-party insurers with respect to risks located in the U.S. These excise taxes are reflected as “other operating expenses” in the Company’s consolidated income statements.

Other Operating Expenses and Ot

Other Operating Expenses and Other Expenses	12 Months Ended
	Dec. 31, 2019
Other Operating Expenses And Other Expenses [Abstract]
Other Operating Expenses and Other Expenses	Other Operating Expenses and Other Expenses ​ Other operating expenses consist of the following: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Amortization of policy acquisition costs $ 83,893 $ 111,103 $ 116,001 Other underwriting expenses of the insurance segments 59,351 63,029 55,662 Other operating expenses of the Corporate and Other segment 27,664 26,903 25,330 Total $ 170,908 $ 201,035 $ 196,993 Other expenses consist of the following: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Employee severance $ 1,055 $ 1,386 $ 147 Income on leased building the Company was previously deemed to own for accounting purposes — (623 ) (248 ) Legal and professional services related to secondary share offerings — 337 535 Other — — 105 Impairment of intangible asset — 200 — Total $ 1,055 $ 1,300 $ 539

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits ​ The Company and its subsidiaries offer savings plans (the “Savings Plans”) which qualify under Section 401(k) of the U.S. Internal Revenue Code. Participants may contribute certain percentages of their pre-tax salary to the Savings Plans subject to statutory limitations. The Company and its subsidiaries match employee contributions at various rates up to a maximum contribution of 6.0% of the participant’s earnings subject to certain statutory limits. For the years ended December 31, 2019 , 2018 , and 2017 , the expense associated with the Savings Plans totaled $3.2 million , $2.9 million , and $2.5 million , respectively.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities ​ The Company is a party to various lawsuits arising in the ordinary course of its operations. The Company believes that the ultimate resolution of these matters will not materially impact its financial position, cash flows, or results of operations. The Company’s reinsurance subsidiary, JRG Re, entered into three letter of credit facilities with banks as security to third-party reinsureds on reinsurance assumed by JRG Re. JRG Re has established custodial accounts to secure these letters of credit. Under a $75.0 million facility, $22.7 million of letters of credit were issued through December 31, 2019 which were secured by deposits of $35.9 million . Under the 2013 Facility, $77.6 million of letters of credit were issued through December 31, 2019 which were secured by deposits of $93.9 million . Under the 2017 Facility, $21.9 million of letters of credit were issued through December 31, 2019 which were secured by deposits of $51.5 million . JRG Re has also established trust accounts to secure its obligations to selected reinsureds. The total amount deposited in the trust accounts for the benefit of third-party reinsureds was $283.2 million at December 31, 2019 . The Company previously issued a set of insurance contracts to Rasier under which the Company pays losses and loss adjustment expenses on the contracts. The Company has indemnity agreements with Rasier (non-insurance entities) and is contractually entitled to receive reimbursement for a significant portion of the losses and loss adjustment expenses paid on behalf of Rasier and other expenses incurred by the Company. Rasier is required to collateralize all amounts currently due to the Company and to provide additional collateral sufficient to cover the amounts that may be recoverable under the indemnity agreements, including, among other things, case loss and loss adjustment expense reserves, IBNR loss and loss adjustment expense reserves, extra contractual obligations and excess of policy limits liabilities. The collateral is provided through a collateral trust arrangement established in favor of the Company by a captive insurance company affiliate of Rasier. As permitted under our indemnification agreements with Rasier and the associated trust agreement, we have withdrawn the collateral posted to the trust account. At December 31, 2019 , the Company held collateral funds of $1,199.2 million . The funds withdrawn from the trust account, currently invested in short term U.S. Treasury securities and included in restricted cash equivalents on the Company's consolidated balance sheet, will be used to reimburse the Company for the losses and loss adjustment expenses paid on behalf of Rasier and other related expenses incurred by the Company to the extent not paid as required under the indemnity agreements. The Company has ongoing exposure to estimated losses and expenses on these contracts growing at a faster pace than growth in our collateral balances. In addition, we have credit exposure if our estimates of future losses and loss adjustment expenses and other amounts recoverable, which are the basis for establishing collateral balances, are lower than actual amounts paid or payable. The amount of our credit exposure in any of these instances could be material. To mitigate these risks, we closely and frequently monitor our exposure compared to our collateral held, and we request additional collateral when our analysis indicates that we have uncollateralized exposure.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) The following table summarizes the components of other comprehensive income (loss): ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Unrealized gains (losses) arising during the period, before U.S. income taxes $ 51,381 $ (23,201 ) $ 11,091 U.S. income taxes (3,510 ) 483 (2,374 ) Unrealized gains (losses) arising during the period, net of U.S. income taxes 47,871 (22,718 ) 8,717 Less reclassification adjustment: Net realized investment gains (losses) 1,081 (554 ) (835 ) U.S. income taxes (152 ) 39 333 Reclassification adjustment for investment gains (losses) realized in net income 929 (515 ) (502 ) Other comprehensive income (loss) $ 46,942 $ (22,203 ) $ 9,219 In addition to the $1.1 million of net realized investment gains and $554,000 and $835,000 of net realized investment losses on available-for-sale fixed maturity securities for the years ended December 31, 2019 , 2018 , and 2017 , the Company recognized $10.1 million of net realized and unrealized investment losses, $1.1 million of net realized and unrealized investment gains, and $1.2 million of net realized and unrealized investment losses in the respective years on its investments in bank loan participations. Net realized and unrealized gains and losses on investments for 2019 and 2018 also include $6.3 million of net gains and $6.0 million of net losses, respectively, for the change in net unrealized gains on equity securities in accordance with the Company's adoption of ASU 2016-01 effective January 1, 2018.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information ​ The Company has four reportable segments, three of which are separately managed business units and the fourth (“Corporate and Other”) includes the Company’s remaining operations. The Excess and Surplus Lines segment primarily offers commercial excess and surplus lines liability and excess property insurance products. The Specialty Admitted Insurance segment offers workers’ compensation insurance coverage as well as specialty admitted fronting and program business. The Casualty Reinsurance segment offers commercial liability and non-catastrophe property reinsurance to U.S. insurance companies and to the Company’s U.S.-based insurance subsidiaries. The Corporate and Other segment consists of certain management and treasury activities of James River Group, James River UK, and JRG Holdings as well as interest expense associated with senior debt and Junior Subordinated Debt, and investment income from investments classified as trading or other invested assets. The accounting policies of the reportable segments are the same as those described in the summary of significant accounting policies. Segment revenues for each reportable segment consist of net earned premiums, net investment income, and realized and unrealized (losses) gains on investments. Segment profit (loss) for each reportable segment is measured by underwriting profit (loss), which is generally defined as net earned premiums less losses and loss adjustment expenses and other operating expenses of the operating segments. Gross fee income of the Excess and Surplus Lines segment is included in that segment’s underwriting profit (loss). Gross fee income of $9.1 million , $13.9 million and $17.0 million was included in underwriting profit for the years ended December 31, 2019 , 2018 and 2017 , respectively. Segment results are reported prior to the effects of the intercompany reinsurance agreements between the Company’s insurance subsidiaries. All gross written premiums and net earned premiums for all periods presented were generated from policies issued to U.S. based insureds. ​ Excess and Surplus Lines Specialty Admitted Insurance Casualty Reinsurance Corporate and Other Total ​ (in thousands) As of and for the Year Ended December 31, 2019 ​ ​ ​ ​ ​ Gross written premiums $ 922,320 $ 387,642 $ 160,773 $ — $ 1,470,735 Net earned premiums 625,528 54,338 143,880 — 823,746 Segment revenues 657,501 61,241 183,700 4,683 907,125 Net investment income 21,358 3,802 46,325 4,167 75,652 Interest expense — — — 10,596 10,596 Underwriting profit (loss) of operating segments 19,157 5,913 (7,161 ) — 17,909 Segment goodwill 181,831 — — — 181,831 Segment assets 2,481,934 786,433 1,699,473 56,565 5,024,405 As of and for the Year Ended December 31, 2018 ​ ​ ​ ​ ​ Gross written premiums $ 656,538 $ 374,346 $ 135,889 $ — $ 1,166,773 Net earned premiums 555,684 55,146 204,568 — 815,398 Segment revenues 580,785 56,717 243,178 4,919 885,599 Net investment income 14,456 3,262 38,838 4,700 61,256 Interest expense — — — 11,553 11,553 Underwriting profit of operating segments 42,834 6,972 5,103 — 54,909 Segment goodwill 181,831 — — — 181,831 Segment assets 972,111 633,689 1,453,754 77,222 3,136,776 As of and for the Year Ended ​ ​ ​ ​ ​ Gross written premiums $ 530,120 $ 316,430 $ 235,355 $ — $ 1,081,905 Net earned premiums 463,521 68,110 209,478 — 741,109 Segment revenues 493,853 70,366 240,751 12,655 817,625 Net investment income 15,014 2,532 31,507 12,066 61,119 Interest expense — — — 8,974 8,974 Underwriting profit (loss) of operating segments 29,693 3,166 (1,765 ) — 31,094 Segment goodwill 181,831 — — — 181,831 Segment assets 843,486 439,416 1,379,866 93,927 2,756,695 The following table reconciles the underwriting profit (loss) of operating segments by individual segment to income before taxes: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Underwriting profit (loss) of the operating segments: ​ ​ ​ Excess and Surplus Lines $ 19,157 $ 42,834 $ 29,693 Specialty Admitted Insurance 5,913 6,972 3,166 Casualty Reinsurance (7,161 ) 5,103 (1,765 ) Total underwriting profit of operating segments 17,909 54,909 31,094 Other operating expenses of the Corporate and Other segment (27,664 ) (26,903 ) (25,330 ) Underwriting (loss) profit (9,755 ) 28,006 5,764 Net investment income 75,652 61,256 61,119 Net realized and unrealized losses on investments (2,919 ) (5,479 ) (1,989 ) Other income 1,137 505 361 Other expenses (1,055 ) (1,300 ) (539 ) Interest expense (10,596 ) (11,553 ) (8,974 ) Amortization of intangible assets (597 ) (597 ) (597 ) Income before income taxes $ 51,867 $ 70,838 $ 55,145 The Company currently has 15 underwriting divisions, including 13 in the Excess and Surplus Lines segment, one in the Specialty Admitted Insurance segment, and one in the Casualty Reinsurance segment. Each underwriting division focuses on a specific industry group or coverage. Gross written premiums by segment and underwriting division are presented below: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Commercial Auto $ 405,565 $ 322,126 $ 247,960 Excess Casualty 118,954 66,452 51,160 General Casualty 115,832 54,127 38,097 Manufacturers and Contractors 105,096 79,160 85,719 Energy 45,442 33,942 29,704 Excess Property 31,606 16,963 14,447 Allied Health 26,713 30,450 19,181 Life Sciences 24,462 16,636 12,981 Small Business 19,725 14,808 11,307 Environmental 16,539 10,499 7,920 Professional Liability 6,441 5,916 6,326 Sports and Entertainment 4,212 3,685 3,021 Medical Professionals 1,733 1,774 2,297 Total Excess and Surplus Lines segment 922,320 656,538 530,120 Specialty Admitted Insurance segment 387,642 374,346 316,430 Casualty Reinsurance segment 160,773 135,889 235,355 Total $ 1,470,735 $ 1,166,773 $ 1,081,905 The Company does business with three brokers that generated $472.6 million , $115.2 million and $98.6 million of gross written premiums for the Excess and Surplus Lines segment for the year ended December 31, 2019 , representing 32.1% (BB&T Insurance Services), 7.8% and 6.7% of consolidated gross written premiums and 51.2% , 12.5% and 10.7% of the Excess and Surplus Lines segment’s gross written premiums, respectively. The Company has agency contracts with various branches within the aforementioned brokers. No other broker generated 10.0% or more of the gross written premiums for the Excess and Surplus Lines segment for the year ended December 31, 2019 . The Company did business with one insured (Rasier, whose insurance policies were canceled as of December 31, 2019) that generated $374.2 million of gross written premiums and $9.1 million of gross fee income for the Excess and Surplus Lines segment for the year ended December 31, 2019 , representing 25.4% of consolidated gross written premiums and 40.6% of the Excess and Surplus Lines segment’s gross written premiums. No other insured generated 10.0% or more of the gross written premiums for the Excess and Surplus Lines segment. The Specialty Admitted Insurance segment accepts applications for insurance from a variety of sources, including independent retail agents, program administrators and managing general agents (“MGAs”). The Company does business with two agencies that generated $146.5 million (Atlas General Insurance Services) and $53.2 million of gross written premiums for the Specialty Admitted Insurance segment for the year ended December 31, 2019 , representing 10.0% and 3.6% of the consolidated gross written premiums and 37.8% and 13.7% of the Specialty Admitted Insurance segment’s gross written premiums, respectively. No other agency generated 10.0% or more of the gross written premiums for the Specialty Admitted Insurance segment for the year ended December 31, 2019 . The Company does business with four brokers that generated $53.7 million , $45.1 million , $42.4 million , and $16.7 million of gross written premiums for the Casualty Reinsurance segment for the year ended December 31, 2019 , representing 3.7% , 3.1% , 2.9% , and 1.1% of consolidated gross written premiums and 33.4% , 28.1% , 26.4% , and 10.4% of the Casualty Reinsurance segment’s gross written premiums, respectively. No other broker generated 10.0% or more of the gross written premiums for the Casualty Reinsurance segment for the year ended December 31, 2019 . The Casualty Reinsurance segment assumed business from three unaffiliated ceding companies that generated $96.4 million , $30.7 million , and $22.6 million of gross written premiums for the year ended December 31, 2019 , representing 6.6% , 2.1% , and 1.5% of consolidated gross written premiums and 59.9% , 19.1% , and 14.0% of the Casualty Reinsurance segment’s gross written premiums, respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements ​ Three levels of inputs are used to measure fair value of financial instruments: (1) Level 1: quoted price (unadjusted) in active markets for identical assets, (2) 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 instrument, and (3) Level 3: inputs to the valuation methodology are unobservable for the asset or liability. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants on the measurement date. To measure fair value, the Company obtains quoted market prices for its investment securities from its outside investment managers. If a quoted market price is not available, the Company uses prices of similar securities. Values for U.S. Treasury and publicly-traded equity securities are generally based on Level 1 inputs which use the market approach valuation technique. The values for all other fixed maturity securities (including state and municipal securities and obligations of U.S. government corporations and agencies) generally incorporate significant Level 2 inputs, and in some cases, Level 3 inputs, using the market approach and income approach valuation techniques. There have been no changes in the Company’s use of valuation techniques since December 31, 2017. The Company reviews fair value prices provided by its outside investment managers for reasonableness by comparing the fair values provided by the managers to those provided by its investment custodian. The Company also reviews and monitors changes in unrealized gains and losses. The Company has not historically adjusted security prices. The Company obtains an understanding of the methods, models and inputs used by the investment managers and independent pricing services, and controls are in place to validate that prices provided represent fair values. The Company’s control process includes, but is not limited to, initial and ongoing evaluation of the methodologies used, a review of specific securities and an assessment for proper classification within the fair value hierarchy, and obtaining and reviewing internal control reports for our investment manager that obtains fair values from independent pricing services. Assets measured at fair value on a recurring basis as of December 31, 2019 are summarized below: Fair Value Measurements Using ​ Quoted Prices in Active Markets for Identical Assets Level 1 Significant Other Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total ​ (in thousands) Fixed maturity securities, available-for-sale: ​ ​ ​ ​ State and municipal $ — $ 167,101 $ — $ 167,101 Residential mortgage-backed — 264,146 — 264,146 Corporate — 632,221 — 632,221 Commercial mortgage and asset-backed — 252,457 252,457 U.S. Treasury securities and obligations guaranteed by the U.S. government 115,173 494 — 115,667 Redeemable preferred stock — 2,034 — 2,034 Total fixed maturity securities, available-for-sale $ 115,173 $ 1,318,453 $ — $ 1,433,626 Equity securities: Preferred stock $ — $ 62,747 $ — $ 62,747 Common stock 14,669 3,276 43 17,988 Total equity securities $ 14,669 $ 66,023 $ 43 $ 80,735 Short-term investments $ — $ 156,925 $ — $ 156,925 Assets measured at fair value on a recurring basis as of December 31, 2018 are summarized below: ​ Fair Value Measurements Using ​ Quoted Prices in Active Markets for Identical Assets Level 1 Significant Other Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total ​ ​ (in thousands) Fixed maturity securities, available-for-sale: ​ ​ ​ ​ State and municipal $ — $ 149,295 $ — $ 149,295 Residential mortgage-backed — 204,109 — 204,109 Corporate — 524,768 — 524,768 Commercial mortgage and asset-backed — 192,797 4,228 197,025 U.S. Treasury securities and obligations guaranteed by the U.S. government 106,651 542 — 107,193 Redeemable preferred stock — 1,812 — 1,812 Total fixed maturity securities, available-for-sale $ 106,651 $ 1,073,323 $ 4,228 $ 1,184,202 Equity securities: Preferred stock $ — $ 60,740 $ — $ 60,740 Common stock 16,674 757 214 17,645 Total equity securities $ 16,674 $ 61,497 $ 214 $ 78,385 Short-term investments $ 1,250 $ 80,716 $ — $ 81,966 A reconciliation of the beginning and ending balances of available-for-sale fixed maturity securities and equity securities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) is shown below: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Beginning balance $ 4,442 $ 4,680 $ 5,000 Transfers in to Level 3 3,010 — — Transfers out of Level 3 (7,238 ) — — Purchases 214 — Sales — — — Maturities and calls (452 ) (320 ) Amortization of discount — — — Total gains or losses (realized/unrealized): Included in earnings (171 ) — — Included in other comprehensive income — — — Ending balance $ 43 $ 4,442 $ 4,680 The Company held one available-for-sale fixed maturity security at December 31, 2018 and 2017 for which the fair value was determined using significant unobservable inputs (Level 3). A market approach using prices in trades of comparable securities was utilized to determine a fair value of $4.2 million for the security at December 31, 2018 and $4.7 million at December 31, 2017 . During 2019 a principle payment of $456,000 was received and the Company was able to obtain a quoted price from a pricing vendor for the security. The available-for-sale fixed maturity security was transferred to Level 2. The Company held one equity security at December 31, 2019 and 2018 for which the fair value was determined using significant unobservable inputs (Level 3). A market approach using prices in trades of comparable securities was utilized to determine a fair value for the equity security of $43,000 at December 31, 2019 and $214,000 at December 31, 2018 . During 2019 , one equity security was transferred from Level 1 to Level 3 as the security was no longer actively traded. The Company was then able to obtain a quoted price from a pricing vendor for the equity security and it was transferred from Level 3 to Level 2. Transfers out of Level 3 occur when the Company is able to obtain reliable prices from pricing vendors for which the Company was previously unable to obtain reliable prices. Transfers in to Level 3 occur when the Company is unable to obtain reliable prices for securities from pricing vendors and instead must use broker price quotes. There were no transfers between Level 1 and Level 2 during 2019 , 2018 or 2017 . The Company recognizes transfers between levels at the beginning of the reporting period. Total losses of $171,000 were included in earnings for the year ended December 31, 2019 attributable to the change in unrealized losses relating to the one Level 3 asset valued at fair value on a recurring basis that is still held at December 31, 2019 . The Company measures certain bank loan participations at fair value on a non-recurring basis during the year as part of the Company’s impairment evaluation when loans are determined by management to be impaired. Assets measured at fair value on a nonrecurring basis are summarized below: ​ Fair Value Measurements Using ​ Quoted Prices in Active Markets for Identical Assets Level 1 Significant Other Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total ​ (in thousands) December 31, 2019 ​ ​ ​ ​ Bank loan participations held-for-investment $ — $ — $ 6,949 $ 6,949 December 31, 2018 Bank loan participations held-for-investment $ — $ — $ — $ — Bank loan participations held for investment that were determined to be impaired were written down to their fair value of $6.9 million at December 31, 2019 . Management concluded that none of the bank loan participations held-for-investment were impaired as of December 31, 2018 . In the determination of the fair value for bank loan participations and certain high yield bonds, the Company’s investment manager endeavors to obtain data from multiple external pricing sources. External pricing sources may include brokers, dealers and price data vendors that provide a composite price based on prices from multiple dealers. Such external pricing sources typically provide valuations for normal institutional size trading units of such securities using methods based on market transactions for comparable securities, and various relationships between securities, as generally recognized by institutional dealers. For investments in which the investment manager determines that only one external pricing source is appropriate or if only one external price is available, the relevant investment is generally recorded at fair value based on such price. Investments for which external sources are not available or are determined by the investment manager not to be representative of fair value are recorded at fair value as determined by the Company, with input from its investment managers and valuation specialists as considered necessary. In determining the fair value of such investments, the Company considers one or more of the following factors: type of security held, convertibility or exchangeability of the security, redeemability of the security (including the timing of redemptions), application of industry accepted valuation models, recent trading activity, liquidity, estimates of liquidation value, purchase cost, and prices received for securities with similar terms of the same issuer or similar issuers. There were no investments for which external sources were unavailable to determine fair value as of December 31, 2019 and 2018 . The carrying values and fair values of financial instruments are summarized below: ​ December 31, ​ 2019 2018 ​ Carrying Value Fair Value Carrying Value Fair Value ​ (in thousands) Assets ​ ​ ​ ​ Fixed maturity securities, available-for-sale $ 1,433,626 $ 1,433,626 $ 1,184,202 $ 1,184,202 Equity securities 80,735 80,735 78,385 78,385 Bank loan participations held-for-investment 260,864 252,423 260,972 250,697 Cash and cash equivalents 206,912 206,912 172,457 172,457 Restricted cash equivalents 1,199,164 1,199,164 — — Short-term investments 156,925 156,925 81,966 81,966 Other invested assets – notes receivable 13,250 18,756 13,250 18,687 Liabilities ​ ​ Senior debt 158,300 158,043 118,300 118,317 Junior subordinated debt 104,055 122,193 104,055 117,057 The fair values of fixed maturity securities and equity securities have been determined using quoted market prices for securities traded in the public market or prices using bid or closing prices for securities not traded in the public marketplace. The fair values of cash and cash equivalents and short-term investments approximate their carrying values due to their short-term maturity. The fair values of other invested assets-notes receivable, senior debt, and Junior Subordinated Debt at December 31, 2019 and 2018 were determined by calculating the present value of expected future cash flows under the terms of the note agreements or debt agreements, as applicable, discounted at an estimated market rate of interest at December 31, 2019 and 2018 , respectively. The fair values of bank loan participations held-for-investment, senior debt, and Junior Subordinated Debt at December 31, 2019 and 2018 were determined using inputs to the valuation methodology that are unobservable (Level 3).

Statutory Matters

Statutory Matters	12 Months Ended
	Dec. 31, 2019
Statutory Matters [Abstract]
Statutory Matters	Statutory Matters ​ U.S. U.S. state insurance laws and regulations prescribe accounting practices for determining statutory net income and capital and surplus for insurance companies. In addition, state regulators may permit statutory accounting practices that differ from prescribed practices. Statutory accounting practices prescribed or permitted by regulatory authorities for the Company’s insurance subsidiaries differ from U.S. GAAP. The principal differences between SAP and GAAP as they relate to the financial statements of the Company’s insurance subsidiaries are (a) policy acquisition costs are expensed as incurred under SAP, whereas they are deferred and amortized under GAAP, (b) certain assets are not admitted for purposes of determining surplus under SAP, (c) the classification and carrying amounts of investments in certain securities are different under SAP and GAAP, and (d) the criteria for providing asset valuation allowances and the methodologies used to determine the amount thereof are different under SAP and GAAP. Combined net income, statutory capital and surplus and minimum required statutory capital and surplus, as determined in accordance with statutory accounting practices, for the U.S. insurance subsidiaries as of December 31, 2019 , 2018 , and 2017 and for the years then ended are summarized as follows: ​ 2019 2018 2017 ​ (in thousands) Statutory net income $ 3,586 $ 6,770 $ 31,881 Statutory capital and surplus 266,715 241,668 219,132 Minimum required statutory capital and surplus 111,208 24,850 25,000 Risk-Based Capital (“RBC”) requirements promulgated by the National Association of Insurance Commissioners require property-casualty insurers to maintain minimum capitalization levels determined based on formulas incorporating various business risks of the insurance subsidiaries. As of December 31, 2019 , the insurance subsidiaries’ adjusted capital and surplus exceeds their authorized control level RBC. Bermuda The Company has two Bermuda-based insurance subsidiaries: JRG Re, a Class 3B insurer and Carolina Re, a Class 3A insurer. Under the Bermuda Insurance Act 1978 and related regulations, an insurer must maintain minimum statutory capital and surplus at the greater of a minimum solvency margin (“MSM”) and the Enhanced Capital Requirement (“ECR”), which is the higher of the MSM and capital calculated by the Bermuda Solvency Capital Requirement (“BSCR”) model or an approved internal model. The combined Bermuda insurers minimum statutory solvency margin required at December 31, 2019 was approximately $161.4 million ( 2018 : $161.3 million ). Actual combined statutory capital and surplus at December 31, 2019 was $502.6 million ( 2018 : $439.4 million ). The insurers had combined statutory net income of $53.2 million for 2019 , $86.5 million for 2018 , and $20.1 million for 2017 . The combined ECR for the year ended December 31, 2018 was $283.6 million . The BSCR models for the year ended December 31, 2019 will not be filed with the Bermuda Monetary Authority until April 30, 2020 . The Company believes that the minimum statutory capital and surplus requirements will be met. The insurers must also maintain a minimum liquidity ratio in which the value of its relevant assets is not less than 75.0% of the amount of its relevant liabilities for general business. Relevant assets include cash and cash equivalents, fixed maturities, quoted alternative investments, accrued interest income, premiums receivable, losses recoverable from reinsurers, and funds withheld. The relevant liabilities include total insurance provisions and other liabilities less deferred income taxes and letters of credit, guarantees and other instruments. As of December 31, 2019 the minimum liquidity ratio requirements were met.

Dividend Restrictions

Dividend Restrictions	12 Months Ended
	Dec. 31, 2019
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract]
Dividend Restrictions	Dividend Restrictions ​ U.S. The insurance statutes of the U.S.-based insurance subsidiaries’ states of domicile limit the amount of dividends that they may pay annually without first obtaining regulatory approval. Generally, the limitations are based on the greater of statutory net income for the preceding year or 10.0% of statutory surplus at the end of the preceding year. The maximum amount of dividends available to James River Group from its U.S. insurance subsidiaries during 2020 without regulatory approval is $26.7 million . However, U.S. insurance regulators have broad powers to prevent the reduction of statutory surplus to inadequate levels and could refuse to permit the payment of dividends. Distributions from the Company’s U.S.-based subsidiaries to its U.K. intermediate holding company, James River UK, are generally subject to a 5% dividend withholding tax. The payment of any dividends by the Company’s U.S.-based subsidiaries directly to a Bermuda-based entity is subject to U.S. taxes at a 30.0% tax rate. JRG Holdings has determined that earnings of its U.S. subsidiaries have been and will be indefinitely reinvested in U.S. operations. Bermuda The Bermuda Insurance Act of 1978 prohibits an insurer from declaring or paying a dividend if it is in breach of its minimum solvency margin, its enhanced capital requirement, or its minimum liquidity ratio, or if the declaration or payment of such dividend would cause such a breach. An insurer can declare or pay dividends without prior regulatory approval up to 25% of the total statutory capital and surplus. The maximum combined amount of dividends and return of capital available to us from our Bermuda insurers in 2019 is calculated to be approximately $125.6 million . However, this dividend amount is subject to annual enhanced solvency requirement calculations. As of December 31, 2019 , JRG Holdings had consolidated retained earnings of $89.6 million , all of which was available for the payment of dividends to shareholders.

Other Related Party Transaction

Other Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Other Related Party Transactions	Other Related Party Transactions ​ The Company leases a commercial office building which houses the Company’s Richmond, Virginia operations under the terms of a non-cancelable lease from an entity with which it is affiliated. The term of the lease, which has been amended from time to time, runs through 2026. Operating costs under the lease were $2.1 million , $2.6 million , and $2.4 million for the years ended December 31, 2019, 2018, and 2017, respectively. The Chief Executive Officer of the Company previously owned a plane that the Company periodically leased. Total fees paid by the Company for the use of this plane were $0 , $123,000 , and $314,000 for 2019 , 2018 , and 2017 , respectively. Upon the Company’s initial public offering in 2014, the Company entered into a consulting agreement (the “Consulting Agreement”) with one of the Company's Independent Directors. Under the terms of the Consulting Agreement, the director received $37,500 in 2017 for investment and other business consulting services. The Consulting Agreement was terminated on March 31, 2017.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 19, 2020 , the Board of Directors declared a cash dividend of $0.30 per share. The dividend is payable on March 31, 2020 to shareholders of record on March 16, 2020 . On February 19, 2020 , the Board of Directors granted awards under the 2014 LTIP and the 2014 Director Plan to the Company’s employees and directors. RSUs for 179,016 shares were awarded with a fair value on the date of grant of $43.55 per share. The RSUs vest over one to three year periods, depending on the award.

Unaudited Selected Quarterly Fi

Unaudited Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Unaudited Selected Quarterly Financial Data	Unaudited Selected Quarterly Financial Data The following is a summary of the unaudited quarterly results of operations: ​ 2019 Quarter 2019 ​ First Second Third Fourth Year ​ (in thousands, except per share data) Gross written premiums $ 327,334 $ 380,003 $ 388,228 $ 375,170 $ 1,470,735 Total revenues 214,127 220,374 231,474 241,150 907,125 Net income (loss) 22,728 20,307 (25,167 ) 20,471 38,339 Comprehensive income (loss) 42,988 41,039 (15,710 ) 16,964 85,281 Earnings (loss) per share: ​ ​ ​ ​ ​ Basic (1) $ 0.76 $ 0.67 $ (0.83 ) $ 0.67 $ 1.27 Diluted (1) $ 0.75 $ 0.66 $ (0.83 ) $ 0.67 $ 1.25 2018 Quarter 2018 First Second Third Fourth Year (in thousands, except per share data) Gross written premiums $ 298,116 $ 293,378 $ 279,969 $ 295,310 $ 1,166,773 Total revenues 218,344 228,041 224,692 214,522 885,599 Net income 15,633 16,984 19,581 11,632 63,830 Comprehensive (loss) income (2,914 ) 10,426 15,192 18,923 41,627 Earnings per share: ​ ​ ​ ​ ​ Basic (1) $ 0.53 $ 0.57 $ 0.65 $ 0.39 $ 2.14 Diluted (1) $ 0.52 $ 0.56 $ 0.64 $ 0.38 $ 2.11 (1) Since the weighted-average shares for the quarter are calculated independently of the weighted-average shares for the year, quarterly earnings per share may not total to annual earnings per share.

SCHEDULE I - Summary of Investm

SCHEDULE I - Summary of Investments - Other than Investments in Related Parties	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract]
Summary of Investments - Other than Investments in Related Parties	Summary of Investments—Other than Investments in Related Parties Type of Investment Cost or Amortized Cost Fair Value Amount at which shown on Balance Sheet (1) ​ (in thousands) Fixed maturity securities, available-for-sale: ​ ​ ​ State and municipal $ 159,894 $ 167,101 $ 167,101 Residential mortgage-backed 261,524 264,146 264,146 Corporate 611,304 632,221 632,221 Commercial mortgage and asset-backed 249,309 252,457 252,457 U.S. Treasury securities and obligations guaranteed by the U.S. government 114,477 115,667 115,667 Redeemable preferred stock 2,025 2,034 2,034 Total fixed maturity securities, available-for-sale 1,398,533 1,433,626 1,433,626 Equity securities, available-for-sale Preferred Stock 52,557 62,747 62,747 Common Stock 20,687 17,988 17,988 Total equity securities 73,244 80,735 80,735 Bank loan participations, held-for-investment, net of allowance 260,864 252,423 260,864 Short-term investments 156,925 156,925 156,925 Other invested assets 16,741 Total invested assets $ 1,948,891 (1) Differences between the amounts in this column and the amounts in the consolidated balance sheet are due to this schedule excluding investments in related parties. ​

SCHEDULE II - Condensed Financi

SCHEDULE II - Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Statements of financial information of parent company only (Parent Company)	Condensed Financial Information of Registrant Balance Sheets (Parent Company) ​ December 31, ​ 2019 2018 ​ (in thousands) Assets ​ ​ Cash and cash equivalents $ 1,521 $ 240 Investment in subsidiaries 987,221 882,407 Due from subsidiaries 7,371 5,775 Other assets 2,842 1,579 Total assets $ 998,955 $ 890,001 Liabilities and shareholders’ equity Liabilities: Accrued expenses $ 1,592 $ 2,322 Senior debt 143,300 103,300 Junior subordinated debt 15,928 15,928 Notes payable to subsidiary 40,000 40,000 Due to subsidiaries 18,822 18,605 Other liabilities 732 605 Total liabilities 220,374 180,760 Commitments and contingent liabilities Shareholders’ equity: Class A common shares 6 6 Additional paid-in capital 657,875 645,310 Retained earnings 89,586 79,753 Accumulated other comprehensive income (loss) 31,114 (15,828 ) Total shareholders’ equity 778,581 709,241 Total liabilities and shareholders’ equity $ 998,955 $ 890,001 See accompanying notes. SCHEDULE II​ JAMES RIVER GROUP HOLDINGS, LTD. AND SUBSIDIARIES Condensed Financial Information of Registrant Statements of Income and Comprehensive Income (Parent Company) ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Revenues: Other income $ 61 $ 58 $ 49 Total revenues 61 58 49 Expenses: Other operating expenses 14,267 13,768 10,375 Other expenses — 337 640 Interest expense 5,047 5,122 4,130 Total expenses 19,314 19,227 15,145 Loss before equity in net income of subsidiaries (19,253 ) (19,169 ) (15,096 ) Equity in net income of subsidiaries 57,592 82,999 58,662 Net income $ 38,339 $ 63,830 $ 43,566 Other comprehensive income (loss): Equity in other comprehensive earnings (losses) of subsidiaries 46,942 (22,203 ) 9,219 Total comprehensive income $ 85,281 $ 41,627 $ 52,785 See accompanying notes. SCHEDULE II​ JAMES RIVER GROUP HOLDINGS, LTD. AND SUBSIDIARIES Condensed Financial Information of Registrant Statements of Cash Flows (Parent Company) ​ Year Ended December 31, ​ 2019 2018 2017 Operating activities Net income $ 38,339 $ 63,830 $ 43,566 Adjustments to reconcile net income to net cash (used in) provided by operating activities: Provision for depreciation and amortization 182 176 176 Share based compensation expense 7,178 6,228 7,688 Equity in undistributed earnings of subsidiaries (49,592 ) 6,000 (23,662 ) Changes in operating assets and liabilities (2,782 ) (5,653 ) 684 Net cash (used in) provided by operating activities (6,675 ) 70,581 28,452 Investing activities Dividends from subsidiaries — — 20,000 Net cash provided by investing activities — — 20,000 Financing activities Dividends paid (36,720 ) (36,123 ) (50,832 ) Senior debt issuance 60,000 20,000 10,000 Senior debt repayments (20,000 ) — — Subsidiary note repayments — (60,000 ) — Debt issue costs paid (711 ) — — Issuances of common shares under equity incentive plans 8,286 5,172 1,708 Common share repurchases (2,899 ) (2,239 ) (9,448 ) Net cash provided by (used in) financing activities 7,956 (73,190 ) (48,572 ) Change in cash and cash equivalents 1,281 (2,609 ) (120 ) Cash and cash equivalents at beginning of period 240 2,849 2,969 Cash and cash equivalents at end of period $ 1,521 $ 240 $ 2,849 Supplemental information Interest paid $ 5,710 $ 5,052 $ 4,612 ​ See accompanying notes. SCHEDULE II​ JAMES RIVER GROUP HOLDINGS, LTD. AND SUBSIDIARIES Condensed Financial Information of Registrant Notes to Condensed Financial Statements 1. Accounting Policies Organization James River Group Holdings, Ltd. (the “Company”) is an exempted holding company registered in Bermuda, organized for the purpose of acquiring and managing insurance and reinsurance entities. Basis of Presentation The accompanying condensed financial statements have been prepared using the equity method. Under the equity method, the investment in consolidated subsidiaries is stated at cost plus equity in undistributed earnings of consolidated subsidiaries since the date of acquisition. These condensed financial statements should be read in conjunction with the Company’s consolidated financial statements. Estimates and Assumptions Preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying disclosures. Those estimates are inherently subject to change, and actual results may ultimately differ from those estimates. Adopted Accounting Standards Effective January 1, 2019, the Company adopted ASU 2016-02, Leases (Topic 842) . This update requires the recognition of a right-of-use asset and a corresponding lease liability, discounted to the present value, for all leases that extend beyond 12 months. The Company adopted the new standard using a modified retrospective transition method, applying the transition provisions at the beginning of the period of adoption. The Company elected the package of practical expedients permitted under the transition guidance within the new standard and did not elect to use hindsight in determining the lease term. Upon adoption of the new standard, the Company derecognized assets of $22.6 million and liabilities of $30.9 million associated with a lease that was designated as build-to-suit under the previous guidance, and recorded a cumulative-effect adjustment to increase retained earnings by $8.3 million . The Company recorded right-of-use assets of $17.2 million and lease liabilities of $17.8 million at adoption of the new standard associated with operating leases for office space in Bermuda, North Carolina, Virginia, Arizona, and Georgia. The new standard did not materially impact the Company's results of operations, earnings per share, or cash flows, and did not impact compliance under the covenants of the Company's current credit agreements.

SCHEDULE III - Supplementary In

SCHEDULE III - Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Supplementary Insurance Information	Supplementary Insurance Information (in thousands) ​ Deferred Reserve Unearned Net Net Losses Amortization Other Net December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ Excess and Surplus Lines $ 24,428 $ 1,245,581 $ 267,924 $ 625,528 $ 21,358 $ 528,133 $ 49,720 $ 87,326 $ 685,814 Specialty Admitted (2,902 ) 511,027 115,606 54,338 3,802 34,860 (3,560 ) 13,986 58,637 Casualty Reinsurance 40,480 288,898 140,847 143,880 46,325 109,109 37,733 41,932 151,699 Corporate and Other — — — — 4,167 — — 27,664 — Total $ 62,006 $ 2,045,506 $ 524,377 $ 823,746 $ 75,652 $ 672,102 $ 83,893 $ 170,908 $ 896,150 December 31, 2018 Excess and Surplus Lines $ 16,736 $ 960,562 $ 175,231 $ 555,684 $ 14,456 $ 437,904 $ 48,299 $ 88,865 $ 571,098 Specialty Admitted (1,829 ) 426,315 84,659 55,146 3,262 32,623 (1,792 ) 15,551 55,840 Casualty Reinsurance 39,543 274,582 126,583 204,568 38,838 129,749 64,596 69,716 135,734 Corporate and Other — — — — 4,700 — — 26,903 — Total $ 54,450 $ 1,661,459 $ 386,473 $ 815,398 $ 61,256 $ 600,276 $ 111,103 $ 201,035 $ 762,672 December 31, 2017 Excess and Surplus Lines $ 17,050 $ 759,043 $ 149,047 $ 463,521 $ 15,014 $ 371,717 $ 45,158 $ 79,136 $ 469,891 Specialty Admitted (725 ) 271,446 73,649 68,110 2,532 44,863 5,605 20,081 60,957 Casualty Reinsurance 56,040 261,860 195,418 209,478 31,507 138,797 65,238 72,446 235,778 Corporate and Other — — — — 12,066 — — 25,330 — Total $ 72,365 $ 1,292,349 $ 418,114 $ 741,109 $ 61,119 $ 555,377 $ 116,001 $ 196,993 $ 766,626

SCHEDULE IV - Reinsurance

SCHEDULE IV - Reinsurance	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
Reinsurance	Reinsurance ​ Direct Amount Ceded to Other Companies Assumed from Other Companies Net Amount Percentage of Amount Assumed to Net ​ (in thousands) Year Ended December 31, 2019 ​ ​ ​ ​ ​ Excess and Surplus Lines Written Premiums $ 922,320 $ 236,506 $ — $ 685,814 — Specialty Admitted Written Premiums 383,628 329,005 4,014 58,637 6.8 % Casualty Reinsurance Written Premiums — 9,074 160,773 151,699 106.0 % Total Written Premiums $ 1,305,948 $ 574,585 $ 164,787 $ 896,150 18.4 % Year Ended December 31, 2018 ​ ​ ​ ​ Excess and Surplus Lines Written Premiums $ 656,538 $ 85,440 $ — $ 571,098 — Specialty Admitted Written Premiums 370,684 318,506 3,662 55,840 6.6 % Casualty Reinsurance Written Premiums — 155 135,889 135,734 100.1 % Total Written Premiums $ 1,027,222 $ 404,101 $ 139,551 $ 762,672 18.3 % Year Ended December 31, 2017 ​ ​ ​ ​ Excess and Surplus Lines Written Premiums $ 530,077 $ 60,229 $ 43 $ 469,891 — Specialty Admitted Written Premiums 313,642 255,473 2,788 60,957 4.6 % Casualty Reinsurance Written Premiums — (423 ) 235,355 235,778 99.8 % Total Written Premiums $ 843,719 $ 315,279 $ 238,186 $ 766,626 31.1 %

SCHEDULE V - Valuation and Qual

SCHEDULE V - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	Valuation and Qualifying Accounts ​ Balance at Beginning of Period Additions Amounts Charged to Expense Deductions Amounts Written Off or Disposals Balance at End of Period ​ (in thousands) Year Ended December 31, 2019 ​ ​ ​ ​ Allowance for Doubtful Accounts $ 3,948 $ 2,523 $ (812 ) $ 5,659 Allowance for Credit Losses on Bank Loans — 8,898 (1,717 ) 7,181 Total $ 3,948 $ 11,421 $ (2,529 ) $ 12,840 Year Ended December 31, 2018 ​ ​ ​ ​ Allowance for Doubtful Accounts $ 2,757 $ 1,504 $ (313 ) $ 3,948 Allowance for Credit Losses on Bank Loans 3,219 950 (4,169 ) — Total $ 5,976 $ 2,454 $ (4,482 ) $ 3,948 Year Ended December 31, 2017 ​ ​ ​ ​ Allowance for Doubtful Accounts $ 2,136 $ 1,029 $ (408 ) $ 2,757 Allowance for Credit Losses on Bank Loans 943 2,424 (148 ) 3,219 Total $ 3,079 $ 3,453 $ (556 ) $ 5,976

SCHEDULE VI - Supplementary Inf

SCHEDULE VI - Supplementary Information Concerning Property Casualty Insurance Operations	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Supplementary Information Concerning Property Casualty Insurance Operations	Supplementary Information Concerning Property Casualty Insurance Operations ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Deferred policy acquisition costs $ 62,006 $ 54,450 $ 72,365 Reserve for losses and loss adjustment expenses 2,045,506 1,661,459 1,292,349 Unearned premiums 524,377 386,473 418,114 Net earned premiums 823,746 815,398 741,109 Net investment income 75,652 61,256 61,119 Losses and loss adjustment expenses incurred: Current year 603,094 582,604 533,905 Prior year 69,008 17,672 21,472 Total losses and loss adjustment expenses incurred 672,102 600,276 555,377 Amortization of policy acquisition costs 83,893 111,103 116,001 Paid losses and loss adjustment expenses, net of reinsurance 488,729 396,013 326,680 Net written premiums 896,150 762,672 766,626

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“GAAP”), which vary in some respects from statutory accounting practices (“SAP”) which are prescribed or permitted by the various state insurance departments in the U.S. or by insurance regulators in Bermuda. The accompanying consolidated financial statements include the accounts and operations of the Company and its subsidiaries. Intercompany transactions and balances have been eliminated.
Estimates and Assumptions	Estimates and Assumptions Preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying disclosures. Those estimates are inherently subject to change, and actual results may ultimately differ from those estimates.
Fixed Maturity and Equity Securities	Fixed Maturity and Equity Securities Fixed maturity securities classified as “available-for-sale” are carried at fair value, and unrealized gains and losses on such securities, net of any deferred taxes, are reported as a separate component of accumulated other comprehensive income. Fixed maturity securities purchased for short-term resale are classified as “trading” and are carried at fair value with unrealized gains and losses included in earnings as a component of net investment income. The Company does not have any securities classified as “held-to-maturity”. Fair value generally represents quoted market value prices for securities traded in the public marketplace or prices analytically determined using bid or closing prices for securities not traded in the public marketplace. Premiums and discounts on mortgage-backed securities and asset-backed securities are amortized or accrued using the constant yield method which considers anticipated prepayments at the date of purchase. To the extent that the estimated lives of such securities change as a result of changes in estimated prepayment rates, the adjustments are included in net investment income using the retrospective method. Realized investment gains or losses are determined on a specific identification basis. Interest income is recognized as earned, and dividend income is recognized on the ex-dividend date. The Company evaluates its available-for-sale fixed maturity securities regularly to determine whether there are declines in value that are other-than-temporary. The Company’s outside investment managers assist the Company in this evaluation. When the Company determines that a security has experienced an other-than-temporary impairment, the impairment loss is recognized as a realized investment loss. The factors that the Company considers in evaluating whether such an other-than-temporary impairment has occurred include the amount and percentage that fair value is below amortized cost and the length of time that fair value has been below amortized cost. In addition, the Company considers the credit quality rating of the security, with a special emphasis on securities downgraded below investment grade. Management does not intend to sell available-for-sale fixed maturity securities in an unrealized loss position, and it is not “more likely than not” that the Company will be required to sell these securities before a recovery in fair value to their amortized cost basis occurs. Effective January 1, 2018, with the adoption of ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , equity securities (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) are measured at fair value with changes in fair value recognized in net realized and unrealized gains or losses. Prior to the adoption of ASU 2016-01, changes in the fair value of equity securities were recognized net of taxes as a component of accumulated other comprehensive income.
Bank Loan Participations Held-for-Investment and Allowance for Credit Losses	Bank Loan Participations Held-for-Investment and Allowance for Credit Losses Bank loan participations held-for-investment are managed by a specialized outside investment manager and are generally stated at their outstanding unpaid principal balances net of unamortized premiums or discounts and net of any allowance for credit losses. Interest income is accrued on the unpaid principal balance. Discounts and premiums are amortized to income using the interest method. Generally, the accrual of interest on a bank loan participation is discontinued when the contractual payment of principal or interest has become 90 days past due or management has serious doubts about further collectability of principal or interest. A bank loan participation may remain on accrual status if it is in the process of collection and is either guaranteed or well secured. Interest received on nonaccrual loans generally is reported as investment income. There were no bank loans on nonaccrual status at December 31, 2019 or 2018 . Generally, bank loan participations are restored to accrual status when the obligation is brought current, has performed in accordance with the contractual terms for a reasonable period of time, and the ultimate collectability of the total contractual principal and interest is no longer in doubt. ​ The allowance for credit losses is maintained at a level believed adequate by management to absorb estimated probable credit losses. Management’s periodic evaluation of the adequacy of the allowance is based on consultations and advice of the Company’s specialized investment manager, known and inherent risks in the portfolio, adverse situations that may affect the borrower’s ability to repay, the estimated value of any underlying collateral, current economic conditions, and other relevant factors. When an observable market price for a loan is available, the Company has recorded an allowance equal to the difference between the fair value and the amortized cost of bank loans that it has determined to be impaired as a practical expedient for an estimate of probable future cash flows to be collected on those bank loans. If an observable market price for a loan is not available, the Company records an allowance equal to the difference between the present value of expected future cash flows discounted at the loan’s effective interest rate and the amortized cost of the loan. Bank loans are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote.
Other Invested Assets	Other Invested Assets Other invested assets at December 31, 2019 and 2018 include the Company’s interests in private debt and equity investments. The investments are primarily focused in renewable energy, limited partnerships, and bank holding companies. Equity interests in various limited liability companies (“LLCs”) and limited partnerships are accounted for under the equity method, as the Company has determined that the equity method best reflects its economic interest in the underlying equity investment.
Short-Term Investments	Short-Term Investments Short-term investments are carried at amortized cost, which approximates fair value. Short-term investments have maturities greater than three months but less than one year at the date of purchase.
Cash Equivalents and Restricted Cash Equivalents	Cash Equivalents The Company considers highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. Restricted Cash Equivalents The Company considers highly liquid investments with maturities of three months or less at the date of purchase that are segregated for a specific use to be restricted cash equivalents.
Direct Written Premiums	Direct Written Premiums Direct written premiums are earned on a pro rata basis over the terms of the policies, generally 12 months. The portion of premiums written applicable to the unexpired terms of the policies in force is recorded as unearned premiums. Policies are accounted for on an individual basis, with no aggregation by counterparty.
Assumed Reinsurance Premiums	Assumed Reinsurance Premiums Assumed reinsurance written premiums include amounts reported by brokers and ceding companies, supplemented by the Company’s own estimates of premiums when reports have not been received. Premiums on the Company’s excess of loss and pro rata reinsurance contracts are estimated when the business is underwritten. For excess of loss contracts, the deposit premium, as defined in the contract, is generally recorded as an estimate of premiums written at the inception date of the treaty. Estimates of premiums written under pro rata contracts are recorded in the period in which the underlying risks are expected to begin and are based on information provided by the brokers and the ceding companies. Reinsurance premium estimates are reviewed by management periodically. Any adjustment to these estimates is recorded in the period in which it becomes known. ​ Reinsurance premiums assumed are earned over the terms of the underlying policies or reinsurance contracts. Contracts and policies written on a “losses occurring” basis cover claims that may occur during the term of the contract or policy, which is typically 12 months. Accordingly, the premium is earned evenly over the term. Contracts which are written on a “risks attaching” basis cover claims which attach to the underlying insurance policies written during the terms of such contracts. Premiums earned on such contracts usually extend beyond the original term of the reinsurance contract, typically resulting in recognition of premiums earned over a 24-month period in proportion to the level of underlying exposure. Contracts are accounted for on an individual basis, with no aggregation by counterparty.
Premiums Receivable and Agents' Balances, Net	Premiums Receivable and Agents’ Balances, Net Premiums receivable and agents’ balances are carried at face value net of any allowance for doubtful accounts. The allowance for doubtful accounts represents an estimate of amounts considered uncollectible based on the Company’s assessment of the collectability of receivables that are past due. Receivables greater than 90 days past due were $3.3 million and $4.5 million at December 31, 2019 and 2018 , respectively. The allowance for doubtful accounts was $5.7 million and $3.9 million at December 31, 2019 and 2018 , respectively. Bad debt expense was $2.5 million for the year ended December 31, 2019 , $1.5 million for the year ended December 31, 2018 , and $1.0 million for the year ended December 31, 2017 . Receivables written off against the allowance for doubtful accounts totaled $812,000 for the year ended December 31, 2019 , $313,000 for the year ended December 31, 2018 , and $408,000 for the year ended December 31, 2017 . Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote.
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs Costs which are incrementally or directly related to the successful acquisition of new or renewal insurance business are deferred. These deferred costs are primarily commissions to agents, ceding commissions paid on reinsurance assumed, premium taxes, and the portion of underwriting fixed compensation and payroll related fringe benefits directly related to an insurance contract that has been acquired, net of ceding commissions related to reinsurance ceded. Amortization of such policy acquisition costs is charged to expense in proportion to premium earned over the estimated policy life. To the extent that unearned premiums on existing policies are not adequate to cover projected related costs and expenses, deferred policy acquisition costs are charged to earnings. The Company considers anticipated investment income in determining whether a premium deficiency exists.
Reinsurance and Adjustable Features of Insurance and Reinsurance Contracts	Reinsurance and Adjustable Features of Insurance and Reinsurance Contracts Certain premiums and losses are ceded to other insurance companies or assumed from other insurance companies under various excess of loss and quota-share reinsurance contracts. The Company enters into ceded reinsurance contracts to limit its exposure to large losses, to limit exposure on new lines of insurance written by the Company, and to provide additional capacity for growth. Premiums, commissions, and losses and loss adjustment expenses on reinsured business are accounted for on a basis consistent with that used in accounting for the original policies issued and the terms of the reinsurance contracts. Reinsurance recoverables and prepaid reinsurance premiums are reported as assets. Other amounts payable to insurance companies and reinsurers or receivable from insurance companies and reinsurers are netted where the right of offset exists. The Company receives ceding commissions in connection with certain ceded reinsurance. The ceding commissions are recorded as a reduction of other operating expenses. Certain reinsurance contracts include provisions that adjust premiums or acquisition expenses based upon the loss experience under the contracts. Premiums written and earned, as well as related acquisition expenses are recorded based upon the projected loss experience under the contracts. The Company’s Specialty Admitted Insurance segment writes insurance under specialty admitted fronting and program arrangements. The fronting and program arrangements may contain contractual provisions that adjust acquisition expenses based upon loss experience under the contracts. The specialty admitted fronting and program arrangements are significantly reinsured. These reinsurance contracts may also contain provisions that adjust premiums or acquisition expenses based upon the loss experience under the contracts. Premiums written and earned, as well as related acquisition expenses, are recorded based upon the projected experience under the contracts.
Other Income	Other Income Other income is principally comprised of fee income earned on policies for which the Company has no exposure to underwriting risk. Fee income of $9.1 million , $13.9 million , and $17.0 million is included in other income for the years ended December 31, 2019 , 2018 , and 2017 , respectively. Fees are earned on a pro rata basis over the service period of the underlying business. Policies are accounted for on an individual basis, with no aggregation by counterparty.
Income Taxes	Income Taxes Deferred tax assets and deferred tax liabilities are provided for the future tax consequences attributable to temporary differences between the financial statement carrying amounts of assets and liabilities and their respective U.S. tax basis. Deferred tax assets and liabilities are measured using enacted U.S. corporate tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Deferred tax assets are reduced by a valuation allowance only when management believes it is more likely than not that some, or all, of the deferred tax assets will not be realized. Effective January 1, 2018, the Company adopted ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.
Goodwill	Goodwill Goodwill is tested annually for impairment in the fourth quarter of each calendar year, or more frequently if events or changes in circumstances indicate that the carrying amount of the Company’s reporting units, including goodwill, may exceed their fair values. The Company first assesses qualitative factors in determining whether it is necessary to perform the quantitative goodwill impairment test. If management determines that it is more likely than not that the fair value of a reporting unit is less than the carrying value based on qualitative factors then they will perform the quantitative goodwill impairment test. For the quantitative goodwill impairment testing, the fair value of the reporting units is determined using a combination of a market approach and an income approach which projects the future cash flows produced by the reporting units and discounts those cash flows to their present value. The projection of future cash flows is necessarily dependent upon assumptions on the future levels of income as well as business trends, prospects, market, and economic conditions. The results of the two approaches are weighted to determine the fair value of each reporting unit. When the fair value is less than the carrying value of the net assets of the reporting unit, including goodwill, an impairment loss is charged to operations. To determine the amount of any goodwill impairment, the implied fair value of reporting unit goodwill is compared to the carrying amount of that goodwill. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination is determined. That is, the fair value of a reporting unit is assigned to all of the assets and liabilities of that unit (including any unrecognized intangible assets) as if the reporting unit had been acquired in a business combination. The excess of the fair value of a reporting unit over the amounts assigned to its assets and liabilities is the implied fair value of goodwill.
Intangible Assets, Net	Intangible Assets, Net Intangible assets are initially recognized and measured at fair value. Specifically identified intangible assets with indefinite lives include trademarks and state insurance licenses and authorities. Other specifically identified intangible assets with lives ranging from 7.0 to 27.5 years represent relationships with brokers. These intangible assets are amortized on a straight-line basis over their estimated useful lives. Intangible assets with indefinite useful lives are reviewed for impairment at least annually. In evaluating whether there has been impairment to the intangible asset, management determines the fair value of the intangible asset and compares the resulting fair value to the carrying value of the intangible asset. If the carrying value exceeds the fair value, the intangible asset is written down to fair value, and the impairment is reported through earnings. The Company evaluates intangible assets with definite lives for impairment when impairment indicators are noted.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets with finite lives are tested for impairment whenever recognized events or changes in circumstances indicate the carrying value of these assets may not be recoverable. If indicators of impairment are present, fair value is calculated using estimated future cash flows expected to be generated from the use of those assets. An impairment loss is recognized only if the carrying amount of a long-lived asset or asset group is not recoverable and exceeds its fair value. The carrying amount of a long-lived asset or asset group is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset or asset group. That assessment is based on the carrying amount of the asset or asset group at the date it is tested for recoverability. An impairment loss is measured as the amount by which the carrying amount of a long-lived asset or asset group exceeds its fair value.
Property and Equipment, Net	Property and Equipment, Net Property and equipment, which is included in “other assets” in the accompanying consolidated balance sheets, is reported at cost less accumulated depreciation and is depreciated principally on a straight-line basis over the estimated useful lives of the depreciable assets, generally three to ten years .
Reserve for Losses and Loss Adjustment Expenses	Reserve for Losses and Loss Adjustment Expenses The reserve for losses and loss adjustment expenses represents the estimated ultimate cost of all reported and unreported losses and loss adjustment expenses incurred and unpaid at the balance sheet date. The Company does not discount this reserve. The process of estimating the reserve for losses and loss adjustment expenses requires a high degree of judgment and is subject to a number of variables. The reserve for losses and loss adjustment expenses is estimated using individual case-basis valuations and statistical analyses. Those estimates are subject to the effects of trends in loss severity and frequency. The Company utilizes various actuarially-accepted reserving methodologies in determining the continuum of expected outcomes for its reserves. These methodologies utilize various inputs, including management’s initial expected loss ratio (the ratio of losses and loss adjustment expenses incurred to net earned premiums), expected reporting patterns and payment patterns for losses and loss adjustment expenses (based on insurance industry data and the Company’s own experience), and the Company’s actual paid and reported losses and loss adjustment expenses. An internal actuary reviews these results and (after applying appropriate professional judgment and other actuarial techniques that are considered necessary) presents recommendations to the Company’s management. Management uses this information and its judgment to make decisions on the final recorded reserve for losses and loss adjustment expenses. Management believes that the use of judgment is necessary to arrive at a best estimate for the reserve for losses and loss adjustment expenses given the long-tailed nature of the business generally written by the Company and the limited operating experience of the Casualty Reinsurance segment, the fronting and program business in the Specialty Admitted Insurance segment, and the commercial auto business in the Excess and Surplus Lines segment. Catastrophes of significant magnitude, including hurricanes and earthquakes, involve complex coverage issues. In estimating the reserve for losses and loss adjustment expenses for these catastrophes, management uses case reserve estimates based on information obtained from site inspections by the Company’s adjustors and the terms of coverage provided in the policies. Management estimates reserves for incurred but not reported claims for these catastrophes using judgment based on an assessment of the Company’s property insurance exposures where the catastrophes occur and the Company’s progress in settling claims. Although management believes that the reserve for losses and loss adjustment expenses is reasonable, it is possible that the Company’s actual incurred losses and loss adjustment expenses will not develop in a manner consistent with the assumptions inherent in the determination of these reserves. Specifically, the Company’s actual ultimate loss ratio could differ from management’s initial expected loss ratio and/or the Company’s actual reporting patterns for losses could differ from the expected reporting patterns. Accordingly, the ultimate settlement of losses and the related loss adjustment expenses may vary significantly from the estimates included in the Company’s consolidated financial statements. These estimates are reviewed continually by management and are adjusted as necessary as experience develops or new information becomes known; such adjustments are included in current operations.
Share Based Compensation	Share Based Compensation The Company expenses the fair value of share equity awards over the vesting period of the award on a straight-line basis. The Black-Scholes-Merton option pricing model is used to value the options granted (see Note 12). Forfeitures of share-based awards are recognized as they occur. As the share based compensation expense is incurred, a corresponding increase to additional paid-in capital in shareholders’ equity is recognized. Share based compensation expense is reflected in “other operating expenses” in the accompanying consolidated statements of income and comprehensive income.
Variable Interest Entities	Variable Interest Entities Entities that do not have sufficient equity at risk to allow the entity to finance its activities without additional financial support or in which the equity investors, as a group, do not have the characteristic of a controlling financial interest are referred to as variable interest entities (“VIE”). A VIE is consolidated by the variable interest holder that is determined to have the controlling financial interest (primary beneficiary) as a result of having both the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance and the obligation to absorb losses or right to receive benefits from the VIE that could potentially be significant to the VIE. The Company determines whether it is the primary beneficiary of an entity subject to consolidation based on a qualitative assessment of the VIE’s capital structure, contractual terms, nature of the VIE’s operations and purpose, and the Company’s relative exposure to the related risks of the VIE on the date it becomes initially involved in the VIE. The Company reassesses its VIE determination with respect to an entity on an ongoing basis.
Earnings Per Share	Earnings Per Share Basic earnings per share excludes dilution and is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted earnings per share reflects the dilution that could occur if securities or other contracts to issue common shares or common share equivalents were exercised or converted into common shares as calculated using the treasury stock method. When inclusion of common share equivalents increases the earnings per share or reduces the loss per share, the effect on earnings is anti-dilutive, and the diluted net earnings or net loss per share is computed excluding these common share equivalents.
Adopted and Prospective Accounting Standards	Adopted Accounting Standards Effective January 1, 2019, the Company adopted ASU 2016-02, Leases (Topic 842) . This update requires the recognition of a right-of-use asset and a corresponding lease liability, discounted to the present value, for all leases that extend beyond 12 months. The Company adopted the new standard using a modified retrospective transition method, applying the transition provisions at the beginning of the period of adoption. The Company elected the package of practical expedients permitted under the transition guidance within the new standard and did not elect to use hindsight in determining the lease term. Upon adoption of the new standard, the Company derecognized assets of $22.6 million and liabilities of $30.9 million associated with a lease that was designated as build-to-suit under the previous guidance, and recorded a cumulative-effect adjustment to increase retained earnings by $8.3 million . The Company recorded right-of-use assets of $17.2 million and lease liabilities of $17.8 million at adoption of the new standard associated with operating leases for office space in Bermuda, North Carolina, Virginia, Arizona, and Georgia. The new standard did not materially impact the Company's results of operations, earnings per share, or cash flows, and did not impact compliance under the covenants of the Company's current credit agreements. Prospective Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Current GAAP requires the recognition of credit losses when it is probable a loss has been incurred. The update will require financial assets measured at amortized cost, such as bank loan participations held for investment, to be presented at the net amount expected to be collected by means of an allowance for credit losses that is reflected in net income. Credit losses relating to available-for-sale debt securities will also be recorded through an allowance for credit losses, with the amount of the allowance limited to the amount by which fair value is below amortized cost. This ASU is effective for annual and interim reporting periods beginning after December 15, 2019. The Company will adopt the ASU on January 1, 2020 using the modified-retrospective approach, by which a cumulative-effect adjustment will be made to retained earnings as of the date of adoption. In connection with the adoption of this ASU, the Company will elect the fair value option in accounting for bank loan participations effective January 1, 2020. We will also use the targeted transition relief offered by ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief to elect the fair value option to account for bank loan participations already held at the January 1, 2020 date of adoption. Under the fair value option, bank loan participations will be measured at fair value, and changes in unrealized gains and losses in bank loan participations will be reported in our income statement as net realized and unrealized gains (losses) on investments. At adoption on January 1, 2020, the Company expects to reduce the carrying value of its bank loan portfolio to fair value through an $8.4 million adjustment with a $7.8 million (net of tax) cumulative effect adjustment to reduce retained earnings. Upon adoption of this ASU, the Company will establish an allowance for uncollectible reinsurance balances through a cumulative effect adjustment to retained earnings. Because we purchase reinsurance from financially strong reinsurers or we have collateral securing the recoverables, the effect of adoption is not expected to be material to our financial position.
Leases	Operating lease costs are primarily comprised of rental expense for operating leases. Rental expense is recognized on a straight line basis over the lease term and includes amortization of the right-of-use lease asset and imputed interest on the lease liability. Operating lease costs are included in other operating expenses in the Company's consolidated statements of income and comprehensive income.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedule of reconciliation of numerator and denominator of basic and diluted earnings per share	The following represents a reconciliation of the numerator and denominator of the basic and diluted earnings per share computations contained in the consolidated financial statements. ​ Net Income Weighted-Average Earnings ​ (in thousands, except per share data) Year ended December 31, 2019 ​ ​ ​ Basic $ 38,339 30,275,184 $ 1.27 Common share equivalents — 398,740 (0.02 ) Diluted $ 38,339 30,673,924 $ 1.25 Year ended December 31, 2018 Basic $ 63,830 29,887,990 $ 2.14 Common share equivalents — 419,111 (0.03 ) Diluted $ 63,830 30,307,101 $ 2.11 Year ended December 31, 2017 Basic $ 43,566 29,461,717 $ 1.48 Common share equivalents — 811,432 (0.04 ) Diluted $ 43,566 30,273,149 $ 1.44

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of summary of available-for-sale investments	The Company’s available-for-sale fixed maturity securities are summarized as follows: Cost or Gross Gross Fair (in thousands) December 31, 2019 Fixed maturity securities: State and municipal $ 159,894 $ 7,949 $ (742 ) $ 167,101 Residential mortgage-backed 261,524 3,244 (622 ) 264,146 Corporate 611,304 21,306 (389 ) 632,221 Commercial mortgage and asset-backed 249,309 3,954 (806 ) 252,457 U.S. Treasury securities and obligations guaranteed by the U.S. government 114,477 1,229 (39 ) 115,667 Redeemable preferred stock 2,025 9 — 2,034 Total fixed maturity securities, available-for-sale $ 1,398,533 $ 37,691 $ (2,598 ) $ 1,433,626 December 31, 2018 Fixed maturity securities: State and municipal $ 147,160 $ 3,422 $ (1,287 ) $ 149,295 Residential mortgage-backed 208,869 577 (5,337 ) 204,109 Corporate 534,024 1,516 (10,772 ) 524,768 Commercial mortgage and asset-backed 199,528 310 (2,813 ) 197,025 U.S. Treasury securities and obligations guaranteed by the U.S. government 107,803 235 (845 ) 107,193 Redeemable preferred stock 2,025 — (213 ) 1,812 Total fixed maturity securities, available-for-sale $ 1,199,409 $ 6,060 $ (21,267 ) $ 1,184,202
Schedule of summary of available-for-sale investments by contractual maturity	The amortized cost and fair value of available-for-sale investments in fixed maturity securities at December 31, 2019 are summarized, by contractual maturity, as follows: Cost or Fair (in thousands) One year or less $ 81,705 $ 82,048 After one year through five years 456,076 466,952 After five years through ten years 219,717 228,596 After ten years 128,177 137,393 Residential mortgage-backed 261,524 264,146 Commercial mortgage and asset-backed 249,309 252,457 Redeemable preferred stock 2,025 2,034 Total $ 1,398,533 $ 1,433,626
Schedule of gross unrealized losses and fair value for available-for-sale securities	The following table shows the Company’s gross unrealized losses and fair value for available-for-sale securities aggregated by investment category and the length of time that individual securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total Fair Gross Fair Gross Fair Gross (in thousands) December 31, 2019 Fixed maturity securities: State and municipal $ 30,028 $ (741 ) $ 667 $ (1 ) $ 30,695 $ (742 ) Residential mortgage-backed 23,632 (78 ) 37,363 (544 ) 60,995 (622 ) Corporate 45,550 (365 ) 9,933 (24 ) 55,483 (389 ) Commercial mortgage and asset-backed 46,434 (406 ) 56,720 (400 ) 103,154 (806 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 8,474 (22 ) 7,168 (17 ) 15,642 (39 ) Total fixed maturity securities, available-for-sale $ 154,118 $ (1,612 ) $ 111,851 $ (986 ) $ 265,969 $ (2,598 ) December 31, 2018 Fixed maturity securities: State and municipal $ 19,733 $ (284 ) $ 47,018 $ (1,003 ) $ 66,751 $ (1,287 ) Residential mortgage-backed 49,180 (743 ) 105,778 (4,594 ) 154,958 (5,337 ) Corporate 243,384 (5,089 ) 155,902 (5,683 ) 399,286 (10,772 ) Commercial mortgage and asset-backed 106,423 (1,229 ) 51,805 (1,584 ) 158,228 (2,813 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 17,618 (51 ) 54,201 (794 ) 71,819 (845 ) Redeemable preferred stock 1,812 (213 ) — — 1,812 (213 ) Total fixed maturity securities, available-for-sale $ 438,150 $ (7,609 ) $ 414,704 $ (13,658 ) $ 852,854 $ (21,267 )
Schedule of major categories of the company' s net investment income	Major categories of the Company’s net investment income are summarized as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Fixed maturity securities $ 39,875 $ 34,129 $ 26,833 Bank loan participations 19,772 18,279 17,388 Equity securities 5,262 5,240 5,045 Other invested assets 6,254 5,165 14,079 Cash, cash equivalents, restricted cash equivalents, and short-term investments 9,210 2,677 1,704 Gross investment income 80,373 65,490 65,049 Investment expense (4,721 ) (4,234 ) (3,930 ) Net investment income $ 75,652 $ 61,256 $ 61,119
Schedule of summary of realized gains and losses	The Company’s net realized and unrealized losses and gains on investments are summarized as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Fixed maturity securities: Gross realized gains $ 1,575 $ 422 $ 840 Gross realized losses (494 ) (976 ) (512 ) ​ 1,081 (554 ) 328 Equity securities: Gross realized gains 11 — 429 Gross realized losses (232 ) (62 ) (1,591 ) Changes in fair values of equity securities 6,257 (5,970 ) — ​ 6,036 (6,032 ) (1,162 ) Bank loan participations: Gross realized gains 846 2,279 2,407 Gross realized losses (10,902 ) (1,166 ) (3,557 ) ​ (10,056 ) 1,113 (1,150 ) Short-term investments and other: Gross realized gains 21 — 1 Gross realized losses (1 ) (6 ) (6 ) ​ 20 (6 ) (5 ) Total $ (2,919 ) $ (5,479 ) $ (1,989 )
Schedule of available-for-sale gross unrealized gains or losses	The following table summarizes the change in the Company’s available-for-sale gross unrealized gains or losses by investment type: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Change in gross unrealized gains (losses): Fixed maturity securities $ 50,300 $ (22,643 ) $ 6,571 Equity securities — — 5,356 Total $ 50,300 $ (22,643 ) $ 11,927
Schedule of other invested assets	The Company invests selectively in private debt and equity opportunities. These investments, which together comprise the Company’s other invested assets, are primarily focused in renewable energy, limited partnerships, and bank holding companies. ​ Carrying Value Investment Income ​ December 31, Year Ended December 31, ​ 2019 2018 2019 2018 2017 ​ (in thousands) (in thousands) Renewable energy LLCs (a) $ 31,219 $ 29,795 $ 2,181 $ 2,974 $ 10,578 Renewable energy notes receivable (b) 8,750 8,750 1,313 1,282 526 Limited partnerships (c) 16,741 29,276 2,417 566 2,632 Bank holding companies (d) 4,500 4,500 343 343 343 Total other invested assets $ 61,210 $ 72,321 $ 6,254 $ 5,165 $ 14,079 (a) The Company’s Corporate and Other segment owns equity interests ranging from 2.6% to 32.2% in various LLCs whose principal objective is capital appreciation and income generation from owning and operating renewable energy production facilities (wind and solar). The LLCs are managed by an entity for which one of our directors and one of our recent former directors serve as officers, and the Company’s Executive Chairman and Chief Executive Officer has invested in certain of these LLCs. The equity method is used to account for the Company’s LLC investments. Income for the LLCs primarily reflects adjustments to the carrying values of investments in renewable energy projects to their determined fair values. The fair value adjustments are included in revenues for the LLCs. Expenses for the LLCs are not significant and are comprised of administrative and interest expenses. The Company received cash distributions from these investments totaling $757,000 and $5.8 million for the years ended December 31, 2019 and 2018 , respectively. ​ (b) The Company's Corporate and Other segment has invested in notes receivable for renewable energy projects. At December 31, 2019 and 2018 , the Company held one $8.8 million note issued by an entity for which one of our directors and one of our recent former directors serve as officers . Interest on the note, which matures in 2021, is fixed at 15% . Interest income on the note was $1.3 million , $1.3 million , and $526,000 for the years ended December 31, 2019 , 2018 , and 2017 , respectively. ​ (c) The Company owns investments in limited partnerships that invest in concentrated portfolios including publicly-traded small cap equities, loans of middle market private equity sponsored companies, equity tranches of collateralized loan obligations ("CLOs"), and tranches of distressed home loans. Income from the partnerships is recognized under the equity method of accounting. The Company’s Corporate and Other segment held an investment in a limited partnership with a carrying value of $3.4 million and $3.1 million at December 31, 2019 and 2018 , and recognized investment income of $327,000 , $70,000 , and $394,000 for the years ended December 31, 2019 , 2018 and 2017 , respectively. The Company’s Excess and Surplus Lines segment holds investments in limited partnerships of $13.3 million and $26.2 million at December 31, 2019 and 2018 , respectively. Investment income of $2.1 million , $496,000 , and $2.2 million were recognized on these investments for the years ended December 31, 2019 , 2018 , and 2017 , respectively. At December 31, 2019 , the Company’s Excess and Surplus Lines segment has outstanding commitments to invest another $625,000 in these limited partnerships. (d) The Company's Corporate and Other segment holds $4.5 million of subordinated notes issued by a bank holding company for which the Company’s Executive Chairman and Chief Executive Officer was previously the Lead Independent Director and an investor and for which one of the Company’s directors was an investor and is currently a lender (the "Bank Holding Company"). Interest on the notes, which mature in 2023, is fixed at 7.6% per annum. Interest income on the notes was $343,000 in each of the years ended December 31, 2019 , 2018 and 2017 .

Deferred Policy Acquisition C_2

Deferred Policy Acquisition Costs (Tables)	12 Months Ended
	Dec. 31, 2019
Deferred Policy Acquisition Costs Disclosures [Abstract]
Schedule of deferred policy acquisition costs	​ An analysis of deferred policy acquisition costs is as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Balance at beginning of period $ 54,450 $ 72,365 $ 64,789 Policy acquisition costs deferred: Commissions 67,303 72,473 107,387 Underwriting and other issue expenses 24,146 20,715 16,190 ​ 91,449 93,188 123,577 Amortization of policy acquisition costs (83,893 ) (111,103 ) (116,001 ) Net change 7,556 (17,915 ) 7,576 Balance at end of period $ 62,006 $ 54,450 $ 72,365

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of gross carrying amounts and accumulated amortization	The gross carrying amounts and accumulated amortization for each major specifically identifiable intangible asset class were as follows: ​ December 31, ​ 2019 2018 Weighted- Average Life (Years) Gross Accumulated Gross Accumulated ​ ​ (in thousands) Trademarks Indefinite $ 22,200 $ — $ 22,200 $ — Insurance licenses and authorities Indefinite 8,964 — 8,964 — Identifiable intangibles not subject to amortization ​ 31,164 — 31,164 — Broker relationships 24.6 11,611 5,835 11,611 5,238 Identifiable intangible assets subject to amortization ​ 11,611 5,835 11,611 5,238 ​ ​ $ 42,775 $ 5,835 $ 42,775 $ 5,238
Schedule of future estimated amortization	Future estimated amortization of specifically identifiable intangible assets as of December 31, 2019 is as follows ( in thousands) : 2020 $ 538 2021 363 2022 363 2023 363 2024 363 Thereafter 3,786 Total $ 5,776
Schedule of acquired indefinite-lived intangible assets	The table below summarizes the changes in the net carrying values of intangible assets by segment for 2019 : December 31, 2018 December 31, 2019 ​ Net Carrying Amortization Impairment Net Carrying ​ (in thousands) Excess and Surplus Lines Trademarks $ 19,700 $ — $ — $ 19,700 Insurance licenses and authorities 4,900 — — 4,900 Broker relationships 5,965 (362 ) — 5,603 ​ 30,565 (362 ) — 30,203 Specialty Admitted Insurance Trademarks 2,500 — — 2,500 Insurance licenses and authorities 4,065 — — 4,065 Broker relationships 407 (235 ) — 172 ​ 6,972 (235 ) — 6,737 Total identifiable intangible assets $ 37,537 $ (597 ) $ — $ 36,940   ​ The table below summarizes the changes in the net carrying values of intangible assets by segment for 2018 : December 31, 2017 December 31, 2018 ​ Net Carrying Amortization Impairment Net Carrying ​ (in thousands) Excess and Surplus Lines Trademarks $ 19,700 $ — $ — $ 19,700 Insurance licenses and authorities 4,900 — — 4,900 Broker relationships 6,327 (362 ) — 5,965 ​ 30,927 (362 ) — 30,565 Specialty Admitted Insurance Trademarks 2,500 — — 2,500 Insurance licenses and authorities 4,265 — (200 ) 4,065 Broker relationships 642 (235 ) — 407 ​ 7,407 (235 ) (200 ) 6,972 Total identifiable intangible assets $ 38,334 $ (597 ) $ (200 ) $ 37,537
Schedule of acquired finite-lived intangible assets	The table below summarizes the changes in the net carrying values of intangible assets by segment for 2019 : December 31, 2018 December 31, 2019 ​ Net Carrying Amortization Impairment Net Carrying ​ (in thousands) Excess and Surplus Lines Trademarks $ 19,700 $ — $ — $ 19,700 Insurance licenses and authorities 4,900 — — 4,900 Broker relationships 5,965 (362 ) — 5,603 ​ 30,565 (362 ) — 30,203 Specialty Admitted Insurance Trademarks 2,500 — — 2,500 Insurance licenses and authorities 4,065 — — 4,065 Broker relationships 407 (235 ) — 172 ​ 6,972 (235 ) — 6,737 Total identifiable intangible assets $ 37,537 $ (597 ) $ — $ 36,940   ​ The table below summarizes the changes in the net carrying values of intangible assets by segment for 2018 : December 31, 2017 December 31, 2018 ​ Net Carrying Amortization Impairment Net Carrying ​ (in thousands) Excess and Surplus Lines Trademarks $ 19,700 $ — $ — $ 19,700 Insurance licenses and authorities 4,900 — — 4,900 Broker relationships 6,327 (362 ) — 5,965 ​ 30,927 (362 ) — 30,565 Specialty Admitted Insurance Trademarks 2,500 — — 2,500 Insurance licenses and authorities 4,265 — (200 ) 4,065 Broker relationships 642 (235 ) — 407 ​ 7,407 (235 ) (200 ) 6,972 Total identifiable intangible assets $ 38,334 $ (597 ) $ (200 ) $ 37,537

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of property and equipment, net	Property and equipment, net of accumulated depreciation, is included in "other assets" on the consolidated balance sheets and consists of the following: ​ December 31, ​ 2019 2018 ​ (in thousands) Building, leased for which the Company was previously deemed the owner for accounting purposes $ — $ 30,971 Electronic data processing hardware and software 7,522 7,423 Furniture and equipment 2,180 2,662 Property and equipment, cost basis 9,702 41,056 Accumulated depreciation (7,934 ) (17,745 ) Property and equipment, net $ 1,768 $ 23,311

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Summary of Lease Maturities	he table below summarizes maturities of the Company’s operating lease liabilities as of December 31, 2019 , which reconciles to total lease liabilities included in other liabilities on the Company’s consolidated balance sheet: Years ending December 31, (in thousands) 2020 $ 4,024 2021 3,993 2022 3,800 2023 3,619 2024 2,422 Thereafter 2,546 Total lease payments 20,404 Less imputed interest (2,172 ) Total operating lease liabilities $ 18,232

Reserve for Losses and Loss A_2

Reserve for Losses and Loss Adjustment Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Liability for Claims and Claims Adjustment Expense [Abstract]
Schedule of reconciliation of beginning and ending reserve balances for losses and loss adjustment expenses	The following table provides a reconciliation of the beginning and ending reserve balances for losses and loss adjustment expenses, net of reinsurance, to the gross amounts reported in the consolidated balance sheets: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Reserve for losses and loss adjustment expenses net of reinsurance recoverables at beginning of period $ 1,194,088 $ 989,825 $ 761,128 Add: Incurred losses and loss adjustment expenses net of reinsurance: ​ ​ ​ Current year 603,094 582,604 533,905 Prior years 69,008 17,672 21,472 Total incurred losses and loss and adjustment expenses 672,102 600,276 555,377 Deduct: Loss and loss adjustment expense payments net of reinsurance: ​ ​ ​ Current year 75,249 86,355 103,205 Prior years 413,480 309,658 223,475 Total loss and loss adjustment expense payments 488,729 396,013 326,680 Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period 1,377,461 1,194,088 989,825 Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period 668,045 467,371 302,524 Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period $ 2,045,506 $ 1,661,459 $ 1,292,349
Schedule of incurred losses and loss adjustment expenses, net of reinsurance	Excess and Surplus Lines — Excluding Commercial Auto Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 78,424 $ 80,569 $ 78,117 $ 73,035 $ 69,080 $ 69,964 $ 70,294 $ 70,913 $ 71,312 $ 69,594 2011 111,190 119,927 114,473 106,564 106,381 106,130 106,643 106,536 105,173 2012 97,908 98,672 97,829 96,497 97,306 99,619 101,271 103,061 2013 96,729 96,064 85,433 81,009 82,830 83,855 82,732 2014 114,942 104,092 90,267 82,232 84,074 88,904 2015 126,443 113,417 104,847 102,434 103,688 2016 138,507 125,093 126,050 126,971 2017 144,349 131,897 132,136 2018 167,004 158,458 2019 214,653 Total $ 1,185,370   Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 13,673 $ 26,418 $ 35,812 $ 45,641 $ 52,071 $ 57,371 $ 61,307 $ 64,214 $ 65,246 $ 65,915 2011 27,684 53,109 72,732 81,696 90,884 94,998 98,684 99,798 101,728 2012 6,944 33,757 49,604 63,216 74,869 82,545 88,812 94,588 2013 3,867 14,509 30,382 44,421 59,641 66,553 71,035 2014 3,412 16,969 28,212 43,891 58,774 71,549 2015 4,048 17,164 34,801 55,911 73,455 2016 5,180 22,852 46,045 70,105 2017 5,290 22,956 42,764 2018 6,000 26,160 2019 8,235 Total $ 625,534 All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance (60 claims outstanding) $ 8,978 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 568,814 Excess and Surplus Lines — Commercial Auto Incurred losses and adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 1,255 $ 1,300 $ 1,451 $ 1,351 $ 1,301 $ 1,277 $ 1,277 2014 20,487 14,071 17,233 18,953 19,779 18,303 2015 30,109 33,113 35,149 36,139 36,636 2016 74,340 109,286 126,791 147,122 2017 207,355 208,743 272,421 2018 255,881 230,220 2019 262,306 Total $ 968,285 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 60 $ 1,182 $ 1,285 $ 1,291 $ 1,275 $ 1,275 $ 1,275 2014 6,166 8,645 12,679 16,359 18,678 17,745 2015 8,356 15,234 24,282 31,592 34,819 2016 18,295 54,054 89,381 125,108 2017 41,467 107,377 192,961 2018 45,136 119,099 2019 44,225 Total $ 535,232 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 433,053 Specialty Admitted — Individual Risk Workers’ Compensation Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 27,209 $ 28,736 $ 30,464 $ 30,373 $ 28,963 $ 28,938 $ 27,590 $ 27,098 $ 27,099 $ 27,099 2011 37,834 41,421 40,154 38,999 38,311 37,455 36,594 36,593 36,593 2012 32,116 32,420 31,490 29,689 28,255 28,174 28,186 28,186 2013 12,525 13,668 12,786 11,578 10,907 10,909 10,909 2014 16,638 16,652 14,620 13,890 12,704 12,704 2015 20,938 21,274 19,741 18,376 17,626 2016 21,678 20,299 18,050 15,800 2017 24,869 22,071 19,779 2018 16,432 16,288 2019 20,253 Total $ 205,237 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 7,157 $ 16,245 $ 21,805 $ 23,898 $ 25,210 $ 25,477 $ 26,345 $ 26,352 $ 26,358 $ 26,365 2011 10,123 23,127 29,021 33,204 34,240 34,287 34,334 34,614 34,638 2012 9,222 20,308 24,755 26,435 26,897 26,932 26,963 26,994 2013 4,487 8,723 9,846 10,246 10,263 10,309 10,337 2014 4,633 10,648 12,041 12,236 12,282 12,282 2015 6,604 13,285 15,118 15,889 15,901 2016 4,664 10,227 12,135 12,432 2017 6,546 12,782 14,285 2018 4,497 9,034 2019 5,473 Total $ 167,741 All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance (4 claims outstanding) $ 1,039 Outstanding losses and loss adjustment expenses assumed from involuntary workers’ compensation pools $ 4,656 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 43,191 Specialty Admitted — Fronting and Programs Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 104 $ 80 $ 52 $ 52 $ 52 $ 52 52 2014 3,460 3,468 3,818 3,425 3,228 3,083 2015 7,136 9,632 9,358 8,974 8,384 2016 11,542 15,670 14,682 15,522 2017 21,229 24,271 25,201 2018 21,758 20,677 2019 18,832 Total $ 91,751 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2013 2014 2015 2016 2017 2018 2019 2013 $ 28 $ 52 $ 52 $ 52 $ 52 $ 52 52 2014 883 1,687 2,369 2,728 2,854 2,916 2015 2,058 4,666 6,165 6,919 7,329 2016 1,894 5,123 6,888 10,732 2017 1,223 6,682 13,065 2018 885 4,972 2019 4,358 Total $ 43,424 All outstanding losses and loss adjustment expenses, net of reinsurance $ 48,327 Outstanding losses and loss adjustment expenses, assumed from involuntary pools $ 400 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 48,727 Casualty Reinsurance Incurred losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 64,413 $ 60,476 $ 61,068 $ 62,714 $ 61,344 $ 60,949 $ 60,978 $ 61,619 $ 62,605 $ 63,357 2011 114,908 103,123 97,366 97,812 98,993 99,282 101,276 103,196 105,333 2012 148,251 132,388 131,281 135,594 136,813 139,978 143,305 146,045 2013 133,230 130,361 131,352 134,446 137,801 143,124 146,760 2014 118,881 115,927 114,636 116,981 121,200 126,160 2015 119,157 108,870 108,699 109,117 114,517 2016 112,759 105,533 103,544 108,222 2017 134,628 128,472 129,800 2018 121,529 119,098 2019 86,022 Total $ 1,145,314 Cumulative paid losses and loss adjustment expenses, net of reinsurance (in thousands) Accident Year 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 21,918 $ 31,500 $ 38,430 $ 44,921 $ 49,263 $ 52,761 $ 54,659 $ 57,013 $ 58,707 $ 59,634 2011 48,688 61,922 68,616 78,164 87,267 90,287 94,627 97,715 99,511 2012 73,124 81,859 97,215 113,943 121,026 128,567 133,606 137,430 2013 59,756 75,094 93,902 108,396 119,256 127,732 134,644 2014 41,421 58,601 76,302 89,899 101,366 110,374 2015 40,021 53,986 68,002 80,208 90,661 2016 36,268 50,905 65,409 78,145 2017 47,739 72,891 90,117 2018 30,903 50,274 2019 12,646 Total $ 863,436 All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance $ 1,798 Total outstanding losses and loss adjustment expenses, net of reinsurance $ 283,676
Schedule of reserve for losses and loss adjustment expenses	The reconciliation of the net incurred and paid claims development tables to the reserve for losses and loss adjustment expenses in the consolidated balance sheet at December 31, 2019 is as follows (in thousands): E&S – excluding commercial auto $ 568,814 E&S – commercial auto 433,053 Specialty Admitted – individual risk workers’ compensation 43,191 Specialty Admitted – fronting and programs 48,727 Casualty Reinsurance 283,676 Net reserve for losses and loss adjustment expenses 1,377,461 Reinsurance recoverables on unpaid losses 668,045 Gross reserve for losses and loss adjustment expenses $ 2,045,506
Schedule of average annual percentage payouts of incurred claims by age, net of reinsurance	The following is unaudited supplementary information about average annual percentage payouts of incurred claims by age, net of reinsurance, for the Excess and Surplus Lines segment and the Specialty Admitted Insurance segments as of December 31, 2019 . ​ Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 E&S – excluding commercial auto 9.5 % 15.7 % 17.2 % 18.5 % 14.5 % 8.0 % 5.4 % 3.8 % 2.0 % 1.1 % E&S – commercial auto 20.4 % 38.1 % 16.0 % 14.1 % 7.2 % 2.6 % 1.5 % Specialty Admitted – individual risk workers’ compensation 27.9 % 30.9 % 16.0 % 10.2 % 7.2 % 1.2 % 1.7 % 0.9 % 0.1 % 1.3 % Specialty Admitted – fronting and programs 18.7 % 22.4 % 24.3 % 16.1 % 10.5 % 5.3 % Casualty Reinsurance 21.1 % 16.4 % 12.2 % 8.9 % 6.4 % 5.3 % 4.3 % 3.6 % 3.5 % 3.2 %
Schedule of incurred but not reported liabilities and claims frequency	The table below provides information on IBNR liabilities and claims frequency for: (1) the Excess and Surplus Lines segment split between commercial auto and all non commercial auto, and (2) the Specialty Admitted Insurance segment split between individual risk workers’ compensation and fronting and programs: Excess and Surplus Lines — Excluding Commercial Auto Accident Year Incurred Losses IBNR Cumulative # of ​ ($ in thousands) 2010 $ 69,594 $ 1,347 1,429 2011 105,173 2,380 1,480 2012 103,061 2,042 1,806 2013 82,732 5,493 2,396 2014 88,904 9,855 2,162 2015 103,688 7,681 2,531 2016 126,971 23,882 2,933 2017 132,136 53,525 2,898 2018 158,458 95,477 3,935 2019 214,653 178,172 4,038 Excess and Surplus Lines — Commercial Auto Accident Year Incurred Losses and Loss Adj Expenses IBNR Cumulative # of Reported Claims ​ ($ in thousands) 2013 $ 1,277 $ 1 54 2014 18,303 150 7,763 2015 36,636 337 41,757 2016 147,122 5,258 89,003 2017 272,421 11,473 133,654 2018 230,220 34,896 95,889 2019 262,306 167,476 67,380 Specialty Admitted - Individual Risk Workers’ Compensation Accident Year Incurred Losses IBNR Cumulative # of ​ ($ in thousands) 2010 $ 27,099 $ 698 $ 1,604 2011 36,593 1,879 1,814 2012 28,186 1,090 1,323 2013 10,909 572 540 2014 12,704 423 850 2015 17,626 1,440 975 2016 15,800 3,245 836 2017 19,779 3,888 1,092 2018 16,288 3,495 1,230 2019 20,253 2,965 1,482   Specialty Admitted — Fronting and Programs Accident Year Incurred Losses IBNR Cumulative # of ​ ($ in thousands) 2013 $ 52 $ — 22 2014 3,083 147 857 2015 8,384 432 1,362 2016 15,522 1,861 2,807 2017 25,201 6,751 6,706 2018 20,677 10,142 7,158 2019 18,832 10,961 5,695 The table below provides information on IBNR liabilities for the Casualty Reinsurance segment: Accident Year Incurred Losses IBNR ​ ($ in thousands) 2010 $ 63,357 $ 723 2011 105,333 1,184 2012 146,045 2,025 2013 146,760 2,631 2014 126,160 3,487 2015 114,517 9,957 2016 108,222 18,720 2017 129,800 36,167 2018 119,098 29,472 2019 86,022 68,499

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Schedule of premiums written, premiums earned, and losses and loss adjustment expenses	Premiums written, premiums earned, and losses and loss adjustment expenses incurred are summarized as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Written premiums: ​ ​ ​ Direct $ 1,305,948 $ 1,027,222 $ 843,719 Assumed 164,787 139,551 238,186 Ceded (574,585 ) (404,101 ) (315,279 ) Net $ 896,150 $ 762,672 $ 766,626 Earned premiums: ​ ​ ​ Direct $ 1,182,501 $ 990,221 $ 842,182 Assumed 150,330 208,192 173,472 Ceded (509,085 ) (383,015 ) (274,545 ) Net $ 823,746 $ 815,398 $ 741,109 Losses and loss adjustment expenses: ​ ​ ​ Direct $ 953,548 $ 769,490 $ 626,318 Assumed 113,843 131,346 142,818 Ceded (395,289 ) (300,560 ) (213,759 ) Net $ 672,102 $ 600,276 $ 555,377

Junior Subordinated Debt (Table

Junior Subordinated Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Subordinated Borrowings [Abstract]
Schedule of Junior Subordinated Debt	The following table summarizes the nature and terms of the Junior Subordinated Debt and Trust Preferred Securities: ​ James River Capital Trust I James River James River Capital Trust III James River Franklin ​ ($ in thousands) Issue date May 26, 2004 December 15, 2004 June 15, 2006 December 11, 2007 January 10, 2008 Principal amount of Trust Preferred Securities $7,000 $15,000 $20,000 $54,000 $30,000 Principal amount of Junior Subordinated Debt $7,217 $15,464 $20,619 $55,670 $30,928 Carrying amount of Junior Subordinated Debt net of repurchases $7,217 $15,464 $20,619 $44,827 $15,928 Maturity date of Junior Subordinated Debt, unless accelerated earlier May 24, 2034 December 15, 2034 June 15, 2036 December 15, 2037 March 15, 2038 Trust common stock $217 $464 $619 $1,670 $928 Interest rate, per annum Three-Month LIBOR plus 4.0% Three-Month LIBOR plus 3.4% Three-Month LIBOR plus 3.0% Three-Month LIBOR plus 3.1% Three-Month LIBOR plus 4.0%

Capital Stock (Tables)

Capital Stock (Tables)	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Schedule of cash dividends declared	The Board of Directors declared the following cash dividends in 2019 , 2018 , and 2017 : Date of Declaration Dividend per Common Share Payable to Shareholders of Record on Payment Date Total Amount 2019 February 20, 2019 $0.30 March 11, 2019 March 29, 2019 $ 9,146,357 April 30, 2019 $0.30 June 10, 2019 June 28, 2019 $ 9,204,804 July 30, 2019 $0.30 September 16, 2019 September 30, 2019 $ 9,230,801 November 5, 2019 $0.30 December 16, 2019 December 31, 2019 $ 9,228,656 Total $1.20 $ 36,810,618 2018 ​ ​ ​ February 22, 2018 $0.30 March 12, 2018 March 30, 2018 $ 9,049,476 May 1, 2018 $0.30 June 11, 2018 June 29, 2018 $ 9,066,023 August 1, 2018 $0.30 September 10, 2018 September 28, 2018 $ 9,080,519 November 7, 2018 $0.30 December 14, 2018 December 28, 2018 $ 9,088,542 Total $1.20 $ 36,284,560 2017 February 14, 2017 $0.30 March 13, 2017 March 31, 2017 $ 8,878,147 May 2, 2017 $0.30 June 12, 2017 June 30, 2017 $ 8,917,471 August 1, 2017 $0.30 September 11, 2017 September 29, 2017 $ 8,943,279 November 1, 2017 $0.30 December 15, 2017 December 28, 2017 $ 8,974,196 November 1, 2017 $0.50 December 15, 2017 December 28, 2017 $ 14,956,994 Total $1.70 $ 50,670,087

Equity Awards (Tables)

Equity Awards (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Schedule of summary of option activity	The following table summarizes the option activity: ​ Year Ended December 31, ​ 2019 2018 2017 ​ Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Outstanding: ​ ​ ​ ​ ​ ​ Beginning of year 1,115,324 $ 29.02 1,479,236 $ 27.81 2,234,699 $ 22.84 Granted — $ — — $ — 205,244 $ 42.24 Exercised (459,415 ) $ 26.87 (308,025 ) $ 22.01 (898,218 ) $ 18.53 Forfeited (12,058 ) $ 36.84 (55,887 ) $ 35.69 (62,489 ) $ 30.80 End of year 643,851 $ 30.41 1,115,324 $ 29.02 1,479,236 $ 27.81 Exercisable, end of year 590,340 $ 29.34 814,421 $ 26.46 846,371 $ 22.35
Schedule of value of the options granted was estimated at the date of grant using the Black-Scholes-Merton	The value of the options granted was estimated at the date of grant using the Black-Scholes-Merton option pricing model using the following assumptions: ​ Year Ended December 31, ​ 2017 Risk-free interest rate 1.97 % Dividend yield 2.85 % Expected share price volatility 27.39 % Expected life 5.0 years
Schedule of summary of RSU activity	The following table summarizes RSU activity: ​ Year Ended December 31, ​ 2019 2018 2017 ​ Shares Weighted- Average Grant Date Fair Value Shares Weighted- Average Grant Date Fair Value Shares Weighted- Average Grant Date Fair Value Unvested, beginning of year 300,142 $ 39.22 178,882 $ 37.93 196,800 $ 24.38 Granted 197,078 $ 42.56 227,481 $ 39.74 137,034 $ 42.20 Vested (134,407 ) $ 37.99 (83,384 ) $ 37.61 (132,764 ) $ 24.24 Forfeited (22,445 ) $ 41.32 (22,837 ) $ 40.21 (22,188 ) $ 26.06 Unvested, end of year 340,368 $ 41.50 300,142 $ 39.22 178,882 $ 37.93
Schedule of summary of amount of expense and related tax benefit	The amount of expense and related tax benefit is summarized below: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Share based compensation expense $ 7,178 $ 6,228 $ 7,688 U.S. tax benefit on share based compensation expense $ 872 $ 716 $ 2,093

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of weighted-average tax rate as well as a reconciliation to total tax expense	A reconciliation of the difference between the Company’s Federal income tax provision on U.S. income and the expected Federal tax provision on U.S. income using the weighted-average tax rate as well as a reconciliation to total tax expense is as follows: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Federal income tax expense at applicable statutory rates $ 14,843 $ 7,875 $ 17,541 Tax-exempt investment income (230 ) (272 ) (586 ) Dividends received deduction (307 ) (307 ) (792 ) Excess tax benefits on share based compensation (1,099 ) (567 ) (2,114 ) Effect of tax rate reduction on deferred tax liability — 220 (3,498 ) Other 99 145 (90 ) Federal income tax expense $ 13,306 $ 7,094 $ 10,461 U.S. state income tax expense (benefit) 222 (86 ) 65 U.S. dividend withholding tax — — 1,053 Total income tax expense $ 13,528 $ 7,008 $ 11,579
Schedule of deferred tax asset at the current prevailing corporate income tax rate	The significant components of net deferred tax assets (liabilities) at the corporate income tax rate of 21% for the years ended December 31, 2019 and 2018 are summarized as follows: ​ December 31, ​ 2019 2018 ​ (in thousands) Deferred tax assets: ​ ​ Accrued compensation expenses $ 2,563 $ 2,456 Reserve for losses and loss adjustment expenses 12,286 7,482 Unearned premiums 8,226 5,711 Share based compensation 1,482 1,352 Allowance for doubtful accounts 1,188 829 Property and equipment 16 1,909 Other 1,974 1,903 Total deferred tax assets 27,735 21,642 Deferred tax liabilities: Intangible assets 7,381 7,461 Net unrealized gains 5,792 887 Deferred policy acquisition costs 4,448 3,491 Equity method investments 9,316 8,582 Other 134 167 Total deferred tax liabilities 27,071 20,588 Net deferred tax assets $ 664 $ 1,054

Other Operating Expenses and _2

Other Operating Expenses and Other Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Other Operating Expenses And Other Expenses [Abstract]
Schedule of other operating expenses	Other operating expenses consist of the following: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Amortization of policy acquisition costs $ 83,893 $ 111,103 $ 116,001 Other underwriting expenses of the insurance segments 59,351 63,029 55,662 Other operating expenses of the Corporate and Other segment 27,664 26,903 25,330 Total $ 170,908 $ 201,035 $ 196,993
Schedule of other expenses	Other expenses consist of the following: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Employee severance $ 1,055 $ 1,386 $ 147 Income on leased building the Company was previously deemed to own for accounting purposes — (623 ) (248 ) Legal and professional services related to secondary share offerings — 337 535 Other — — 105 Impairment of intangible asset — 200 — Total $ 1,055 $ 1,300 $ 539

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of components of comprehensive income	The following table summarizes the components of other comprehensive income (loss): ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Unrealized gains (losses) arising during the period, before U.S. income taxes $ 51,381 $ (23,201 ) $ 11,091 U.S. income taxes (3,510 ) 483 (2,374 ) Unrealized gains (losses) arising during the period, net of U.S. income taxes 47,871 (22,718 ) 8,717 Less reclassification adjustment: Net realized investment gains (losses) 1,081 (554 ) (835 ) U.S. income taxes (152 ) 39 333 Reclassification adjustment for investment gains (losses) realized in net income 929 (515 ) (502 ) Other comprehensive income (loss) $ 46,942 $ (22,203 ) $ 9,219

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Schedule of summary of company's segment results	Segment results are reported prior to the effects of the intercompany reinsurance agreements between the Company’s insurance subsidiaries. All gross written premiums and net earned premiums for all periods presented were generated from policies issued to U.S. based insureds. ​ Excess and Surplus Lines Specialty Admitted Insurance Casualty Reinsurance Corporate and Other Total ​ (in thousands) As of and for the Year Ended December 31, 2019 ​ ​ ​ ​ ​ Gross written premiums $ 922,320 $ 387,642 $ 160,773 $ — $ 1,470,735 Net earned premiums 625,528 54,338 143,880 — 823,746 Segment revenues 657,501 61,241 183,700 4,683 907,125 Net investment income 21,358 3,802 46,325 4,167 75,652 Interest expense — — — 10,596 10,596 Underwriting profit (loss) of operating segments 19,157 5,913 (7,161 ) — 17,909 Segment goodwill 181,831 — — — 181,831 Segment assets 2,481,934 786,433 1,699,473 56,565 5,024,405 As of and for the Year Ended December 31, 2018 ​ ​ ​ ​ ​ Gross written premiums $ 656,538 $ 374,346 $ 135,889 $ — $ 1,166,773 Net earned premiums 555,684 55,146 204,568 — 815,398 Segment revenues 580,785 56,717 243,178 4,919 885,599 Net investment income 14,456 3,262 38,838 4,700 61,256 Interest expense — — — 11,553 11,553 Underwriting profit of operating segments 42,834 6,972 5,103 — 54,909 Segment goodwill 181,831 — — — 181,831 Segment assets 972,111 633,689 1,453,754 77,222 3,136,776 As of and for the Year Ended ​ ​ ​ ​ ​ Gross written premiums $ 530,120 $ 316,430 $ 235,355 $ — $ 1,081,905 Net earned premiums 463,521 68,110 209,478 — 741,109 Segment revenues 493,853 70,366 240,751 12,655 817,625 Net investment income 15,014 2,532 31,507 12,066 61,119 Interest expense — — — 8,974 8,974 Underwriting profit (loss) of operating segments 29,693 3,166 (1,765 ) — 31,094 Segment goodwill 181,831 — — — 181,831 Segment assets 843,486 439,416 1,379,866 93,927 2,756,695
Schedule of underwriting profit (loss) of operating segments by individual segment and reconciliation to consolidated income before taxes	The following table reconciles the underwriting profit (loss) of operating segments by individual segment to income before taxes: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Underwriting profit (loss) of the operating segments: ​ ​ ​ Excess and Surplus Lines $ 19,157 $ 42,834 $ 29,693 Specialty Admitted Insurance 5,913 6,972 3,166 Casualty Reinsurance (7,161 ) 5,103 (1,765 ) Total underwriting profit of operating segments 17,909 54,909 31,094 Other operating expenses of the Corporate and Other segment (27,664 ) (26,903 ) (25,330 ) Underwriting (loss) profit (9,755 ) 28,006 5,764 Net investment income 75,652 61,256 61,119 Net realized and unrealized losses on investments (2,919 ) (5,479 ) (1,989 ) Other income 1,137 505 361 Other expenses (1,055 ) (1,300 ) (539 ) Interest expense (10,596 ) (11,553 ) (8,974 ) Amortization of intangible assets (597 ) (597 ) (597 ) Income before income taxes $ 51,867 $ 70,838 $ 55,145
Schedule of gross written premiums by segment and underwriting division	Gross written premiums by segment and underwriting division are presented below: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Commercial Auto $ 405,565 $ 322,126 $ 247,960 Excess Casualty 118,954 66,452 51,160 General Casualty 115,832 54,127 38,097 Manufacturers and Contractors 105,096 79,160 85,719 Energy 45,442 33,942 29,704 Excess Property 31,606 16,963 14,447 Allied Health 26,713 30,450 19,181 Life Sciences 24,462 16,636 12,981 Small Business 19,725 14,808 11,307 Environmental 16,539 10,499 7,920 Professional Liability 6,441 5,916 6,326 Sports and Entertainment 4,212 3,685 3,021 Medical Professionals 1,733 1,774 2,297 Total Excess and Surplus Lines segment 922,320 656,538 530,120 Specialty Admitted Insurance segment 387,642 374,346 316,430 Casualty Reinsurance segment 160,773 135,889 235,355 Total $ 1,470,735 $ 1,166,773 $ 1,081,905

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of assets measured at fair value on a recurring basis	Assets measured at fair value on a recurring basis as of December 31, 2019 are summarized below: Fair Value Measurements Using ​ Quoted Prices in Active Markets for Identical Assets Level 1 Significant Other Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total ​ (in thousands) Fixed maturity securities, available-for-sale: ​ ​ ​ ​ State and municipal $ — $ 167,101 $ — $ 167,101 Residential mortgage-backed — 264,146 — 264,146 Corporate — 632,221 — 632,221 Commercial mortgage and asset-backed — 252,457 252,457 U.S. Treasury securities and obligations guaranteed by the U.S. government 115,173 494 — 115,667 Redeemable preferred stock — 2,034 — 2,034 Total fixed maturity securities, available-for-sale $ 115,173 $ 1,318,453 $ — $ 1,433,626 Equity securities: Preferred stock $ — $ 62,747 $ — $ 62,747 Common stock 14,669 3,276 43 17,988 Total equity securities $ 14,669 $ 66,023 $ 43 $ 80,735 Short-term investments $ — $ 156,925 $ — $ 156,925 Assets measured at fair value on a recurring basis as of December 31, 2018 are summarized below: ​ Fair Value Measurements Using ​ Quoted Prices in Active Markets for Identical Assets Level 1 Significant Other Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total ​ ​ (in thousands) Fixed maturity securities, available-for-sale: ​ ​ ​ ​ State and municipal $ — $ 149,295 $ — $ 149,295 Residential mortgage-backed — 204,109 — 204,109 Corporate — 524,768 — 524,768 Commercial mortgage and asset-backed — 192,797 4,228 197,025 U.S. Treasury securities and obligations guaranteed by the U.S. government 106,651 542 — 107,193 Redeemable preferred stock — 1,812 — 1,812 Total fixed maturity securities, available-for-sale $ 106,651 $ 1,073,323 $ 4,228 $ 1,184,202 Equity securities: Preferred stock $ — $ 60,740 $ — $ 60,740 Common stock 16,674 757 214 17,645 Total equity securities $ 16,674 $ 61,497 $ 214 $ 78,385 Short-term investments $ 1,250 $ 80,716 $ — $ 81,966
Schedule of fair value on a recurring basis using significant unobservable inputs (Level 3)	A reconciliation of the beginning and ending balances of available-for-sale fixed maturity securities and equity securities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) is shown below: ​ Year Ended December 31, ​ 2019 2018 2017 ​ (in thousands) Beginning balance $ 4,442 $ 4,680 $ 5,000 Transfers in to Level 3 3,010 — — Transfers out of Level 3 (7,238 ) — — Purchases 214 — Sales — — — Maturities and calls (452 ) (320 ) Amortization of discount — — — Total gains or losses (realized/unrealized): Included in earnings (171 ) — — Included in other comprehensive income — — — Ending balance $ 43 $ 4,442 $ 4,680
Schedule of assets measured at fair value on a nonrecurring basis	Assets measured at fair value on a nonrecurring basis are summarized below: ​ Fair Value Measurements Using ​ Quoted Prices in Active Markets for Identical Assets Level 1 Significant Other Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total ​ (in thousands) December 31, 2019 ​ ​ ​ ​ Bank loan participations held-for-investment $ — $ — $ 6,949 $ 6,949 December 31, 2018 Bank loan participations held-for-investment $ — $ — $ — $ —
Schedule of carrying value and fair value	The carrying values and fair values of financial instruments are summarized below: ​ December 31, ​ 2019 2018 ​ Carrying Value Fair Value Carrying Value Fair Value ​ (in thousands) Assets ​ ​ ​ ​ Fixed maturity securities, available-for-sale $ 1,433,626 $ 1,433,626 $ 1,184,202 $ 1,184,202 Equity securities 80,735 80,735 78,385 78,385 Bank loan participations held-for-investment 260,864 252,423 260,972 250,697 Cash and cash equivalents 206,912 206,912 172,457 172,457 Restricted cash equivalents 1,199,164 1,199,164 — — Short-term investments 156,925 156,925 81,966 81,966 Other invested assets – notes receivable 13,250 18,756 13,250 18,687 Liabilities ​ ​ Senior debt 158,300 158,043 118,300 118,317 Junior subordinated debt 104,055 122,193 104,055 117,057

Statutory Matters (Tables)

Statutory Matters (Tables)	12 Months Ended
	Dec. 31, 2019
Statutory Matters [Abstract]
Schedule of statutory accounting	Combined net income, statutory capital and surplus and minimum required statutory capital and surplus, as determined in accordance with statutory accounting practices, for the U.S. insurance subsidiaries as of December 31, 2019 , 2018 , and 2017 and for the years then ended are summarized as follows: ​ 2019 2018 2017 ​ (in thousands) Statutory net income $ 3,586 $ 6,770 $ 31,881 Statutory capital and surplus 266,715 241,668 219,132 Minimum required statutory capital and surplus 111,208 24,850 25,000

Unaudited Selected Quarterly _2

Unaudited Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Schedule of unaudited quarterly results of operations	The following is a summary of the unaudited quarterly results of operations: ​ 2019 Quarter 2019 ​ First Second Third Fourth Year ​ (in thousands, except per share data) Gross written premiums $ 327,334 $ 380,003 $ 388,228 $ 375,170 $ 1,470,735 Total revenues 214,127 220,374 231,474 241,150 907,125 Net income (loss) 22,728 20,307 (25,167 ) 20,471 38,339 Comprehensive income (loss) 42,988 41,039 (15,710 ) 16,964 85,281 Earnings (loss) per share: ​ ​ ​ ​ ​ Basic (1) $ 0.76 $ 0.67 $ (0.83 ) $ 0.67 $ 1.27 Diluted (1) $ 0.75 $ 0.66 $ (0.83 ) $ 0.67 $ 1.25 2018 Quarter 2018 First Second Third Fourth Year (in thousands, except per share data) Gross written premiums $ 298,116 $ 293,378 $ 279,969 $ 295,310 $ 1,166,773 Total revenues 218,344 228,041 224,692 214,522 885,599 Net income 15,633 16,984 19,581 11,632 63,830 Comprehensive (loss) income (2,914 ) 10,426 15,192 18,923 41,627 Earnings per share: ​ ​ ​ ​ ​ Basic (1) $ 0.53 $ 0.57 $ 0.65 $ 0.39 $ 2.14 Diluted (1) $ 0.52 $ 0.56 $ 0.64 $ 0.38 $ 2.11 (1) Since the weighted-average shares for the quarter are calculated independently of the weighted-average shares for the year, quarterly earnings per share may not total to annual earnings per share.

Accounting Policies - Narrative

Accounting Policies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)companyloanshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares	Jan. 01, 2020USD ($)	Jan. 01, 2019USD ($)	Mar. 31, 2018USD ($)	Jan. 01, 2018USD ($)
Accounting Policies [Line Items]
Number of bank loans on nonaccrual status | loan	0
Allowance for doubtful accounts	$ 5,700	$ 3,900
Bad debt expense	2,500	1,500	$ 1,000
Allowance for doubtful accounts receivables written off	812	313	408
Fee income	9,100	13,900	17,000
Assets	(5,024,405)	(3,136,776)	$ (2,756,695)
Liabilities	(4,245,824)	(2,427,535)
Investment in variable interest entities	$ 31,200	$ 29,800
Common share equivalents excluded from calculations of diluted earnings per share | shares	9,735	180,329	174,380
Right-of-use assets	$ 17,200
Lease liabilities	18,232
Bank loan participations held-for-investment	$ 260,864	$ 260,972
Minimum
Accounting Policies [Line Items]
Intangible assets, useful life (in years)	7 years
Property and equipment, estimated useful lives (in years)	3 years
Maximum
Accounting Policies [Line Items]
Intangible assets, useful life (in years)	27 years 6 months
Property and equipment, estimated useful lives (in years)	10 years
Receivables greater than 90 days past due
Accounting Policies [Line Items]
Premiums receivable, past due	$ 3,300	$ 4,500
United States
Accounting Policies [Line Items]
Number of insurance companies | company	5
ASU 2018-02
Accounting Policies [Line Items]
Cumulative effect of adoption of ASU							$ 0
ASU 2016-02
Accounting Policies [Line Items]
Assets					$ 22,600
Liabilities					30,900
Cumulative effect of adoption of ASU					8,280
Right-of-use assets					17,200
Lease liabilities					$ 17,800
AOCI | ASU 2018-02
Accounting Policies [Line Items]
Cumulative effect of adoption of ASU						$ 711
Forecast | ASU 2016-13
Accounting Policies [Line Items]
Cumulative effect of adoption of ASU				$ (7,800)
Bank loan participations held-for-investment				$ (8,400)

Accounting Policies - Schedule

Accounting Policies - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Income	$ 20,471	$ (25,167)	$ 20,307	$ 22,728	$ 11,632	$ 19,581	$ 16,984	$ 15,633	$ 38,339	$ 63,830	$ 43,566
Weighted average common shares
Basic (in shares)									30,275,184	29,887,990	29,461,717
Common share equivalents (in shares)									398,740	419,111	811,432
Diluted (in shares)									30,673,924	30,307,101	30,273,149
Earnings per share
Basic earnings per share (in dollars per share)	$ 0.67	$ (0.83)	$ 0.67	$ 0.76	$ 0.39	$ 0.65	$ 0.57	$ 0.53	$ 1.27	$ 2.14	$ 1.48
Common share equivalents (in dollars per share)									(0.02)	(0.03)	(0.04)
Diluted earnings per share (in dollars per share)	$ 0.67	$ (0.83)	$ 0.66	$ 0.75	$ 0.38	$ 0.64	$ 0.56	$ 0.52	$ 1.25	$ 2.11	$ 1.44

Investments - Schedule of Avail

Investments - Schedule of Available-for-Sale Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	$ 1,398,533	$ 1,199,409
Fair Value	1,433,626	1,184,202
Fixed maturity securities:
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	1,398,533	1,199,409
Gross Unrealized Gains	37,691	6,060
Gross Unrealized Losses	(2,598)	(21,267)
Fair Value	1,433,626	1,184,202
State and municipal
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	159,894	147,160
Gross Unrealized Gains	7,949	3,422
Gross Unrealized Losses	(742)	(1,287)
Fair Value	167,101	149,295
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	261,524	208,869
Gross Unrealized Gains	3,244	577
Gross Unrealized Losses	(622)	(5,337)
Fair Value	264,146	204,109
Corporate
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	611,304	534,024
Gross Unrealized Gains	21,306	1,516
Gross Unrealized Losses	(389)	(10,772)
Fair Value	632,221	524,768
Commercial mortgage and asset-backed
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	249,309	199,528
Gross Unrealized Gains	3,954	310
Gross Unrealized Losses	(806)	(2,813)
Fair Value	252,457	197,025
U.S. Treasury securities and obligations guaranteed by the U.S. government
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	114,477	107,803
Gross Unrealized Gains	1,229	235
Gross Unrealized Losses	(39)	(845)
Fair Value	115,667	107,193
Redeemable preferred stock
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	2,025	2,025
Gross Unrealized Gains	9	0
Gross Unrealized Losses	0	(213)
Fair Value	$ 2,034	$ 1,812

Investments - Schedule of Amort

Investments - Schedule of Amortized Cost and Fair Value of Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
One year or less	$ 81,705
After one year through five years	456,076
After five years through ten years	219,717
After ten years	128,177
Residential mortgage-backed	261,524
Commercial mortgage and asset-backed	249,309
Redeemable preferred stock	2,025
Cost or Amortized Cost	1,398,533	$ 1,199,409
Fair Value
One year or less	82,048
After one year through five years	466,952
After five years through ten years	228,596
After ten years	137,393
Residential mortgage-backed	264,146
Commercial mortgage and asset-backed	252,457
Redeemable preferred stock	2,034
Total, Fair Value	$ 1,433,626	$ 1,184,202

Investments - Schedule of Gross

Investments - Schedule of Gross Unrealized Losses and Fair Values of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 154,118	$ 438,150
Less Than 12 Months, Unrealized Losses	(1,612)	(7,609)
12 Months or More, Fair Value	111,851	414,704
12 Months or More, Gross Unrealized Losses	(986)	(13,658)
Total, Fair Value	265,969	852,854
Total, Gross Unrealized Losses	(2,598)	(21,267)
State and municipal
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	30,028	19,733
Less Than 12 Months, Unrealized Losses	(741)	(284)
12 Months or More, Fair Value	667	47,018
12 Months or More, Gross Unrealized Losses	(1)	(1,003)
Total, Fair Value	30,695	66,751
Total, Gross Unrealized Losses	(742)	(1,287)
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	23,632	49,180
Less Than 12 Months, Unrealized Losses	(78)	(743)
12 Months or More, Fair Value	37,363	105,778
12 Months or More, Gross Unrealized Losses	(544)	(4,594)
Total, Fair Value	60,995	154,958
Total, Gross Unrealized Losses	(622)	(5,337)
Corporate
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	45,550	243,384
Less Than 12 Months, Unrealized Losses	(365)	(5,089)
12 Months or More, Fair Value	9,933	155,902
12 Months or More, Gross Unrealized Losses	(24)	(5,683)
Total, Fair Value	55,483	399,286
Total, Gross Unrealized Losses	(389)	(10,772)
Commercial mortgage and asset-backed
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	46,434	106,423
Less Than 12 Months, Unrealized Losses	(406)	(1,229)
12 Months or More, Fair Value	56,720	51,805
12 Months or More, Gross Unrealized Losses	(400)	(1,584)
Total, Fair Value	103,154	158,228
Total, Gross Unrealized Losses	(806)	(2,813)
U.S. Treasury securities and obligations guaranteed by the U.S. government
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	8,474	17,618
Less Than 12 Months, Unrealized Losses	(22)	(51)
12 Months or More, Fair Value	7,168	54,201
12 Months or More, Gross Unrealized Losses	(17)	(794)
Total, Fair Value	15,642	71,819
Total, Gross Unrealized Losses	$ (39)	(845)
Redeemable preferred stock
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value		1,812
Less Than 12 Months, Unrealized Losses		(213)
12 Months or More, Fair Value		0
12 Months or More, Gross Unrealized Losses		0
Total, Fair Value		1,812
Total, Gross Unrealized Losses		$ (213)

Investments - Narrative (Detail

Investments - Narrative (Details)	12 Months Ended
	Dec. 31, 2019USD ($)issuerloan	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)loan	Mar. 31, 2018USD ($)
Debt Securities, Available-for-sale [Line Items]
Number of available-for-sale securities held in an unrealized loss position | issuer	112
Total fair value of unrealized loss position securities	$ 265,969,000	$ 852,854,000
Gross unrealized losses	2,598,000	21,267,000
Impairment loss			$ 1,500,000
Number of impaired loans | loan			5
Carrying value of impaired loans	6,900,000		$ 5,100,000
Unpaid principal on impaired loans	14,300,000		8,400,000
Allowance for credit losses	7,200,000		3,200,000
Carrying value of loan	260,864,000	260,972,000
Net Investment Income	75,652,000	61,256,000	61,119,000
Fixed maturity securities, available-for-sale	1,433,626,000	1,184,202,000
Investment as collateral for outstanding letters of credit	464,500,000
Investments on deposit with state insurance departments	36,600,000	25,500,000
Investment Income	6,254,000	5,165,000	14,079,000
Bank Holding Company
Debt Securities, Available-for-sale [Line Items]
Interest income	343,000	343,000	343,000
Available-for-sale fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, available-for-sale	$ 1,433,626,000	1,184,202,000
Puerto Rico loan
Debt Securities, Available-for-sale [Line Items]
Unpaid principal on impaired loans			807,000
Carrying value of loan			0
Realized gain on repayment				$ 807,000
Impaired bank loans
Debt Securities, Available-for-sale [Line Items]
Number of impaired loans | loan	7
Number Of Issuers With Impaired Loans | issuer	6
Average recorded investment in impaired bank loans	$ 3,500,000	2,600,000	5,800,000
Net Investment Income	293,000	125,000	300,000
Net realized gain (loss) on changes in fair value of impaired bank loans	$ (8,900,000)	(858,000)	(2,400,000)
Loans from issuer experiencing liquidity concerns
Debt Securities, Available-for-sale [Line Items]
Number of impaired loans | loan	2
Number Of Issuers With Impaired Loans | issuer	1
Allowance for credit losses	$ 5,100,000
Bank loan participations
Debt Securities, Available-for-sale [Line Items]
Unamortized discount	2,400,000	1,800,000
Unamortized premium	$ 4,000	17,000
Standard & Poor's, BBB- Rating | Available-for-sale fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Percentage of available for sale securities	99.60%
Renewable Energy Bridge Financing Notes
Debt Securities, Available-for-sale [Line Items]
Interest income	$ 1,300,000	1,300,000	526,000
Investment Income	1,313,000	1,282,000	526,000
Bank Holding Company
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, available-for-sale	$ 3,200,000	$ 4,200,000
Bank Holding Company | Bank Holding Company
Debt Securities, Available-for-sale [Line Items]
Gross realized gains			$ 409,000

Investments - Summary of Net In

Investments - Summary of Net Investment Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Investment Income [Line Items]
Gross investment income	$ 80,373	$ 65,490	$ 65,049
Investment expense	(4,721)	(4,234)	(3,930)
Net investment income	75,652	61,256	61,119
Fixed maturity securities:
Net Investment Income [Line Items]
Gross investment income	39,875	34,129	26,833
Bank loan participations
Net Investment Income [Line Items]
Gross investment income	19,772	18,279	17,388
Equity securities
Net Investment Income [Line Items]
Gross investment income	5,262	5,240	5,045
Other invested assets
Net Investment Income [Line Items]
Gross investment income	6,254	5,165	14,079
Cash, cash equivalents, restricted cash equivalents, and short-term investments
Net Investment Income [Line Items]
Gross investment income	$ 9,210	$ 2,677	$ 1,704

Investments - Summary of Realiz

Investments - Summary of Realized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Fixed maturity securities, gross realized gains	$ 1,575	$ 422	$ 840
Fixed maturity securities, gross realized losses	(494)	(976)	(512)
Fixed maturity securities	1,081	(554)	328
Equity securities, gross realized gains	11	0	429
Equity securities, gross realized losses	(232)	(62)	(1,591)
Changes in fair values of equity securities	6,257	(5,970)	0
Equity securities	6,036	(6,032)	(1,162)
Bank loan participations, gross realized gain	846	2,279	2,407
Bank loan participations, gross realized losses	(10,902)	(1,166)	(3,557)
Bank loan participations	(10,056)	1,113	(1,150)
Short-term investments and other, gross realized gains	21	0	1
Short-term investments and other, gross realized losses	(1)	(6)	(6)
Short-term investments and other	20	(6)	(5)
Total	$ (2,919)	$ (5,479)	$ (1,989)

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Gross Unrealized Gains or Losses by Investment Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, change in gross unrealized gains (losses)	$ 50,300	$ (22,643)	$ 11,927
Fixed maturity securities:
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, change in gross unrealized gains (losses)	50,300	(22,643)	6,571
Equity securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, change in gross unrealized gains (losses)	$ 0	$ 0	$ 5,356

Investments - Summary of Privat

Investments - Summary of Private Debt and Equity Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Investment Income [Line Items]
Total other invested assets	$ 61,210	$ 72,321
Investment Income	6,254	5,165	$ 14,079
Distributions from equity method investments	2,834	7,499	7,333
Equity in net income of subsidiaries	4,598	3,540	13,209
Renewable energy LLCs
Net Investment Income [Line Items]
Total other invested assets	31,219	29,795
Investment Income	2,181	2,974	10,578
Renewable energy notes receivable
Net Investment Income [Line Items]
Total other invested assets	8,750	8,750
Investment Income	$ 1,313	1,282	526
Investment interest rate	15.00%
Interest income	$ 1,300	1,300	526
Limited partnerships
Net Investment Income [Line Items]
Total other invested assets	16,741	29,276
Investment Income	2,417	566	2,632
Bank holding companies
Net Investment Income [Line Items]
Total other invested assets	4,500	4,500
Investment Income	343	343	343
Corporate and other segment | Limited partnerships
Net Investment Income [Line Items]
Carrying value of investments	3,400	3,100
Equity in net income of subsidiaries	327	70	394
Excess and Surplus Lines | Limited partnerships
Net Investment Income [Line Items]
Carrying value of investments	13,300	26,200
Equity in net income of subsidiaries	2,100	496	2,200
Commitment to investment in limited partnership	625
Investment in LLC | Corporate and other segment
Net Investment Income [Line Items]
Distributions from equity method investments	$ 757	5,800
Bank Holding Company
Net Investment Income [Line Items]
Investment interest rate	7.60%
Interest income	$ 343	$ 343	$ 343
Investment in subordinated notes	$ 4,500
Minimum | Investment in LLC | Corporate and other segment
Net Investment Income [Line Items]
Ownership percentage	2.60%
Maximum | Investment in LLC | Corporate and other segment
Net Investment Income [Line Items]
Ownership percentage	32.20%

Deferred Policy Acquisition C_3

Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance at beginning of period	$ 54,450	$ 72,365	$ 64,789
Policy acquisition costs deferred:
Commissions	67,303	72,473	107,387
Underwriting and other issue expenses	24,146	20,715	16,190
Policy acquisition costs deferred	91,449	93,188	123,577
Amortization of policy acquisition costs	(83,893)	(111,103)	(116,001)
Net change	7,556	(17,915)	7,576
Balance at end of period	$ 62,006	$ 54,450	$ 72,365

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 11, 2007
Business Acquisition [Line Items]
Goodwill impairment	$ 0	$ 0	$ 0
Goodwill	181,831,000	181,831,000	181,831,000
Accumulated goodwill impairment losses	99,600,000	99,600,000
Identifiable intangibles not subject to amortization	31,164,000	31,164,000
Impairment of intangible assets	0	200,000	0
Amortization of intangible assets	597,000	597,000	597,000
Excess and Surplus Lines
Business Acquisition [Line Items]
Goodwill	181,831,000	181,831,000	181,831,000
Amortization of intangible assets	362,000	362,000	362,000
Specialty Admitted Insurance
Business Acquisition [Line Items]
Goodwill	0	0	0
Impairment of intangible assets		200,000
Amortization of intangible assets	$ 235,000	235,000	$ 235,000
James River Group, Inc.
Business Acquisition [Line Items]
Percentage of outstanding shares acquired				100.00%
State Licenses
Business Acquisition [Line Items]
Identifiable intangibles not subject to amortization		$ 0

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Acquired Intangible Assets [Line Items]
Identifiable intangibles not subject to amortization	$ 31,164	$ 31,164
Identifiable intangible assets subject to amortization
Gross Carrying Amount	11,611	11,611
Accumulated Amortization	5,835	5,238
Total intangible assets, gross	42,775	42,775
Broker relationships
Identifiable intangible assets subject to amortization
Gross Carrying Amount	11,611	11,611
Accumulated Amortization	$ 5,835	5,238
Weighted-Average Life (in years)	24 years 7 months 6 days
Trademarks
Acquired Intangible Assets [Line Items]
Identifiable intangibles not subject to amortization	$ 22,200	22,200
Insurance licenses and authorities
Acquired Intangible Assets [Line Items]
Identifiable intangibles not subject to amortization	$ 8,964	$ 8,964

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Schedule of Future Estimated Amortization (Details) $ in Thousands	Dec. 31, 2019USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2020	$ 538
2021	363
2022	363
2023	363
2024	363
Thereafter	3,786
Total	$ 5,776

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Summary of Changes in Net Carrying Value of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets [Roll Forward]
Net Carrying Value	$ 37,537	$ 38,334
Amortization	(597)	(597)	$ (597)
Impairment Losses	0	(200)	0
Net Carrying Value	36,940	37,537	38,334
Excess and Surplus Lines
Intangible Assets [Roll Forward]
Net Carrying Value	30,565	30,927
Amortization	(362)	(362)	(362)
Impairment Losses	0	0
Net Carrying Value	30,203	30,565	30,927
Excess and Surplus Lines | Trademarks
Intangible Assets [Roll Forward]
Net Carrying Value	19,700	19,700
Amortization	0	0
Impairment Losses	0	0
Net Carrying Value	19,700	19,700	19,700
Excess and Surplus Lines | Insurance licenses and authorities
Intangible Assets [Roll Forward]
Net Carrying Value	4,900	4,900
Amortization	0	0
Impairment Losses	0	0
Net Carrying Value	4,900	4,900	4,900
Excess and Surplus Lines | Broker relationships
Intangible Assets [Roll Forward]
Net Carrying Value	5,965	6,327
Amortization	(362)	(362)
Impairment Losses	0	0
Net Carrying Value	5,603	5,965	6,327
Specialty Admitted Insurance
Intangible Assets [Roll Forward]
Net Carrying Value	6,972	7,407
Amortization	(235)	(235)	(235)
Impairment Losses	0	(200)
Net Carrying Value	6,737	6,972	7,407
Specialty Admitted Insurance | Trademarks
Intangible Assets [Roll Forward]
Net Carrying Value	2,500	2,500
Amortization	0	0
Impairment Losses	0	0
Net Carrying Value	2,500	2,500	2,500
Specialty Admitted Insurance | Insurance licenses and authorities
Intangible Assets [Roll Forward]
Net Carrying Value	4,065	4,265
Amortization	0	0
Impairment Losses	0	(200)
Net Carrying Value	4,065	4,065	4,265
Specialty Admitted Insurance | Broker relationships
Intangible Assets [Roll Forward]
Net Carrying Value	407	642
Amortization	(235)	(235)
Impairment Losses	0	0
Net Carrying Value	$ 172	$ 407	$ 642

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, cost basis	$ 9,702	$ 41,056
Accumulated depreciation	(7,934)	(17,745)
Property and equipment, net	1,768	23,311
Building, leased for which the Company was previously deemed the owner for accounting purposes
Property, Plant and Equipment [Line Items]
Property and equipment, cost basis	0	30,971
Electronic data processing hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment, cost basis	7,522	7,423
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, cost basis	$ 2,180	$ 2,662

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Right-of-use assets	$ 17,200
Lease liabilities	$ 18,232
Weighted average discount rate	4.30%
Weighted average remaining lease term	5 years 3 months 18 days
Operating lease costs	$ 5,200	$ 4,600	$ 4,200
Minority interest in partnership
Related Party Transaction [Line Items]
Lease liabilities	$ 11,900

Leases - Summary of Operating L

Leases - Summary of Operating Lease Liabilities Maturities (Details) $ in Thousands	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 4,024
2021	3,993
2022	3,800
2023	3,619
2024	2,422
Thereafter	2,546
Total lease payments	20,404
Less imputed interest	(2,172)
Total operating lease liabilities	$ 18,232

Reserve for Losses and Loss A_3

Reserve for Losses and Loss Adjustment Expenses - Reserve for Losses and Loss Adjustment Expenses, Net of Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) [Abstract]
Reserve for losses and loss adjustment expenses net of reinsurance recoverables at beginning of period	$ 1,194,088	$ 989,825	$ 761,128
Add: Incurred losses and loss adjustment expenses net of reinsurance:
Current year	603,094	582,604	533,905
Prior years	69,008	17,672	21,472
Total incurred losses and loss and adjustment expenses	672,102	600,276	555,377
Deduct: Loss and loss adjustment expense payments net of reinsurance:
Current year	75,249	86,355	103,205
Prior years	413,480	309,658	223,475
Total loss and loss adjustment expense payments	488,729	396,013	326,680
Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period	1,377,461	1,194,088	989,825
Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period	668,045	467,371	302,524
Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period	$ 2,045,506	$ 1,661,459	$ 1,292,349

Reserve for Losses and Loss A_4

Reserve for Losses and Loss Adjustment Expenses - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses	$ (69,008)	$ (17,672)	$ (21,472)
Excess and Surplus Lines
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses	(51,200)	(15,000)	(20,000)
Specialty Admitted Insurance | Accident Years Prior to 2018
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses	5,300
Specialty Admitted Insurance | Accident years 2014 through 2016
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses		5,600
Specialty Admitted Insurance | Accident years 2010 through 2015
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses			2,700
Casualty Reinsurance | Accident Years 2011 Through 2016
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses	(23,100)
Casualty Reinsurance | Accident years at least four years old
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses		(8,200)
Casualty Reinsurance | Accident years 2010 through 2013
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses			(4,200)
Excluding Commercial Auto | Excess and Surplus Lines
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses	6,200
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2017
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses		5,700
Excluding Commercial Auto | Excess and Surplus Lines | Accident years 2014 through 2016
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses			18,600
Commercial Auto | Excess and Surplus Lines | Accident years 2016 and 2017
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses	$ (57,400)
Commercial Auto | Excess and Surplus Lines | Accident year 2016
Favorable development on prior year loss reserves
Reserves for losses and loss adjustment expenses		$ (20,700)	$ (38,700)

Reserve for Losses and Loss A_5

Reserve for Losses and Loss Adjustment Expenses - Incurred Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Casualty Reinsurance
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	$ 1,145,314
Cumulative paid losses and loss adjustment expenses, net of reinsurance	863,436
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	1,798
Total outstanding losses and loss adjustment expenses, net of reinsurance	283,676
Casualty Reinsurance | Accident year 2010
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	63,357	$ 62,605	$ 61,619	$ 60,978	$ 60,949	$ 61,344	$ 62,714	$ 61,068	$ 60,476	$ 64,413
Cumulative paid losses and loss adjustment expenses, net of reinsurance	59,634	58,707	57,013	54,659	52,761	49,263	44,921	38,430	31,500	21,918
Casualty Reinsurance | Accident year 2011
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	105,333	103,196	101,276	99,282	98,993	97,812	97,366	103,123	114,908
Cumulative paid losses and loss adjustment expenses, net of reinsurance	99,511	97,715	94,627	90,287	87,267	78,164	68,616	61,922	48,688
Casualty Reinsurance | Accident year 2012
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	146,045	143,305	139,978	136,813	135,594	131,281	132,388	148,251
Cumulative paid losses and loss adjustment expenses, net of reinsurance	137,430	133,606	128,567	121,026	113,943	97,215	81,859	73,124
Casualty Reinsurance | Accident year 2013
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	146,760	143,124	137,801	134,446	131,352	130,361	133,230
Cumulative paid losses and loss adjustment expenses, net of reinsurance	134,644	127,732	119,256	108,396	93,902	75,094	59,756
Casualty Reinsurance | Accident year 2014
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	126,160	121,200	116,981	114,636	115,927	118,881
Cumulative paid losses and loss adjustment expenses, net of reinsurance	110,374	101,366	89,899	76,302	58,601	41,421
Casualty Reinsurance | Accident year 2015
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	114,517	109,117	108,699	108,870	119,157
Cumulative paid losses and loss adjustment expenses, net of reinsurance	90,661	80,208	68,002	53,986	40,021
Casualty Reinsurance | Accident year 2016
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	108,222	103,544	105,533	112,759
Cumulative paid losses and loss adjustment expenses, net of reinsurance	78,145	65,409	50,905	36,268
Casualty Reinsurance | Accident year 2017
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	129,800	128,472	134,628
Cumulative paid losses and loss adjustment expenses, net of reinsurance	90,117	72,891	47,739
Casualty Reinsurance | Accident year 2018
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	119,098	121,529
Cumulative paid losses and loss adjustment expenses, net of reinsurance	50,274	30,903
Casualty Reinsurance | Accident year 2019
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	86,022
Cumulative paid losses and loss adjustment expenses, net of reinsurance	12,646
Commercial Auto | Excess and Surplus Lines
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	968,285
Cumulative paid losses and loss adjustment expenses, net of reinsurance	535,232
Total outstanding losses and loss adjustment expenses, net of reinsurance	433,053
Commercial Auto | Excess and Surplus Lines | Accident year 2013
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	1,277	1,277	1,301	1,351	1,451	1,300	1,255
Cumulative paid losses and loss adjustment expenses, net of reinsurance	1,275	1,275	1,275	1,291	1,285	1,182	60
Commercial Auto | Excess and Surplus Lines | Accident year 2014
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	18,303	19,779	18,953	17,233	14,071	20,487
Cumulative paid losses and loss adjustment expenses, net of reinsurance	17,745	18,678	16,359	12,679	8,645	6,166
Commercial Auto | Excess and Surplus Lines | Accident year 2015
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	36,636	36,139	35,149	33,113	30,109
Cumulative paid losses and loss adjustment expenses, net of reinsurance	34,819	31,592	24,282	15,234	8,356
Commercial Auto | Excess and Surplus Lines | Accident year 2016
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	147,122	126,791	109,286	74,340
Cumulative paid losses and loss adjustment expenses, net of reinsurance	125,108	89,381	54,054	18,295
Commercial Auto | Excess and Surplus Lines | Accident year 2017
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	272,421	208,743	207,355
Cumulative paid losses and loss adjustment expenses, net of reinsurance	192,961	107,377	41,467
Commercial Auto | Excess and Surplus Lines | Accident year 2018
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	230,220	255,881
Cumulative paid losses and loss adjustment expenses, net of reinsurance	119,099	45,136
Commercial Auto | Excess and Surplus Lines | Accident year 2019
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	262,306
Cumulative paid losses and loss adjustment expenses, net of reinsurance	44,225
Excluding Commercial Auto | Excess and Surplus Lines
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	1,185,370
Cumulative paid losses and loss adjustment expenses, net of reinsurance	625,534
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	8,978
Total outstanding losses and loss adjustment expenses, net of reinsurance	568,814
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2010
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	69,594	71,312	70,913	70,294	69,964	69,080	73,035	78,117	80,569	78,424
Cumulative paid losses and loss adjustment expenses, net of reinsurance	65,915	65,246	64,214	61,307	57,371	52,071	45,641	35,812	26,418	13,673
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2011
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	105,173	106,536	106,643	106,130	106,381	106,564	114,473	119,927	111,190
Cumulative paid losses and loss adjustment expenses, net of reinsurance	101,728	99,798	98,684	94,998	90,884	81,696	72,732	53,109	27,684
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2012
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	103,061	101,271	99,619	97,306	96,497	97,829	98,672	97,908
Cumulative paid losses and loss adjustment expenses, net of reinsurance	94,588	88,812	82,545	74,869	63,216	49,604	33,757	6,944
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2013
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	82,732	83,855	82,830	81,009	85,433	96,064	96,729
Cumulative paid losses and loss adjustment expenses, net of reinsurance	71,035	66,553	59,641	44,421	30,382	14,509	3,867
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2014
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	88,904	84,074	82,232	90,267	104,092	114,942
Cumulative paid losses and loss adjustment expenses, net of reinsurance	71,549	58,774	43,891	28,212	16,969	3,412
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2015
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	103,688	102,434	104,847	113,417	126,443
Cumulative paid losses and loss adjustment expenses, net of reinsurance	73,455	55,911	34,801	17,164	4,048
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2016
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	126,971	126,050	125,093	138,507
Cumulative paid losses and loss adjustment expenses, net of reinsurance	70,105	46,045	22,852	5,180
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2017
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	132,136	131,897	144,349
Cumulative paid losses and loss adjustment expenses, net of reinsurance	42,764	22,956	5,290
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2018
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	158,458	167,004
Cumulative paid losses and loss adjustment expenses, net of reinsurance	26,160	6,000
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2019
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	214,653
Cumulative paid losses and loss adjustment expenses, net of reinsurance	8,235
Fronting and Programs | Specialty Admitted Insurance
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	91,751
Cumulative paid losses and loss adjustment expenses, net of reinsurance	43,424
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	48,327
Total outstanding losses and loss adjustment expenses, net of reinsurance	48,727
Fronting and Programs | Specialty Admitted Insurance | Accident year 2013
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	52	52	52	52	52	80	104
Cumulative paid losses and loss adjustment expenses, net of reinsurance	52	52	52	52	52	52	28
Fronting and Programs | Specialty Admitted Insurance | Accident year 2014
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	3,083	3,228	3,425	3,818	3,468	3,460
Cumulative paid losses and loss adjustment expenses, net of reinsurance	2,916	2,854	2,728	2,369	1,687	883
Fronting and Programs | Specialty Admitted Insurance | Accident year 2015
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	8,384	8,974	9,358	9,632	7,136
Cumulative paid losses and loss adjustment expenses, net of reinsurance	7,329	6,919	6,165	4,666	2,058
Fronting and Programs | Specialty Admitted Insurance | Accident year 2016
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	15,522	14,682	15,670	11,542
Cumulative paid losses and loss adjustment expenses, net of reinsurance	10,732	6,888	5,123	1,894
Fronting and Programs | Specialty Admitted Insurance | Accident year 2017
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	25,201	24,271	21,229
Cumulative paid losses and loss adjustment expenses, net of reinsurance	13,065	6,682	1,223
Fronting and Programs | Specialty Admitted Insurance | Accident year 2018
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	20,677	21,758
Cumulative paid losses and loss adjustment expenses, net of reinsurance	4,972	885
Fronting and Programs | Specialty Admitted Insurance | Accident year 2019
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	18,832
Cumulative paid losses and loss adjustment expenses, net of reinsurance	4,358
Individual Risk Workers' Compensation | Specialty Admitted Insurance
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	205,237
Cumulative paid losses and loss adjustment expenses, net of reinsurance	167,741
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	1,039
Total outstanding losses and loss adjustment expenses, net of reinsurance	43,191
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2010
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	27,099	27,099	27,098	27,590	28,938	28,963	30,373	30,464	28,736	27,209
Cumulative paid losses and loss adjustment expenses, net of reinsurance	26,365	26,358	26,352	26,345	25,477	25,210	23,898	21,805	16,245	$ 7,157
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2011
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	36,593	36,593	36,594	37,455	38,311	38,999	40,154	41,421	37,834
Cumulative paid losses and loss adjustment expenses, net of reinsurance	34,638	34,614	34,334	34,287	34,240	33,204	29,021	23,127	$ 10,123
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2012
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	28,186	28,186	28,174	28,255	29,689	31,490	32,420	32,116
Cumulative paid losses and loss adjustment expenses, net of reinsurance	26,994	26,963	26,932	26,897	26,435	24,755	20,308	$ 9,222
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2013
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	10,909	10,909	10,907	11,578	12,786	13,668	12,525
Cumulative paid losses and loss adjustment expenses, net of reinsurance	10,337	10,309	10,263	10,246	9,846	8,723	$ 4,487
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2014
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	12,704	12,704	13,890	14,620	16,652	16,638
Cumulative paid losses and loss adjustment expenses, net of reinsurance	12,282	12,282	12,236	12,041	10,648	$ 4,633
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2015
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	17,626	18,376	19,741	21,274	20,938
Cumulative paid losses and loss adjustment expenses, net of reinsurance	15,901	15,889	15,118	13,285	$ 6,604
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2016
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	15,800	18,050	20,299	21,678
Cumulative paid losses and loss adjustment expenses, net of reinsurance	12,432	12,135	10,227	$ 4,664
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2017
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	19,779	22,071	24,869
Cumulative paid losses and loss adjustment expenses, net of reinsurance	14,285	12,782	$ 6,546
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2018
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	16,288	16,432
Cumulative paid losses and loss adjustment expenses, net of reinsurance	9,034	$ 4,497
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2019
Claims Development [Line Items]
Incurred losses and loss adjustment expenses, net of reinsurance	20,253
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 5,473

Reserve for Losses and Loss A_6

Reserve for Losses and Loss Adjustment Expenses - Cumulative Paid Losses and Loss Adjustment Expenses (Details) $ in Thousands	Dec. 31, 2019USD ($)Claimclaim	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)
Casualty Reinsurance
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 863,436
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	1,798
Total outstanding losses and loss adjustment expenses, net of reinsurance	283,676
Casualty Reinsurance | Accident year 2010
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	59,634	$ 58,707	$ 57,013	$ 54,659	$ 52,761	$ 49,263	$ 44,921	$ 38,430	$ 31,500	$ 21,918
Casualty Reinsurance | Accident year 2011
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	99,511	97,715	94,627	90,287	87,267	78,164	68,616	61,922	48,688
Casualty Reinsurance | Accident year 2012
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	137,430	133,606	128,567	121,026	113,943	97,215	81,859	73,124
Casualty Reinsurance | Accident year 2013
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	134,644	127,732	119,256	108,396	93,902	75,094	59,756
Casualty Reinsurance | Accident year 2014
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	110,374	101,366	89,899	76,302	58,601	41,421
Casualty Reinsurance | Accident year 2015
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	90,661	80,208	68,002	53,986	40,021
Casualty Reinsurance | Accident year 2016
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	78,145	65,409	50,905	36,268
Casualty Reinsurance | Accident year 2017
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	90,117	72,891	47,739
Casualty Reinsurance | Accident year 2018
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	50,274	30,903
Casualty Reinsurance | Accident year 2019
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	12,646
Excluding Commercial Auto | Excess and Surplus Lines
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	625,534
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	8,978
Total outstanding losses and loss adjustment expenses, net of reinsurance	$ 568,814
Claims outstanding | claim	60
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2010
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 65,915	65,246	64,214	61,307	57,371	52,071	45,641	35,812	26,418	13,673
Claims outstanding | Claim	1,429
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2011
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 101,728	99,798	98,684	94,998	90,884	81,696	72,732	53,109	27,684
Claims outstanding | Claim	1,480
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2012
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 94,588	88,812	82,545	74,869	63,216	49,604	33,757	6,944
Claims outstanding | Claim	1,806
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2013
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 71,035	66,553	59,641	44,421	30,382	14,509	3,867
Claims outstanding | Claim	2,396
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2014
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 71,549	58,774	43,891	28,212	16,969	3,412
Claims outstanding | Claim	2,162
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2015
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 73,455	55,911	34,801	17,164	4,048
Claims outstanding | Claim	2,531
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2016
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 70,105	46,045	22,852	5,180
Claims outstanding | Claim	2,933
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2017
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 42,764	22,956	5,290
Claims outstanding | Claim	2,898
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2018
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 26,160	6,000
Claims outstanding | Claim	3,935
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2019
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 8,235
Claims outstanding | Claim	4,038
Fronting and Programs | Specialty Admitted Insurance
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 43,424
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	48,327
Outstanding losses and loss adjustment expenses assumed from involuntary workers compensation pools	400
Total outstanding losses and loss adjustment expenses, net of reinsurance	48,727
Fronting and Programs | Specialty Admitted Insurance | Accident year 2013
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 52	52	52	52	52	52	28
Claims outstanding | Claim	22
Fronting and Programs | Specialty Admitted Insurance | Accident year 2014
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 2,916	2,854	2,728	2,369	1,687	883
Claims outstanding | Claim	857
Fronting and Programs | Specialty Admitted Insurance | Accident year 2015
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 7,329	6,919	6,165	4,666	2,058
Claims outstanding | Claim	1,362
Fronting and Programs | Specialty Admitted Insurance | Accident year 2016
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 10,732	6,888	5,123	1,894
Claims outstanding | Claim	2,807
Fronting and Programs | Specialty Admitted Insurance | Accident year 2017
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 13,065	6,682	1,223
Claims outstanding | Claim	6,706
Fronting and Programs | Specialty Admitted Insurance | Accident year 2018
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 4,972	885
Claims outstanding | Claim	7,158
Fronting and Programs | Specialty Admitted Insurance | Accident year 2019
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 4,358
Claims outstanding | Claim	5,695
Individual Risk Workers' Compensation | Specialty Admitted Insurance
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 167,741
All outstanding losses and loss adjustment expenses prior to 2010, net of reinsurance	1,039
Outstanding losses and loss adjustment expenses assumed from involuntary workers compensation pools	4,656
Total outstanding losses and loss adjustment expenses, net of reinsurance	$ 43,191
Claims outstanding | claim	4
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2010
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 26,365	26,358	26,352	26,345	25,477	25,210	23,898	21,805	16,245	$ 7,157
Claims outstanding | Claim	1,604
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2011
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 34,638	34,614	34,334	34,287	34,240	33,204	29,021	23,127	$ 10,123
Claims outstanding | Claim	1,814
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2012
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 26,994	26,963	26,932	26,897	26,435	24,755	20,308	$ 9,222
Claims outstanding | Claim	1,323
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2013
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 10,337	10,309	10,263	10,246	9,846	8,723	4,487
Claims outstanding | Claim	540
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2014
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 12,282	12,282	12,236	12,041	10,648	4,633
Claims outstanding | Claim	850
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2015
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 15,901	15,889	15,118	13,285	6,604
Claims outstanding | Claim	975
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2016
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 12,432	12,135	10,227	4,664
Claims outstanding | Claim	836
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2017
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 14,285	12,782	6,546
Claims outstanding | Claim	1,092
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2018
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 9,034	4,497
Claims outstanding | Claim	1,230
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2019
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 5,473
Claims outstanding | Claim	1,482
Commercial Auto | Excess and Surplus Lines
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 535,232
Total outstanding losses and loss adjustment expenses, net of reinsurance	433,053
Commercial Auto | Excess and Surplus Lines | Accident year 2013
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 1,275	1,275	1,275	1,291	1,285	1,182	$ 60
Claims outstanding | Claim	54
Commercial Auto | Excess and Surplus Lines | Accident year 2014
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 17,745	18,678	16,359	12,679	8,645	$ 6,166
Claims outstanding | Claim	7,763
Commercial Auto | Excess and Surplus Lines | Accident year 2015
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 34,819	31,592	24,282	15,234	$ 8,356
Claims outstanding | Claim	41,757
Commercial Auto | Excess and Surplus Lines | Accident year 2016
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 125,108	89,381	54,054	$ 18,295
Claims outstanding | Claim	89,003
Commercial Auto | Excess and Surplus Lines | Accident year 2017
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 192,961	107,377	$ 41,467
Claims outstanding | Claim	133,654
Commercial Auto | Excess and Surplus Lines | Accident year 2018
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 119,099	$ 45,136
Claims outstanding | Claim	95,889
Commercial Auto | Excess and Surplus Lines | Accident year 2019
Claims Development [Line Items]
Cumulative paid losses and loss adjustment expenses, net of reinsurance	$ 44,225
Claims outstanding | Claim	67,380

Reserve for Losses and Loss A_7

Reserve for Losses and Loss Adjustment Expenses - Reserves for Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Claims Development [Line Items]
Net reserve for losses and loss adjustment expenses	$ 1,377,461	$ 1,194,088	$ 989,825	$ 761,128
Reinsurance recoverable on unpaid losses	668,045	467,371	302,524
Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period	2,045,506	$ 1,661,459	$ 1,292,349
Casualty Reinsurance
Claims Development [Line Items]
Net reserve for losses and loss adjustment expenses	283,676
Fronting and Programs | Specialty Admitted Insurance
Claims Development [Line Items]
Net reserve for losses and loss adjustment expenses	48,727
Excluding Commercial Auto | Excess and Surplus Lines
Claims Development [Line Items]
Net reserve for losses and loss adjustment expenses	568,814
Commercial Auto | Excess and Surplus Lines
Claims Development [Line Items]
Net reserve for losses and loss adjustment expenses	433,053
Individual Risk Workers' Compensation | Specialty Admitted Insurance
Claims Development [Line Items]
Net reserve for losses and loss adjustment expenses	$ 43,191

Reserve for Losses and Loss A_8

Reserve for Losses and Loss Adjustment Expenses - Average Annual Percentage Payouts of Incurred Claims (Details)	Dec. 31, 2019
Casualty Reinsurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	21.10%
Year 2	16.40%
Year 3	12.20%
Year 4	8.90%
Year 5	6.40%
Year 6	5.30%
Year 7	4.30%
Year 8	3.60%
Year 9	3.50%
Year 10	3.20%
Fronting and Programs | Specialty Admitted Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	18.70%
Year 2	22.40%
Year 3	24.30%
Year 4	16.10%
Year 5	10.50%
Year 6	5.30%
Excluding Commercial Auto | E&S
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	9.50%
Year 2	15.70%
Year 3	17.20%
Year 4	18.50%
Year 5	14.50%
Year 6	8.00%
Year 7	5.40%
Year 8	3.80%
Year 9	2.00%
Year 10	1.10%
Commercial Auto | E&S
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	20.40%
Year 2	38.10%
Year 3	16.00%
Year 4	14.10%
Year 5	7.20%
Year 6	2.60%
Year 7	1.50%
Individual Risk Workers' Compensation | Specialty Admitted Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	27.90%
Year 2	30.90%
Year 3	16.00%
Year 4	10.20%
Year 5	7.20%
Year 6	1.20%
Year 7	1.70%
Year 8	0.90%
Year 9	0.10%
Year 10	1.30%

Reserve for Losses and Loss A_9

Reserve for Losses and Loss Adjustment Expenses - IBNR Liabilities and Claims Frequency (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)Claimclaim	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 672,102	$ 600,276	$ 555,377
Casualty Reinsurance | Accident year 2010
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	63,357
IBNR	723
Casualty Reinsurance | Accident year 2011
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	105,333
IBNR	1,184
Casualty Reinsurance | Accident year 2012
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	146,045
IBNR	2,025
Casualty Reinsurance | Accident year 2013
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	146,760
IBNR	2,631
Casualty Reinsurance | Accident year 2014
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	126,160
IBNR	3,487
Casualty Reinsurance | Accident year 2015
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	114,517
IBNR	9,957
Casualty Reinsurance | Accident year 2016
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	108,222
IBNR	18,720
Casualty Reinsurance | Accident year 2017
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	129,800
IBNR	36,167
Casualty Reinsurance | Accident year 2018
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	119,098
IBNR	29,472
Casualty Reinsurance | Accident year 2019
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	86,022
IBNR	68,499
Fronting and Programs | Specialty Admitted Insurance | Accident year 2013
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	52
IBNR	$ 0
Cumulative Number of Reported Claims | Claim	22
Fronting and Programs | Specialty Admitted Insurance | Accident year 2014
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 3,083
IBNR	$ 147
Cumulative Number of Reported Claims | Claim	857
Fronting and Programs | Specialty Admitted Insurance | Accident year 2015
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 8,384
IBNR	$ 432
Cumulative Number of Reported Claims | Claim	1,362
Fronting and Programs | Specialty Admitted Insurance | Accident year 2016
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 15,522
IBNR	$ 1,861
Cumulative Number of Reported Claims | Claim	2,807
Fronting and Programs | Specialty Admitted Insurance | Accident year 2017
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 25,201
IBNR	$ 6,751
Cumulative Number of Reported Claims | Claim	6,706
Fronting and Programs | Specialty Admitted Insurance | Accident year 2018
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 20,677
IBNR	$ 10,142
Cumulative Number of Reported Claims | Claim	7,158
Fronting and Programs | Specialty Admitted Insurance | Accident year 2019
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 18,832
IBNR	$ 10,961
Cumulative Number of Reported Claims | Claim	5,695
Individual Risk Workers' Compensation | Specialty Admitted Insurance
Claims Development [Line Items]
Cumulative Number of Reported Claims | claim	4
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2010
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 27,099
IBNR	$ 698
Cumulative Number of Reported Claims | Claim	1,604
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2011
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 36,593
IBNR	$ 1,879
Cumulative Number of Reported Claims | Claim	1,814
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2012
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 28,186
IBNR	$ 1,090
Cumulative Number of Reported Claims | Claim	1,323
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2013
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 10,909
IBNR	$ 572
Cumulative Number of Reported Claims | Claim	540
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2014
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 12,704
IBNR	$ 423
Cumulative Number of Reported Claims | Claim	850
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2015
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 17,626
IBNR	$ 1,440
Cumulative Number of Reported Claims | Claim	975
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2016
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 15,800
IBNR	$ 3,245
Cumulative Number of Reported Claims | Claim	836
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2017
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 19,779
IBNR	$ 3,888
Cumulative Number of Reported Claims | Claim	1,092
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2018
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 16,288
IBNR	$ 3,495
Cumulative Number of Reported Claims | Claim	1,230
Individual Risk Workers' Compensation | Specialty Admitted Insurance | Accident year 2019
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 20,253
IBNR	$ 2,965
Cumulative Number of Reported Claims | Claim	1,482
Commercial Auto | Excess and Surplus Lines | Accident year 2013
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 1,277
IBNR	$ 1
Cumulative Number of Reported Claims | Claim	54
Commercial Auto | Excess and Surplus Lines | Accident year 2014
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 18,303
IBNR	$ 150
Cumulative Number of Reported Claims | Claim	7,763
Commercial Auto | Excess and Surplus Lines | Accident year 2015
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 36,636
IBNR	$ 337
Cumulative Number of Reported Claims | Claim	41,757
Commercial Auto | Excess and Surplus Lines | Accident year 2016
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 147,122
IBNR	$ 5,258
Cumulative Number of Reported Claims | Claim	89,003
Commercial Auto | Excess and Surplus Lines | Accident year 2017
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 272,421
IBNR	$ 11,473
Cumulative Number of Reported Claims | Claim	133,654
Commercial Auto | Excess and Surplus Lines | Accident year 2018
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 230,220
IBNR	$ 34,896
Cumulative Number of Reported Claims | Claim	95,889
Commercial Auto | Excess and Surplus Lines | Accident year 2019
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 262,306
IBNR	$ 167,476
Cumulative Number of Reported Claims | Claim	67,380
Excluding Commercial Auto | Excess and Surplus Lines
Claims Development [Line Items]
Cumulative Number of Reported Claims | claim	60
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2010
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 69,594
IBNR	$ 1,347
Cumulative Number of Reported Claims | Claim	1,429
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2011
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 105,173
IBNR	$ 2,380
Cumulative Number of Reported Claims | Claim	1,480
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2012
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 103,061
IBNR	$ 2,042
Cumulative Number of Reported Claims | Claim	1,806
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2013
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 82,732
IBNR	$ 5,493
Cumulative Number of Reported Claims | Claim	2,396
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2014
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 88,904
IBNR	$ 9,855
Cumulative Number of Reported Claims | Claim	2,162
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2015
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 103,688
IBNR	$ 7,681
Cumulative Number of Reported Claims | Claim	2,531
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2016
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 126,971
IBNR	$ 23,882
Cumulative Number of Reported Claims | Claim	2,933
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2017
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 132,136
IBNR	$ 53,525
Cumulative Number of Reported Claims | Claim	2,898
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2018
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 158,458
IBNR	$ 95,477
Cumulative Number of Reported Claims | Claim	3,935
Excluding Commercial Auto | Excess and Surplus Lines | Accident year 2019
Claims Development [Line Items]
Incurred Losses and Loss Adj Expenses	$ 214,653
IBNR	$ 178,172
Cumulative Number of Reported Claims | Claim	4,038

Reinsurance - Narrative (Detail

Reinsurance - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Reinsurance recoverable on unpaid losses	$ 668,045	$ 467,371	$ 302,524
Reinsurance recoverable on paid losses	$ 33,221	18,344
Percentage of reinsurance recoverables on unpaid losses for 3 largest reinsurers	46.30%
Prepaid reinsurance premiums ceded	$ 178,976	$ 112,498
Percentage of prepaid reinsurance premiums ceded for 3 largest reinsurers	41.30%
Largest reinsurer one
Ceded Credit Risk [Line Items]
Reinsurance recoverable on unpaid losses	$ 191,400
Prepaid reinsurance premiums ceded	27,200
Largest reinsurer two
Ceded Credit Risk [Line Items]
Reinsurance recoverable on unpaid losses	59,600
Prepaid reinsurance premiums ceded	24,500
Largest reinsurer three
Ceded Credit Risk [Line Items]
Reinsurance recoverable on unpaid losses	58,000
Prepaid reinsurance premiums ceded	$ 22,300

Reinsurance - Summary of Premiu

Reinsurance - Summary of Premiums Written, Premiums Earned, and Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Written premiums:
Direct	$ 1,305,948	$ 1,027,222	$ 843,719
Assumed	164,787	139,551	238,186
Ceded	(574,585)	(404,101)	(315,279)
Net written premiums	896,150	762,672	766,626
Earned premiums:
Direct	1,182,501	990,221	842,182
Assumed	150,330	208,192	173,472
Ceded	(509,085)	(383,015)	(274,545)
Net earned premiums	823,746	815,398	741,109
Losses and loss adjustment expenses:
Direct	953,548	769,490	626,318
Assumed	113,843	131,346	142,818
Ceded	(395,289)	(300,560)	(213,759)
Net	$ 672,102	$ 600,276	$ 555,377

Senior Debt (Details)

Senior Debt (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Aug. 02, 2017	May 26, 2004
2013 Facility
Line of Credit Facility [Line Items]
Current total capacity	$ 315,000,000
2013 Facility | Bank Holding Company
Line of Credit Facility [Line Items]
Commitment to lend	36,000,000
2013 Facility | Secured | JRG Re
Line of Credit Facility [Line Items]
Maximum borrowing capacity	102,500,000
Letters of credit outstanding	77,600,000
2013 Facility | Unsecured
Line of Credit Facility [Line Items]
Maximum borrowing capacity	212,500,000
Amount outstanding on line of credit	$ 133,300,000	$ 73,300,000
2013 Facility | LIBOR | Unsecured | JRG Re
Line of Credit Facility [Line Items]
Margin above LIBOR, percentage rate	1.375%
2017 Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 100,000,000
2017 Facility | Secured | JRG Re
Line of Credit Facility [Line Items]
Amount outstanding on line of credit	$ 21,900,000
2017 Facility | Unsecured
Line of Credit Facility [Line Items]
Amount outstanding on line of credit	$ 10,000,000
James River Group Senior Debt
Line of Credit Facility [Line Items]
Principal amount of Senior Debt				$ 15,000,000
James River Group Senior Debt | LIBOR
Line of Credit Facility [Line Items]
Margin above LIBOR, percentage rate				3.85%

Junior Subordinated Debt - Summ

Junior Subordinated Debt - Summary of Junior Subordinated Debt and Trust Preferred Securities (Details) - Junior Subordinated Debt $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
James River Capital Trust I
Debt Instrument [Line Items]
Issue date	May 26, 2004
Principal amount of Trust Preferred Securities	$ 7,000
Principal amount of Junior Subordinated Debt	7,217
Carrying amount of Junior Subordinated Debt net of repurchases	$ 7,217
Maturity date of Junior Subordinated Debt, unless accelerated earlier	May 24, 2034
Trust common stock	$ 217
Interest rate, per annum	Three-Month LIBOR plus 4.0%
James River Capital Trust II
Debt Instrument [Line Items]
Issue date	Dec. 15, 2004
Principal amount of Trust Preferred Securities	$ 15,000
Principal amount of Junior Subordinated Debt	15,464
Carrying amount of Junior Subordinated Debt net of repurchases	$ 15,464
Maturity date of Junior Subordinated Debt, unless accelerated earlier	Dec. 15, 2034
Trust common stock	$ 464
Interest rate, per annum	Three-Month LIBOR plus 3.4%
James River Capital Trust III
Debt Instrument [Line Items]
Issue date	Jun. 15, 2006
Principal amount of Trust Preferred Securities	$ 20,000
Principal amount of Junior Subordinated Debt	20,619
Carrying amount of Junior Subordinated Debt net of repurchases	$ 20,619
Maturity date of Junior Subordinated Debt, unless accelerated earlier	Jun. 15, 2036
Trust common stock	$ 619
Interest rate, per annum	Three-Month LIBOR plus 3.0%
James River Capital Trust IV
Debt Instrument [Line Items]
Issue date	Dec. 11, 2007
Principal amount of Trust Preferred Securities	$ 54,000
Principal amount of Junior Subordinated Debt	55,670
Carrying amount of Junior Subordinated Debt net of repurchases	$ 44,827
Maturity date of Junior Subordinated Debt, unless accelerated earlier	Dec. 15, 2037
Trust common stock	$ 1,670
Interest rate, per annum	Three-Month LIBOR plus 3.1%
Franklin Holdings II (Bermuda) Capital Trust I
Debt Instrument [Line Items]
Issue date	Jan. 10, 2008
Principal amount of Trust Preferred Securities	$ 30,000
Principal amount of Junior Subordinated Debt	30,928
Carrying amount of Junior Subordinated Debt net of repurchases	$ 15,928
Maturity date of Junior Subordinated Debt, unless accelerated earlier	Mar. 15, 2038
Trust common stock	$ 928
Interest rate, per annum	Three-Month LIBOR plus 4.0%

Junior Subordinated Debt - Narr

Junior Subordinated Debt - Narrative (Details) - Junior Subordinated Debt	12 Months Ended
	Dec. 31, 2019
Debt Instrument [Line Items]
Debt redemption percentage	100.00%
Deferred interest payment period (in years)	5 years

Capital Stock - Narrative (Deta

Capital Stock - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized	200,000,000	200,000,000
Common stock, par value (in dollars per share)	$ 0.0002	$ 0.0002
Common stock, shares issued	30,424,391	29,988,460
Undesignated preferred stock, shares authorized	20,000,000	20,000,000
Undesignated stock par value (in dollars per share)	$ 0.00125	$ 0.00125
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, shares outstanding	30,424,391	29,988,460	29,696,682
Common shares reserved for future issuance	4,325,963
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock unit dividend equivalents	$ 433,000	$ 391,000	$ 450,000
Dividends payable	$ 623,000	$ 557,000	$ 434,000

Capital Stock - Summary of Cash

Capital Stock - Summary of Cash Dividends Declared (Details) - USD ($)	Dec. 31, 2019	Nov. 05, 2019	Sep. 30, 2019	Jul. 30, 2019	Jun. 28, 2019	Apr. 30, 2019	Mar. 29, 2019	Feb. 20, 2019	Dec. 28, 2018	Nov. 07, 2018	Sep. 28, 2018	Aug. 01, 2018	Jun. 29, 2018	May 01, 2018	Mar. 30, 2018	Feb. 22, 2018	Dec. 28, 2017	Nov. 01, 2017	Sep. 29, 2017	Aug. 01, 2017	Jun. 30, 2017	May 02, 2017	Mar. 31, 2017	Feb. 14, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend declared per share (in dollars per share)		$ 0.30		$ 0.30		$ 0.30		$ 0.30		$ 0.30		$ 0.30		$ 0.30		$ 0.30				$ 0.30		$ 0.30		$ 0.30	$ 1.20	$ 1.20	$ 1.70
Total Amount	$ 9,228,656		$ 9,230,801		$ 9,204,804		$ 9,146,357		$ 9,088,542		$ 9,080,519		$ 9,066,023		$ 9,049,476				$ 8,943,279		$ 8,917,471		$ 8,878,147		$ 36,810,618	$ 36,284,560	$ 50,670,087
November 1, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend declared per share (in dollars per share)																		$ 0.30
Total Amount																	$ 8,974,196
November 1, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend declared per share (in dollars per share)																		$ 0.50
Total Amount																	$ 14,956,994

Equity Awards - Narrative (Deta

Equity Awards - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	0	0
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life of option (in years)	7 years
Total intrinsic value of options exercised	$ 8.2	$ 4.6	$ 20.4
Aggregate intrinsic value of options outstanding	7.1	9.4	18.5
Aggregate intrinsic value of options exercisable	$ 7.1	$ 8.5	$ 14.9
Fair value of shares used in calculation of intrinsic values (in dollars per share)	$ 41.21	$ 36.54	$ 40.01
Weighted-average remaining contractual life of options outstanding (in years)	2 years 10 months 24 days
Weighted-average remaining contractual life of options exercisable (in years)	2 years 9 months 18 days
Options granted	0	0	205,244
Weighted-average fair value of options granted (in dollars per share)			$ 8.21
Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Total fair value of shares vested	$ 5.3	$ 3.2	$ 5.5
Unrecognized share based compensation expense	$ 8.6
Weighted-average period of unrecognized share based compensation expense (in years)	1 year 8 months 12 days
RSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	1 year
RSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	5 years
2014 Long Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares available for issuance	4,171,150
Number of shares available for grant	1,575,359
2014 Non-Employee Director Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares available for issuance	150,000
Number of shares available for grant	108,594
Increase in number of common shares authorized for issuance				100,000
Non-employee directors | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	1 year

Equity Awards - Summary of Opti

Equity Awards - Summary of Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Granted (in shares)	0	0
Options
Shares
Beginning of year (in shares)	1,115,324	1,479,236	2,234,699
Granted (in shares)	0	0	205,244
Exercised (in shares)	(459,415)	(308,025)	(898,218)
Forfeited (in shares)	(12,058)	(55,887)	(62,489)
End of year (in shares)	643,851	1,115,324	1,479,236
Exercisable, end of year (in shares)	590,340	814,421	846,371
Weighted- Average Exercise Price
Beginning of year (in dollars per share)	$ 29.02	$ 27.81	$ 22.84
Granted (in dollars per share)	0	0	42.24
Exercised (in dollars per share)	26.87	22.01	18.53
Forfeited (in dollars per share)	36.84	35.69	30.80
End of year (in dollars per share)	30.41	29.02	27.81
Exercisable, end of year	$ 29.34	$ 26.46	$ 22.35

Equity Awards - Summary of Assu

Equity Awards - Summary of Assumptions for Options Granted (Details) - Options	12 Months Ended
	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.97%
Dividend yield	2.85%
Expected share price volatility	27.39%
Expected life (in years)	5 years

Equity Awards - Summary of RSU

Equity Awards - Summary of RSU Activity (Details) - RSUs - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Unvested, beginning of year (in shares)	300,142	178,882	196,800
Granted (in shares)	197,078	227,481	137,034
Vested (in shares)	(134,407)	(83,384)	(132,764)
Forfeited (in shares)	(22,445)	(22,837)	(22,188)
Unvested, end of year (in shares)	340,368	300,142	178,882
Weighted- Average Grant Date Fair Value
Unvested, beginning of year (in dollars per share)	$ 39.22	$ 37.93	$ 24.38
Granted (in dollars per share)	42.56	39.74	42.20
Vested (in dollars per share)	37.99	37.61	24.24
Forfeited (in dollars per share)	41.32	40.21	26.06
Unvested, end of year (in dollars per share)	$ 41.50	$ 39.22	$ 37.93

Equity Awards - Summary of Comp

Equity Awards - Summary of Compensation Expense and Related Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Share based compensation expense	$ 7,178	$ 6,228	$ 7,688
U.S. tax benefit on share based compensation expense	$ 872	$ 716	$ 2,093

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Examination [Line Items]
Percentage of dividend withholding tax	5.00%
Dividend distributions to intermediate holding company	$ 0	$ 0	$ 21,100,000
Remittance of dividend withholding tax			1,100,000
Deferred tax asset for additional discount			8,800,000
Deferred tax liability			$ 8,800,000
Transition provision expense		$ 1,100,000
Income tax expense recognized over next six years	5,700,000
Income tax expense recognized over next six years per year	$ 950,000
Federal statutory tax rates	21.00%	21.00%	35.00%
U.S. income before Federal income taxes	$ 70,700,000	$ 37,500,000	$ 50,100,000
Percentage of excise tax on reinsurance premiums paid	1.00%
Payment of federal excise taxes	$ 586,000	823,000	3,400,000
Excise taxes paid	$ 1,500,000	$ 2,100,000	$ 2,200,000
Bermuda
Income Tax Examination [Line Items]
Federal statutory tax rates	0.00%

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal income tax expense at applicable statutory rates	$ 14,843	$ 7,875	$ 17,541
Tax-exempt investment income	(230)	(272)	(586)
Dividends received deduction	(307)	(307)	(792)
Excess tax benefits on share based compensation	(1,099)	(567)	(2,114)
Effect of tax rate reduction on deferred tax liability	0	220	(3,498)
Other	99	145	(90)
Federal income tax expense	13,306	7,094	10,461
U.S. state income tax expense (benefit)	222	(86)	65
U.S. dividend withholding tax	0	0	1,053
Total income tax expense	$ 13,528	$ 7,008	$ 11,579

Income Taxes - Summary of Net D

Income Taxes - Summary of Net Deferred Tax Asset (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Accrued compensation expenses	$ 2,563	$ 2,456
Reserve for losses and loss adjustment expenses	12,286	7,482
Unearned premiums	8,226	5,711
Share based compensation	1,482	1,352
Allowance for doubtful accounts	1,188	829
Property and equipment	16	1,909
Other	1,974	1,903
Total deferred tax assets	27,735	21,642
Deferred tax liabilities:
Intangible assets	7,381	7,461
Net unrealized gains	5,792	887
Deferred policy acquisition costs	4,448	3,491
Equity method investments	9,316	8,582
Other	134	167
Total deferred tax liabilities	27,071	20,588
Net deferred tax assets	$ 664	$ 1,054

Other Operating Expenses and _3

Other Operating Expenses and Other Expenses - Summary of Other Operating Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Operating Expenses And Other Expenses [Abstract]
Amortization of policy acquisition costs	$ 83,893	$ 111,103	$ 116,001
Other underwriting expenses of the insurance segments	59,351	63,029	55,662
Other operating expenses of the Corporate and Other segment	27,664	26,903	25,330
Total	$ 170,908	$ 201,035	$ 196,993

Other Operating Expenses and _4

Other Operating Expenses and Other Expenses - Summary of Other Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Operating Expenses And Other Expenses [Abstract]
Employee severance	$ 1,055	$ 1,386	$ 147
Income on leased building the Company was previously deemed to own for accounting purposes	0	(623)	(248)
Legal and professional services related to secondary share offerings	0	337	535
Other	0	0	105
Impairment of intangible asset	0	200	0
Total	$ 1,055	$ 1,300	$ 539

Employee Benefits (Details)

Employee Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Maximum matching employer contribution	6.00%
Expense associated with Savings Plans	$ 3.2	$ 2.9	$ 2.5

Commitments and Contingent Li_2

Commitments and Contingent Liabilities - Narrative (Details)	Dec. 31, 2019USD ($)letter_of_credit_facility	Dec. 31, 2018USD ($)
Contingent Liabilities [Line Items]
Amount of collateral held	$ 1,199,164,000	$ 0
JRG Reinsurance Company, Ltd.
Contingent Liabilities [Line Items]
Letter of credit facilities | letter_of_credit_facility	3
Total amount deposited in trust accounts	$ 283,200,000
JRG Reinsurance Company, Ltd. | Letter of credit 75 million
Contingent Liabilities [Line Items]
Letters of credit facility, amount	75,000,000
Amount of letters of credit issued	22,700,000
Assets deposited for securing letters of credit	35,900,000
JRG Reinsurance Company, Ltd. | 2013 Facility
Contingent Liabilities [Line Items]
Amount of letters of credit issued	77,600,000
Assets deposited for securing letters of credit	93,900,000
JRG Reinsurance Company, Ltd. | 2017 Facility
Contingent Liabilities [Line Items]
Amount of letters of credit issued	21,900,000
Assets deposited for securing letters of credit	51,500,000
Raiser
Contingent Liabilities [Line Items]
Amount of collateral held	$ 1,199,200,000

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) - Summary of Components of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gains (losses) arising during the period, before U.S. income taxes	$ 51,381	$ (23,201)	$ 11,091
U.S. income taxes	(3,510)	483	(2,374)
Unrealized gains (losses) arising during the period, net of U.S. income taxes	47,871	(22,718)	8,717
Less reclassification adjustment:
Net realized investment gains (losses)	1,081	(554)	(835)
U.S. income taxes	(152)	39	333
Reclassification adjustment for investment gains (losses) realized in net income	929	(515)	(502)
Other comprehensive income (loss)	$ 46,942	$ (22,203)	$ 9,219

Other Comprehensive Income (L_4

Other Comprehensive Income (Loss) - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net realized investment gains (losses)	$ 1,081	$ (554)	$ (835)
Bank loan participations realized investment gains (losses)	(10,056)	1,113	(1,150)
Changes in fair values of equity securities	$ 6,257	$ (5,970)	$ 0

Segment Information - Narrative

Segment Information - Narrative (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019USD ($)companyinsuredagencybroker	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)companyinsuredUnderwriting_divisionagencybrokerSegment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment									4
Fee income									$ 9,100	$ 13,900	$ 17,000
Number of underwriting divisions | Underwriting_division									15
Gross written premiums	$ 375,170	$ 388,228	$ 380,003	$ 327,334	$ 295,310	$ 279,969	$ 293,378	$ 298,116	$ 1,470,735	1,166,773	1,081,905
Excess and Surplus Lines
Segment Reporting Information [Line Items]
Number of brokers | broker	3								3
Number of underwriting divisions | Underwriting_division									13
Gross written premiums									$ 922,320	656,538	530,120
Number of insured | insured	1								1
Excess and Surplus Lines | Broker one
Segment Reporting Information [Line Items]
Gross written premiums									$ 472,600
Consolidated gross written premiums percentage									32.10%
Gross written premiums percentage									51.20%
Excess and Surplus Lines | Broker two
Segment Reporting Information [Line Items]
Gross written premiums									$ 115,200
Consolidated gross written premiums percentage									7.80%
Gross written premiums percentage									12.50%
Excess and Surplus Lines | Broker three
Segment Reporting Information [Line Items]
Gross written premiums									$ 98,600
Consolidated gross written premiums percentage									6.70%
Gross written premiums percentage									10.70%
Excess and Surplus Lines | Insured one
Segment Reporting Information [Line Items]
Fee income									$ 9,100
Gross written premiums									$ 374,200
Consolidated gross written premiums percentage									25.40%
Gross written premiums percentage									40.60%
Specialty Admitted Insurance
Segment Reporting Information [Line Items]
Number of underwriting divisions | Underwriting_division									1
Gross written premiums									$ 387,642	374,346	316,430
Number of agencies | agency	2								2
Specialty Admitted Insurance | Agency one
Segment Reporting Information [Line Items]
Gross written premiums									$ 146,500
Consolidated gross written premiums percentage									10.00%
Gross written premiums percentage									37.80%
Specialty Admitted Insurance | Agency two
Segment Reporting Information [Line Items]
Gross written premiums									$ 53,200
Consolidated gross written premiums percentage									3.60%
Gross written premiums percentage									13.70%
Casualty Reinsurance
Segment Reporting Information [Line Items]
Number of brokers | broker	4								4
Number of underwriting divisions | Underwriting_division									1
Gross written premiums									$ 160,773	$ 135,889	$ 235,355
Number of unaffiliated ceding companies | company	3								3
Casualty Reinsurance | Broker one
Segment Reporting Information [Line Items]
Gross written premiums									$ 53,700
Consolidated gross written premiums percentage									3.70%
Gross written premiums percentage									33.40%
Casualty Reinsurance | Broker two
Segment Reporting Information [Line Items]
Gross written premiums									$ 45,100
Consolidated gross written premiums percentage									3.10%
Gross written premiums percentage									28.10%
Casualty Reinsurance | Broker three
Segment Reporting Information [Line Items]
Gross written premiums									$ 42,400
Consolidated gross written premiums percentage									2.90%
Gross written premiums percentage									26.40%
Casualty Reinsurance | Broker four
Segment Reporting Information [Line Items]
Gross written premiums									$ 16,700
Consolidated gross written premiums percentage									1.10%
Gross written premiums percentage									10.40%
Casualty Reinsurance | Unaffiliated ceding company one
Segment Reporting Information [Line Items]
Gross written premiums									$ 96,400
Consolidated gross written premiums percentage									6.60%
Gross written premiums percentage									59.90%
Casualty Reinsurance | Unaffiliated ceding company two
Segment Reporting Information [Line Items]
Gross written premiums									$ 30,700
Consolidated gross written premiums percentage									2.10%
Gross written premiums percentage									19.10%
Casualty Reinsurance | Unaffiliated ceding company three
Segment Reporting Information [Line Items]
Gross written premiums									$ 22,600
Consolidated gross written premiums percentage									1.50%
Gross written premiums percentage									14.00%

Segment Information - Schedule

Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Gross written premiums	$ 375,170	$ 388,228	$ 380,003	$ 327,334	$ 295,310	$ 279,969	$ 293,378	$ 298,116	$ 1,470,735	$ 1,166,773	$ 1,081,905
Net earned premiums									823,746	815,398	741,109
Segment revenues	241,150	$ 231,474	$ 220,374	$ 214,127	214,522	$ 224,692	$ 228,041	$ 218,344	907,125	885,599	817,625
Net investment income									75,652	61,256	61,119
Interest expense									10,596	11,553	8,974
Underwriting profit (loss) of operating segments									17,909	54,909	31,094
Goodwill	181,831				181,831				181,831	181,831	181,831
Segment assets	5,024,405				3,136,776				5,024,405	3,136,776	2,756,695
Excess and Surplus Lines
Segment Reporting Information [Line Items]
Gross written premiums									922,320	656,538	530,120
Net earned premiums									625,528	555,684	463,521
Segment revenues									657,501	580,785	493,853
Net investment income									21,358	14,456	15,014
Interest expense									0	0	0
Underwriting profit (loss) of operating segments									19,157	42,834	29,693
Goodwill	181,831				181,831				181,831	181,831	181,831
Segment assets	2,481,934				972,111				2,481,934	972,111	843,486
Specialty Admitted Insurance
Segment Reporting Information [Line Items]
Gross written premiums									387,642	374,346	316,430
Net earned premiums									54,338	55,146	68,110
Segment revenues									61,241	56,717	70,366
Net investment income									3,802	3,262	2,532
Interest expense									0	0	0
Underwriting profit (loss) of operating segments									5,913	6,972	3,166
Goodwill	0				0				0	0	0
Segment assets	786,433				633,689				786,433	633,689	439,416
Casualty Reinsurance
Segment Reporting Information [Line Items]
Gross written premiums									160,773	135,889	235,355
Net earned premiums									143,880	204,568	209,478
Segment revenues									183,700	243,178	240,751
Net investment income									46,325	38,838	31,507
Interest expense									0	0	0
Underwriting profit (loss) of operating segments									(7,161)	5,103	(1,765)
Goodwill	0				0				0	0	0
Segment assets	1,699,473				1,453,754				1,699,473	1,453,754	1,379,866
Corporate and other segment
Segment Reporting Information [Line Items]
Gross written premiums									0	0	0
Net earned premiums									0	0	0
Segment revenues									4,683	4,919	12,655
Net investment income									4,167	4,700	12,066
Interest expense									10,596	11,553	8,974
Underwriting profit (loss) of operating segments									0	0	0
Goodwill	0				0				0	0	0
Segment assets	$ 56,565				$ 77,222				$ 56,565	$ 77,222	$ 93,927

Segment Information - Reconcili

Segment Information - Reconciliation of Underwriting Profit (Loss) of Insurance Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Underwriting profit (loss) of operating segments	$ 17,909	$ 54,909	$ 31,094
Other operating expenses	(27,664)	(26,903)	(25,330)
Underwriting profit	(9,755)	28,006	5,764
Net investment income	75,652	61,256	61,119
Net realized investment (losses) gains	(2,919)	(5,479)	(1,989)
Other income	1,137	505	361
Other expenses	(1,055)	(1,300)	(539)
Interest expense	(10,596)	(11,553)	(8,974)
Amortization of intangible assets	(597)	(597)	(597)
Income before income taxes	51,867	70,838	55,145
Excess and Surplus Lines
Segment Reporting Information [Line Items]
Underwriting profit (loss) of operating segments	19,157	42,834	29,693
Net investment income	21,358	14,456	15,014
Interest expense	0	0	0
Amortization of intangible assets	(362)	(362)	(362)
Specialty Admitted Insurance
Segment Reporting Information [Line Items]
Underwriting profit (loss) of operating segments	5,913	6,972	3,166
Net investment income	3,802	3,262	2,532
Interest expense	0	0	0
Amortization of intangible assets	(235)	(235)	(235)
Casualty Reinsurance
Segment Reporting Information [Line Items]
Underwriting profit (loss) of operating segments	(7,161)	5,103	(1,765)
Net investment income	46,325	38,838	31,507
Interest expense	0	0	0
Corporate and other segment
Segment Reporting Information [Line Items]
Underwriting profit (loss) of operating segments	0	0	0
Net investment income	4,167	4,700	12,066
Interest expense	$ (10,596)	$ (11,553)	$ (8,974)

Segment Information - Gross Wri

Segment Information - Gross Written Premiums (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total gross written premiums	$ 375,170	$ 388,228	$ 380,003	$ 327,334	$ 295,310	$ 279,969	$ 293,378	$ 298,116	$ 1,470,735	$ 1,166,773	$ 1,081,905
Excess and Surplus Lines
Segment Reporting Information [Line Items]
Total gross written premiums									922,320	656,538	530,120
Excess and Surplus Lines | Commercial Auto
Segment Reporting Information [Line Items]
Total gross written premiums									405,565	322,126	247,960
Excess and Surplus Lines | Excess Casualty
Segment Reporting Information [Line Items]
Total gross written premiums									118,954	66,452	51,160
Excess and Surplus Lines | General Casualty
Segment Reporting Information [Line Items]
Total gross written premiums									115,832	54,127	38,097
Excess and Surplus Lines | Manufacturers and Contractors
Segment Reporting Information [Line Items]
Total gross written premiums									105,096	79,160	85,719
Excess and Surplus Lines | Energy
Segment Reporting Information [Line Items]
Total gross written premiums									45,442	33,942	29,704
Excess and Surplus Lines | Excess Property
Segment Reporting Information [Line Items]
Total gross written premiums									31,606	16,963	14,447
Excess and Surplus Lines | Allied Health
Segment Reporting Information [Line Items]
Total gross written premiums									26,713	30,450	19,181
Excess and Surplus Lines | Life Sciences
Segment Reporting Information [Line Items]
Total gross written premiums									24,462	16,636	12,981
Excess and Surplus Lines | Small Business
Segment Reporting Information [Line Items]
Total gross written premiums									19,725	14,808	11,307
Excess and Surplus Lines | Environmental
Segment Reporting Information [Line Items]
Total gross written premiums									16,539	10,499	7,920
Excess and Surplus Lines | Professional Liability
Segment Reporting Information [Line Items]
Total gross written premiums									6,441	5,916	6,326
Excess and Surplus Lines | Sports and Entertainment
Segment Reporting Information [Line Items]
Total gross written premiums									4,212	3,685	3,021
Excess and Surplus Lines | Medical Professionals
Segment Reporting Information [Line Items]
Total gross written premiums									1,733	1,774	2,297
Specialty Admitted Insurance
Segment Reporting Information [Line Items]
Total gross written premiums									387,642	374,346	316,430
Casualty Reinsurance
Segment Reporting Information [Line Items]
Total gross written premiums									$ 160,773	$ 135,889	$ 235,355

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	$ 1,433,626	$ 1,184,202
Equity securities:
Equity securities	80,735	78,385
Fixed maturity securities:
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	1,433,626	1,184,202
State and municipal
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	167,101	149,295
Residential mortgage-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	264,146	204,109
Corporate
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	632,221	524,768
Commercial mortgage and asset-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	252,457	197,025
U.S. Treasury securities and obligations guaranteed by the U.S. government
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	115,667	107,193
Redeemable preferred stock
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	2,034	1,812
Recurring basis
Equity securities:
Short-term investments	156,925	81,966
Recurring basis | Fixed maturity securities:
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	1,433,626	1,184,202
Recurring basis | State and municipal
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	167,101	149,295
Recurring basis | Residential mortgage-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	264,146	204,109
Recurring basis | Corporate
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	632,221	524,768
Recurring basis | Commercial mortgage and asset-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	252,457	197,025
Recurring basis | U.S. Treasury securities and obligations guaranteed by the U.S. government
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	115,667	107,193
Recurring basis | Redeemable preferred stock
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	2,034	1,812
Recurring basis | Equity securities
Equity securities:
Equity securities	80,735	78,385
Recurring basis | Preferred stock
Equity securities:
Equity securities	62,747	60,740
Recurring basis | Common stock
Equity securities:
Equity securities	17,988	17,645
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1
Equity securities:
Short-term investments	0	1,250
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Fixed maturity securities:
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	115,173	106,651
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | State and municipal
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Residential mortgage-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Corporate
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Commercial mortgage and asset-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | U.S. Treasury securities and obligations guaranteed by the U.S. government
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	115,173	106,651
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Redeemable preferred stock
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Equity securities
Equity securities:
Equity securities	14,669	16,674
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Preferred stock
Equity securities:
Equity securities	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Common stock
Equity securities:
Equity securities	14,669	16,674
Recurring basis | Significant Other Observable Inputs Level 2
Equity securities:
Short-term investments	156,925	80,716
Recurring basis | Significant Other Observable Inputs Level 2 | Fixed maturity securities:
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	1,318,453	1,073,323
Recurring basis | Significant Other Observable Inputs Level 2 | State and municipal
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	167,101	149,295
Recurring basis | Significant Other Observable Inputs Level 2 | Residential mortgage-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	264,146	204,109
Recurring basis | Significant Other Observable Inputs Level 2 | Corporate
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	632,221	524,768
Recurring basis | Significant Other Observable Inputs Level 2 | Commercial mortgage and asset-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	252,457	192,797
Recurring basis | Significant Other Observable Inputs Level 2 | U.S. Treasury securities and obligations guaranteed by the U.S. government
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	494	542
Recurring basis | Significant Other Observable Inputs Level 2 | Redeemable preferred stock
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	2,034	1,812
Recurring basis | Significant Other Observable Inputs Level 2 | Equity securities
Equity securities:
Equity securities	66,023	61,497
Recurring basis | Significant Other Observable Inputs Level 2 | Preferred stock
Equity securities:
Equity securities	62,747	60,740
Recurring basis | Significant Other Observable Inputs Level 2 | Common stock
Equity securities:
Equity securities	3,276	757
Recurring basis | Significant Unobservable Inputs Level 3
Equity securities:
Short-term investments	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Fixed maturity securities:
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	4,228
Recurring basis | Significant Unobservable Inputs Level 3 | State and municipal
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Residential mortgage-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Corporate
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Commercial mortgage and asset-backed
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale		4,228	$ 4,700
Recurring basis | Significant Unobservable Inputs Level 3 | U.S. Treasury securities and obligations guaranteed by the U.S. government
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Redeemable preferred stock
Fixed maturity securities, available-for-sale:
Fixed maturity securities, available-for-sale	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Equity securities
Equity securities:
Equity securities	43	214
Recurring basis | Significant Unobservable Inputs Level 3 | Preferred stock
Equity securities:
Equity securities	$ 0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Common stock
Equity securities:
Equity securities		$ 214

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Available-for-Sale Fixed Maturity Securities Measured at Fair Value on a Recurring Basis (Details) - Available-for-sale fixed maturity and equity securities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 4,442	$ 4,680	$ 5,000
Transfers in to Level 3	3,010	0	0
Transfers out of Level 3	(7,238)	0	0
Purchases		214	0
Sales	0	0	0
Maturities and calls		(452)	(320)
Amortization of discount	0	0	0
Total gains or losses (realized/unrealized) - Included in earnings	(171)	0	0
Total gains or losses (realized/unrealized) - Included in other comprehensive income	0	0	0
Ending balance	$ 43	$ 4,442	$ 4,680

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale	$ 1,433,626	$ 1,184,202
Principal payment received	128,809	129,139	$ 121,890
Equity securities	80,735	78,385
Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired bank loan participations held for investment	6,949	0
Significant Unobservable Inputs Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal payment received	456
Significant Unobservable Inputs Level 3 | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired bank loan participations held for investment	6,949	0
Commercial mortgage and asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale	252,457	197,025
Commercial mortgage and asset-backed | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale	252,457	197,025
Commercial mortgage and asset-backed | Significant Unobservable Inputs Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale		4,228	$ 4,700
Equity securities | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	80,735	78,385
Equity securities | Significant Unobservable Inputs Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	$ 43	$ 214

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Assets Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring basis - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	$ 6,949	$ 0
Quoted Prices in Active Markets for Identical Assets Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	0	0
Significant Other Observable Inputs Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	0	0
Significant Unobservable Inputs Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	$ 6,949	$ 0

Fair Value Measurements - Sum_4

Fair Value Measurements - Summary of the Carrying Value and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
Fixed maturity securities, available-for-sale	$ 1,433,626	$ 1,184,202
Equity securities	80,735	78,385
Bank loan participations held-for-investment	260,864	260,972
Cash and cash equivalents	206,912	172,457
Restricted cash equivalents	1,199,164	0
Short-term investments	156,925	81,966
Liabilities
Senior debt	158,300	118,300
Carrying Value
Assets
Fixed maturity securities, available-for-sale	1,433,626	1,184,202
Equity securities	80,735	78,385
Bank loan participations held-for-investment	260,864	260,972
Cash and cash equivalents	206,912	172,457
Restricted cash equivalents	1,199,164	0
Short-term investments	156,925	81,966
Other invested assets – notes receivable	13,250	13,250
Liabilities
Senior debt	158,300	118,300
Junior subordinated debt	104,055	104,055
Fair Value
Assets
Fixed maturity securities, available-for-sale	1,433,626	1,184,202
Equity securities	80,735	78,385
Bank loan participations held-for-investment	252,423	250,697
Cash and cash equivalents	206,912	172,457
Restricted cash equivalents	1,199,164	0
Short-term investments	156,925	81,966
Other invested assets – notes receivable	18,756	18,687
Liabilities
Senior debt	158,043	118,317
Junior subordinated debt	$ 122,193	$ 117,057

Statutory Matters - Schedule of

Statutory Matters - Schedule of Statutory Accounting (Details) - UNITED STATES - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices [Line Items]
Statutory net income	$ 3,586	$ 6,770	$ 31,881
Statutory capital and surplus	266,715	241,668	219,132
Minimum required statutory capital and surplus	$ 111,208	$ 24,850	$ 25,000

Statutory Matters - Narrative (

Statutory Matters - Narrative (Details) - Casualty Reinsurance - BERMUDA - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices [Line Items]
Minimum statutory solvency margin	$ 161.4	$ 161.3
Actual statutory capital and surplus	502.6	439.4
Statutory net income	$ 53.2	86.5	$ 20.1
Combined ECR		$ 283.6
Minimum liquidity ratio	75.00%

Dividend Restrictions (Details)

Dividend Restrictions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statutory Accounting Practices [Line Items]
Percentage of dividend withholding tax for distributions	5.00%
Percentage of dividend distribution tax	30.00%
Retained earnings	$ 89,586	$ 79,753
UNITED STATES
Statutory Accounting Practices [Line Items]
Dividend limitations percentage of statutory surplus	10.00%
Maximum amount of dividends available without regulatory approval	$ 26,700
BERMUDA
Statutory Accounting Practices [Line Items]
Maximum amount of dividends and return of capital available	$ 125,600

Other Related Party Transacti_2

Other Related Party Transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Minority interest in partnership
Related Party Transaction [Line Items]
Operating costs under lease	$ 2,100,000	$ 2,600,000	$ 2,400,000
Independent Directors | Consulting Agreement
Related Party Transaction [Line Items]
Investment and other business consulting services fees			37,500
Chief Executive Officer
Related Party Transaction [Line Items]
Total fees paid for the use of plane	$ 0	$ 123,000	$ 314,000

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares	Feb. 19, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
RSUs
Subsequent Event [Line Items]
Number of awards granted		197,078	227,481	137,034
Fair value on grant date		$ 42.56	$ 39.74	$ 42.20
Vesting period (in years)		3 years
RSUs | Minimum
Subsequent Event [Line Items]
Vesting period (in years)		1 year
RSUs | Maximum
Subsequent Event [Line Items]
Vesting period (in years)		5 years
Subsequent event
Subsequent Event [Line Items]
Dividends payable, per common share	$ 0.30
Subsequent event | 2014 Long Term Incentive Plan | RSUs
Subsequent Event [Line Items]
Number of awards granted	179,016
Fair value on grant date	$ 43.55
Subsequent event | 2014 Long Term Incentive Plan | RSUs | Minimum
Subsequent Event [Line Items]
Vesting period (in years)	1 year
Subsequent event | 2014 Long Term Incentive Plan | RSUs | Maximum
Subsequent Event [Line Items]
Vesting period (in years)	3 years

Unaudited Selected Quarterly _3

Unaudited Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Gross written premiums	$ 375,170	$ 388,228	$ 380,003	$ 327,334	$ 295,310	$ 279,969	$ 293,378	$ 298,116	$ 1,470,735	$ 1,166,773	$ 1,081,905
Total revenues	241,150	231,474	220,374	214,127	214,522	224,692	228,041	218,344	907,125	885,599	817,625
Net income (loss)	20,471	(25,167)	20,307	22,728	11,632	19,581	16,984	15,633	38,339	63,830	43,566
Comprehensive income (loss)	$ 16,964	$ (15,710)	$ 41,039	$ 42,988	$ 18,923	$ 15,192	$ 10,426	$ (2,914)	$ 85,281	$ 41,627	$ 52,785
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.67	$ (0.83)	$ 0.67	$ 0.76	$ 0.39	$ 0.65	$ 0.57	$ 0.53	$ 1.27	$ 2.14	$ 1.48
Diluted (in dollars per share)	$ 0.67	$ (0.83)	$ 0.66	$ 0.75	$ 0.38	$ 0.64	$ 0.56	$ 0.52	$ 1.25	$ 2.11	$ 1.44

SCHEDULE I - Summary of Inves_2

SCHEDULE I - Summary of Investments - Other than Investments in Related Parties (Details) $ in Thousands	Dec. 31, 2019USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amount at which shown on Balance Sheet	$ 1,948,891
Bank loan participations, held-for-investment, net of allowance
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	260,864
Fair Value	252,423
Amount at which shown on Balance Sheet	260,864
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	156,925
Fair Value	156,925
Amount at which shown on Balance Sheet	156,925
Other invested assets
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amount at which shown on Balance Sheet	16,741
Available-for-sale Securities | Fixed maturity securities:
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	1,398,533
Fair Value	1,433,626
Amount at which shown on Balance Sheet	1,433,626
Available-for-sale Securities | State and municipal
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	159,894
Fair Value	167,101
Amount at which shown on Balance Sheet	167,101
Available-for-sale Securities | Residential mortgage-backed
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	261,524
Fair Value	264,146
Amount at which shown on Balance Sheet	264,146
Available-for-sale Securities | Corporate
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	611,304
Fair Value	632,221
Amount at which shown on Balance Sheet	632,221
Available-for-sale Securities | Commercial mortgage and asset-backed
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	249,309
Fair Value	252,457
Amount at which shown on Balance Sheet	252,457
Available-for-sale Securities | U.S. Treasury securities and obligations guaranteed by the U.S. government
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	114,477
Fair Value	115,667
Amount at which shown on Balance Sheet	115,667
Available-for-sale Securities | Redeemable preferred stock
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	2,025
Fair Value	2,034
Amount at which shown on Balance Sheet	2,034
Available-for-sale Securities | Equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	73,244
Fair Value	80,735
Amount at which shown on Balance Sheet	80,735
Available-for-sale Securities | Preferred stock
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	52,557
Fair Value	62,747
Amount at which shown on Balance Sheet	62,747
Available-for-sale Securities | Common stock
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	20,687
Fair Value	17,988
Amount at which shown on Balance Sheet	$ 17,988

SCHEDULE II - Condensed Finan_2

SCHEDULE II - Condensed Financial Information of Registrant (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets [Abstract]
Cash and cash equivalents	$ 206,912	$ 172,457
Other assets	80,227	94,379
Total assets	5,024,405	3,136,776	$ 2,756,695
Liabilities:
Accrued expenses	58,416	51,792
Senior debt	158,300	118,300
Junior subordinated debt	104,055	104,055
Other liabilities	46,464	41,879
Total liabilities	4,245,824	2,427,535
Commitments and contingent liabilities
Shareholders’ equity:
Class A common shares	6	6
Additional paid-in capital	657,875	645,310
Retained earnings	89,586	79,753
Accumulated other comprehensive income (loss)	31,114	(15,828)
Total shareholders’ equity	778,581	709,241	694,699	$ 693,221
Total liabilities and shareholders’ equity	5,024,405	3,136,776
Parent Company
Assets [Abstract]
Cash and cash equivalents	1,521	240	$ 2,849	$ 2,969
Investment in subsidiaries	987,221	882,407
Due from subsidiaries	7,371	5,775
Other assets	2,842	1,579
Total assets	998,955	890,001
Liabilities:
Accrued expenses	1,592	2,322
Senior debt	143,300	103,300
Junior subordinated debt	15,928	15,928
Notes payable to subsidiary	40,000	40,000
Due to subsidiaries	18,822	18,605
Other liabilities	732	605
Total liabilities	220,374	180,760
Commitments and contingent liabilities
Shareholders’ equity:
Class A common shares	6	6
Additional paid-in capital	657,875	645,310
Retained earnings	89,586	79,753
Accumulated other comprehensive income (loss)	31,114	(15,828)
Total shareholders’ equity	778,581	709,241
Total liabilities and shareholders’ equity	$ 998,955	$ 890,001

SCHEDULE II - Condensed Finan_3

SCHEDULE II - Condensed Financial Information of Registrant (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Other income									$ 10,646	$ 14,424	$ 17,386
Total revenues	$ 241,150	$ 231,474	$ 220,374	$ 214,127	$ 214,522	$ 224,692	$ 228,041	$ 218,344	907,125	885,599	817,625
Expenses:
Other operating expenses									170,908	201,035	196,993
Other expenses									1,055	1,300	539
Interest expense									10,596	11,553	8,974
Total expenses									855,258	814,761	762,480
Loss before equity in net income of subsidiaries									51,867	70,838	55,145
Equity in net income of subsidiaries									4,598	3,540	13,209
Net income	20,471	(25,167)	20,307	22,728	11,632	19,581	16,984	15,633	38,339	63,830	43,566
Other comprehensive (loss) income:
Equity in other comprehensive earnings (losses) of subsidiaries									46,942	(22,203)	9,219
Total comprehensive income	$ 16,964	$ (15,710)	$ 41,039	$ 42,988	$ 18,923	$ 15,192	$ 10,426	$ (2,914)	85,281	41,627	52,785
Parent Company
Revenues:
Other income									61	58	49
Total revenues									61	58	49
Expenses:
Other operating expenses									14,267	13,768	10,375
Other expenses									0	337	640
Interest expense									5,047	5,122	4,130
Total expenses									19,314	19,227	15,145
Loss before equity in net income of subsidiaries									(19,253)	(19,169)	(15,096)
Equity in net income of subsidiaries									57,592	82,999	58,662
Net income									38,339	63,830	43,566
Other comprehensive (loss) income:
Equity in other comprehensive earnings (losses) of subsidiaries									46,942	(22,203)	9,219
Total comprehensive income									$ 85,281	$ 41,627	$ 52,785

SCHEDULE II - Condensed Finan_4

SCHEDULE II - Condensed Financial Information of Registrant (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 20,471	$ (25,167)	$ 20,307	$ 22,728	$ 11,632	$ 19,581	$ 16,984	$ 15,633	$ 38,339	$ 63,830	$ 43,566
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provision for depreciation and amortization									4,063	4,215	2,123
Share based compensation expense									7,178	6,228	7,688
Net cash provided by operating activities									1,489,022	290,028	207,816
Investing activities
Net cash used in investing activities									(263,359)	(266,772)	(104,741)
Financing activities
Dividends paid									(36,720)	(36,123)	(50,832)
Senior debt issuance									60,000	20,000	10,000
Senior debt repayments									(20,000)	0	0
Issuances of common shares under equity incentive plans									8,286	5,172	1,708
Common share repurchases									(2,899)	(2,239)	(9,448)
Net cash provided by (used in) financing activities									7,956	(14,294)	(49,364)
Cash and cash equivalents at beginning of year				172,457					172,457
Cash and cash equivalents at end of year	206,912				172,457				206,912	172,457
Supplemental information
Interest paid									12,354	11,269	8,909
Parent Company
Operating activities
Net income									38,339	63,830	43,566
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provision for depreciation and amortization									182	176	176
Share based compensation expense									7,178	6,228	7,688
Equity in undistributed earnings of subsidiaries									(49,592)	6,000	(23,662)
Changes in operating assets and liabilities:									(2,782)	(5,653)	684
Net cash provided by operating activities									(6,675)	70,581	28,452
Investing activities
Dividends from subsidiaries									0	0	20,000
Net cash used in investing activities									0	0	20,000
Financing activities
Dividends paid									(36,720)	(36,123)	(50,832)
Senior debt issuance									60,000	20,000	10,000
Senior debt repayments									(20,000)	0	0
Subsidiary note repayments									0	(60,000)	0
Debt issue costs paid									(711)	0	0
Issuances of common shares under equity incentive plans									8,286	5,172	1,708
Common share repurchases									(2,899)	(2,239)	(9,448)
Net cash provided by (used in) financing activities									7,956	(73,190)	(48,572)
Increase in cash and cash equivalents									1,281	(2,609)	(120)
Cash and cash equivalents at beginning of year				$ 240				$ 2,849	240	2,849	2,969
Cash and cash equivalents at end of year	$ 1,521				$ 240				1,521	240	2,849
Supplemental information
Interest paid									$ 5,710	$ 5,052	$ 4,612

SCHEDULE II - Condensed Finan_5

SCHEDULE II - Condensed Financial Information of Registrant - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Assets	$ (5,024,405)		$ (3,136,776)		$ (2,756,695)
Liabilities	(4,245,824)		$ (2,427,535)
Right-of-use assets	17,200
Lease liabilities	$ 18,232
ASU 2016-02
Condensed Financial Statements, Captions [Line Items]
Assets		$ 22,600
Liabilities		30,900
Cumulative effect of adoption of ASU		8,280
Right-of-use assets		17,200
Lease liabilities		17,800
ASU 2016-01
Condensed Financial Statements, Captions [Line Items]
Cumulative effect of adoption of ASU				$ 0
ASU 2018-02
Condensed Financial Statements, Captions [Line Items]
Cumulative effect of adoption of ASU				0
Retained Earnings | ASU 2016-02
Condensed Financial Statements, Captions [Line Items]
Cumulative effect of adoption of ASU		$ 8,280
Retained Earnings | ASU 2016-01
Condensed Financial Statements, Captions [Line Items]
Cumulative effect of adoption of ASU				4,682
Retained Earnings | ASU 2018-02
Condensed Financial Statements, Captions [Line Items]
Cumulative effect of adoption of ASU				$ (711)

SCHEDULE III - Supplementary _2

SCHEDULE III - Supplementary Insurance Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	$ 62,006	$ 54,450	$ 72,365
Reserve for Losses and Loss Adjustment Expenses	2,045,506	1,661,459	1,292,349
Unearned Premiums	524,377	386,473	418,114
Net Earned Premiums	823,746	815,398	741,109
Net Investment Income	75,652	61,256	61,119
Losses and Loss Adjustment Expenses	672,102	600,276	555,377
Amortization of Policy Acquisition Costs	83,893	111,103	116,001
Other Operating Expenses	170,908	201,035	196,993
Net Written Premiums	896,150	762,672	766,626
Excess and Surplus Lines
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	24,428	16,736	17,050
Reserve for Losses and Loss Adjustment Expenses	1,245,581	960,562	759,043
Unearned Premiums	267,924	175,231	149,047
Net Earned Premiums	625,528	555,684	463,521
Net Investment Income	21,358	14,456	15,014
Losses and Loss Adjustment Expenses	528,133	437,904	371,717
Amortization of Policy Acquisition Costs	49,720	48,299	45,158
Other Operating Expenses	87,326	88,865	79,136
Net Written Premiums	685,814	571,098	469,891
Specialty Admitted Insurance
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	(2,902)	(1,829)	(725)
Reserve for Losses and Loss Adjustment Expenses	511,027	426,315	271,446
Unearned Premiums	115,606	84,659	73,649
Net Earned Premiums	54,338	55,146	68,110
Net Investment Income	3,802	3,262	2,532
Losses and Loss Adjustment Expenses	34,860	32,623	44,863
Amortization of Policy Acquisition Costs	(3,560)	(1,792)	5,605
Other Operating Expenses	13,986	15,551	20,081
Net Written Premiums	58,637	55,840	60,957
Casualty Reinsurance
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	40,480	39,543	56,040
Reserve for Losses and Loss Adjustment Expenses	288,898	274,582	261,860
Unearned Premiums	140,847	126,583	195,418
Net Earned Premiums	143,880	204,568	209,478
Net Investment Income	46,325	38,838	31,507
Losses and Loss Adjustment Expenses	109,109	129,749	138,797
Amortization of Policy Acquisition Costs	37,733	64,596	65,238
Other Operating Expenses	41,932	69,716	72,446
Net Written Premiums	151,699	135,734	235,778
Corporate and other segment
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	0	0	0
Reserve for Losses and Loss Adjustment Expenses	0	0	0
Unearned Premiums	0	0	0
Net Earned Premiums	0	0	0
Net Investment Income	4,167	4,700	12,066
Losses and Loss Adjustment Expenses	0	0	0
Amortization of Policy Acquisition Costs	0	0	0
Other Operating Expenses	27,664	26,903	25,330
Net Written Premiums	$ 0	$ 0	$ 0

SCHEDULE IV - Reinsurance (Deta

SCHEDULE IV - Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Written Premiums	$ 1,305,948	$ 1,027,222	$ 843,719
Ceded to Other Companies Written Premiums	574,585	404,101	315,279
Assumed from Other Companies Written Premiums	164,787	139,551	238,186
Net written premiums	$ 896,150	$ 762,672	$ 766,626
Percentage of Amount Assumed to Net	18.40%	18.30%	31.10%
Excess and Surplus Lines
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Written Premiums	$ 922,320	$ 656,538	$ 530,077
Ceded to Other Companies Written Premiums	236,506	85,440	60,229
Assumed from Other Companies Written Premiums	0	0	43
Net written premiums	$ 685,814	$ 571,098	$ 469,891
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%
Specialty Admitted Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Written Premiums	$ 383,628	$ 370,684	$ 313,642
Ceded to Other Companies Written Premiums	329,005	318,506	255,473
Assumed from Other Companies Written Premiums	4,014	3,662	2,788
Net written premiums	$ 58,637	$ 55,840	$ 60,957
Percentage of Amount Assumed to Net	6.80%	6.60%	4.60%
Casualty Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Written Premiums	$ 0	$ 0	$ 0
Ceded to Other Companies Written Premiums	9,074	155	(423)
Assumed from Other Companies Written Premiums	160,773	135,889	235,355
Net written premiums	$ 151,699	$ 135,734	$ 235,778
Percentage of Amount Assumed to Net	106.00%	100.10%	99.80%

SCHEDULE V - Valuation and Qu_2

SCHEDULE V - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 3,948	$ 5,976	$ 3,079
Additions Amounts Charged to Expense	11,421	2,454	3,453
Deductions Amounts Written Off or Disposals	(2,529)	(4,482)	(556)
Balance at End of Period	12,840	3,948	5,976
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	3,948	2,757	2,136
Additions Amounts Charged to Expense	2,523	1,504	1,029
Deductions Amounts Written Off or Disposals	(812)	(313)	(408)
Balance at End of Period	5,659	3,948	2,757
Allowance for Credit Losses on Bank Loans
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	0	3,219	943
Additions Amounts Charged to Expense	8,898	950	2,424
Deductions Amounts Written Off or Disposals	(1,717)	(4,169)	(148)
Balance at End of Period	$ 7,181	$ 0	$ 3,219

SCHEDULE VI - Supplementary I_2

SCHEDULE VI - Supplementary Information Concerning Property Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Deferred policy acquisition costs	$ 62,006	$ 54,450	$ 72,365
Reserve for losses and loss adjustment expenses	2,045,506	1,661,459	1,292,349
Unearned premiums	524,377	386,473	418,114
Net earned premiums	823,746	815,398	741,109
Net investment income	75,652	61,256	61,119
Current year	603,094	582,604	533,905
Prior year	69,008	17,672	21,472
Total incurred losses and loss and adjustment expenses	672,102	600,276	555,377
Amortization of policy acquisition costs	83,893	111,103	116,001
Paid losses and loss adjustment expenses, net of reinsurance	488,729	396,013	326,680
Net written premiums	$ 896,150	$ 762,672	$ 766,626

Uncategorized Items - jrvr10k12

Label	Element	Value
Accounting Standards Update 2016-01 [Member] | AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (4,682,000)
Accounting Standards Update 2018-02 [Member] | AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 711,000