James River (JRVR) 10-Q 3 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 01, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	James River Group Holdings, Ltd.
Entity Central Index Key	1,620,459
Trading Symbol	jrvr
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		29,607,305
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2,017

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fixed maturity securities:
Available-for-sale, at fair value (amortized cost: 2017 – $1,006,715; 2016 – $940,212)	$ 1,016,818	$ 941,077
Trading, at fair value (amortized cost: 2017 – $3,802; 2016 – $5,052)	3,812	5,063
Equity securities available-for-sale, at fair value (cost: 2017 – $72,102; 2016 – $74,553)	78,705	76,401
Bank loan participations held-for-investment, at amortized cost, net of allowance	245,741	203,526
Short-term investments	42,331	50,844
Other invested assets	66,205	55,419
Total invested assets	1,453,612	1,332,330
Cash and cash equivalents	106,500	109,784
Accrued investment income	8,062	7,246
Premiums receivable and agents’ balances, net	390,534	265,315
Reinsurance recoverable on unpaid losses	283,949	182,737
Reinsurance recoverable on paid losses	14,221	2,877
Prepaid reinsurance premiums	87,087	90,147
Deferred policy acquisition costs	84,530	64,789
Intangible assets, net	38,484	38,931
Goodwill	181,831	181,831
Other assets	72,842	70,546
Total assets	2,721,652	2,346,533
Liabilities:
Reserve for losses and loss adjustment expenses	1,187,248	943,865
Unearned premiums	469,214	390,563
Payables to reinsurers	47,013	39,899
Senior debt	88,300	88,300
Junior subordinated debt	104,055	104,055
Accrued expenses	40,276	36,884
Other liabilities	64,577	49,746
Total liabilities	2,000,683	1,653,312
Commitments and contingent liabilities
Shareholders’ equity:
Common Shares – 2017 and 2016: $0.0002 par value; 200,000,000 shares authorized; 29,582,656 and 29,257,566 shares issued and outstanding, respectively	6	6
Preferred Shares – 2017 and 2016: $0.00125 par value; 20,000,000 shares authorized; no shares issued and outstanding	0	0
Additional paid-in capital	636,474	636,856
Retained earnings	71,904	55,232
Accumulated other comprehensive income	12,585	1,127
Total shareholders’ equity	720,969	693,221
Total liabilities and shareholders’ equity	$ 2,721,652	$ 2,346,533

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Available-for-sale debt securities, amortized cost	$ 1,006,715	$ 940,212
Trading securities, debt, amortized cost	3,802	5,052
Available-for-sale equity securities, amortized cost	$ 72,102	$ 74,553
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	29,582,656	29,257,566
Common stock, shares outstanding	29,582,656	29,257,566
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

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income and Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues
Gross written premiums	$ 338,351	$ 260,166	$ 844,005	$ 563,908
Ceded written premiums	(81,587)	(55,025)	(221,507)	(118,808)
Net written premiums	256,764	205,141	622,498	445,100
Change in net unearned premiums	(54,648)	(71,992)	(81,618)	(76,266)
Net earned premiums	202,116	133,149	540,880	368,834
Net investment income	14,880	15,797	45,327	38,622
Net realized investment (losses) gains	(171)	210	1,183	2,376
Other income	4,041	2,209	12,272	7,373
Total revenues	220,866	151,365	599,662	417,205
Expenses
Losses and loss adjustment expenses	150,445	83,326	386,898	233,491
Other operating expenses	54,260	43,579	156,189	124,732
Other expenses	119	(43)	351	36
Interest expense	2,304	2,079	6,651	6,294
Amortization of intangible assets	149	149	447	447
Total expenses	207,277	129,090	550,536	365,000
Income before taxes	13,589	22,275	49,126	52,205
Income tax expense	3,238	909	5,784	3,406
Net income	10,351	21,366	43,342	48,799
Other comprehensive income:
Net unrealized gains (losses), net of taxes of $(136) and $2,535 in 2017 and $(373) and $2,271 in 2016	716	(1,672)	11,458	26,740
Total comprehensive income	$ 11,067	$ 19,694	$ 54,800	$ 75,539
Per share data:
Basic earnings per share (in dollars per share)	$ 0.35	$ 0.73	$ 1.47	$ 1.68
Diluted earnings per share (in dollars per share)	0.34	0.71	1.43	1.64
Dividend declared per share (in dollars per share)	$ 0.30	$ 0.20	$ 0.90	$ 0.60
Weighted-average common shares outstanding:
Basic (in shares)	29,524,243	29,101,550	29,407,762	29,030,284
Diluted (in shares)	30,220,077	29,935,152	30,285,733	29,834,686

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Income and Comprehensive Income (Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Tax on net unrealized gains (losses)	$ (136)	$ 2,535	$ (373)	$ 2,271

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Shares	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income
Balance (in shares) at Dec. 31, 2015		28,941,547
Balance at Dec. 31, 2015	$ 681,038	$ 6	$ 630,820	$ 47,026	$ 3,186
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	48,799			48,799
Other comprehensive income	26,740				26,740
Dividends	(17,604)			(17,604)
Exercised (in shares)		174,949
Exercise of stock options and related excess tax benefits	2,585		2,585
Compensation expense under stock incentive plans	4,207		4,207
Balance (in shares) at Sep. 30, 2016		29,116,496
Balance at Sep. 30, 2016	$ 745,765	$ 6	637,612	78,221	29,926
Balance (in shares) at Dec. 31, 2016	29,257,566	29,257,566
Balance at Dec. 31, 2016	$ 693,221	$ 6	636,856	55,232	1,127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,342			43,342
Other comprehensive income	11,458				11,458
Dividends	(26,670)			(26,670)
Exercised (in shares)		300,168
Exercise of stock options	(5,093)		(5,093)
Compensation expense under stock incentive plans	5,338		5,338
Vesting of restricted share units (in shares)		24,922
Vesting of restricted share units	$ (627)		(627)
Balance (in shares) at Sep. 30, 2017	29,582,656	29,582,656
Balance at Sep. 30, 2017	$ 720,969	$ 6	$ 636,474	$ 71,904	$ 12,585

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net cash provided by operating activities	$ 121,001	$ 83,916
Securities available-for-sale:
Purchases – fixed maturity securities	(174,635)	(233,753)
Sales – fixed maturity securities	58,678	62,006
Maturities and calls – fixed maturity securities	48,172	106,687
Purchases – equity securities	0	(3,680)
Sales – equity securities	2,748	4,811
Bank loan participations:
Purchases	(192,624)	(86,074)
Sales	105,747	21,743
Maturities	47,157	45,861
Other invested assets:
Purchases	(6,322)	(1,990)
Return of capital	0	717
Maturities and repayments	0	6,500
Short-term investments, net	8,513	(3,986)
Securities receivable or payable, net	12,682	705
Purchases of property and equipment	(2,118)	(2,142)
Net cash used in investing activities	(92,002)	(82,595)
Financing activities
Dividends paid	(26,596)	(17,428)
Issuance of common shares under equity incentive plans	1,548	2,134
Common share repurchases	(6,613)	(716)
Repayments of financing obligations net of proceeds	(622)	(844)
Net cash used in financing activities	(32,283)	(16,854)
Change in cash and cash equivalents	(3,284)	(15,533)
Cash and cash equivalents at beginning of period	109,784	106,406
Cash and cash equivalents at end of period	106,500	90,873
Supplemental information
Interest paid	$ 6,626	$ 6,011

Accounting Policies

Accounting Policies	9 Months Ended
	Sep. 30, 2017
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 six insurance companies based in the United States (“U.S.”) focused on specialty insurance niches and a Bermuda-based reinsurance company 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.”). JRG Holdings 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 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, Falls Lake General Insurance Company, an Ohio 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 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. Basis of Presentation The accompanying condensed consolidated financial statements and notes have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and do not contain all of the information and footnotes required by U.S. GAAP for complete financial statements. The condensed consolidated financial statements include the results of the Company and its subsidiaries from their respective dates of inception or acquisition, as applicable. Readers are urged to review the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 for a more complete description of the Company’s business and accounting policies. In the opinion of management, all adjustments necessary for a fair presentation of the condensed consolidated financial statements have been included. Such adjustments consist only of normal recurring items. Interim results are not necessarily indicative of results of operations for the full year. The consolidated balance sheet as of December 31, 2016 was derived from the Company’s audited annual consolidated financial statements. Intercompany transactions and balances have been eliminated. Estimates and Assumptions Preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying disclosures. Those estimates are inherently subject to change, and actual results may ultimately differ from those estimates. 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 the 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 condensed 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 $31.3 million and $27.1 million as of September 30, 2017 and December 31, 2016 , respectively, representing the Company’s maximum exposure to loss. Income Tax Expense Our effective tax rate fluctuates from period to period based on the relative mix of income reported by country and the respective tax rates imposed by each tax jurisdiction. For the three months ended September 30, 2017 and 2016 , our U.S. federal income tax expense was 23.8% and 4.1% of income before taxes, respectively ( 11.8% and 6.5% for the nine months ended September 30, 2017 and 2016 , respectively). The catastrophe losses this quarter reduced underwriting income in both the Excess and Surplus Lines and the Casualty Reinsurance segments and this caused a higher proportion of the Group's income to be taxed at a higher rate applicable to earnings in the United States. For U.S.-sourced income, the Company’s U.S. federal income tax expense differs from the amounts computed by applying the federal statutory income tax rate to income before taxes due primarily to interest income on tax-advantaged state and municipal securities (state and municipal securities represent 12.2% and 10.0% of our available-for-sale securities at September 30, 2017 and 2016 , respectively), dividends received income, and excess tax benefits on share based compensation. Adopted Accounting Standards Effective January 1, 2017, the Company adopted Accounting Standards Update (“ASU”) 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting using the prospective method. The guidance requires that all tax effects related to share-based payments be made through the income statement at the time of settlement as opposed to excess tax benefits being recognized in additional paid-in capital under the previous guidance . The ASU also removes the requirement to delay recognition of a tax benefit until it reduces current taxes payable. Additionally, all tax related cash flows resulting from share-based payments are now reported as operating activities on the statement of cash flows, a change from the previous requirement to present tax benefits as an inflow from financing activities and an outflow from operating activities. For the nine months ended September 30, 2016 , net cash provided by operating activities increased by $1.2 million and net cash used in financing activities increased by $1.2 million for the adoption of ASU 2016-09. The Company has elected to recognize forfeitures as they occur in accordance with ASU 2016-09. The adoption of ASU 2016-09 did not materially impact the Company’s consolidated income statements. Prospective Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) . The guidance applies to all companies that either enter into contracts with customers to transfer goods or services or enter into contracts for the transfer of nonfinancial assets, unless those contracts are within the scope of other standards, such as insurance contracts. Under this guidance, a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the current guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 becomes effective for the Company during the first quarter of 2018 and must be applied retrospectively. The Company is completing it evaluation of ASU 2014-09 to determine what, if any, impact that adopting this standard will have on reported fee income. As part of this evaluation, the Company is completing a review of its contracts and assessing the impact the new standard will have on its disclosures and internal controls. The Company does not believe adoption will have a material impact on its consolidated financial statements. The Company plans to adopt this ASU using the modified retrospective method, with the cumulative effect of initially applying this update recognized in the first quarter of 2018. The Company is in the process of drafting an updated accounting policy for revenue recognition, evaluating new disclosure requirements and identifying and implementing appropriate changes to its business processes, systems and controls to support recognition and disclosure under the new guidance. In January 2016, the FASB issued ASU 2016-01, Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities . Among other things, this ASU will require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. This ASU is effective for interim and annual reporting periods beginning after December 15, 2017. Upon adoption, a cumulative-effect adjustment to the balance sheet will be made as of the beginning of the fiscal year of adoption. Adoption of this ASU is not expected to have a material impact on the Company's financial position, cash flows, or total comprehensive income, but will have an impact on the Company's results of operations, as changes in fair value of equity instruments will be presented in net income rather than other comprehensive income. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . Under current guidance for lessees, leases are only included on the balance sheet if certain criteria, classifying the agreement as a capital lease, are met. This update will require 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. This ASU is effective for annual and interim reporting periods beginning after December 15, 2018. Early adoption is permitted. Upon adoption, leases will be recognized and measured at the beginning of the earliest period presented using a modified retrospective approach. The Company is currently evaluating ASU 2016-02 to determine the potential impact that adopting this standard will have on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Current GAAP delays the recognition of credit losses until 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 runs through 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. Upon adoption, this ASU will be applied using the modified-retrospective approach, by which a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first reporting period presented. The Company has not yet completed the analysis of how adopting this ASU will affect the Company’s financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments to address the diversity in practice of how certain cash receipts and payments are classified in the statement of cash flows. The update addresses specific issues, including distributions received from equity method investees and the classification of cash receipts and payments that have aspects of more than one class of cash flows. This ASU is effective for annual and interim reporting periods beginning after December 15, 2017. Upon adoption, the update will be applied using the retrospective transition method. The Company does not expect that the adoption of this ASU will have a material impact on its statement of cash flows.

Investments

Investments	9 Months Ended
	Sep. 30, 2017
Investments [Abstract]
Investments	Investments The Company’s available-for-sale investments are summarized as follows: Cost or Gross Gross Fair (in thousands) September 30, 2017 Fixed maturity securities: State and municipal $ 129,786 $ 5,608 $ (416 ) $ 134,978 Residential mortgage-backed 140,053 946 (1,942 ) 139,057 Corporate 415,817 7,490 (1,901 ) 421,406 Commercial mortgage and asset-backed 176,952 984 (489 ) 177,447 Obligations of U.S. government corporations and agencies 62,435 37 (97 ) 62,375 U.S. Treasury securities and obligations guaranteed by the U.S. government 79,647 77 (244 ) 79,480 Redeemable preferred stock 2,025 50 — 2,075 Total fixed maturity securities 1,006,715 15,192 (5,089 ) 1,016,818 Equity securities 72,102 8,116 (1,513 ) 78,705 Total investments available-for-sale $ 1,078,817 $ 23,308 $ (6,602 ) $ 1,095,523 December 31, 2016 Fixed maturity securities: State and municipal $ 101,793 $ 5,032 $ (984 ) $ 105,841 Residential mortgage-backed 152,703 1,070 (2,975 ) 150,798 Corporate 379,727 4,382 (5,661 ) 378,448 Commercial mortgage and asset-backed 167,967 906 (826 ) 168,047 Obligations of U.S. government corporations and agencies 64,823 276 (85 ) 65,014 U.S. Treasury securities and obligations guaranteed by the U.S. government 71,174 131 (185 ) 71,120 Redeemable preferred stock 2,025 — (216 ) 1,809 Total fixed maturity securities 940,212 11,797 (10,932 ) 941,077 Equity securities 74,553 4,503 (2,655 ) 76,401 Total investments available-for-sale $ 1,014,765 $ 16,300 $ (13,587 ) $ 1,017,478 The amortized cost and fair value of available-for-sale investments in fixed maturity securities at September 30, 2017 are summarized, by contractual maturity, as follows: Cost or Fair (in thousands) One year or less $ 117,434 $ 117,483 After one year through five years 253,240 255,514 After five years through ten years 192,269 193,760 After ten years 124,742 131,482 Residential mortgage-backed 140,053 139,057 Commercial mortgage and asset-backed 176,952 177,447 Redeemable preferred stock 2,025 2,075 Total $ 1,006,715 $ 1,016,818 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) September 30, 2017 Fixed maturity securities: State and municipal $ 27,813 $ (220 ) $ 5,371 $ (196 ) $ 33,184 $ (416 ) Residential mortgage-backed 81,667 (882 ) 30,486 (1,060 ) 112,153 (1,942 ) Corporate 106,427 (998 ) 31,522 (903 ) 137,949 (1,901 ) Commercial mortgage and asset-backed 46,526 (288 ) 11,861 (201 ) 58,387 (489 ) Obligations of U.S. government corporations and agencies 52,157 (97 ) — — 52,157 (97 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 60,192 (243 ) 2,223 (1 ) 62,415 (244 ) Total fixed maturity securities 374,782 (2,728 ) 81,463 (2,361 ) 456,245 (5,089 ) Equity securities 3,913 (68 ) 8,847 (1,445 ) 12,760 (1,513 ) Total investments available-for-sale $ 378,695 $ (2,796 ) $ 90,310 $ (3,806 ) $ 469,005 $ (6,602 ) December 31, 2016 Fixed maturity securities: State and municipal $ 28,398 $ (984 ) $ — $ — $ 28,398 $ (984 ) Residential mortgage-backed 93,242 (1,548 ) 32,330 (1,427 ) 125,572 (2,975 ) Corporate 199,841 (4,212 ) 8,477 (1,449 ) 208,318 (5,661 ) Commercial mortgage and asset-backed 47,990 (799 ) 7,195 (27 ) 55,185 (826 ) Obligations of U.S. government corporations and agencies 50,573 (85 ) — — 50,573 (85 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 48,989 (185 ) — — 48,989 (185 ) Redeemable preferred stock 1,809 (216 ) — — 1,809 (216 ) Total fixed maturity securities 470,842 (8,029 ) 48,002 (2,903 ) 518,844 (10,932 ) Equity securities 21,345 (1,071 ) 6,558 (1,584 ) 27,903 (2,655 ) Total investments available-for-sale $ 492,187 $ (9,100 ) $ 54,560 $ (4,487 ) $ 546,747 $ (13,587 ) The Company held securities of 146 issuers that were in an unrealized loss position at September 30, 2017 with a total fair value of $469.0 million and gross unrealized losses of $6.6 million. None of the fixed maturity securities with unrealized losses has ever missed, or been delinquent on, a scheduled principal or interest payment. At September 30, 2017 , 99.1% 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. Fixed maturity securities with ratings below investment grade by Standard & Poor’s or another nationally recognized rating agency at September 30, 2017 had an aggregate fair value of $9.0 million and an aggregate net unrealized gain of $248,000 . Management concluded that none of the fixed maturity securities with an unrealized loss at September 30, 2017 or December 31, 2016 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. Management also concluded that none of the equity securities with an unrealized loss at September 30, 2017 or December 31, 2016 experienced an other-than-temporary impairment. Management has evaluated the near-term prospects of these equity securities in relation to the severity and duration of the impairment, and management has the ability and intent to hold these securities until a recovery of their fair value. At September 30, 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 through a power purchase agreement with Puerto Rico Electric Power Authority (“PREPA”), a public corporation and governmental agency of the Commonwealth of Puerto Rico. PREPA’s credit strength and ability to make timely payments has been impacted by the economic conditions in Puerto Rico. In July 2017, PREPA filed a petition for relief in U.S. District Court under Title III of the Puerto Rico Oversight, Management, and Economic Stability Act. The recent devastation caused by Hurricane Maria on the island of Puerto Rico raises additional doubt about PREPA's ability to make payments to the issuer. The loan was scheduled to mature in November 2017, but the issuer has proposed deferring payment until March 2018. Based on this deferral request and the uncertainty regarding repayment, management has concluded that an allowance for credit losses should be established on the loan to reduce its carrying value to $0 at September 30, 2017 . At December 31, 2016 , the loan had a carrying value of $1.7 million , unpaid principal of $2.0 million , and an allowance for credit losses of $177,000 . The Company’s bank loan portfolio includes loans to oil and gas companies in the energy sector. The market values of these loans have been impacted by declining energy prices. At September 30, 2017 , the Company’s oil and gas exposure in the bank loan portfolio was in four loans with a carrying value of $9.7 million and an unrealized loss of $1.9 million . All of the loans were current at September 30, 2017 . Management concluded that two of these loans were impaired as of September 30, 2017 . At September 30, 2017 , the two impaired loans had a carrying value of $1.9 million , unpaid principal of $2.5 million and an allowance for credit losses of $490,000 . At December 31, 2016 , one loan was impaired with a carrying value of $1.6 million , unpaid principal of $2.2 million and an allowance for credit losses of $545,000 . Management also concluded that one non-energy sector loan was impaired at September 30, 2017 . The loan has a carrying value of $499,000 , unpaid principal of $708,000 , and an allowance for credit losses of $209,000 . At December 31, 2016 , three non-energy sector loans were impaired with a total carrying value of $3.2 million , unpaid principal of $3.5 million , and an allowance for credit losses of $221,000 . The aggregate allowance for credit losses was $1.5 million at September 30, 2017 on impaired loans from four issuers with a total carrying value of $2.4 million and unpaid principal of $4.0 million . At December 31, 2016 , the aggregate allowance for credit losses was $943,000 on impaired loans from five issuers with a total carrying value of $6.5 million and unpaid principal of $7.6 million . The aggregate allowance for credit losses on impaired loans was $2.0 million at September 30, 2016 and $4.3 million at December 31, 2015. 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. 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. 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. Interest received on nonaccrual loans generally is reported as investment income. There were no bank loans on nonaccrual status at September 30, 2017 or December 31, 2016 . 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 a dvice of the Company’s independent 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. The Company generally records 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. Bank loans are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. The average recorded investment in impaired bank loans was $4.5 million and $8.0 million during the nine months ended September 30, 2017 and 2016 , respectively. Investment income of $231,000 and $237,000 , respectively, was recognized during the time within those periods that the loans were impaired. The Company recorded net realized investment losses of $729,000 and $594,000 in the three months and nine months ended September 30, 2017 , respectively, for changes in the fair value of impaired bank loans. For the three months and nine months ended September 30, 2016 , the Company recorded net realized investment losses of $663,000 and $53,000 , respectively, for changes in the fair value of impaired bank loans. Changes in unrealized gains or losses on securities held for trading are recorded as trading gains or losses within net investment income. Net investment income for the three months ended September 30, 2017 includes $2,000 of net trading losses, all relating to securities still held at September 30, 2017 . Trading gains or losses included in net investment income in the nine months ended September 30, 2017 were $0 . The Company’s realized gains and losses are summarized as follows: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Fixed maturity securities: Gross realized gains $ 378 $ 70 $ 734 $ 1,479 Gross realized losses (4 ) — (331 ) (2 ) 374 70 403 1,477 Bank loan participations: Gross realized gains 341 273 1,948 1,466 Gross realized losses (839 ) (1,308 ) (1,528 ) (1,741 ) (498 ) (1,035 ) 420 (275 ) Equity securities: Gross realized gains — 1,174 409 1,174 Gross realized losses (45 ) — (45 ) — (45 ) 1,174 364 1,174 Short-term investments and other: Gross realized gains 1 2 1 3 Gross realized losses (3 ) (1 ) (5 ) (3 ) (2 ) 1 (4 ) — Total $ (171 ) $ 210 $ 1,183 $ 2,376 Realized investment gains or losses are determined on a specific identification basis. 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. Investment Income Carrying Value September 30, December 31, Three Months Ended Nine Months Ended 2017 2016 2017 2016 2017 2016 (in thousands) Renewable energy LLCs (a) $ 31,264 $ 27,067 $ 1,516 $ 2,745 $ 8,631 $ 1,976 Renewable energy notes receivable ( b) 5,688 — 238 — 287 450 Limited partnerships (c) 24,753 23,852 477 1,948 1,562 3,784 Bank holding companies (d) 4,500 4,500 85 86 257 257 Total other invested assets $ 66,205 $ 55,419 $ 2,316 $ 4,779 $ 10,737 $ 6,467 (a) The Company’s Corporate and Other segment owns equity interests ranging from 2.6% to 32.8% 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 affiliate of the Company’s largest shareholder and the Company’s 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 $4.4 million and $2.4 million in the nine months ended September 30, 2017 and 2016 , respectively. (b) The Company has invested in notes receivable for renewable energy projects. In June 2017, the Company invested $5.7 million in a note with an affiliate of the Company’s largest shareholder. Interest on the note, which matures in 2021, is fixed at 15.0% . The Company is committed to investing another $3.1 million in the note and commitment fees of 2.5% are earned on the unfunded commitment. Interest income on the note was $238,000 and $287,000 for the three and nine months ended September 30, 2017 , respectively. The Company’s Chairman and Chief Executive Officer and one of the Company’s directors are also lenders on this project. In May 2016, the outstanding principal on a $6.5 million note was fully repaid. Income prior to repayment of the note was $450,000 in the nine months ended September 30, 2016 . This note was also with an affiliate of the Company's largest shareholder. (c) The Company owns investments in limited partnerships that invest in concentrated portfolios of publicly-traded small cap equities, loans of middle market private equity sponsored companies, and equity tranches of collateralized loan obligations (CLOs). Income f rom 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 $2.9 million at September 30, 2017 . The Company recognized investment income of $246,000 and $178,000 on the investment for the nine months ended September 30, 2017 and 2016 , respectively. The Company’s Excess and Surplus Lines segment holds investments in limited partnerships of $21.9 million at September 30, 2017 . Investment income of $1.3 million and $3.6 million was recognized on the investments for the nine months ended September 30, 2017 and 2016 , respectively. At September 30, 2017 , the Company’s Excess and Surplus Lines segment has an outstanding commitment to invest another $625,000 in a limited partnership that invests in loans of middle market private equity sponsored companies. (d) The Company holds $4.5 million of subordinated notes issued by a bank holding company. Interest on the notes, which mature on August 12, 2023, is fixed at 7.6% per annum. Interest income on the notes was $257,000 in both nine months ended September 30, 2017 and 2016 . The Company’s Chairman and Chief Executive Officer was previously the Lead Independent Director of the bank holding company and an investor in the bank holding company. Additionally, one of the Company’s directors was an investor in the bank holding company and is currently a lender to the bank holding company. At September 30, 2017 , 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 $5.0 million at September 30, 2017 , is classified as an available-for-sale fixed maturity. Realized investments gains of $409,000 were recognized in the nine months ended September 30, 2017 related to the sale of common shares of the bank holding company. Income of $266,000 was recognized on the shares for the nine months ended September 30, 2016 . The Company holds a $1.0 million certificate of deposit issued by the bank holding company. The certificate of deposit, which matures on December 19, 2017, is carried as a short-term investment. Interest income of $2,000 and $3,000 was recognized on this investment for the nine months ended September 30, 2017 and 2016 , respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2017
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. Goodwill resulting from the Merger was $181.8 million at September 30, 2017 and December 31, 2016 . The gross carrying amounts and accumulated amortization for each major specifically identifiable intangible asset class were as follows: September 30, 2017 December 31, 2016 Life Gross Accumulated Gross Accumulated ($ in thousands) Intangible Assets Trademarks Indefinite $ 22,200 $ — $ 22,200 $ — Insurance licenses and authorities Indefinite 9,164 — 9,164 — Identifiable intangibles not subject to amortization 31,364 — 31,364 — Broker relationships 24.6 11,611 4,491 11,611 4,044 Identifiable intangible assets subject to amortization 11,611 4,491 11,611 4,044 $ 42,975 $ 4,491 $ 42,975 $ 4,044

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Share	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 condensed consolidated financial statements: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands, except share and per share amounts) Net income to shareholders $ 10,351 $ 21,366 $ 43,342 $ 48,799 Weighted average common shares outstanding: Basic 29,524,243 29,101,550 29,407,762 29,030,284 Common share equivalents 695,834 833,602 877,971 804,402 Diluted 30,220,077 29,935,152 30,285,733 29,834,686 Earnings per share: Basic $ 0.35 $ 0.73 $ 1.47 $ 1.68 Common share equivalents (0.01 ) (0.02 ) (0.04 ) (0.04 ) Diluted $ 0.34 $ 0.71 $ 1.43 $ 1.64 Common share equivalents relate to stock options and restricted share units (“RSU’s”). For the three and nine months ended September 30, 2017 , common share equivalents of 203,758 and 168,167 shares, respectively, were excluded from the calculations of diluted earnings per share as their effects were anti-dilutive. For the three and nine months ended September 30, 2016 , all common share equivalents were dilutive.

Reserve for Losses and Loss Adj

Reserve for Losses and Loss Adjustment Expenses	9 Months Ended
	Sep. 30, 2017
Liability for Claims and Claims Adjustment Expense [Abstract]
Reserve for Losses and Loss Adjustment Expenses	Reserve 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 condensed consolidated balance sheets: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Reserve for losses and loss adjustment expenses net of reinsurance recoverables at beginning of period $ 839,508 $ 689,631 $ 761,128 $ 653,534 Add: Incurred losses and loss adjustment expenses net of reinsurance: Current year 158,009 88,659 396,161 248,239 Prior years (7,564 ) (5,333 ) (9,263 ) (14,748 ) Total incurred losses and loss and adjustment expenses 150,445 83,326 386,898 233,491 Deduct: Loss and loss adjustment expense payments net of reinsurance: Current year 21,305 10,734 38,911 21,624 Prior years 65,349 43,847 205,816 147,025 Total loss and loss adjustment expense payments 86,654 54,581 244,727 168,649 Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period 903,299 718,376 903,299 718,376 Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period 283,949 156,286 283,949 156,286 Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period $ 1,187,248 $ 874,662 $ 1,187,248 $ 874,662 The Company experienced $7.6 million of favorable reserve development in the three months ended September 30, 2017 on the reserve for losses and loss adjustment expenses held at December 31, 2016 . This reserve development included $5.1 million of favorable development in the Excess and Surplus Lines segment, primarily from the 2015 and 2014 accident years which were partially offset by unfavorable development in the 2016 accident year. This favorable development occurred because our actuarial studies at September 30, 2017 for the Excess and Surplus Lines segment indicated that our loss experience on our casualty business continues to be below our initial expected loss ratios. The Specialty Admitted Insurance segment experienced $3.0 million of favorable development, primarily due to favorable development in the workers' compensation business for the 2015 and 2014 accident years. The Company also experienced $581,000 of adverse development for the Casualty Reinsurance segment. The development was primarily related to the 2011 and 2013 contracts with one reinsured. The Company experienced $5.3 million of favorable reserve development in the three months ended September 30, 2016 on the reserve for losses and loss adjustment expenses held at December 31, 2015 . This reserve development included $5.8 million of favorable development in the Excess and Surplus Lines segment, primarily from the 2013, 2014, and 2015 accident years. This favorable development occurred because our actuarial studies at September 30, 2016 for the Excess and Surplus Lines segment indicated that our loss experience on our casualty business continues to be below our initial expected loss ratios. The Company also experienced $1.6 million of favorable development in the Specialty Admitted Insurance segment primarily from the 2013, 2014 and 2015 accident years. The Casualty Reinsurance segment experienced $2.0 million of adverse development on prior accident years primarily from two contracts from 2012 and 2013 underwriting years that had higher than expected reported losses in the quarter. The Company experienced $9.3 million of favorable reserve development in the nine months ended September 30, 2017 on the reserve for losses and loss adjustment expenses held at December 31, 2016 . This reserve development included $9.8 million of favorable development in the Excess and Surplus Lines segment, primarily from the 2014 through 2016 accident years. This favorable development occurred because our actuarial studies at September 30, 2017 for the Excess and Surplus Lines segment indicated that our loss experience on our casualty business continues to be below our initial expected loss ratios. The Specialty Admitted Insurance segment experienced $2.1 million of favorable development, primarily due to favorable development in the workers' compensation business for the 2016, 2015, and 2014 accident years which was partially offset by adverse development in programs for the 2016 accident year. The Company also experienced $2.6 million of adverse development for the Casualty Reinsurance segment. The development was mostly related to the 2011 through 2013 contracts with one reinsured. The Company experienced $14.7 million of favorable reserve development in the nine months ended September 30, 2016 on the reserve for losses and loss adjustment expenses held at December 31, 2015 . This reserve development included $13.8 million of favorable development in the Excess and Surplus Lines segment, primarily from the 2013, 2014, and 2015 accident years. This favorable development occurred because our actuarial studies at September 30, 2016 for the Excess and Surplus Lines segment indicated that our loss experience on our casualty business continues to be below our initial expected loss ratios. The Company also experienced favorable development of $2.5 million in the Specialty Admitted Insurance segment primarily from accident years 2010 through 2014. The Casualty Reinsurance segment experienced $1.5 million of adverse reserve development on prior accident years primarily from two contracts from the 2012 and 2013 years that had higher than expected reported losses in 2016.

Other Comprehensive Income

Other Comprehensive Income	9 Months Ended
	Sep. 30, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income	Other Comprehensive Income The following table summarizes the components of other comprehensive income: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Unrealized gains (losses) arising during the period, before U.S. income taxes $ 909 $ (802 ) $ 14,760 $ 31,662 U.S. income taxes 21 (38 ) (2,771 ) (3,115 ) Unrealized gains (losses) arising during the period, net of U.S. income taxes 930 (840 ) 11,989 28,547 Less reclassification adjustment: Net realized investment gains 329 1,243 767 2,651 U.S. income tax expenses (115 ) (411 ) (236 ) (844 ) Reclassification adjustment for investment gains realized in net income 214 832 531 1,807 Other comprehensive income (loss) $ 716 $ (1,672 ) $ 11,458 $ 26,740

Contingent Liabilities

Contingent Liabilities	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingent Liabilities	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, has entered into 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 $100.0 million facility, $85.6 million of letters of credit were issued through September 30, 2017 which were secured by deposits of $95.8 million . Under a $102.5 million facility, $47.6 million of letters of credit were issued through September 30, 2017 which were secured by deposits of $61.6 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 $269.8 million at September 30, 2017 . On August 2, 2017, the Company, and its wholly-owned subsidiary, JRG Re, together as borrowers, entered into a credit agreement 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. At September 30, 2017, there were no loans or letters of credit outstanding on the facility. The Company is also exposed to credit risk relating to a set of insurance contracts with an insured group of companies under which the Company pays losses and loss adjustment expenses on the contract. The Company has indemnity agreements with this group of insured parties (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 the insured parties and other expenses incurred by the Company. The insured parties are 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 agreement, 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. This collateral is currently provided through a collateral trust arrangement established in favor of the Company by a captive insurance company affiliate of the insured group. At September 30, 2017 , the cash equivalent collateral held in the collateral trust arrangement was approximately $670.1 million , which exceeds the amount of claims receivable and unpaid reported losses and loss adjustment expenses outstanding. This is a rapidly growing relationship, and as such, there is 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.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information The Company has four reportable segments: the Excess and Surplus Lines segment, the Specialty Admitted Insurance segment, the Casualty Reinsurance segment, and the Corporate and Other segment. Segment profit (loss) is measured by underwriting profit (loss), which is generally defined as net earned premiums less loss and loss adjustment expenses and other operating expenses of the operating segments. Fee income of the Excess and Surplus Lines segment is included in that segment’s underwriting profit. Fee income of $3.9 million and $2.1 million was included in underwriting profit for the three months ended September 30, 2017 and 2016 , respectively. For the nine months ended September 30, 2017 and 2016 , fee income of $12.0 million and $7.2 million , respectively, was included in underwriting profit. Segment results are reported prior to the effects of intercompany reinsurance agreements among the Company’s insurance subsidiaries. The following table summarizes the Company’s segment results: Excess and Specialty Casualty Corporate Total (in thousands) Three Months Ended September 30, 2017 Gross written premiums $ 140,425 $ 84,838 $ 113,088 $ — $ 338,351 Net earned premiums 123,606 19,324 59,186 — 202,116 Underwriting profit (loss) of insurance segments 9,946 851 (2,933 ) — 7,864 Net investment income 3,727 626 8,590 1,937 14,880 Interest expense — — — 2,304 2,304 Segment revenues 131,033 19,992 67,860 1,981 220,866 Segment goodwill 181,831 — — — 181,831 Segment assets 821,668 405,209 1,372,234 122,541 2,721,652 Three Months Ended September 30, 2016 Gross written premiums $ 99,882 $ 56,119 $ 104,165 $ — $ 260,166 Net earned premiums 81,672 13,204 38,273 — 133,149 Underwriting profit of insurance segments 12,408 702 133 — 13,243 Net investment income 5,236 647 7,085 2,829 15,797 Interest expense — — — 2,079 2,079 Segment revenues 88,671 13,890 44,808 3,996 151,365 Segment goodwill 181,831 — — — 181,831 Segment assets 728,231 261,063 1,258,522 100,095 2,347,911 Nine Months Ended September 30, 2017 Gross written premiums $ 387,424 $ 234,073 $ 222,508 $ — $ 844,005 Net earned premiums 334,723 53,337 152,820 — 540,880 Underwriting profit (loss) of insurance segments 30,475 2,246 (3,863 ) — 28,858 Net investment income 10,751 1,893 23,100 9,583 45,327 Interest expense — — — 6,651 6,651 Segment revenues 357,607 55,351 176,580 10,124 599,662 Segment goodwill 181,831 — — — 181,831 Segment assets 821,668 405,209 1,372,234 122,541 2,721,652 Nine Months Ended September 30, 2016 Gross written premiums $ 279,417 $ 119,007 $ 165,484 $ — $ 563,908 Net earned premiums 217,742 36,816 114,276 — 368,834 Underwriting profit of insurance segments 31,395 1,302 673 — 33,370 Net investment income 13,601 1,898 20,248 2,875 38,622 Interest expense — — — 6,294 6,294 Segment revenues 239,401 39,266 134,420 4,118 417,205 Segment goodwill 181,831 — — — 181,831 Segment assets 728,231 261,063 1,258,522 100,095 2,347,911 The following table reconciles the underwriting profit (loss) of the operating segments by individual segment to consolidated income before taxes: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Underwriting profit (loss) of the insurance segments: Excess and Surplus Lines $ 9,946 $ 12,408 $ 30,475 $ 31,395 Specialty Admitted Insurance 851 702 2,246 1,302 Casualty Reinsurance (2,933 ) 133 (3,863 ) 673 Total underwriting profit of insurance segments 7,864 13,243 28,858 33,370 Other operating expenses of the Corporate and Other segment (6,507 ) (4,870 ) (19,063 ) (15,597 ) Underwriting profit 1,357 8,373 9,795 17,773 Net investment income 14,880 15,797 45,327 38,622 Net realized investment (losses) gains (171 ) 210 1,183 2,376 Amortization of intangible assets (149 ) (149 ) (447 ) (447 ) Other income and expenses (24 ) 123 (81 ) 175 Interest expense (2,304 ) (2,079 ) (6,651 ) (6,294 ) Income before taxes $ 13,589 $ 22,275 $ 49,126 $ 52,205 Underwriting profit (loss) for the three and nine months ended September 30, 2017 reflects $10.0 million of catastrophe losses from Hurricanes Harvey, Irma, and Maria. The Excess and Surplus Lines segment includes $7.3 million of such losses primarily related to property losses in Florida. The Casualty Reinsurance segment includes $2.7 million of losses primarily related to nonstandard auto losses in Texas. The correction of a contingent commission accrual and related commission expense increased underwriting expenses of the Casualty Reinsurance segment by $0 and $2.0 million in the three and nine months ended September 30, 2017 , respectively. In addition, the correction of an expense reimbursement accrual for the Excess and Surplus Lines segment reduced underwriting expenses by $1.3 million and $0 for the three and nine months ended September 30, 2017, respectively. There was also a third quarter adjustment to increase the investment income of the Casualty Reinsurance segment by $480,000 for the three months ended September 30, 2017. Investment income for the Casualty Reinsurance segment had been understated for the three months ended June 30, 2017.

Other Operating Expenses and Ot

Other Operating Expenses and Other Expenses	9 Months Ended
	Sep. 30, 2017
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: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Amortization of policy acquisition costs $ 35,311 $ 24,761 $ 94,563 $ 70,552 Other underwriting expenses of the operating segments 12,442 13,948 42,563 38,583 Other operating expenses of the Corporate and Other segment 6,507 4,870 19,063 15,597 Total $ 54,260 $ 43,579 $ 156,189 $ 124,732 Other expenses of $119,000 and $351,000 for the three and nine months ended September 30, 2017 , respectively, were primarily employee severance and legal and other professional services associated with the Company's May 2017 secondary offering. For the three and nine months ended September 30, 2016 , other expenses of $(43,000) and $36,000 , respectively, were largely comprised of filing fees and due diligence costs related to merger and acquisition activities.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
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, 2015. 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 September 30, 2017 are summarized below: Fair Value Measurements Using Quoted Prices Significant Significant Total (in thousands) Available-for-sale securities: Fixed maturity securities: State and municipal $ — $ 134,978 $ — $ 134,978 Residential mortgage-backed — 139,057 — 139,057 Corporate — 421,406 — 421,406 Commercial mortgage and asset-backed — 172,447 5,000 177,447 Obligations of U.S. government corporations and agencies — 62,375 — 62,375 U.S. Treasury securities and obligations guaranteed by the U.S. government 78,864 616 — 79,480 Redeemable preferred stock — 2,075 — 2,075 Total fixed maturity securities 78,864 932,954 5,000 1,016,818 Equity securities: Preferred stock — 66,833 — 66,833 Common stock 11,138 734 — 11,872 Total equity securities 11,138 67,567 — 78,705 Total available-for-sale securities $ 90,002 $ 1,000,521 $ 5,000 $ 1,095,523 Trading securities: Fixed maturity securities $ — $ 3,812 $ — $ 3,812 Short-term investments $ 1,000 $ 41,331 $ — $ 42,331 Assets measured at fair value on a recurring basis as of December 31, 2016 are summarized below: Fair Value Measurements Using Quoted Prices Significant Significant Total (in thousands) Available-for-sale securities: Fixed maturity securities: State and municipal $ — $ 105,841 $ — $ 105,841 Residential mortgage-backed — 150,798 — 150,798 Corporate — 378,448 — 378,448 Commercial mortgage and asset-backed — 163,047 5,000 168,047 Obligations of U.S. government corporations and agencies — 65,014 — 65,014 U.S. Treasury securities and obligations guaranteed by the U.S. government 70,465 655 — 71,120 Redeemable preferred stock — 1,809 — 1,809 Total fixed maturity securities 70,465 865,612 5,000 941,077 Equity securities: Preferred stock — 64,827 — 64,827 Common stock 10,840 734 — 11,574 Total equity securities 10,840 65,561 — 76,401 Total available-for-sale securities $ 81,305 $ 931,173 $ 5,000 $ 1,017,478 Trading securities: Fixed maturity securities $ 1,250 $ 3,813 $ — $ 5,063 Short-term investments $ 1,100 $ 49,744 $ — $ 50,844 The beginning and ending balances of assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) consist of one available-for-sale fixed maturity security with a fair value of $5.0 million , and there was no activity (purchases, sales, transfers) involving Level 3 securities for the nine months ended September 30, 2017 and 2016 . A market approach using prices in trades of comparable securities was utilized to determine the fair value for this security at September 30, 2017 and December 31, 2016 . Transfers out of Level 3 occur when the Company is able to obtain reliable prices from pricing vendors for securities 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 to value the securities. There were no transfers between Level 1 and Level 2 during the nine months ended September 30, 2017 or 2016 . The Company recognizes transfers between levels at the beginning of the reporting period. There were no realized gains or losses included in earnings for the nine months ended September 30, 2017 attributable to the change in unrealized gains or losses relating to Level 3 assets valued at fair value on a recurring basis that are still held at September 30, 2017 . 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 Significant Significant Total (in thousands) September 30, 2017 Bank loan participations held-for-investment $ — $ — $ 2,445 $ 2,445 December 31, 2016 Bank loan participations held-for-investment $ — $ — $ 4,849 $ 4,849 Bank loan participations held-for-investment that were determined to be impaired were written down to their fair value of $2.4 million at September 30, 2017 and $4.8 million at December 31, 2016 . 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. At September 30, 2017 , there were bank loan participations with an unpaid principal balance of $807,000 and a carrying value of $0 for which external sources were unavailable to determine fair value. At December 31, 2016 , there were bank loan participations with an unpaid principal balance of $2.3 million and a carrying value of $2.0 million for which external sources were unavailable to determine fair value. The carrying values and fair values of financial instruments are summarized below: September 30, 2017 December 31, 2016 Carrying Fair Value Carrying Fair Value (in thousands) Assets Available-for-sale: Fixed maturity securities $ 1,016,818 $ 1,016,818 $ 941,077 $ 941,077 Equity securities 78,705 78,705 76,401 76,401 Trading: Fixed maturity securities 3,812 3,812 5,063 5,063 Bank loan participations held-for-investment 245,741 242,164 203,526 203,123 Cash and cash equivalents 106,500 106,500 109,784 109,784 Short-term investments 42,331 42,331 50,844 50,844 Other invested assets – notes receivable 10,188 12,033 4,500 6,008 Liabilities Senior debt 88,300 85,706 88,300 85,404 Junior subordinated debt 104,055 109,384 104,055 99,397 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 September 30, 2017 and December 31, 2016 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 September 30, 2017 and December 31, 2016 , respectively. The fair values of bank loan participations held-for-investment, senior debt, and junior subordinated debt at September 30, 2017 and December 31, 2016 were determined using inputs to the valuation methodology that are unobservable (Level 3).

Capital Stock and Equity Awards

Capital Stock and Equity Awards	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Capital Stock and Equity Awards	Capital Stock and Equity Awards The Company issued 325,090 common shares in the nine months ended September 30, 2017 with 300,168 new shares related to stock option exercises and 24,922 new shares related to vesting of RSUs. The total common shares outstanding increased from 29,257,566 at December 31, 2016 to 29,582,656 at September 30, 2017 . The Company declared the following dividends during the first nine months of 2017 and 2016: Date of Declaration Dividend per Common Share Payable to Shareholders of Record on Payment Date Total Amount 2017 February 14, 2017 $ 0.30 March 13, 2017 March 31, 2017 $ 8.9 million May 2, 2017 $ 0.30 June 12, 2017 June 30, 2017 $ 8.9 million August 1, 2017 $ 0.30 September 11, 2017 September 29, 2017 $ 8.9 million $ 0.90 $ 26.7 million 2016 February 16, 2016 $ 0.20 March 14, 2016 March 28, 2016 $ 5.8 million May 3, 2016 $ 0.20 June 13, 2016 June 30, 2016 $ 5.9 million August 3, 2016 $ 0.20 September 12, 2016 September 30, 2016 $ 5.9 million $ 0.60 $ 17.6 million 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 under such plan. Employees are eligible to receive non-qualified stock options, incentive stock options, share appreciation rights, performance shares, restricted shares, restricted share units (“RSUs”), and other awards under the 2014 LTIP. In May 2017, the Company's shareholders approved an amendment to the 2014 LTIP to increase the number of common shares authorized for issuance by 1,000,000 , with only 500,000 of such additional shares to be available for issuance as awards that are not share appreciation rights or share option awards. The maximum number of shares available for issuance under the 2014 LTIP is 4,171,150 , and at September 30, 2017 , 1,880,013 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, restricted share units, and other awards under the 2014 Director Plan. The maximum number of shares available for issuance under the 2014 Director Plan is 50,000 , and at September 30, 2017 , 32,994 shares are available for grant. The Board of Directors has granted awards under the 2014 LTIP and 2014 Director Plan to the Company’s employees and directors. Non-qualified stock options granted under the 2014 LTIP vest over a three year period. RSUs granted under the 2014 LTIP and 2014 Director Plan vest over one to five year periods, depending upon the award. 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) following a Change in Control as defined in the applicable plans. Options The following table summarizes the option activity: Nine Months Ended September 30, 2017 2016 Shares Weighted- Shares Weighted- Outstanding: Beginning of period 2,234,699 $ 22.84 2,058,085 $ 18.11 Granted 205,244 $ 42.24 706,203 $ 32.07 Exercised (735,587 ) $ 18.00 (256,916 ) $ 15.92 Forfeited (62,489 ) $ 30.80 (33,039 ) $ 27.68 End of period 1,641,867 $ 27.13 2,474,333 $ 22.19 Exercisable, end of period 699,922 $ 22.63 992,643 $ 17.04 RSUs The following table summarizes the RSU activity: Nine Months Ended September 30, 2017 2016 Shares Weighted- Shares Weighted- Unvested, beginning of period 196,800 $ 24.38 234,922 $ 21.00 Granted 119,312 $ 42.19 60,291 $ 32.03 Vested (39,113 ) $ 32.01 — $ — Forfeited (22,188 ) $ 26.06 — $ — Unvested, end of period 254,811 $ 31.40 295,213 $ 23.25 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: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Share based compensation expense $ 1,760 $ 1,520 $ 5,338 $ 4,207 U.S. tax benefit on share based compensation expense 467 425 1,413 1,182 As of September 30, 2017 , the Company had $8.5 million of unrecognized share based compensation expense expected to be charged to earnings over a weighted-average period of 1.9 years. The weighted-average remaining contractual life of the options outstanding and options exercisable was 4.7 years and 4.0 years, respectively.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On November 1, 2017 , the Board of Directors declared a cash dividend of $0.30 per common share and a special cash dividend of $0.50 per common share. Both dividends are payable on December 28, 2017 to shareholders of record on December 15, 2017 .

Accounting Policies (Policies)

Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements and notes have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and do not contain all of the information and footnotes required by U.S. GAAP for complete financial statements. The condensed consolidated financial statements include the results of the Company and its subsidiaries from their respective dates of inception or acquisition, as applicable. Readers are urged to review the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 for a more complete description of the Company’s business and accounting policies. In the opinion of management, all adjustments necessary for a fair presentation of the condensed consolidated financial statements have been included. Such adjustments consist only of normal recurring items. Interim results are not necessarily indicative of results of operations for the full year. The consolidated balance sheet as of December 31, 2016 was derived from the Company’s audited annual consolidated financial statements. Intercompany transactions and balances have been eliminated.
Estimates and Assumptions	Estimates and Assumptions Preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying disclosures. Those estimates are inherently subject to change, and actual results may ultimately differ from those estimates.
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 the 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 condensed 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.
Income Tax Expense	Income Tax Expense Our effective tax rate fluctuates from period to period based on the relative mix of income reported by country and the respective tax rates imposed by each tax jurisdiction. For the three months ended September 30, 2017 and 2016 , our U.S. federal income tax expense was 23.8% and 4.1% of income before taxes, respectively ( 11.8% and 6.5% for the nine months ended September 30, 2017 and 2016 , respectively). The catastrophe losses this quarter reduced underwriting income in both the Excess and Surplus Lines and the Casualty Reinsurance segments and this caused a higher proportion of the Group's income to be taxed at a higher rate applicable to earnings in the United States. For U.S.-sourced income, the Company’s U.S. federal income tax expense differs from the amounts computed by applying the federal statutory income tax rate to income before taxes due primarily to interest income on tax-advantaged state and municipal securities (state and municipal securities represent 12.2% and 10.0% of our available-for-sale securities at September 30, 2017 and 2016 , respectively), dividends received income, and excess tax benefits on share based compensation.
Adopted Accounting Standards	Adopted Accounting Standards Effective January 1, 2017, the Company adopted Accounting Standards Update (“ASU”) 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting using the prospective method. The guidance requires that all tax effects related to share-based payments be made through the income statement at the time of settlement as opposed to excess tax benefits being recognized in additional paid-in capital under the previous guidance . The ASU also removes the requirement to delay recognition of a tax benefit until it reduces current taxes payable. Additionally, all tax related cash flows resulting from share-based payments are now reported as operating activities on the statement of cash flows, a change from the previous requirement to present tax benefits as an inflow from financing activities and an outflow from operating activities. For the nine months ended September 30, 2016 , net cash provided by operating activities increased by $1.2 million and net cash used in financing activities increased by $1.2 million for the adoption of ASU 2016-09. The Company has elected to recognize forfeitures as they occur in accordance with ASU 2016-09. The adoption of ASU 2016-09 did not materially impact the Company’s consolidated income statements.
Prospective Accounting Standards	Prospective Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) . The guidance applies to all companies that either enter into contracts with customers to transfer goods or services or enter into contracts for the transfer of nonfinancial assets, unless those contracts are within the scope of other standards, such as insurance contracts. Under this guidance, a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the current guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 becomes effective for the Company during the first quarter of 2018 and must be applied retrospectively. The Company is completing it evaluation of ASU 2014-09 to determine what, if any, impact that adopting this standard will have on reported fee income. As part of this evaluation, the Company is completing a review of its contracts and assessing the impact the new standard will have on its disclosures and internal controls. The Company does not believe adoption will have a material impact on its consolidated financial statements. The Company plans to adopt this ASU using the modified retrospective method, with the cumulative effect of initially applying this update recognized in the first quarter of 2018. The Company is in the process of drafting an updated accounting policy for revenue recognition, evaluating new disclosure requirements and identifying and implementing appropriate changes to its business processes, systems and controls to support recognition and disclosure under the new guidance. In January 2016, the FASB issued ASU 2016-01, Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities . Among other things, this ASU will require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. This ASU is effective for interim and annual reporting periods beginning after December 15, 2017. Upon adoption, a cumulative-effect adjustment to the balance sheet will be made as of the beginning of the fiscal year of adoption. Adoption of this ASU is not expected to have a material impact on the Company's financial position, cash flows, or total comprehensive income, but will have an impact on the Company's results of operations, as changes in fair value of equity instruments will be presented in net income rather than other comprehensive income. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . Under current guidance for lessees, leases are only included on the balance sheet if certain criteria, classifying the agreement as a capital lease, are met. This update will require 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. This ASU is effective for annual and interim reporting periods beginning after December 15, 2018. Early adoption is permitted. Upon adoption, leases will be recognized and measured at the beginning of the earliest period presented using a modified retrospective approach. The Company is currently evaluating ASU 2016-02 to determine the potential impact that adopting this standard will have on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Current GAAP delays the recognition of credit losses until 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 runs through 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. Upon adoption, this ASU will be applied using the modified-retrospective approach, by which a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first reporting period presented. The Company has not yet completed the analysis of how adopting this ASU will affect the Company’s financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments to address the diversity in practice of how certain cash receipts and payments are classified in the statement of cash flows. The update addresses specific issues, including distributions received from equity method investees and the classification of cash receipts and payments that have aspects of more than one class of cash flows. This ASU is effective for annual and interim reporting periods beginning after December 15, 2017. Upon adoption, the update will be applied using the retrospective transition method. The Company does not expect that the adoption of this ASU will have a material impact on its statement of cash flows.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2017
Investments [Abstract]
Schedule of summary of available-for-sale investments	The Company’s available-for-sale investments are summarized as follows: Cost or Gross Gross Fair (in thousands) September 30, 2017 Fixed maturity securities: State and municipal $ 129,786 $ 5,608 $ (416 ) $ 134,978 Residential mortgage-backed 140,053 946 (1,942 ) 139,057 Corporate 415,817 7,490 (1,901 ) 421,406 Commercial mortgage and asset-backed 176,952 984 (489 ) 177,447 Obligations of U.S. government corporations and agencies 62,435 37 (97 ) 62,375 U.S. Treasury securities and obligations guaranteed by the U.S. government 79,647 77 (244 ) 79,480 Redeemable preferred stock 2,025 50 — 2,075 Total fixed maturity securities 1,006,715 15,192 (5,089 ) 1,016,818 Equity securities 72,102 8,116 (1,513 ) 78,705 Total investments available-for-sale $ 1,078,817 $ 23,308 $ (6,602 ) $ 1,095,523 December 31, 2016 Fixed maturity securities: State and municipal $ 101,793 $ 5,032 $ (984 ) $ 105,841 Residential mortgage-backed 152,703 1,070 (2,975 ) 150,798 Corporate 379,727 4,382 (5,661 ) 378,448 Commercial mortgage and asset-backed 167,967 906 (826 ) 168,047 Obligations of U.S. government corporations and agencies 64,823 276 (85 ) 65,014 U.S. Treasury securities and obligations guaranteed by the U.S. government 71,174 131 (185 ) 71,120 Redeemable preferred stock 2,025 — (216 ) 1,809 Total fixed maturity securities 940,212 11,797 (10,932 ) 941,077 Equity securities 74,553 4,503 (2,655 ) 76,401 Total investments available-for-sale $ 1,014,765 $ 16,300 $ (13,587 ) $ 1,017,478
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 September 30, 2017 are summarized, by contractual maturity, as follows: Cost or Fair (in thousands) One year or less $ 117,434 $ 117,483 After one year through five years 253,240 255,514 After five years through ten years 192,269 193,760 After ten years 124,742 131,482 Residential mortgage-backed 140,053 139,057 Commercial mortgage and asset-backed 176,952 177,447 Redeemable preferred stock 2,025 2,075 Total $ 1,006,715 $ 1,016,818
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) September 30, 2017 Fixed maturity securities: State and municipal $ 27,813 $ (220 ) $ 5,371 $ (196 ) $ 33,184 $ (416 ) Residential mortgage-backed 81,667 (882 ) 30,486 (1,060 ) 112,153 (1,942 ) Corporate 106,427 (998 ) 31,522 (903 ) 137,949 (1,901 ) Commercial mortgage and asset-backed 46,526 (288 ) 11,861 (201 ) 58,387 (489 ) Obligations of U.S. government corporations and agencies 52,157 (97 ) — — 52,157 (97 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 60,192 (243 ) 2,223 (1 ) 62,415 (244 ) Total fixed maturity securities 374,782 (2,728 ) 81,463 (2,361 ) 456,245 (5,089 ) Equity securities 3,913 (68 ) 8,847 (1,445 ) 12,760 (1,513 ) Total investments available-for-sale $ 378,695 $ (2,796 ) $ 90,310 $ (3,806 ) $ 469,005 $ (6,602 ) December 31, 2016 Fixed maturity securities: State and municipal $ 28,398 $ (984 ) $ — $ — $ 28,398 $ (984 ) Residential mortgage-backed 93,242 (1,548 ) 32,330 (1,427 ) 125,572 (2,975 ) Corporate 199,841 (4,212 ) 8,477 (1,449 ) 208,318 (5,661 ) Commercial mortgage and asset-backed 47,990 (799 ) 7,195 (27 ) 55,185 (826 ) Obligations of U.S. government corporations and agencies 50,573 (85 ) — — 50,573 (85 ) U.S. Treasury securities and obligations guaranteed by the U.S. government 48,989 (185 ) — — 48,989 (185 ) Redeemable preferred stock 1,809 (216 ) — — 1,809 (216 ) Total fixed maturity securities 470,842 (8,029 ) 48,002 (2,903 ) 518,844 (10,932 ) Equity securities 21,345 (1,071 ) 6,558 (1,584 ) 27,903 (2,655 ) Total investments available-for-sale $ 492,187 $ (9,100 ) $ 54,560 $ (4,487 ) $ 546,747 $ (13,587 )
Schedule of summary of realized gains and losses	The Company’s realized gains and losses are summarized as follows: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Fixed maturity securities: Gross realized gains $ 378 $ 70 $ 734 $ 1,479 Gross realized losses (4 ) — (331 ) (2 ) 374 70 403 1,477 Bank loan participations: Gross realized gains 341 273 1,948 1,466 Gross realized losses (839 ) (1,308 ) (1,528 ) (1,741 ) (498 ) (1,035 ) 420 (275 ) Equity securities: Gross realized gains — 1,174 409 1,174 Gross realized losses (45 ) — (45 ) — (45 ) 1,174 364 1,174 Short-term investments and other: Gross realized gains 1 2 1 3 Gross realized losses (3 ) (1 ) (5 ) (3 ) (2 ) 1 (4 ) — Total $ (171 ) $ 210 $ 1,183 $ 2,376
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. Investment Income Carrying Value September 30, December 31, Three Months Ended Nine Months Ended 2017 2016 2017 2016 2017 2016 (in thousands) Renewable energy LLCs (a) $ 31,264 $ 27,067 $ 1,516 $ 2,745 $ 8,631 $ 1,976 Renewable energy notes receivable ( b) 5,688 — 238 — 287 450 Limited partnerships (c) 24,753 23,852 477 1,948 1,562 3,784 Bank holding companies (d) 4,500 4,500 85 86 257 257 Total other invested assets $ 66,205 $ 55,419 $ 2,316 $ 4,779 $ 10,737 $ 6,467 (a) The Company’s Corporate and Other segment owns equity interests ranging from 2.6% to 32.8% 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 affiliate of the Company’s largest shareholder and the Company’s 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 $4.4 million and $2.4 million in the nine months ended September 30, 2017 and 2016 , respectively. (b) The Company has invested in notes receivable for renewable energy projects. In June 2017, the Company invested $5.7 million in a note with an affiliate of the Company’s largest shareholder. Interest on the note, which matures in 2021, is fixed at 15.0% . The Company is committed to investing another $3.1 million in the note and commitment fees of 2.5% are earned on the unfunded commitment. Interest income on the note was $238,000 and $287,000 for the three and nine months ended September 30, 2017 , respectively. The Company’s Chairman and Chief Executive Officer and one of the Company’s directors are also lenders on this project. In May 2016, the outstanding principal on a $6.5 million note was fully repaid. Income prior to repayment of the note was $450,000 in the nine months ended September 30, 2016 . This note was also with an affiliate of the Company's largest shareholder. (c) The Company owns investments in limited partnerships that invest in concentrated portfolios of publicly-traded small cap equities, loans of middle market private equity sponsored companies, and equity tranches of collateralized loan obligations (CLOs). Income f rom 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 $2.9 million at September 30, 2017 . The Company recognized investment income of $246,000 and $178,000 on the investment for the nine months ended September 30, 2017 and 2016 , respectively. The Company’s Excess and Surplus Lines segment holds investments in limited partnerships of $21.9 million at September 30, 2017 . Investment income of $1.3 million and $3.6 million was recognized on the investments for the nine months ended September 30, 2017 and 2016 , respectively. At September 30, 2017 , the Company’s Excess and Surplus Lines segment has an outstanding commitment to invest another $625,000 in a limited partnership that invests in loans of middle market private equity sponsored companies. (d) The Company holds $4.5 million of subordinated notes issued by a bank holding company. Interest on the notes, which mature on August 12, 2023, is fixed at 7.6% per annum. Interest income on the notes was $257,000 in both nine months ended September 30, 2017 and 2016 . The Company’s Chairman and Chief Executive Officer was previously the Lead Independent Director of the bank holding company and an investor in the bank holding company. Additionally, one of the Company’s directors was an investor in the bank holding company and is currently a lender to the bank holding company.

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2017
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: September 30, 2017 December 31, 2016 Life Gross Accumulated Gross Accumulated ($ in thousands) Intangible Assets Trademarks Indefinite $ 22,200 $ — $ 22,200 $ — Insurance licenses and authorities Indefinite 9,164 — 9,164 — Identifiable intangibles not subject to amortization 31,364 — 31,364 — Broker relationships 24.6 11,611 4,491 11,611 4,044 Identifiable intangible assets subject to amortization 11,611 4,491 11,611 4,044 $ 42,975 $ 4,491 $ 42,975 $ 4,044

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [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 condensed consolidated financial statements: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands, except share and per share amounts) Net income to shareholders $ 10,351 $ 21,366 $ 43,342 $ 48,799 Weighted average common shares outstanding: Basic 29,524,243 29,101,550 29,407,762 29,030,284 Common share equivalents 695,834 833,602 877,971 804,402 Diluted 30,220,077 29,935,152 30,285,733 29,834,686 Earnings per share: Basic $ 0.35 $ 0.73 $ 1.47 $ 1.68 Common share equivalents (0.01 ) (0.02 ) (0.04 ) (0.04 ) Diluted $ 0.34 $ 0.71 $ 1.43 $ 1.64

Reserve for Losses and Loss A24

Reserve for Losses and Loss Adjustment Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
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 condensed consolidated balance sheets: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Reserve for losses and loss adjustment expenses net of reinsurance recoverables at beginning of period $ 839,508 $ 689,631 $ 761,128 $ 653,534 Add: Incurred losses and loss adjustment expenses net of reinsurance: Current year 158,009 88,659 396,161 248,239 Prior years (7,564 ) (5,333 ) (9,263 ) (14,748 ) Total incurred losses and loss and adjustment expenses 150,445 83,326 386,898 233,491 Deduct: Loss and loss adjustment expense payments net of reinsurance: Current year 21,305 10,734 38,911 21,624 Prior years 65,349 43,847 205,816 147,025 Total loss and loss adjustment expense payments 86,654 54,581 244,727 168,649 Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period 903,299 718,376 903,299 718,376 Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period 283,949 156,286 283,949 156,286 Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period $ 1,187,248 $ 874,662 $ 1,187,248 $ 874,662

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of components of comprehensive income	The following table summarizes the components of other comprehensive income: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Unrealized gains (losses) arising during the period, before U.S. income taxes $ 909 $ (802 ) $ 14,760 $ 31,662 U.S. income taxes 21 (38 ) (2,771 ) (3,115 ) Unrealized gains (losses) arising during the period, net of U.S. income taxes 930 (840 ) 11,989 28,547 Less reclassification adjustment: Net realized investment gains 329 1,243 767 2,651 U.S. income tax expenses (115 ) (411 ) (236 ) (844 ) Reclassification adjustment for investment gains realized in net income 214 832 531 1,807 Other comprehensive income (loss) $ 716 $ (1,672 ) $ 11,458 $ 26,740

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Schedule of summary of company's segment results	The following table summarizes the Company’s segment results: Excess and Specialty Casualty Corporate Total (in thousands) Three Months Ended September 30, 2017 Gross written premiums $ 140,425 $ 84,838 $ 113,088 $ — $ 338,351 Net earned premiums 123,606 19,324 59,186 — 202,116 Underwriting profit (loss) of insurance segments 9,946 851 (2,933 ) — 7,864 Net investment income 3,727 626 8,590 1,937 14,880 Interest expense — — — 2,304 2,304 Segment revenues 131,033 19,992 67,860 1,981 220,866 Segment goodwill 181,831 — — — 181,831 Segment assets 821,668 405,209 1,372,234 122,541 2,721,652 Three Months Ended September 30, 2016 Gross written premiums $ 99,882 $ 56,119 $ 104,165 $ — $ 260,166 Net earned premiums 81,672 13,204 38,273 — 133,149 Underwriting profit of insurance segments 12,408 702 133 — 13,243 Net investment income 5,236 647 7,085 2,829 15,797 Interest expense — — — 2,079 2,079 Segment revenues 88,671 13,890 44,808 3,996 151,365 Segment goodwill 181,831 — — — 181,831 Segment assets 728,231 261,063 1,258,522 100,095 2,347,911 Nine Months Ended September 30, 2017 Gross written premiums $ 387,424 $ 234,073 $ 222,508 $ — $ 844,005 Net earned premiums 334,723 53,337 152,820 — 540,880 Underwriting profit (loss) of insurance segments 30,475 2,246 (3,863 ) — 28,858 Net investment income 10,751 1,893 23,100 9,583 45,327 Interest expense — — — 6,651 6,651 Segment revenues 357,607 55,351 176,580 10,124 599,662 Segment goodwill 181,831 — — — 181,831 Segment assets 821,668 405,209 1,372,234 122,541 2,721,652 Nine Months Ended September 30, 2016 Gross written premiums $ 279,417 $ 119,007 $ 165,484 $ — $ 563,908 Net earned premiums 217,742 36,816 114,276 — 368,834 Underwriting profit of insurance segments 31,395 1,302 673 — 33,370 Net investment income 13,601 1,898 20,248 2,875 38,622 Interest expense — — — 6,294 6,294 Segment revenues 239,401 39,266 134,420 4,118 417,205 Segment goodwill 181,831 — — — 181,831 Segment assets 728,231 261,063 1,258,522 100,095 2,347,911
Schedule of underwriting profit of operating segments by individual segment and reconciliation to consolidated income before taxes	The following table reconciles the underwriting profit (loss) of the operating segments by individual segment to consolidated income before taxes: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Underwriting profit (loss) of the insurance segments: Excess and Surplus Lines $ 9,946 $ 12,408 $ 30,475 $ 31,395 Specialty Admitted Insurance 851 702 2,246 1,302 Casualty Reinsurance (2,933 ) 133 (3,863 ) 673 Total underwriting profit of insurance segments 7,864 13,243 28,858 33,370 Other operating expenses of the Corporate and Other segment (6,507 ) (4,870 ) (19,063 ) (15,597 ) Underwriting profit 1,357 8,373 9,795 17,773 Net investment income 14,880 15,797 45,327 38,622 Net realized investment (losses) gains (171 ) 210 1,183 2,376 Amortization of intangible assets (149 ) (149 ) (447 ) (447 ) Other income and expenses (24 ) 123 (81 ) 175 Interest expense (2,304 ) (2,079 ) (6,651 ) (6,294 ) Income before taxes $ 13,589 $ 22,275 $ 49,126 $ 52,205

Other Operating Expenses and 27

Other Operating Expenses and Other Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
Other Operating Expenses And Other Expenses [Abstract]
Schedule of other operating expenses	Other operating expenses consist of the following: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Amortization of policy acquisition costs $ 35,311 $ 24,761 $ 94,563 $ 70,552 Other underwriting expenses of the operating segments 12,442 13,948 42,563 38,583 Other operating expenses of the Corporate and Other segment 6,507 4,870 19,063 15,597 Total $ 54,260 $ 43,579 $ 156,189 $ 124,732

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 are summarized below: Fair Value Measurements Using Quoted Prices Significant Significant Total (in thousands) Available-for-sale securities: Fixed maturity securities: State and municipal $ — $ 134,978 $ — $ 134,978 Residential mortgage-backed — 139,057 — 139,057 Corporate — 421,406 — 421,406 Commercial mortgage and asset-backed — 172,447 5,000 177,447 Obligations of U.S. government corporations and agencies — 62,375 — 62,375 U.S. Treasury securities and obligations guaranteed by the U.S. government 78,864 616 — 79,480 Redeemable preferred stock — 2,075 — 2,075 Total fixed maturity securities 78,864 932,954 5,000 1,016,818 Equity securities: Preferred stock — 66,833 — 66,833 Common stock 11,138 734 — 11,872 Total equity securities 11,138 67,567 — 78,705 Total available-for-sale securities $ 90,002 $ 1,000,521 $ 5,000 $ 1,095,523 Trading securities: Fixed maturity securities $ — $ 3,812 $ — $ 3,812 Short-term investments $ 1,000 $ 41,331 $ — $ 42,331 Assets measured at fair value on a recurring basis as of December 31, 2016 are summarized below: Fair Value Measurements Using Quoted Prices Significant Significant Total (in thousands) Available-for-sale securities: Fixed maturity securities: State and municipal $ — $ 105,841 $ — $ 105,841 Residential mortgage-backed — 150,798 — 150,798 Corporate — 378,448 — 378,448 Commercial mortgage and asset-backed — 163,047 5,000 168,047 Obligations of U.S. government corporations and agencies — 65,014 — 65,014 U.S. Treasury securities and obligations guaranteed by the U.S. government 70,465 655 — 71,120 Redeemable preferred stock — 1,809 — 1,809 Total fixed maturity securities 70,465 865,612 5,000 941,077 Equity securities: Preferred stock — 64,827 — 64,827 Common stock 10,840 734 — 11,574 Total equity securities 10,840 65,561 — 76,401 Total available-for-sale securities $ 81,305 $ 931,173 $ 5,000 $ 1,017,478 Trading securities: Fixed maturity securities $ 1,250 $ 3,813 $ — $ 5,063 Short-term investments $ 1,100 $ 49,744 $ — $ 50,844
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 Significant Significant Total (in thousands) September 30, 2017 Bank loan participations held-for-investment $ — $ — $ 2,445 $ 2,445 December 31, 2016 Bank loan participations held-for-investment $ — $ — $ 4,849 $ 4,849
Schedule of carrying value and fair value	The carrying values and fair values of financial instruments are summarized below: September 30, 2017 December 31, 2016 Carrying Fair Value Carrying Fair Value (in thousands) Assets Available-for-sale: Fixed maturity securities $ 1,016,818 $ 1,016,818 $ 941,077 $ 941,077 Equity securities 78,705 78,705 76,401 76,401 Trading: Fixed maturity securities 3,812 3,812 5,063 5,063 Bank loan participations held-for-investment 245,741 242,164 203,526 203,123 Cash and cash equivalents 106,500 106,500 109,784 109,784 Short-term investments 42,331 42,331 50,844 50,844 Other invested assets – notes receivable 10,188 12,033 4,500 6,008 Liabilities Senior debt 88,300 85,706 88,300 85,404 Junior subordinated debt 104,055 109,384 104,055 99,397

Capital Stock and Equity Awar29

Capital Stock and Equity Awards (Tables)	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Schedule of dividends	The Company declared the following dividends during the first nine months of 2017 and 2016: Date of Declaration Dividend per Common Share Payable to Shareholders of Record on Payment Date Total Amount 2017 February 14, 2017 $ 0.30 March 13, 2017 March 31, 2017 $ 8.9 million May 2, 2017 $ 0.30 June 12, 2017 June 30, 2017 $ 8.9 million August 1, 2017 $ 0.30 September 11, 2017 September 29, 2017 $ 8.9 million $ 0.90 $ 26.7 million 2016 February 16, 2016 $ 0.20 March 14, 2016 March 28, 2016 $ 5.8 million May 3, 2016 $ 0.20 June 13, 2016 June 30, 2016 $ 5.9 million August 3, 2016 $ 0.20 September 12, 2016 September 30, 2016 $ 5.9 million $ 0.60 $ 17.6 million
Schedule of summary of option activity	The following table summarizes the option activity: Nine Months Ended September 30, 2017 2016 Shares Weighted- Shares Weighted- Outstanding: Beginning of period 2,234,699 $ 22.84 2,058,085 $ 18.11 Granted 205,244 $ 42.24 706,203 $ 32.07 Exercised (735,587 ) $ 18.00 (256,916 ) $ 15.92 Forfeited (62,489 ) $ 30.80 (33,039 ) $ 27.68 End of period 1,641,867 $ 27.13 2,474,333 $ 22.19 Exercisable, end of period 699,922 $ 22.63 992,643 $ 17.04
Schedule of summary of RSU activity	The following table summarizes the RSU activity: Nine Months Ended September 30, 2017 2016 Shares Weighted- Shares Weighted- Unvested, beginning of period 196,800 $ 24.38 234,922 $ 21.00 Granted 119,312 $ 42.19 60,291 $ 32.03 Vested (39,113 ) $ 32.01 — $ — Forfeited (22,188 ) $ 26.06 — $ — Unvested, end of period 254,811 $ 31.40 295,213 $ 23.25
Schedule of summary of amount of expense and related tax benefit	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: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (in thousands) Share based compensation expense $ 1,760 $ 1,520 $ 5,338 $ 4,207 U.S. tax benefit on share based compensation expense 467 425 1,413 1,182

Accounting Policies - Narrative

Accounting Policies - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)company	Sep. 30, 2016	Sep. 30, 2017USD ($)company	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of insurance companies based in the United States | company	6		6
Investment in variable interest entities	$ 31.3		$ 31.3		$ 27.1
Effective U.S. federal income tax expense rate	23.80%	4.10%	11.80%	6.50%
Percentage of available for sale securities	12.20%	10.00%	12.20%	10.00%
Accounting Standards Update ("ASU") 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in net cash provided by operating activities				$ 1.2
Increase in net cash used in financing activities				$ 1.2

Investments - Narrative (Detail

Investments - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017USD ($)issuerloan	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)issuerloan	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)loan	Dec. 31, 2015USD ($)
Gain (Loss) on Investments [Line Items]
Number of available-for-sale securities held in an unrealized loss position | issuer	146		146
Total fair value of unrealized loss position securities	$ 469,005		$ 469,005		$ 546,747
Total gross unrealized losses of unrealized loss position securities	$ 6,602		$ 6,602		13,587
Percentage of available for sale securities	12.20%	10.00%	12.20%	10.00%
Fair value	$ 1,095,523		$ 1,095,523		1,017,478
Unpaid principal on impaired loans	4,000		4,000		7,600
Carrying value of loan	245,741		245,741		203,526
Allowance for credit losses on impaired loans	1,500	$ 2,000	$ 1,500	$ 2,000	$ 943	$ 4,300
Number of impaired loans held | loan			4		5
Carrying value of impaired loans	2,400		$ 2,400		$ 6,500
Average recorded investment in impaired bank loans			4,500	8,000
Investment income during period loans were impaired			231	237
Net realized gain (loss) on changes in fair value of impaired bank loans	729	663	594	53
Net trading gains (losses) still held	2
Net trading gains (losses)			0
Carrying value of collateralized loan obligation held	5,000		5,000
Net realized investment (losses) gains	(171)	210	1,183	2,376
Investment income	2,316	4,779	10,737	6,467
Bank Holding Company
Gain (Loss) on Investments [Line Items]
Net realized investment (losses) gains			409
Investment income				266
Investment in certificate of deposit			1,000
Interest income			2	3
Fixed maturity securities
Gain (Loss) on Investments [Line Items]
Total fair value of unrealized loss position securities	456,245		456,245		518,844
Total gross unrealized losses of unrealized loss position securities	5,089		5,089		10,932
Fair value	1,016,818		1,016,818		941,077
Net realized investment (losses) gains	374	$ 70	403	$ 1,477
Puerto Rico loan
Gain (Loss) on Investments [Line Items]
Unpaid principal on impaired loans	807		807		2,000
Carrying value of loan	0		0		1,700
Allowance for credit losses on impaired loans					177
Oil and gas companies loan
Gain (Loss) on Investments [Line Items]
Unpaid principal on impaired loans	2,500		2,500		2,200
Carrying value of loan	9,700		9,700
Allowance for credit losses on impaired loans	$ 500		$ 500		$ 500
Number of loans | loan	4		4
Bank loan participations gross unrealized losses	$ 1,900		$ 1,900
Number of impaired loans held | loan			2		1
Carrying value of impaired loans	1,900		$ 1,900		$ 1,600
Non-energy sector loan
Gain (Loss) on Investments [Line Items]
Unpaid principal on impaired loans	708		708		3,500
Allowance for credit losses on impaired loans	209		$ 209		$ 221
Number of impaired loans held | loan			1		3
Carrying value of impaired loans	$ 500		$ 500		$ 3,200
BBB- or better | Fixed maturity securities
Gain (Loss) on Investments [Line Items]
Percentage of available for sale securities	99.10%		99.10%
Fair value	$ 9,000		$ 9,000
Aggregate net unrealized gain	$ 248

Investments - Schedule of Avail

Investments - Schedule of Available-for-Sale Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 1,078,817	$ 1,014,765
Gross Unrealized Gains	23,308	16,300
Gross Unrealized Losses	(6,602)	(13,587)
Fair Value	1,095,523	1,017,478
Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,006,715	940,212
Gross Unrealized Gains	15,192	11,797
Gross Unrealized Losses	(5,089)	(10,932)
Fair Value	1,016,818	941,077
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	129,786	101,793
Gross Unrealized Gains	5,608	5,032
Gross Unrealized Losses	(416)	(984)
Fair Value	134,978	105,841
Residential mortgage-backed
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	140,053	152,703
Gross Unrealized Gains	946	1,070
Gross Unrealized Losses	(1,942)	(2,975)
Fair Value	139,057	150,798
Corporate
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	415,817	379,727
Gross Unrealized Gains	7,490	4,382
Gross Unrealized Losses	(1,901)	(5,661)
Fair Value	421,406	378,448
Commercial mortgage and asset-backed
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	176,952	167,967
Gross Unrealized Gains	984	906
Gross Unrealized Losses	(489)	(826)
Fair Value	177,447	168,047
Obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	62,435	64,823
Gross Unrealized Gains	37	276
Gross Unrealized Losses	(97)	(85)
Fair Value	62,375	65,014
U.S. Treasury securities and obligations guaranteed by the U.S. government
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	79,647	71,174
Gross Unrealized Gains	77	131
Gross Unrealized Losses	(244)	(185)
Fair Value	79,480	71,120
Redeemable preferred stock
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,025	2,025
Gross Unrealized Gains	50	0
Gross Unrealized Losses	0	(216)
Fair Value	2,075	1,809
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	72,102	74,553
Gross Unrealized Gains	8,116	4,503
Gross Unrealized Losses	(1,513)	(2,655)
Fair Value	$ 78,705	$ 76,401

Investments - Schedule of Contr

Investments - Schedule of Contract Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Cost or Amortized Cost
One year or less	$ 117,434
After one year through five years	253,240
After five years through ten years	192,269
After ten years	124,742
Residential mortgage-backed	140,053
Commercial mortgage and asset-backed	176,952
Redeemable preferred stock	2,025
Total	1,006,715	$ 940,212
Fair Value
One year or less	117,483
After one year through five years	255,514
After five years through ten years	193,760
After ten years	131,482
Residential mortgage-backed	139,057
Commercial mortgage and asset-backed	177,447
Redeemable preferred stock	2,075
Total	$ 1,016,818	$ 941,077

Investments - Schedule of Gross

Investments - Schedule of Gross Unrealized Losses and Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 378,695	$ 492,187
Less Than 12 Months, Gross Unrealized Losses	(2,796)	(9,100)
12 Months or More, Fair Value	90,310	54,560
12 Months or More, Gross Unrealized Losses	(3,806)	(4,487)
Total, Fair Value	469,005	546,747
Total, Gross Unrealized Losses	(6,602)	(13,587)
Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	374,782	470,842
Less Than 12 Months, Gross Unrealized Losses	(2,728)	(8,029)
12 Months or More, Fair Value	81,463	48,002
12 Months or More, Gross Unrealized Losses	(2,361)	(2,903)
Total, Fair Value	456,245	518,844
Total, Gross Unrealized Losses	(5,089)	(10,932)
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	27,813	28,398
Less Than 12 Months, Gross Unrealized Losses	(220)	(984)
12 Months or More, Fair Value	5,371	0
12 Months or More, Gross Unrealized Losses	(196)	0
Total, Fair Value	33,184	28,398
Total, Gross Unrealized Losses	(416)	(984)
Residential mortgage-backed
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	81,667	93,242
Less Than 12 Months, Gross Unrealized Losses	(882)	(1,548)
12 Months or More, Fair Value	30,486	32,330
12 Months or More, Gross Unrealized Losses	(1,060)	(1,427)
Total, Fair Value	112,153	125,572
Total, Gross Unrealized Losses	(1,942)	(2,975)
Corporate
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	106,427	199,841
Less Than 12 Months, Gross Unrealized Losses	(998)	(4,212)
12 Months or More, Fair Value	31,522	8,477
12 Months or More, Gross Unrealized Losses	(903)	(1,449)
Total, Fair Value	137,949	208,318
Total, Gross Unrealized Losses	(1,901)	(5,661)
Commercial mortgage and asset-backed
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	46,526	47,990
Less Than 12 Months, Gross Unrealized Losses	(288)	(799)
12 Months or More, Fair Value	11,861	7,195
12 Months or More, Gross Unrealized Losses	(201)	(27)
Total, Fair Value	58,387	55,185
Total, Gross Unrealized Losses	(489)	(826)
Obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	52,157	50,573
Less Than 12 Months, Gross Unrealized Losses	(97)	(85)
12 Months or More, Fair Value	0	0
12 Months or More, Gross Unrealized Losses	0	0
Total, Fair Value	52,157	50,573
Total, Gross Unrealized Losses	(97)	(85)
U.S. Treasury securities and obligations guaranteed by the U.S. government
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	60,192	48,989
Less Than 12 Months, Gross Unrealized Losses	(243)	(185)
12 Months or More, Fair Value	2,223	0
12 Months or More, Gross Unrealized Losses	(1)	0
Total, Fair Value	62,415	48,989
Total, Gross Unrealized Losses	(244)	(185)
Redeemable preferred stock
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value		1,809
Less Than 12 Months, Gross Unrealized Losses		(216)
12 Months or More, Fair Value		0
12 Months or More, Gross Unrealized Losses		0
Total, Fair Value		1,809
Total, Gross Unrealized Losses		(216)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	3,913	21,345
Less Than 12 Months, Gross Unrealized Losses	(68)	(1,071)
12 Months or More, Fair Value	8,847	6,558
12 Months or More, Gross Unrealized Losses	(1,445)	(1,584)
Total, Fair Value	12,760	27,903
Total, Gross Unrealized Losses	$ (1,513)	$ (2,655)

Investments - Summary of Realiz

Investments - Summary of Realized Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of Available-for-sale Securities [Line Items]
Net realized investment gains	$ (171)	$ 210	$ 1,183	$ 2,376
Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	378	70	734	1,479
Gross realized losses	(4)	0	(331)	(2)
Net realized investment gains	374	70	403	1,477
Bank loan participations
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	341	273	1,948	1,466
Gross realized losses	(839)	(1,308)	(1,528)	(1,741)
Net realized investment gains	(498)	(1,035)	420	(275)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	0	1,174	409	1,174
Gross realized losses	(45)	0	(45)	0
Net realized investment gains	(45)	1,174	364	1,174
Short-term investments and other
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	1	2	1	3
Gross realized losses	(3)	(1)	(5)	(3)
Net realized investment gains	$ (2)	$ 1	$ (4)	$ 0

Investments - Summary of Privat

Investments - Summary of Private Debt and Equity (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Net Investment Income [Line Items]
Net realized gain (loss) on changes in fair value of impaired bank loans		$ 729	$ 663	$ 594	$ 53
Total other invested assets		66,205		66,205		$ 55,419
Investment income		2,316	4,779	10,737	6,467
Maturities and repayments				0	6,500
Renewable energy LLCs
Net Investment Income [Line Items]
Total other invested assets		31,264		31,264		27,067
Investment income		1,516	2,745	8,631	1,976
Renewable energy bridge financing notes
Net Investment Income [Line Items]
Total other invested assets		5,688		5,688		0
Investment income		238	0	$ 287	450
Rate of interest				15.00%
Commitment to invest		$ 3,100		$ 3,100
Commitment fee percentage		2.50%		2.50%
Interest income		$ 238		$ 287
Maturities and repayments	$ 6,500
Limited partnerships
Net Investment Income [Line Items]
Total other invested assets		24,753		24,753		23,852
Investment income		477	1,948	1,562	3,784
Bank holding companies
Net Investment Income [Line Items]
Total other invested assets		4,500		4,500		$ 4,500
Investment income		85	$ 86	257	257
Interest income				$ 257	257
Bank Holding Company
Net Investment Income [Line Items]
Investment income					266
Rate of interest				7.60%
Interest income				$ 2	3
Investment in private subordinated notes				4,500
Corporate and other | Limited partnerships
Net Investment Income [Line Items]
Carrying values of limited partnerships held		2,900		2,900
Investment income (loss)				246	178
Corporate and other | Investment in LLC
Net Investment Income [Line Items]
Cash distributions from LLCs				4,400	2,400
Excess and Surplus Lines | Limited partnerships
Net Investment Income [Line Items]
Carrying values of limited partnerships held		21,900		21,900
Investment income (loss)				1,300	$ 3,600
Commitment to investment in limited partnership		$ 625		$ 625
Minimum | Corporate and other | Investment in LLC
Net Investment Income [Line Items]
Ownership percentage		2.60%		2.60%
Maximum | Corporate and other | Investment in LLC
Net Investment Income [Line Items]
Ownership percentage		32.80%		32.80%

Goodwill and Intangible Asset37

Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 11, 2007
Business Acquisition [Line Items]
Goodwill	$ 181,831	$ 181,831	$ 181,831
James River Group, Inc.
Business Acquisition [Line Items]
Percentage of outstanding shares				100.00%

Goodwill and Intangible Asset38

Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Acquired Intangible Assets [Line Items]
Identifiable intangibles not subject to amortization	$ 31,364	$ 31,364
Identifiable intangible assets subject to amortization
Gross Carrying Amount	11,611	11,611
Accumulated Amortization	4,491	4,044
Total Intangible Assets, Gross	42,975	42,975
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	9,164	9,164
Broker relationships
Identifiable intangible assets subject to amortization
Gross Carrying Amount	11,611	11,611
Accumulated Amortization	$ 4,491	$ 4,044
Life (Years)	24 years 7 months 6 days

Earnings Per Share - Narrative

Earnings Per Share - Narrative (Details) - shares shares in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Stock options and restricted share units ("RSU's")
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities excluded from the calculations of diluted earnings per share	203,758	168,167

Earnings Per Share - Basic and

Earnings Per Share - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income to shareholders	$ 10,351	$ 21,366	$ 43,342	$ 48,799
Weighted average common shares outstanding:
Basic (in shares)	29,524,243	29,101,550	29,407,762	29,030,284
Common share equivalents (in shares)	695,834	833,602	877,971	804,402
Diluted (in shares)	30,220,077	29,935,152	30,285,733	29,834,686
Earnings per share:
Basic (in dollars per share)	$ 0.35	$ 0.73	$ 1.47	$ 1.68
Common share equivalents (in dollars per share)	(0.01)	(0.02)	(0.04)	(0.04)
Diluted (in dollars per share)	$ 0.34	$ 0.71	$ 1.43	$ 1.64

Reserve for Losses and Loss A41

Reserve for Losses and Loss Adjustment Expenses - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses	$ 7,564	$ 5,333	$ 9,263	$ 14,748
Excess and Surplus Lines | Prior accident years | From the 2015 and 2014 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses	5,100
Excess and Surplus Lines | Prior accident years | From the 2013, 2014, and 2015 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses		5,800		13,800
Excess and Surplus Lines | Prior accident years | From the 2014-2016 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses			9,800
Specialty Admitted Insurance | Prior accident years | From the 2015 and 2014 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses	3,000
Specialty Admitted Insurance | Prior accident years | From the 2013, 2014, and 2015 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses		1,600
Specialty Admitted Insurance | Prior accident years | From the 2014-2016 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses			2,100
Specialty Admitted Insurance | Prior accident years | From the 2010-2014 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses				2,500
Casualty Reinsurance | Prior accident years | From the 2013 and 2011 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses	$ (581)
Casualty Reinsurance | Prior accident years | From the 2013 and 2012 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses		$ (2,000)		$ (1,500)
Casualty Reinsurance | Prior accident years | From the 2013-2011 accident years
Favorable development on prior year loss reserves
Reserve for losses and loss adjustment expenses			$ (2,600)

Reserve for Losses and Loss A42

Reserve for Losses and Loss Adjustment Expenses - Reconciliation of Losses and Loss Adjustment Balances (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
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	$ 839,508	$ 689,631	$ 761,128	$ 653,534
Add: Incurred losses and loss adjustment expenses net of reinsurance:
Current year	158,009	88,659	396,161	248,239
Prior years	(7,564)	(5,333)	(9,263)	(14,748)
Total incurred losses and loss and adjustment expenses	150,445	83,326	386,898	233,491
Deduct: Loss and loss adjustment expense payments net of reinsurance:
Current year	21,305	10,734	38,911	21,624
Prior years	65,349	43,847	205,816	147,025
Total loss and loss adjustment expense payments	86,654	54,581	244,727	168,649
Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period	903,299	718,376	903,299	718,376
Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period	283,949	156,286	283,949	156,286	$ 182,737
Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period	$ 1,187,248	$ 874,662	$ 1,187,248	$ 874,662	$ 943,865

Other Comprehensive Income - Su

Other Comprehensive Income - Summary of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gains (losses) arising during the period, before U.S. income taxes	$ 909	$ (802)	$ 14,760	$ 31,662
U.S. income taxes	21	(38)	(2,771)	(3,115)
Unrealized gains (losses) arising during the period, net of U.S. income taxes	930	(840)	11,989	28,547
Less reclassification adjustment:
Net realized investment gains	329	1,243	767	2,651
U.S. income tax expenses	(115)	(411)	(236)	(844)
Reclassification adjustment for investment gains realized in net income	214	832	531	1,807
Other comprehensive income (loss)	$ 716	$ (1,672)	$ 11,458	$ 26,740

Contingent Liabilities - Narrat

Contingent Liabilities - Narrative (Details) $ in Millions	Sep. 30, 2017USD ($)
JRG Reinsurance Company, Ltd. | Letter of credit 100 Million
Contingent Liabilities [Line Items]
Letters of credit facility, amount	$ 100
Amount of letters of credit issued	85.6
Assets deposited for securing letters of credit	95.8
JRG Reinsurance Company, Ltd. | Letter of credit 102.5 Million
Contingent Liabilities [Line Items]
Letters of credit facility, amount	102.5
Amount of letters of credit issued	47.6
Assets deposited for securing letters of credit	61.6
James River Insurance Co
Contingent Liabilities [Line Items]
Total amount deposited in trust accounts	670.1
Third-party Reinsureds | JRG Reinsurance Company, Ltd.
Contingent Liabilities [Line Items]
Total amount deposited in trust accounts	$ 269.8

Segment Information - Narrative

Segment Information - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)segment	Sep. 30, 2016USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			4
Fee income in Excess and Surplus Lines segment	$ 3,900	$ 2,100	$ 12,000	$ 7,200
Catastrophe losses	10,000		10,000
Casualty Reinsurance
Segment Reporting Information [Line Items]
Catastrophe losses	2,700		2,700
Increase (decrease) in underwriting expense	0		2,000
Increase in investment income	480
Excess and Surplus Lines
Segment Reporting Information [Line Items]
Catastrophe losses	7,300		7,300
Increase (decrease) in underwriting expense	$ (1,300)		$ 0

Segment Information - Summary o

Segment Information - Summary of Segment Results (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross written premiums	$ 338,351	$ 260,166	$ 844,005	$ 563,908
Net earned premiums	202,116	133,149	540,880	368,834
Underwriting profit (loss) of insurance segments	7,864	13,243	28,858	33,370
Net investment income	14,880	15,797	45,327	38,622
Interest expense	2,304	2,079	6,651	6,294
Segment revenues	220,866	151,365	599,662	417,205
Segment goodwill	181,831	181,831	181,831	181,831	$ 181,831
Segment assets	2,721,652	2,347,911	2,721,652	2,347,911	$ 2,346,533
Reportable segments | Excess and Surplus Lines
Segment Reporting Information [Line Items]
Gross written premiums	140,425	99,882	387,424	279,417
Net earned premiums	123,606	81,672	334,723	217,742
Underwriting profit (loss) of insurance segments	9,946	12,408	30,475	31,395
Net investment income	3,727	5,236	10,751	13,601
Interest expense	0	0	0	0
Segment revenues	131,033	88,671	357,607	239,401
Segment goodwill	181,831	181,831	181,831	181,831
Segment assets	821,668	728,231	821,668	728,231
Reportable segments | Specialty Admitted Insurance
Segment Reporting Information [Line Items]
Gross written premiums	84,838	56,119	234,073	119,007
Net earned premiums	19,324	13,204	53,337	36,816
Underwriting profit (loss) of insurance segments	851	702	2,246	1,302
Net investment income	626	647	1,893	1,898
Interest expense	0	0	0	0
Segment revenues	19,992	13,890	55,351	39,266
Segment goodwill	0	0	0	0
Segment assets	405,209	261,063	405,209	261,063
Reportable segments | Casualty Reinsurance
Segment Reporting Information [Line Items]
Gross written premiums	113,088	104,165	222,508	165,484
Net earned premiums	59,186	38,273	152,820	114,276
Underwriting profit (loss) of insurance segments	(2,933)	133	(3,863)	673
Net investment income	8,590	7,085	23,100	20,248
Interest expense	0	0	0	0
Segment revenues	67,860	44,808	176,580	134,420
Segment goodwill	0	0	0	0
Segment assets	1,372,234	1,258,522	1,372,234	1,258,522
Corporate and Other | Corporate and other
Segment Reporting Information [Line Items]
Gross written premiums	0	0	0	0
Net earned premiums	0	0	0	0
Underwriting profit (loss) of insurance segments	0	0	0	0
Net investment income	1,937	2,829	9,583	2,875
Interest expense	2,304	2,079	6,651	6,294
Segment revenues	1,981	3,996	10,124	4,118
Segment goodwill	0	0	0	0
Segment assets	$ 122,541	$ 100,095	$ 122,541	$ 100,095

Segment Information - Reconcili

Segment Information - Reconciliation of Operating Segments by Individual Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Total underwriting profit of insurance segments	$ 7,864	$ 13,243	$ 28,858	$ 33,370
Other operating expenses of the Corporate and Other segment	(6,507)	(4,870)	(19,063)	(15,597)
Underwriting profit	1,357	8,373	9,795	17,773
Net investment income	14,880	15,797	45,327	38,622
Net realized investment (losses) gains	(171)	210	1,183	2,376
Amortization of intangible assets	(149)	(149)	(447)	(447)
Other income and expenses	(24)	123	(81)	175
Interest expense	(2,304)	(2,079)	(6,651)	(6,294)
Income before taxes	13,589	22,275	49,126	52,205
Reportable segments | Excess and Surplus Lines
Segment Reporting Information [Line Items]
Total underwriting profit of insurance segments	9,946	12,408	30,475	31,395
Net investment income	3,727	5,236	10,751	13,601
Interest expense	0	0	0	0
Reportable segments | Specialty Admitted Insurance
Segment Reporting Information [Line Items]
Total underwriting profit of insurance segments	851	702	2,246	1,302
Net investment income	626	647	1,893	1,898
Interest expense	0	0	0	0
Reportable segments | Casualty Reinsurance
Segment Reporting Information [Line Items]
Total underwriting profit of insurance segments	(2,933)	133	(3,863)	673
Net investment income	8,590	7,085	23,100	20,248
Interest expense	$ 0	$ 0	$ 0	$ 0

Other Operating Expenses and 48

Other Operating Expenses and Other Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Operating Expenses And Other Expenses [Abstract]
Amortization of policy acquisition costs	$ 35,311	$ 24,761	$ 94,563	$ 70,552
Other underwriting expenses of the operating segments	12,442	13,948	42,563	38,583
Other operating expenses of the Corporate and Other segment	6,507	4,870	19,063	15,597
Total	54,260	43,579	156,189	124,732
Other expenses	$ 119	$ (43)	$ 351	$ 36

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities	$ 1,095,523	$ 1,017,478
Impaired bank loan participations held for investment	2,400	4,800
Unpaid principal on bank loan participations for which external sources were unavailable to determine fair value	807,000	2,300
Carrying value of bank loan participations for which external sources were unavailable to determine fair value	0	$ 2,000
Market approach | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities	$ 5,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	$ 1,095,523	$ 1,017,478
Trading securities:
Fixed maturity securities	3,812	5,063
Short-term investments	42,331	50,844
Fixed maturity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	1,016,818	941,077
State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	134,978	105,841
Residential mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	139,057	150,798
Corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	421,406	378,448
Commercial mortgage and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	177,447	168,047
Obligations of U.S. government corporations and agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	62,375	65,014
U.S. Treasury securities and obligations guaranteed by the U.S. government
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	79,480	71,120
Redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	2,075	1,809
Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	78,705	76,401
Recurring basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	1,095,523	1,017,478
Trading securities:
Fixed maturity securities	3,812	5,063
Short-term investments	42,331	50,844
Recurring basis | Fixed maturity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	1,016,818	941,077
Recurring basis | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	134,978	105,841
Recurring basis | Residential mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	139,057	150,798
Recurring basis | Corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	421,406	378,448
Recurring basis | Commercial mortgage and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	177,447	168,047
Recurring basis | Obligations of U.S. government corporations and agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	62,375	65,014
Recurring basis | U.S. Treasury securities and obligations guaranteed by the U.S. government
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	79,480	71,120
Recurring basis | Redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	2,075	1,809
Recurring basis | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	78,705	76,401
Recurring basis | Preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	66,833	64,827
Recurring basis | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	11,872	11,574
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	90,002	81,305
Trading securities:
Fixed maturity securities	0	1,250
Short-term investments	1,000	1,100
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Fixed maturity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	78,864	70,465
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Residential mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Commercial mortgage and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Obligations of U.S. government corporations and agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	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
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	78,864	70,465
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	11,138	10,840
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	11,138	10,840
Recurring basis | Significant Other Observable Inputs Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	1,000,521	931,173
Trading securities:
Fixed maturity securities	3,812	3,813
Short-term investments	41,331	49,744
Recurring basis | Significant Other Observable Inputs Level 2 | Fixed maturity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	932,954	865,612
Recurring basis | Significant Other Observable Inputs Level 2 | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	134,978	105,841
Recurring basis | Significant Other Observable Inputs Level 2 | Residential mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	139,057	150,798
Recurring basis | Significant Other Observable Inputs Level 2 | Corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	421,406	378,448
Recurring basis | Significant Other Observable Inputs Level 2 | Commercial mortgage and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	172,447	163,047
Recurring basis | Significant Other Observable Inputs Level 2 | Obligations of U.S. government corporations and agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	62,375	65,014
Recurring basis | Significant Other Observable Inputs Level 2 | U.S. Treasury securities and obligations guaranteed by the U.S. government
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	616	655
Recurring basis | Significant Other Observable Inputs Level 2 | Redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	2,075	1,809
Recurring basis | Significant Other Observable Inputs Level 2 | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	67,567	65,561
Recurring basis | Significant Other Observable Inputs Level 2 | Preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	66,833	64,827
Recurring basis | Significant Other Observable Inputs Level 2 | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	734	734
Recurring basis | Significant Unobservable Inputs Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	5,000	5,000
Trading securities:
Fixed maturity securities	0	0
Short-term investments	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Fixed maturity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	5,000	5,000
Recurring basis | Significant Unobservable Inputs Level 3 | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Residential mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Commercial mortgage and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	5,000	5,000
Recurring basis | Significant Unobservable Inputs Level 3 | Obligations of U.S. government corporations and agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | U.S. Treasury securities and obligations guaranteed by the U.S. government
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	0	0
Recurring basis | Significant Unobservable Inputs Level 3 | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	$ 0	$ 0

Fair Value Measurements - Sum51

Fair Value Measurements - Summary of Assets Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	$ 2,400	$ 4,800
Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	2,445	4,849
Nonrecurring basis | 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
Nonrecurring basis | 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
Nonrecurring basis | Significant Unobservable Inputs Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	$ 2,445	$ 4,849

Fair Value Measurements - Sum52

Fair Value Measurements - Summary of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Available-for-sale:
Fixed maturity securities	$ 1,016,818	$ 941,077
Equity securities	78,705	76,401
Trading:
Bank loan participations held-for-investment, at amortized cost, net of allowance	245,741	203,526
Cash and cash equivalents	106,500	109,784	$ 90,873	$ 106,406
Short-term investments	42,331	50,844
Liabilities
Senior debt	88,300	88,300
Junior subordinated debt	104,055	104,055
Carrying Value
Available-for-sale:
Fixed maturity securities	1,016,818	941,077
Equity securities	78,705	76,401
Trading:
Fixed maturity securities	3,812	5,063
Bank loan participations held-for-investment, at amortized cost, net of allowance	245,741	203,526
Cash and cash equivalents	106,500	109,784
Short-term investments	42,331	50,844
Other invested assets – notes receivable	10,188	4,500
Liabilities
Senior debt	88,300	88,300
Junior subordinated debt	104,055	104,055
Fair Value
Available-for-sale:
Fixed maturity securities	1,016,818	941,077
Equity securities	78,705	76,401
Trading:
Fixed maturity securities	3,812	5,063
Bank loan participations held-for-investment, at amortized cost, net of allowance	242,164	203,123
Cash and cash equivalents	106,500	109,784
Short-term investments	42,331	50,844
Other invested assets – notes receivable	12,033	6,008
Liabilities
Senior debt	85,706	85,404
Junior subordinated debt	$ 109,384	$ 99,397

Capital Stock and Equity Awar53

Capital Stock and Equity Awards - Commons Shares (Details) - shares	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares outstanding	29,582,656	29,257,566
Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares issued during period	325,090
Common stock, shares outstanding	29,582,656	29,257,566	29,116,496	28,941,547
Options | Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares issued during period	300,168
RSUs | Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares issued during period	24,922

Capital Stock and Equity Awar54

Capital Stock and Equity Awards - Schedule of Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	Sep. 29, 2017	Aug. 01, 2017	Jun. 30, 2017	May 02, 2017	Mar. 31, 2017	Feb. 14, 2017	Sep. 30, 2016	Aug. 03, 2016	Jun. 30, 2016	May 03, 2016	Mar. 28, 2016	Feb. 16, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Dividend declared per share (in dollars per share)		$ 0.30		$ 0.30		$ 0.30		$ 0.20		$ 0.20		$ 0.20	$ 0.30	$ 0.20	$ 0.90	$ 0.60
Total Amount	$ 8.9		$ 8.9		$ 8.9		$ 5.9		$ 5.9		$ 5.8				$ 26.7	$ 17.6

Capital Stock and Equity Awar55

Capital Stock and Equity Awards - Equity Incentive Plans (Details) - $ / shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	May 31, 2017
Non-qualified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)	$ 42.24	$ 32.07
2014 LTIP | Non-qualified stock options
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	1,880,013
Vesting period (in years)	3 years
2014 LTIP | RSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	1 year
2014 LTIP | RSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	5 years
2014 Director Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares available for issuance	50,000
Number of shares available for grant	32,994
2014 Director Plan | RSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	1 year
2014 Director Plan | RSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	5 years
Common stock | Amendment to the 2014 LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares available for issuance			1,000,000
Number of shares available for grant			500,000

Capital Stock and Equity Awar56

Capital Stock and Equity Awards - Summary of Option Activity (Details) - Options - $ / shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Shares
Beginning of period (in shares)	2,234,699	2,058,085
Granted (in shares)	205,244	706,203
Exercised (in shares)	(735,587)	(256,916)
Forfeited (in shares)	(62,489)	(33,039)
End of period (in shares)	1,641,867	2,474,333
Exercisable, end of period (in shares)	699,922	992,643
Weighted- Average Exercise Price
Beginning of period (in dollars per share)	$ 22.84	$ 18.11
Granted (in dollars per share)	42.24	32.07
Exercised (in dollars per share)	18	15.92
Forfeited (in dollars per share)	30.80	27.68
End of period (in dollars per share)	27.13	22.19
Exercisable, end of period (in dollars per share)	$ 22.63	$ 17.04

Capital Stock and Equity Awar57

Capital Stock and Equity Awards - Summary of RSU Activity (Details) - RSUs - $ / shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Shares
Unvested, beginning of period (in shares)	196,800	234,922
Granted (in shares)	119,312	60,291
Vested (in shares)	(39,113)	0
Forfeited (in shares)	(22,188)	0
Unvested, end of period (in shares)	254,811	295,213
Shares
Unvested, beginning of period (in dollars per share)	$ 24.38	$ 21
Granted (in dollars per share)	42.19	32.03
Vested (in dollars per share)	32.01	0
Forfeited (in dollars per share)	26.06	0
Unvested, end of period (in dollars per share)	$ 31.40	$ 23.25

Capital Stock and Equity Awar58

Capital Stock and Equity Awards - Summary of Share Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Share based compensation expense	$ 1,760	$ 1,520	$ 5,338	$ 4,207
U.S. tax benefit on share based compensation expense	$ 467	$ 425	$ 1,413	$ 1,182

Capital Stock and Equity Awar59

Capital Stock and Equity Awards - Compensation Expense (Details) $ in Millions	3 Months Ended
	Sep. 30, 2017USD ($)
Equity [Abstract]
Unrecognized share based compensation expense	$ 8.5
Weighted-average period of unrecognized share based compensation expense (in years)	1 year 10 months 24 days
Weighted-average remaining contractual life of options outstanding (in years)	4 years 8 months 12 days
Weighted-average remaining contractual life of options exercisable (in years)	4 years

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent event - $ / shares	Dec. 28, 2017	Dec. 15, 2017	Nov. 01, 2017
Subsequent Event [Line Items]
Dividends payable, date declared			Nov. 1, 2017
Cash dividend declared (in dollars per share)			$ 0.30
Special cash dividend declared (in dollars per share)			$ 0.50
Dividends payable, date to be paid	Dec. 28, 2017
Dividend payable, record date		Dec. 15, 2017