ProAssurance (PRA) 10-Q 7 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 31, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	PROASSURANCE CORP
Entity Central Index Key	1,127,703
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		53,413,399

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Investments
Fixed maturities, available for sale, at fair value; amortized cost, $2,505,953 and $2,586,821, respectively	$ 2,546,107	$ 2,613,406
Equity securities, trading, at fair value; cost, $377,336 and $353,744, respectively	410,906	387,274
Short-term investments	263,701	442,084
Business owned life insurance	61,031	60,134
Investment in unconsolidated subsidiaries	330,329	340,906
Other investments, $30,814 and $31,501 at fair value, respectively, otherwise at cost or amortized cost	80,466	81,892
Total Investments	3,692,540	3,925,696
Cash and cash equivalents	117,463	117,347
Premiums receivable	235,117	223,480
Receivable from reinsurers on paid losses and loss adjustment expenses	5,967	5,446
Receivable from reinsurers on unpaid losses and loss adjustment expenses	280,332	273,475
Prepaid reinsurance premiums	47,711	39,723
Deferred policy acquisition costs	50,209	46,809
Deferred tax asset, net	5,919	10,256
Real estate, net	32,611	31,814
Intangible assets	81,592	84,406
Goodwill	210,725	210,725
Other assets	101,530	96,004
Total Assets	4,861,716	5,065,181
Policy liabilities and accruals
Reserve for losses and loss adjustment expenses	1,991,865	1,993,428
Unearned premiums	397,495	372,563
Reinsurance premiums payable	38,076	30,001
Total Policy Liabilities	2,427,436	2,395,992
Other liabilities	169,810	422,285
Debt less debt issuance costs	426,374	448,202
Total Liabilities	3,023,620	3,266,479
Shareholders’ Equity
Common shares, par value $0.01 per share, 100,000,000 shares authorized, 62,822,081 and 62,660,234 shares issued, respectively	628	627
Additional paid-in capital	379,587	376,518
Accumulated other comprehensive income (loss), net of deferred tax expense (benefit) of $14,358 and $9,894, respectively	26,064	17,399
Retained earnings	1,851,745	1,824,088
Treasury shares, at cost, 9,408,925 shares and 9,408,977 shares, respectively	(419,928)	(419,930)
Total Shareholders’ Equity	1,838,096	1,798,702
Total Liabilities and Shareholders’ Equity	$ 4,861,716	$ 5,065,181

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, at fair value; amortized cost	$ 2,505,953	$ 2,586,821
Equity securities, trading, cost	377,336	353,744
Other investments, portion carried at fair value	$ 30,814	$ 31,501
Common shares, par value (USD per share)	$ 0.01	$ 0.01
Common shares, shares authorized (in shares)	100,000,000	100,000,000
Common shares, shares issued (in shares)	62,822,081	62,660,234
Deferred tax expense (benefit) on accumulated other comprehensive income (loss)	$ 14,358	$ 9,894
Treasury shares, number of shares (in shares)	9,408,925	9,408,977

Condensed Consolidated Statemen

Condensed Consolidated Statements of Changes in Capital (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Increase (Decrease) in Stockholders' Equity:
Beginning Balance			$ 1,798,702	$ 1,958,354
Common shares reacquired			0	(2,106)
Common shares issued for compensation and effect of shares reissued to stock purchase plan			1,878	2,195
Share-based compensation			6,092	5,813
Net effect of restricted and performance shares issued and stock options exercised			(5,323)	(2,981)
Dividends to shareholders			(33,040)	(32,913)
Other comprehensive income (loss)			8,665	37,434
Net income	$ 19,518	$ 43,081	60,973	62,399
Ending Balance	1,838,096	2,028,195	1,838,096	2,028,195
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity:
Beginning Balance			627	625
Common shares issued for compensation and effect of shares reissued to stock purchase plan				1
Net effect of restricted and performance shares issued and stock options exercised			1	1
Ending Balance	628	627	628	627
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity:
Beginning Balance			376,518	365,399
Common shares issued for compensation and effect of shares reissued to stock purchase plan			1,876	2,194
Share-based compensation			6,092	5,813
Net effect of restricted and performance shares issued and stock options exercised			(5,324)	(2,982)
Ending Balance	379,587	370,424	379,587	370,424
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity:
Beginning Balance			17,399	23,855
Other comprehensive income (loss)			8,665	37,434
Ending Balance	26,064	61,289	26,064	61,289
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity:
Beginning Balance			1,824,088	1,988,035
Dividends to shareholders			(33,040)	(32,913)
Net income			60,973	62,399
Ending Balance	1,851,745	2,017,521	1,851,745	2,017,521
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity:
Beginning Balance			419,930	(419,560)
Common shares reacquired			0	(2,106)
Common shares issued for compensation and effect of shares reissued to stock purchase plan			2	0
Ending Balance	$ (419,928)	$ (421,666)	$ (419,928)	$ (421,666)

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Income and Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues
Net premiums earned	$ 180,353	$ 176,732	$ 363,256	$ 354,312
Net investment income	22,677	24,583	45,863	50,023
Equity in earnings (loss) of unconsolidated subsidiaries	2,516	376	4,324	(3,259)
Net realized investment gains (losses):
OTTI losses	0	0	(419)	(10,734)
Portion of OTTI losses recognized in other comprehensive income before taxes	0	0	248	1,068
Net impairment losses recognized in earnings	0	0	(171)	(9,666)
Other net realized investment gains (losses)	(2,219)	10,929	11,232	12,244
Total net realized investment gains (losses)	(2,219)	10,929	11,061	2,578
Other income	2,250	2,181	4,071	4,535
Total revenues	205,577	214,801	428,575	408,189
Expenses
Net losses and loss adjustment expenses	115,550	106,899	234,701	217,854
Underwriting, policy acquisition and operating expenses
Operating expense	34,972	32,456	69,454	67,802
DPAC amortization	22,913	21,578	45,540	43,121
Segregated portfolio cells dividend expense (income)	8,811	1,523	11,186	2,699
Interest expense	4,145	3,851	8,278	7,537
Total expenses	186,391	166,307	369,159	339,013
Income before income taxes	19,186	48,494	59,416	69,176
Provision for income taxes
Current expense (benefit)	6,700	3,321	(1,579)	2,670
Deferred expense (benefit)	(7,032)	2,092	22	4,107
Total income tax expense (benefit)	(332)	5,413	(1,557)	6,777
Net income	19,518	43,081	60,973	62,399
Other comprehensive income (loss), after tax, net of reclassification adjustments	5,741	14,174	8,665	37,434
Comprehensive income	$ 25,259	$ 57,255	$ 69,638	$ 99,833
Earnings per share:
Basic (USD per share)	$ 0.37	$ 0.81	$ 1.14	$ 1.17
Diluted (USD per share)	$ 0.36	$ 0.81	$ 1.14	$ 1.17
Weighted average number of common shares outstanding:
Basic (in shares)	53,402	53,205	53,359	53,182
Diluted (in shares)	53,607	53,428	53,571	53,395
Cash dividends declared per common share (USD per share)	$ 0.310	$ 0.31	$ 0.62	$ 0.62

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Statement of Cash Flows [Abstract]
Dividend declared	$ 33,000	$ 32,900
Operating Activities
Net income	60,973	62,399
Adjustments to reconcile income to net cash provided by operating activities:
Depreciation and amortization, net of accretion	13,949	16,971
(Increase) decrease in cash surrender value of BOLI	(897)	(899)
Net realized investment (gains) losses	(11,061)	(2,578)
Share-based compensation	6,092	5,813
Deferred income taxes	22	4,107
Policy acquisition costs, net amortization (net deferral)	(3,400)	(3,325)
Equity in (earnings) loss of unconsolidated subsidiaries	(4,324)	3,259
Other	(438)	(1,247)
Other changes in assets and liabilities:
Premiums receivable	(11,637)	(10,991)
Reinsurance related assets and liabilities	(7,291)	(10,786)
Other assets	(2,613)	16,019
Reserve for losses and loss adjustment expenses	(1,563)	(12,525)
Unearned premiums	24,932	23,148
Other liabilities	(8,730)	(3,134)
Net cash provided (used) by operating activities	54,014	86,231
Purchases of:
Fixed maturities, available for sale	(359,080)	(373,180)
Equity securities, trading	(101,854)	(59,336)
Other investments	(8,879)	(11,382)
Funding of qualified affordable housing tax credit limited partnerships	(320)	(956)
Investment in unconsolidated subsidiaries	(19,787)	(28,096)
Proceeds from sales or maturities of:
Fixed maturities, available for sale	434,075	387,496
Equity securities, trading	85,907	42,227
Other investments	12,689	7,216
Distributions from unconsolidated subsidiaries	34,024	5,180
Net sales or maturities (purchases) of short-term investments	172,250	(87,517)
Unsettled security transactions, net change	12,714	25,720
Purchases of capital assets	(6,593)	(5,219)
Other	(75)	1,573
Net cash provided (used) by investing activities	255,071	(96,274)
Financing Activities
Repayments under revolving credit agreement	(22,000)	0
Repurchase of common stock	0	(2,106)
Dividends to shareholders	(282,180)	(85,893)
External capital contribution received for segregated portfolio cells	162	4,740
Other	(4,951)	(2,629)
Net cash provided (used) by financing activities	(308,969)	(85,888)
Increase (decrease) in Cash and cash equivalents	116	(95,931)
Cash and cash equivalents at beginning of period	117,347	241,100
Cash and cash equivalents at end of period	117,463	145,169
Significant non-cash transactions
Dividends declared and not yet paid	$ 16,524	$ 16,461

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements include the accounts of ProAssurance Corporation and its consolidated subsidiaries (ProAssurance, PRA or the Company). The financial statements have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation, consisting of normal recurring adjustments, have been included. ProAssurance’s results for the six months ended June 30, 2017 are not necessarily indicative of the results that may be expected for the year ending December 31, 2017 . The accompanying Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes contained in ProAssurance’s December 31, 2016 report on Form 10-K. In connection with its preparation of the Condensed Consolidated Financial Statements, ProAssurance evaluated events that occurred subsequent to June 30, 2017 for recognition or disclosure in its financial statements and notes to financial statements. ProAssurance operates in four reportable segments as follows: Specialty P&C , Workers' Compensation, Lloyd's Syndicate and Corporate. For more information on the nature of products and services provided and for financial information by segment, refer to Note 11 of the Notes to Condensed Consolidated Financial Statements. Reclassifications In the second quarter of 2017, ProAssurance began presenting separately the components of Underwriting, policy acquisition and operating expense as Operating expense and DPAC amortization on the Condensed Consolidated Statements of Income and Comprehensive Income in order to provide additional details for investors. The Condensed Consolidated Statements of Income and Comprehensive Income for the three and six months ended June 30, 2016 have been reclassified to conform to the current period presentation. Total Underwriting, policy acquisition and operating expense as well as Net income for all periods presented was not affected by the change in presentation. Other Liabilities Other liabilities consisted of the following: (In thousands) June 30, 2017 December 31, 2016 SPC dividends payable $ 40,625 $ 34,289 Unpaid dividends 16,524 265,659 All other 112,661 122,337 Total other liabilities $ 169,810 $ 422,285 SPC dividends payable are the cumulative undistributed earnings contractually payable to the external preferred shareholders of SPC s operated by ProAssurance's Cayman Islands subsidiary, Eastern Re . Unpaid dividends represent common stock dividends declared by ProAssurance's Board of Directors that had not yet been paid. Unpaid dividends at December 31, 2016 reflect a special dividend declared in late 2016 that was paid in January 2017 . Accounting Changes Adopted Improvements to Employee Share-Based Payment Accounting Effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, the FASB issued guidance that simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of cash flows, and the classification of awards as either equity or liabilities. Under the new guidance, the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes is to be recognized as income tax expense in the current period and included with other income tax cash flows as an operating activity. The threshold for equity classification has also been revised to permit withholdings up to the maximum statutory tax rates in the applicable jurisdictions. The update also provides an accounting policy election to account for forfeitures as they occur. ProAssurance adopted the guidance as of January 1, 2017. The primary effects of the adoption on the current period are the following: (1) using a prospective application, ProAssurance recorded unrecognized excess tax benefits of $0.3 million and $2.6 million for the three and six months ended June 30, 2017 , respectively, as a current tax expense, (2) using a modified retrospective application, ProAssurance elected to recognize forfeitures as they occur and recorded a $0.4 million increase to Additional paid-in capital and a respective $0.3 million reduction to Retained earnings and a $0.1 million increase to deferred taxes to reflect the incremental share-based compensation expense, net of related tax impacts, that would have been recognized in prior years under the modified guidance and (3) excess tax benefits from share-based compensation of $2.3 million was reclassified from financing activities to operating activities in the Condensed Consolidated Statements of Cash Flows. Interests Held Through Related Parties that are Under Common Control Effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, the FASB issued additional guidance regarding consolidation of legal entities such as LP s/ LLC s and securitization structures (collateralized debt obligations, collateralized loan obligations, and mortgage-backed security transactions). The new guidance modifies the criteria used by a reporting entity when determining if it is a primary beneficiary of a VIE when there are entities under common control and the reporting entity has indirect interests in the VIE through related party relationships. ProAssurance adopted the guidance as of January 1, 2017. Adoption of the guidance had no material effect on ProAssurance’s results of operations or financial position. Simplifying the Transition to the Equity Method of Accounting Effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, the FASB issued guidance that eliminates the requirement for retroactive restatement when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence. The new guidance provides that the cost of acquiring an additional interest in an investee is to be added to the current basis of an investor’s previously held interest and the equity method of accounting adopted as of the date the investment becomes qualified for equity method accounting with no retroactive adjustment of the investment. If an available-for-sale equity security qualifies for the equity method of accounting, the unrealized holding gain or loss in AOCI is to be recognized through earnings at the date the investment becomes qualified for use of the equity method. ProAssurance adopted the guidance as of January 1, 2017. Adoption of the guidance had no material effect on ProAssurance’s results of operations or financial position. Accounting Changes Not Yet Adopted Clarifying the Definition of a Business Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance which provides clarification of the definition of a business, affecting areas such as acquisitions, disposals, goodwill and consolidation. The new guidance intends to assist entities with determining whether a transaction should be accounted for as an acquisition or disposal of assets or a business. ProAssurance plans to early adopt the guidance during 2017 for any acquisitions or dispositions. Adoption is not expected to have a material effect on ProAssurance’s results of operations or financial position. Restricted Cash Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance related to the classification of restricted cash presented in the statement of cash flows with the objective of reducing diversity in practice. Under the new guidance, entities are required to include restricted cash and restricted cash equivalents with cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts as presented on the statement of cash flows. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption is not expected to have a material effect on ProAssurance’s results of operations, financial position or cash flows. Intra-Entity Transfers of Assets Other than Inventory Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance which reduces the complexity in accounting standards related to the income tax consequences of intra-entity transfers of assets other than inventory. Under the new guidance, entities are required to recognize income tax consequences of an intra-entity transfer of assets other than inventory when the transfer occurs instead of delaying recognition until the asset has been sold to an outside party. ProAssurance is in the process of evaluating the effect the new guidance would have on its results of operations and financial position and plans to adopt the guidance beginning January 1, 2018. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Classification of Certain Cash Receipts and Cash Payments Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance related to the classification of certain cash receipts and cash payments presented in the statement of cash flows with the objective of reducing diversity in practice. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption is not expected to have a material effect on ProAssurance’s results of operations, financial position or cash flows. Revenue from Contracts with Customers Effective for fiscal years beginning after December 15, 2017 the FASB issued guidance related to revenue from contracts with customers. The core principle of the new guidance is that revenue is recognized to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ProAssurance plans to adopt the guidance beginning January 1, 2018. As the majority of ProAssurance's revenues come from insurance contracts which fall under the scope of other FASB standards, adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Recognition and Measurement of Financial Assets and Financial Liabilities Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance that requires 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. The new guidance also specifies that an entity use the exit price notion when measuring the fair value of financial instruments for disclosure purposes and present financial assets and liabilities by measurement category and form of financial asset. Other provisions of the new guidance include: revised disclosure requirements related to the presentation in comprehensive income of changes in the fair value of liabilities; elimination, for public companies, of disclosure requirements relative to the method(s) and significant assumptions underlying fair values disclosed for financial instruments measured at amortized cost; and simplified impairment assessments for equity investments without readily determinable fair values. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Modification Accounting for Employee Share-Based Payment Awards Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance which reduces the complexity in accounting standards when there is a change in the terms or conditions of a share-based payment award. The new guidance clarifies that an entity should apply the modification accounting guidance if the value, vesting conditions or classification of the award changes. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Premium Amortization on Purchased Callable Debt Securities Effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years, the FASB issued guidance that will require the premium for certain callable debt securities to be amortized over a shorter period than is currently required. Currently amortization is permitted over the contractual life of the instrument and the guidance shortens the amortization to the earliest call date. The purpose of the guidance is to more closely align the amortization period of premiums to expectations incorporated in market pricing on the underlying securities. ProAssurance plans to adopt the guidance beginning January 1, 2019. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Leases Effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years, the FASB issued guidance that requires a lessee to recognize for all leases (with the exception of short-term leases) a lease liability, which is a lessee's obligation to make lease payments arising from a lease, measured on a discounted basis, and a right-of-use asset, which is an asset that represents the lessee's right to use, or control the use of, a specified asset for the lease term. ProAssurance plans to adopt the guidance beginning January 1, 2019. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position as ProAssurance does not have any leases it believes to be material. Simplifying the Test for Goodwill Impairment Effective for the fiscal years beginning after December 15, 2019 and interim periods within those fiscal years, the FASB issued guidance that simplifies the requirements to test goodwill for impairment for business entities that have goodwill reported in their financial statements. The guidance eliminates the second step of the impairment test which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount. In addition, the guidance also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment. ProAssurance plans to adopt the guidance beginning January 1, 2020. Adoption is not expected to have a material effect on ProAssurance’s results of operations or financial position. Improvements to Financial Instruments - Credit Losses Effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years, the FASB issued guidance that replaces the incurred loss impairment methodology, which delays recognition of credit losses until a probable loss has been incurred, with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. Under the new guidance, credit losses are required to be recorded through an allowance for credit losses account and the income statement reflects the measurement for newly recognized financial assets, as well as increases or decreases of expected credit losses that have taken place during the period. ProAssurance is in the process of evaluating the effect the new guidance would have on its results of operations and financial position and plans to adopt the guidance beginning January 1, 2020. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position.

Fair Value Measurement

Fair Value Measurement	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. A three level hierarchy has been established for valuing assets and liabilities based on how transparent (observable) the inputs are that are used to determine fair value, with the inputs considered most observable categorized as Level 1 and those that are the least observable categorized as Level 3. Hierarchy levels are defined as follows: Level 1: quoted (unadjusted) market prices in active markets for identical assets and liabilities. For ProAssurance, Level 1 inputs are generally quotes for debt or equity securities actively traded in exchange or over-the-counter markets. Level 2: market data obtained from sources independent of the reporting entity (observable inputs). For ProAssurance, Level 2 inputs generally include quoted prices in markets that are not active, quoted prices for similar assets or liabilities, and results from pricing models that use observable inputs such as interest rates and yield curves that are generally available at commonly quoted intervals. Level 3: the reporting entity's own assumptions about market participant assumptions based on the best information available in the circumstances (non-observable inputs). For ProAssurance, Level 3 inputs are used in situations where little or no Level 1 or 2 inputs are available or are inappropriate given the particular circumstances. Level 3 inputs include results from pricing models for which some or all of the inputs are not observable, discounted cash flow methodologies, single non-binding broker quotes and adjustments to externally quoted prices that are based on management judgment or estimation. Fair values of assets measured at fair value on a recurring basis as of June 30, 2017 and December 31, 2016 are shown in the following tables. Where applicable, the tables also indicate the fair value hierarchy of the valuation techniques utilized to determine those fair values. For some assets, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. When this is the case, the asset is categorized based on the level of the most significant input to the fair value measurement. Assessments of the significance of a particular input to the fair value measurement require judgment and consideration of factors specific to the assets being valued. June 30, 2017 Fair Value Measurements Using Total (In thousands) Level 1 Level 2 Level 3 Fair Value Assets: Fixed maturities, available for sale U.S. Treasury obligations $ — $ 143,453 $ — $ 143,453 U.S. Government-sponsored enterprise obligations — 20,192 — 20,192 State and municipal bonds — 721,836 — 721,836 Corporate debt, multiple observable inputs 2,406 1,292,473 — 1,294,879 Corporate debt, limited observable inputs — — 17,849 17,849 Residential mortgage-backed securities — 206,415 — 206,415 Agency commercial mortgage-backed securities — 11,960 — 11,960 Other commercial mortgage-backed securities — 17,157 — 17,157 Other asset-backed securities — 109,361 3,005 112,366 Equity securities Financial 82,324 — — 82,324 Utilities/Energy 44,687 — — 44,687 Consumer oriented 56,079 — — 56,079 Industrial 49,635 — — 49,635 Bond funds 116,025 — — 116,025 All other 62,156 — — 62,156 Short-term investments 251,486 12,215 — 263,701 Other investments 963 29,846 5 30,814 Total assets categorized within the fair value hierarchy $ 665,761 $ 2,564,908 $ 20,859 3,251,528 LP/LLC interests carried at NAV which approximates fair value. These interests, reported as a part of Investment in unconsolidated subsidiaries, are not categorized within the fair value hierarchy. 201,154 Total assets at fair value $ 3,452,682 December 31, 2016 Fair Value Measurements Using Total (In thousands) Level 1 Level 2 Level 3 Fair Value Assets: Fixed maturities, available for sale U.S. Treasury obligations $ — $ 146,539 $ — $ 146,539 U.S. Government-sponsored enterprise obligations — 30,235 — 30,235 State and municipal bonds — 800,463 — 800,463 Corporate debt, multiple observable inputs 2,339 1,261,842 — 1,264,181 Corporate debt, limited observable inputs — — 14,810 14,810 Residential mortgage-backed securities — 217,906 — 217,906 Agency commercial mortgage-backed securities — 12,783 — 12,783 Other commercial mortgage-backed securities — 19,611 — 19,611 Other asset-backed securities — 103,871 3,007 106,878 Equity securities Financial 81,749 — — 81,749 Utilities/Energy 52,869 — — 52,869 Consumer oriented 61,284 — — 61,284 Industrial 54,265 — — 54,265 Bond funds 79,843 10,159 — 90,002 All other 27,181 19,924 — 47,105 Short-term investments 437,580 4,504 — 442,084 Other investments 1,956 29,542 3 31,501 Total assets categorized within the fair value hierarchy $ 799,066 $ 2,657,379 $ 17,820 3,474,265 LP/LLC interests carried at NAV which approximates fair value. These interests, reported as a part of Investment in unconsolidated subsidiaries, are not categorized within the fair value hierarchy. 204,719 Total assets at fair value $ 3,678,984 The fair values for securities included in the Level 2 category, with the few exceptions described below, were developed by one of several third party, nationally recognized pricing services, including services that price only certain types of securities. Each service uses complex methodologies to determine values for securities and subject the values they develop to quality control reviews. Management selected a primary source for each type of security in the portfolio and reviewed the values provided for reasonableness by comparing data to alternate pricing services and to available market and trade data. Values that appeared inconsistent were further reviewed for appropriateness. Any value that did not appear reasonable was discussed with the service that provided the value and adjusted, if necessary. There were no material changes to the values supplied by the pricing services during the three and six months ended June 30, 2017 and 2016 . Level 2 Valuations Below is a summary description of the valuation methodologies primarily used by the pricing services for securities in the Level 2 category, by security type: U.S. Treasury obligations were valued based on quoted prices for identical assets, or, in markets that are not active, quotes for similar assets, taking into consideration adjustments for variations in contractual cash flows and yields to maturity. U.S. Government-sponsored enterprise obligations were valued using pricing models that consider current and historical market data, normal trading conventions, credit ratings, and the particular structure and characteristics of the security being valued, such as yield to maturity, redemption options, and contractual cash flows. Adjustments to model inputs or model results were included in the valuation process when necessary to reflect recent regulatory, government or corporate actions or significant economic, industry or geographic events affecting the security’s fair value. State and municipal bonds were valued using a series of matrices that considered credit ratings, the structure of the security, the sector in which the security falls, yields, and contractual cash flows. Valuations were further adjusted, when necessary, to reflect the expected effect on fair value of recent significant economic or geographic events or ratings changes. Corporate debt, multiple observable inputs consisted primarily of corporate bonds, but also included a small number of bank loans. The methodology used to value Level 2 corporate bonds was the same as the methodology previously described for U.S. Government-sponsored enterprise obligations. Bank loans were valued based on an average of broker quotes for the loans in question, if available. If quotes were not available, the loans were valued based on quoted prices for comparable loans or, if the loan was newly issued, by comparison to similar seasoned issues. Broker quotes were compared to actual trade prices to permit assessment of the reliability of the quotes; unreliable quotes were not considered in quoted averages. Residential and commercial mortgage-backed securities were valued using a pricing matrix which considers the issuer type, coupon rate and longest cash flows outstanding. The matrix used was based on the most recently available market information. Agency and non-agency collateralized mortgage obligations were both valued using models that consider the structure of the security, current and historical information regarding prepayment speeds, ratings and ratings updates, and current and historical interest rate and interest rate spread data. Other asset-backed securities were valued using models that consider the structure of the security, monthly payment information, current and historical information regarding prepayment speeds, ratings and ratings updates, and current and historical interest rate and interest rate spread data. Spreads and prepayment speeds consider collateral type. Equity securities were securities not traded on an exchange on the valuation date. The securities were valued using the most recently available quotes for the securities. Short-term investments are securities maturing within one year, carried at cost which approximated the fair value of the security due to the short term to maturity. Other investments consisted primarily of convertible bonds valued using a pricing model that incorporated selected dealer quotes as well as current market data regarding equity prices and risk free rates. If dealer quotes were unavailable for the security being valued, quotes for securities with similar terms and credit status were used in the pricing model. Dealer quotes selected for use were those considered most accurate based on parameters such as underwriter status and historical reliability. Level 3 Valuations Below is a summary description of the valuation processes and methodologies used as well as quantitative information regarding securities in the Level 3 category. Level 3 Valuation Processes • Level 3 securities are priced by the Chief Investment Officer. • Level 3 valuations are computed quarterly. Prices are evaluated quarterly against prior period prices and the expected change in prices. • ProAssurance's Level 3 securities are primarily NRSRO rated debt instruments for which comparable market inputs are commonly available for evaluating the securities in question. Valuation of these debt instruments is not overly sensitive to changes in the unobservable inputs used. Level 3 Valuation Methodologies Corporate debt, limited observable inputs consisted of corporate bonds valued using dealer quotes for similar securities or discounted cash flow models using yields currently available for similar securities. Similar securities are defined as securities of comparable credit quality that have like terms and payment features. Assessments of credit quality were based on NRSRO ratings, if available, or were subjectively determined by management if not available. At June 30, 2017 , 77% of the securities were rated and the average rating was BBB+ . At December 31, 2016 , 84% of the securities were rated and the average rating was BBB+ . Other asset-backed securities consisted of securitizations of receivables valued using dealer quotes for similar securities or discounted cash flow models using yields currently available for similar securities. Other investments consisted of convertible securities for which limited observable inputs were available at June 30, 2017 and at December 31, 2016 . The securities were valued internally based on expected cash flows, including the expected final recovery, discounted at a yield that considered the lack of liquidity and the financial status of the issuer. Quantitative Information Regarding Level 3 Valuations Fair Value at (In thousands) June 30, 2017 December 31, 2016 Valuation Technique Unobservable Input Range Assets: Corporate debt, limited observable inputs $17,849 $14,810 Market Comparable Comparability Adjustment 0% - 5% (2.5%) Discounted Cash Flows Comparability Adjustment 0% - 5% (2.5%) Other asset-backed securities $3,005 $3,007 Market Comparable Comparability Adjustment 0% - 5% (2.5%) Discounted Cash Flows Comparability Adjustment 0% - 5% (2.5%) Other investments $5 $3 Discounted Cash Flows Comparability Adjustment 0% - 10% (5%) The significant unobservable inputs used in the fair value measurement of the above listed securities were the valuations of comparable securities with similar issuers, credit quality and maturity. Changes in the availability of comparable securities could result in changes in the fair value measurements. Fair Value Measurements - Level 3 Assets The following tables (the Level 3 Tables) present summary information regarding changes in the fair value of assets measured at fair value using Level 3 inputs. June 30, 2017 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance March 31, 2017 $ 18,914 $ 3,002 $ 903 $ 22,819 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (34 ) — — (34 ) Net realized investment gains (losses) — — (124 ) (124 ) Included in other comprehensive income (70 ) 3 138 71 Purchases 4,841 — — 4,841 Sales (1,848 ) — (912 ) (2,760 ) Transfers in 10 — — 10 Transfers out (3,964 ) — — (3,964 ) Balance June 30, 2017 $ 17,849 $ 3,005 $ 5 $ 20,859 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ — June 30, 2017 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance December 31, 2016 $ 14,810 $ 3,007 $ 3 $ 17,820 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (73 ) — — (73 ) Net realized investment gains (losses) 13 — (124 ) (111 ) Included in other comprehensive income (278 ) (2 ) 140 (140 ) Purchases 11,889 — — 11,889 Sales (3,560 ) — (912 ) (4,472 ) Transfers in 10 — 898 908 Transfers out (4,962 ) — — (4,962 ) Balance June 30, 2017 $ 17,849 $ 3,005 $ 5 $ 20,859 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ — June 30, 2016 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance March 31, 2016 $ 13,649 $ 4,088 $ 1,558 $ 19,295 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (22 ) — (3 ) (25 ) Net realized investment gains (losses) — — — — Included in other comprehensive income 204 7 1 212 Purchases 5,995 — — 5,995 Sales (2,016 ) (535 ) — (2,551 ) Transfers in — — — — Transfers out — (2,805 ) — (2,805 ) Balance June 30, 2016 $ 17,810 $ 755 $ 1,556 $ 20,121 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ — June 30, 2016 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance December 31, 2015 $ 14,500 $ 757 $ — $ 15,257 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (36 ) — (4 ) (40 ) Net realized investment gains (losses) (75 ) — — (75 ) Included in other comprehensive income 129 5 — 134 Purchases 5,995 3,500 1,560 11,055 Sales (2,697 ) (702 ) — (3,399 ) Transfers in — — — — Transfers out (6 ) (2,805 ) — (2,811 ) Balance June 30, 2016 $ 17,810 $ 755 $ 1,556 $ 20,121 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ — Transfers There were no transfers between the Level 1 and Level 2 categories during the three months ended June 30, 2017 . During the six-month period June 30, 2017 , equity securities of approximately $35.4 million were transferred from Level 2 to Level 1. Transfers between the Level 1 and Level 2 categories were nominal during the three and six months ended June 30, 2016 . Transfers shown in the preceding Level 3 tables were as of the end of the quarter in which the transfer occurred. All transfers were to or from Level 2. All transfers during the three and six months ended June 30, 2017 and 2016 related to securities held for which the level of market activity for identical or nearly identical securities varies from period to period. The securities were valued using multiple observable inputs when those inputs were available; otherwise the securities were valued using limited observable inputs. Fair Values Not Categorized Investments in unconsolidated subsidiaries at both June 30, 2017 and December 31, 2016 included interests in investment fund LP s/ LLC s that measure fund assets at fair value on a recurring basis and that provide a NAV for the interest. The carrying value of these interests is based on the NAV provided and was considered to approximate the fair value of the interests. In accordance with GAAP , the fair value of these investments was not classified within the fair value hierarchy. Additional information regarding these investments is as follows: Unfunded Fair Value (In thousands) June 30, June 30, December 31, Investments in LPs/LLCs: Private debt funds (1) $11,247 $ 44,520 $ 55,637 Long equity fund (2) None 7,459 6,268 Long/short equity funds (3) None 30,404 28,926 Non-public equity funds (4) $85,121 91,707 89,691 Multi-strategy fund of funds (5) None 8,783 8,448 Structured credit fund (6) None 6,187 4,273 Long/short commodities fund (7) None 12,094 11,476 $ 201,154 $ 204,719 (1) The investment is comprised of interests in two unrelated LP funds that are structured to provide interest distributions primarily through diversified portfolios of private debt instruments. One LP allows redemption by special consent; the other does not permit redemption. Income and capital are to be periodically distributed at the discretion of the LP s over an anticipated time frame that spans from three to eight years. (2) The fund is a LP that holds long equities of public international companies. Redemptions are allowed at the end of any calendar month with a prior notice requirement of 15 days and are paid within 10 days of the end of the calendar month of the redemption request. (3) The investment is comprised of interests in multiple unrelated LP funds. The funds hold primarily long and short North American equities and target absolute returns using strategies designed to take advantage of market opportunities. The funds generally permit quarterly or semi-annual capital redemptions subject to notice requirements of 30 to 90 days. For some funds, redemptions above specified thresholds (lowest threshold is 90% ) may be only partially payable until after a fund audit is completed and are then payable within 30 days. (4) The investment is comprised of interests in multiple unrelated LP funds, each structured to provide capital appreciation through diversified investments in private equity, which can include investments in buyout, venture capital, debt including senior, second lien and mezzanine, distressed debt, and other private equity-oriented LP s. Two of the LP s allow redemption by terms set forth in the LP agreements; the others do not permit redemption. Income and capital are to be periodically distributed at the discretion of the LP over time frames that are anticipated to span up to nine years. (5) This fund is a LLC structured to build and manage low volatility, multi-manager portfolios that have little or no correlation to the broader fixed income and equity security markets. Redemptions are not permitted but offers to repurchase units of the LLC may be extended periodically. (6) This fund is a LP seeking to obtain superior risk-adjusted absolute returns by acquiring and actively managing a diversified portfolio of debt securities, including bonds, loans and other asset-backed instruments. Redemptions are allowed at any quarter-end with a prior notice requirement of 90 days . (7) This fund is a LLC invested across a broad range of commodities and focuses primarily on market neutral, relative value strategies, seeking to generate absolute returns with low correlation to broad commodity, equity and fixed income markets. Following an initial one-year lock-up period, redemptions are allowed with a prior notice requirement of 30 days and are payable within 30 days. ProAssurance may not sell, transfer or assign its interest in any of the above LP s/ LLC s without special consent from the LP s/ LLC s. Financial Instruments - Methodologies Other Than Fair Value The following table provides the estimated fair value of our financial instruments that, in accordance with GAAP for the type of investment, are measured using a methodology other than fair value. All fair values provided fall within the Level 3 fair value category. June 30, 2017 December 31, 2016 (In thousands) Carrying Fair Carrying Fair Financial assets: BOLI $ 61,031 $ 61,031 $ 60,134 $ 60,134 Other investments $ 49,652 $ 58,704 $ 50,391 $ 58,757 Other assets $ 33,386 $ 33,225 $ 29,111 $ 28,960 Financial liabilities: Senior notes due 2023* $ 250,000 $ 274,610 $ 250,000 $ 270,898 Revolving Credit Agreement* $ 178,000 $ 178,000 $ 200,000 $ 200,000 Other liabilities $ 18,868 $ 18,868 $ 17,033 $ 17,011 * Carrying value excludes debt issuance costs. The fair value of the BOLI was equal to the cash surrender value associated with the policies on the valuation date. Other investments listed in the table above include interests in certain investment fund LP s/ LLC s accounted for using the cost method, investments in FHLB common stock carried at cost, and an annuity investment carried at amortized cost. The estimated fair value of the LP / LLC interests was based on the equity value of the interest provided by the LP / LLC managers for the most recent quarter, which approximates the fair value of the interest. The estimated fair value of the FHLB common stock was based on the amount ProAssurance would receive if its membership were canceled, as the membership cannot be sold. The fair value of the annuity represents the present value of the expected future cash flows discounted using a rate available in active markets for similarly structured instruments. Other assets and Other liabilities primarily consisted of related investment assets and liabilities associated with funded deferred compensation agreements. Fair values of the funded deferred compensation assets and liabilities were based on the NAV s provided by the underlying funds. Other assets also included a secured note receivable and unsecured note receivables under two separate line of credit agreements. Fair value of these receivables was based on the present value of expected cash flows from the receivables, discounted at market rates on the valuation date for receivables with similar credit standings and similar payment structures. The fair value of the debt was estimated based on the present value of expected future cash outflows, discounted at rates available on the valuation date for similar debt issued by entities with a similar credit standing to ProAssurance.

Investments

Investments	6 Months Ended
	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Available-for-sale securities at June 30, 2017 and December 31, 2016 included the following: June 30, 2017 (In thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Fixed maturities U.S. Treasury obligations $ 143,088 $ 1,092 $ 727 $ 143,453 U.S. Government-sponsored enterprise obligations 20,179 140 127 20,192 State and municipal bonds 702,688 21,217 2,069 721,836 Corporate debt 1,294,689 23,274 5,235 1,312,728 Residential mortgage-backed securities 204,179 3,369 1,133 206,415 Agency commercial mortgage-backed securities 11,945 77 62 11,960 Other commercial mortgage-backed securities 17,087 152 82 17,157 Other asset-backed securities 112,098 361 93 112,366 $ 2,505,953 $ 49,682 $ 9,528 $ 2,546,107 December 31, 2016 (In thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Fixed maturities U.S. Treasury obligations $ 146,186 $ 1,264 $ 911 $ 146,539 U.S. Government-sponsored enterprise obligations 30,038 388 191 30,235 State and municipal bonds 790,154 17,261 6,952 800,463 Corporate debt 1,264,812 22,659 8,480 1,278,991 Residential mortgage-backed securities 216,285 3,667 2,046 217,906 Agency commercial mortgage-backed securities 12,837 89 143 12,783 Other commercial mortgage-backed securities 19,571 177 137 19,611 Other asset-backed securities 106,938 207 267 106,878 $ 2,586,821 $ 45,712 $ 19,127 $ 2,613,406 The recorded cost basis and estimated fair value of available-for-sale fixed maturities at June 30, 2017 , by contractual maturity, are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. (In thousands) Amortized Due in one Due after Due after Due after Total Fair Fixed maturities, available for sale U.S. Treasury obligations $ 143,088 $ 29,357 $ 92,270 $ 18,815 $ 3,011 $ 143,453 U.S. Government-sponsored enterprise obligations 20,179 499 7,873 11,678 142 20,192 State and municipal bonds 702,688 54,052 243,955 308,236 115,593 721,836 Corporate debt 1,294,689 138,176 733,558 418,955 22,039 1,312,728 Residential mortgage-backed securities 204,179 206,415 Agency commercial mortgage-backed securities 11,945 11,960 Other commercial mortgage-backed securities 17,087 17,157 Other asset-backed securities 112,098 112,366 $ 2,505,953 $ 2,546,107 Excluding obligations of the U.S. Government or U.S. Government-sponsored enterprises, no investment in any entity or its affiliates exceeded 10% of Shareholders’ equity at June 30, 2017 . Cash and securities with a carrying value of $46.4 million at June 30, 2017 were on deposit with various state insurance departments to meet regulatory requirements. ProAssurance also held securities with a carrying value of $239.8 million at June 30, 2017 that are pledged as collateral security for advances under the Revolving Credit Agreement (see Note 7 of the Notes to Condensed Consolidated Financial Statements for additional detail on the Revolving Credit Agreement ). As a member of Lloyd's and a capital provider to Syndicate 1729 , ProAssurance is required to maintain capital at Lloyd's , referred to as FAL . ProAssurance investments at June 30, 2017 included fixed maturities with a fair value of $94.8 million and short-term investments with a fair value of approximately $3.4 million on deposit with Lloyd's in order to satisfy these FAL requirements. BOLI ProAssurance holds BOLI policies that are carried at the current cash surrender value of the policies (original cost $33 million ). All insured individuals were members of ProAssurance management at the time the policies were acquired. The primary purpose of the program is to offset future employee benefit expenses through earnings on the cash value of the policies. ProAssurance is the owner and beneficiary of these policies. Investment in Unconsolidated Subsidiaries ProAssurance holds investments in unconsolidated subsidiaries, accounted for under the equity method. The investments include the following: Carrying Value (In thousands) June 30, December 31, Investment in LPs/LLCs: Qualified affordable housing tax credit partnerships $ 95,041 $ 102,313 Other tax credit partnerships 8,976 11,459 All other LPs/LLCs 226,312 227,134 $ 330,329 $ 340,906 Qualified affordable housing tax credit partnership interests held by ProAssurance generate investment returns by providing tax benefits to fund investors in the form of tax credits and project operating losses. The carrying value of these investments reflects ProAssurance's total commitments (both funded and unfunded) to the partnerships, less any amortization. ProAssurance's ownership percentage relative to two of the tax credit partnership interests is almost 100% ; these interests had a carrying value of $36.4 million at June 30, 2017 and $40.2 million at December 31, 2016 . ProAssurance's ownership percentage relative to the remaining tax credit partnership interests is less than 20% ; these interests had a carrying value of $58.6 million at June 30, 2017 and $62.1 million at December 31, 2016 . ProAssurance does not have the ability to exert control over the partnerships; all are accounted for using the equity method. Other tax credit partnerships are comprised entirely of historic tax credits. The historic tax credits generate investment returns by providing benefits to fund investors in the form of tax credits, tax-deductible project operating losses and positive cash flows. The carrying value of these investments reflects ProAssurance's total funded commitments less any amortization. ProAssurance's ownership percentage relative to the tax credit partnerships is almost 100% . ProAssurance does not have the ability to exert control over the partnerships; the interests are accounted for using the equity method. As discussed in additional detail in Note 2 of the Notes to Condensed Consolidated Financial Statements, ProAssurance holds interests in certain LP s/ LLC s that are investment funds which measure fund assets at fair value on a recurring basis and the fund managers provide a NAV for the interest. The carrying value of these interests is based on the NAV provided, and is considered to approximate the fair value of the interests; such interests totaled $201.2 million at June 30, 2017 and $204.7 million at December 31, 2016 . ProAssurance also holds interests in other LP s/ LLC s which are not considered to be investment funds; such interests totaled $25.1 million at June 30, 2017 and $22.4 million at December 31, 2016 . ProAssurance's ownership percentage relative to three of the LP s/ LLC s is greater than 25% , which is expected to be reduced as the funds mature and other investors participate in the funds; these investments had a carrying value of $20.9 million at June 30, 2017 and $18.5 million at December 31, 2016 . ProAssurance's ownership percentage relative to the remaining LP s/ LLC s is less than 25% ; these interests had a carrying value of $205.4 million at June 30, 2017 and $208.6 million at December 31, 2016 . ProAssurance does not have the ability to exert control over any of these funds. Other Investments Other investments at June 30, 2017 and December 31, 2016 were comprised as follows: (In thousands) June 30, December 31, Investments in LPs/LLCs, at cost $ 46,200 $ 46,852 Convertible securities, at fair value 30,814 31,501 Other, principally FHLB capital stock, at cost 3,452 3,539 $ 80,466 $ 81,892 Investments in convertible securities are carried at fair value as permitted by the accounting guidance for hybrid financial instruments, with changes in fair value recognized in income as a component of Net realized investment gains (losses) during the period of change. FHLB capital stock is not marketable, but may be liquidated by terminating membership in the FHLB . The liquidation process can take up to five years . Investments Held in a Loss Position The following tables provide summarized information with respect to investments held in an unrealized loss position at June 30, 2017 and December 31, 2016 , including the length of time the investment had been held in a continuous unrealized loss position. June 30, 2017 Total Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Fair Unrealized (In thousands) Value Loss Value Loss Value Loss Fixed maturities, available for sale U.S. Treasury obligations $ 83,416 $ 727 $ 78,080 $ 664 $ 5,336 $ 63 U.S. Government-sponsored enterprise obligations 15,907 127 15,907 127 — — State and municipal bonds 111,522 2,069 103,371 1,441 8,151 628 Corporate debt 372,586 5,235 336,877 3,167 35,709 2,068 Residential mortgage-backed securities 89,610 1,133 87,491 1,086 2,119 47 Agency commercial mortgage-backed securities 4,568 62 4,188 34 380 28 Other commercial mortgage-backed securities 9,147 82 7,457 65 1,690 17 Other asset-backed securities 40,149 93 38,264 91 1,885 2 $ 726,905 $ 9,528 $ 671,635 $ 6,675 $ 55,270 $ 2,853 December 31, 2016 Total Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Fair Unrealized (In thousands) Value Loss Value Loss Value Loss Fixed maturities, available for sale U.S. Treasury obligations $ 79,833 $ 911 $ 79,833 $ 911 $ — $ — U.S. Government-sponsored enterprise obligations 11,746 191 11,746 191 — — State and municipal bonds 224,884 6,952 219,276 6,444 5,608 508 Corporate debt 469,632 8,480 424,721 5,662 44,911 2,818 Residential mortgage-backed securities 103,680 2,046 100,542 1,982 3,138 64 Agency commercial mortgage-backed securities 4,579 143 4,192 114 387 29 Other commercial mortgage-backed securities 9,822 137 9,179 134 643 3 Other asset-backed securities 44,343 267 39,079 256 5,264 11 $ 948,519 $ 19,127 $ 888,568 $ 15,694 $ 59,951 $ 3,433 As of June 30, 2017 , excluding U.S. Government or U.S. Government-sponsored enterprise obligations, there were 534 debt securities ( 21.4% of all available-for-sale fixed maturity securities held) in an unrealized loss position representing 363 issuers. The greatest and second greatest unrealized loss positions among those securities were approximately $0.5 million and $0.3 million , respectively. The securities were evaluated for impairment as of June 30, 2017 . As of December 31, 2016 , excluding U.S. Government or U.S. Government-sponsored enterprise obligations, there were 703 debt securities ( 27.2% of all available-for-sale fixed maturity securities held) in an unrealized loss position representing 456 issuers. The greatest and second greatest unrealized loss positions among those securities were each approximately $0.5 million . The securities were evaluated for impairment as of December 31, 2016 . Each quarter, ProAssurance performs a detailed analysis for the purpose of assessing whether any of the securities it holds in an unrealized loss position have suffered an OTTI in value. A detailed discussion of the factors considered in the assessment is included in Note 1 of the Notes to Consolidated Financial Statements included in ProAssurance's December 31, 2016 Form 10-K. Fixed maturity securities held in an unrealized loss position at June 30, 2017 , excluding asset-backed securities, have paid all scheduled contractual payments and are expected to continue doing so. Expected future cash flows of asset-backed securities held in an unrealized loss position were estimated as part of the June 30, 2017 impairment evaluation using the most recently available six-month historical performance data for the collateral (loans) underlying the security or, if historical data was not available, sector based assumptions, and equaled or exceeded the current amortized cost basis of the security. Net Investment Income Net investment income by investment category was as follows: Three Months Ended Six Months Ended (In thousands) 2017 2016 2017 2016 Fixed maturities $ 18,841 $ 21,208 $ 38,962 $ 43,784 Equities 4,298 3,561 7,942 7,204 Short-term and Other investments 978 678 1,778 1,082 BOLI 442 439 897 899 Investment fees and expenses (1,882 ) (1,303 ) (3,716 ) (2,946 ) Net investment income $ 22,677 $ 24,583 $ 45,863 $ 50,023 Equity in Earnings (Loss) of Unconsolidated Subsidiaries Equity in earnings (loss) of unconsolidated subsidiaries included losses from qualified affordable housing project tax credit investments and historic tax credit investments. The losses recorded reflect ProAssurance's allocable portion of partnership operating losses. Losses from qualified affordable housing project tax credit investments were $4.0 million and $7.3 million for the three and six months ended June 30, 2017 , respectively, and $3.0 million and $8.3 million for the same respective periods of 2016 . Tax credits recognized related to these investments totaled $4.6 million and $9.2 million for the three and six months ended June 30, 2017 , respectively, and $4.6 million and $9.3 million for the same respective periods of 2016 . Losses from historic tax credit investments were $2.4 million and $2.8 million for the three and six months ended June 30, 2017 , respectively, and $0.1 million and $0.3 million for the same respective periods of 2016 . Tax credits recognized related to these investments totaled $0.8 million and $2.6 million for the three and six months ended June 30, 2017 , respectively, and $1.7 million and $4.2 million for the same respective periods of 2016 . Tax credits recognized reduced income tax expense in the respective periods. Net Realized Investment Gains (Losses) Realized investment gains and losses are recognized on the first-in, first-out basis. The following table provides detailed information regarding Net realized investment gains (losses): Three Months Ended Six Months Ended (In thousands) 2017 2016 2017 2016 Total OTTI losses: Corporate debt $ — $ — $ (419 ) $ (7,604 ) Other investments — — — (3,130 ) Portion of OTTI losses recognized in other comprehensive income before taxes: Corporate debt — — 248 1,068 Net impairment losses recognized in earnings — — (171 ) (9,666 ) Gross realized gains, available-for-sale securities 746 1,885 2,599 5,070 Gross realized (losses), available-for-sale securities (1,401 ) (612 ) (1,468 ) (5,259 ) Net realized gains (losses), Short-term investments — 18 — 18 Net realized gains (losses), trading securities 794 1,913 7,356 3,968 Net realized gains (losses), Other investments 546 447 1,719 498 Change in unrealized holding gains (losses), trading securities (3,191 ) 7,115 424 7,851 Change in unrealized holding gains (losses), convertible securities, carried at fair value 285 162 598 95 Other 2 1 4 3 Net realized investment gains (losses) $ (2,219 ) $ 10,929 $ 11,061 $ 2,578 ProAssurance did no t recognize OTTI during the second quarter of 2017 . During the 2017 six-month period , ProAssurance recognized OTTI in earnings of $0.2 million and $0.2 million in non-credit OTTI in OCI , both of which related to corporate bonds. ProAssurance did no t recognize OTTI during the second quarter of 2016 . ProAssurance recognized OTTI in earnings during the 2016 six-month period of $6.5 million related to corporate bonds, including credit-related OTTI of $5.5 million related to debt instruments from ten issuers in the energy sector. The fair value of the bonds and the credit quality of the issuers had declined and ProAssurance recognized credit-related OTTI to reduce the amortized cost basis of the bonds to the present value of future cash flows expected to be received from the bonds. ProAssurance also recognized non-credit OTTI in OCI during the 2016 six-month period of $0.9 million related to certain of these same bonds, as the fair value of the bonds was less than the present value of the expected future cash flows from the securities. ProAssurance also recognized a $3.1 million OTTI in earnings during the 2016 six-month period related to an investment fund that is accounted for using the cost method (classified as Other investments). The fund is focused on the energy sector and securities held by the fund declined in value during the first quarter of 2016 . An OTTI was recognized to reduce ProAssurance's carrying value of the investment to the NAV reported by the fund. The following table presents a roll forward of cumulative credit losses recorded in earnings related to impaired debt securities for which a portion of the OTTI was recorded in OCI . Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Balance beginning of period $ 1,329 $ 6,559 $ 1,158 $ 5,751 Additional credit losses recognized during the period, related to securities for which: No OTTI has been previously recognized — — 171 2,398 OTTI has been previously recognized — — — 2,154 Reductions due to: Securities sold during the period (realized) (16 ) (3,240 ) (16 ) (6,984 ) Balance June 30 $ 1,313 $ 3,319 $ 1,313 $ 3,319 Other information regarding sales and purchases of available-for-sale securities is as follows: Three Months Ended June 30 Six Months Ended June 30 (In millions) 2017 2016 2017 2016 Proceeds from sales (exclusive of maturities and paydowns) $ 156.3 $ 82.0 $ 235.5 $ 191.9 Purchases $ 198.7 $ 173.6 $ 359.1 $ 373.2

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes ProAssurance estimates its annual effective tax rate at the end of each quarterly reporting period and uses this estimated rate to record the provision for income taxes in the interim financial statements. The provision for income taxes is different from that which would be obtained by applying the statutory Federal income tax rate to income before income taxes primarily because a portion of ProAssurance’s investment income is tax-exempt, and because ProAssurance utilizes tax credit benefits transferred from tax credit partnership investments. ProAssurance had a receivable for Federal and U.K. income taxes of $4.2 million at June 30, 2017 , carried as a part of Other assets and a liability of $5.1 million at December 31, 2016 , carried as a part of Other liabilities. The liability for unrecognized tax benefits was $8.6 million at June 30, 2017 and $8.4 million at December 31, 2016 .

Reserve for Losses and Loss Adj

Reserve for Losses and Loss Adjustment Expenses	6 Months Ended
	Jun. 30, 2017
Insurance [Abstract]
Reserve for Losses and Loss Adjustment Expenses	Reserve for Losses and Loss Adjustment Expenses The reserve for losses is established based on estimates of individual claims and actuarially determined estimates of future losses based on ProAssurance’s past loss experience, available industry data and projections as to future claims frequency, severity, inflationary trends and settlement patterns. Estimating the reserve, particularly the reserve appropriate for liability exposures, is a complex process. Claims may be resolved over an extended period of time, often five years or more, and may be subject to litigation. Estimating losses requires ProAssurance to make and revise judgments and assessments regarding multiple uncertainties over an extended period of time. As a result, the reserve estimate may vary considerably from the eventual outcome. The assumptions used in establishing ProAssurance’s reserve are regularly reviewed and updated by management as new data becomes available. Changes to estimates of previously established reserves are included in earnings in the period in which the estimate is changed. ProAssurance believes that the methods it uses to establish reserves are reasonable and appropriate. Each year, ProAssurance uses internal actuaries to review the reserve for losses of each insurance subsidiary. ProAssurance also engages consulting actuaries to review ProAssurance claims data and provide observations regarding cost trends, rate adequacy and ultimate loss costs. ProAssurance considers the views of the actuaries as well as other factors, such as known, anticipated or estimated changes in frequency and severity of claims, loss retention levels and premium rates, in establishing the amount of its reserve for losses. The statutory filings of each insurance company with the insurance regulators must be accompanied by a consulting actuary's certification as to their respective reserves. ProAssurance partitions its reserve by accident year, which is the year in which the claim becomes its liability. As claims are incurred (reported) and claim payments are made, they are aggregated by accident year for analysis purposes. ProAssurance also partitions its reserve by reserve type: case reserves and IBNR reserves. Case reserves are established by the claims department based upon the particular circumstances of each reported claim and represent ProAssurance’s estimate of the future loss costs (often referred to as expected losses) that will be paid on reported claims. Case reserves are decremented as claim payments are made and are periodically adjusted upward or downward as estimates regarding the amount of future losses are revised; a reported loss for an individual claim equates to the case reserve at any point in time plus the claim payments that have been made to date. IBNR reserves represent an estimate, in the aggregate, of future development on losses that have been reported to ProAssurance plus an estimate of losses that have been incurred but not reported. Development of Prior Accident Years In addition to setting the initial reserve for the current accident year, each period ProAssurance reassesses the amount of reserve required for prior accident years. The foundation of ProAssurance’s reserve re-estimation process is an actuarial analysis that is performed by both the internal and consulting actuaries. This detailed analysis projects ultimate losses on a line of business, geographic, coverage layer and accident year basis. The procedure uses the most representative data for each partition, capturing its unique patterns of development and trends. In all, there are 219 different partitions of ProAssurance's business for purposes of this analysis. ProAssurance believes that the use of consulting actuaries provides an independent view of the loss data as well as a broader perspective on industry loss trends. Activity in the Reserve for losses and loss adjustment expenses is summarized as follows: (In thousands) Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 Year Ended December 31, 2016 Balance, beginning of year $ 1,993,428 $ 2,005,326 $ 2,005,326 Less reinsurance recoverables on unpaid losses and loss adjustment expenses 273,475 249,350 249,350 Net balance, beginning of year 1,719,953 1,755,976 1,755,976 Net losses: Current year 292,489 283,329 587,007 Favorable development of reserves established in prior years, net (57,788 ) (65,475 ) (143,778 ) Total 234,701 217,854 443,229 Paid related to: Current year (33,115 ) (30,651 ) (96,190 ) Prior years (210,006 ) (204,193 ) (383,062 ) Total paid (243,121 ) (234,844 ) (479,252 ) Net balance, end of period 1,711,533 1,738,986 1,719,953 Plus reinsurance recoverables on unpaid losses and loss adjustment expenses 280,332 253,815 273,475 Balance, end of period $ 1,991,865 $ 1,992,801 $ 1,993,428 The favorable loss development of $29.0 million and $57.8 million recognized in the three and six months ended June 30, 2017 , respectively, primarily reflected a lower than anticipated claims severity trend (i.e., the average size of a claim) for accident years 2010 through 2014 . The favorable loss development of $36.8 million and $65.5 million recognized in the three and six months ended June 30, 2016 , respectively, primarily reflected a lower than anticipated claims severity trend for accident years 2009 through 2013 . The favorable loss development of $143.8 million recognized in the twelve months ended December 31, 2016 primarily reflected a lower than anticipated claims severity trend for accident years 2008 through 2014. For additional information regarding ProAssurance's reserve, see Note 1 of the Notes to Consolidated Financial Statements included in ProAssurance's December 31, 2016 Form 10-K.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies ProAssurance is involved in various legal actions related to insurance policies and claims handling including, but not limited to, claims asserted by policyholders. These types of legal actions arise in the Company's ordinary course of business and, in accordance with GAAP for insurance entities, are considered as a part of the Company's loss reserving process, which is described in detail under the heading "Losses and Loss Adjustment Expenses" in the Accounting Policies section in Note 1 of the Notes to Consolidated Financial Statements in ProAssurance's 2016 Form 10-K. ProAssurance has funding commitments primarily related to non-public investment entities totaling approximately $160.7 million , expected to be paid as follows: $57.9 million in 2017 , $67.6 million in 2018 and 2019 combined, $32.2 million in 2020 and 2021 combined and $3.0 million thereafter. Of these funding commitments, $1.3 million are related to qualified affordable housing project tax credit investments and are expected to be paid as follows: $0.3 million in 2017 , $0.3 million in 2018 and 2019 combined, $0.3 million in 2020 and 2021 combined and $0.4 million thereafter. As a member of Lloyd's ProAssurance is required to provide capital to support Syndicate 1729 through 2022 of up to $200 million , referred to as FAL . At June 30, 2017 , ProAssurance is satisfying the FAL requirement with investment securities on deposit with Lloyd's with a carrying value of $98.2 million (see Note 3 of the Notes to Condensed Consolidated Financial Statements). ProAssurance has issued an unconditional revolving credit agreement to the Premium Trust Fund of Syndicate 1729 for the purpose of providing working capital. Permitted borrowings are £20.0 million under an amended Syndicate Credit Agreement executed in April 2016. Under the amended Syndicate Credit Agreement advances bear interest at 3.8% annually, and may be repaid at any time but are repayable upon demand after December 31, 2019 . As of June 30, 2017 , the unused commitment under the Syndicate Credit Agreement approximated £10.9 million (approximately $14.2 million as of June 30, 2017 ). In conjunction with a strategic business partnership ProAssurance entered into during the third quarter of 2016, ProAssurance issued a line of credit of up to $9.0 million for the purpose of funding the entity's operations. The line of credit is non-interest bearing and may be repaid at any time but is repayable upon demand on or before August 31, 2017 . As of June 30, 2017 , the unused commitment under the line of credit approximated $4.5 million .

Debt

Debt	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Debt	Debt ProAssurance’s outstanding debt consisted of the following: (In thousands) June 30, December 31, Senior notes due 2023, unsecured, interest at 5.3% annually $ 250,000 $ 250,000 Revolving Credit Agreement, outstanding borrowings are fully secured, see Note 3, and carried at a weighted average interest rate of 1.66% and 1.35%, respectively. Outstanding borrowings are not permitted to exceed $250 million aggregately; Revolving Credit Agreement expires in 2020. The interest rate on the borrowings is set at the time the respective borrowing is initiated or renewed. The current borrowings can be repaid or renewed in the third quarter 2017. If renewed, the interest rate will be reset. 178,000 200,000 Total principal 428,000 450,000 Less debt issuance costs 1,626 1,798 Debt less debt issuance costs $ 426,374 $ 448,202 Covenant Compliance There are no financial covenants associated with the Senior Notes due 2023. The Revolving Credit Agreement contains customary representations, covenants and events constituting default, and remedies for default. The Revolving Credit Agreement also defines financial covenants regarding permitted leverage ratios. ProAssurance is currently in compliance with all covenants of the Revolving Credit Agreement . Additional Information For additional information regarding ProAssurance's debt, see Note 10 of the Notes to Consolidated Financial Statements included in ProAssurance's December 31, 2016 Form 10-K.

Shareholders' Equity

Shareholders' Equity	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity At June 30, 2017 and December 31, 2016 , ProAssurance had 100 million shares of authorized common stock and 50 million shares of authorized preferred stock. The Board has the authority to determine provisions for the issuance of preferred shares, including the number of shares to be issued, the designations, powers, preferences and rights, and the qualifications, limitations or restrictions of such shares. To date, the Board has not approved the issuance of preferred stock. ProAssurance declared cash dividends of $0.31 per share during both the first and second quarters of 2017 , totaling $33.0 million . ProAssurance declared cash dividends of $0.31 per share during both the first and second quarters of 2016 , totaling $32.9 million . At June 30, 2017 , Board authorizations for the repurchase of common shares or the retirement of outstanding debt of $109.6 million remained available for use. ProAssurance did no t repurchase any common shares during the six months ended June 30, 2017 and repurchased approximately 44,500 shares at a cost of $2.1 million during the six months ended June 30, 2016 . Share-based compensation expense and related tax benefits were as follows: Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Share-based compensation expense $ 2,746 $ 3,098 $ 6,092 $ 5,813 Related tax benefits $ 961 $ 1,084 $ 2,132 $ 2,035 ProAssurance awarded approximately 84,600 restricted share units and 48,000 base performance share units to employees in February 2017 . The fair value of each unit awarded was estimated at $58.35 , equal to the market value of a ProAssurance common share on the date of grant less the estimated present value of dividends during the vesting period. All awards are charged to expense as an increase to equity over the service period (generally the vesting period) associated with the award. Restricted share units and performance share units vest in their entirety at the end of a three -year period following the grant date based on a continuous service requirement and, for performance share units, achievement of a performance objective. Partial vesting is permitted for retirees. A ProAssurance common share is issued for each unit once vesting requirements are met, except that units sufficient to satisfy required tax withholdings are paid in cash. The number of common shares issued for performance share units varies from 50% to 200% of base awards depending upon the degree to which stated performance objectives are achieved. ProAssurance issued approximately 29,300 and 99,500 common shares to employees in February 2017 related to restricted share units and performance share units, respectively, granted in 2014. Performance share units for the 2014 award were issued at levels ranging from 117% to 125% . ProAssurance issued approximately 9,000 common shares to employees in February 2017 as bonus compensation, as approved by the Compensation Committee of the Board. The shares issued were valued at fair value (the market price of a ProAssurance common share on the date of award). Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) For the three and six months ended June 30, 2017 and 2016 , OCI was primarily comprised of unrealized gains and losses, including non-credit impairment losses, arising during the period related to available-for-sale securities, less reclassification adjustments, as shown in the table that follows, net of tax. For the six months ended June 30, 2016 , OCI included a gain of $0.5 million , net of tax, related to changes from the reestimation of two defined benefit plans assumed in the Eastern acquisition, one of which was terminated late in 2016. The remaining plan is frozen as to the earnings of additional benefits, but the unrecognized plan benefit liability is reestimated annually. At June 30, 2017 and December 31, 2016 , AOCI was primarily comprised of unrealized gains and losses from available-for-sale securities, including non-credit impairments recognized in OCI of $0.5 million and $0.3 million , respectively, net of tax. During 2016 , as discussed above, one of the defined benefit plans assumed in the Eastern acquisition was terminated and the related unrecognized losses were reclassified from AOCI to earnings. At June 30, 2017 and December 31, 2016 , unrecognized changes in the remaining defined benefit plan liability were nominal in amount. All tax effects were computed using a 35% rate, with the exception of unrealized gains and losses on available-for-sale securities held at our U.K. and Cayman Island entities which were immaterial in amount. Amounts reclassified from AOCI to Net income and the amounts of deferred tax expense (benefit) included in OCI were as follows: Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Reclassifications from AOCI to Net income: Realized investment gains (losses) $ (653 ) $ 2,024 $ 963 $ (4,443 ) Non-credit impairment losses reclassified to earnings, due to sale of securities or reclassification as a credit loss (3 ) (753 ) (3 ) (2,279 ) Total amounts reclassified, before tax effect (656 ) 1,271 960 (6,722 ) Tax effect (at 35%) 230 (445 ) (336 ) 2,353 Net reclassification adjustments $ (426 ) $ 826 $ 624 $ (4,369 ) Deferred tax expense (benefit) included in OCI $ 2,983 $ 7,541 $ 4,464 $ 19,801

Variable Interest Entities

Variable Interest Entities	6 Months Ended
	Jun. 30, 2017
Variable Interest Entities [Abstract]
Variable Interest Entities	Variable Interest Entities ProAssurance holds passive interests in a number of entities that are considered to be VIE s under GAAP guidance. ProAssurance's VIE interests principally consist of interests in LP s/ LLC s formed for the purpose of achieving diversified equity and debt returns. ProAssurance's VIE interests carried as a part of Other investments totaled $27.0 million at June 30, 2017 and $26.9 million at December 31, 2016 . ProAssurance's VIE interests carried as a part of Investment in unconsolidated subsidiaries totaled $270.5 million at June 30, 2017 and $282.3 million at December 31, 2016 . ProAssurance does not have power over the activities that most significantly impact the economic performance of these VIE s and thus is not the primary beneficiary. Therefore, ProAssurance has not consolidated these VIE s. ProAssurance’s involvement with each entity is limited to its direct ownership interest in the entity. Except as disclosed in Note 6 of the Notes to Condensed Consolidated Financial Statements, ProAssurance has no arrangements with any of the entities to provide other financial support to or on behalf of the entity. At June 30, 2017 , ProAssurance’s maximum loss exposure relative to these investments was limited to the carrying value of ProAssurance’s investment in the VIE .

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Diluted weighted average shares is calculated as basic weighted average shares plus the effect, calculated using the treasury stock method, of assuming that performance and restricted share units and purchase match units have vested. All outstanding performance and restricted share units and purchase match units had a dilutive effect for the three and six months ended June 30, 2017 and 2016 .

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information ProAssurance operates in four segments that are organized around the nature of the products and services provided: Specialty P&C , Workers' Compensation, Lloyd's Syndicate, and Corporate. A description of each segment follows. Specialty P&C is primarily focused on professional liability insurance and medical technology liability insurance. Professional liability insurance is primarily offered to healthcare providers and institutions and to attorneys and their firms. Medical technology liability insurance is offered to medical technology and life sciences companies that manufacture or distribute products including entities conducting human clinical trials. The Specialty P&C segment cedes certain premium to the Lloyd's Syndicate segment under a quota share agreement with Syndicate 1729 . As discussed below, Syndicate 1729 operating results are reported on a quarter delay. For consistency purposes, results from this ceding arrangement, other than cash receipts or disbursements, have been reported within the Specialty P&C segment on the same one-quarter delay. Workers' Compensation provides workers' compensation products primarily to employers with 1,000 or fewer employees. The segment also offers alternative market solutions whereby policies written are 100% ceded either to captive insurers unaffiliated with ProAssurance or to SPC s operated by a wholly owned subsidiary of ProAssurance. Each SPC is owned, fully or in part, by an agency, group or association. Operating results (underwriting profit or loss, plus investment results reported in the Corporate segment) of the SPC s are due to the owners of that cell. Lloyd's Syndicate includes operating results from ProAssurance's 58% participation in Lloyd's of London Syndicate 1729 . Syndicate 1729 underwrites risks over a wide range of property and casualty insurance and reinsurance lines in both the U.S. and international markets. The results of this segment are reported on a quarter delay, except that investment results associated with investment assets solely allocated to Syndicate 1729 operations and certain U.S. paid administrative expenses are reported concurrently as that information is available on an earlier time frame. Corporate includes ProAssurance's investment operations, interest expense and U.S. income taxes, all of which are managed at the corporate level with the exception of investment assets solely allocated to Syndicate 1729 as discussed above. The segment also includes non-premium revenues generated outside of our insurance entities and corporate expenses. The accounting policies of the segments are the same as those described in Note 1 of the Notes to Consolidated Financial Statements in ProAssurance’s December 31, 2016 report on Form 10-K and Note 1 of the Notes to Condensed Consolidated Financial Statements. ProAssurance evaluates performance of its Specialty P&C and Workers' Compensation segments based on before tax underwriting profit or loss, which excludes investment performance. Performance of the Lloyd's Syndicate segment is evaluated based on underwriting profit or loss, plus investment results of investment assets solely allocated to Syndicate 1729 operations, net of U.K. income tax expense. Performance of the Corporate segment is evaluated based on the contribution made to consolidated after tax results. ProAssurance accounts for inter-segment transactions as if the transactions were to third parties at current market prices. Assets are not allocated to segments because investments and other assets are not managed at the segment level. Financial results by segment were as follows: Three Months Ended June 30, 2017 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 109,005 $ 56,854 $ 14,494 $ — $ — $ 180,353 Net investment income — — 410 22,267 — 22,677 Equity in earnings (loss) of unconsolidated subsidiaries — — — 2,516 — 2,516 Net realized gains (losses) — — 47 (2,266 ) — (2,219 ) Other income 1,469 209 (151 ) 778 (55 ) 2,250 Net losses and loss adjustment expenses (71,296 ) (33,486 ) (10,768 ) — — (115,550 ) Underwriting, policy acquisition and operating expenses (26,239 ) (17,093 ) (6,851 ) (7,757 ) 55 (57,885 ) Segregated portfolio cells dividend (expense) income (1)(2) (5,119 ) (2,698 ) — (994 ) — (8,811 ) Interest expense — — — (4,145 ) — (4,145 ) Income tax benefit (expense) (2) — — 548 (216 ) — 332 Segment operating results $ 7,820 $ 3,786 $ (2,271 ) $ 10,183 $ — $ 19,518 Significant non-cash items: Depreciation and amortization, net of accretion $ 1,506 $ 831 $ (5 ) $ 3,814 $ — $ 6,146 Six Months Ended June 30, 2017 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 222,063 $ 112,137 $ 29,056 $ — $ — $ 363,256 Net investment income — — 782 45,081 — 45,863 Equity in earnings (loss) of unconsolidated subsidiaries — — — 4,324 — 4,324 Net realized gains (losses) — — 74 10,987 — 11,061 Other income 2,668 354 240 951 (142 ) 4,071 Net losses and loss adjustment expenses (146,291 ) (68,136 ) (20,274 ) — — (234,701 ) Underwriting, policy acquisition and operating expenses (52,217 ) (33,784 ) (13,062 ) (16,073 ) 142 (114,994 ) Segregated portfolio cells dividend (expense) income (1)(2) (5,091 ) (3,872 ) — (2,223 ) — (11,186 ) Interest expense — — — (8,278 ) — (8,278 ) Income tax benefit (expense) (2) — — 555 1,002 — 1,557 Segment operating results $ 21,132 $ 6,699 $ (2,629 ) $ 35,771 $ — $ 60,973 Significant non-cash items: Depreciation and amortization, net of accretion $ 3,417 $ 1,668 $ (8 ) $ 8,872 $ — $ 13,949 Three Months Ended June 30, 2016 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 108,126 $ 55,093 $ 13,513 $ — $ — $ 176,732 Net investment income — — 337 24,246 — 24,583 Equity in earnings (loss) of unconsolidated subsidiaries — — — 376 — 376 Net realized gains (losses) — — 14 10,915 — 10,929 Other income 1,732 139 188 286 (164 ) 2,181 Net losses and loss adjustment expenses (3) (62,301 ) (34,661 ) (8,502 ) — (1,435 ) (106,899 ) Underwriting, policy acquisition and operating expenses (3) (25,902 ) (16,334 ) (5,240 ) (8,157 ) 1,599 (54,034 ) Segregated portfolio cells dividend (expense) income (1) — (1,277 ) — (246 ) — (1,523 ) Interest expense — — — (3,851 ) — (3,851 ) Income tax benefit (expense) — — (812 ) (4,601 ) — (5,413 ) Segment operating results $ 21,655 $ 2,960 $ (502 ) $ 18,968 $ — $ 43,081 Significant non-cash items: Depreciation and amortization, net of accretion $ 1,486 $ 1,393 $ 43 $ 5,421 $ — $ 8,343 Six Months Ended June 30, 2016 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 218,882 $ 109,476 $ 25,954 $ — $ — $ 354,312 Net investment income — — 653 49,370 — 50,023 Equity in earnings (loss) of unconsolidated subsidiaries — — — (3,259 ) — (3,259 ) Net realized gains (losses) — — 8 2,570 — 2,578 Other income 3,008 610 440 744 (267 ) 4,535 Net losses and loss adjustment expenses (3) (133,477 ) (69,687 ) (14,690 ) — — (217,854 ) Underwriting, policy acquisition and operating expenses (3) (50,954 ) (34,165 ) (10,406 ) (15,665 ) 267 (110,923 ) Segregated portfolio cells dividend (expense) income (1) — (1,990 ) — (709 ) — (2,699 ) Interest expense — — — (7,537 ) — (7,537 ) Income tax benefit (expense) — — (897 ) (5,880 ) — (6,777 ) Segment operating results $ 37,459 $ 4,244 $ 1,062 $ 19,634 $ — $ 62,399 Significant non-cash items: Depreciation and amortization, net of accretion $ 3,497 $ 2,797 $ 109 $ 10,568 $ — $ 16,971 (1) During the first quarter of 2017, ProAssurance began reporting in the Corporate segment the portion of the SPC dividend (expense) income that is attributable to the investment results of the SPCs, all of which are reported in the Corporate segment, to better align the expense with the related investment results of the SPCs. For comparative purposes, ProAssurance has reflected the SPC dividend expense for 2016 in the same manner. (2) During the second quarter of 2017, ProAssurance recognized a $5.2 million pre-tax expense related to previously unrecognized SPC dividend expense for the cumulative earnings of unrelated parties that have owned segregated portfolio cells at various periods since 2003 in a Bermuda captive insurance operation managed by the Company's HCPL line of business within the Specialty P&C segment. The expense recorded in the second quarter of 2017 related to periods prior to the current period and is unrelated to the captive operations of the Company's Eastern Re subsidiary. The $1.8 million tax impact of the expense recognized in the second quarter of 2017 is reflected as an income tax benefit in the Corporate segment. (3) During the second quarter of 2016, ProAssurance discontinued the practice of eliminating in consolidation the portion of the management fee that was allocated to ULAE and reversed the elimination that was recorded in the first quarter of 2016. Thus, there was no management fee elimination recorded in ULAE for the 2016 six-month period and no similar elimination for the 2017 three- and six-month periods. The following table provides detailed information regarding ProAssurance's gross premiums earned by product as well as a reconciliation to net premiums earned. All gross premiums earned are from external customers except as noted. ProAssurance's insured risks are primarily within the U.S. Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Specialty P&C Segment Gross premiums earned: Healthcare professional liability $ 115,781 $ 111,938 $ 232,832 $ 225,687 Legal professional liability 6,417 6,493 12,734 13,107 Medical technology liability 8,389 8,243 16,701 16,794 Other 101 154 203 421 Ceded premiums earned (21,683 ) (18,702 ) (40,407 ) (37,127 ) Segment net premiums earned 109,005 108,126 222,063 218,882 Workers' Compensation Segment Gross premiums earned: Traditional business 42,501 42,193 84,269 84,844 Alternative market business 20,209 18,805 39,655 37,099 Ceded premiums earned (5,856 ) (5,905 ) (11,787 ) (12,467 ) Segment net premiums earned 56,854 55,093 112,137 109,476 Lloyd's Syndicate Segment Gross premiums earned: Property and casualty* 16,960 13,859 34,145 27,231 Ceded premiums earned (2,466 ) (346 ) (5,089 ) (1,277 ) Segment net premiums earned 14,494 13,513 29,056 25,954 Consolidated Net premiums earned $ 180,353 $ 176,732 $ 363,256 $ 354,312 *Includes premium assumed from the Specialty P&C segment of $3.1 million and $6.6 million for the three and six months ended June 30, 2017 , respectively, and $3.4 million and $7.0 million for the three and six months ended June 30, 2016 .

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events In July 2017, ProAssurance repaid $17 million of the balance outstanding on the Revolving Credit Agreement (see Note 7 of the Notes to Condensed Consolidated Financial Statements for further discussion of the terms of the Revolving Credit Agreement ).

Basis of Presentation (Policies

Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounting Changes Adopted and Not Yet Adopted	Accounting Changes Adopted Improvements to Employee Share-Based Payment Accounting Effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, the FASB issued guidance that simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of cash flows, and the classification of awards as either equity or liabilities. Under the new guidance, the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes is to be recognized as income tax expense in the current period and included with other income tax cash flows as an operating activity. The threshold for equity classification has also been revised to permit withholdings up to the maximum statutory tax rates in the applicable jurisdictions. The update also provides an accounting policy election to account for forfeitures as they occur. ProAssurance adopted the guidance as of January 1, 2017. The primary effects of the adoption on the current period are the following: (1) using a prospective application, ProAssurance recorded unrecognized excess tax benefits of $0.3 million and $2.6 million for the three and six months ended June 30, 2017 , respectively, as a current tax expense, (2) using a modified retrospective application, ProAssurance elected to recognize forfeitures as they occur and recorded a $0.4 million increase to Additional paid-in capital and a respective $0.3 million reduction to Retained earnings and a $0.1 million increase to deferred taxes to reflect the incremental share-based compensation expense, net of related tax impacts, that would have been recognized in prior years under the modified guidance and (3) excess tax benefits from share-based compensation of $2.3 million was reclassified from financing activities to operating activities in the Condensed Consolidated Statements of Cash Flows. Interests Held Through Related Parties that are Under Common Control Effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, the FASB issued additional guidance regarding consolidation of legal entities such as LP s/ LLC s and securitization structures (collateralized debt obligations, collateralized loan obligations, and mortgage-backed security transactions). The new guidance modifies the criteria used by a reporting entity when determining if it is a primary beneficiary of a VIE when there are entities under common control and the reporting entity has indirect interests in the VIE through related party relationships. ProAssurance adopted the guidance as of January 1, 2017. Adoption of the guidance had no material effect on ProAssurance’s results of operations or financial position. Simplifying the Transition to the Equity Method of Accounting Effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, the FASB issued guidance that eliminates the requirement for retroactive restatement when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence. The new guidance provides that the cost of acquiring an additional interest in an investee is to be added to the current basis of an investor’s previously held interest and the equity method of accounting adopted as of the date the investment becomes qualified for equity method accounting with no retroactive adjustment of the investment. If an available-for-sale equity security qualifies for the equity method of accounting, the unrealized holding gain or loss in AOCI is to be recognized through earnings at the date the investment becomes qualified for use of the equity method. ProAssurance adopted the guidance as of January 1, 2017. Adoption of the guidance had no material effect on ProAssurance’s results of operations or financial position. Accounting Changes Not Yet Adopted Clarifying the Definition of a Business Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance which provides clarification of the definition of a business, affecting areas such as acquisitions, disposals, goodwill and consolidation. The new guidance intends to assist entities with determining whether a transaction should be accounted for as an acquisition or disposal of assets or a business. ProAssurance plans to early adopt the guidance during 2017 for any acquisitions or dispositions. Adoption is not expected to have a material effect on ProAssurance’s results of operations or financial position. Restricted Cash Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance related to the classification of restricted cash presented in the statement of cash flows with the objective of reducing diversity in practice. Under the new guidance, entities are required to include restricted cash and restricted cash equivalents with cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts as presented on the statement of cash flows. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption is not expected to have a material effect on ProAssurance’s results of operations, financial position or cash flows. Intra-Entity Transfers of Assets Other than Inventory Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance which reduces the complexity in accounting standards related to the income tax consequences of intra-entity transfers of assets other than inventory. Under the new guidance, entities are required to recognize income tax consequences of an intra-entity transfer of assets other than inventory when the transfer occurs instead of delaying recognition until the asset has been sold to an outside party. ProAssurance is in the process of evaluating the effect the new guidance would have on its results of operations and financial position and plans to adopt the guidance beginning January 1, 2018. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Classification of Certain Cash Receipts and Cash Payments Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance related to the classification of certain cash receipts and cash payments presented in the statement of cash flows with the objective of reducing diversity in practice. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption is not expected to have a material effect on ProAssurance’s results of operations, financial position or cash flows. Revenue from Contracts with Customers Effective for fiscal years beginning after December 15, 2017 the FASB issued guidance related to revenue from contracts with customers. The core principle of the new guidance is that revenue is recognized to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ProAssurance plans to adopt the guidance beginning January 1, 2018. As the majority of ProAssurance's revenues come from insurance contracts which fall under the scope of other FASB standards, adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Recognition and Measurement of Financial Assets and Financial Liabilities Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance that requires 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. The new guidance also specifies that an entity use the exit price notion when measuring the fair value of financial instruments for disclosure purposes and present financial assets and liabilities by measurement category and form of financial asset. Other provisions of the new guidance include: revised disclosure requirements related to the presentation in comprehensive income of changes in the fair value of liabilities; elimination, for public companies, of disclosure requirements relative to the method(s) and significant assumptions underlying fair values disclosed for financial instruments measured at amortized cost; and simplified impairment assessments for equity investments without readily determinable fair values. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Modification Accounting for Employee Share-Based Payment Awards Effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years, the FASB issued guidance which reduces the complexity in accounting standards when there is a change in the terms or conditions of a share-based payment award. The new guidance clarifies that an entity should apply the modification accounting guidance if the value, vesting conditions or classification of the award changes. ProAssurance plans to adopt the guidance beginning January 1, 2018. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Premium Amortization on Purchased Callable Debt Securities Effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years, the FASB issued guidance that will require the premium for certain callable debt securities to be amortized over a shorter period than is currently required. Currently amortization is permitted over the contractual life of the instrument and the guidance shortens the amortization to the earliest call date. The purpose of the guidance is to more closely align the amortization period of premiums to expectations incorporated in market pricing on the underlying securities. ProAssurance plans to adopt the guidance beginning January 1, 2019. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position. Leases Effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years, the FASB issued guidance that requires a lessee to recognize for all leases (with the exception of short-term leases) a lease liability, which is a lessee's obligation to make lease payments arising from a lease, measured on a discounted basis, and a right-of-use asset, which is an asset that represents the lessee's right to use, or control the use of, a specified asset for the lease term. ProAssurance plans to adopt the guidance beginning January 1, 2019. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position as ProAssurance does not have any leases it believes to be material. Simplifying the Test for Goodwill Impairment Effective for the fiscal years beginning after December 15, 2019 and interim periods within those fiscal years, the FASB issued guidance that simplifies the requirements to test goodwill for impairment for business entities that have goodwill reported in their financial statements. The guidance eliminates the second step of the impairment test which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount. In addition, the guidance also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment. ProAssurance plans to adopt the guidance beginning January 1, 2020. Adoption is not expected to have a material effect on ProAssurance’s results of operations or financial position. Improvements to Financial Instruments - Credit Losses Effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years, the FASB issued guidance that replaces the incurred loss impairment methodology, which delays recognition of credit losses until a probable loss has been incurred, with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. Under the new guidance, credit losses are required to be recorded through an allowance for credit losses account and the income statement reflects the measurement for newly recognized financial assets, as well as increases or decreases of expected credit losses that have taken place during the period. ProAssurance is in the process of evaluating the effect the new guidance would have on its results of operations and financial position and plans to adopt the guidance beginning January 1, 2020. Adoption of the guidance is not expected to have a material effect on ProAssurance’s results of operations or financial position.
Reclassifications	Reclassifications In the second quarter of 2017, ProAssurance began presenting separately the components of Underwriting, policy acquisition and operating expense as Operating expense and DPAC amortization on the Condensed Consolidated Statements of Income and Comprehensive Income in order to provide additional details for investors. The Condensed Consolidated Statements of Income and Comprehensive Income for the three and six months ended June 30, 2016 have been reclassified to conform to the current period presentation. Total Underwriting, policy acquisition and operating expense as well as Net income for all periods presented was not affected by the change in presentation.
Fair Value Policy	The fair values for securities included in the Level 2 category, with the few exceptions described below, were developed by one of several third party, nationally recognized pricing services, including services that price only certain types of securities. Each service uses complex methodologies to determine values for securities and subject the values they develop to quality control reviews. Management selected a primary source for each type of security in the portfolio and reviewed the values provided for reasonableness by comparing data to alternate pricing services and to available market and trade data. Values that appeared inconsistent were further reviewed for appropriateness. Any value that did not appear reasonable was discussed with the service that provided the value and adjusted, if necessary. There were no material changes to the values supplied by the pricing services during the three and six months ended June 30, 2017 and 2016 . Level 2 Valuations Below is a summary description of the valuation methodologies primarily used by the pricing services for securities in the Level 2 category, by security type: U.S. Treasury obligations were valued based on quoted prices for identical assets, or, in markets that are not active, quotes for similar assets, taking into consideration adjustments for variations in contractual cash flows and yields to maturity. U.S. Government-sponsored enterprise obligations were valued using pricing models that consider current and historical market data, normal trading conventions, credit ratings, and the particular structure and characteristics of the security being valued, such as yield to maturity, redemption options, and contractual cash flows. Adjustments to model inputs or model results were included in the valuation process when necessary to reflect recent regulatory, government or corporate actions or significant economic, industry or geographic events affecting the security’s fair value. State and municipal bonds were valued using a series of matrices that considered credit ratings, the structure of the security, the sector in which the security falls, yields, and contractual cash flows. Valuations were further adjusted, when necessary, to reflect the expected effect on fair value of recent significant economic or geographic events or ratings changes. Corporate debt, multiple observable inputs consisted primarily of corporate bonds, but also included a small number of bank loans. The methodology used to value Level 2 corporate bonds was the same as the methodology previously described for U.S. Government-sponsored enterprise obligations. Bank loans were valued based on an average of broker quotes for the loans in question, if available. If quotes were not available, the loans were valued based on quoted prices for comparable loans or, if the loan was newly issued, by comparison to similar seasoned issues. Broker quotes were compared to actual trade prices to permit assessment of the reliability of the quotes; unreliable quotes were not considered in quoted averages. Residential and commercial mortgage-backed securities were valued using a pricing matrix which considers the issuer type, coupon rate and longest cash flows outstanding. The matrix used was based on the most recently available market information. Agency and non-agency collateralized mortgage obligations were both valued using models that consider the structure of the security, current and historical information regarding prepayment speeds, ratings and ratings updates, and current and historical interest rate and interest rate spread data. Other asset-backed securities were valued using models that consider the structure of the security, monthly payment information, current and historical information regarding prepayment speeds, ratings and ratings updates, and current and historical interest rate and interest rate spread data. Spreads and prepayment speeds consider collateral type. Equity securities were securities not traded on an exchange on the valuation date. The securities were valued using the most recently available quotes for the securities. Short-term investments are securities maturing within one year, carried at cost which approximated the fair value of the security due to the short term to maturity. Other investments consisted primarily of convertible bonds valued using a pricing model that incorporated selected dealer quotes as well as current market data regarding equity prices and risk free rates. If dealer quotes were unavailable for the security being valued, quotes for securities with similar terms and credit status were used in the pricing model. Dealer quotes selected for use were those considered most accurate based on parameters such as underwriter status and historical reliability. Level 3 Valuations Below is a summary description of the valuation processes and methodologies used as well as quantitative information regarding securities in the Level 3 category. Level 3 Valuation Processes • Level 3 securities are priced by the Chief Investment Officer. • Level 3 valuations are computed quarterly. Prices are evaluated quarterly against prior period prices and the expected change in prices. • ProAssurance's Level 3 securities are primarily NRSRO rated debt instruments for which comparable market inputs are commonly available for evaluating the securities in question. Valuation of these debt instruments is not overly sensitive to changes in the unobservable inputs used. Level 3 Valuation Methodologies Corporate debt, limited observable inputs consisted of corporate bonds valued using dealer quotes for similar securities or discounted cash flow models using yields currently available for similar securities. Similar securities are defined as securities of comparable credit quality that have like terms and payment features. Assessments of credit quality were based on NRSRO ratings, if available, or were subjectively determined by management if not available. At June 30, 2017 , 77% of the securities were rated and the average rating was BBB+ . At December 31, 2016 , 84% of the securities were rated and the average rating was BBB+ . Other asset-backed securities consisted of securitizations of receivables valued using dealer quotes for similar securities or discounted cash flow models using yields currently available for similar securities. Other investments consisted of convertible securities for which limited observable inputs were available at June 30, 2017 and at December 31, 2016 . The securities were valued internally based on expected cash flows, including the expected final recovery, discounted at a yield that considered the lack of liquidity and the financial status of the issuer.

Basis of Presentation (Tables)

Basis of Presentation (Tables)	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Other Liabilities	Other liabilities consisted of the following: (In thousands) June 30, 2017 December 31, 2016 SPC dividends payable $ 40,625 $ 34,289 Unpaid dividends 16,524 265,659 All other 112,661 122,337 Total other liabilities $ 169,810 $ 422,285

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value	Fair values of assets measured at fair value on a recurring basis as of June 30, 2017 and December 31, 2016 are shown in the following tables. Where applicable, the tables also indicate the fair value hierarchy of the valuation techniques utilized to determine those fair values. For some assets, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. When this is the case, the asset is categorized based on the level of the most significant input to the fair value measurement. Assessments of the significance of a particular input to the fair value measurement require judgment and consideration of factors specific to the assets being valued. June 30, 2017 Fair Value Measurements Using Total (In thousands) Level 1 Level 2 Level 3 Fair Value Assets: Fixed maturities, available for sale U.S. Treasury obligations $ — $ 143,453 $ — $ 143,453 U.S. Government-sponsored enterprise obligations — 20,192 — 20,192 State and municipal bonds — 721,836 — 721,836 Corporate debt, multiple observable inputs 2,406 1,292,473 — 1,294,879 Corporate debt, limited observable inputs — — 17,849 17,849 Residential mortgage-backed securities — 206,415 — 206,415 Agency commercial mortgage-backed securities — 11,960 — 11,960 Other commercial mortgage-backed securities — 17,157 — 17,157 Other asset-backed securities — 109,361 3,005 112,366 Equity securities Financial 82,324 — — 82,324 Utilities/Energy 44,687 — — 44,687 Consumer oriented 56,079 — — 56,079 Industrial 49,635 — — 49,635 Bond funds 116,025 — — 116,025 All other 62,156 — — 62,156 Short-term investments 251,486 12,215 — 263,701 Other investments 963 29,846 5 30,814 Total assets categorized within the fair value hierarchy $ 665,761 $ 2,564,908 $ 20,859 3,251,528 LP/LLC interests carried at NAV which approximates fair value. These interests, reported as a part of Investment in unconsolidated subsidiaries, are not categorized within the fair value hierarchy. 201,154 Total assets at fair value $ 3,452,682 December 31, 2016 Fair Value Measurements Using Total (In thousands) Level 1 Level 2 Level 3 Fair Value Assets: Fixed maturities, available for sale U.S. Treasury obligations $ — $ 146,539 $ — $ 146,539 U.S. Government-sponsored enterprise obligations — 30,235 — 30,235 State and municipal bonds — 800,463 — 800,463 Corporate debt, multiple observable inputs 2,339 1,261,842 — 1,264,181 Corporate debt, limited observable inputs — — 14,810 14,810 Residential mortgage-backed securities — 217,906 — 217,906 Agency commercial mortgage-backed securities — 12,783 — 12,783 Other commercial mortgage-backed securities — 19,611 — 19,611 Other asset-backed securities — 103,871 3,007 106,878 Equity securities Financial 81,749 — — 81,749 Utilities/Energy 52,869 — — 52,869 Consumer oriented 61,284 — — 61,284 Industrial 54,265 — — 54,265 Bond funds 79,843 10,159 — 90,002 All other 27,181 19,924 — 47,105 Short-term investments 437,580 4,504 — 442,084 Other investments 1,956 29,542 3 31,501 Total assets categorized within the fair value hierarchy $ 799,066 $ 2,657,379 $ 17,820 3,474,265 LP/LLC interests carried at NAV which approximates fair value. These interests, reported as a part of Investment in unconsolidated subsidiaries, are not categorized within the fair value hierarchy. 204,719 Total assets at fair value $ 3,678,984
Summary of quantitative information about Level 3 fair value measurements	Quantitative Information Regarding Level 3 Valuations Fair Value at (In thousands) June 30, 2017 December 31, 2016 Valuation Technique Unobservable Input Range Assets: Corporate debt, limited observable inputs $17,849 $14,810 Market Comparable Comparability Adjustment 0% - 5% (2.5%) Discounted Cash Flows Comparability Adjustment 0% - 5% (2.5%) Other asset-backed securities $3,005 $3,007 Market Comparable Comparability Adjustment 0% - 5% (2.5%) Discounted Cash Flows Comparability Adjustment 0% - 5% (2.5%) Other investments $5 $3 Discounted Cash Flows Comparability Adjustment 0% - 10% (5%)
Summary of changes in the fair value of assets measured at fair value	The following tables (the Level 3 Tables) present summary information regarding changes in the fair value of assets measured at fair value using Level 3 inputs. June 30, 2017 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance March 31, 2017 $ 18,914 $ 3,002 $ 903 $ 22,819 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (34 ) — — (34 ) Net realized investment gains (losses) — — (124 ) (124 ) Included in other comprehensive income (70 ) 3 138 71 Purchases 4,841 — — 4,841 Sales (1,848 ) — (912 ) (2,760 ) Transfers in 10 — — 10 Transfers out (3,964 ) — — (3,964 ) Balance June 30, 2017 $ 17,849 $ 3,005 $ 5 $ 20,859 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ — June 30, 2017 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance December 31, 2016 $ 14,810 $ 3,007 $ 3 $ 17,820 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (73 ) — — (73 ) Net realized investment gains (losses) 13 — (124 ) (111 ) Included in other comprehensive income (278 ) (2 ) 140 (140 ) Purchases 11,889 — — 11,889 Sales (3,560 ) — (912 ) (4,472 ) Transfers in 10 — 898 908 Transfers out (4,962 ) — — (4,962 ) Balance June 30, 2017 $ 17,849 $ 3,005 $ 5 $ 20,859 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ — June 30, 2016 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance March 31, 2016 $ 13,649 $ 4,088 $ 1,558 $ 19,295 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (22 ) — (3 ) (25 ) Net realized investment gains (losses) — — — — Included in other comprehensive income 204 7 1 212 Purchases 5,995 — — 5,995 Sales (2,016 ) (535 ) — (2,551 ) Transfers in — — — — Transfers out — (2,805 ) — (2,805 ) Balance June 30, 2016 $ 17,810 $ 755 $ 1,556 $ 20,121 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ — June 30, 2016 Level 3 Fair Value Measurements – Assets (In thousands) Corporate Debt Asset-backed Securities All other investments Total Balance December 31, 2015 $ 14,500 $ 757 $ — $ 15,257 Total gains (losses) realized and unrealized: Included in earnings, as a part of: Net investment income (36 ) — (4 ) (40 ) Net realized investment gains (losses) (75 ) — — (75 ) Included in other comprehensive income 129 5 — 134 Purchases 5,995 3,500 1,560 11,055 Sales (2,697 ) (702 ) — (3,399 ) Transfers in — — — — Transfers out (6 ) (2,805 ) — (2,811 ) Balance June 30, 2016 $ 17,810 $ 755 $ 1,556 $ 20,121 Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end $ — $ — $ — $ —
Investments in Limited liability companies and limited partnerships	Investments in unconsolidated subsidiaries at both June 30, 2017 and December 31, 2016 included interests in investment fund LP s/ LLC s that measure fund assets at fair value on a recurring basis and that provide a NAV for the interest. The carrying value of these interests is based on the NAV provided and was considered to approximate the fair value of the interests. In accordance with GAAP , the fair value of these investments was not classified within the fair value hierarchy. Additional information regarding these investments is as follows: Unfunded Fair Value (In thousands) June 30, June 30, December 31, Investments in LPs/LLCs: Private debt funds (1) $11,247 $ 44,520 $ 55,637 Long equity fund (2) None 7,459 6,268 Long/short equity funds (3) None 30,404 28,926 Non-public equity funds (4) $85,121 91,707 89,691 Multi-strategy fund of funds (5) None 8,783 8,448 Structured credit fund (6) None 6,187 4,273 Long/short commodities fund (7) None 12,094 11,476 $ 201,154 $ 204,719 (1) The investment is comprised of interests in two unrelated LP funds that are structured to provide interest distributions primarily through diversified portfolios of private debt instruments. One LP allows redemption by special consent; the other does not permit redemption. Income and capital are to be periodically distributed at the discretion of the LP s over an anticipated time frame that spans from three to eight years. (2) The fund is a LP that holds long equities of public international companies. Redemptions are allowed at the end of any calendar month with a prior notice requirement of 15 days and are paid within 10 days of the end of the calendar month of the redemption request. (3) The investment is comprised of interests in multiple unrelated LP funds. The funds hold primarily long and short North American equities and target absolute returns using strategies designed to take advantage of market opportunities. The funds generally permit quarterly or semi-annual capital redemptions subject to notice requirements of 30 to 90 days. For some funds, redemptions above specified thresholds (lowest threshold is 90% ) may be only partially payable until after a fund audit is completed and are then payable within 30 days. (4) The investment is comprised of interests in multiple unrelated LP funds, each structured to provide capital appreciation through diversified investments in private equity, which can include investments in buyout, venture capital, debt including senior, second lien and mezzanine, distressed debt, and other private equity-oriented LP s. Two of the LP s allow redemption by terms set forth in the LP agreements; the others do not permit redemption. Income and capital are to be periodically distributed at the discretion of the LP over time frames that are anticipated to span up to nine years. (5) This fund is a LLC structured to build and manage low volatility, multi-manager portfolios that have little or no correlation to the broader fixed income and equity security markets. Redemptions are not permitted but offers to repurchase units of the LLC may be extended periodically. (6) This fund is a LP seeking to obtain superior risk-adjusted absolute returns by acquiring and actively managing a diversified portfolio of debt securities, including bonds, loans and other asset-backed instruments. Redemptions are allowed at any quarter-end with a prior notice requirement of 90 days . (7) This fund is a LLC invested across a broad range of commodities and focuses primarily on market neutral, relative value strategies, seeking to generate absolute returns with low correlation to broad commodity, equity and fixed income markets. Following an initial one-year lock-up period, redemptions are allowed with a prior notice requirement of 30 days and are payable within 30 days.
Financial instruments not measured at fair value	The following table provides the estimated fair value of our financial instruments that, in accordance with GAAP for the type of investment, are measured using a methodology other than fair value. All fair values provided fall within the Level 3 fair value category. June 30, 2017 December 31, 2016 (In thousands) Carrying Fair Carrying Fair Financial assets: BOLI $ 61,031 $ 61,031 $ 60,134 $ 60,134 Other investments $ 49,652 $ 58,704 $ 50,391 $ 58,757 Other assets $ 33,386 $ 33,225 $ 29,111 $ 28,960 Financial liabilities: Senior notes due 2023* $ 250,000 $ 274,610 $ 250,000 $ 270,898 Revolving Credit Agreement* $ 178,000 $ 178,000 $ 200,000 $ 200,000 Other liabilities $ 18,868 $ 18,868 $ 17,033 $ 17,011 * Carrying value excludes debt issuance costs.

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Amortized cost and estimated fair value of available-for-sale fixed maturities and equity securities	Available-for-sale securities at June 30, 2017 and December 31, 2016 included the following: June 30, 2017 (In thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Fixed maturities U.S. Treasury obligations $ 143,088 $ 1,092 $ 727 $ 143,453 U.S. Government-sponsored enterprise obligations 20,179 140 127 20,192 State and municipal bonds 702,688 21,217 2,069 721,836 Corporate debt 1,294,689 23,274 5,235 1,312,728 Residential mortgage-backed securities 204,179 3,369 1,133 206,415 Agency commercial mortgage-backed securities 11,945 77 62 11,960 Other commercial mortgage-backed securities 17,087 152 82 17,157 Other asset-backed securities 112,098 361 93 112,366 $ 2,505,953 $ 49,682 $ 9,528 $ 2,546,107 December 31, 2016 (In thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Fixed maturities U.S. Treasury obligations $ 146,186 $ 1,264 $ 911 $ 146,539 U.S. Government-sponsored enterprise obligations 30,038 388 191 30,235 State and municipal bonds 790,154 17,261 6,952 800,463 Corporate debt 1,264,812 22,659 8,480 1,278,991 Residential mortgage-backed securities 216,285 3,667 2,046 217,906 Agency commercial mortgage-backed securities 12,837 89 143 12,783 Other commercial mortgage-backed securities 19,571 177 137 19,611 Other asset-backed securities 106,938 207 267 106,878 $ 2,586,821 $ 45,712 $ 19,127 $ 2,613,406
Schedule of available for sale securities by contractual maturity	The recorded cost basis and estimated fair value of available-for-sale fixed maturities at June 30, 2017 , by contractual maturity, are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. (In thousands) Amortized Due in one Due after Due after Due after Total Fair Fixed maturities, available for sale U.S. Treasury obligations $ 143,088 $ 29,357 $ 92,270 $ 18,815 $ 3,011 $ 143,453 U.S. Government-sponsored enterprise obligations 20,179 499 7,873 11,678 142 20,192 State and municipal bonds 702,688 54,052 243,955 308,236 115,593 721,836 Corporate debt 1,294,689 138,176 733,558 418,955 22,039 1,312,728 Residential mortgage-backed securities 204,179 206,415 Agency commercial mortgage-backed securities 11,945 11,960 Other commercial mortgage-backed securities 17,087 17,157 Other asset-backed securities 112,098 112,366 $ 2,505,953 $ 2,546,107
Unconsolidated subsidiaries	ProAssurance holds investments in unconsolidated subsidiaries, accounted for under the equity method. The investments include the following: Carrying Value (In thousands) June 30, December 31, Investment in LPs/LLCs: Qualified affordable housing tax credit partnerships $ 95,041 $ 102,313 Other tax credit partnerships 8,976 11,459 All other LPs/LLCs 226,312 227,134 $ 330,329 $ 340,906
Other investments	Other investments at June 30, 2017 and December 31, 2016 were comprised as follows: (In thousands) June 30, December 31, Investments in LPs/LLCs, at cost $ 46,200 $ 46,852 Convertible securities, at fair value 30,814 31,501 Other, principally FHLB capital stock, at cost 3,452 3,539 $ 80,466 $ 81,892
Investments held in an unrealized loss position	The following tables provide summarized information with respect to investments held in an unrealized loss position at June 30, 2017 and December 31, 2016 , including the length of time the investment had been held in a continuous unrealized loss position. June 30, 2017 Total Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Fair Unrealized (In thousands) Value Loss Value Loss Value Loss Fixed maturities, available for sale U.S. Treasury obligations $ 83,416 $ 727 $ 78,080 $ 664 $ 5,336 $ 63 U.S. Government-sponsored enterprise obligations 15,907 127 15,907 127 — — State and municipal bonds 111,522 2,069 103,371 1,441 8,151 628 Corporate debt 372,586 5,235 336,877 3,167 35,709 2,068 Residential mortgage-backed securities 89,610 1,133 87,491 1,086 2,119 47 Agency commercial mortgage-backed securities 4,568 62 4,188 34 380 28 Other commercial mortgage-backed securities 9,147 82 7,457 65 1,690 17 Other asset-backed securities 40,149 93 38,264 91 1,885 2 $ 726,905 $ 9,528 $ 671,635 $ 6,675 $ 55,270 $ 2,853 December 31, 2016 Total Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Fair Unrealized (In thousands) Value Loss Value Loss Value Loss Fixed maturities, available for sale U.S. Treasury obligations $ 79,833 $ 911 $ 79,833 $ 911 $ — $ — U.S. Government-sponsored enterprise obligations 11,746 191 11,746 191 — — State and municipal bonds 224,884 6,952 219,276 6,444 5,608 508 Corporate debt 469,632 8,480 424,721 5,662 44,911 2,818 Residential mortgage-backed securities 103,680 2,046 100,542 1,982 3,138 64 Agency commercial mortgage-backed securities 4,579 143 4,192 114 387 29 Other commercial mortgage-backed securities 9,822 137 9,179 134 643 3 Other asset-backed securities 44,343 267 39,079 256 5,264 11 $ 948,519 $ 19,127 $ 888,568 $ 15,694 $ 59,951 $ 3,433
Net Investment Income	Net investment income by investment category was as follows: Three Months Ended Six Months Ended (In thousands) 2017 2016 2017 2016 Fixed maturities $ 18,841 $ 21,208 $ 38,962 $ 43,784 Equities 4,298 3,561 7,942 7,204 Short-term and Other investments 978 678 1,778 1,082 BOLI 442 439 897 899 Investment fees and expenses (1,882 ) (1,303 ) (3,716 ) (2,946 ) Net investment income $ 22,677 $ 24,583 $ 45,863 $ 50,023
Net realized investment gains (losses)	The following table provides detailed information regarding Net realized investment gains (losses): Three Months Ended Six Months Ended (In thousands) 2017 2016 2017 2016 Total OTTI losses: Corporate debt $ — $ — $ (419 ) $ (7,604 ) Other investments — — — (3,130 ) Portion of OTTI losses recognized in other comprehensive income before taxes: Corporate debt — — 248 1,068 Net impairment losses recognized in earnings — — (171 ) (9,666 ) Gross realized gains, available-for-sale securities 746 1,885 2,599 5,070 Gross realized (losses), available-for-sale securities (1,401 ) (612 ) (1,468 ) (5,259 ) Net realized gains (losses), Short-term investments — 18 — 18 Net realized gains (losses), trading securities 794 1,913 7,356 3,968 Net realized gains (losses), Other investments 546 447 1,719 498 Change in unrealized holding gains (losses), trading securities (3,191 ) 7,115 424 7,851 Change in unrealized holding gains (losses), convertible securities, carried at fair value 285 162 598 95 Other 2 1 4 3 Net realized investment gains (losses) $ (2,219 ) $ 10,929 $ 11,061 $ 2,578
Other than temporary impairment, credit losses recognized in earnings	The following table presents a roll forward of cumulative credit losses recorded in earnings related to impaired debt securities for which a portion of the OTTI was recorded in OCI . Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Balance beginning of period $ 1,329 $ 6,559 $ 1,158 $ 5,751 Additional credit losses recognized during the period, related to securities for which: No OTTI has been previously recognized — — 171 2,398 OTTI has been previously recognized — — — 2,154 Reductions due to: Securities sold during the period (realized) (16 ) (3,240 ) (16 ) (6,984 ) Balance June 30 $ 1,313 $ 3,319 $ 1,313 $ 3,319
Information regarding sales and purchases of available-for-sale securities	Other information regarding sales and purchases of available-for-sale securities is as follows: Three Months Ended June 30 Six Months Ended June 30 (In millions) 2017 2016 2017 2016 Proceeds from sales (exclusive of maturities and paydowns) $ 156.3 $ 82.0 $ 235.5 $ 191.9 Purchases $ 198.7 $ 173.6 $ 359.1 $ 373.2

Reserve for Losses and Loss A23

Reserve for Losses and Loss Adjustment Expenses (Tables)	6 Months Ended
	Jun. 30, 2017
Insurance [Abstract]
Summary of reserve for losses and loss adjustment expenses	Activity in the Reserve for losses and loss adjustment expenses is summarized as follows: (In thousands) Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 Year Ended December 31, 2016 Balance, beginning of year $ 1,993,428 $ 2,005,326 $ 2,005,326 Less reinsurance recoverables on unpaid losses and loss adjustment expenses 273,475 249,350 249,350 Net balance, beginning of year 1,719,953 1,755,976 1,755,976 Net losses: Current year 292,489 283,329 587,007 Favorable development of reserves established in prior years, net (57,788 ) (65,475 ) (143,778 ) Total 234,701 217,854 443,229 Paid related to: Current year (33,115 ) (30,651 ) (96,190 ) Prior years (210,006 ) (204,193 ) (383,062 ) Total paid (243,121 ) (234,844 ) (479,252 ) Net balance, end of period 1,711,533 1,738,986 1,719,953 Plus reinsurance recoverables on unpaid losses and loss adjustment expenses 280,332 253,815 273,475 Balance, end of period $ 1,991,865 $ 1,992,801 $ 1,993,428

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	ProAssurance’s outstanding debt consisted of the following: (In thousands) June 30, December 31, Senior notes due 2023, unsecured, interest at 5.3% annually $ 250,000 $ 250,000 Revolving Credit Agreement, outstanding borrowings are fully secured, see Note 3, and carried at a weighted average interest rate of 1.66% and 1.35%, respectively. Outstanding borrowings are not permitted to exceed $250 million aggregately; Revolving Credit Agreement expires in 2020. The interest rate on the borrowings is set at the time the respective borrowing is initiated or renewed. The current borrowings can be repaid or renewed in the third quarter 2017. If renewed, the interest rate will be reset. 178,000 200,000 Total principal 428,000 450,000 Less debt issuance costs 1,626 1,798 Debt less debt issuance costs $ 426,374 $ 448,202

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Schedule of Share-based compensation expense and related tax benefits	Share-based compensation expense and related tax benefits were as follows: Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Share-based compensation expense $ 2,746 $ 3,098 $ 6,092 $ 5,813 Related tax benefits $ 961 $ 1,084 $ 2,132 $ 2,035
Reclassification adjustments related to available-for-sale securities	Amounts reclassified from AOCI to Net income and the amounts of deferred tax expense (benefit) included in OCI were as follows: Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Reclassifications from AOCI to Net income: Realized investment gains (losses) $ (653 ) $ 2,024 $ 963 $ (4,443 ) Non-credit impairment losses reclassified to earnings, due to sale of securities or reclassification as a credit loss (3 ) (753 ) (3 ) (2,279 ) Total amounts reclassified, before tax effect (656 ) 1,271 960 (6,722 ) Tax effect (at 35%) 230 (445 ) (336 ) 2,353 Net reclassification adjustments $ (426 ) $ 826 $ 624 $ (4,369 ) Deferred tax expense (benefit) included in OCI $ 2,983 $ 7,541 $ 4,464 $ 19,801

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Financial results by segment were as follows: Three Months Ended June 30, 2017 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 109,005 $ 56,854 $ 14,494 $ — $ — $ 180,353 Net investment income — — 410 22,267 — 22,677 Equity in earnings (loss) of unconsolidated subsidiaries — — — 2,516 — 2,516 Net realized gains (losses) — — 47 (2,266 ) — (2,219 ) Other income 1,469 209 (151 ) 778 (55 ) 2,250 Net losses and loss adjustment expenses (71,296 ) (33,486 ) (10,768 ) — — (115,550 ) Underwriting, policy acquisition and operating expenses (26,239 ) (17,093 ) (6,851 ) (7,757 ) 55 (57,885 ) Segregated portfolio cells dividend (expense) income (1)(2) (5,119 ) (2,698 ) — (994 ) — (8,811 ) Interest expense — — — (4,145 ) — (4,145 ) Income tax benefit (expense) (2) — — 548 (216 ) — 332 Segment operating results $ 7,820 $ 3,786 $ (2,271 ) $ 10,183 $ — $ 19,518 Significant non-cash items: Depreciation and amortization, net of accretion $ 1,506 $ 831 $ (5 ) $ 3,814 $ — $ 6,146 Six Months Ended June 30, 2017 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 222,063 $ 112,137 $ 29,056 $ — $ — $ 363,256 Net investment income — — 782 45,081 — 45,863 Equity in earnings (loss) of unconsolidated subsidiaries — — — 4,324 — 4,324 Net realized gains (losses) — — 74 10,987 — 11,061 Other income 2,668 354 240 951 (142 ) 4,071 Net losses and loss adjustment expenses (146,291 ) (68,136 ) (20,274 ) — — (234,701 ) Underwriting, policy acquisition and operating expenses (52,217 ) (33,784 ) (13,062 ) (16,073 ) 142 (114,994 ) Segregated portfolio cells dividend (expense) income (1)(2) (5,091 ) (3,872 ) — (2,223 ) — (11,186 ) Interest expense — — — (8,278 ) — (8,278 ) Income tax benefit (expense) (2) — — 555 1,002 — 1,557 Segment operating results $ 21,132 $ 6,699 $ (2,629 ) $ 35,771 $ — $ 60,973 Significant non-cash items: Depreciation and amortization, net of accretion $ 3,417 $ 1,668 $ (8 ) $ 8,872 $ — $ 13,949 Three Months Ended June 30, 2016 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 108,126 $ 55,093 $ 13,513 $ — $ — $ 176,732 Net investment income — — 337 24,246 — 24,583 Equity in earnings (loss) of unconsolidated subsidiaries — — — 376 — 376 Net realized gains (losses) — — 14 10,915 — 10,929 Other income 1,732 139 188 286 (164 ) 2,181 Net losses and loss adjustment expenses (3) (62,301 ) (34,661 ) (8,502 ) — (1,435 ) (106,899 ) Underwriting, policy acquisition and operating expenses (3) (25,902 ) (16,334 ) (5,240 ) (8,157 ) 1,599 (54,034 ) Segregated portfolio cells dividend (expense) income (1) — (1,277 ) — (246 ) — (1,523 ) Interest expense — — — (3,851 ) — (3,851 ) Income tax benefit (expense) — — (812 ) (4,601 ) — (5,413 ) Segment operating results $ 21,655 $ 2,960 $ (502 ) $ 18,968 $ — $ 43,081 Significant non-cash items: Depreciation and amortization, net of accretion $ 1,486 $ 1,393 $ 43 $ 5,421 $ — $ 8,343 Six Months Ended June 30, 2016 (In thousands) Specialty P&C Workers' Compensation Lloyd's Syndicate Corporate Inter-segment Eliminations Consolidated Net premiums earned $ 218,882 $ 109,476 $ 25,954 $ — $ — $ 354,312 Net investment income — — 653 49,370 — 50,023 Equity in earnings (loss) of unconsolidated subsidiaries — — — (3,259 ) — (3,259 ) Net realized gains (losses) — — 8 2,570 — 2,578 Other income 3,008 610 440 744 (267 ) 4,535 Net losses and loss adjustment expenses (3) (133,477 ) (69,687 ) (14,690 ) — — (217,854 ) Underwriting, policy acquisition and operating expenses (3) (50,954 ) (34,165 ) (10,406 ) (15,665 ) 267 (110,923 ) Segregated portfolio cells dividend (expense) income (1) — (1,990 ) — (709 ) — (2,699 ) Interest expense — — — (7,537 ) — (7,537 ) Income tax benefit (expense) — — (897 ) (5,880 ) — (6,777 ) Segment operating results $ 37,459 $ 4,244 $ 1,062 $ 19,634 $ — $ 62,399 Significant non-cash items: Depreciation and amortization, net of accretion $ 3,497 $ 2,797 $ 109 $ 10,568 $ — $ 16,971 (1) During the first quarter of 2017, ProAssurance began reporting in the Corporate segment the portion of the SPC dividend (expense) income that is attributable to the investment results of the SPCs, all of which are reported in the Corporate segment, to better align the expense with the related investment results of the SPCs. For comparative purposes, ProAssurance has reflected the SPC dividend expense for 2016 in the same manner. (2) During the second quarter of 2017, ProAssurance recognized a $5.2 million pre-tax expense related to previously unrecognized SPC dividend expense for the cumulative earnings of unrelated parties that have owned segregated portfolio cells at various periods since 2003 in a Bermuda captive insurance operation managed by the Company's HCPL line of business within the Specialty P&C segment. The expense recorded in the second quarter of 2017 related to periods prior to the current period and is unrelated to the captive operations of the Company's Eastern Re subsidiary. The $1.8 million tax impact of the expense recognized in the second quarter of 2017 is reflected as an income tax benefit in the Corporate segment. (3) During the second quarter of 2016, ProAssurance discontinued the practice of eliminating in consolidation the portion of the management fee that was allocated to ULAE and reversed the elimination that was recorded in the first quarter of 2016. Thus, there was no management fee elimination recorded in ULAE for the 2016 six-month period and no similar elimination for the 2017 three- and six-month periods.
Schedule of Gross Premiums by Product	The following table provides detailed information regarding ProAssurance's gross premiums earned by product as well as a reconciliation to net premiums earned. All gross premiums earned are from external customers except as noted. ProAssurance's insured risks are primarily within the U.S. Three Months Ended June 30 Six Months Ended June 30 (In thousands) 2017 2016 2017 2016 Specialty P&C Segment Gross premiums earned: Healthcare professional liability $ 115,781 $ 111,938 $ 232,832 $ 225,687 Legal professional liability 6,417 6,493 12,734 13,107 Medical technology liability 8,389 8,243 16,701 16,794 Other 101 154 203 421 Ceded premiums earned (21,683 ) (18,702 ) (40,407 ) (37,127 ) Segment net premiums earned 109,005 108,126 222,063 218,882 Workers' Compensation Segment Gross premiums earned: Traditional business 42,501 42,193 84,269 84,844 Alternative market business 20,209 18,805 39,655 37,099 Ceded premiums earned (5,856 ) (5,905 ) (11,787 ) (12,467 ) Segment net premiums earned 56,854 55,093 112,137 109,476 Lloyd's Syndicate Segment Gross premiums earned: Property and casualty* 16,960 13,859 34,145 27,231 Ceded premiums earned (2,466 ) (346 ) (5,089 ) (1,277 ) Segment net premiums earned 14,494 13,513 29,056 25,954 Consolidated Net premiums earned $ 180,353 $ 176,732 $ 363,256 $ 354,312 *Includes premium assumed from the Specialty P&C segment of $3.1 million and $6.6 million for the three and six months ended June 30, 2017 , respectively, and $3.4 million and $7.0 million for the three and six months ended June 30, 2016 .

Basis of Presentation (Details

Basis of Presentation (Details Textual) $ in Thousands		3 Months Ended	6 Months Ended
		Jun. 30, 2017USD ($)	Jun. 30, 2017USD ($)segment	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment			4
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrecognized excess tax benefits recognized as current tax expense		$ 300	$ 2,600
Operating activities in Condensed Consolidated Statements of Cash Flow			54,014	$ 86,231
Financing activities in Condensed Consolidated Statements of Cash Flow			(308,969)	$ (85,888)
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment- ASU 2016-09 adoption	[1]				$ 149
Operating activities in Condensed Consolidated Statements of Cash Flow			2,300
Financing activities in Condensed Consolidated Statements of Cash Flow			$ (2,300)
Accounting Standards Update 2016-09 [Member] | Additional Paid-in Capital [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment- ASU 2016-09 adoption	[1]				425
Accounting Standards Update 2016-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment- ASU 2016-09 adoption	[1]				$ (276)
[1]	See Note 1 of the Notes to Condensed Consolidated Financial Statements for discussion of accounting guidance adopted during the period.

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
SPC dividends payable	$ 40,625	$ 34,289
Unpaid dividends	16,524	265,659	$ 16,461
All other	112,661	122,337
Total other liabilities	$ 169,810	$ 422,285

Fair Value Measurement (Assets

Fair Value Measurement (Assets and Liabilities Measured at Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Assets:
Equity securities	$ 410,906	$ 387,274
Other investments	80,466	81,892
LP/LLC interests carried at NAV which approximates fair value. These interests, reported as a part of Investment in unconsolidated subsidiaries, are not categorized within the fair value hierarchy.	201,154	204,719
Level 3 [Member] | Corporate debt with limited observable inputs [Member]
Assets:
Total assets categorized within the fair value hierarchy	17,849	14,810
Level 3 [Member] | Other asset-backed securities [Member]
Assets:
Total assets categorized within the fair value hierarchy	3,005	3,007
Fair Value, Measurements, Recurring [Member]
Assets:
Other investments	30,814	31,501
Total assets categorized within the fair value hierarchy	3,251,528	3,474,265
LP/LLC interests carried at NAV which approximates fair value. These interests, reported as a part of Investment in unconsolidated subsidiaries, are not categorized within the fair value hierarchy.	201,154	204,719
Total assets at fair value, including NAV value not within fair value hierarchy	3,452,682	3,678,984
Fair Value, Measurements, Recurring [Member] | U.S. Treasury obligations [Member]
Assets:
Fixed maturities, available for sale	143,453	146,539
Fair Value, Measurements, Recurring [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fixed maturities, available for sale	20,192	30,235
Fair Value, Measurements, Recurring [Member] | State and municipal bonds [Member]
Assets:
Fixed maturities, available for sale	721,836	800,463
Fair Value, Measurements, Recurring [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fixed maturities, available for sale	1,294,879	1,264,181
Fair Value, Measurements, Recurring [Member] | Corporate debt with limited observable inputs [Member]
Assets:
Fixed maturities, available for sale	17,849	14,810
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	206,415	217,906
Fair Value, Measurements, Recurring [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	11,960	12,783
Fair Value, Measurements, Recurring [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	17,157	19,611
Fair Value, Measurements, Recurring [Member] | Other asset-backed securities [Member]
Assets:
Fixed maturities, available for sale	112,366	106,878
Fair Value, Measurements, Recurring [Member] | Financial [Member]
Assets:
Equity securities	82,324	81,749
Fair Value, Measurements, Recurring [Member] | Utilities/Energy [Member]
Assets:
Equity securities	44,687	52,869
Fair Value, Measurements, Recurring [Member] | Consumer oriented [Member]
Assets:
Equity securities	56,079	61,284
Fair Value, Measurements, Recurring [Member] | Industrial [Member]
Assets:
Equity securities	49,635	54,265
Fair Value, Measurements, Recurring [Member] | Bond funds [Member]
Assets:
Equity securities	116,025	90,002
Fair Value, Measurements, Recurring [Member] | All other [Member]
Assets:
Equity securities	62,156	47,105
Fair Value, Measurements, Recurring [Member] | Short-term investments [Member]
Assets:
Short-term investments	263,701	442,084
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets:
Other investments	963	1,956
Total assets categorized within the fair value hierarchy	665,761	799,066
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury obligations [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | State and municipal bonds [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fixed maturities, available for sale	2,406	2,339
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate debt with limited observable inputs [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Residential mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other asset-backed securities [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Financial [Member]
Assets:
Equity securities	82,324	81,749
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Utilities/Energy [Member]
Assets:
Equity securities	44,687	52,869
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Consumer oriented [Member]
Assets:
Equity securities	56,079	61,284
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Industrial [Member]
Assets:
Equity securities	49,635	54,265
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Bond funds [Member]
Assets:
Equity securities	116,025	79,843
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | All other [Member]
Assets:
Equity securities	62,156	27,181
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Short-term investments [Member]
Assets:
Short-term investments	251,486	437,580
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets:
Other investments	29,846	29,542
Total assets categorized within the fair value hierarchy	2,564,908	2,657,379
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury obligations [Member]
Assets:
Fixed maturities, available for sale	143,453	146,539
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fixed maturities, available for sale	20,192	30,235
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | State and municipal bonds [Member]
Assets:
Fixed maturities, available for sale	721,836	800,463
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fixed maturities, available for sale	1,292,473	1,261,842
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate debt with limited observable inputs [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Residential mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	206,415	217,906
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	11,960	12,783
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	17,157	19,611
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other asset-backed securities [Member]
Assets:
Fixed maturities, available for sale	109,361	103,871
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Financial [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Utilities/Energy [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Consumer oriented [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Industrial [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Bond funds [Member]
Assets:
Equity securities	0	10,159
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | All other [Member]
Assets:
Equity securities	0	19,924
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Short-term investments [Member]
Assets:
Short-term investments	12,215	4,504
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets:
Other investments	5	3
Total assets categorized within the fair value hierarchy	20,859	17,820
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury obligations [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | State and municipal bonds [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate debt with limited observable inputs [Member]
Assets:
Fixed maturities, available for sale	17,849	14,810
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Residential mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fixed maturities, available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other asset-backed securities [Member]
Assets:
Fixed maturities, available for sale	3,005	3,007
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Financial [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Utilities/Energy [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Consumer oriented [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Industrial [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Bond funds [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | All other [Member]
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Short-term investments [Member]
Assets:
Short-term investments	$ 0	$ 0

Fair Value Measurement (Narrati

Fair Value Measurement (Narrative) (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017USD ($)Agreement	Dec. 31, 2016	Jun. 30, 2016USD ($)
Credit Derivatives [Line Items]
Number of line of credit agreement | Agreement	2
Equity securities [Member]
Credit Derivatives [Line Items]
Transfer of equity securities from Level 2 to Level 1 | $	$ 35.4		$ 0
Standard & Poor's, BBB Rating [Member] | Corporate debt with limited observable inputs [Member]
Credit Derivatives [Line Items]
Credit rating	77.00%
NRSRO | Standard & Poor's, BBB+ Rating [Member] | Corporate debt with limited observable inputs [Member]
Credit Derivatives [Line Items]
Credit rating		84.00%

Fair Value Measurement (Quantit

Fair Value Measurement (Quantitative Information Regarding Level 3 Valuations) (Details) - Level 3 [Member] - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Corporate debt with limited observable inputs [Member]
Assets:
Fair Value at	$ 17,849	$ 14,810
Corporate debt with limited observable inputs [Member] | Market comparable securities valuation technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Corporate debt with limited observable inputs [Member] | Market comparable securities valuation technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Corporate debt with limited observable inputs [Member] | Market comparable securities valuation technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%
Corporate debt with limited observable inputs [Member] | Discount cash flows valuation technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Corporate debt with limited observable inputs [Member] | Discount cash flows valuation technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Corporate debt with limited observable inputs [Member] | Discount cash flows valuation technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%
Other asset-backed securities [Member]
Assets:
Fair Value at	$ 3,005	3,007
Other asset-backed securities [Member] | Market comparable securities valuation technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Other asset-backed securities [Member] | Market comparable securities valuation technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Other asset-backed securities [Member] | Market comparable securities valuation technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%
Other asset-backed securities [Member] | Discount cash flows valuation technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Other asset-backed securities [Member] | Discount cash flows valuation technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Other asset-backed securities [Member] | Discount cash flows valuation technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%
Other investments [Member]
Assets:
Fair Value at	$ 5	$ 3
Other investments [Member] | Discount cash flows valuation technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Other investments [Member] | Discount cash flows valuation technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	10.00%
Other investments [Member] | Discount cash flows valuation technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	5.00%

Fair Value Measurement (Level 3

Fair Value Measurement (Level 3 Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	$ 22,819	$ 19,295	$ 17,820	$ 15,257
Included in earnings, as a part of:
Included in other comprehensive income	71	212	(140)	134
Purchases	4,841	5,995	11,889	11,055
Sales	(2,760)	(2,551)	(4,472)	(3,399)
Transfers in	10	0	908	0
Transfers out	(3,964)	(2,805)	(4,962)	(2,811)
Ending Balance	20,859	20,121	20,859	20,121
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0	0	0
Net investment Income [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	(34)	(25)	(73)	(40)
Net realized investment gains (losses) [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	(124)	0	(111)	(75)
Corporate debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	18,914	13,649	14,810	14,500
Included in earnings, as a part of:
Included in other comprehensive income	(70)	204	(278)	129
Purchases	4,841	5,995	11,889	5,995
Sales	(1,848)	(2,016)	(3,560)	(2,697)
Transfers in	10	0	10	0
Transfers out	(3,964)	0	(4,962)	(6)
Ending Balance	17,849	17,810	17,849	17,810
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0	0	0
Corporate debt [Member] | Net investment Income [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	(34)	(22)	(73)	(36)
Corporate debt [Member] | Net realized investment gains (losses) [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	0	0	13	(75)
Asset-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	3,002	4,088	3,007	757
Included in earnings, as a part of:
Included in other comprehensive income	3	7	(2)	5
Purchases	0	0	0	3,500
Sales	0	(535)	0	(702)
Transfers in	0	0	0	0
Transfers out	0	(2,805)	0	(2,805)
Ending Balance	3,005	755	3,005	755
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0	0	0
Asset-backed securities [Member] | Net investment Income [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	0	0	0	0
Asset-backed securities [Member] | Net realized investment gains (losses) [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	0	0	0	0
All other investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	903	1,558	3	0
Included in earnings, as a part of:
Included in other comprehensive income	138	1	140	0
Purchases	0	0	0	1,560
Sales	(912)	0	(912)	0
Transfers in	0	0	898	0
Transfers out	0	0	0	0
Ending Balance	5	1,556	5	1,556
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0	0	0
All other investments [Member] | Net investment Income [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	0	(3)	0	(4)
All other investments [Member] | Net realized investment gains (losses) [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	$ (124)	$ 0	$ (124)	$ 0

Fair Value Measurement (Investm

Fair Value Measurement (Investments in LLCs and Limited Partnerships) (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments in LPs/LLCs fair value	$ 201,154,000	$ 204,719,000
Private debt fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	11,247,000
Investments in LPs/LLCs fair value	44,520,000	55,637,000
Long equity fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	7,459,000	6,268,000
Long/Short equity funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	30,404,000	28,926,000
Non-public equity funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	85,121,000
Investments in LPs/LLCs fair value	91,707,000	89,691,000
Multi-strategy fund of funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	8,783,000	8,448,000
Structured credit fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	6,187,000	4,273,000
Long/Short commodities fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	$ 12,094,000	$ 11,476,000

Fair Value Measurement (Inves34

Fair Value Measurement (Investments in LLCs and Limited Partnerships Footnote) (Details)	6 Months Ended
	Jun. 30, 2017
Long equity fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment redemption notice period	15 days
Payment period for redemption of LP valued at NAV	10 days
Long/Short Equity Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Payment period for redemption of LP valued at NAV	30 days
Redemption percentage of LP at NAV for which initial payment is limited	90.00%
Non-public equity funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Liquidating investments remaining period	9 years
Structured credit fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment redemption notice period	90 days
Long/Short commodities fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment redemption notice period	30 days
Minimum [Member] | Secured debt fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Liquidating investments remaining period	3 years
Minimum [Member] | Long/Short Equity Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment redemption notice period	30 days
Maximum [Member] | Secured debt fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Liquidating investments remaining period	8 years
Maximum [Member] | Long/Short Equity Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment redemption notice period	90 days
Maximum [Member] | Long/Short commodities fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Payment period for redemption of LP valued at NAV	30 days

Fair Value Measurement (Methodo

Fair Value Measurement (Methodologies Other Than Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financial assets:
BOLI	$ 61,031	$ 60,134
Other investments	80,466	81,892
Other assets	101,530	96,004
Financial liabilities:
Debt	426,374	448,202
Total other liabilities	169,810	422,285
Not Measured At Fair Value [Member] | Carrying Value [Member]
Financial assets:
BOLI	61,031	60,134
Other investments	49,652	50,391
Other assets	33,386	29,111
Financial liabilities:
Total other liabilities	18,868	17,033
Not Measured At Fair Value [Member] | Carrying Value [Member] | Senior notes due 2023 [Member]
Financial liabilities:
Debt	250,000	250,000
Not Measured At Fair Value [Member] | Carrying Value [Member] | Revolving Credit Facility [Member]
Financial liabilities:
Debt	178,000	200,000
Not Measured At Fair Value [Member] | Level 3 [Member] | Fair Value [Member]
Financial assets:
BOLI	61,031	60,134
Other investments	58,704	58,757
Other assets	33,225	28,960
Financial liabilities:
Total other liabilities	18,868	17,011
Not Measured At Fair Value [Member] | Level 3 [Member] | Fair Value [Member] | Senior notes due 2023 [Member]
Financial liabilities:
Debt	274,610	270,898
Not Measured At Fair Value [Member] | Level 3 [Member] | Fair Value [Member] | Revolving Credit Facility [Member]
Financial liabilities:
Debt	$ 178,000	$ 200,000

Investments (Available-For-Sale

Investments (Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Debt Securities [Member]
Fixed maturities, available for sale
Amortized Cost	$ 2,505,953	$ 2,586,821
Gross Unrealized Gains	49,682	45,712
Gross Unrealized Losses	9,528	19,127
Estimated Fair Value	2,546,107	2,613,406
U.S. Treasury obligations [Member]
Fixed maturities, available for sale
Amortized Cost	143,088	146,186
Gross Unrealized Gains	1,092	1,264
Gross Unrealized Losses	727	911
Estimated Fair Value	143,453	146,539
U.S. Government-sponsored enterprise obligations [Member]
Fixed maturities, available for sale
Amortized Cost	20,179	30,038
Gross Unrealized Gains	140	388
Gross Unrealized Losses	127	191
Estimated Fair Value	20,192	30,235
State and municipal bonds [Member]
Fixed maturities, available for sale
Amortized Cost	702,688	790,154
Gross Unrealized Gains	21,217	17,261
Gross Unrealized Losses	2,069	6,952
Estimated Fair Value	721,836	800,463
Corporate debt [Member]
Fixed maturities, available for sale
Amortized Cost	1,294,689	1,264,812
Gross Unrealized Gains	23,274	22,659
Gross Unrealized Losses	5,235	8,480
Estimated Fair Value	1,312,728	1,278,991
Residential mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	204,179	216,285
Gross Unrealized Gains	3,369	3,667
Gross Unrealized Losses	1,133	2,046
Estimated Fair Value	206,415	217,906
Agency commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	11,945	12,837
Gross Unrealized Gains	77	89
Gross Unrealized Losses	62	143
Estimated Fair Value	11,960	12,783
Other commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	17,087	19,571
Gross Unrealized Gains	152	177
Gross Unrealized Losses	82	137
Estimated Fair Value	17,157	19,611
Other asset-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	112,098	106,938
Gross Unrealized Gains	361	207
Gross Unrealized Losses	93	267
Estimated Fair Value	$ 112,366	$ 106,878

Investments (Available For Sale

Investments (Available For Sale Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Debt Securities [Member]
Fixed maturities, available for sale
Amortized Cost	$ 2,505,953	$ 2,586,821
Estimated Fair Value	2,546,107	2,613,406
U.S. Treasury obligations [Member]
Fixed maturities, available for sale
Amortized Cost	143,088	146,186
Due in one year or less	29,357
Due after one year through five years	92,270
Due after five years through ten years	18,815
Due after ten years	3,011
Estimated Fair Value	143,453	146,539
U.S. Government-sponsored enterprise obligations [Member]
Fixed maturities, available for sale
Amortized Cost	20,179	30,038
Due in one year or less	499
Due after one year through five years	7,873
Due after five years through ten years	11,678
Due after ten years	142
Estimated Fair Value	20,192	30,235
State and municipal bonds [Member]
Fixed maturities, available for sale
Amortized Cost	702,688	790,154
Due in one year or less	54,052
Due after one year through five years	243,955
Due after five years through ten years	308,236
Due after ten years	115,593
Estimated Fair Value	721,836	800,463
Corporate debt [Member]
Fixed maturities, available for sale
Amortized Cost	1,294,689	1,264,812
Due in one year or less	138,176
Due after one year through five years	733,558
Due after five years through ten years	418,955
Due after ten years	22,039
Estimated Fair Value	1,312,728	1,278,991
Residential mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	204,179	216,285
Estimated Fair Value	206,415	217,906
Agency commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	11,945	12,837
Estimated Fair Value	11,960	12,783
Other commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	17,087	19,571
Estimated Fair Value	17,157	19,611
Other asset-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	112,098	106,938
Estimated Fair Value	$ 112,366	$ 106,878

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017USD ($)AffiliateBusinessIssuerinvestment_interestSecurity	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)AffiliateBusinessIssuerinvestment_interestSecurity	Jun. 30, 2016USD ($)Issuer	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)IssuerSecurity	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Schedule of Available-for-sale Securities [Line Items]
Number of investment affiliates exceeding shareholder's equity ten percent threshold limit | Affiliate	0		0
Threshold limit of investments based on shareholders' equity	10.00%		10.00%
Securities on deposit with state insurance departments	$ 46,400		$ 46,400
Business owned life insurance cost	33,000		33,000
Investment in unconsolidated subsidiaries	330,329		330,329			$ 340,906
Investments in LPs/LLCs fair value	$ 201,154		$ 201,154			204,719
Number of LPs / LLCs with investment ownership percent over 25% | Business	3		3
Equity in earnings, losses from affordable housing projects	$ (4,000)	$ (3,000)	$ (7,300)	$ (8,300)
Affordable housing tax credits	4,600	4,600	9,200	9,300
Losses from historic tax credit investments	(2,400)	(100)	(2,800)	(300)
Tax credits recognized related to historic tax credit investments	800	1,700	2,600	4,200
Net impairment losses recognized in earnings	0	0	171	9,666
Portion of noncredit OTTI losses recognized in OCI	0	0	248	1,068
Credit-related other-than-temporary impairment recognized in earnings	1,313	3,319	1,313	3,319	$ 1,329	1,158	$ 6,559	$ 5,751
Other than Temporary Impairment Losses, Investments	$ 0	0	$ 419	10,734
Tax Credit Partnerships Almost 100% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of tax credit partnerships almost 100% ownership percentage | investment_interest	2		2
Investment in unconsolidated subsidiaries	$ 36,400		$ 36,400			40,200
Tax Credit Partnerships Less Than 20% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment in unconsolidated subsidiaries	58,600		58,600			62,100
Other Limited Partnerships and Limited Liability Company, Not Considered Investment Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment in unconsolidated subsidiaries	$ 25,100		$ 25,100			22,400
Other Limited Partnerships and Limited Liability Company, Greater Than 25% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity method investment ownership percentage	25.00%		25.00%
Investment in unconsolidated subsidiaries	$ 20,900		$ 20,900			18,500
Other Limited Partnerships and Limited Liability Company Less than 25% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity method investment ownership percentage	25.00%		25.00%
Investment in unconsolidated subsidiaries	$ 205,400		$ 205,400			$ 208,600
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Period for federal home loan bank stock liquidation process			5 years
Maximum [Member] | Tax Credit Partnerships Almost 100% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity method investment ownership percentage	100.00%		100.00%
Maximum [Member] | Tax Credit Partnerships Less Than 20% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity method investment ownership percentage	20.00%		20.00%
Fixed maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Required FAL Deposit	$ 94,800		$ 94,800
Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Required FAL Deposit	$ 3,400		$ 3,400
Non Government-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of debt securities in unrealized loss position | Security	534		534			703
Debt securities in unrealized loss position as percentage of total debt securities held	21.40%		21.40%			27.20%
Number of issuers in unrealized loss position | Issuer	363		363			456
Single greatest unrealized loss position	$ 500		$ 500			$ 500
Second greatest unrealized loss position	300		300			$ 500
Corporate debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Portion of noncredit OTTI losses recognized in OCI	0	0	248	1,068
Credit-related other-than-temporary impairment recognized in earnings		5,500		$ 5,500
Debt securities, number of issuers | Issuer				10
Other than Temporary Impairment Losses, Investments	0	0	419	$ 7,604
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Net impairment losses recognized in earnings				6,500
Portion of noncredit OTTI losses recognized in OCI				900
Other investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Net impairment losses recognized in earnings				3,100
Other than Temporary Impairment Losses, Investments	0	$ 0	0	$ 3,130
Revolving Credit Facility [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities pledged as collateral	$ 239,800		$ 239,800

Investments (Unconsolidated Sub

Investments (Unconsolidated Subsidiaries) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	$ 330,329	$ 340,906
Qualified affordable housing tax credit partnerships [Member]
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	95,041	102,313
Other tax credit partnerships [Member]
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	8,976	11,459
All Other LPs/LLCs [Member]
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	$ 226,312	$ 227,134

Investments (Other Investments)

Investments (Other Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Other Investments
Other investments	$ 80,466	$ 81,892
Investments in LPs/LLCs, at cost [Member]
Other Investments
Other investments	46,200	46,852
Convertible securities, at fair value [Member]
Other Investments
Other investments	30,814	31,501
Other, principally FHLB capital stock at cost [Member]
Other Investments
Other investments	$ 3,452	$ 3,539

Investments (Investments Held i

Investments (Investments Held in a Loss Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Debt Securities [Member]
Investments held in an unrealized loss position
Fair Value	$ 726,905	$ 948,519
Unrealized Loss	9,528	19,127
Less than 12 months, Fair Value	671,635	888,568
Less than 12 months, Unrealized Loss	6,675	15,694
More than 12 months, Fair Value	55,270	59,951
More than 12 months, Unrealized Loss	2,853	3,433
U.S. Treasury obligations [Member]
Investments held in an unrealized loss position
Fair Value	83,416	79,833
Unrealized Loss	727	911
Less than 12 months, Fair Value	78,080	79,833
Less than 12 months, Unrealized Loss	664	911
More than 12 months, Fair Value	5,336	0
More than 12 months, Unrealized Loss	63	0
US Government-sponsored Enterprises Debt Securities [Member]
Investments held in an unrealized loss position
Fair Value	15,907	11,746
Unrealized Loss	127	191
Less than 12 months, Fair Value	15,907	11,746
Less than 12 months, Unrealized Loss	127	191
More than 12 months, Fair Value	0	0
More than 12 months, Unrealized Loss	0	0
State and municipal bonds [Member]
Investments held in an unrealized loss position
Fair Value	111,522	224,884
Unrealized Loss	2,069	6,952
Less than 12 months, Fair Value	103,371	219,276
Less than 12 months, Unrealized Loss	1,441	6,444
More than 12 months, Fair Value	8,151	5,608
More than 12 months, Unrealized Loss	628	508
Corporate debt [Member]
Investments held in an unrealized loss position
Fair Value	372,586	469,632
Unrealized Loss	5,235	8,480
Less than 12 months, Fair Value	336,877	424,721
Less than 12 months, Unrealized Loss	3,167	5,662
More than 12 months, Fair Value	35,709	44,911
More than 12 months, Unrealized Loss	2,068	2,818
Residential mortgage-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	89,610	103,680
Unrealized Loss	1,133	2,046
Less than 12 months, Fair Value	87,491	100,542
Less than 12 months, Unrealized Loss	1,086	1,982
More than 12 months, Fair Value	2,119	3,138
More than 12 months, Unrealized Loss	47	64
Agency commercial mortgage-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	4,568	4,579
Unrealized Loss	62	143
Less than 12 months, Fair Value	4,188	4,192
Less than 12 months, Unrealized Loss	34	114
More than 12 months, Fair Value	380	387
More than 12 months, Unrealized Loss	28	29
Other commercial mortgage-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	9,147	9,822
Unrealized Loss	82	137
Less than 12 months, Fair Value	7,457	9,179
Less than 12 months, Unrealized Loss	65	134
More than 12 months, Fair Value	1,690	643
More than 12 months, Unrealized Loss	17	3
Other asset-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	40,149	44,343
Unrealized Loss	93	267
Less than 12 months, Fair Value	38,264	39,079
Less than 12 months, Unrealized Loss	91	256
More than 12 months, Fair Value	1,885	5,264
More than 12 months, Unrealized Loss	$ 2	$ 11

Investments (Net Investment Inc

Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net Investment Income
Investment fees and expenses	$ (1,882)	$ (1,303)	$ (3,716)	$ (2,946)
Net investment income	22,677	24,583	45,863	50,023
Fixed maturities [Member]
Net Investment Income
Investment Income	18,841	21,208	38,962	43,784
Equities [Member]
Net Investment Income
Investment Income	4,298	3,561	7,942	7,204
Short-term investments and Other invested assets [Member]
Net Investment Income
Investment Income	978	678	1,778	1,082
BOLI [Member]
Net Investment Income
Investment Income	$ 442	$ 439	$ 897	$ 899

Investments (Net Realized Inves

Investments (Net Realized Investment Gains (Losses)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Gain (Loss) on Investments [Line Items]
OTTI losses	$ 0	$ 0	$ (419)	$ (10,734)
Portion of OTTI losses recognized in other comprehensive income before taxes	0	0	248	1,068
Net impairment losses recognized in earnings	0	0	(171)	(9,666)
Gross realized gains, available-for-sale securities	746	1,885	2,599	5,070
Gross realized (losses), available-for-sale securities	(1,401)	(612)	(1,468)	(5,259)
Net realized gains (losses), Short-term investments	0	18	0	18
Net realized gains (losses), trading securities	794	1,913	7,356	3,968
Net realized gains (losses), Other investments	546	447	1,719	498
Change in unrealized holding gains (losses), trading securities	(3,191)	7,115	424	7,851
Change in unrealized holding gains (losses), convertible securities, carried at fair value	285	162	598	95
Other	2	1	4	3
Total net realized investment gains (losses)	(2,219)	10,929	11,061	2,578
Corporate debt [Member]
Gain (Loss) on Investments [Line Items]
OTTI losses	0	0	(419)	(7,604)
Portion of OTTI losses recognized in other comprehensive income before taxes	0	0	248	1,068
Other investments [Member]
Gain (Loss) on Investments [Line Items]
OTTI losses	$ 0	$ 0	$ 0	(3,130)
Net impairment losses recognized in earnings				$ (3,100)

Investments (Credit Losses Reco

Investments (Credit Losses Recorded in Earnings) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other than Temporary Impairment, Credit Losses Recognized in Earnings:
Accumulated credit losses related to impaired debt securities, Beginning Balance	$ 1,329	$ 6,559	$ 1,158	$ 5,751
Additional credit losses recognized during the period, related to securities for which:
No OTTI has been previously recognized	0	0	171	2,398
OTTI has been previously recognized	0	0	0	2,154
Reductions due to:
Securities sold during the period (realized)	(16)	(3,240)	(16)	(6,984)
Accumulated credit losses related to impaired debt securities, Ending Balance	$ 1,313	$ 3,319	$ 1,313	$ 3,319

Investments (Sales and Purchase

Investments (Sales and Purchases of Available-for-Sale Securities) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Information regarding sales and purchases of available-for-sale securities
Proceeds from sales (exclusive of maturities and paydowns)	$ 156,300	$ 82,000	$ 235,500	$ 191,900
Purchases	$ 198,700	$ 173,600	$ 359,080	$ 373,180

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 8.6	$ 8.4
Other Assets [Member]
Income Tax Contingency [Line Items]
Income taxes receivable	$ 4.2
Other Liabilities [Member]
Income Tax Contingency [Line Items]
Income taxes liabilities		$ 5.1

Reserve for Losses and Loss A47

Reserve for Losses and Loss Adjustment Expenses - Narrative and Activity in the Reserve (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017USD ($)partition	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)partition	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) [Abstract]
Minimum period for claims resolution (years)			5 years
Number of business partitions | partition	219		219
Summary of reserve for losses and loss adjustment expenses
Balance, beginning of year			$ 1,993,428	$ 2,005,326	$ 2,005,326
Less reinsurance recoverables on unpaid losses and loss adjustment expenses			273,475	249,350	249,350
Net balance, beginning of year			1,719,953	1,755,976	1,755,976
Net losses:
Current year			292,489	283,329	587,007
Favorable loss development of reserves established in prior years, net	$ (29,012)	$ (36,769)	(57,788)	(65,475)	(143,778)
Total			234,701	217,854	443,229
Paid related to:
Current year			(33,115)	(30,651)	(96,190)
Prior years			(210,006)	(204,193)	(383,062)
Total paid			(243,121)	(234,844)	(479,252)
Net balance, end of year	1,711,533	1,738,986	1,711,533	1,738,986	1,719,953
Plus reinsurance recoverables on unpaid losses and loss adjustment expenses	280,332	253,815	280,332	253,815	273,475
Balance, end of year	$ 1,991,865	$ 1,992,801	$ 1,991,865	$ 1,992,801	$ 1,993,428

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details)	Jun. 30, 2017USD ($)	Jun. 30, 2017GBP (£)	Apr. 30, 2016GBP (£)
Lloyds Syndicate [Member]
Other Commitment, Fiscal Year Maturity [Abstract]
Required FAL Deposit	$ 98,200,000
Current lending capacity under revolving credit agreement | £			£ 20,000,000
Interest rate on revolving credit agreement			3.80%
Unused commitments to extend credit	14,200,000	£ 10,900,000
Non-Public Investment Entities [Member]
Other Commitment, Fiscal Year Maturity [Abstract]
Commitments Total	160,700,000
Commitments due 2017	57,900,000
Commitments due 2018 and 2019	67,600,000
Commitments due 2020 and 2021	32,200,000
Commitments due thereafter	3,000,000
Qualified Affordable Housing Project [Member]
Other Commitment, Fiscal Year Maturity [Abstract]
Commitments due 2017	300,000
Commitments due 2018 and 2019	300,000
Commitments due 2020 and 2021	300,000
Commitments due thereafter	400,000
Qualified affordable housing project investments	1,300,000
Commitment to Provide Capital [Member] | Lloyds Syndicate [Member]
Other Commitment, Fiscal Year Maturity [Abstract]
Commitments Total	200,000,000
Strategic Business Partnership [Member]
Other Commitment, Fiscal Year Maturity [Abstract]
Line of credit amount	9,000,000
Line of credit unused commitment	$ 4,500,000

Debt (Details)

Debt (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Outstanding long-term debt
Debt, gross	$ 428,000,000	$ 450,000,000
Less debt issuance costs	1,626,000	1,798,000
Debt less debt issuance costs	426,374,000	448,202,000
Senior Notes [Member] | Senior notes due 2023 [Member]
Outstanding long-term debt
Debt, gross	$ 250,000,000	$ 250,000,000
Debt stated interest rate	5.30%	5.30%
Line of Credit [Member] | Revolving Credit Facility [Member]
Outstanding long-term debt
Debt, gross	$ 178,000,000	$ 200,000,000
Interest rate on senior notes	1.66%	1.35%
Line of credit maximum borrowing capacity	$ 250,000,000	$ 250,000,000

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended				6 Months Ended		12 Months Ended
	Feb. 28, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2014	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized common stock (in shares)		100,000,000				100,000,000			100,000,000
Authorized preferred stock (in shares)		50,000,000				50,000,000			50,000,000
Quarterly dividend declared, per share (USD per share)		$ 0.310	$ 0.31	$ 0.31	$ 0.31	$ 0.62	$ 0.62
Dividend declared						$ 33,000	$ 32,900
Total authorizations which remain available for use		$ 109,600				$ 109,600
Common shares acquired (in shares)						0	44,500
Cost of common shares reacquired						$ 0	$ 2,106
Bonus compensation shares issued (in shares)	9,000
Gain (loss) related to unrecognized changes in defined benefit plan liabilities							$ 500
Non-credit loss, net of tax		$ 500				$ 500			$ 300
Statutory income tax rate		35.00%		35.00%		35.00%	35.00%
Restricted Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards in period (in shares)	84,600
Fair value of each unit awarded (USD per share)	$ 58.35
Award vesting period	3 years
Shares issued in period for share-based compensation (in shares)	29,300
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards in period (in shares)	48,000
Shares issued in period for share-based compensation (in shares)	99,500
Performance Shares [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award payout rate	50.00%
Performance Shares [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award payout rate	200.00%
Performance Shares Granted in 2014 [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award payout rate								117.00%
Performance Shares Granted in 2014 [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award payout rate								125.00%

Shareholders' Equity (Share-bas

Shareholders' Equity (Share-based Compensation Expense and Related Tax Benefits) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
Share-based compensation expense	$ 2,746	$ 3,098	$ 6,092	$ 5,813
Related tax benefits	$ 961	$ 1,084	$ 2,132	$ 2,035

Shareholders' Equity (AOCI Recl

Shareholders' Equity (AOCI Reclassification) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassifications from AOCI to Net income:
Deferred tax expense (benefit) included in OCI	$ 2,983	$ 7,541	$ 4,464	$ 19,801
Tax rate used to compute the tax effect of amounts reclassified out of OCI	35.00%	35.00%	35.00%	35.00%
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassifications from AOCI to Net income:
Reclassification amount, before tax effect	$ (656)	$ 1,271	$ 960	$ (6,722)
Tax effect (at 35%)	230	(445)	(336)	2,353
Net reclassification adjustments	(426)	826	624	(4,369)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Realized investment gains (losses) [Member]
Reclassifications from AOCI to Net income:
Reclassification amount, before tax effect	(653)	2,024	963	(4,443)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Non-credit impairment losses reclassified to earnings, due to sale of securities or reclassification as a credit loss [Member]
Reclassifications from AOCI to Net income:
Reclassification amount, before tax effect	$ (3)	$ (753)	$ (3)	$ (2,279)

Variable Interest Entities (Det

Variable Interest Entities (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Other investments [Member]
Variable Interest Entity [Line Items]
VIE interests carrying value	$ 27	$ 26.9
Investment in unconsolidated subsidiaries [Member]
Variable Interest Entity [Line Items]
VIE interests carrying value	$ 270.5	$ 282.3

Segment Information (Narrative)

Segment Information (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)segment	Jun. 30, 2016USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			4
Segregated portfolio cells dividend expense (income)	$ 8,811	$ 1,523	$ 11,186	$ 2,699
Income tax benefit (expense)	332	(5,413)	1,557	(6,777)
Premiums ceded under quota share agreement	$ 3,100	3,400	$ 6,600	7,000
Workers Compensation [Member]
Segment Reporting Information [Line Items]
Worker's compensation SPC percentage ceded	100.00%		100.00%
Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Proportion of Capital Provided to support Lloyd's Syndicate 1729	58.00%		58.00%
Operating Segments [Member] | Workers Compensation [Member]
Segment Reporting Information [Line Items]
Segregated portfolio cells dividend expense (income)	$ 2,698	1,277	$ 3,872	1,990
Operating Segments [Member] | Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Income tax benefit (expense)	548	(812)	555	(897)
Operating Segments [Member] | Specialty Property and Casualty [Member]
Segment Reporting Information [Line Items]
Segregated portfolio cells dividend expense (income)	5,119		5,091
Operating Segments [Member] | Specialty Property and Casualty [Member] | Previously Unrecognized Segregated Portfolilo Cells (SPC) Dividend Expense [Member]
Segment Reporting Information [Line Items]
Segregated portfolio cells dividend expense (income)	5,200
Operating Segments [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Segregated portfolio cells dividend expense (income)	994	246	2,223	709
Income tax benefit (expense)	(216)	$ (4,601)	$ 1,002	$ (5,880)
Operating Segments [Member] | Corporate [Member] | Previously Unrecognized Segregated Portfolilo Cells (SPC) Dividend Expense [Member]
Segment Reporting Information [Line Items]
Income tax benefit (expense)	$ 1,800

Segment Information (Financial

Segment Information (Financial Data by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Net premiums earned	$ 180,353	$ 176,732	$ 363,256	$ 354,312
Net investment income	22,677	24,583	45,863	50,023
Equity in earnings (loss) of unconsolidated subsidiaries	2,516	376	4,324	(3,259)
Net realized gains (losses)	(2,219)	10,929	11,061	2,578
Other income	2,250	2,181	4,071	4,535
Net losses and loss adjustment expenses	(115,550)	(106,899)	(234,701)	(217,854)
Underwriting, policy acquisition and operating expenses	(57,885)	(54,034)	(114,994)	(110,923)
Segregated portfolio cells dividend (expense) income	(8,811)	(1,523)	(11,186)	(2,699)
Interest expense	(4,145)	(3,851)	(8,278)	(7,537)
Income tax benefit (expense)	332	(5,413)	1,557	(6,777)
Net income	19,518	43,081	60,973	62,399
Depreciation and amortization, net of accretion	6,146	8,343	13,949	16,971
Operating Segments [Member] | Specialty P&C [Member]
Segment Reporting Information [Line Items]
Net premiums earned	109,005	108,126	222,063	218,882
Other income	1,469	1,732	2,668	3,008
Net losses and loss adjustment expenses	(71,296)	(62,301)	(146,291)	(133,477)
Underwriting, policy acquisition and operating expenses	(26,239)	(25,902)	(52,217)	(50,954)
Segregated portfolio cells dividend (expense) income	(5,119)		(5,091)
Net income	7,820	21,655	21,132	37,459
Depreciation and amortization, net of accretion	1,506	1,486	3,417	3,497
Operating Segments [Member] | Workers Compensation [Member]
Segment Reporting Information [Line Items]
Net premiums earned	56,854	55,093	112,137	109,476
Other income	209	139	354	610
Net losses and loss adjustment expenses	(33,486)	(34,661)	(68,136)	(69,687)
Underwriting, policy acquisition and operating expenses	(17,093)	(16,334)	(33,784)	(34,165)
Segregated portfolio cells dividend (expense) income	(2,698)	(1,277)	(3,872)	(1,990)
Net income	3,786	2,960	6,699	4,244
Depreciation and amortization, net of accretion	831	1,393	1,668	2,797
Operating Segments [Member] | Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Net premiums earned	14,494	13,513	29,056	25,954
Net investment income	410	337	782	653
Net realized gains (losses)	47	14	74	8
Other income	(151)	188	240	440
Net losses and loss adjustment expenses	(10,768)	(8,502)	(20,274)	(14,690)
Underwriting, policy acquisition and operating expenses	(6,851)	(5,240)	(13,062)	(10,406)
Income tax benefit (expense)	548	(812)	555	(897)
Net income	(2,271)	(502)	(2,629)	1,062
Depreciation and amortization, net of accretion	(5)	43	(8)	109
Operating Segments [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Net investment income	22,267	24,246	45,081	49,370
Equity in earnings (loss) of unconsolidated subsidiaries	2,516	376	4,324	(3,259)
Net realized gains (losses)	(2,266)	10,915	10,987	2,570
Other income	778	286	951	744
Underwriting, policy acquisition and operating expenses	(7,757)	(8,157)	(16,073)	(15,665)
Segregated portfolio cells dividend (expense) income	(994)	(246)	(2,223)	(709)
Interest expense	(4,145)	(3,851)	(8,278)	(7,537)
Income tax benefit (expense)	(216)	(4,601)	1,002	(5,880)
Net income	10,183	18,968	35,771	19,634
Depreciation and amortization, net of accretion	3,814	5,421	8,872	10,568
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net premiums earned	0	0	0	0
Other income	(55)	(164)	(142)	(267)
Net losses and loss adjustment expenses	0	(1,435)	0	0
Underwriting, policy acquisition and operating expenses	55	1,599	142	267
Net income	0	0	0	0
Depreciation and amortization, net of accretion	$ 0	$ 0	$ 0	$ 0

Segment Information (Gross Prem

Segment Information (Gross Premiums Earned by Product and Reconciliation to Net Premiums) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Net premiums earned	$ 180,353	$ 176,732	$ 363,256	$ 354,312
Operating Segments [Member] | Specialty P&C [Member]
Segment Reporting Information [Line Items]
Ceded premiums earned	(21,683)	(18,702)	(40,407)	(37,127)
Net premiums earned	109,005	108,126	222,063	218,882
Operating Segments [Member] | Specialty P&C [Member] | Healthcare professional liability [Member]
Segment Reporting Information [Line Items]
Gross premiums earned	115,781	111,938	232,832	225,687
Operating Segments [Member] | Specialty P&C [Member] | Legal professional liability [Member]
Segment Reporting Information [Line Items]
Gross premiums earned	6,417	6,493	12,734	13,107
Operating Segments [Member] | Specialty P&C [Member] | Medical technology and life sciences product liability [Member]
Segment Reporting Information [Line Items]
Gross premiums earned	8,389	8,243	16,701	16,794
Operating Segments [Member] | Specialty P&C [Member] | Other [Member]
Segment Reporting Information [Line Items]
Gross premiums earned	101	154	203	421
Operating Segments [Member] | Workers Compensation [Member]
Segment Reporting Information [Line Items]
Ceded premiums earned	(5,856)	(5,905)	(11,787)	(12,467)
Net premiums earned	56,854	55,093	112,137	109,476
Operating Segments [Member] | Workers Compensation [Member] | Traditional business [Member]
Segment Reporting Information [Line Items]
Gross premiums earned	42,501	42,193	84,269	84,844
Operating Segments [Member] | Workers Compensation [Member] | Alternative market business [Member]
Segment Reporting Information [Line Items]
Gross premiums earned	20,209	18,805	39,655	37,099
Operating Segments [Member] | Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Ceded premiums earned	(2,466)	(346)	(5,089)	(1,277)
Net premiums earned	14,494	13,513	29,056	25,954
Operating Segments [Member] | Lloyds Syndicate [Member] | Property, Liability and Casualty Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Gross premiums earned	$ 16,960	$ 13,859	$ 34,145	$ 27,231

Subsequent Events (Details)

Subsequent Events (Details) $ in Millions	1 Months Ended
	Jul. 31, 2017USD ($)
Subsequent Event [Member] | Line of Credit [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Amount of debt repaid	$ 17