ProAssurance (PRA) 10-K 24 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 20, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	PROASSURANCE CORP
Entity Central Index Key	1127703
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		55,814,475
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$2,557,238,513

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Investments
Fixed maturities, available for sale, at fair value; amortized cost, $3,055,477 and $3,026,256, respectively	$3,145,027	$3,118,049
Equity securities, trading, at fair value; cost, $283,107 and $203,308, respectively	314,482	253,541
Short-term investments	131,259	248,605
Business owned life insurance	56,381	54,374
Investment in unconsolidated subsidiaries	276,501	214,236
Other investments, $28,958 at fair value at December 31, 2014, otherwise at cost or amortized cost	86,057	52,240
Total Investments	4,009,707	3,941,045
Cash and cash equivalents	197,040	129,383
Restricted cash	0	78,000
Premiums receivable	202,528	115,403
Receivable from reinsurers on paid losses and loss adjustment expenses	6,494	3,231
Receivable from reinsurers on unpaid losses and loss adjustment expenses	237,966	247,518
Prepaid reinsurance premiums	32,115	21,449
Deferred policy acquisition costs	38,790	28,207
Deferred tax asset	0	1,757
Real estate, net	39,799	41,010
Intangible assets	100,733	52,002
Goodwill	210,725	161,115
Other assets	93,263	329,979
Total Assets	5,169,160	5,150,099
Policy liabilities and accruals
Reserve for losses and loss adjustment expenses	2,058,266	2,072,822
Unearned premiums	345,828	255,463
Reinsurance premiums payable	17,451	34,321
Total Policy Liabilities	2,421,545	2,362,606
Deferred tax liability	18,818	0
Other liabilities	320,853	143,079
Long-term debt	250,000	250,000
Total Liabilities	3,011,216	2,755,685
Shareholders’ Equity:
Common shares, par value $0.01 per share, 100,000,000 shares authorized, 62,297,214 and 62,096,787 shares issued, respectively	623	621
Additional paid-in capital	359,577	349,894
Accumulated other comprehensive income (loss), net of deferred tax expense (benefit) of $31,342 and $32,127, respectively	58,204	59,661
Retained earnings	1,991,704	2,015,603
Treasury shares, at cost, 5,763,388 shares and 900,281 shares, respectively	-252,164	-31,365
Total Shareholders’ Equity	2,157,944	2,394,414
Total Liabilities and Shareholders’ Equity	$5,169,160	$5,150,099

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, at fair value; amortized cost	$3,055,477	$3,026,256
Equity securities, trading, cost	283,107	203,308
Other investments, portion carried at fair value	28,958	0
Common shares, par value (USD per share)	$0.01	$0.01
Common shares, shares authorized	100,000,000	100,000,000
Common shares, shares issued	62,297,214	62,096,787
Deferred tax expense (benefit) on accumulated other comprehensive income (loss)	$31,342	$32,127
Treasury shares, number of shares	5,763,388	900,281

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Capital (USD $)	3 Months Ended				12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase (Decrease) in Stockholders' Equity:
Beginning Balance		$2,394,414		$2,270,580	$2,394,414	$2,270,580	$2,164,453
Common shares reacquired					-222,360	-32,454
Common shares issued for compensation					4,200	4,085	3,594
Share-based compensation					10,056	9,242	8,639
Net effect of restricted and performance shares issued and stock options exercised					-3,010	-4,066	-4,453
Dividends to shareholders					-220,464	-64,777	-192,466
Two-for-one stock split effected in the form of a stock dividend							0
Other comprehensive income (loss)					-1,457	-85,719	15,343
Net income	65,114	46,731	70,864	112,850	196,565	297,523	275,470
Ending Balance	2,157,944		2,394,414		2,157,944	2,394,414	2,270,580
Common Stock
Increase (Decrease) in Stockholders' Equity:
Beginning Balance		621		619	621	619	346
Common shares reacquired					0	0
Common shares issued for compensation					0	0	0
Share-based compensation					0	0	0
Net effect of restricted and performance shares issued and stock options exercised					2	2	2
Dividends to shareholders					0	0	0
Two-for-one stock split effected in the form of a stock dividend							271
Other comprehensive income (loss)					0	0	0
Net income					0	0	0
Ending Balance	623		621		623	621	619
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity:
Beginning Balance		349,894		341,780	349,894	341,780	538,625
Common shares reacquired					0	0
Common shares issued for compensation					2,639	2,940	3,041
Share-based compensation					10,056	9,242	8,639
Net effect of restricted and performance shares issued and stock options exercised					-3,012	-4,068	-4,455
Dividends to shareholders					0	0	0
Two-for-one stock split effected in the form of a stock dividend							-204,070
Other comprehensive income (loss)					0	0	0
Net income					0	0	0
Ending Balance	359,577		349,894		359,577	349,894	341,780
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity:
Beginning Balance		59,661		145,380	59,661	145,380	130,037
Common shares reacquired					0	0
Common shares issued for compensation						0	0
Share-based compensation					0	0	0
Net effect of restricted and performance shares issued and stock options exercised					0	0	0
Dividends to shareholders					0	0	0
Two-for-one stock split effected in the form of a stock dividend							0
Other comprehensive income (loss)					-1,457	-85,719	15,343
Net income					0	0	0
Ending Balance	58,204		59,661		58,204	59,661	145,380
Retained Earnings
Increase (Decrease) in Stockholders' Equity:
Beginning Balance		2,015,603		1,782,857	2,015,603	1,782,857	1,699,853
Common shares reacquired					0	0
Common shares issued for compensation					0	0	0
Share-based compensation					0	0	0
Net effect of restricted and performance shares issued and stock options exercised					0	0	0
Dividends to shareholders					-220,464	-64,777	-192,466
Other comprehensive income (loss)					0	0	0
Net income					196,565	297,523	275,470
Ending Balance	1,991,704		2,015,603		1,991,704	2,015,603	1,782,857
Treasury Stock
Increase (Decrease) in Stockholders' Equity:
Beginning Balance		-31,365		-56	-31,365	-56	-204,408
Common shares reacquired					-222,360	-32,454
Common shares issued for compensation					1,561	1,145	553
Share-based compensation					0	0	0
Net effect of restricted and performance shares issued and stock options exercised					0	0	0
Dividends to shareholders					0	0	0
Two-for-one stock split effected in the form of a stock dividend							203,799
Other comprehensive income (loss)					0	0	0
Net income					0	0	0
Ending Balance	($252,164)		($31,365)		($252,164)	($31,365)	($56)

Consolidated_Statements_of_Inc

Consolidated Statements of Income and Comprehensive Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Net premiums earned	$699,731	$527,919	$550,664
Net investment income	125,557	129,265	136,094
Equity in earnings (loss) of unconsolidated subsidiaries	3,986	7,539	-6,873
Net realized investment gains (losses):
Other-than-temporary impairment (OTTI) losses	-1,475	-71	-1,566
Portion of OTTI losses recognized in (reclassified from) other comprehensive income before taxes	268	0	-201
Net impairment losses recognized in earnings	-1,207	-71	-1,767
Other net realized investment gains (losses)	15,861	67,975	30,630
Total net realized investment gains (losses)	14,654	67,904	28,863
Other income	8,398	7,551	7,106
Total revenues	852,326	740,178	715,854
Expenses
Losses and loss adjustment expenses	379,232	243,015	161,726
Reinsurance recoveries	-16,148	-18,254	18,187
Net losses and loss adjustment expenses	363,084	224,761	179,913
Underwriting, policy acquisition and operating expenses	211,311	147,817	135,631
Segregated portfolio cells dividend expense	1,842	0	0
Interest expense	14,084	2,755	2,181
Loss on extinguishment of debt	0	0	2,163
Total expenses	590,321	375,333	319,888
Gain on acquisition	0	32,314	0
Income before income taxes	262,005	397,159	395,966
Provision for income taxes
Current expense (benefit)	58,645	74,977	82,752
Deferred expense (benefit)	6,795	24,659	37,744
Total income tax expense (benefit)	65,440	99,636	120,496
Net income	196,565	297,523	275,470
Other comprehensive income (loss), after tax, net of reclassification adjustments	-1,457	-85,719	15,343
Comprehensive income	$195,108	$211,804	$290,813
Earnings per share:
Basic (USD per share)	$3.32	$4.82	$4.49
Diluted (USD per share)	$3.30	$4.80	$4.46
Weighted average number of common shares outstanding:
Basic (in shares)	59,285	61,761	61,342
Diluted (in shares)	59,525	62,020	61,833
Cash dividends declared per common share (USD per share)	$3.86	$1.05	$3.13

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities
Net income	$196,565	$297,523	$275,470
Adjustments to reconcile income to net cash provided by operating activities:
Amortization, net of accretion	43,367	41,429	32,832
Depreciation	6,956	4,538	4,741
Loss (gain) on extinguishment of debt	0	0	2,163
Gain on acquisition	0	-32,314	0
(Increase) decrease in cash surrender value of business owned life insurance	-2,007	-1,960	-2,008
Net realized investment gains	-14,654	-67,904	-28,863
Share-based compensation	10,056	9,242	8,639
Deferred income taxes	6,795	24,659	37,744
Policy acquisition costs, net amortization (net deferral)	10	-5,820	3,448
Equity in earnings of unconsolidated subsidiaries, excluding distributions received and tax credit partnership amortization	-10,700	-17,376	450
Other	-8,784	-3,014	-2,957
Other changes in assets and liabilities, excluding effect of business combinations:
Premiums receivable	-15,136	-6,105	16,494
Receivable from reinsurers on paid losses and loss adjustment expenses	3,263	2,601	-342
Receivable from reinsurers on unpaid losses and loss adjustment expenses	27,114	15,625	58,870
Prepaid reinsurance premiums	-5,672	-849	-482
Other assets	36,924	9,582	-11,231
Reserve for losses and loss adjustment expenses	-167,747	-179,677	-218,100
Unearned premiums	10,097	-1,740	-21,919
Reinsurance premiums payable	-26,377	-13,269	-36,583
Other liabilities	5,932	-36,569	-27,116
Net cash provided (used) by operating activities	96,002	38,602	91,250
Purchases of:
Fixed maturities, available for sale	-645,114	-519,161	-646,198
Equity securities, trading	-119,865	-87,604	-120,555
Other investments	-25,109	-34,699	-9,977
Funding of tax credit limited partnerships	-8,611	-63,489	-35,745
Investment in unconsolidated subsidiaries	-52,295	-19,228	-11,009
Proceeds from sales or maturities of:
Fixed maturities, available for sale	703,828	970,708	926,221
Equity securities, trading	134,005	123,645	54,670
Other investments	19,942	2,352	1,180
Distributions from unconsolidated subsidiaries	5,428	14,632	1,387
Net sales or maturities (purchases) of short-term investments	140,411	-176,092	48,565
Cash received in (paid in) acquisition	35,013	22,780	-28,439
Deposit made for future acquisition	0	-205,244	-153,700
Unsettled security transactions, net change	-2,953	205	4,852
Funds at Lloyd's in support of Syndicate 1729, returned (deposited)	8,690	-8,699	0
(Increase) decrease in restricted cash	78,000	-78,000	0
Other	-4,390	-9,909	-4,409
Net cash provided (used) by investing activities	266,980	-67,803	26,843
Financing Activities
Proceeds from long-term debt	0	250,000	125,000
Repayment of long-term debt	0	-127,183	-57,660
Repurchase of common stock	-222,360	-29,089	0
Excess tax benefit from share-based payment arrangements	2,702	2,128	7,022
Dividends to shareholders	-71,252	-46,375	-200,118
Other	-4,415	-9,448	-4,186
Net cash provided (used) by financing activities	-295,325	40,033	-129,942
Increase (decrease) in cash and cash equivalents	67,657	10,832	-11,849
Cash and cash equivalents at beginning of period	129,383	118,551	130,400
Cash and cash equivalents at end of period	197,040	129,383	118,551
Supplemental Disclosure of Cash Flow Information
Cash paid during the year for income taxes, net of refunds	26,061	117,107	110,278
Cash paid during the year for interest	13,408	913	2,342
Significant non-cash transactions
Deposit transferred as consideration for acquisition	205,244	153,700	0
Unpaid dividends	167,744	18,532	0
Other investment interest converted to equity securities	$0	$0	$15,742

Accounting_Policies

Accounting Policies

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Accounting Policies

Accounting Policies

Organization and Nature of Business

ProAssurance Corporation (ProAssurance, PRA or the Company), a Delaware corporation, is an insurance holding company primarily for wholly owned specialty property and casualty insurance entities including an entity that is the majority capital provider to Syndicate 1729 at Lloyd's of London. Risks insured are primarily liability risks located within the United States of America (U.S.). As described in more detail in Note 15, ProAssurance operates in four reportable segments: Specialty Property and Casualty (Specialty P&C), Workers' Compensation, Lloyd's Syndicate, and Corporate.

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of ProAssurance Corporation and its wholly-owned subsidiaries. Investments in entities where ProAssurance holds a greater than minor interest but does not hold a controlling interest are accounted for using the equity method. All significant intercompany accounts and transactions are eliminated in consolidation. ProAssurance subsidiaries located in the United Kingdom (U.K.) are reported on a quarter delay due to timing issues regarding the availability of information, except there is no delay related to subsidiary investments managed in the U.S. as that information is available on an earlier schedule.

Basis of Presentation

The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenues and expenses, and disclosures related to these amounts at the date of the financial statements. Actual results could differ from those estimates.

Reclassifications

On January 1, 2014, ProAssurance began reporting unearned ceding commissions as an offset to deferred policy acquisition costs (DPAC) on the Consolidated Balance Sheet, and the December 31, 2013 Consolidated Balance Sheet has been conformed to the current presentation. Previously, unearned ceding commissions ($0.8 million at December 31, 2013) were reported in Unearned premiums. Also, ceding commission income earned for the years ended December 31, 2014, 2013 and 2012 has been reported as an offset to DPAC amortization (see Note 7) which lowered DPAC amortization as previously reported for the years ended December 31, 2013 and 2012 by $5.9 million and $2.1 million, respectively. Total underwriting, policy acquisition and operating expense for the years ended December 31, 2013 and 2012 was not affected by the change in presentation.

Stock Split

In 2012, the Board of Directors of ProAssurance Corporation (the Board) declared a two-for-one split of ProAssurance common shares which was effected December 27, 2012 in the form of a stock dividend. All share and per share information provided in this report reflects the effect of the split for all periods presented.

Accounting Policies

The significant accounting policies followed by ProAssurance in making estimates that materially affect financial reporting are summarized in these notes to the consolidated financial statements.

Recognition of Revenues

Insurance premiums are recognized as revenues pro rata over the terms of the policies, which are principally one year in duration.

At December 31, 2014 and 2013 ProAssurance had established allowances for credit losses related to premium and agency receivables as shown in the following table.

(in thousands)

Premium

Agency

Receivables

Receivables

Allowance for credit losses:

Balance at December 31, 2012

$

1,000

$

286

Estimated credit losses

236

—

Account write offs, net of recoveries

(246

)

(236

)

Balance at December 31, 2013

990

50

Estimated credit losses

299

—

Account write offs, net of recoveries

(299

)

—

Allowance acquired from acquisition

225

—

Balance at December 31, 2014

$

1,215

$

50

Earned But Unbilled Premiums (EBUB)

Workers’ compensation premiums are determined based upon the payroll of the insured, the applicable premium rates and, where applicable, an experience based modification factor. An audit of the policyholders’ records is conducted after policy expiration to make a final determination of applicable premiums. Audit premium due from or due to a policyholder as a result of an audit is reflected in net premiums earned when billed. ProAssurance tracks, by policy, the amount of additional premium billed in final audit invoices as a percentage of payroll exposure and uses this information to estimate the probable additional amount that it has earned, but not yet billed, as of the balance sheet date. Changes to the EBUB estimate are included in Net premiums earned in the period recognized. As of December 31, 2014, ProAssurance carried earned but unbilled premiums of $3.4 million as a part of Premiums receivable.

Losses and Loss Adjustment Expenses

ProAssurance establishes its reserve for losses and loss adjustment expenses ("reserve for losses" or "reserve") based on estimates of the future amounts necessary to pay claims and expenses associated with the investigation and settlement of claims. The reserve for losses is determined on the basis of individual claims and payments thereon as well as actuarially determined estimates of future losses based on past loss experience, available industry data and projections as to future claims frequency, severity, inflationary trends, judicial trends, legislative changes and settlement patterns.

Management establishes the reserve for losses after taking into consideration a variety of factors including the conclusions reached by internal actuaries, premium rates, claims frequency, historical paid and incurred loss development trends, the effect of inflation, general economic trends, the legal and political environment, and the reports received from consulting actuaries. Internal actuaries perform an in-depth review of the reserve for losses at least semi-annually using the loss and exposure data of ProAssurance subsidiaries. Management engages consulting actuaries to review subsidiary loss and exposure data and provide reports to Management regarding the adequacy of reserves.

Estimating casualty insurance reserves, and particularly long-tailed insurance reserves, is a complex process. Long-tailed insurance is characterized by the extended period of time between collecting the premium for insuring a risk and the ultimate payment of losses. For a high proportion of the risks insured or reinsured by ProAssurance the period of time required to resolve a claim is often five years or more, and claims may be subject to litigation. Estimating losses for these long-tailed claims requires ProAssurance to make and revise judgments and assessments regarding multiple uncertainties over an extended period of time. As a result, reserve estimates may vary significantly from the eventual outcome. Reserve estimates and the assumptions on which these estimates are predicated are regularly reviewed and updated as new information becomes available. Any adjustments necessary are reflected in then current operations. Due to the size of ProAssurance’s reserve for losses, even a small percentage adjustment to these estimates could have a material effect on earnings in the period in which the adjustment is made, as was the case in 2014, 2013 and 2012.

The effect of adjustments made to reinsured losses is mitigated by the corresponding adjustment that is made to reinsurance recoveries. Thus, in any given year, ProAssurance may make significant adjustments to gross losses that have little effect on its net losses.

Reinsurance Receivables

ProAssurance enters into reinsurance agreements whereby other insurance entities agree to assume a portion of the risk associated with certain policies issued by ProAssurance. In return, ProAssurance agrees to pay a premium to the reinsurer. ProAssurance purchases reinsurance to provide for greater diversification of business and to allow management to control exposure to potential losses arising from large risks.

Receivable from reinsurers on paid losses and loss adjustment expenses is the estimated amount of losses already paid that will be recoverable from reinsurers. Receivable from reinsurers on unpaid losses and loss adjustment expenses is the estimated amount of future loss payments that will be recoverable from reinsurers. Reinsurance recoveries are the portion of losses incurred during the period that are estimated to be allocable to reinsurers. Premiums ceded are the estimated premiums that will be due to reinsurers with respect to premiums earned and losses incurred during the period.

These estimates are based upon management’s estimates of ultimate losses and the portion of those losses that are allocable to reinsurers under the terms of the related reinsurance agreements. Given the uncertainty of the ultimate amounts of losses, these estimates may vary significantly from the eventual outcome. Management regularly reviews these estimates and any adjustments necessary are reflected in the period in which the estimate is changed. Due to the size of the receivable from reinsurers, even a small adjustment to the estimates could have a material effect on ProAssurance’s results of operations for the period in which the change is made.

Reinsurance contracts do not relieve ProAssurance from its obligations to policyholders. ProAssurance continually monitors its reinsurers to minimize its exposure to significant losses from reinsurer insolvencies. Any amount determined to be uncollectible is written off in the period in which the uncollectible amount is identified.

Investments

Fair Values

Fair values of investment securities are primarily provided by independent pricing services. The pricing services provide an exchange traded price, if available, or provide an estimated price determined using multiple observable inputs, including exchange traded prices for similar assets. Management reviews valuations of securities obtained from the pricing services for accuracy based upon the specifics of the security, including class, maturity, credit rating, durations, collateral, and comparable markets for similar securities. Multiple observable inputs are not available for certain of our investments, including municipal bonds and corporate debt not actively traded, and investments in limited partnerships/limited liability companies (LPs/LLCs). Management values these municipal bonds and corporate debt either using a single non-binding broker quote or pricing models that utilize market based assumptions that have limited observable inputs. Management values certain investments in LPs/LLCs based on the net asset value (NAV) of the interest held, as provided by the fund.

Fixed Maturities and Equity Securities

Fixed maturities and equity securities are considered as either available-for-sale or trading securities.

Available-for-sale securities are carried at fair value, determined as described above, and unrealized gains and losses on such available-for-sale securities are included, net of related tax effects, in Shareholders’ Equity as a component of Accumulated Other Comprehensive Income (Loss).

Investment income includes amortization of premium and accretion of discount related to available-for-sale debt securities acquired at other than par value. Debt securities and mandatorily redeemable preferred stock with maturities beyond one year when purchased are classified as fixed maturities.

Trading portfolio securities are carried at fair value, determined as described above, with the holding gains and losses included in realized investment gains and losses in the current period.

Short-term Investments

Short-term investments, which have a maturity at purchase of one year or less, are primarily comprised of investments in U.S. Treasury obligations and commercial paper. All balances are reported at amortized cost, which approximates fair value.

Other Investments

Investments in LPs/LLCs where ProAssurance has virtually no influence over the operating and financial policies of an investee are accounted for using the cost method. Under the cost method, investments are valued at cost, with investment income recognized when received.

Investments in convertible bond 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. Interest on convertible bond securities is recorded on an accrual basis based on contractual interest rates and is included in Net investment income.

Investment in Unconsolidated Subsidiaries

Investments in LPs/LLCs where ProAssurance is deemed to have influence because it holds a greater than a minor interest are accounted for using the equity method. Under the equity method, the recorded basis of the investment is adjusted each period for the investor’s pro rata share of the investee’s income or loss. Investments in unconsolidated subsidiaries include tax credit partnerships accounted for using the equity method, whereby ProAssurance’s proportionate share of income or loss is included in investment income. Tax credits received from the partnerships are recognized in the period received as a reduction to current tax expenses.

Business Owned Life Insurance (BOLI)

ProAssurance owns life insurance contracts on certain management employees. The life insurance contracts are carried at their current cash surrender value. Changes in the cash surrender value are included in income in the current period as investment income. Death proceeds from the contracts are recorded when the proceeds become payable under the policy terms.

Realized Gains and Losses

Realized investment gains and losses are recognized on the specific identification basis.

Other-than-temporary Impairments

ProAssurance evaluates its available-for-sale investment securities on at least a quarterly basis for the purpose of determining whether declines in fair value below recorded cost basis represent other-than-temporary declines. The assessment of whether the amortized cost basis of debt securities, particularly asset-backed debt securities, is expected to be recovered requires management to make assumptions regarding various matters affecting cash flows to be received in the future. The choice of assumptions is subjective and requires the use of judgment; actual credit losses experienced in future periods may differ from management’s estimates of those credit losses.

If there is intent to sell the security or if it is more likely than not that the security will be required to be sold before full recovery of its amortized cost basis, ProAssurance considers a decline in fair value to be an other-than-temporary impairment. Otherwise, ProAssurance considers the following factors in determining whether an investment’s decline is other-than-temporary:

For equity securities:

•

the length of time for which the fair value of the investment has been less than its recorded basis;

•

the financial condition and near-term prospects of the issuer underlying the investment, taking into consideration the economic prospects of the issuer’s industry and geographical region, to the extent that information is publicly available; and

•

the historical and implied volatility of the fair value of the security.

For debt securities, an evaluation is made as to whether the decline in fair value is due to credit loss, which is defined as the excess of the current amortized cost basis of the security over the present value of expected future cash flows. Methodologies used to estimate the present value of expected cash flows to determine if a decline is due to a credit loss are:

•

For non-structured fixed maturities (U.S. Treasury securities, obligations of U.S. Government and government agencies and authorities, obligations of states, municipalities and political subdivisions, and corporate debt) the estimate of expected cash flows is determined by projecting a recovery value and a recovery time frame and assessing whether further principal and interest will be received. ProAssurance considers various factors in projecting recovery values and recovery time frames, including the following:

•

third party research and credit rating reports;

•

the current credit standing of the issuer, including credit rating downgrades, whether before or after the balance sheet date;

•

internal assessments and the assessments of external portfolio managers regarding specific circumstances surrounding an investment, which indicate the investment is more or less likely to recover its amortized cost than other investments with a similar structure;

•

failure of the issuer of the security to make scheduled interest or principal payments;

•

For structured securities (primarily asset-backed securities), ProAssurance estimates the present value of the security’s cash flows using the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment or changes in expected cash flows). ProAssurance considers the most recently available six month averages of the levels of delinquencies, defaults, severities, and prepayments for the collateral (loans) underlying the securitization or, if historical data is not available, sector based assumptions, to estimate expected future cash flows of these securities.

Investments in tax credit partnerships are evaluated for OTTI by considering both qualitative and quantitative factors which include: whether cash flows currently expected from the investment, primarily tax benefits, equal or exceed the carrying value of the investment, whether currently expected cash flows are less than those expected at the time the investment was acquired, and ProAssurance's ability and intent to hold the investment until the recovery of its carrying value.

Investments in LPs/LLCs other than tax credit partnerships are evaluated for impairment by comparing ProAssurance’s carrying value to net asset value of ProAssurance’s interest as reported by the LP/LLC. Additionally, Management considers the performance of the LP/LLC relative to the market and its stated objectives, cash flows expected from the interest, and the audited financial statements of the LP/LLC, if available.

ProAssurance recognizes other-than-temporary impairments, including impairments of debt securities due to credit loss, in earnings as a part of net realized investment gains (losses). In subsequent periods, any measurement of gain or loss or impairment is based on the revised amortized basis of the security. Declines in fair value, including non-credit impairments of debt securities, not considered to be other-than-temporary are recognized in other comprehensive income.

Asset-backed securities that have been impaired due to credit or are below investment grade quality are accounted for under the effective yield method. Under the effective yield method estimates of cash flows expected over the life of asset-backed securities are then used to recognize income on the investment balance for subsequent accounting periods.

Foreign Currency

The functional currency of all ProAssurance foreign subsidiaries is the U.S. Dollar.

Cash and Cash Equivalents

For purposes of the consolidated balance sheets and statements of cash flows, ProAssurance considers all demand deposits and overnight investments to be cash equivalents.

Restricted Cash

Restricted cash represents cash balances which are not available for immediate or general use. At December 31, 2013 ProAssurance's Restricted cash was comprised entirely of a deposit collateralizing a standby letter of credit entered into as partial funding at Lloyd's for Syndicate 1729.

Deferred Policy Acquisition Costs; Ceding Commission Income

Costs that vary with and are directly related to the successful production of new and renewal premiums (primarily premium taxes, commissions and underwriting salaries) are deferred to the extent they are recoverable against unearned premiums and are amortized as related premiums are earned. Unearned ceding commission income is reported as an offset to deferred policy acquisition costs. Ceding commission earned is reported as an offset to DPAC amortization.

Income Taxes/Deferred Taxes

ProAssurance files a consolidated federal income tax return. Tax-related interest and penalties are recognized as components of tax expense.

ProAssurance evaluates tax positions taken on tax returns and recognizes positions in the financial statements when it is more likely than not that the position will be sustained upon resolution with a taxing authority. If recognized, the benefit is measured as the largest amount of benefit that has a greater than fifty percent probability of being realized. Uncertain tax positions are reviewed each period by considering changes in facts and circumstances, such as changes in tax law, interactions with taxing authorities and developments in case law, and adjustments are made as considered necessary. Adjustments to unrecognized tax benefits may affect income tax expense and the settlement of uncertain tax positions may require the use of cash.

Deferred federal income taxes arise from the recognition of temporary differences between the basis of assets and liabilities determined for financial reporting purposes and the basis determined for income tax purposes. ProAssurance’s temporary differences principally relate to loss reserves, unearned premium, deferred policy acquisition costs, unrealized investment gains (losses), basis differentials for investments, compensation accruals, and intangibles. Deferred tax assets and liabilities are measured using the enacted tax rates expected to be in effect when such benefits are realized. ProAssurance reviews its deferred tax assets quarterly for impairment. If management determines that it is more likely than not that some or all of a deferred tax asset will not be realized, a valuation allowance is recorded to reduce the carrying value of the asset. In assessing the need for a valuation allowance, management is required to make certain judgments and assumptions about the future operations of ProAssurance based on historical experience and information as of the measurement date regarding reversal of existing temporary differences, carryback capacity, future taxable income, including its capital and operating characteristics, and tax planning strategies.

Changes in tax laws and rates could also affect recorded deferred tax assets and liabilities in the future. Management is not aware of any such changes that would have a material effect on the Company’s results of operations, cash flows or financial position.

Real Estate

Real Estate balances are reported at cost or, for properties acquired in business combinations, estimated fair value on the date of acquisition, less accumulated depreciation. Real estate principally consists of properties in use as corporate offices. Depreciation is computed over the estimated useful lives of the related property using the straight-line method. Excess office capacity is leased or made available for lease; rental income is included in other income and real estate expenses are included in underwriting, policy acquisition and operating expenses.

Real estate accumulated depreciation was approximately $23.0 million and $21.6 million at December 31, 2014 and 2013, respectively. Real estate depreciation expense for the years ended December 31, 2014, 2013 and 2012 was $1.5 million, $1.5 million and $1.4 million, respectively.

Intangible Assets

Intangible assets with definite lives are amortized over the estimated useful life of the asset. Amortizable intangible assets primarily consist of agency and policyholder relationships. Intangible assets with an indefinite life, primarily state licenses, are not amortized. Both amortizable and non-amortizable intangible assets increased during 2014 due to intangible assets purchased in the Eastern acquisition, see Note 2. Intangible assets are evaluated for impairment on an annual basis. Information about ProAssurance's intangible assets is shown in the following table.

Gross Carrying Value

Accumulated Amortization

Amortization Expense

31-Dec

31-Dec

Year Ended December 31

(In millions)

2014

2013

2014

2013

2014

2013

2012

Intangible Assets

Non-amortizable

$

25.8

$

16.8

Amortizable

96.2

51.7

$

21.2

$

16.5

$

10.3

$

5.3

$

4.5

Total Intangible Assets

$

122

$

68.5

Aggregate amortization expense for intangible assets is estimated to be $8.3 million for 2015, $8.0 million for 2016, $5.6 million for 2017, $5.6 million for 2018 and $5.6 million for 2019.

Goodwill

Goodwill is recognized in conjunction with acquisitions as the excess of the purchase consideration for the acquisition over the fair value of identifiable assets acquired and liabilities assumed. The fair value of identifiable assets and liabilities, and thus goodwill, is subject to redetermination within a measurement period of up to one year following completion of an acquisition.

ProAssurance evaluates the carrying value of goodwill at the segment (or reporting unit) level annually as of October 1st. If, at any time during the year, events occur or circumstances change that would more likely than not reduce the fair value below the carrying value, an additional evaluation of goodwill is made.

The goodwill impairment assessment requires evaluating qualitative factors or performing a quantitative assessment to determine if a reporting unit’s carrying value is likely to exceed its fair value. ProAssurance elected to evaluate goodwill for each of its reporting units using qualitative factors to determine whether it was more likely than not that the fair value of a reporting unit was less than its carrying amount. In applying the qualitative approach, Management considered macroeconomic factors, such as industry and market conditions, as well as reporting-unit-specific events, actual financial performance versus expectations, and management’s future business expectations. For recently acquired reporting units with material goodwill, consideration was given to the fact that the business had been recently acquired in an orderly transaction between market participants, and that the purchase price therefore represented fair value at acquisition. A significant amount of judgment is required in performing the goodwill impairment analysis. As of October 1, 2014, the most recent evaluation date, Management concluded that the fair value of each ProAssurance reporting unit exceeded the carrying value of the reporting unit, and deemed it unnecessary to perform further testing for impairment.

Other Assets and Other Liabilities

At December 31, 2013, Other assets was principally comprised of a deposit with an intermediate third-party of $205 million, related to the completion of the Eastern Insurance Holdings, Inc. (Eastern) acquisition which closed on January 1, 2014. See Note 2.

Other liabilities at December 31, 2014 and 2013 consisted of the following:

(In millions)

2014

2013

Unpaid dividends

$

167.7

$

18.5

Segregated portfolio cell (SPC) dividends payable

15.8

—

All other

137.4

124.6

Total other liabilities

$

320.9

$

143.1

The SPC dividend payable represents the cumulative undistributed earnings of segregated portfolio cells that are contractually payable to external preferred shareholders of the cells. Unpaid dividends represents common stock dividends declared by ProAssurance's Board of Directors that have not yet been paid. Unpaid dividends increased for 2014 due to special dividends declared in the fourth quarter that were paid in 2015.

Treasury Stock

Treasury shares are reported at cost, and are reflected on the Consolidated Balance Sheets as an unallocated reduction of total equity.

Share-Based Payments

Compensation cost for share-based payments is measured based on the grant-date fair value of the award, recognized over the period in which the employee is required to provide service in exchange for the award. Excess tax benefits (tax deductions realized in excess of the compensation costs recognized for the exercise of the awards, multiplied by the incremental tax rate) are reported as financing cash inflows.

Subsequent Events

ProAssurance evaluates events that occurred subsequent to December 31, 2014, for recognition or disclosure in its Consolidated Financial Statements.

Accounting Changes Adopted

Obligations Resulting from Joint and Several Liability Arrangements

Effective for fiscal years beginning after December 15, 2013, the Financial Accounting Standards Board (FASB) revised guidance related to obligations resulting from joint and several liability arrangements. The new guidance requires an entity to recognize, measure and disclose obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date, except for obligations already addressed within existing GAAP guidance, with retrospective application required for such arrangements existing at the beginning of the fiscal year of adoption. ProAssurance adopted the guidance on January 1, 2014. Adoption of this guidance had no effect on ProAssurance's results of operations or financial position.

Presentation of Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists

Effective for fiscal years beginning after December 15, 2013, the FASB issued guidance related to the financial statement presentation of unrecognized tax benefits. The new guidance requires an entity to present unrecognized tax benefits as a reduction to a deferred tax asset resulting from a net operating loss carryforward, a similar tax loss, or tax credit carryforward except in circumstances where the relevant taxing authority does not permit offset or does not require offset and the entity does not intend to use the deferred tax asset for offset. The guidance requires prospective application for all unrecognized tax benefits that exist as of the effective date, but may be applied retrospectively. ProAssurance adopted the guidance prospectively on January 1, 2014. Adoption of this guidance had no material effect on ProAssurance's results of operations or financial position.

Equity Method and Joint Ventures-Accounting for Investments in Qualified Affordable Housing Projects

Effective for fiscal years beginning after December 15, 2014, the FASB issued guidance which, if certain criteria is met, permits but does not require reporting entities to begin using a new accounting method, the proportional amortization method, for investments in qualified affordable housing projects. The guidance also includes new disclosure requirements around the nature of investments in qualified affordable housing projects and their effect on financial position and results of operations. Under the proportional amortization method the investments in such projects are amortized in proportion to the tax benefits received, and investment performance is recognized as a component of income tax expense (benefit) rather than as a component of investment income. The tax credit partnership investments held by ProAssurance are primarily investments in qualified affordable housing projects. ProAssurance has adopted the new guidance as of December 31, 2014, but has elected to continue to account for these investments using the equity method of accounting. Adoption of this guidance had no material effect on ProAssurance’s results of operations or financial position as it affected disclosures only.

Determining Whether Hybrid Financial Instruments Issued as a Share is More Akin to Debt or to Equity

Effective for fiscal years beginning after December 15, 2015, early adoption permitted, the FASB issued guidance that clarifies current U.S. GAAP regarding the evaluation of the economic characteristics and risks of a host contract in a hybrid financial instrument that is issued in the form of a share. ProAssurance adopted the guidance as of December 31, 2014. Adoption of this guidance had no effect on ProAssurance’s results of operations or financial position.

Business Combinations: Pushdown Accounting

On November 18, 2014, the FASB issued immediately effective guidance on whether and at what threshold an acquired entity can apply pushdown accounting in its separate financial statements. ProAssurance has adopted this guidance as of its effective date. Adoption of this guidance had no effect on ProAssurance’s results of operations or financial position.

Income Statement Presentation of Extraordinary Items

Effective for fiscal years beginning after December 15, 2015, early adoption permitted, the FASB issued guidance that eliminates from U.S. GAAP the concept of extraordinary items and the related presentation requirements. Under the new guidance, the effect of each event or transaction that is unusual in nature or occurs infrequently, or both, is to be presented as a separate component of income from continuing operations or, alternatively, disclosed in notes to the financial statements. ProAssurance adopted the guidance as of January 1, 2014. Adoption of this guidance had no effect on ProAssurance’s results of operations or financial position.

Accounting Changes Not Yet Adopted

Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity

Effective for fiscal years beginning after December 15, 2014, the FASB issued guidance which changes the requirements for reporting discontinued operations. Under the new guidance, reporting entities are required to report disposals of business components only if the disposal represents a strategic shift in the entity’s operations that will have a major effect on the entity’s operations and financial results. The new guidance expands disclosure requirements for reported discontinued operations and requires disclosure of pre-tax profit or loss attributable to significant disposals that are not reported as discontinued operations. ProAssurance plans to adopt the guidance beginning January 1, 2015. Adoption of the guidance is expected to have no effect on ProAssurance’s results of operations or financial position.

Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period

Effective for fiscal years beginning after December 15, 2015, the FASB issued guidance for share-based payments in which the terms of the award provide that a performance target can be achieved after completion of the requisite service period. The new guidance provides that compensation cost for such awards should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered. ProAssurance plans to adopt the guidance beginning January 1, 2016. Adoption of the guidance is expected to have no effect on ProAssurance’s results of operations or financial position as ProAssurance has no awards with performance targets extending beyond the requisite service period.

Revenue from Contracts with Customers

Effective for fiscal years beginning after December 15, 2016, the FASB issued guidance related to revenue from contracts with customers. The core principle of the new guidance is that revenue should be 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, 2017. 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 expected to have no material effect on ProAssurance’s results of operations or financial position.

Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern

Effective for fiscal years ending after December 15, 2016 and interim periods beginning after December 15, 2016, the FASB issued guidance that establishes principles and definitions related to management's evaluation of whether there is substantial doubt about the organization's ability to continue as a going concern. For each interim and annual reporting period, the new guidance requires management to evaluate the organization's ability to meet its obligations as they are due within one year of the date the financial statements are issued and requires disclosure when there is substantial doubt regarding the organization's ability to continue as a going concern. ProAssurance plans to adopt the guidance on its effective date. Adoption is expected to have no effect on ProAssurance’s results of operations or financial position.

Business_Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Business Combinations	Business Combinations
	All entities acquired in 2014, 2013 and 2012 were accounted for in accordance with GAAP relating to Business Combinations.
	On January 1, 2014, ProAssurance completed the acquisition of Eastern by purchasing 100% of its outstanding common shares for cash of $205 million. Eastern is based in Lancaster, Pennsylvania and specializes in workers' compensation insurance and reinsurance products and services, including alternative market solutions. ProAssurance incurred expenses related to the purchase of approximately $2.2 million during the year ended December 31, 2014 and approximately $0.9 million during the year ended December 31, 2013. These expenses were included as a part of operating expenses in the periods incurred.
	On January 1, 2013, ProAssurance completed the acquisition of Medmarc Mutual Insurance Company, now Medmarc Casualty Insurance Company (Medmarc), through a sponsored demutualization. Medmarc is based in Chantilly, Virginia and provides products liability insurance for medical technology and life sciences companies and also provides legal professional liability insurance. ProAssurance acquired Medmarc for cash of $153.7 million, including the funding of future policy credits for eligible members of $7.5 million. ProAssurance transferred all of the cash required to complete the transaction to a third party agent for the benefit of Medmarc eligible members on December 27, 2012. ProAssurance incurred expenses related to the purchase of approximately $2.6 million during the year ended December 31, 2013 and approximately $1.0 million during the year ended December 31, 2012. These expenses were included as a part of operating expenses in the periods incurred.
	During 2012, ProAssurance also completed an acquisition of a reciprocal exchange that converted to a stock insurance company upon acquisition. The acquisition was not material to ProAssurance.
	The purchase consideration for both the acquisitions of Eastern and Medmarc was allocated to the assets acquired and liabilities assumed based on their estimated fair values on the acquisition dates, as shown in the table below. For the Eastern acquisition, goodwill of $49.6 million was recognized equal to the excess of the purchase price over the net fair value of identifiable assets acquired and liabilities assumed. Factors contributing to the recognition of goodwill include strategic and synergistic benefits that are expected to be realized as a result of the acquisition. These benefits include insurance market diversification, expanded access to alternative markets, and opportunities to reach additional insureds in the healthcare market by being a single source provider of a suite of insurance products. None of the goodwill is expected to be tax deductible.
	For the Medmarc acquisition, the purchase consideration was less than the estimated fair value of the net assets acquired resulting in a gain on the acquisition of $32.3 million. ProAssurance believes it was able to acquire Medmarc for less than the fair value of its net assets due to Medmarc's declining premium base and its small capital position relative to other insurers in the medical technology and life sciences products liability insurance market.
	(In thousands)		Eastern				Medmarc
	Fixed maturities, available for sale		$	107,131			$	269,529
	Equity securities, trading		65,945				30,976
	Cash and short-term investments		58,944				24,008
	Other investments		42,133				5,340
	Premiums receivable, net		71,989				2,986
	Receivable from reinsurers on paid and unpaid losses and LAE		18,942				73,107
	Intangible assets		59,000				3,630
	Deferred policy acquisition costs (see discussion below)		10,593				—
	Other assets		19,225				14,614
	Reserve for losses and loss adjustment expenses		(153,191		)		(201,072		)
	Unearned premiums		(80,268		)		(16,937		)
	Ceded balances payable		(9,507		)		—
	Segregated portfolio cells dividends payable		(14,430		)		—
	Deferred tax liabilities, net		(12,835		)		(4,934		)
	Other liabilities		(28,038		)		(15,233		)
	Fair value of net assets acquired		$	155,633			$	186,014
	Goodwill		49,610				—
	Gain on acquisition		—				(32,314		)
	Total purchase consideration		$	205,243			$	153,700
	Intangible assets acquired from Eastern and Medmarc included the following:
		Eastern					Medmarc
	(In millions)	Estimated Fair Value on Acquisition Date		Estimated			Estimated Fair Value on Acquisition Date		Estimated
				Useful Life					Useful Life
	Agency relationships	$27.00		15			$—		—
	Policyholder relationships	8		15			—		—
	Trade names	8		15			—		—
	Non-compete agreements	7		3			1.1		2		-1
	Total intangibles subject to amortization	$50.00		13	-2		$1.10		2		-2
	Insurance license agreements	$9.00		Indefinite			$2.50		Indefinite
	(1) Medmarc non-compete agreements were fully amortized as of December 31, 2014.
	(2) Reflects the weighted average estimated useful life of acquired intangible assets that are subject to amortization.
	ProAssurance's fair value estimate of the value of business acquired (VOBA), calculated as the present value of future earnings expected from the insurance contracts acquired, approximated the carrying value of Eastern's asset for deferred policy acquisition costs as of the acquisition date. Consequently, Eastern's asset for deferred policy acquisition costs was recognized in the purchase price allocation, as listed above, in lieu of recognizing an intangible asset for VOBA.
	ProAssurance believes that all contractual cash flows related to acquired receivables of both acquisitions will be collected. For Eastern, the fair values of the reserve for losses and loss adjustment expenses and related reinsurance recoverables were based on three components: an actuarial estimate of the expected future net cash flows, a reduction to those cash flows for the time value of money determined utilizing the U.S. Treasury Yield Curve, and a risk margin adjustment to reflect the net present value of profit that an investor would demand in return for the assumption of the development risk associated with the reserve. The fair value of the reserve, including the risk margin adjustment, exceeded the undiscounted loss reserve previously established by Eastern by $9.3 million; this fair value adjustment is being amortized over the average expected life of the reserve of 6 years as a reduction to loss expenses. For Medmarc, the fair values of the reserve for losses and loss adjustment expenses and related reinsurance recoverables were estimated based on the present value of the expected underlying net cash flows, including a 5% profit margin and a 5% risk premium, and were determined to be materially the same as the recorded cost basis acquired.
	The following table provides Pro Forma Consolidated Results for the years ended December 31, 2014, 2013 and 2012 as if the Eastern transaction had occurred on January 1, 2013 and the Medmarc transaction had occurred on January 1, 2012. ProAssurance Actual Consolidated Results have been adjusted by the following, net of related tax effects, to reflect the Pro Forma Consolidated Results below.
	•	For the year ended December 31, 2013, ProAssurance 2013 Actual Consolidated Results, which did not include Eastern, have been adjusted to include Eastern's 2013 operating results. ProAssurance Actual Consolidated Results for the year ended December 31, 2014 included Eastern's operating results (Revenue of $202.2 million and Net income of $9.1 million).
	•	For the year ended December 31, 2012, ProAssurance 2012 Actual Consolidated Results, which did not include Medmarc, have been adjusted to include Medmarc's 2012 operating results. ProAssurance Actual Consolidated Results for the years ended December 31, 2014 and 2013 included Medmarc's operating results (Revenue of $41.4 million and $46.5 million, respectively, and Net Income of $8.1 million and $15.7 million, respectively).
	•	Certain costs included in ProAssurance Actual Consolidated Results for the years ended December 31, 2014 and 2013 have been reported in the Pro Forma Consolidated Results as if the costs had been incurred for the years ended December 31, 2013 and 2012, respectively. Such costs include direct transaction costs and certain compensation costs directly related to the integration of Eastern and Medmarc operations.
	•	Prior to the acquisition date, Medmarc reported on a statutory basis and expensed policy acquisition costs associated with successful contracts as incurred. After the acquisition date, in accordance with GAAP, Medmarc policy acquisition costs associated with successful contracts were capitalized and amortized to expense as the related premium revenues were earned, but no amortization was recognized for Medmarc policies written prior to the acquisition date. The Pro Forma Consolidated Results for both 2013 and 2012 have been adjusted to reflect policy acquisition costs as if Medmarc had followed GAAP guidance for these costs in pre-acquisition periods.
	•	Net income for the years ended December 31, 2013 and 2012, respectively, was reduced to reflect amortization of intangible assets and debt security premiums and discounts recorded as a part of the Eastern and Medmarc purchase price allocations.
	•	The non-taxable gain on the Medmarc acquisition of $32.3 million that was included in ProAssurance Actual Consolidated Results for the year ended December 31, 2013 has been reported in the Pro Forma Consolidated Results as being recognized during the year ended December 31, 2012.
		Year Ended December 31, 2014				Year Ended December 31, 2013				Year Ended December 31, 2012
	(In thousands)	ProAssurance		ProAssurance		ProAssurance		ProAssurance		ProAssurance		ProAssurance
		Pro Forma		Actual		Pro Forma		Actual		Pro Forma		Actual
		Consolidated		Consolidated Results		Consolidated		Consolidated Results		Consolidated		Consolidated Results
		Results				Results				Results
	Revenue	$852,326		$852,326		$926,873		$740,178		$757,240		$715,854
	Net income	$197,533		$196,565		$263,446	*	$297,523		$317,097		$275,470
	* Includes adjustments related to Eastern of $0.4 million and Medmarc of $33.7 million.

Fair_Value_Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2014
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 December 31, 2014 and December 31, 2013, are shown in the following tables. 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.
		31-Dec-14
		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	$	—			$	166,512			$	—		$	166,512
	U.S. Government-sponsored enterprise obligations	—				39,563				—			39,563
	State and municipal bonds	—				1,057,590				5,025			1,062,615
	Corporate debt, multiple observable inputs	—				1,404,020				—			1,404,020
	Corporate debt, limited observable inputs:
	Other corporate debt, NRSRO ratings available	—				—				10,474			10,474
	Other corporate debt, NRSRO ratings not available	—				—				2,607			2,607
	Residential mortgage-backed securities	—				276,056				—			276,056
	Agency commercial mortgage-backed securities	—				15,493				—			15,493
	Other commercial mortgage-backed securities	—				51,063				—			51,063
	Other asset-backed securities	—				111,855				4,769			116,624
	Equity securities
	Financial	79,341				—				—			79,341
	Utilities/Energy	25,629				—				—			25,629
	Consumer oriented	65,670				—				—			65,670
	Industrial	55,460				—				—			55,460
	Bond funds	55,196				—				—			55,196
	All other	33,186				—				—			33,186
	Short-term investments	131,199				60				—			131,259
	Financial instruments carried at fair value, classified as a part of:
	Investment in unconsolidated subsidiaries	—				—				133,250			133,250
	Other investments	$	6,050			$	22,908			$	—		$	28,958
	Total assets	$	451,731			$	3,145,120			$	156,125		$	3,752,976
		31-Dec-13
		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	$	—			$	170,714			$	—		$	170,714
	U.S. Government-sponsored enterprise obligations	—				32,768				—			32,768
	State and municipal bonds	—				1,147,328				7,338			1,154,666
	Corporate debt, multiple observable inputs	—				1,346,977				—			1,346,977
	Corporate debt, limited observable inputs:
	Other corporate debt, NRSRO ratings available	—				—				11,449			11,449
	Other corporate debt, NRSRO ratings not available	—				—				2,727			2,727
	Residential mortgage-backed securities	—				235,614				—			235,614
	Agency commercial mortgage-backed securities	—				27,475				—			27,475
	Other commercial mortgage-backed securities	—				61,390				—			61,390
	Other asset-backed securities	—				67,455				6,814			74,269
	Equity securities
	Financial	81,536				—				—			81,536
	Utilities/Energy	32,350				—				—			32,350
	Consumer oriented	66,461				—				—			66,461
	Industrial	57,262				—				—			57,262
	All other	15,932				—				—			15,932
	Short-term investments	248,605											248,605
	Financial instruments carried at fair value, classified as a part of:
	Investment in unconsolidated subsidiaries	—				—				72,062			72,062
	Total assets	$	502,146			$	3,089,721			$	100,390		$	3,692,257
	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. If a value did not appear reasonable, the valuation was discussed with the service that provided the value and would have been adjusted, if necessary. No such adjustments were necessary at December 31, 2014 or 2013.
	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 with 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 by an outside vendor based upon a widely distributed, loan-specific listing of average bid and ask prices published daily by an investment industry group. The publisher of the listing derived the averages from data received from multiple market-makers for bank loans.
Residential and commercial mortgage backed securities. Agency pass-through 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 considered collateral type.
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 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 price.
•	Exclusive of Investments in unconsolidated subsidiaries, which are valued at NAV, the securities noted in the disclosure 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
State and municipal bonds consisted of auction rate municipal bonds valued internally using either published quotes for similar securities or values produced by discounted cash flow models using yields currently available on fixed rate securities with a similar term and collateral, adjusted to consider the effect of a floating rate and a premium for illiquidity. At December 31, 2014, 100% of the securities were rated; the average rating was A-.
Corporate debt with 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 December 31, 2014, the average rating of rated securities was A-.
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.
Investment in unconsolidated subsidiaries consisted of limited partnership (LP) and limited liability company (LLC) interests valued using the NAV provided by the LP/LLC, which approximated the fair value of the interest.
Such interests include the following:
	Unfunded	Fair Value
	Commitments
(In thousands)	December 31,	December 31,				December 31,
	2014	2014				2013
Investments in LPs/LLCs:
Private debt funds (1)	$27,578	$	37,296			$	13,233
Long equity fund (2)	None	6,747				6,574
Long/Short equity funds (3)	None	25,301				28,385
Non-public equity funds (4)	$66,545	51,811				23,870
Multi-strategy fund of funds (5)	None	8,271				—
Structured credit fund (6)	None	3,824				—
		$	133,250			$	72,062
-1	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 LPs over an anticipated time frame that spans from 3 to 8 years.
-2	This fund is an 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	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 event-driven market opportunities. The funds generally permit quarterly or semi-annual redemptions of the investors' existing capital balance with 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	Comprised of interests in three unrelated LP funds, each structured to provide capital appreciation through diversified investments in private equity, which can include investments in buyout, venture capital, mezzanine debt, distressed debt and other private equity-oriented LPs. One LP allows redemption by special consent; 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 9 years.
-5	This fund is an 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 the LLC Board is permitted discretion to periodically extend offers to repurchase units of the LLC.
-6	This fund is an 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.
ProAssurance may not sell, transfer or assign its interest in any of the above LPs/LLCs without special consent from the LPs/LLCs.
Quantitative Information Regarding Level 3 Valuations
Quantitative Information about Level 3 Fair Value Measurements
		Fair Value at
(In millions)		31-Dec-14		31-Dec-13		Valuation Technique		Unobservable Input		Range
										(Weighted Average)
Assets:
State and municipal bonds		$5.00		$7.30		Market Comparable		Comparability Adjustment		0% - 10% (5%)
						Securities
						Discounted Cash Flows		Comparability Adjustment		0% - 10% (5%)
Corporate debt with limited observable inputs		$13.10		$14.20		Market Comparable		Comparability Adjustment		0% - 5% (2.5%)
						Securities
						Discounted Cash Flows		Comparability Adjustment		0% - 5% (2.5%)
Other asset-backed securities		$4.80		$6.80		Market Comparable		Comparability Adjustment		0% - 5% (2.5%)
						Securities
						Discounted Cash Flows		Comparability Adjustment		0% - 5% (2.5%)
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.
	31-Dec-14
	Level 3 Fair Value Measurements – Assets
(In thousands)	U.S. Government-sponsored Enterprise Obligations				State and Municipal Bonds				Corporate Debt			Asset-backed Securities			Investment in Unconsolidated Subsidiaries			Total
Balance December 31, 2013	$	—			$	7,338			$	14,176		$	6,814		$	72,062		$	100,390
Total gains (losses) realized and unrealized:
Included in earnings, as a part of:
Net investment income	—				(14		)		65			—			—			51
Equity in earnings of unconsolidated subsidiaries	—				—				—			—			10,538			10,538
Net realized investment gains (losses)	—				(95		)		3			—			—			(92		)
Included in other comprehensive income	1				(29		)		688			59			—			719
Purchases	1,000				1,861				2,000			3,340			56,340			64,541
Sales	—				(1,731		)		(1,826		)	(61		)	(5,690		)	(9,308		)
Transfers in	—				2,119				—			305			—			2,424
Transfers out	(1,001		)		(4,424		)		(2,025		)	(5,688		)	—			(13,138		)
Balance December 31, 2014	$	—			$	5,025			$	13,081		$	4,769		$	133,250		$	156,125
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	$	—			$	—			$	—		$	—		$	10,538		$	10,538
	31-Dec-13
	Level 3 Fair Value Measurements – Assets
(In thousands)	U.S. Government-sponsored Enterprise Obligations				State and Municipal Bonds				Corporate Debt			Asset-backed Securities			Investment in Unconsolidated Subsidiaries			Total
Balance December 31, 2012	$	—			$	7,175			$	15,191		$	4,035		$	33,739		$	60,140
Total gains (losses) realized and unrealized:
Included in earnings, as a part of:
Net investment income	—				—				(103		)	(17		)	—			(120		)
Equity in earnings of unconsolidated subsidiaries	—				—				—			—			6,877			6,877
Net realized investment gains (losses)	—				(44		)		(69		)	—			—			(113		)
Included in other comprehensive income	—				1				(725		)	(61		)	—			(785		)
Purchases	—				—				9,470			1,356			24,567			35,393
Sales	—				(2,106		)		(1,629		)	(18		)	(14,632		)	(18,385		)
Transfers in	—				2,312				2,114			3,800			21,511			29,737
Transfers out	—				—				(10,073		)	(2,281		)	—			(12,354		)
Balance December 31, 2013	$	—			$	7,338			$	14,176		$	6,814		$	72,062		$	100,390
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	$	—			$	—			$	—		$	—		$	6,877		$	6,877
Transfers
There were no transfers between the Level 1 and Level 2 categories during 2014. Short-term investments of $7.2 million were transferred from Level 2 to Level 1 as of the end of 2013.
Transfers shown in the preceding Level 3 Tables were as of the end of the period and were to or from Level 2, unless otherwise noted.
The transfer in for Investment in unconsolidated subsidiaries reported in the Level 3 Tables for 2013 reflected an interest in an LP previously accounted for using the cost method and thus not carried at fair value. During 2013, the interest began to be accounted for using the equity method which approximates fair value.
All remaining transfers during 2014 and 2013 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.
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.
	31-Dec-14								31-Dec-13
(In thousands)	Carrying				Fair				Carrying			Fair
	Value				Value				Value			Value
Financial assets:
BOLI	$	56,381			$	56,381			$	54,374		$	54,374
Other investments	57,099				57,994				52,240			51,833
Other assets	22,440				22,399				17,940			17,940
Financial liabilities:
Senior notes due 2023	$	250,000			$	276,503			$	250,000		$	262,500
Other liabilities	14,656				14,645				13,303			13,303
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 LPs/LLCs accounted for using the cost method, investments in Federal Home Loan Bank (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 NAVs provided by the LP/LLC managers. 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 NAVs of the underlying securities. Other assets also included a secured note receivable and an unsecured receivable under a revolving credit agreement. 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. Other liabilities also included certain contractual liabilities related to prior business combinations. The fair values of the business combination liabilities were based on the present value of the expected future cash outflows, discounted at ProAssurance’s assumed incremental borrowing rate on the valuation date for unsecured liabilities with similar repayment structures.
The fair value of the long-term 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	12 Months Ended
	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Investments	Investments
	Available-for-sale securities at December 31, 2014 and December 31, 2013 included the following:
		31-Dec-14
	(In thousands)	Amortized			Gross Unrealized Gains				Gross Unrealized Losses				Estimated Fair Value
		Cost
	Fixed maturities
	U.S. Treasury obligations	$	163,714		$	3,785			$	987			$	166,512
	U.S. Government-sponsored enterprise obligations	38,022			1,641				100				39,563
	State and municipal bonds	1,015,555			47,395				335				1,062,615
	Corporate debt	1,389,970			44,234				17,103				1,417,101
	Residential mortgage-backed securities	266,306			10,198				448				276,056
	Agency commercial mortgage-backed securities	15,344			208				59				15,493
	Other commercial mortgage-backed securities	50,025			1,137				99				51,063
	Other asset-backed securities	116,541			288				205				116,624
		$	3,055,477		$	108,886			$	19,336			$	3,145,027
		31-Dec-13
	(In thousands)	Amortized			Gross Unrealized Gains				Gross Unrealized Losses				Estimated Fair Value
		Cost
	Fixed maturities
	U.S. Treasury obligations	$	166,115		$	6,118			$	1,519			$	170,714
	U.S. Government-sponsored enterprise obligations	30,942			2,251				425				32,768
	State and municipal bonds	1,116,060			46,533				7,927				1,154,666
	Corporate debt	1,321,838			53,059				13,744				1,361,153
	Residential mortgage-backed securities	230,861			7,608				2,855				235,614
	Agency commercial mortgage-backed securities	27,268			343				136				27,475
	Other commercial mortgage-backed securities	59,066			2,491				167				61,390
	Other asset-backed securities	74,106			487				324				74,269
		$	3,026,256		$	118,890			$	27,097			$	3,118,049
	The recorded cost basis and estimated fair value of available-for-sale fixed maturities at December 31, 2014, 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
		Cost			year or less				one year				five years		ten years		Value
									through				through
									five years				ten years
	Fixed maturities, available for sale
	U.S. Treasury obligations	$	163,714		$	9,584			$	113,489			$	39,264	$	4,175	$	166,512
	U.S. Government-sponsored enterprise obligations	38,022			3,641				25,286				10,287		349		39,563
	State and municipal bonds	1,015,555			44,334				380,741				453,275		184,265		1,062,615
	Corporate debt	1,389,970			115,301				711,806				566,585		23,409		1,417,101
	Residential mortgage-backed securities	266,306															276,056
	Agency commercial mortgage-backed securities	15,344															15,493
	Other commercial mortgage-backed securities	50,025															51,063
	Other asset-backed securities	116,541															116,624
		$	3,055,477														$	3,145,027
	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 December 31, 2014.
	Cash and securities with a carrying value of $49.3 million at December 31, 2014 were on deposit with various state insurance departments to meet regulatory requirements.
	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 Funds at Lloyd's (FAL). ProAssurance investments at December 31, 2014 included fixed maturities with a fair value of $85.0 million and short term investments with a fair value of approximately $0.2 million on deposit with Lloyd's in order to satisfy these FAL requirements.
	BOLI
	ProAssurance holds BOLI policies on management employees that are carried at the current cash surrender value of the policies (original cost $33 million). 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 principal beneficiary of these policies.
	Other Investments
	Other investments at December 31, 2014 and December 31, 2013 was comprised as follows:
	(In thousands)	December 31,			December 31,
		2014			2013
	Investments in LPs/LLCs, at cost	$	53,258		$	47,258
	Convertible securities, at fair value, see Note 1	28,958			—
	Other, principally FHLB capital stock, at cost	3,841			4,982
		$	86,057		$	52,240
	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.
	Unconsolidated Subsidiaries
	ProAssurance holds investments in unconsolidated subsidiaries, accounted for under the equity method. The investments include the following:
		31-Dec-14						Carrying Value
	(In thousands)	Unfunded			Percentage			December 31,				December 31,
		Commitments*			Ownership			2014				2013
	Investment in LPs/LLCs:
	Tax credit partnerships	$	15,537		See below			$	133,143			$	142,174
Private debt funds	27,578			<	20%		37,296				13,233
Long equity fund	None			<	20%		6,747				6,574
Long/short equity funds	None			<	25%		25,301				28,385
Non-public equity funds	80,070			<	20%		58,128				23,870
Multi-strategy fund of funds	—			<	20%		8,271				—
Structured credit fund	—			<	20%		3,824				—
Real estate fund	6,526			<	20%		3,791				—
							$	276,501			$	214,236
* Unfunded commitments are included in the carrying value of tax credit partnerships only.
Tax credit partnership interests held by ProAssurance generate investment returns by providing tax benefits to fund investors in the form of project operating losses and tax credits. The related properties are all qualified affordable housing projects. ProAssurance's ownership percentage relative to two of the tax credit partnership interests is almost 100%; these interests had a carrying value of $58.0 million at December 31, 2014. ProAssurance's ownership percentage relative to the remaining tax credit partnership interests is less than 20%; these interests had a carrying value of $75.1 million at December 31, 2014. All are accounted for under the equity method as ProAssurance does not have the ability to exert control over the partnerships.
The Private debt funds are structured to provide interest distributions primarily through diversified portfolios of private debt investments.
The Long equity fund targets long-term total returns through holdings in public international companies.
The Long/Short equity funds target absolute returns using strategies designed to take advantage of event-driven market opportunities.
The Non-public equity funds hold diversified private equities and are structured to provide capital appreciation.
The Multi-strategy fund of funds holds portfolios having little or no correlation to the broader fixed income and equity security markets.
The Structured credit fund seeks to obtain superior risk-adjusted absolute returns by acquiring and actively managing a diversified portfolio of debt securities.
The Real estate fund invests in multi-tenant industrial real estate with the objective of achieving superior absolute returns in all market cycles.
Investments Held in a Loss Position
The following tables provide summarized information with respect to investments held in an unrealized loss position at December 31, 2014 and December 31, 2013, including the length of time the investment had been held in a continuous unrealized loss position.
	31-Dec-14
	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	$	61,209		$	987			$	46,869			$	617	$	14,340	$	370
U.S. Government-sponsored enterprise obligations	6,268			100				2,775				44		3,493		56
State and municipal bonds	39,831			335				18,910				84		20,921		251
Corporate debt	423,107			17,103				326,804				13,236		96,303		3,867
Residential mortgage-backed securities	45,006			448				14,406				31		30,600		417
Agency commercial mortgage-backed securities	4,783			59				70				—		4,713		59
Other commercial mortgage-backed securities	13,860			99				7,005				28		6,855		71
Other asset-backed securities	62,577			205				59,176				109		3,401		96
	$	656,641		$	19,336			$	476,015			$	14,149	$	180,626	$	5,187
Other investments
Investments in LPs/LLCs carried at cost	$	23,683		$	3,948			$	22,265			$	3,711	$	1,418	$	237
	31-Dec-13
	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	$	47,668		$	1,519			$	44,304			$	1,182	$	3,364	$	337
U.S. Goverment-sponsored enterprise obligations	$	6,640		$	425			$	5,752			$	321	$	888	$	104
State and municipal bonds	203,970			7,927				184,401				6,640		19,569		1,287
Corporate debt	349,277			13,744				324,510				12,061		24,767		1,683
Residential mortgage-backed securities	93,608			2,855				84,045				2,393		9,563		462
Agency commercial mortgage-backed securities	11,658			136				11,082				116		576		20
Other commercial mortgage-backed securities	11,153			167				10,215				159		938		8
Other asset-backed securities	25,539			324				21,804				77		3,735		247
	$	749,513		$	27,097			$	686,113			$	22,949	$	63,400	$	4,148
Other investments
Investments in LPs/LLCs carried at cost	$	14,752		$	1,059			$	13,166			$	1,018	$	1,586	$	41
As of December 31, 2014, excluding U.S. government backed securities, there were 588 debt securities (20.5% of all available-for-sale fixed maturity securities held) in an unrealized loss position representing 434 issuers. The greatest and second greatest unrealized loss position among those securities were approximately $1.7 million and $0.7 million, respectively. The securities were evaluated for impairment as of December 31, 2014.
As of December 31, 2013, excluding U.S. government backed securities, there were 714 debt securities (26.3% of all available-for-sale fixed maturity securities held) in an unrealized loss position representing 516 issuers. Both the greatest and the second greatest unrealized loss position among those securities approximated $0.4 million. The securities were evaluated for impairment as of December 31, 2013.
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 other-than-temporary impairment in value. A detailed discussion of the factors considered in the assessment is included in Note 1.
Fixed maturity securities held in an unrealized loss position at December 31, 2014, 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 December 31, 2014 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:
	Year Ended December 31
(In thousands)	2014			2013				2012
Fixed maturities	$	111,895		$	122,065			$	133,088
Equities	10,817			9,454				6,947
Short-term and Other investments	8,833			2,584				660
Business owned life insurance	2,006			1,960				2,008
Investment fees and expenses	(7,994		)	(6,798		)		(6,609		)
Net investment income	$	125,557		$	129,265			$	136,094
Equity in Earnings (Loss) from Unconsolidated Subsidiaries
Equity in earnings (loss) from unconsolidated subsidiaries included losses due to amortization resulting from the allocable portion of the projected operating losses of qualified affordable housing project tax credits investments of $10.7 million, $10.1 million and $6.4 million for the years ended December 31, 2014, 2013 and 2012, respectively.
During 2013, ProAssurance's interest in one of its LPs increased and ProAssurance therefore determined it appropriate to begin applying the equity method of accounting instead of the previously applied cost method. Under GAAP such a change from the cost to the equity method should be made on a retroactive basis with restatement of prior periods. ProAssurance did not restate prior periods related to this method change as the amounts were not material to 2013 or any of the prior periods affected. Accordingly, Equity in earnings (loss) of unconsolidated subsidiaries for 2013 included ProAssurance's portion of the LP’s accumulated earnings from the date of initial investment, which totaled $10.5 million, of which $8.4 million was related to prior periods.
Net Realized Investment Gains (Losses)
The following table provides detailed information regarding net realized investment gains (losses):
	Year Ended December 31
(In thousands)	2014			2013				2012
Total other-than-temporary impairment losses:
State and municipal bonds	$	(50	)	$	(71	)		$	—
Residential mortgage-backed securities	—			—				(557		)
Corporate debt	(1,425		)	—				(878		)
Other investments	—			—				(131		)
Portion recognized in (reclassified from) Other Comprehensive Income:
Corporate debt	268			—				(201		)
Net impairments recognized in earnings	(1,207		)	(71		)		(1,767		)
Gross realized gains, available-for-sale securities	5,627			18,130				18,645
Gross realized (losses), available-for-sale securities	(1,103		)	(7,031		)		(2,076		)
Net realized gains (losses), trading securities	28,018			20,444				1,485
Net realized gains (losses), Other investments	326			—				—
Change in unrealized holding gains (losses), trading securities	(18,883		)	35,507				12,673
Change in unrealized holding gains (losses), convertible securities, carried at fair value	1,876			—				—
Decrease (increase) in the fair value of liabilities carried at fair value	—			—				(1,245		)
Other	—			925				1,148
Net realized investment gains (losses)	$	14,654		$	67,904			$	28,863
Credit-related impairments related to two corporate debt instruments were recognized during 2014. Additionally, a non-credit impairment related to one of the instruments was recognized as the fair value of the instrument was less than the expected future cash flows from the security. No significant impairment losses were recognized during 2013. During 2012, impairment losses were recognized related to certain residential mortgage-backed securities because carrying values for those securities were greater than the future cash flows expected to be received from the securities, and impairment losses for corporate debt securities were recognized because the credit standing of the issuers had deteriorated.
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 other-than-temporary impairment was recorded in Other comprehensive income.
(In thousands)	2014			2013				2012
Balance January 1	$	83		$	3,301			$	5,870
Additional credit losses recognized during the period, related to securities for which:
No OTTI has been previously recognized	149			—				—
OTTI has been previously recognized	—			—				268
Reductions due to:
Securities sold during the period (realized)	—			(3,218		)		(2,837		)
Balance December 31	$	232		$	83			$	3,301
Other information regarding sales and purchases of available-for-sale securities is as follows:
	Year Ended December 31
(In millions)	2014			2013			2012
Proceeds from sales (exclusive of maturities and paydowns)	$	244.9		$	593.3		$	500.2
Purchases	$	645.1		$	519.2		$	646.2

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2014
Insurance [Abstract]
Reinsurance	Reinsurance
	ProAssurance purchases reinsurance from third-party reinsurers and insurance enterprises in order to reduce its net exposure to losses. ProAssurance also uses reinsurance arrangements as a mechanism for sharing risk with insureds or their affiliates.
	The effect of reinsurance on premiums written and earned was as follows:
	(In thousands)	2014 Premiums						2013 Premiums						2012 Premiums
		Written			Earned			Written			Earned			Written			Earned
	Direct	$	761,043		$	755,623		$	566,745		$	568,629		$	536,318		$	558,200
	Assumed	18,566			12,987			802			804			113			116
	Ceded	(77,760		)	(68,879		)	(42,365		)	(41,514		)	(8,133		)	(7,652		)
	Net premiums	$	701,849		$	699,731		$	525,182		$	527,919		$	528,298		$	550,664
	The Receivable from reinsurers on unpaid losses and loss adjustment expenses represents Management’s estimate of amounts that will be recoverable under ProAssurance reinsurance agreements. Most Company reinsurance agreements base the amount of premium that is due to the reinsurer in part on losses reimbursed or to be reimbursed under the agreement, and terms may also include maximum and minimum amounts of ceded premium. Ceded premium amounts are estimated based on Management’s expectation of ultimate losses and the portion of those losses that are allocable to reinsurers according to the terms of the agreements, including any minimums or maximums. Given the uncertainty of the ultimate amounts of losses, Management’s estimates of losses and related amounts recoverable may vary significantly from the eventual outcome. During the years ended December 31, 2014, 2013 and 2012 ProAssurance reduced premiums ceded by $15.7 million, $16.4 million and $34.3 million, respectively, due to changes in Management’s estimates of amounts due to reinsurers related to prior accident year loss recoveries.
	Reinsurance contracts do not relieve ProAssurance from its obligations to policyholders and ProAssurance remains liable to its policyholders whether or not reinsurers honor their contractual obligations to ProAssurance. ProAssurance continually monitors its reinsurers to minimize its exposure to significant losses from reinsurer insolvencies.
	At December 31, 2014, $66.9 million of the net total amounts due from reinsurers of $259.1 million (including receivables related to paid and unpaid losses and LAE and prepaid reinsurance premiums, less reinsurance premiums payable) was due from three reinsurers which had an individual balance which exceeded $20 million. Each of these reinsurers had an A.M. Best credit rating of A or above. There were no individual reinsurers having a balance that exceeded 5% of shareholders’ equity.
	At December 31, 2014 reinsurance recoverables totaling approximately $35 million were collateralized by letters of credit or funds withheld. ProAssurance had no allowance for credit losses related to its reinsurance receivables at December 31, 2014 or 2013 as all reinsurance balances were considered collectible. During the years ended December 31, 2014, 2013 and 2012 no reinsurance balances were written off for credit reasons.
	There were no significant reinsurance commutations in 2014, 2013 or 2012.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Deferred income taxes reflect the net tax effects of temporary differences between the amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of ProAssurance’s deferred tax assets and liabilities were as follows:
	(In thousands)	2014			2013
	Deferred tax assets
	Unpaid loss discount	$	44,002		$	51,879
	Unearned premium adjustment	23,972			21,861
	Compensation related	18,623			18,172
	Intangibles	1,957			2,074
	Total deferred tax assets	88,554			93,986
	Deferred tax liabilities
	Deferred acquisition costs	9,180			10,150
	Unrealized gains on investments, net	31,342			32,127
	Fixed assets	3,689			4,166
	Basis differentials–investments	31,657			31,247
	Intangibles	27,294			13,238
	Other	4,210			1,301
	Total deferred tax liabilities	107,372			92,229
	Net deferred tax assets (liabilities)	$	(18,818	)	$	1,757
	At December 31, 2014, ProAssurance had no available net operating loss carryforwards, capital loss carryforwards, or Alternative Minimum Tax credit carryforwards. ProAssurance files income tax returns in the U.S. federal jurisdiction and various states.
	During 2013 the IRS issued a Notice of Proposed Adjustment (NOPA) to ProAssurance related to the 2009 and 2010 tax years. ProAssurance subsequently protested certain issues in the NOPA, all of which related to the timing of deductions. During 2014, ProAssurance and the IRS reached a final settlement on all contested issues which resulted in no additional tax liability for ProAssurance. The IRS subsequently refunded $30.6 million, exclusive of interest, to ProAssurance, reflecting both a refund from the settlement of non-contested issues addressed by the NOPA and the return of a protective payment made in 2013.
	ProAssurance had receivables for federal income taxes of $1.1 million at December 31, 2014 and $27.3 million at December 31, 2013, both carried as a part of Other Assets.
	The statute of limitations is now closed for all tax years prior to 2011.
	A reconciliation of the beginning and ending amounts of unrecognized tax benefits for 2014 and 2013 was as follows:
	(In thousands)	2014			2013			2012
	Balance at January 1	$	4,823		$	4,823		$	18,585
	Increase for tax position acquired as result of a business combination	414			—			—
	Increases for tax positions taken during the current year	163			—			—
	(Decreases) for tax positions taken during the current year	(4,823		)	—			(10,206		)
	(Decreases) for tax positions taken during prior years	—			—			(3,556		)
	Balance at December 31	$	577		$	4,823		$	4,823
	At December 31, 2014, all of ProAssurance's uncertain tax positions, if recognized, would affect the effective tax rate. None of ProAssurance's uncertain tax positions at December 31, 2013, if recognized, would have affected the effective tax rate. As with any uncertain tax position, there is a possibility that the ultimate benefit realized could differ from the estimate Management has established. Management does not expect any portion of unrecognized benefits at December 31, 2014 to reverse during the next twelve months.
	ProAssurance recognizes interest and/or penalties related to income tax matters in income tax expense. Interest recognized in the income statement was not significant during the years ended December 31, 2014, and 2013 and approximated $0.5 million in 2012. The accrued liability for interest was not significant at December 31, 2014 and approximated $1.3 million at December 31, 2013.
	A reconciliation of “expected” income tax expense (35% of income before income taxes) to actual income tax expense for each of the years ended December 31, 2014, 2013 and 2012 follows:
	(In thousands)	2014			2013			2012
	Computed “expected” tax expense	$	91,702		$	139,005		$	138,588
	Tax-exempt income	(13,250		)	(14,509		)	(14,374		)
	Tax credits, qualified affordable housing	(17,918		)	(17,888		)	(10,005		)
	Non-taxable gain on acquisition	—			(11,310		)	—
	Non-U.S. Loss	1,741			—			—
	Other	3,165			4,338			6,287
	Total	$	65,440		$	99,636		$	120,496

Deferred_Policy_Acquisition_Co

Deferred Policy Acquisition Costs	12 Months Ended
	Dec. 31, 2014
Insurance [Abstract]
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs
	Policy acquisition costs, that are primarily and directly related to the successful production of new and renewal insurance contracts, most significantly agent commissions, premium taxes and underwriting salaries and benefits, are capitalized as policy acquisition costs and amortized to expense, net of ceding commissions earned, as the related premium revenues are earned.
	Amortization of deferred policy acquisition costs was $68.6 million, $53.2 million and $54.9 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Reserve_for_Losses_and_Loss_Ad

Reserve for Losses and Loss Adjustment Expenses	12 Months Ended
	Dec. 31, 2014
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 significantly 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 and 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 in accordance with the requirements of the NAIC.
	Activity in the reserve for losses and loss adjustment expenses is summarized as follows:
	(In thousands)	2014			2013			2012
	Balance, beginning of year	$	2,072,822		$	2,054,994		$	2,247,772
	Less reinsurance recoverables on unpaid losses and loss adjustment expenses	247,518			191,645			247,658
	Net balance, beginning of year	1,825,304			1,863,349			2,000,114
	Net reserves acquired from acquisitions	139,549			126,007			22,464
	Net losses:
	Current year	545,168			447,510			451,951
	Favorable development of reserves established in prior years, net	(182,084		)	(222,749		)	(272,038		)
	Total	363,084			224,761			179,913
	Paid related to:
	Current year	(93,737		)	(43,616		)	(38,439		)
	Prior years	(413,900		)	(345,197		)	(300,703		)
	Total paid	(507,637		)	(388,813		)	(339,142		)
	Net balance, end of year	1,820,300			1,825,304			1,863,349
	Plus reinsurance recoverables on unpaid losses and loss adjustment expenses	237,966			247,518			191,645
	Balance, end of year	$	2,058,266		$	2,072,822		$	2,054,994
	As discussed in Note 1, estimating liability reserves is complex and requires the use of many assumptions. As time passes and ultimate losses for prior years are either known or become subject to a more precise estimation, ProAssurance increases or decreases the reserve estimates established in prior periods. The favorable loss development recognized in 2014 primarily reflects a lower than anticipated claims severity trend (i.e. the average size of a claim) for accident years 2007 through 2011. The favorable development recognized in 2013 and 2012 was primarily due to lower than anticipated claims severity trends for accident years 2005 through 2011 and accident years 2004 through 2009, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
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 of Note 1.
	ProAssurance has funding commitments primarily related to non-public investment entities totaling approximately $169.4 million, expected to be paid as follows: $98.8 million in 2015, $69.2 million in 2016 and 2017 combined, $0.6 million in 2018 and 2019 combined, and $0.8 million thereafter. Of these funding commitments, $15.5 million are related to qualified affordable housing project tax credit investments and are expected to be paid as follows: $14.1 million in 2015, $0.5 million in 2016 and 2017 combined, $0.3 million in 2018 and 2019 combined and $0.6 million thereafter.
	As a member of Lloyd's and a capital provider to Syndicate 1729, ProAssurance is required to provide capital, referred to as FAL. At December 31, 2014, ProAssurance is satisfying the FAL requirement with investment securities on deposit with Lloyd's with a carrying value of $85.2 million (see Note 4). At December 31, 2013, the FAL requirement was primarily met through a standby letter of credit (LOC).
	ProAssurance has issued an unconditional revolving credit agreement (the "Syndicate Credit Agreement") of up to £10 million ($16 million at December 31, 2014) to the Premium Trust Fund of Syndicate 1729 for the purpose of providing working capital. Advances under the Syndicate Credit Agreement bear interest at 8.5% annually, and are repayable upon demand after December 31, 2016. As of December 31, 2014, £6.6 million ($11.0 million) had been advanced under the Syndicate Credit Agreement.
	ProAssurance is involved in a number of operating leases primarily for office space and office equipment. The following is a schedule of future minimum lease payments for operating leases that had initial or remaining non-cancelable lease terms in excess of one year as of December 31, 2014.
	Operating Leases
	(In thousands)
	2015	$	5,024
	2016	4,915
	2017	3,601
	2018	2,965
	2019	2,572
	Thereafter	5,232
	Total minimum lease payments	$	24,309
	ProAssurance incurred rent expense of $5.0 million, $3.2 million and $2.7 million in the years ended December 31, 2014, 2013 and 2012, respectively.

Longterm_Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt
	ProAssurance’s outstanding long-term debt consisted of the following:
	(In thousands)	December 31,		December 31,
		2014		2013
	Senior notes due 2023, unsecured, interest at 5.3% annually	$	250,000	$	250,000
	Revolving credit agreement, outstanding borrowings not permitted to exceed $200 million aggregately, expires in 2016	—		—
		$	250,000	$	250,000
	Senior Notes due 2023 (the Senior Notes)
	The Senior Notes are the unsecured obligations of ProAssurance Corporation, due in full in November 2023, unless sooner redeemed, with interest payable semiannually. Redemptions may be made prior to maturity, in whole or part, at the greater of par or the sum of the present values of the outstanding principal and remaining interest payments calculated at 40 basis points above the then-current rate for U.S. Treasury Notes with a term comparable to the remaining term of the Senior Notes. There are no financial covenants associated with the Senior Notes.
	Revolving Credit Agreement
	ProAssurance has entered into a revolving credit agreement (the “Credit Agreement”) with five participating lenders with an expiration date of April 15, 2016. The Credit Agreement permits ProAssurance to borrow, repay and reborrow from the lenders during the term of the Credit Agreement. All borrowings are required to be repaid prior to the expiration date of the Credit Agreement. ProAssurance is required to pay a commitment fee, ranging from 15 to 30 basis points based on ProAssurance’s credit ratings, on the average unused portion of the credit line during the term of the Credit Agreement. Borrowings under the Credit Agreement may be secured or unsecured and accrue interest at a selected base rate, adjusted by a margin, which can vary from 0 to 188 basis points, based on ProAssurance’s credit rating and whether the borrowing is secured or unsecured. The base rate selected may either be the current one-, three- or six-month LIBOR rate, with the LIBOR term selected fixing the interest period for which the rate is effective. If LIBOR is not selected, the base rate defaults to the highest of (1) the Prime rate (2) the Federal Funds rate plus 50 basis points or (3) the one month LIBOR rate plus 100 basis points, determined daily. Rates are reset each successive interest period until the borrowing is repaid.
	The Credit Agreement contains customary representations, covenants and events constituting default, and remedies for default. Additionally, the Credit Agreement carries the following financial covenants:
	-1	ProAssurance is not permitted to have a leverage ratio of Consolidated Funded Indebtedness (principally, obligations for borrowed money, obligations evidenced by instruments such as notes or acceptances, standby and commercial Letters of Credit, and contingent obligations) to Consolidated Total Capitalization (principally, total non-trade liabilities on a consolidated basis plus consolidated shareholders’ equity, exclusive of accumulated other comprehensive income) greater than 0.35 to 1.0, determined at the end of each fiscal quarter.
	-2	ProAssurance is required to maintain a minimum net worth of not less than the sum of 75% of Consolidated Net Worth (consolidated shareholders’ equity, exclusive of accumulated other comprehensive income) at December 31, 2010, plus 50% of consolidated net income earned each fiscal quarter, if positive, beginning with the quarter ending March 31, 2011, plus 100% of net cash proceeds resulting from the issuance of ProAssurance capital stock.
	Funds borrowed under the terms of the Credit Agreement will be used for general corporate purposes, including, but not limited to, use as short-term working capital, funding for share repurchases as authorized by the Board, and for support of other activities ProAssurance enters into in the normal course of business.
	Covenant Compliance
	ProAssurance is currently in compliance with all covenants.
	Loss on Extinguishment
	ProAssurance recognized a $2.2 million loss on extinguishment of debt during 2012 upon repayment of a note payable carried at fair value.

Shareholders_Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity
	At December 31, 2014 and 2013, 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.
	The following is a summary of changes in common shares issued and outstanding during the years ended December 31, 2014, 2013 and 2012:
	(In thousands of shares)	2014			2013			2012
	Issued and outstanding shares - January 1	61,197			61,624			61,107
	Repurchase of shares	(4,909	)		(681	)		—
	Shares issued due to exercise of options and vesting of share-based compensation awards	154			169			436
	Other shares issued for compensation and shares reissued to stock purchase plan*	92			85			81
	Issued and outstanding shares - December 31	56,534			61,197			61,624
	*	Shares issued were valued at fair value (the market price of a ProAssurance common share on the date of issue).
	As of December 31, 2014, approximately 2.7 million of ProAssurance's authorized common shares were reserved by the Board for award or issuance under the incentive compensation plans described in Note 12 and an additional 0.8 million of authorized common shares were reserved for the issuance of currently outstanding restricted share and performance share unit awards and for the exercise of outstanding stock options.
	ProAssurance declared cash dividends during 2014, 2013 and 2012 as follows:
			Cash Dividends Declared, per Share
			2014				2013			2012
	First Quarter		$	0.3			$	0.25		$	0.125
	Second Quarter		$	0.3			$	0.25		$	0.125
	Third Quarter		$	0.3			$	0.25		$	0.125
	Fourth Quarter*		$	2.96			$	0.3		$	2.75
	* Includes special dividends of $2.65 per share in 2014 and $2.50 per share in 2012.
	Dividends declared during 2014, 2013 and 2012 totaled $220.5 million, $64.8 million and $192.5 million, respectively. These dividends were paid in the month following the quarter in which they were declared, except for fourth quarter 2012 dividends for which payment was accelerated into December 2012.
	ProAssurance's ability to pay dividends to its shareholders is limited by its holding company structure, to the extent of the net assets held by its insurance subsidiaries, as discussed in Note 17. Otherwise, there are no other regulatory restrictions on ProAssurance's retained earnings or net income that materially impact its ability to pay dividends. Based on Shareholders' Equity at December 31, 2014, total equity of $239 million was free of debt covenant restrictions regarding the payment of dividends. However, any decision to pay future cash dividends is subject to the Board’s final determination after a comprehensive review of financial performance, future expectations and other factors deemed relevant by the Board.
	As of December 31, 2014 Board authorizations for the repurchase of common shares or the retirement of outstanding debt of $181.5 million remained available for use. The timing and quantity of purchases depends upon market conditions and changes in ProAssurance's capital requirements and is subject to limitations that may be imposed on such purchases by applicable securities laws and regulations, and the rules of the New York Stock Exchange.
	Other Comprehensive Income (Loss) (OCI)
	For the years ended December 31, 2014, 2013 and 2012, OCI was primarily comprised of unrealized gains and losses arising during the period related to available-for-sale securities, less reclassification adjustments as shown in the table below, net of tax. At December 31, 2014 and 2013, accumulated other comprehensive income was comprised primarily of unrealized gains and losses from available-for-sale securities, including non-credit impairment losses of $0.8 million and 0.5 million, respectively, net of tax. All tax effects were computed using a 35% rate. OCI and accumulated other comprehensive income also included immaterial amounts of foreign currency translation adjustments.
	Amounts reclassified from accumulated other comprehensive income to net income and the amounts of deferred tax expense (benefit) included in OCI were as follows:
	(In thousands)	2014				2013			2012
	Reclassifications from accumulated other comprehensive income to net income, available-for-sale securities:
	Realized investment gains (losses)	$	3,317			$	11,375		$	17,350
	Non-credit impairment losses reclassified to earnings, due to sale of securities or reclassification as a credit loss	—				(347		)	(2,417		)
	Total amounts reclassified, before tax effect	3,317				11,028			14,933
	Tax effect (at 35%)	(1,161		)		(3,860		)	(5,227		)
	Net reclassification adjustments	$	2,156			$	7,168		$	9,706
	Deferred tax expense (benefit) included in OCI	$	(785	)		$	(46,157	)	$	8,262

ShareBased_Payments

Share-Based Payments	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Payments	Share-Based Payments
	Share-based compensation costs are primarily classified as underwriting, policy acquisition and operating expenses.
	Since May 2013, ProAssurance has provided share-based compensation to employees under the ProAssurance Corporation Amended and Restated 2014 Equity Incentive Plan. Previously, compensation was provided under the ProAssurance Corporation 2008 Equity Incentive Plan (2009 to May 2013), and the ProAssurance Corporation 2004 Equity Incentive Plan (2005 to 2008). The Compensation Committee of the Board is responsible for the administration of each plan.
	ProAssurance has provided share-based compensation to employees utilizing four types of awards: stock options, restricted share units, performance share units and purchase match units. The following table provides a summary of compensation expense and compensation cost that will be charged to expense in future periods, by award type, and the total related tax benefit recognized during each period. There was no compensation expense related to stock option awards in 2014, 2013 or 2012.
		Share-Based										Unrecognized Compensation Cost
		Compensation Expense
		Year Ended December 31										31-Dec-14
		2014			2013			2012				Amount				Remaining
																Recognition Period
		(In millions)										(In millions)				(Weighted average years)
	Restricted Share Units	1.7			1.6			1.6				2				1.8
	Performance Share Units	7.6			7.1			6.7				6.3				1.7
	Purchase Match Units	0.8			0.5			0.3				1.6				2.2
	Total share-based compensation expense	$	10.1		$	9.2		$	8.6			$	9.9
	Tax benefit recognized	$	3.5		$	3.2		$	3
	The above awards are charged to expense as an increase to equity over the service period (generally the vesting period) associated with the award. Awards 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 restricted, performance or purchase match unit once vesting requirements are met, except that units sufficient to satisfy required tax withholdings are paid in cash.
	Stock Options
	Activity for ProAssurance stock option awards during 2014, 2013 and 2012 is summarized below.
		2014					2013							2012
		Options		Weighted			Options			Weighted				Options			Weighted
				Average						Average							Average
				Exercise						Exercise							Exercise
				Price						Price							Price
	Outstanding, beginning of year	18,082		$	23		20,302			$	23.15			1,014,661			$	22.76
	Granted	—		—			—			—				—			—
	Exercised	(13,626	)	22.47			(2,220	)		24.28				(994,148	)		22.75
	Forfeited or expired	—		—			—			—				(211	)		25.67
	Outstanding at end of year	4,456		24.64			18,082			23				20,302			23.15
	Exercisable at end of year	4,456		24.64			18,082			23				20,302			23.15
	Outstanding at end of year,	4,456		24.64			18,082			23				20,302			23.15
	vested or expected to vest
	All options were vested as of December 31, 2012. The aggregate grant date fair value of options vested during the year ended December 31, 2012 was $0.9 million. The aggregate intrinsic value of options exercised during 2014, 2013 and 2012 was $0.3 million, $0.1 million and $19.8 million, respectively. ProAssurance outstanding options had an aggregate intrinsic value of $0.1 million and a weighted average remaining contractual term of 2.44 years at December 31, 2014. All ProAssurance option agreements permit cashless exercise whereby the exercise price and any required tax withholdings are allowed to be satisfied by the retention of shares that would otherwise be deliverable to the option holder. ProAssurance issues new shares for options exercised. There were no cash proceeds from options exercised during the years ended December 31, 2014, 2013 or 2012.
	Restricted Share Units
	Activity for restricted share units during 2014, 2013 and 2012 is summarized below. Grant date fair values are based on the market value of a ProAssurance common share on the date of grant.
		2014					2013							2012
		Units		Weighted			Units			Weighted				Units			Weighted
				Average						Average							Average
				Grant Date						Grant Date							Grant Date
				Fair Value						Fair Value							Fair Value
	Beginning non-vested balance	138,770		$	38.92		157,212			$	31.94			167,236			$	25.52
	Granted	49,750		46.34			39,400			46.97				51,864			42.22
	Forfeited	(2,044	)	44.88			(603	)		35.91				(2,823	)		35.23
	Vested and released	(49,674	)	29.22			(57,239	)		25.25				(59,065	)		22.61
	Ending non-vested balance	136,802		45.02			138,770			38.92				157,212			31.94
	The aggregate grant date fair value of restricted share units vested and released in 2014, 2013 and 2012 totaled $1.5 million, $1.4 million and $1.3 million, respectively. The aggregate intrinsic value of restricted share units vested and released in 2014, 2013 and 2012 (including units paid in cash to cover tax withholdings) totaled $2.3 million, $2.7 million and $2.6 million, respectively.
	Performance Share Units
	Performance share units vest only if minimum performance objectives are met, and the number of units earned varies from 75% to 125% of a base award depending upon the degree to which stated performance objectives are achieved. Performance share unit activity for 2014, 2013 and 2012 is summarized below. The table reflects the base number of units; actual awards that vest depends upon the extent to which performance objectives are achieved. Grant date fair values are based on the market value of a ProAssurance common share on the date of grant.
		2014					2013							2012
		Base Units		Weighted			Base Units			Weighted				Base Units			Weighted
				Average						Average							Average
				Grant Date						Grant Date							Grant Date
				Fair Value						Fair Value							Fair Value
	Beginning non-vested balance	486,680		$	39.86		552,417			$	33.21			522,599			$	26.36
	Granted	160,900		46.34			145,580			46.97				212,205			42.22
	Forfeited	(14,221	)	45.3			(17,043	)		38.9				(20,492	)		31.44
	Vested and released	(166,499	)	31.33			(194,274	)		26.39				(161,895	)		23.13
	Ending non-vested balance	466,860		44.97			486,680			39.86				552,417			33.21
	The aggregate grant date fair value of performance share units (base level) vested and released in 2014, 2013 and 2012 totaled $5.2 million, $5.1 million and $3.7 million, respectively. The aggregate intrinsic value of performance share units vested and released in 2014, 2013 and 2012 (including units paid in cash to cover tax withholdings) totaled $7.7 million, $9.1 million and $7.2 million, respectively. The vested units were issued at the maximum level (125%) based on performance levels achieved.
	Purchase Match Units
	The ProAssurance Corporation 2011 Employee Stock Ownership Plan provides a purchase match unit for each share purchased with contributions by eligible plan participants, with participant contributions subject to a $5,000 annual limit per participant. Purchase match unit activity during 2014, 2013 and 2012 is summarized below. Grant date fair values are based on the market value of a ProAssurance common share on the date of grant.
		2014					2013							2012
		Units		Weighted			Units			Weighted				Units			Weighted
				Average						Average							Average
				Grant  Date						Grant  Date							Grant  Date
Fair Value				Fair Value						Fair Value
Beginning non-vested balance	63,125		$	41.34		40,985			$	39.85			18,900			$	36.2
Granted	29,069		44.55			25,151			43.57				23,799			42.59
Forfeited	(2,968	)	43.14			(2,456	)		40.71				(1,610	)		37.72
Vested and released	(17,125	)	36.61			(555	)		36.33				(104	)		36.2
Ending non-vested balance	72,101		43.69			63,125			41.34				40,985			39.85
The aggregate grant date fair value of purchase match units vested and released in 2014 totaled $0.6 million and the aggregate intrinsic value of purchase match share units vested and released in 2014 (including units paid in cash to cover tax withholdings) totaled $0.8 million. In both 2013 and 2012 the aggregate grant date fair value and the aggregate intrinsic value of units vested were nominal as 2014 was the first full vesting period.

Variable_Interest_Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2014
Variable Interest Entities [Abstract]
Variable Interest Entities	Variable Interest Entities
	ProAssurance holds passive interests in a number of entities that are considered to be Variable Interest Entities (VIEs) under GAAP guidance. ProAssurance's VIE interests principally consist of interests in LPs/LLCs formed for the purpose of achieving diversified equity and debt returns. ProAssurance VIE interests carried as a part of Other investments totaled $33.3 million at December 31, 2014 and $27.3 million at December 31, 2013. ProAssurance VIE interests, carried as a part of Investment in unconsolidated subsidiaries, totaled $65.0 million at December 31, 2014 and $49.5 million at December 31, 2013.
	ProAssurance has not consolidated these VIEs because it has either very limited or no power to control the activities that most significantly affect the economic performance of these entities and is not the primary beneficiary of any of the entities. ProAssurance’s involvement with each entity is limited to its direct ownership interest in the entity. ProAssurance has no arrangements with any of the entities to provide other financial support to or on behalf of the entity. At December 31, 2014, 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	12 Months Ended
	Dec. 31, 2014
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 dilutive stock options have been exercised and that performance, restricted, and purchase share units have vested. All outstanding stock options, performance, restricted, and purchase share units had a dilutive effect for the years ended December 31, 2014, 2013 and 2012.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
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 and life sciences products liability insurance. The professional liability business primarily offers professional liability insurance to healthcare providers and institutions and to attorneys and their firms. The medical technology and life sciences business offers products liability insurance for medical technology and life sciences companies that manufacture or distribute products. The Specialty P&C segment cedes certain premium to the Lloyd's Syndicate segment under an agreement with Syndicate 1729. As discussed below, Syndicate 1729 operating results are reported on a quarter delay. The ceded premium associated with the Syndicate 1729 reinsurance agreement has been reported within the Specialty P&C segment on a similar lag, as this results in the ceded premium being reported in the same period in which the Lloyd's Syndicate segment reports the corresponding assumed premium.
	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 a captive insurer unaffiliated with ProAssurance or to SPCs operated by a wholly owned subsidiary of ProAssurance. The SPCs are fully or partially owned by the employer (or employer group, association or affiliate) insured by the policies ceded. Financial results (underwriting profit or loss, plus investment income) of the SPCs accrue to the owners of that cell. Our Workers' Compensation segment is comprised entirely of the business acquired through Eastern on January 1, 2014.
	Lloyd's Syndicate includes operating results from ProAssurance's 58% participation in Lloyd's of London Syndicate 1729 that began writing business as of January 1, 2014. Syndicate 1729 underwrites risks over a wide range of property and casualty insurance and reinsurance lines. The results of this segment are reported on a quarter delay, except that investment results associated with the FAL investments and certain U.S. paid administrative expenses, primarily start-up costs, are reported concurrently as that information is available on an earlier time frame.
	Corporate includes ProAssurance's U.S. investment operations, interest expense and U.S. income taxes, all of which are managed at the corporate level, 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. ProAssurance evaluates performance of its Specialty P&C and Workers' Compensation segments based on before tax underwriting profit or loss, and excludes investment performance. Performance of the Lloyd's Syndicate segment is evaluated based on underwriting profit or loss, and 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 sales and transfers as if the sales or transfers were to third parties at current market prices. Assets are not allocated to segments because investments and assets are not managed at the segment level.
	Financial data by segment for the years December 31, 2014, 2013 and 2012 were as follows:
		Year Ended December 31, 2014
	(In thousands)	Specialty P&C				Workers' Compensation				Lloyd's Syndicate				Corporate			Inter-segment Eliminations			Consolidated
	Net premiums earned	$	492,733			$	194,540			$	12,458			$	—		$	—		$	699,731
	Net investment income	—				—				410				125,147			—			125,557
	Equity in earnings (loss) of unconsolidated subsidiaries	—				—				—				3,986			—			3,986
	Net realized gains (losses)	—				—				4				14,650			—			14,654
	Other income	5,823				645				126				2,285			(481		)	8,398
	Net losses and loss adjustment expenses	(228,199		)		(126,447		)		(8,438		)		—			—			(363,084		)
	Underwriting, policy acquisition and operating expenses	(133,132		)		(60,357		)		(9,535		)		(8,768		)	481			(211,311		)
	Segregated portfolio cells dividend expense	—				(1,842		)		—				—			—			(1,842		)
	Interest expense	—				—				—				(14,084		)	—			(14,084		)
	Income tax benefit (expense)	—				—				—				(65,440		)	—			(65,440		)
	Segment operating results	$	137,225			$	6,539			$	(4,975	)		$	57,776		$	—		$	196,565
	Significant non-cash items
	Depreciation and amortization	$	8,945			$	5,828			$	477			$	35,073		$	—		$	50,323
		Year Ended December 31, 2013
	(In thousands)	Specialty P&C				Workers' Compensation				Lloyd's Syndicate				Corporate			Inter-segment Eliminations			Consolidated
	Net premiums earned	$	527,919			$	—			$	—			$	—		$	—		$	527,919
	Net investment income	—				—				—				129,265			—			129,265
	Equity in earnings (loss) of unconsolidated subsidiaries	—				—				—				7,539			—			7,539
	Net realized gains (losses)	—				—				—				67,904			—			67,904
	Other income	5,648				—				—				1,910			(7		)	7,551
	Gain on acquisition	—				—				—				32,314			—			32,314
	Net losses and loss adjustment expenses	(224,761		)		—				—				—			—			(224,761		)
	Underwriting, policy acquisition and operating expenses	(132,076		)		—				—				(15,748		)	7			(147,817		)
	Interest expense	—				—				—				(2,755		)	—			(2,755		)
	Income tax benefit (expense)	—				—				—				(99,636		)	—			(99,636		)
	Segment operating results	$	176,730			$	—			$	—			$	120,793		$	—		$	297,523
	Significant non-cash items
	Depreciation and amortization	$	7,199			$	—			$	—			$	38,768		$	—		$	45,967
		Year Ended December 31, 2012
	(In thousands)	Specialty P&C				Workers' Compensation				Lloyd's Syndicate				Corporate			Inter-segment Eliminations			Consolidated
	Net premiums earned	$	550,664			$	—			$	—			$	—		$	—		$	550,664
	Net investment income	—				—				—				136,094			—			136,094
	Equity in earnings (loss) of unconsolidated subsidiaries	—				—				—				(6,873		)	—			(6,873		)
	Net realized gains (losses)	—				—								28,863			—			28,863
	Other income	5,331				—				—				1,825			(50		)	7,106
	Gain on acquisition	—				—				—				—			—			—
	Net losses and loss adjustment expenses	(179,913		)		—				—				—			—			(179,913		)
	Underwriting, policy acquisition and operating expenses	(125,292		)		—				—				(10,389		)	50			(135,631		)
	Interest expense	—				—				—				(2,181		)	—			(2,181		)
	Loss on extinguishment of debt	—				—				—				(2,163		)	—			(2,163		)
	Income tax benefit (expense)	—												(120,496		)				(120,496		)
	Segment operating results	$	250,790			$	—			$	—			$	24,680		$	—		$	275,470
	Significant non-cash items
	Depreciation and amortization	$	7,355			$	—			$	—			$	30,218		$	—		$	37,573
	The following table provides detailed information regarding gross premiums earned by major category within each segment 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 United States.
			Year Ended December 31
	(In thousands)		2014				2013				2012
	Specialty P&C Segment
	Gross premiums earned:
	Healthcare professional liability		$	477,031			$	507,222			$	539,729
	Legal professional liability		28,278				27,162				17,042
	Medical technology and life sciences products liability		35,913				33,242				—
	Other		1,830				1,807				1,545
	Ceded premiums earned*		(50,319		)		(41,514		)		(7,652		)
Segment net premiums earned		$	492,733			$	527,919			$	550,664
Workers' Compensation Segment
Gross premiums earned:
Traditional business		$	160,717			$	—			$	—
Alternative market business		55,616				—				—
Ceded premiums earned		(21,793		)		—				—
Segment net premiums earned		$	194,540			$	—			$	—
Lloyd's Syndicate Segment
Gross premiums earned:
Property and casualty*		$	13,429			$	—			$	—
Ceded premiums earned		(971		)		—				—
Segment net premiums earned		$	12,458			$	—			$	—
Consolidated net premiums earned		$	699,731			$	527,919			$	550,664
* Includes premium ceded from the Specialty P&C Segment to the Lloyd's Syndicate Segment of $4.2 million for year ended December 31, 2014.

Benefit_Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Benefit Plans	Benefit Plans
	ProAssurance maintains a defined contribution savings and retirement plan (the ProAssurance Savings Plan) that is intended to provide retirement income to eligible employees. The plan provides for employer contributions to the plan of between 5% and 10% of salary for qualified employees. During 2014 and 2013, ProAssurance also maintained similar plans of acquired entities prior to the plans being merged into the ProAssurance Savings Plan. ProAssurance incurred expense related to savings and retirement plans of $6.0 million, $5.1 million and $4.6 million during the years ended December 31, 2014, 2013 and 2012, respectively.
	ProAssurance also maintains a non-qualified deferred compensation plan (the ProAssurance Plan) that allows participating management employees to defer a portion of their current salary. ProAssurance incurred expense related to the ProAssurance Plan, as well as another plan acquired as part of a business combination, of $0.3 million during the year ended December 31, 2014 and $0.4 million during each of the years ended December 31, 2013 and 2012. ProAssurance deferred compensation liabilities totaled $14.0 million, and $13.1 million at December 31, 2014. and 2013, respectively. The liabilities included amounts due under the ProAssurance Plan and amounts due under individual agreements with current or former employees.

Statutory_Accounting_and_Divid

Statutory Accounting and Dividend Restrictions	12 Months Ended
	Dec. 31, 2014
Statutory Accounting And Dividend Restrictions [Abstract]
Statutory Accounting and Dividend Restrictions	Statutory Accounting and Dividend Restrictions
	ProAssurance’s domestic U.S. insurance subsidiaries are required to file statutory financial statements with state insurance regulatory authorities, prepared based upon statutory accounting practices prescribed or permitted by regulatory authorities. ProAssurance did not use any prescribed or permitted statutory accounting practices that differed from the National Association of Insurance Commissioners' statutory accounting practices at December 31, 2014, 2013 or 2012. Differences between net income prepared in accordance with GAAP and statutory net income are principally due to: (a) policy acquisition and certain software and equipment costs which are deferred under GAAP but expensed for statutory purposes and (b) certain deferred income taxes which are recognized under GAAP but are not recognized for statutory purposes.
	The NAIC specifies risk-based capital requirements for property and casualty insurance providers. At December 31, 2014 actual statutory capital and surplus for each of ProAssurance’s insurance subsidiaries substantially exceeded the regulatory requirements. Net earnings and capital and surplus of ProAssurance’s insurance subsidiaries on a statutory basis are shown in the following table.
	(In millions)
	Statutory Net Earnings			Statutory Capital and Surplus
	2014	2013	2012	2014	2013
	$246	$256	$312	$1,681	$1,642
	At December 31, 2014 $1.9 billion of ProAssurance's consolidated net assets were held at its domestic insurance subsidiaries, of which approximately $230 million are permitted to be paid as dividends over the course of 2015 without prior approval of state insurance regulators. However, the payment of any dividend requires prior notice to the insurance regulator in the state of domicile and the regulator may prevent the dividend if, in its judgment, payment of the dividend would have an adverse effect on the capital and surplus of the insurance subsidiary.

Quarterly_Results_of_Operation

Quarterly Results of Operations (unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Quarterly Results of Operations (unaudited)	Quarterly Results of Operations (unaudited)
	The following is a summary of unaudited quarterly results of operations for 2014 and 2013:
			2014
	(In thousands, except per share data)		1st			2nd			3rd			4th
	Net premiums earned		$	171,730		$	176,303		$	177,028		$	174,670
	Net losses and loss adjustment expenses:
	Current year		137,647			141,126			142,124			124,271
	Prior year		(48,139		)	(42,213		)	(42,902		)	(48,830		)
	Net income		46,731			49,942			34,778			65,114
	Basic earnings per share*		0.76			0.84			0.59			1.13
	Diluted earnings per share*		0.76			0.84			0.59			1.12
			2013
	(In thousands, except per share data)		1st			2nd			3rd			4th
	Net premiums earned		$	134,578		$	130,352		$	133,598		$	129,392
	Net losses and loss adjustment expenses:
	Current year		110,726			109,109			110,987			116,689
	Prior year		(53,100		)	(38,500		)	(49,350		)	(81,799		)
	Net income		112,850			50,451			63,357			70,864
	Basic earnings per share*		1.83			0.82			1.02			1.15
	Diluted earnings per share*		1.82			0.81			1.02			1.14
	*	Quarterly and year-to-date computations of per share amounts are made independently; therefore, the sum of per share amounts for the quarters may not equal per share amounts for the respective year-to-date periods.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events
	In January 2015, ProAssurance drew $100 million against its revolving credit agreement on a secured basis. Refer to Note 10 for further discussion of the terms of the revolving credit agreement.

Schedule_I_Summary_of_Investme

Schedule I - Summary of Investments-Other Than Investments In Related Parties	12 Months Ended
	Dec. 31, 2014
Summary of Investments, Other than Investments in Related Parties [Abstract]
Schedule I - Summary of Investments Other than Investments in Related Parties
	Type of Investment	Recorded		Fair		Amount Which is
		Cost		Value		Presented
		Basis				in the
						Balance Sheet
	(In thousands)
	Fixed Maturities
	Bonds:
	U.S. Government or government agencies and authorities	$	201,736	$	206,075	$	206,075
	States, municipalities and political subdivisions	1,015,555		1,062,615		1,062,615
	Foreign Governments	2,709		2,871		2,871
	Public utilities	80,086		83,668		83,668
	All other corporate bonds	1,307,025		1,330,412		1,330,412
	Certificates of deposit	150		150		150
	Mortgage-backed securities	448,216		459,236		459,236
	Total Fixed Maturities	3,055,477		3,145,027		3,145,027
	Equity Securities, trading
	Common Stocks:
	Public utilities	6,559		7,981		7,981
	Banks, trusts and insurance companies	75,171		79,341		79,341
	Industrial, miscellaneous and all other	201,377		227,160		227,160
	Total Equity Securities, trading	283,107		314,482		314,482
	Other long-term investments	418,939		421,655		418,939
	Short-term investments	131,259		131,259		131,259
	Total Investments	$	3,888,782	$	4,012,423	$	4,009,707

Schedule_II_Condensed_Financia

Schedule II - Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2014
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule II - Condensed Financial Information of Registrant	ProAssurance Corporation – Registrant Only
	Condensed Balance Sheets
		December 31
	(In thousands)	2014			2013
	Assets
	Investment in subsidiaries, at equity	$	2,145,358		$	1,996,721
	Fixed maturities available for sale, at fair value	203,451			86,603
	Equity securities, trading, at fair value	—			12,043
	Short-term investments	42,790			191,991
	Cash and cash equivalents	87,200			37,459
	Restricted cash	—			78,000
	Due from subsidiaries	87,719			12,014
	Other assets	25,736			255,313
	Total Assets	$	2,592,254		$	2,670,144
	Liabilities and Shareholders’ Equity
	Liabilities:
	Other liabilities	$	184,310		$	25,730
	Long-term debt	250,000			250,000
	Total Liabilities	434,310			275,730
	Shareholders’ Equity:
	Common stock	623			621
	Other shareholders’ equity, including unrealized gains (losses) on securities of subsidiaries	2,157,321			2,393,793
	Total Shareholders’ Equity	2,157,944			2,394,414
	Total Liabilities and Shareholders’ Equity	$	2,592,254		$	2,670,144
	ProAssurance Corporation – Registrant Only
	Condensed Statements of Income
		Year Ended December 31
	(In thousands)	2014			2013			2012
	Net investment income	$	3,295		$	5,789		$	5,281
	Equity in earnings (loss) of unconsolidated subsidiaries	—			—			(728		)
	Net realized investment gains (losses)	990			5,334			3,230
	Other income (loss)	660			170			54
		4,945			11,293			7,837
	Expenses:
	Interest expense	14,084			2,747			1,534
	Other expenses	7,083			13,213			8,870
		21,167			15,960			10,404
	Income (loss) before income tax expense (benefit) and equity in net income of consolidated subsidiaries	(16,222		)	(4,667		)	(2,567		)
	Income tax expense (benefit)	(6,728		)	(1,007		)	773
	Income (loss) before equity in net income of consolidated subsidiaries	(9,494		)	(3,660		)	(3,340		)
	Equity in net income of consolidated subsidiaries	206,059			301,183			278,810
	Net income	$	196,565		$	297,523		$	275,470
	Other comprehensive income	$	(1,457	)	$	(85,719	)	$	15,343
	Comprehensive income	$	195,108		$	211,804		$	290,813
	ProAssurance Corporation – Registrant Only
	Condensed Statements of Cash Flow
		Year Ended December 31
	(In thousands)	2014			2013			2012
	Net cash provided (used) by operating activities	$	20,086		$	(24,654	)	$	3,601
	Investing activities
	Purchases of equity securities trading	(310		)	(1,265		)	(364		)
	Proceeds from sale or maturities of:
	Fixed maturities, available for sale	104,844			224,993			150,192
	Equity securities trading	12,813			1,113			616
	Net decrease (increase) in short-term investments	149,202			(187,625		)	58,657
	Dividends from subsidiaries	67,188			239,484			59,369
	Contribution of capital to subsidiaries	(7,000		)	—			(184,330		)
	Deposit made for future acquisition	—			(205,244		)	—
	(Increase) decrease in restricted cash	78,000			(78,000		)	—
	Funds advanced for Syndicate 1729 FAL deposit	(76,553		)	(8,699		)	—
	Funds advanced under Syndicate 1729 credit agreement	(9,107		)	(1,665		)	—
	Other	415			(20		)	(1		)
	Net cash provided (used) by investing activities	319,492			(16,928		)	84,139
	Financing activities
Proceeds from long-term debt	—			250,000			125,000
Principal repayment of debt	—			(125,000		)	(32,992		)
Repurchase of common stock	(222,360		)	(29,089		)	—
Subsidiary payments for common shares and share-based compensation awarded to subsidiary employees	8,301			6,258			7,066
Excess of tax benefit from share-based payment arrangements	1,631			2,128			7,022
Dividends to shareholders	(70,490		)	(46,375		)	(200,118		)
Other	(6,919		)	(8,278		)	(12,259		)
Net cash provided (used) by financing activities	(289,837		)	49,644			(106,281		)
Increase (decrease) in cash and cash equivalents	49,741			8,062			(18,541		)
Cash and cash equivalents, beginning of period	37,459			29,397			47,938
Cash and cash equivalents, end of period	$	87,200		$	37,459		$	29,397
Supplemental disclosure of cash flow information:
Cash paid during the year for income taxes, net of refunds	$	26,061		$	117,107		$	110,278
Cash paid during the year for interest	$	13,408		$	913		$	2,342
Significant non-cash transactions:
Dividends declared and not yet paid	$	167,744		$	18,532		$	—
Securities transferred at fair value as dividends from subsidiaries	$	227,412		$	69,011		$	241,081
Notes to Condensed Financial Statements of Registrant
1. Basis of Presentation
The registrant-only financial statements should be read in conjunction with ProAssurance Corporation’s (PRA Parent) consolidated financial statements. At December 31, 2014 and 2013, PRA Parent’s investment in subsidiaries is stated at the initial consolidation value plus equity in the undistributed earnings of subsidiaries since the date of acquisition.
2. Business Combinations
On January 1, 2014, ProAssurance completed the acquisition of Eastern Insurance Holdings, Inc. (Eastern) (NASDAQ: EIHI) by purchasing 100% of its outstanding common shares. ProAssurance acquired Eastern for cash of $205 million. ProAssurance transferred all of the cash required to complete the transaction to a third-party agent for the benefit of Eastern eligible shareholders on December 27, 2013; the deposit was classified as a part of Other Assets at December 31, 2013.
On January 1, 2013, ProAssurance, through a wholly owned subsidiary, completed the acquisition of Medmarc Mutual Insurance Company, now Medmarc Casualty Insurance Company (Medmarc), through a sponsored demutualization. A gain recognized on the acquisition is included in the December 31, 2013 Consolidated Statements of Income and Comprehensive Income.
Additional information regarding business combinations is provided in Note 2 of the Notes to Consolidated Financial Statements.
3. Other Assets
At December 31, 2013 Other assets was principally comprised of a $205 million deposit made related to the Eastern transaction, discussed in Note 2 above.
4. Long-term Debt
Outstanding long-term debt, as of December 31, 2014 and 2013, consisted of the following:
(In thousands)	2014			2013
Senior notes due 2023, unsecured, interest at 5.3% annually	$	250,000		$	250,000
Revolving credit agreement, outstanding borrowings not permitted to exceed $200 million aggregately, expires in 2016	—			—
	$	250,000		$	250,000
See Note 10 of the Notes to Consolidated Financial Statements included herein for a detailed description of the terms of the Senior Notes due 2023 and the Revolving Credit Agreement.
5. Related Party Transactions
PRA Parent received dividends from its subsidiaries of $294.6 million, $308.5 million and $300.5 million during the years ended December 31, 2014, 2013 and 2012, respectively. PRA Parent contributed capital of $7.0 million, and $184.3 million to its subsidiaries during the years ended December 31, 2014 and 2012, respectively. No capital was contributed to subsidiaries during the year ended December 31, 2013. Capital contributed in 2012 was primarily for the purpose of funding the Medmarc acquisition. Additionally, advances of $76.6 million and $8.7 million were made in 2014 and 2013, respectively, to a subsidiary that is a Corporate Member at Lloyds. The subsidiary used the advances to provide capital at Lloyd's, also known as FAL, in support of Syndicate 1729.
6. Income Taxes
Under terms of PRA Parent’s tax sharing agreement with its subsidiaries, income tax provisions for individual companies are allocated on a separate company basis.
7. Commitment to Syndicate 1729
ProAssurance has provided a revolving credit agreement (the "Syndicate Credit Agreement") to Premium Trust Fund of Syndicate 1729 which will provide operating funds for the Syndicate of up to £10 million (approximately $16 million at December 31, 2014). At December 31, 2014, £6.6 million ($11.0 million) had been drawn under the Syndicate Credit Agreement. See Note 9 of the Notes to Consolidated Financial Statements for additional information regarding the Syndicate Credit Agreement.

Schedule_III_Supplementary_Ins

Schedule III - Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2014
Supplementary Insurance Information [Abstract]
Schedule III - Supplementary Insurance Information
	(In thousands)	2014			2013			2012
	Net premiums earned
	Specialty P&C	$	492,733		$	527,919		$	550,664
	Workers' Compensation	194,540			—			—
	Lloyd's Syndicate	12,458			—			—
	Consolidated	699,731			527,919			550,664
	Net investment income (1)
	Lloyd's Syndicate	410			—			—
	Corporate	125,147			129,265			136,094
	Consolidated	125,557			129,265			136,094
	Losses and loss adjustment expenses incurred related to current year, net of reinsurance
	Specialty P&C	408,987			447,510			451,951
	Workers' Compensation	127,743			—			—
	Lloyd's Syndicate	8,438			—			—
	Consolidated	545,168			447,510			451,951
	Losses and loss adjustment expenses incurred related to prior year, net of reinsurance
	Specialty P&C	(180,788		)	(222,749		)	(272,038		)
	Workers' Compensation	(1,296		)	—			—
	Lloyd's Syndicate	—			—			—
	Consolidated	(182,084		)	(222,749		)	(272,038		)
	Paid losses and loss adjustment expenses, net of reinsurance
	Specialty P&C	389,458			388,813			339,142
	Workers' Compensation	117,775			—			—
	Lloyd's Syndicate	404			—			—
	Consolidated	507,637			388,813			339,142
	Amortization of deferred policy acquisition costs
	Specialty P&C	55,105			53,207			54,887
	Workers' Compensation	10,307			—			—
	Lloyd's Syndicate	3,165			—			—
	Consolidated	68,577			53,207			54,887
	Other underwriting, policy acquisition and operating expenses
	Specialty P&C	78,027			78,869			70,405
	Workers' Compensation	50,050			—			—
	Lloyd's Syndicate	6,370			—			—
	Corporate	8,768			15,748			10,389
	Consolidated (2)	142,734			94,610			80,744
	Net premiums written
	Specialty P&C	467,046			525,182			528,298
	Workers' Compensation	202,697			—			—
	Lloyd's Syndicate	32,106			—			—
	Consolidated	701,849			525,182			528,298
	Deferred policy acquisition costs (1)	38,790			28,207			23,179
	Reserve for losses and loss adjustment expenses (1)	2,058,266			2,072,822			2,054,994
	Unearned premiums (1)	345,828			255,463			233,861
	(1) Assets are not allocated to segments because investments and assets are not managed at the segment level, with the exception
	of the FAL investments held at our Lloyd's Syndicate segment.
	(2) Includes Inter-segment eliminations.

Schedule_IV_Reinsurance

Schedule IV - Reinsurance	12 Months Ended
	Dec. 31, 2014
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Schedule IV - Reinsurance
	(In thousands)		2014			2013			2012
	Property and Liability *
	Premiums earned		$	755,623		$	568,629		$	558,200
	Premiums ceded		(68,879		)	(41,514		)	(7,652		)
	Premiums assumed		12,987			804			116
	Net premiums earned		$	699,731		$	527,919		$	550,664
	Percentage of amount assumed to net		1.86		%	0.15		%	0.02		%
	*	All of ProAssurance’s premiums are related to property and liability coverages.

Accounting_Policies_Policies

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Organization and Nature of Business	Organization and Nature of Business
	ProAssurance Corporation (ProAssurance, PRA or the Company), a Delaware corporation, is an insurance holding company primarily for wholly owned specialty property and casualty insurance entities including an entity that is the majority capital provider to Syndicate 1729 at Lloyd's of London. Risks insured are primarily liability risks located within the United States of America (U.S.). As described in more detail in Note 15, ProAssurance operates in four reportable segments: Specialty Property and Casualty (Specialty P&C), Workers' Compensation, Lloyd's Syndicate, and Corporate.
Principles of Consolidation	Principles of Consolidation
	The accompanying consolidated financial statements include the accounts of ProAssurance Corporation and its wholly-owned subsidiaries. Investments in entities where ProAssurance holds a greater than minor interest but does not hold a controlling interest are accounted for using the equity method. All significant intercompany accounts and transactions are eliminated in consolidation. ProAssurance subsidiaries located in the United Kingdom (U.K.) are reported on a quarter delay due to timing issues regarding the availability of information, except there is no delay related to subsidiary investments managed in the U.S. as that information is available on an earlier schedule.
Basis of Presentation	Basis of Presentation
	The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenues and expenses, and disclosures related to these amounts at the date of the financial statements. Actual results could differ from those estimates.
Reclassifications	Reclassifications
	On January 1, 2014, ProAssurance began reporting unearned ceding commissions as an offset to deferred policy acquisition costs (DPAC) on the Consolidated Balance Sheet, and the December 31, 2013 Consolidated Balance Sheet has been conformed to the current presentation. Previously, unearned ceding commissions ($0.8 million at December 31, 2013) were reported in Unearned premiums. Also, ceding commission income earned for the years ended December 31, 2014, 2013 and 2012 has been reported as an offset to DPAC amortization (see Note 7) which lowered DPAC amortization as previously reported for the years ended December 31, 2013 and 2012 by $5.9 million and $2.1 million, respectively. Total underwriting, policy acquisition and operating expense for the years ended December 31, 2013 and 2012 was not affected by the change in presentation.
Stock Split	Stock Split
	In 2012, the Board of Directors of ProAssurance Corporation (the Board) declared a two-for-one split of ProAssurance common shares which was effected December 27, 2012 in the form of a stock dividend. All share and per share information provided in this report reflects the effect of the split for all periods presented.
Recognition of Revenues	Recognition of Revenues
	Insurance premiums are recognized as revenues pro rata over the terms of the policies, which are principally one year in duration.
	At December 31, 2014 and 2013 ProAssurance had established allowances for credit losses related to premium and agency receivables as shown in the following table.
	(in thousands)		Premium			Agency
			Receivables			Receivables
	Allowance for credit losses:
	Balance at December 31, 2012		$	1,000		$	286
	Estimated credit losses		236			—
	Account write offs, net of recoveries		(246		)	(236		)
	Balance at December 31, 2013		990			50
	Estimated credit losses		299			—
	Account write offs, net of recoveries		(299		)	—
	Allowance acquired from acquisition		225			—
	Balance at December 31, 2014		$	1,215		$	50
	Earned But Unbilled Premiums (EBUB)
	Workers’ compensation premiums are determined based upon the payroll of the insured, the applicable premium rates and, where applicable, an experience based modification factor. An audit of the policyholders’ records is conducted after policy expiration to make a final determination of applicable premiums. Audit premium due from or due to a policyholder as a result of an audit is reflected in net premiums earned when billed. ProAssurance tracks, by policy, the amount of additional premium billed in final audit invoices as a percentage of payroll exposure and uses this information to estimate the probable additional amount that it has earned, but not yet billed, as of the balance sheet date. Changes to the EBUB estimate are included in Net premiums earned in the period recognized. As of December 31, 2014, ProAssurance carried earned but unbilled premiums of $3.4 million as a part of Premiums receivable.
Losses and Loss Adjustment Expenses	Losses and Loss Adjustment Expenses
	ProAssurance establishes its reserve for losses and loss adjustment expenses ("reserve for losses" or "reserve") based on estimates of the future amounts necessary to pay claims and expenses associated with the investigation and settlement of claims. The reserve for losses is determined on the basis of individual claims and payments thereon as well as actuarially determined estimates of future losses based on past loss experience, available industry data and projections as to future claims frequency, severity, inflationary trends, judicial trends, legislative changes and settlement patterns.
	Management establishes the reserve for losses after taking into consideration a variety of factors including the conclusions reached by internal actuaries, premium rates, claims frequency, historical paid and incurred loss development trends, the effect of inflation, general economic trends, the legal and political environment, and the reports received from consulting actuaries. Internal actuaries perform an in-depth review of the reserve for losses at least semi-annually using the loss and exposure data of ProAssurance subsidiaries. Management engages consulting actuaries to review subsidiary loss and exposure data and provide reports to Management regarding the adequacy of reserves.
	Estimating casualty insurance reserves, and particularly long-tailed insurance reserves, is a complex process. Long-tailed insurance is characterized by the extended period of time between collecting the premium for insuring a risk and the ultimate payment of losses. For a high proportion of the risks insured or reinsured by ProAssurance the period of time required to resolve a claim is often five years or more, and claims may be subject to litigation. Estimating losses for these long-tailed claims requires ProAssurance to make and revise judgments and assessments regarding multiple uncertainties over an extended period of time. As a result, reserve estimates may vary significantly from the eventual outcome. Reserve estimates and the assumptions on which these estimates are predicated are regularly reviewed and updated as new information becomes available. Any adjustments necessary are reflected in then current operations. Due to the size of ProAssurance’s reserve for losses, even a small percentage adjustment to these estimates could have a material effect on earnings in the period in which the adjustment is made, as was the case in 2014, 2013 and 2012.
	The effect of adjustments made to reinsured losses is mitigated by the corresponding adjustment that is made to reinsurance recoveries. Thus, in any given year, ProAssurance may make significant adjustments to gross losses that have little effect on its net losses.
Reinsurance Receivables	Reinsurance Receivables
	ProAssurance enters into reinsurance agreements whereby other insurance entities agree to assume a portion of the risk associated with certain policies issued by ProAssurance. In return, ProAssurance agrees to pay a premium to the reinsurer. ProAssurance purchases reinsurance to provide for greater diversification of business and to allow management to control exposure to potential losses arising from large risks.
	Receivable from reinsurers on paid losses and loss adjustment expenses is the estimated amount of losses already paid that will be recoverable from reinsurers. Receivable from reinsurers on unpaid losses and loss adjustment expenses is the estimated amount of future loss payments that will be recoverable from reinsurers. Reinsurance recoveries are the portion of losses incurred during the period that are estimated to be allocable to reinsurers. Premiums ceded are the estimated premiums that will be due to reinsurers with respect to premiums earned and losses incurred during the period.
	These estimates are based upon management’s estimates of ultimate losses and the portion of those losses that are allocable to reinsurers under the terms of the related reinsurance agreements. Given the uncertainty of the ultimate amounts of losses, these estimates may vary significantly from the eventual outcome. Management regularly reviews these estimates and any adjustments necessary are reflected in the period in which the estimate is changed. Due to the size of the receivable from reinsurers, even a small adjustment to the estimates could have a material effect on ProAssurance’s results of operations for the period in which the change is made.
	Reinsurance contracts do not relieve ProAssurance from its obligations to policyholders. ProAssurance continually monitors its reinsurers to minimize its exposure to significant losses from reinsurer insolvencies. Any amount determined to be uncollectible is written off in the period in which the uncollectible amount is identified.
Investments	Investments
	Fair Values
	Fair values of investment securities are primarily provided by independent pricing services. The pricing services provide an exchange traded price, if available, or provide an estimated price determined using multiple observable inputs, including exchange traded prices for similar assets. Management reviews valuations of securities obtained from the pricing services for accuracy based upon the specifics of the security, including class, maturity, credit rating, durations, collateral, and comparable markets for similar securities. Multiple observable inputs are not available for certain of our investments, including municipal bonds and corporate debt not actively traded, and investments in limited partnerships/limited liability companies (LPs/LLCs). Management values these municipal bonds and corporate debt either using a single non-binding broker quote or pricing models that utilize market based assumptions that have limited observable inputs. Management values certain investments in LPs/LLCs based on the net asset value (NAV) of the interest held, as provided by the fund.
	Fixed Maturities and Equity Securities
	Fixed maturities and equity securities are considered as either available-for-sale or trading securities.
	Available-for-sale securities are carried at fair value, determined as described above, and unrealized gains and losses on such available-for-sale securities are included, net of related tax effects, in Shareholders’ Equity as a component of Accumulated Other Comprehensive Income (Loss).
	Investment income includes amortization of premium and accretion of discount related to available-for-sale debt securities acquired at other than par value. Debt securities and mandatorily redeemable preferred stock with maturities beyond one year when purchased are classified as fixed maturities.
	Trading portfolio securities are carried at fair value, determined as described above, with the holding gains and losses included in realized investment gains and losses in the current period.
	Short-term Investments
	Short-term investments, which have a maturity at purchase of one year or less, are primarily comprised of investments in U.S. Treasury obligations and commercial paper. All balances are reported at amortized cost, which approximates fair value.
	Other Investments
	Investments in LPs/LLCs where ProAssurance has virtually no influence over the operating and financial policies of an investee are accounted for using the cost method. Under the cost method, investments are valued at cost, with investment income recognized when received.
	Investments in convertible bond 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. Interest on convertible bond securities is recorded on an accrual basis based on contractual interest rates and is included in Net investment income.
	Investment in Unconsolidated Subsidiaries
	Investments in LPs/LLCs where ProAssurance is deemed to have influence because it holds a greater than a minor interest are accounted for using the equity method. Under the equity method, the recorded basis of the investment is adjusted each period for the investor’s pro rata share of the investee’s income or loss. Investments in unconsolidated subsidiaries include tax credit partnerships accounted for using the equity method, whereby ProAssurance’s proportionate share of income or loss is included in investment income. Tax credits received from the partnerships are recognized in the period received as a reduction to current tax expenses.
	Business Owned Life Insurance (BOLI)
	ProAssurance owns life insurance contracts on certain management employees. The life insurance contracts are carried at their current cash surrender value. Changes in the cash surrender value are included in income in the current period as investment income. Death proceeds from the contracts are recorded when the proceeds become payable under the policy terms.
	Realized Gains and Losses
	Realized investment gains and losses are recognized on the specific identification basis.
	Other-than-temporary Impairments
	ProAssurance evaluates its available-for-sale investment securities on at least a quarterly basis for the purpose of determining whether declines in fair value below recorded cost basis represent other-than-temporary declines. The assessment of whether the amortized cost basis of debt securities, particularly asset-backed debt securities, is expected to be recovered requires management to make assumptions regarding various matters affecting cash flows to be received in the future. The choice of assumptions is subjective and requires the use of judgment; actual credit losses experienced in future periods may differ from management’s estimates of those credit losses.
	If there is intent to sell the security or if it is more likely than not that the security will be required to be sold before full recovery of its amortized cost basis, ProAssurance considers a decline in fair value to be an other-than-temporary impairment. Otherwise, ProAssurance considers the following factors in determining whether an investment’s decline is other-than-temporary:
	For equity securities:
	•	the length of time for which the fair value of the investment has been less than its recorded basis;
	•	the financial condition and near-term prospects of the issuer underlying the investment, taking into consideration the economic prospects of the issuer’s industry and geographical region, to the extent that information is publicly available; and
	•	the historical and implied volatility of the fair value of the security.
	For debt securities, an evaluation is made as to whether the decline in fair value is due to credit loss, which is defined as the excess of the current amortized cost basis of the security over the present value of expected future cash flows. Methodologies used to estimate the present value of expected cash flows to determine if a decline is due to a credit loss are:
	•	For non-structured fixed maturities (U.S. Treasury securities, obligations of U.S. Government and government agencies and authorities, obligations of states, municipalities and political subdivisions, and corporate debt) the estimate of expected cash flows is determined by projecting a recovery value and a recovery time frame and assessing whether further principal and interest will be received. ProAssurance considers various factors in projecting recovery values and recovery time frames, including the following:
	•	third party research and credit rating reports;
	•	the current credit standing of the issuer, including credit rating downgrades, whether before or after the balance sheet date;
	•	internal assessments and the assessments of external portfolio managers regarding specific circumstances surrounding an investment, which indicate the investment is more or less likely to recover its amortized cost than other investments with a similar structure;
	•	failure of the issuer of the security to make scheduled interest or principal payments;
	•	For structured securities (primarily asset-backed securities), ProAssurance estimates the present value of the security’s cash flows using the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment or changes in expected cash flows). ProAssurance considers the most recently available six month averages of the levels of delinquencies, defaults, severities, and prepayments for the collateral (loans) underlying the securitization or, if historical data is not available, sector based assumptions, to estimate expected future cash flows of these securities.
	Investments in tax credit partnerships are evaluated for OTTI by considering both qualitative and quantitative factors which include: whether cash flows currently expected from the investment, primarily tax benefits, equal or exceed the carrying value of the investment, whether currently expected cash flows are less than those expected at the time the investment was acquired, and ProAssurance's ability and intent to hold the investment until the recovery of its carrying value.
	Investments in LPs/LLCs other than tax credit partnerships are evaluated for impairment by comparing ProAssurance’s carrying value to net asset value of ProAssurance’s interest as reported by the LP/LLC. Additionally, Management considers the performance of the LP/LLC relative to the market and its stated objectives, cash flows expected from the interest, and the audited financial statements of the LP/LLC, if available.
	ProAssurance recognizes other-than-temporary impairments, including impairments of debt securities due to credit loss, in earnings as a part of net realized investment gains (losses). In subsequent periods, any measurement of gain or loss or impairment is based on the revised amortized basis of the security. Declines in fair value, including non-credit impairments of debt securities, not considered to be other-than-temporary are recognized in other comprehensive income.
	Asset-backed securities that have been impaired due to credit or are below investment grade quality are accounted for under the effective yield method. Under the effective yield method estimates of cash flows expected over the life of asset-backed securities are then used to recognize income on the investment balance for subsequent accounting periods.
Foreign Currency	Foreign Currency
	The functional currency of all ProAssurance foreign subsidiaries is the U.S. Dollar
Cash and Cash Equivalents	Cash and Cash Equivalents
	For purposes of the consolidated balance sheets and statements of cash flows, ProAssurance considers all demand deposits and overnight investments to be cash equivalents.
Restricted Cash	Restricted Cash
	Restricted cash represents cash balances which are not available for immediate or general use. At December 31, 2013 ProAssurance's Restricted cash was comprised entirely of a deposit collateralizing a standby letter of credit entered into as partial funding at Lloyd's for Syndicate 1729.
Deferred Policy Acquisition Costs (DPAC); Ceding Commission Income	Deferred Policy Acquisition Costs; Ceding Commission Income
	Costs that vary with and are directly related to the successful production of new and renewal premiums (primarily premium taxes, commissions and underwriting salaries) are deferred to the extent they are recoverable against unearned premiums and are amortized as related premiums are earned.
Income Taxes/Deferred Taxes	Income Taxes/Deferred Taxes
	ProAssurance files a consolidated federal income tax return. Tax-related interest and penalties are recognized as components of tax expense.
	ProAssurance evaluates tax positions taken on tax returns and recognizes positions in the financial statements when it is more likely than not that the position will be sustained upon resolution with a taxing authority. If recognized, the benefit is measured as the largest amount of benefit that has a greater than fifty percent probability of being realized. Uncertain tax positions are reviewed each period by considering changes in facts and circumstances, such as changes in tax law, interactions with taxing authorities and developments in case law, and adjustments are made as considered necessary. Adjustments to unrecognized tax benefits may affect income tax expense and the settlement of uncertain tax positions may require the use of cash.
	Deferred federal income taxes arise from the recognition of temporary differences between the basis of assets and liabilities determined for financial reporting purposes and the basis determined for income tax purposes. ProAssurance’s temporary differences principally relate to loss reserves, unearned premium, deferred policy acquisition costs, unrealized investment gains (losses), basis differentials for investments, compensation accruals, and intangibles. Deferred tax assets and liabilities are measured using the enacted tax rates expected to be in effect when such benefits are realized. ProAssurance reviews its deferred tax assets quarterly for impairment. If management determines that it is more likely than not that some or all of a deferred tax asset will not be realized, a valuation allowance is recorded to reduce the carrying value of the asset. In assessing the need for a valuation allowance, management is required to make certain judgments and assumptions about the future operations of ProAssurance based on historical experience and information as of the measurement date regarding reversal of existing temporary differences, carryback capacity, future taxable income, including its capital and operating characteristics, and tax planning strategies.
	Changes in tax laws and rates could also affect recorded deferred tax assets and liabilities in the future. Management is not aware of any such changes that would have a material effect on the Company’s results of operations, cash flows or financial position.
Real Estate	Real Estate
	Real Estate balances are reported at cost or, for properties acquired in business combinations, estimated fair value on the date of acquisition, less accumulated depreciation. Real estate principally consists of properties in use as corporate offices. Depreciation is computed over the estimated useful lives of the related property using the straight-line method. Excess office capacity is leased or made available for lease; rental income is included in other income and real estate expenses are included in underwriting, policy acquisition and operating expenses
Intangible Assets	Intangible Assets
	Intangible assets with definite lives are amortized over the estimated useful life of the asset. Amortizable intangible assets primarily consist of agency and policyholder relationships. Intangible assets with an indefinite life, primarily state licenses, are not amortized. Both amortizable and non-amortizable intangible assets increased during 2014 due to intangible assets purchased in the Eastern acquisition, see Note 2. Intangible assets are evaluated for impairment on an annual basis.
Goodwill	Goodwill
	Goodwill is recognized in conjunction with acquisitions as the excess of the purchase consideration for the acquisition over the fair value of identifiable assets acquired and liabilities assumed. The fair value of identifiable assets and liabilities, and thus goodwill, is subject to redetermination within a measurement period of up to one year following completion of an acquisition.
	ProAssurance evaluates the carrying value of goodwill at the segment (or reporting unit) level annually as of October 1st. If, at any time during the year, events occur or circumstances change that would more likely than not reduce the fair value below the carrying value, an additional evaluation of goodwill is made.
	The goodwill impairment assessment requires evaluating qualitative factors or performing a quantitative assessment to determine if a reporting unit’s carrying value is likely to exceed its fair value. ProAssurance elected to evaluate goodwill for each of its reporting units using qualitative factors to determine whether it was more likely than not that the fair value of a reporting unit was less than its carrying amount. In applying the qualitative approach, Management considered macroeconomic factors, such as industry and market conditions, as well as reporting-unit-specific events, actual financial performance versus expectations, and management’s future business expectations. For recently acquired reporting units with material goodwill, consideration was given to the fact that the business had been recently acquired in an orderly transaction between market participants, and that the purchase price therefore represented fair value at acquisition. A significant amount of judgment is required in performing the goodwill impairment analysis. As of October 1, 2014, the most recent evaluation date, Management concluded that the fair value of each ProAssurance reporting unit exceeded the carrying value of the reporting unit, and deemed it unnecessary to perform further testing for impairment.
Treasury Shares	Treasury Stock
	Treasury shares are reported at cost, and are reflected on the Consolidated Balance Sheets as an unallocated reduction of total equity.
Share-Based Payments	Share-Based Payments
	Compensation cost for share-based payments is measured based on the grant-date fair value of the award, recognized over the period in which the employee is required to provide service in exchange for the award. Excess tax benefits (tax deductions realized in excess of the compensation costs recognized for the exercise of the awards, multiplied by the incremental tax rate) are reported as financing cash inflows.
Subsequent Events	Subsequent Events
	ProAssurance evaluates events that occurred subsequent to December 31, 2014, for recognition or disclosure in its Consolidated Financial Statements.
Accounting Changes Adopted and Not Yet Adopted	Accounting Changes Adopted
	Obligations Resulting from Joint and Several Liability Arrangements
	Effective for fiscal years beginning after December 15, 2013, the Financial Accounting Standards Board (FASB) revised guidance related to obligations resulting from joint and several liability arrangements. The new guidance requires an entity to recognize, measure and disclose obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date, except for obligations already addressed within existing GAAP guidance, with retrospective application required for such arrangements existing at the beginning of the fiscal year of adoption. ProAssurance adopted the guidance on January 1, 2014. Adoption of this guidance had no effect on ProAssurance's results of operations or financial position.
	Presentation of Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists
	Effective for fiscal years beginning after December 15, 2013, the FASB issued guidance related to the financial statement presentation of unrecognized tax benefits. The new guidance requires an entity to present unrecognized tax benefits as a reduction to a deferred tax asset resulting from a net operating loss carryforward, a similar tax loss, or tax credit carryforward except in circumstances where the relevant taxing authority does not permit offset or does not require offset and the entity does not intend to use the deferred tax asset for offset. The guidance requires prospective application for all unrecognized tax benefits that exist as of the effective date, but may be applied retrospectively. ProAssurance adopted the guidance prospectively on January 1, 2014. Adoption of this guidance had no material effect on ProAssurance's results of operations or financial position.
	Equity Method and Joint Ventures-Accounting for Investments in Qualified Affordable Housing Projects
	Effective for fiscal years beginning after December 15, 2014, the FASB issued guidance which, if certain criteria is met, permits but does not require reporting entities to begin using a new accounting method, the proportional amortization method, for investments in qualified affordable housing projects. The guidance also includes new disclosure requirements around the nature of investments in qualified affordable housing projects and their effect on financial position and results of operations. Under the proportional amortization method the investments in such projects are amortized in proportion to the tax benefits received, and investment performance is recognized as a component of income tax expense (benefit) rather than as a component of investment income. The tax credit partnership investments held by ProAssurance are primarily investments in qualified affordable housing projects. ProAssurance has adopted the new guidance as of December 31, 2014, but has elected to continue to account for these investments using the equity method of accounting. Adoption of this guidance had no material effect on ProAssurance’s results of operations or financial position as it affected disclosures only.
	Determining Whether Hybrid Financial Instruments Issued as a Share is More Akin to Debt or to Equity
	Effective for fiscal years beginning after December 15, 2015, early adoption permitted, the FASB issued guidance that clarifies current U.S. GAAP regarding the evaluation of the economic characteristics and risks of a host contract in a hybrid financial instrument that is issued in the form of a share. ProAssurance adopted the guidance as of December 31, 2014. Adoption of this guidance had no effect on ProAssurance’s results of operations or financial position.
	Business Combinations: Pushdown Accounting
	On November 18, 2014, the FASB issued immediately effective guidance on whether and at what threshold an acquired entity can apply pushdown accounting in its separate financial statements. ProAssurance has adopted this guidance as of its effective date. Adoption of this guidance had no effect on ProAssurance’s results of operations or financial position.
	Income Statement Presentation of Extraordinary Items
	Effective for fiscal years beginning after December 15, 2015, early adoption permitted, the FASB issued guidance that eliminates from U.S. GAAP the concept of extraordinary items and the related presentation requirements. Under the new guidance, the effect of each event or transaction that is unusual in nature or occurs infrequently, or both, is to be presented as a separate component of income from continuing operations or, alternatively, disclosed in notes to the financial statements. ProAssurance adopted the guidance as of January 1, 2014. Adoption of this guidance had no effect on ProAssurance’s results of operations or financial position.
	Accounting Changes Not Yet Adopted
	Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity
	Effective for fiscal years beginning after December 15, 2014, the FASB issued guidance which changes the requirements for reporting discontinued operations. Under the new guidance, reporting entities are required to report disposals of business components only if the disposal represents a strategic shift in the entity’s operations that will have a major effect on the entity’s operations and financial results. The new guidance expands disclosure requirements for reported discontinued operations and requires disclosure of pre-tax profit or loss attributable to significant disposals that are not reported as discontinued operations. ProAssurance plans to adopt the guidance beginning January 1, 2015. Adoption of the guidance is expected to have no effect on ProAssurance’s results of operations or financial position.
	Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period
	Effective for fiscal years beginning after December 15, 2015, the FASB issued guidance for share-based payments in which the terms of the award provide that a performance target can be achieved after completion of the requisite service period. The new guidance provides that compensation cost for such awards should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered. ProAssurance plans to adopt the guidance beginning January 1, 2016. Adoption of the guidance is expected to have no effect on ProAssurance’s results of operations or financial position as ProAssurance has no awards with performance targets extending beyond the requisite service period.
	Revenue from Contracts with Customers
	Effective for fiscal years beginning after December 15, 2016, the FASB issued guidance related to revenue from contracts with customers. The core principle of the new guidance is that revenue should be 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, 2017. 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 expected to have no material effect on ProAssurance’s results of operations or financial position.
	Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern
	Effective for fiscal years ending after December 15, 2016 and interim periods beginning after December 15, 2016, the FASB issued guidance that establishes principles and definitions related to management's evaluation of whether there is substantial doubt about the organization's ability to continue as a going concern. For each interim and annual reporting period, the new guidance requires management to evaluate the organization's ability to meet its obligations as they are due within one year of the date the financial statements are issued and requires disclosure when there is substantial doubt regarding the organization's ability to continue as a going concern. ProAssurance plans to adopt the guidance on its effective date. Adoption is expected to have no effect on ProAssurance’s results of operations or financial position.

Accounting_Policies_Tables

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of allowances for credit losses related to premium and agency receivables	At December 31, 2014 and 2013 ProAssurance had established allowances for credit losses related to premium and agency receivables as shown in the following table.
	(in thousands)		Premium				Agency
			Receivables				Receivables
	Allowance for credit losses:
	Balance at December 31, 2012		$	1,000			$	286
	Estimated credit losses		236				—
	Account write offs, net of recoveries		(246		)		(236		)
	Balance at December 31, 2013		990				50
	Estimated credit losses		299				—
	Account write offs, net of recoveries		(299		)		—
	Allowance acquired from acquisition		225				—
	Balance at December 31, 2014		$	1,215			$	50
Schedule of Intangible Assets Excluding Goodwill	Information about ProAssurance's intangible assets is shown in the following table.
		Gross Carrying Value								Accumulated Amortization				Amortization Expense
		31-Dec								31-Dec				Year Ended December 31
	(In millions)	2014				2013				2014		2013		2014		2013		2012
	Intangible Assets
	Non-amortizable	$	25.8			$	16.8
	Amortizable	96.2				51.7				$	21.2	$	16.5	$	10.3	$	5.3	$	4.5
	Total Intangible Assets	$	122			$	68.5
Other Liabilities	Other liabilities at December 31, 2014 and 2013 consisted of the following:
	(In millions)		2014				2013
	Unpaid dividends		$	167.7			$	18.5
	Segregated portfolio cell (SPC) dividends payable		15.8				—
	All other		137.4				124.6
	Total other liabilities		$	320.9			$	143.1

Business_Combinations_Tables

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Purchase Price Allocation	The purchase consideration for both the acquisitions of Eastern and Medmarc was allocated to the assets acquired and liabilities assumed based on their estimated fair values on the acquisition dates, as shown in the table below. For the Eastern acquisition, goodwill of $49.6 million was recognized equal to the excess of the purchase price over the net fair value of identifiable assets acquired and liabilities assumed. Factors contributing to the recognition of goodwill include strategic and synergistic benefits that are expected to be realized as a result of the acquisition. These benefits include insurance market diversification, expanded access to alternative markets, and opportunities to reach additional insureds in the healthcare market by being a single source provider of a suite of insurance products. None of the goodwill is expected to be tax deductible.
	For the Medmarc acquisition, the purchase consideration was less than the estimated fair value of the net assets acquired resulting in a gain on the acquisition of $32.3 million. ProAssurance believes it was able to acquire Medmarc for less than the fair value of its net assets due to Medmarc's declining premium base and its small capital position relative to other insurers in the medical technology and life sciences products liability insurance market.
	(In thousands)		Eastern				Medmarc
	Fixed maturities, available for sale		$	107,131			$	269,529
	Equity securities, trading		65,945				30,976
	Cash and short-term investments		58,944				24,008
	Other investments		42,133				5,340
	Premiums receivable, net		71,989				2,986
	Receivable from reinsurers on paid and unpaid losses and LAE		18,942				73,107
	Intangible assets		59,000				3,630
	Deferred policy acquisition costs (see discussion below)		10,593				—
	Other assets		19,225				14,614
	Reserve for losses and loss adjustment expenses		(153,191		)		(201,072		)
	Unearned premiums		(80,268		)		(16,937		)
	Ceded balances payable		(9,507		)		—
	Segregated portfolio cells dividends payable		(14,430		)		—
	Deferred tax liabilities, net		(12,835		)		(4,934		)
	Other liabilities		(28,038		)		(15,233		)
	Fair value of net assets acquired		$	155,633			$	186,014
	Goodwill		49,610				—
	Gain on acquisition		—				(32,314		)
	Total purchase consideration		$	205,243			$	153,700
Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination	Intangible assets acquired from Eastern and Medmarc included the following:
		Eastern					Medmarc
	(In millions)	Estimated Fair Value on Acquisition Date		Estimated			Estimated Fair Value on Acquisition Date		Estimated
				Useful Life					Useful Life
	Agency relationships	$27.00		15			$—		—
	Policyholder relationships	8		15			—		—
	Trade names	8		15			—		—
	Non-compete agreements	7		3			1.1		2		-1
	Total intangibles subject to amortization	$50.00		13	-2		$1.10		2		-2
	Insurance license agreements	$9.00		Indefinite			$2.50		Indefinite
	(1) Medmarc non-compete agreements were fully amortized as of December 31, 2014.
	(2) Reflects the weighted average estimated useful life of acquired intangible assets that are subject to amortization.
ProAssurance Consolidated results	The following table provides Pro Forma Consolidated Results for the years ended December 31, 2014, 2013 and 2012 as if the Eastern transaction had occurred on January 1, 2013 and the Medmarc transaction had occurred on January 1, 2012. ProAssurance Actual Consolidated Results have been adjusted by the following, net of related tax effects, to reflect the Pro Forma Consolidated Results below.
	•	For the year ended December 31, 2013, ProAssurance 2013 Actual Consolidated Results, which did not include Eastern, have been adjusted to include Eastern's 2013 operating results. ProAssurance Actual Consolidated Results for the year ended December 31, 2014 included Eastern's operating results (Revenue of $202.2 million and Net income of $9.1 million).
	•	For the year ended December 31, 2012, ProAssurance 2012 Actual Consolidated Results, which did not include Medmarc, have been adjusted to include Medmarc's 2012 operating results. ProAssurance Actual Consolidated Results for the years ended December 31, 2014 and 2013 included Medmarc's operating results (Revenue of $41.4 million and $46.5 million, respectively, and Net Income of $8.1 million and $15.7 million, respectively).
	•	Certain costs included in ProAssurance Actual Consolidated Results for the years ended December 31, 2014 and 2013 have been reported in the Pro Forma Consolidated Results as if the costs had been incurred for the years ended December 31, 2013 and 2012, respectively. Such costs include direct transaction costs and certain compensation costs directly related to the integration of Eastern and Medmarc operations.
	•	Prior to the acquisition date, Medmarc reported on a statutory basis and expensed policy acquisition costs associated with successful contracts as incurred. After the acquisition date, in accordance with GAAP, Medmarc policy acquisition costs associated with successful contracts were capitalized and amortized to expense as the related premium revenues were earned, but no amortization was recognized for Medmarc policies written prior to the acquisition date. The Pro Forma Consolidated Results for both 2013 and 2012 have been adjusted to reflect policy acquisition costs as if Medmarc had followed GAAP guidance for these costs in pre-acquisition periods.
	•	Net income for the years ended December 31, 2013 and 2012, respectively, was reduced to reflect amortization of intangible assets and debt security premiums and discounts recorded as a part of the Eastern and Medmarc purchase price allocations.
	•	The non-taxable gain on the Medmarc acquisition of $32.3 million that was included in ProAssurance Actual Consolidated Results for the year ended December 31, 2013 has been reported in the Pro Forma Consolidated Results as being recognized during the year ended December 31, 2012.
		Year Ended December 31, 2014				Year Ended December 31, 2013				Year Ended December 31, 2012
	(In thousands)	ProAssurance		ProAssurance		ProAssurance		ProAssurance		ProAssurance		ProAssurance
		Pro Forma		Actual		Pro Forma		Actual		Pro Forma		Actual
		Consolidated		Consolidated Results		Consolidated		Consolidated Results		Consolidated		Consolidated Results
		Results				Results				Results
	Revenue	$852,326		$852,326		$926,873		$740,178		$757,240		$715,854
	Net income	$197,533		$196,565		$263,446	*	$297,523		$317,097		$275,470
	* Includes adjustments related to Eastern of $0.4 million and Medmarc of $33.7 million.

Fair_Value_Measurement_Tables

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2014
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 December 31, 2014 and December 31, 2013, are shown in the following tables. 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.
		31-Dec-14
		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	$	—			$	166,512			$	—		$	166,512
	U.S. Government-sponsored enterprise obligations	—				39,563				—			39,563
	State and municipal bonds	—				1,057,590				5,025			1,062,615
	Corporate debt, multiple observable inputs	—				1,404,020				—			1,404,020
	Corporate debt, limited observable inputs:
	Other corporate debt, NRSRO ratings available	—				—				10,474			10,474
	Other corporate debt, NRSRO ratings not available	—				—				2,607			2,607
	Residential mortgage-backed securities	—				276,056				—			276,056
	Agency commercial mortgage-backed securities	—				15,493				—			15,493
	Other commercial mortgage-backed securities	—				51,063				—			51,063
	Other asset-backed securities	—				111,855				4,769			116,624
	Equity securities
	Financial	79,341				—				—			79,341
	Utilities/Energy	25,629				—				—			25,629
	Consumer oriented	65,670				—				—			65,670
	Industrial	55,460				—				—			55,460
	Bond funds	55,196				—				—			55,196
	All other	33,186				—				—			33,186
	Short-term investments	131,199				60				—			131,259
	Financial instruments carried at fair value, classified as a part of:
	Investment in unconsolidated subsidiaries	—				—				133,250			133,250
	Other investments	$	6,050			$	22,908			$	—		$	28,958
	Total assets	$	451,731			$	3,145,120			$	156,125		$	3,752,976
		31-Dec-13
		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	$	—			$	170,714			$	—		$	170,714
	U.S. Government-sponsored enterprise obligations	—				32,768				—			32,768
	State and municipal bonds	—				1,147,328				7,338			1,154,666
	Corporate debt, multiple observable inputs	—				1,346,977				—			1,346,977
	Corporate debt, limited observable inputs:
	Other corporate debt, NRSRO ratings available	—				—				11,449			11,449
	Other corporate debt, NRSRO ratings not available	—				—				2,727			2,727
	Residential mortgage-backed securities	—				235,614				—			235,614
	Agency commercial mortgage-backed securities	—				27,475				—			27,475
	Other commercial mortgage-backed securities	—				61,390				—			61,390
	Other asset-backed securities	—				67,455				6,814			74,269
	Equity securities
	Financial	81,536				—				—			81,536
	Utilities/Energy	32,350				—				—			32,350
	Consumer oriented	66,461				—				—			66,461
	Industrial	57,262				—				—			57,262
	All other	15,932				—				—			15,932
	Short-term investments	248,605											248,605
	Financial instruments carried at fair value, classified as a part of:
	Investment in unconsolidated subsidiaries	—				—				72,062			72,062
	Total assets	$	502,146			$	3,089,721			$	100,390		$	3,692,257
Investments in Limited liability companies and limited partnerships	Investment in unconsolidated subsidiaries consisted of limited partnership (LP) and limited liability company (LLC) interests valued using the NAV provided by the LP/LLC, which approximated the fair value of the interest.
	Such interests include the following:
		Unfunded	Fair Value
		Commitments
	(In thousands)	December 31,	December 31,				December 31,
		2014	2014				2013
	Investments in LPs/LLCs:
	Private debt funds (1)	$27,578	$	37,296			$	13,233
	Long equity fund (2)	None	6,747				6,574
	Long/Short equity funds (3)	None	25,301				28,385
	Non-public equity funds (4)	$66,545	51,811				23,870
	Multi-strategy fund of funds (5)	None	8,271				—
	Structured credit fund (6)	None	3,824				—
			$	133,250			$	72,062
	-1	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 LPs over an anticipated time frame that spans from 3 to 8 years.
	-2	This fund is an 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	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 event-driven market opportunities. The funds generally permit quarterly or semi-annual redemptions of the investors' existing capital balance with 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	Comprised of interests in three unrelated LP funds, each structured to provide capital appreciation through diversified investments in private equity, which can include investments in buyout, venture capital, mezzanine debt, distressed debt and other private equity-oriented LPs. One LP allows redemption by special consent; 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 9 years.
	-5	This fund is an 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 the LLC Board is permitted discretion to periodically extend offers to repurchase units of the LLC.
	-6	This fund is an 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.
Summary of quantitative information about Level 3 fair value measurements	Quantitative Information Regarding Level 3 Valuations
	Quantitative Information about Level 3 Fair Value Measurements
			Fair Value at
	(In millions)		31-Dec-14		31-Dec-13		Valuation Technique		Unobservable Input		Range
											(Weighted Average)
	Assets:
	State and municipal bonds		$5.00		$7.30		Market Comparable		Comparability Adjustment		0% - 10% (5%)
							Securities
							Discounted Cash Flows		Comparability Adjustment		0% - 10% (5%)
	Corporate debt with limited observable inputs		$13.10		$14.20		Market Comparable		Comparability Adjustment		0% - 5% (2.5%)
							Securities
							Discounted Cash Flows		Comparability Adjustment		0% - 5% (2.5%)
	Other asset-backed securities		$4.80		$6.80		Market Comparable		Comparability Adjustment		0% - 5% (2.5%)
							Securities
							Discounted Cash Flows		Comparability Adjustment		0% - 5% (2.5%)
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.
		31-Dec-14
		Level 3 Fair Value Measurements – Assets
	(In thousands)	U.S. Government-sponsored Enterprise Obligations				State and Municipal Bonds				Corporate Debt			Asset-backed Securities			Investment in Unconsolidated Subsidiaries			Total
	Balance December 31, 2013	$	—			$	7,338			$	14,176		$	6,814		$	72,062		$	100,390
	Total gains (losses) realized and unrealized:
	Included in earnings, as a part of:
	Net investment income	—				(14		)		65			—			—			51
	Equity in earnings of unconsolidated subsidiaries	—				—				—			—			10,538			10,538
	Net realized investment gains (losses)	—				(95		)		3			—			—			(92		)
	Included in other comprehensive income	1				(29		)		688			59			—			719
	Purchases	1,000				1,861				2,000			3,340			56,340			64,541
	Sales	—				(1,731		)		(1,826		)	(61		)	(5,690		)	(9,308		)
	Transfers in	—				2,119				—			305			—			2,424
	Transfers out	(1,001		)		(4,424		)		(2,025		)	(5,688		)	—			(13,138		)
	Balance December 31, 2014	$	—			$	5,025			$	13,081		$	4,769		$	133,250		$	156,125
	Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	$	—			$	—			$	—		$	—		$	10,538		$	10,538
		31-Dec-13
		Level 3 Fair Value Measurements – Assets
	(In thousands)	U.S. Government-sponsored Enterprise Obligations				State and Municipal Bonds				Corporate Debt			Asset-backed Securities			Investment in Unconsolidated Subsidiaries			Total
	Balance December 31, 2012	$	—			$	7,175			$	15,191		$	4,035		$	33,739		$	60,140
	Total gains (losses) realized and unrealized:
	Included in earnings, as a part of:
	Net investment income	—				—				(103		)	(17		)	—			(120		)
	Equity in earnings of unconsolidated subsidiaries	—				—				—			—			6,877			6,877
	Net realized investment gains (losses)	—				(44		)		(69		)	—			—			(113		)
	Included in other comprehensive income	—				1				(725		)	(61		)	—			(785		)
	Purchases	—				—				9,470			1,356			24,567			35,393
	Sales	—				(2,106		)		(1,629		)	(18		)	(14,632		)	(18,385		)
	Transfers in	—				2,312				2,114			3,800			21,511			29,737
	Transfers out	—				—				(10,073		)	(2,281		)	—			(12,354		)
	Balance December 31, 2013	$	—			$	7,338			$	14,176		$	6,814		$	72,062		$	100,390
	Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	$	—			$	—			$	—		$	—		$	6,877		$	6,877
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.
		31-Dec-14								31-Dec-13
	(In thousands)	Carrying				Fair				Carrying			Fair
		Value				Value				Value			Value
	Financial assets:
	BOLI	$	56,381			$	56,381			$	54,374		$	54,374
	Other investments	57,099				57,994				52,240			51,833
	Other assets	22,440				22,399				17,940			17,940
	Financial liabilities:
	Senior notes due 2023	$	250,000			$	276,503			$	250,000		$	262,500
	Other liabilities	14,656				14,645				13,303			13,303

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2014
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 December 31, 2014 and December 31, 2013 included the following:
		31-Dec-14
	(In thousands)	Amortized			Gross Unrealized Gains				Gross Unrealized Losses				Estimated Fair Value
		Cost
	Fixed maturities
	U.S. Treasury obligations	$	163,714		$	3,785			$	987			$	166,512
	U.S. Government-sponsored enterprise obligations	38,022			1,641				100				39,563
	State and municipal bonds	1,015,555			47,395				335				1,062,615
	Corporate debt	1,389,970			44,234				17,103				1,417,101
	Residential mortgage-backed securities	266,306			10,198				448				276,056
	Agency commercial mortgage-backed securities	15,344			208				59				15,493
	Other commercial mortgage-backed securities	50,025			1,137				99				51,063
	Other asset-backed securities	116,541			288				205				116,624
		$	3,055,477		$	108,886			$	19,336			$	3,145,027
		31-Dec-13
	(In thousands)	Amortized			Gross Unrealized Gains				Gross Unrealized Losses				Estimated Fair Value
		Cost
	Fixed maturities
	U.S. Treasury obligations	$	166,115		$	6,118			$	1,519			$	170,714
	U.S. Government-sponsored enterprise obligations	30,942			2,251				425				32,768
	State and municipal bonds	1,116,060			46,533				7,927				1,154,666
	Corporate debt	1,321,838			53,059				13,744				1,361,153
	Residential mortgage-backed securities	230,861			7,608				2,855				235,614
	Agency commercial mortgage-backed securities	27,268			343				136				27,475
	Other commercial mortgage-backed securities	59,066			2,491				167				61,390
	Other asset-backed securities	74,106			487				324				74,269
		$	3,026,256		$	118,890			$	27,097			$	3,118,049
Schedule of available for sale securities by contractual maturity	The recorded cost basis and estimated fair value of available-for-sale fixed maturities at December 31, 2014, 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
		Cost			year or less				one year				five years		ten years		Value
									through				through
									five years				ten years
	Fixed maturities, available for sale
	U.S. Treasury obligations	$	163,714		$	9,584			$	113,489			$	39,264	$	4,175	$	166,512
	U.S. Government-sponsored enterprise obligations	38,022			3,641				25,286				10,287		349		39,563
	State and municipal bonds	1,015,555			44,334				380,741				453,275		184,265		1,062,615
	Corporate debt	1,389,970			115,301				711,806				566,585		23,409		1,417,101
	Residential mortgage-backed securities	266,306															276,056
	Agency commercial mortgage-backed securities	15,344															15,493
	Other commercial mortgage-backed securities	50,025															51,063
	Other asset-backed securities	116,541															116,624
		$	3,055,477														$	3,145,027
Other Investments	Other investments at December 31, 2014 and December 31, 2013 was comprised as follows:
	(In thousands)	December 31,			December 31,
		2014			2013
	Investments in LPs/LLCs, at cost	$	53,258		$	47,258
	Convertible securities, at fair value, see Note 1	28,958			—
	Other, principally FHLB capital stock, at cost	3,841			4,982
		$	86,057		$	52,240
Unconsolidated Subsidiaries	ProAssurance holds investments in unconsolidated subsidiaries, accounted for under the equity method. The investments include the following:
		31-Dec-14						Carrying Value
	(In thousands)	Unfunded			Percentage			December 31,				December 31,
		Commitments*			Ownership			2014				2013
	Investment in LPs/LLCs:
	Tax credit partnerships	$	15,537		See below			$	133,143			$	142,174
	Private debt funds	27,578			<	20%		37,296				13,233
	Long equity fund	None			<	20%		6,747				6,574
	Long/short equity funds	None			<	25%		25,301				28,385
	Non-public equity funds	80,070			<	20%		58,128				23,870
	Multi-strategy fund of funds	—			<	20%		8,271				—
	Structured credit fund	—			<	20%		3,824				—
	Real estate fund	6,526			<	20%		3,791				—
								$	276,501			$	214,236
	* Unfunded commitments are included in the carrying value of tax credit partnerships only.
Investments held in an unrealized loss position	The following tables provide summarized information with respect to investments held in an unrealized loss position at December 31, 2014 and December 31, 2013, including the length of time the investment had been held in a continuous unrealized loss position.
		31-Dec-14
		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	$	61,209		$	987			$	46,869			$	617	$	14,340	$	370
	U.S. Government-sponsored enterprise obligations	6,268			100				2,775				44		3,493		56
	State and municipal bonds	39,831			335				18,910				84		20,921		251
	Corporate debt	423,107			17,103				326,804				13,236		96,303		3,867
	Residential mortgage-backed securities	45,006			448				14,406				31		30,600		417
	Agency commercial mortgage-backed securities	4,783			59				70				—		4,713		59
	Other commercial mortgage-backed securities	13,860			99				7,005				28		6,855		71
	Other asset-backed securities	62,577			205				59,176				109		3,401		96
		$	656,641		$	19,336			$	476,015			$	14,149	$	180,626	$	5,187
	Other investments
	Investments in LPs/LLCs carried at cost	$	23,683		$	3,948			$	22,265			$	3,711	$	1,418	$	237
		31-Dec-13
		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	$	47,668		$	1,519			$	44,304			$	1,182	$	3,364	$	337
	U.S. Goverment-sponsored enterprise obligations	$	6,640		$	425			$	5,752			$	321	$	888	$	104
	State and municipal bonds	203,970			7,927				184,401				6,640		19,569		1,287
	Corporate debt	349,277			13,744				324,510				12,061		24,767		1,683
	Residential mortgage-backed securities	93,608			2,855				84,045				2,393		9,563		462
	Agency commercial mortgage-backed securities	11,658			136				11,082				116		576		20
	Other commercial mortgage-backed securities	11,153			167				10,215				159		938		8
	Other asset-backed securities	25,539			324				21,804				77		3,735		247
		$	749,513		$	27,097			$	686,113			$	22,949	$	63,400	$	4,148
	Other investments
	Investments in LPs/LLCs carried at cost	$	14,752		$	1,059			$	13,166			$	1,018	$	1,586	$	41
Net Investment Income	Net investment income by investment category was as follows:
		Year Ended December 31
	(In thousands)	2014			2013				2012
	Fixed maturities	$	111,895		$	122,065			$	133,088
	Equities	10,817			9,454				6,947
	Short-term and Other investments	8,833			2,584				660
	Business owned life insurance	2,006			1,960				2,008
	Investment fees and expenses	(7,994		)	(6,798		)		(6,609		)
	Net investment income	$	125,557		$	129,265			$	136,094
Net realized investment gains (losses)	The following table provides detailed information regarding net realized investment gains (losses):
		Year Ended December 31
	(In thousands)	2014			2013				2012
	Total other-than-temporary impairment losses:
	State and municipal bonds	$	(50	)	$	(71	)		$	—
	Residential mortgage-backed securities	—			—				(557		)
	Corporate debt	(1,425		)	—				(878		)
	Other investments	—			—				(131		)
	Portion recognized in (reclassified from) Other Comprehensive Income:
	Corporate debt	268			—				(201		)
	Net impairments recognized in earnings	(1,207		)	(71		)		(1,767		)
	Gross realized gains, available-for-sale securities	5,627			18,130				18,645
	Gross realized (losses), available-for-sale securities	(1,103		)	(7,031		)		(2,076		)
	Net realized gains (losses), trading securities	28,018			20,444				1,485
	Net realized gains (losses), Other investments	326			—				—
	Change in unrealized holding gains (losses), trading securities	(18,883		)	35,507				12,673
	Change in unrealized holding gains (losses), convertible securities, carried at fair value	1,876			—				—
	Decrease (increase) in the fair value of liabilities carried at fair value	—			—				(1,245		)
	Other	—			925				1,148
	Net realized investment gains (losses)	$	14,654		$	67,904			$	28,863
Cumulative credit losses recorded in earnings related to impaired debt securities for which a portion of the OTTI has been recorded in OCI	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 other-than-temporary impairment was recorded in Other comprehensive income.
	(In thousands)	2014			2013				2012
	Balance January 1	$	83		$	3,301			$	5,870
	Additional credit losses recognized during the period, related to securities for which:
	No OTTI has been previously recognized	149			—				—
	OTTI has been previously recognized	—			—				268
	Reductions due to:
	Securities sold during the period (realized)	—			(3,218		)		(2,837		)
	Balance December 31	$	232		$	83			$	3,301
Information regarding sales and purchases of available-for-sale securities	Other information regarding sales and purchases of available-for-sale securities is as follows:
		Year Ended December 31
	(In millions)	2014			2013			2012
	Proceeds from sales (exclusive of maturities and paydowns)	$	244.9		$	593.3		$	500.2
	Purchases	$	645.1		$	519.2		$	646.2

Reinsurance_Tables

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2014
Insurance [Abstract]
Summary of the effect of reinsurance on premiums written and earned	The effect of reinsurance on premiums written and earned was as follows:
	(In thousands)	2014 Premiums						2013 Premiums						2012 Premiums
		Written			Earned			Written			Earned			Written			Earned
	Direct	$	761,043		$	755,623		$	566,745		$	568,629		$	536,318		$	558,200
	Assumed	18,566			12,987			802			804			113			116
	Ceded	(77,760		)	(68,879		)	(42,365		)	(41,514		)	(8,133		)	(7,652		)
	Net premiums	$	701,849		$	699,731		$	525,182		$	527,919		$	528,298		$	550,664

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Components of deferred tax assets and liabilities	Significant components of ProAssurance’s deferred tax assets and liabilities were as follows:
	(In thousands)	2014			2013
	Deferred tax assets
	Unpaid loss discount	$	44,002		$	51,879
	Unearned premium adjustment	23,972			21,861
	Compensation related	18,623			18,172
	Intangibles	1,957			2,074
	Total deferred tax assets	88,554			93,986
	Deferred tax liabilities
	Deferred acquisition costs	9,180			10,150
	Unrealized gains on investments, net	31,342			32,127
	Fixed assets	3,689			4,166
	Basis differentials–investments	31,657			31,247
	Intangibles	27,294			13,238
	Other	4,210			1,301
	Total deferred tax liabilities	107,372			92,229
	Net deferred tax assets (liabilities)	$	(18,818	)	$	1,757
Reconciliation of unrecognized tax benefits	A reconciliation of the beginning and ending amounts of unrecognized tax benefits for 2014 and 2013 was as follows:
	(In thousands)	2014			2013			2012
	Balance at January 1	$	4,823		$	4,823		$	18,585
	Increase for tax position acquired as result of a business combination	414			—			—
	Increases for tax positions taken during the current year	163			—			—
	(Decreases) for tax positions taken during the current year	(4,823		)	—			(10,206		)
	(Decreases) for tax positions taken during prior years	—			—			(3,556		)
	Balance at December 31	$	577		$	4,823		$	4,823
Reconciliation of expected income tax expense to actual income tax expense	A reconciliation of “expected” income tax expense (35% of income before income taxes) to actual income tax expense for each of the years ended December 31, 2014, 2013 and 2012 follows:
	(In thousands)	2014			2013			2012
	Computed “expected” tax expense	$	91,702		$	139,005		$	138,588
	Tax-exempt income	(13,250		)	(14,509		)	(14,374		)
	Tax credits, qualified affordable housing	(17,918		)	(17,888		)	(10,005		)
	Non-taxable gain on acquisition	—			(11,310		)	—
	Non-U.S. Loss	1,741			—			—
	Other	3,165			4,338			6,287
	Total	$	65,440		$	99,636		$	120,496

Reserve_for_Losses_and_Loss_Ad1

Reserve for Losses and Loss Adjustment Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
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)	2014			2013			2012
	Balance, beginning of year	$	2,072,822		$	2,054,994		$	2,247,772
	Less reinsurance recoverables on unpaid losses and loss adjustment expenses	247,518			191,645			247,658
	Net balance, beginning of year	1,825,304			1,863,349			2,000,114
	Net reserves acquired from acquisitions	139,549			126,007			22,464
	Net losses:
	Current year	545,168			447,510			451,951
	Favorable development of reserves established in prior years, net	(182,084		)	(222,749		)	(272,038		)
	Total	363,084			224,761			179,913
	Paid related to:
	Current year	(93,737		)	(43,616		)	(38,439		)
	Prior years	(413,900		)	(345,197		)	(300,703		)
	Total paid	(507,637		)	(388,813		)	(339,142		)
	Net balance, end of year	1,820,300			1,825,304			1,863,349
	Plus reinsurance recoverables on unpaid losses and loss adjustment expenses	237,966			247,518			191,645
	Balance, end of year	$	2,058,266		$	2,072,822		$	2,054,994

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum lease payments for operating leases	The following is a schedule of future minimum lease payments for operating leases that had initial or remaining non-cancelable lease terms in excess of one year as of December 31, 2014.
	Operating Leases
	(In thousands)
	2015	$	5,024
	2016	4,915
	2017	3,601
	2018	2,965
	2019	2,572
	Thereafter	5,232
	Total minimum lease payments	$	24,309

Longterm_Debt_Tables

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Outstanding long-term debt	ProAssurance’s outstanding long-term debt consisted of the following:
	(In thousands)	December 31,		December 31,
		2014		2013
	Senior notes due 2023, unsecured, interest at 5.3% annually	$	250,000	$	250,000
	Revolving credit agreement, outstanding borrowings not permitted to exceed $200 million aggregately, expires in 2016	—		—
		$	250,000	$	250,000

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Common Stock Outstanding Rollforward	The following is a summary of changes in common shares issued and outstanding during the years ended December 31, 2014, 2013 and 2012:
	(In thousands of shares)	2014			2013			2012
	Issued and outstanding shares - January 1	61,197			61,624			61,107
	Repurchase of shares	(4,909	)		(681	)		—
	Shares issued due to exercise of options and vesting of share-based compensation awards	154			169			436
	Other shares issued for compensation and shares reissued to stock purchase plan*	92			85			81
	Issued and outstanding shares - December 31	56,534			61,197			61,624
	*	Shares issued were valued at fair value (the market price of a ProAssurance common share on the date of issue).
Dividends Declared	ProAssurance declared cash dividends during 2014, 2013 and 2012 as follows:
			Cash Dividends Declared, per Share
			2014				2013			2012
	First Quarter		$	0.3			$	0.25		$	0.125
	Second Quarter		$	0.3			$	0.25		$	0.125
	Third Quarter		$	0.3			$	0.25		$	0.125
	Fourth Quarter*		$	2.96			$	0.3		$	2.75
	* Includes special dividends of $2.65 per share in 2014 and $2.50 per share in 2012.
Reclassification adjustments related to available-for-sale securities	Amounts reclassified from accumulated other comprehensive income to net income and the amounts of deferred tax expense (benefit) included in OCI were as follows:
	(In thousands)	2014				2013			2012
	Reclassifications from accumulated other comprehensive income to net income, available-for-sale securities:
	Realized investment gains (losses)	$	3,317			$	11,375		$	17,350
	Non-credit impairment losses reclassified to earnings, due to sale of securities or reclassification as a credit loss	—				(347		)	(2,417		)
	Total amounts reclassified, before tax effect	3,317				11,028			14,933
	Tax effect (at 35%)	(1,161		)		(3,860		)	(5,227		)
	Net reclassification adjustments	$	2,156			$	7,168		$	9,706
	Deferred tax expense (benefit) included in OCI	$	(785	)		$	(46,157	)	$	8,262

ShareBased_Payments_Tables

Share-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of compensation expense and related tax benefit recognized during each period, and compensation cost expense in future periods	The following table provides a summary of compensation expense and compensation cost that will be charged to expense in future periods, by award type, and the total related tax benefit recognized during each period. There was no compensation expense related to stock option awards in 2014, 2013 or 2012.
		Share-Based										Unrecognized Compensation Cost
		Compensation Expense
		Year Ended December 31										31-Dec-14
		2014			2013			2012				Amount				Remaining
																Recognition Period
		(In millions)										(In millions)				(Weighted average years)
	Restricted Share Units	1.7			1.6			1.6				2				1.8
	Performance Share Units	7.6			7.1			6.7				6.3				1.7
	Purchase Match Units	0.8			0.5			0.3				1.6				2.2
	Total share-based compensation expense	$	10.1		$	9.2		$	8.6			$	9.9
	Tax benefit recognized	$	3.5		$	3.2		$	3
Summary of activity for stock options
		2014					2013							2012
		Options		Weighted			Options			Weighted				Options			Weighted
				Average						Average							Average
				Exercise						Exercise							Exercise
				Price						Price							Price
	Outstanding, beginning of year	18,082		$	23		20,302			$	23.15			1,014,661			$	22.76
	Granted	—		—			—			—				—			—
	Exercised	(13,626	)	22.47			(2,220	)		24.28				(994,148	)		22.75
	Forfeited or expired	—		—			—			—				(211	)		25.67
	Outstanding at end of year	4,456		24.64			18,082			23				20,302			23.15
	Exercisable at end of year	4,456		24.64			18,082			23				20,302			23.15
	Outstanding at end of year,	4,456		24.64			18,082			23				20,302			23.15
	vested or expected to vest
Summary of activity related to management share awards	Activity for restricted share units during 2014, 2013 and 2012 is summarized below. Grant date fair values are based on the market value of a ProAssurance common share on the date of grant.
		2014					2013							2012
		Units		Weighted			Units			Weighted				Units			Weighted
				Average						Average							Average
				Grant Date						Grant Date							Grant Date
				Fair Value						Fair Value							Fair Value
	Beginning non-vested balance	138,770		$	38.92		157,212			$	31.94			167,236			$	25.52
	Granted	49,750		46.34			39,400			46.97				51,864			42.22
	Forfeited	(2,044	)	44.88			(603	)		35.91				(2,823	)		35.23
	Vested and released	(49,674	)	29.22			(57,239	)		25.25				(59,065	)		22.61
	Ending non-vested balance	136,802		45.02			138,770			38.92				157,212			31.94
Summarized activity for performance share awards	The table reflects the base number of units; actual awards that vest depends upon the extent to which performance objectives are achieved. Grant date fair values are based on the market value of a ProAssurance common share on the date of grant.
		2014					2013							2012
		Base Units		Weighted			Base Units			Weighted				Base Units			Weighted
				Average						Average							Average
				Grant Date						Grant Date							Grant Date
				Fair Value						Fair Value							Fair Value
	Beginning non-vested balance	486,680		$	39.86		552,417			$	33.21			522,599			$	26.36
	Granted	160,900		46.34			145,580			46.97				212,205			42.22
	Forfeited	(14,221	)	45.3			(17,043	)		38.9				(20,492	)		31.44
	Vested and released	(166,499	)	31.33			(194,274	)		26.39				(161,895	)		23.13
	Ending non-vested balance	466,860		44.97			486,680			39.86				552,417			33.21
Market value of ProAssurance common share on the grant date fair value	Purchase match unit activity during 2014, 2013 and 2012 is summarized below. Grant date fair values are based on the market value of a ProAssurance common share on the date of grant.
		2014					2013							2012
		Units		Weighted			Units			Weighted				Units			Weighted
				Average						Average							Average
				Grant  Date						Grant  Date							Grant  Date
				Fair Value						Fair Value							Fair Value
	Beginning non-vested balance	63,125		$	41.34		40,985			$	39.85			18,900			$	36.2
	Granted	29,069		44.55			25,151			43.57				23,799			42.59
	Forfeited	(2,968	)	43.14			(2,456	)		40.71				(1,610	)		37.72
	Vested and released	(17,125	)	36.61			(555	)		36.33				(104	)		36.2
	Ending non-vested balance	72,101		43.69			63,125			41.34				40,985			39.85

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Financial data by segment for the years December 31, 2014, 2013 and 2012 were as follows:
		Year Ended December 31, 2014
	(In thousands)	Specialty P&C				Workers' Compensation				Lloyd's Syndicate				Corporate			Inter-segment Eliminations			Consolidated
	Net premiums earned	$	492,733			$	194,540			$	12,458			$	—		$	—		$	699,731
	Net investment income	—				—				410				125,147			—			125,557
	Equity in earnings (loss) of unconsolidated subsidiaries	—				—				—				3,986			—			3,986
	Net realized gains (losses)	—				—				4				14,650			—			14,654
	Other income	5,823				645				126				2,285			(481		)	8,398
	Net losses and loss adjustment expenses	(228,199		)		(126,447		)		(8,438		)		—			—			(363,084		)
	Underwriting, policy acquisition and operating expenses	(133,132		)		(60,357		)		(9,535		)		(8,768		)	481			(211,311		)
	Segregated portfolio cells dividend expense	—				(1,842		)		—				—			—			(1,842		)
	Interest expense	—				—				—				(14,084		)	—			(14,084		)
	Income tax benefit (expense)	—				—				—				(65,440		)	—			(65,440		)
	Segment operating results	$	137,225			$	6,539			$	(4,975	)		$	57,776		$	—		$	196,565
	Significant non-cash items
	Depreciation and amortization	$	8,945			$	5,828			$	477			$	35,073		$	—		$	50,323
		Year Ended December 31, 2013
	(In thousands)	Specialty P&C				Workers' Compensation				Lloyd's Syndicate				Corporate			Inter-segment Eliminations			Consolidated
	Net premiums earned	$	527,919			$	—			$	—			$	—		$	—		$	527,919
	Net investment income	—				—				—				129,265			—			129,265
	Equity in earnings (loss) of unconsolidated subsidiaries	—				—				—				7,539			—			7,539
	Net realized gains (losses)	—				—				—				67,904			—			67,904
	Other income	5,648				—				—				1,910			(7		)	7,551
	Gain on acquisition	—				—				—				32,314			—			32,314
	Net losses and loss adjustment expenses	(224,761		)		—				—				—			—			(224,761		)
	Underwriting, policy acquisition and operating expenses	(132,076		)		—				—				(15,748		)	7			(147,817		)
	Interest expense	—				—				—				(2,755		)	—			(2,755		)
	Income tax benefit (expense)	—				—				—				(99,636		)	—			(99,636		)
	Segment operating results	$	176,730			$	—			$	—			$	120,793		$	—		$	297,523
	Significant non-cash items
	Depreciation and amortization	$	7,199			$	—			$	—			$	38,768		$	—		$	45,967
		Year Ended December 31, 2012
	(In thousands)	Specialty P&C				Workers' Compensation				Lloyd's Syndicate				Corporate			Inter-segment Eliminations			Consolidated
	Net premiums earned	$	550,664			$	—			$	—			$	—		$	—		$	550,664
	Net investment income	—				—				—				136,094			—			136,094
	Equity in earnings (loss) of unconsolidated subsidiaries	—				—				—				(6,873		)	—			(6,873		)
	Net realized gains (losses)	—				—								28,863			—			28,863
	Other income	5,331				—				—				1,825			(50		)	7,106
	Gain on acquisition	—				—				—				—			—			—
	Net losses and loss adjustment expenses	(179,913		)		—				—				—			—			(179,913		)
	Underwriting, policy acquisition and operating expenses	(125,292		)		—				—				(10,389		)	50			(135,631		)
	Interest expense	—				—				—				(2,181		)	—			(2,181		)
	Loss on extinguishment of debt	—				—				—				(2,163		)	—			(2,163		)
	Income tax benefit (expense)	—												(120,496		)				(120,496		)
	Segment operating results	$	250,790			$	—			$	—			$	24,680		$	—		$	275,470
	Significant non-cash items
	Depreciation and amortization	$	7,355			$	—			$	—			$	30,218		$	—		$	37,573
Revenue from External Customers by Products and Services	The following table provides detailed information regarding gross premiums earned by major category within each segment 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 United States.
			Year Ended December 31
	(In thousands)		2014				2013				2012
	Specialty P&C Segment
	Gross premiums earned:
	Healthcare professional liability		$	477,031			$	507,222			$	539,729
	Legal professional liability		28,278				27,162				17,042
	Medical technology and life sciences products liability		35,913				33,242				—
	Other		1,830				1,807				1,545
	Ceded premiums earned*		(50,319		)		(41,514		)		(7,652		)
	Segment net premiums earned		$	492,733			$	527,919			$	550,664
	Workers' Compensation Segment
	Gross premiums earned:
	Traditional business		$	160,717			$	—			$	—
	Alternative market business		55,616				—				—
	Ceded premiums earned		(21,793		)		—				—
	Segment net premiums earned		$	194,540			$	—			$	—
	Lloyd's Syndicate Segment
	Gross premiums earned:
	Property and casualty*		$	13,429			$	—			$	—
	Ceded premiums earned		(971		)		—				—
	Segment net premiums earned		$	12,458			$	—			$	—
	Consolidated net premiums earned		$	699,731			$	527,919			$	550,664
	* Includes premium ceded from the Specialty P&C Segment to the Lloyd's Syndicate Segment of $4.2 million for year ended December 31, 2014.

Statutory_Accounting_and_Divid1

Statutory Accounting and Dividend Restrictions (Tables)	12 Months Ended
	Dec. 31, 2014
Statutory Accounting And Dividend Restrictions [Abstract]
Consolidated net income	Net earnings and capital and surplus of ProAssurance’s insurance subsidiaries on a statutory basis are shown in the following table.
	(In millions)
	Statutory Net Earnings			Statutory Capital and Surplus
	2014	2013	2012	2014	2013
	$246	$256	$312	$1,681	$1,642

Quarterly_Results_of_Operation1

Quarterly Results of Operations (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Summary of unaudited quarterly results of operations	The following is a summary of unaudited quarterly results of operations for 2014 and 2013:
			2014
	(In thousands, except per share data)		1st			2nd			3rd			4th
	Net premiums earned		$	171,730		$	176,303		$	177,028		$	174,670
	Net losses and loss adjustment expenses:
	Current year		137,647			141,126			142,124			124,271
	Prior year		(48,139		)	(42,213		)	(42,902		)	(48,830		)
	Net income		46,731			49,942			34,778			65,114
	Basic earnings per share*		0.76			0.84			0.59			1.13
	Diluted earnings per share*		0.76			0.84			0.59			1.12
			2013
	(In thousands, except per share data)		1st			2nd			3rd			4th
	Net premiums earned		$	134,578		$	130,352		$	133,598		$	129,392
	Net losses and loss adjustment expenses:
	Current year		110,726			109,109			110,987			116,689
	Prior year		(53,100		)	(38,500		)	(49,350		)	(81,799		)
	Net income		112,850			50,451			63,357			70,864
	Basic earnings per share*		1.83			0.82			1.02			1.15
	Diluted earnings per share*		1.82			0.81			1.02			1.14
	*	Quarterly and year-to-date computations of per share amounts are made independently; therefore, the sum of per share amounts for the quarters may not equal per share amounts for the respective year-to-date periods.

Accounting_Policies_Details

Accounting Policies (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summary of allowances for credit losses related to premium and agency receivables
Allowance acquired from acquisition	$225	$0
Premium Receivables [Member]
Summary of allowances for credit losses related to premium and agency receivables
Allowance for credit losses, Beginning balance	990	1,000
Estimated credit losses	299	236
Account write offs, net of recoveries	-299	-246
Allowance for credit losses, Ending balance	1,215	990
Agency Receivables [Member]
Summary of allowances for credit losses related to premium and agency receivables
Allowance for credit losses, Beginning balance	50	286
Estimated credit losses	0	0
Account write offs, net of recoveries	0	-236
Allowance for credit losses, Ending balance	$50	$50

Accounting_Policies_Details_1

Accounting Policies (Details 1) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Carrying value of indefinite lived intangible assets	$25.80	$16.80
Carrying value of finite-lived intangible assets	96.2	51.7
Total Intangible Assets	122	68.5
Accumulated amortization of intangible assets	21.2	16.5
Amortization expense for intangible assets	$10.30	$5.30	$4.50

Accounting_Policies_Accounting

Accounting Policies Accounting Policies (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Unpaid dividends	$167,744,000	$18,532,000	$0
Segregated portfolio cell (SPC) dividends payable	15,800,000	0
All other	137,400,000	124,600,000
Total other liabilities	$320,853,000	$143,079,000

Accounting_Policies_Details_Te

Accounting Policies (Details Textual) (USD $)	0 Months Ended	12 Months Ended
	Dec. 27, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
		Segment
Accounting Policies [Abstract]
Number of reportable segments		4
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock split, conversion ratio	2
Insurance policy duration		1 year
Earned But unbilled premiums		$3,400,000
Percentage of tax benefit		50.00%
Property, Plant and Equipment [Line Items]
Depreciation		6,956,000	4,538,000	4,741,000
Estimated aggregate amortization of intangible assets for 2015		8,300,000
Estimated aggregate amortization of intangible assets for 2016		8,000,000
Estimated aggregate amortization of intangible assets for 2017		5,600,000
Estimated aggregate amortization of intangible assets for 2018		5,600,000
Estimated aggregate amortization of intangible assets for 2019		5,600,000
Third party conversion agent asset			205,000,000
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Real estate accumulated depreciation		23,000,000	21,600,000
Depreciation		1,500,000	1,500,000	1,400,000
Reclassifications [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Unearned ceding commission			800,000
Ceding commission income			$5,900,000	$2,100,000

Business_Combinations_Details

Business Combinations (Details) (USD $)	12 Months Ended			0 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 01, 2014	Jan. 01, 2013
Business Acquisition [Line Items]
Goodwill	$210,725	$161,115
Gain on acquisition	0	-32,314	0
Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Fixed maturities, available for sale				107,131
Equity securities, trading				65,945
Cash and short-term investments				58,944
Other investments				42,133
Premiums receivable, net				71,989
Receivable from reinsurers on paid and unpaid losses and LAE				18,942
Intangible assets				59,000
Deferred policy acquisition costs (see discussion below)				10,593
Other assets				19,225
Reserve for losses and loss adjustment expenses				-153,191
Unearned premiums				-80,268
Ceded balances payable				-9,507
Segregated portfolio cells dividends payable				-14,430
Deferred tax liabilities, net				-12,835
Other liabilities				-28,038
Fair value of net assets acquired				155,633
Goodwill				49,610
Gain on acquisition	0
Total purchase consideration	205,243			205,000
Medmarc [Member]
Business Acquisition [Line Items]
Fixed maturities, available for sale					269,529
Equity securities, trading					30,976
Cash and short-term investments					24,008
Other investments					5,340
Premiums receivable, net					2,986
Receivable from reinsurers on paid and unpaid losses and LAE					73,107
Intangible assets					3,630
Deferred policy acquisition costs (see discussion below)					0
Other assets					14,614
Reserve for losses and loss adjustment expenses					-201,072
Unearned premiums					-16,937
Ceded balances payable					0
Segregated portfolio cells dividends payable					0
Deferred tax liabilities, net					-4,934
Other liabilities					-15,233
Fair value of net assets acquired					186,014
Goodwill					0
Gain on acquisition		-32,314
Total purchase consideration		$153,700		$153,700

Business_Combinations_Details_

Business Combinations (Details 1) (USD $)	0 Months Ended
In Millions, unless otherwise specified	Jan. 01, 2014		Jan. 01, 2013
Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date	$50
Estimated Useful Life, Finite Lived Assets	13 years	[1]
Medmarc [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date			1.1
Estimated Useful Life, Finite Lived Assets			2 years	[1]
Agency relationships [Member] | Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date	27
Estimated Useful Life	15 years
Agency relationships [Member] | Medmarc [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date			0
Policyholder relationships [Member] | Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date	8
Estimated Useful Life	15 years
Policyholder relationships [Member] | Medmarc [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date			0
Trade names [Member] | Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date	8
Estimated Useful Life	15 years
Trade names [Member] | Medmarc [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date			0
Non-compete agreements [Member] | Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date	7
Estimated Useful Life	3 years
Non-compete agreements [Member] | Medmarc [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date			1.1
Estimated Useful Life			2 years	[2]
Insurance License Agreements [Member] | Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date, Finite Lived Assets	9
Insurance License Agreements [Member] | Medmarc [Member]
Business Acquisition [Line Items]
Estimated Fair Value on Acquisition Date, Finite Lived Assets			$2.50
[1]	Reflects the weighted average estimated useful life of acquired intangible assets that are subject to amortization.
[2]	Medmarc non-compete agreements were fully amortized as of December 31, 2014.

Business_Combinations_Details_1

Business Combinations (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Business Acquisition [Line Items]
ProAssurance Pro Forma Consolidated Results									$852,326,000	$926,873,000		$757,240,000
ProAssurance Pro Forma Consolidated Net Income									852,326,000	740,178,000		715,854,000
Business Acquisition, Pro Forma Net Income (Loss)									197,533,000	263,446,000	[1]	317,097,000
Net income	65,114,000	34,778,000	49,942,000	46,731,000	70,864,000	63,357,000	50,451,000	112,850,000	196,565,000	297,523,000		275,470,000
Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Adjustments related to pro forma revenue										400,000	[1]
Medmarc [Member]
Business Acquisition [Line Items]
Adjustments related to pro forma revenue										$33,700,000	[1]
[1]	Includes adjustments related to Eastern of $0.4 million and Medmarc of $33.7 million.

Business_Combinations_Details_2

Business Combinations (Details Textual) (USD $)	0 Months Ended	12 Months Ended
	Jan. 01, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 01, 2013
Business Acquisition [Line Items]
Goodwill		$210,725,000	$161,115,000
Gain on acquisition		0	32,314,000	0
Medmarc [Member]
Business Acquisition [Line Items]
Total purchase consideration	153,700,000		153,700,000
Expenses related to the purchase of business			2,600,000	1,000,000
Business acquisition, related premium credits to eligible policyholders					7,500,000
Goodwill					0
Gain on acquisition			32,314,000
Revenue of aquiree since acquisition date		41,400,000	46,500,000
Earnings of acquiree since acquisition date		8,100,000	15,700,000
Eastern Insurance Holdings [Member]
Business Acquisition [Line Items]
Voting interests acquired	100.00%
Total purchase consideration	205,000,000	205,243,000
Expenses related to the purchase of business		2,200,000	900,000
Goodwill	49,610,000
Gain on acquisition		0
Risk premium used in fair value estimate of acquired reserves for losses and related reinsurance recoverables	9,300,000
Amortization period of fair value adjustment	6 years
Profit margin used in fair value estimate of acquired reserves for losses and related reinsurance recoverables	5.00%
Risk premium used in fair value estimate of acquired reserves for losses and related reinsurance recoverables	5.00%
Revenue of aquiree since acquisition date		202,200,000
Earnings of acquiree since acquisition date		$9,100,000

Fair_Value_Measurement_Details

Fair Value Measurement (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets:
Equity securities, trading, at fair value	$314,482	$253,541
Level 3 [Member] | State and municipal bonds [Member]
Financial instruments carried at fair value, classified as a part of:
Total assets	5,000	7,300
Level 3 [Member] | Other asset-backed securities [Member]
Financial instruments carried at fair value, classified as a part of:
Total assets	4,800	6,800
Fair Value, Measurements, Recurring [Member]
Financial instruments carried at fair value, classified as a part of:
Investment in unconsolidated subsidiaries	133,250	72,062
Other Investments Fair Value Disclosure	28,958
Total assets	3,752,976	3,692,257
Fair Value, Measurements, Recurring [Member] | U.S. Treasury obligations [Member]
Assets:
Fair value of available for sale securities	166,512	170,714
Fair Value, Measurements, Recurring [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fair value of available for sale securities	39,563	32,768
Fair Value, Measurements, Recurring [Member] | State and municipal bonds [Member]
Assets:
Fair value of available for sale securities	1,062,615	1,154,666
Fair Value, Measurements, Recurring [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fair value of available for sale securities	1,404,020	1,346,977
Fair Value, Measurements, Recurring [Member] | Other corporate debt, NRSRO ratings available [Member]
Assets:
Fair value of available for sale securities	10,474	11,449
Fair Value, Measurements, Recurring [Member] | Other corporate debt, NRSRO ratings not available [Member]
Assets:
Fair value of available for sale securities	2,607	2,727
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	276,056	235,614
Fair Value, Measurements, Recurring [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	15,493	27,475
Fair Value, Measurements, Recurring [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	51,063	61,390
Fair Value, Measurements, Recurring [Member] | Other asset-backed securities [Member]
Assets:
Fair value of available for sale securities	116,624	74,269
Fair Value, Measurements, Recurring [Member] | Financial [Member]
Assets:
Equity securities, trading, at fair value	79,341	81,536
Fair Value, Measurements, Recurring [Member] | Utilities/Energy [Member]
Assets:
Equity securities, trading, at fair value	25,629	32,350
Fair Value, Measurements, Recurring [Member] | Consumer oriented [Member]
Assets:
Equity securities, trading, at fair value	65,670	66,461
Fair Value, Measurements, Recurring [Member] | Industrial [Member]
Assets:
Equity securities, trading, at fair value	55,460	57,262
Fair Value, Measurements, Recurring [Member] | Fixed Income Funds [Member]
Assets:
Equity securities, trading, at fair value	55,196
Fair Value, Measurements, Recurring [Member] | All other [Member]
Assets:
Equity securities, trading, at fair value	33,186	15,932
Fair Value, Measurements, Recurring [Member] | Short-term Investments [Member]
Assets:
Short-term investments	131,259	248,605
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial instruments carried at fair value, classified as a part of:
Investment in unconsolidated subsidiaries	0	0
Other Investments Fair Value Disclosure	6,050
Total assets	451,731	502,146
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury obligations [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | State and municipal bonds [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other corporate debt, NRSRO ratings available [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other corporate debt, NRSRO ratings not available [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Residential mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other asset-backed securities [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Financial [Member]
Assets:
Equity securities, trading, at fair value	79,341	81,536
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Utilities/Energy [Member]
Assets:
Equity securities, trading, at fair value	25,629	32,350
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Consumer oriented [Member]
Assets:
Equity securities, trading, at fair value	65,670	66,461
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Industrial [Member]
Assets:
Equity securities, trading, at fair value	55,460	57,262
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Fixed Income Funds [Member]
Assets:
Equity securities, trading, at fair value	55,196
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | All other [Member]
Assets:
Equity securities, trading, at fair value	33,186	15,932
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Short-term Investments [Member]
Assets:
Short-term investments	131,199	248,605
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial instruments carried at fair value, classified as a part of:
Investment in unconsolidated subsidiaries	0	0
Other Investments Fair Value Disclosure	22,908
Total assets	3,145,120	3,089,721
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury obligations [Member]
Assets:
Fair value of available for sale securities	166,512	170,714
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fair value of available for sale securities	39,563	32,768
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | State and municipal bonds [Member]
Assets:
Fair value of available for sale securities	1,057,590	1,147,328
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fair value of available for sale securities	1,404,020	1,346,977
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other corporate debt, NRSRO ratings available [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other corporate debt, NRSRO ratings not available [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Residential mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	276,056	235,614
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	15,493	27,475
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	51,063	61,390
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other asset-backed securities [Member]
Assets:
Fair value of available for sale securities	111,855	67,455
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Financial [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Utilities/Energy [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Consumer oriented [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Industrial [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Fixed Income Funds [Member]
Assets:
Equity securities, trading, at fair value	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | All other [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Short-term Investments [Member]
Assets:
Short-term investments	60
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial instruments carried at fair value, classified as a part of:
Investment in unconsolidated subsidiaries	133,250	72,062
Other Investments Fair Value Disclosure	0
Total assets	156,125	100,390
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury obligations [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Government-sponsored enterprise obligations [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | State and municipal bonds [Member]
Assets:
Fair value of available for sale securities	5,025	7,338
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate debt, multiple observable inputs [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other corporate debt, NRSRO ratings available [Member]
Assets:
Fair value of available for sale securities	10,474	11,449
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other corporate debt, NRSRO ratings not available [Member]
Assets:
Fair value of available for sale securities	2,607	2,727
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Residential mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Agency commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other commercial mortgage-backed securities [Member]
Assets:
Fair value of available for sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other asset-backed securities [Member]
Assets:
Fair value of available for sale securities	4,769	6,814
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Financial [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Utilities/Energy [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Consumer oriented [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Industrial [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Fixed Income Funds [Member]
Assets:
Equity securities, trading, at fair value	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | All other [Member]
Assets:
Equity securities, trading, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Short-term Investments [Member]
Assets:
Short-term investments	$0

Fair_Value_Measurement_Details1

Fair Value Measurement (Details 1) (USD $)	Dec. 31, 2014		Dec. 31, 2013
Secured debt fund [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	$27,578,000	[1]
Investments in limited liability companies and limited partnerships fair value	37,296,000	[1]	13,233,000	[1]
Private equity fund [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0	[2]
Investments in limited liability companies and limited partnerships fair value	6,747,000	[2]	6,574,000	[2]
Long/Short equity funds [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0	[3]
Investments in limited liability companies and limited partnerships fair value	25,301,000	[3]	28,385,000	[3]
Non-public equity funds [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	66,545,000	[4]
Investments in limited liability companies and limited partnerships fair value	51,811,000	[4]	23,870,000	[4]
Multi-strategy fund of funds [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0	[5]
Investments in limited liability companies and limited partnerships fair value	8,271,000	[5]	0	[5]
Structured credit fund [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0	[6]
Investments in limited liability companies and limited partnerships fair value	3,824,000	[6]	0	[6]
Investment in unconsolidated subsidiaries [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships fair value	$133,250,000		$72,062,000
[1]	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 LPs over an anticipated time frame that spans from 3 to 8 years.
[2]	This fund is an 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]	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 event-driven market opportunities. The funds generally permit quarterly or semi-annual redemptions of the investors' existing capital balance with 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]	Comprised of interests in three unrelated LP funds, each structured to provide capital appreciation through diversified investments in private equity, which can include investments in buyout, venture capital, mezzanine debt, distressed debt and other private equity-oriented LPs. One LP allows redemption by special consent; 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 9 years.
[5]	This fund is an 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 the LLC Board is permitted discretion to periodically extend offers to repurchase units of the LLC.
[6]	This fund is an 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.

Fair_Value_Measurement_Details2

Fair Value Measurement (Details 2) (Fair Value, Inputs, Level 3 [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
State and municipal bonds [Member]
Assets:
Total assets	5,000	$7,300
State and municipal bonds [Member] | Market Approach Valuation Technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	10.00%
State and municipal bonds [Member] | Market Approach Valuation Technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
State and municipal bonds [Member] | Market Approach Valuation Technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	5.00%
State and municipal bonds [Member] | Income Approach Valuation Technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	10.00%
State and municipal bonds [Member] | Income Approach Valuation Technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
State and municipal bonds [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	5.00%
Corporate debt with limited observable inputs [Member]
Assets:
Total assets	13,100	14,200
Corporate debt with limited observable inputs [Member] | Market Approach Valuation Technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Corporate debt with limited observable inputs [Member] | Market Approach Valuation Technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Corporate debt with limited observable inputs [Member] | Market Approach Valuation Technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%
Corporate debt with limited observable inputs [Member] | Income Approach Valuation Technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Corporate debt with limited observable inputs [Member] | Income Approach Valuation Technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Corporate debt with limited observable inputs [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%
Asset-backed Securities, Securitized Loans and Receivables [Member]
Assets:
Total assets	4,800	$6,800
Asset-backed Securities, Securitized Loans and Receivables [Member] | Market Approach Valuation Technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Asset-backed Securities, Securitized Loans and Receivables [Member] | Market Approach Valuation Technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Asset-backed Securities, Securitized Loans and Receivables [Member] | Market Approach Valuation Technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%
Asset-backed Securities, Securitized Loans and Receivables [Member] | Income Approach Valuation Technique [Member] | Maximum [Member]
Assets:
Comparability Adjustment	5.00%
Asset-backed Securities, Securitized Loans and Receivables [Member] | Income Approach Valuation Technique [Member] | Minimum [Member]
Assets:
Comparability Adjustment	0.00%
Asset-backed Securities, Securitized Loans and Receivables [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member]
Assets:
Comparability Adjustment	2.50%

Fair_Value_Measurement_Details3

Fair Value Measurement (Details 3) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	$100,390	$60,140
Included in earnings, as a part of:
Included in other comprehensive income	719	-785
Purchases	64,541	35,393
Sales	-9,308	-18,385
Transfers in	2,424	29,737
Transfers out	-13,138	-12,354
Ending Balance	156,125	100,390
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	10,538	6,877
U.S. Government-sponsored enterprise obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	0	0
Included in earnings, as a part of:
Included in other comprehensive income	1	0
Purchases	1,000	0
Sales	0	0
Transfers in	0	0
Transfers out	-1,001	0
Ending Balance		0
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
State and municipal bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	7,338	7,175
Included in earnings, as a part of:
Included in other comprehensive income	-29	1
Purchases	1,861	0
Sales	-1,731	-2,106
Transfers in	2,119	2,312
Transfers out	-4,424	0
Ending Balance	5,025	7,338
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
Corporate debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	14,176	15,191
Included in earnings, as a part of:
Included in other comprehensive income	688	-725
Purchases	2,000	9,470
Sales	-1,826	-1,629
Transfers in	0	2,114
Transfers out	-2,025	-10,073
Ending Balance	13,081	14,176
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
Asset-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	6,814	4,035
Included in earnings, as a part of:
Included in other comprehensive income	59	-61
Purchases	3,340	1,356
Sales	-61	-18
Transfers in	305	3,800
Transfers out	-5,688	-2,281
Ending Balance	4,769	6,814
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
Investment in unconsolidated subsidiaries [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	72,062	33,739
Included in earnings, as a part of:
Included in other comprehensive income	0	0
Purchases	56,340	24,567
Sales	-5,690	-14,632
Transfers in	0	21,511
Transfers out	0	0
Ending Balance	133,250	72,062
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	10,538	6,877
Other Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	0
Included in earnings, as a part of:
Included in other comprehensive income	0
Purchases	0
Sales	0
Transfers in	0
Transfers out	0
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0
Net investment income [Member]
Included in earnings, as a part of:
Net investment income	51	-120
Net investment income [Member] | U.S. Government-sponsored enterprise obligations [Member]
Included in earnings, as a part of:
Net investment income	0	0
Net investment income [Member] | State and municipal bonds [Member]
Included in earnings, as a part of:
Net investment income	-14	0
Net investment income [Member] | Corporate debt [Member]
Included in earnings, as a part of:
Net investment income	65	-103
Net investment income [Member] | Asset-backed securities [Member]
Included in earnings, as a part of:
Net investment income	0	-17
Net investment income [Member] | Investment in unconsolidated subsidiaries [Member]
Included in earnings, as a part of:
Net investment income	0	0
Net investment income [Member] | Other Investments [Member]
Included in earnings, as a part of:
Net investment income	0
Equity in earnings of unconsolidated subsidiaries [Member]
Included in earnings, as a part of:
Net investment income	10,538	6,877
Equity in earnings of unconsolidated subsidiaries [Member] | U.S. Government-sponsored enterprise obligations [Member]
Included in earnings, as a part of:
Net investment income	0	0
Equity in earnings of unconsolidated subsidiaries [Member] | State and municipal bonds [Member]
Included in earnings, as a part of:
Net investment income	0	0
Equity in earnings of unconsolidated subsidiaries [Member] | Corporate debt [Member]
Included in earnings, as a part of:
Net investment income	0	0
Equity in earnings of unconsolidated subsidiaries [Member] | Asset-backed securities [Member]
Included in earnings, as a part of:
Net investment income	0	0
Equity in earnings of unconsolidated subsidiaries [Member] | Investment in unconsolidated subsidiaries [Member]
Included in earnings, as a part of:
Net investment income	10,538	6,877
Equity in earnings of unconsolidated subsidiaries [Member] | Other Investments [Member]
Included in earnings, as a part of:
Net investment income	0
Gain (Loss) on Investments [Member]
Included in earnings, as a part of:
Net investment income	-92	-113
Gain (Loss) on Investments [Member] | U.S. Government-sponsored enterprise obligations [Member]
Included in earnings, as a part of:
Net investment income	0	0
Gain (Loss) on Investments [Member] | State and municipal bonds [Member]
Included in earnings, as a part of:
Net investment income	-95	-44
Gain (Loss) on Investments [Member] | Corporate debt [Member]
Included in earnings, as a part of:
Net investment income	3	-69
Gain (Loss) on Investments [Member] | Asset-backed securities [Member]
Included in earnings, as a part of:
Net investment income	0	0
Gain (Loss) on Investments [Member] | Investment in unconsolidated subsidiaries [Member]
Included in earnings, as a part of:
Net investment income	0	0
Gain (Loss) on Investments [Member] | Other Investments [Member]
Included in earnings, as a part of:
Net investment income	$0

Fair_Value_Measurement_Details4

Fair Value Measurement (Details 4) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financial assets:
BOLI	$56,381	$54,374
Other investments	86,057	52,240
Other assets	93,263	329,979
Financial liabilities:
Notes payable, fair value disclosure	250,000	250,000
Total other liabilities	320,853	143,079
Not Measured At Fair Value [Member] | Carrying Value [Member]
Financial assets:
BOLI	56,381	54,374
Other investments	57,099	52,240
Other assets	22,440	17,940
Financial liabilities:
Total other liabilities	14,656	13,303
Not Measured At Fair Value [Member] | Carrying Value [Member] | Senior notes due 2023 [Member]
Financial liabilities:
Notes payable, fair value disclosure	250,000	250,000
Not Measured At Fair Value [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value [Member]
Financial assets:
BOLI	56,381	54,374
Other investments	57,994	51,833
Other assets	22,399	17,940
Financial liabilities:
Total other liabilities	14,645	13,303
Not Measured At Fair Value [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value [Member] | Senior notes due 2023 [Member]
Financial liabilities:
Notes payable, fair value disclosure	$276,503	$262,500

Fair_Value_Measurement_Details5

Fair Value Measurement (Details Textuals) (Details)	12 Months Ended
	Dec. 31, 2014
Private equity fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Entities that calculate net asset value notice period	15 days
Non-public equity funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Anticipated time frame for distribution at the discretion of the LP	9 years
Structured credit fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Entities that calculate net asset value notice period	90 days
Minimum [Member] | Secured debt fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Anticipated time frame for distribution at the discretion of the LP	3 years
Minimum [Member] | Long/Short equity funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Entities that calculate net asset value notice period	30 days
Redemption Percentage of LP at NAV for which initial payment is limited	90.00%
Maximum [Member] | Secured debt fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Anticipated time frame for distribution at the discretion of the LP	8 years
Maximum [Member] | Private equity fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Payment period for redemption of LP valued at NAV	10 days
Maximum [Member] | 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
Entities that calculate net asset value notice period	90 days

Fair_Value_Measurement_Details6

Fair Value Measurement (Details Textuals 1) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 1 to Level 2	$0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	156,125,000	100,390,000	60,140,000
Included in other comprehensive income	719,000	-785,000
Purchases	64,541,000	35,393,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	9,308,000	18,385,000
Transfers in	2,424,000	29,737,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	13,138,000	12,354,000
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	10,538,000	6,877,000
Carrying Value	276,501,000	214,236,000
Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		0
Included in other comprehensive income	0
Purchases	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0
Transfers in	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 2 to Level 1		$7,200,000

Investments_Details

Investments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
U.S. Treasury obligations [Member]
Fixed maturities, available for sale
Amortized Cost	$163,714	$166,115
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,785	6,118
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	987	1,519
Total Fair Value	166,512	170,714
U.S. Government-sponsored enterprise obligations [Member]
Fixed maturities, available for sale
Amortized Cost	38,022	30,942
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,641	2,251
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	100	425
Total Fair Value	39,563	32,768
State and municipal bonds [Member]
Fixed maturities, available for sale
Amortized Cost	1,015,555	1,116,060
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	47,395	46,533
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	335	7,927
Total Fair Value	1,062,615	1,154,666
Corporate debt [Member]
Fixed maturities, available for sale
Amortized Cost	1,389,970	1,321,838
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	44,234	53,059
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	17,103	13,744
Total Fair Value	1,417,101	1,361,153
Residential mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	266,306	230,861
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	10,198	7,608
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	448	2,855
Total Fair Value	276,056	235,614
Agency commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	15,344	27,268
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	208	343
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	59	136
Total Fair Value	15,493	27,475
Other commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	50,025	59,066
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,137	2,491
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	99	167
Total Fair Value	51,063	61,390
Other asset-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	116,541	74,106
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	288	487
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	205	324
Total Fair Value	116,624	74,269
Debt Securities [Member]
Fixed maturities, available for sale
Amortized Cost	3,055,477	3,026,256
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	108,886	118,890
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	19,336	27,097
Total Fair Value	$3,145,027	$3,118,049

Investments_Details_1

Investments (Details 1) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
U.S. Treasury obligations [Member]
Fixed maturities, available for sale
Amortized Cost	$163,714	$166,115
Due in one year or less	9,584
Due after one year through five years	113,489
Due after five years through ten years	39,264
Due after ten years	4,175
Total Fair Value	166,512	170,714
U.S. Government-sponsored enterprise obligations [Member]
Fixed maturities, available for sale
Amortized Cost	38,022	30,942
Due in one year or less	3,641
Due after one year through five years	25,286
Due after five years through ten years	10,287
Due after ten years	349
Total Fair Value	39,563	32,768
State and municipal bonds [Member]
Fixed maturities, available for sale
Amortized Cost	1,015,555	1,116,060
Due in one year or less	44,334
Due after one year through five years	380,741
Due after five years through ten years	453,275
Due after ten years	184,265
Total Fair Value	1,062,615	1,154,666
Corporate debt [Member]
Fixed maturities, available for sale
Amortized Cost	1,389,970	1,321,838
Due in one year or less	115,301
Due after one year through five years	711,806
Due after five years through ten years	566,585
Due after ten years	23,409
Total Fair Value	1,417,101	1,361,153
Residential mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	266,306	230,861
Total Fair Value	276,056	235,614
Agency commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	15,344	27,268
Total Fair Value	15,493	27,475
Other commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	50,025	59,066
Total Fair Value	51,063	61,390
Other asset-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	116,541	74,106
Total Fair Value	116,624	74,269
Debt Securities [Member]
Fixed maturities, available for sale
Amortized Cost	3,055,477	3,026,256
Total Fair Value	$3,145,027	$3,118,049

Investments_Details_2

Investments (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Investments
Other investments	$86,057	$52,240
Investments in LPs/LLCs, at cost [Member]
Other Investments
Other investments	53,258	47,258
Convertible Debt Securities [Member]
Other Investments
Other investments	28,958	0
FHLB And Other Investments [Member]
Other Investments
Other investments	$3,841	$4,982

Investments_Details_3

Investments (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Unconsolidated Subsidiaries
Carrying Value	$276,501,000	$214,236,000
Tax credit partnerships [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	15,537,000
Carrying Value	133,143,000	142,174,000
Secured debt fund [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	27,578,000
Carrying Value	37,296,000	13,233,000
Secured debt fund [Member] | Maximum [Member]
Unconsolidated Subsidiaries
Percentage Ownership	20.00%
Long equity fund [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	0
Carrying Value	6,747,000	6,574,000
Long equity fund [Member] | Maximum [Member]
Unconsolidated Subsidiaries
Percentage Ownership	20.00%
Long/Short equity funds [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	0
Carrying Value	25,301,000	28,385,000
Long/Short equity funds [Member] | Maximum [Member]
Unconsolidated Subsidiaries
Percentage Ownership	25.00%
Non-public equity funds [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	80,070,000
Carrying Value	58,128,000	23,870,000
Non-public equity funds [Member] | Maximum [Member]
Unconsolidated Subsidiaries
Percentage Ownership	20.00%
Multi-strategy fund of funds [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	0
Carrying Value	8,271,000	0
Multi-strategy fund of funds [Member] | Maximum [Member]
Unconsolidated Subsidiaries
Percentage Ownership	20.00%
Structured credit fund [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	0
Carrying Value	3,824,000	0
Structured credit fund [Member] | Maximum [Member]
Unconsolidated Subsidiaries
Percentage Ownership	20.00%
Real estate fund [Member]
Unconsolidated Subsidiaries
Unfunded Commitments	6,526,000
Carrying Value	$3,791,000	$0
Real estate fund [Member] | Maximum [Member]
Unconsolidated Subsidiaries
Percentage Ownership	20.00%

Investments_Details_4

Investments (Details 4) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Investments in LPs/LLCs [Member]
Investments held in an unrealized loss position
Fair Value	$23,683	$14,752
Unrealized Loss	3,948	1,059
Less than 12 months, Fair Value	22,265	13,166
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,711	1,018
12 months or longer, Fair Value	1,418	1,586
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	237	41
U.S. Treasury obligations [Member]
Investments held in an unrealized loss position
Fair Value	61,209	47,668
Unrealized Loss	987	1,519
Less than 12 months, Fair Value	46,869	44,304
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	617	1,182
12 months or longer, Fair Value	14,340	3,364
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	370	337
U.S. Government-sponsored enterprise obligations [Member]
Investments held in an unrealized loss position
Fair Value	6,268	6,640
Unrealized Loss	100	425
Less than 12 months, Fair Value	2,775	5,752
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	44	321
12 months or longer, Fair Value	3,493	888
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	56	104
State and municipal bonds [Member]
Investments held in an unrealized loss position
Fair Value	39,831	203,970
Unrealized Loss	335	7,927
Less than 12 months, Fair Value	18,910	184,401
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	84	6,640
12 months or longer, Fair Value	20,921	19,569
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	251	1,287
Corporate debt [Member]
Investments held in an unrealized loss position
Fair Value	423,107	349,277
Unrealized Loss	17,103	13,744
Less than 12 months, Fair Value	326,804	324,510
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	13,236	12,061
12 months or longer, Fair Value	96,303	24,767
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,867	1,683
Residential mortgage-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	45,006	93,608
Unrealized Loss	448	2,855
Less than 12 months, Fair Value	14,406	84,045
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	31	2,393
12 months or longer, Fair Value	30,600	9,563
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	417	462
Agency commercial mortgage-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	4,783	11,658
Unrealized Loss	59	136
Less than 12 months, Fair Value	70	11,082
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	116
12 months or longer, Fair Value	4,713	576
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	59	20
Other commercial mortgage-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	13,860	11,153
Unrealized Loss	99	167
Less than 12 months, Fair Value	7,005	10,215
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	28	159
12 months or longer, Fair Value	6,855	938
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	71	8
Other asset-backed securities [Member]
Investments held in an unrealized loss position
Fair Value	62,577	25,539
Unrealized Loss	205	324
Less than 12 months, Fair Value	59,176	21,804
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	109	77
12 months or longer, Fair Value	3,401	3,735
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	96	247
Debt Securities [Member]
Investments held in an unrealized loss position
Fair Value	656,641	749,513
Unrealized Loss	19,336	27,097
Less than 12 months, Fair Value	476,015	686,113
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	14,149	22,949
12 months or longer, Fair Value	180,626	63,400
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$5,187	$4,148

Investments_Details_5

Investments (Details 5) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Investment Income
Investment fees and expenses	($7,994)	($6,798)	($6,609)
Net investment income	125,557	129,265	136,094
Debt Securities [Member]
Net Investment Income
Interest and Dividend Income, Operating	111,895	122,065	133,088
Equities [Member]
Net Investment Income
Interest and Dividend Income, Operating	10,817	9,454	6,947
Short-term Investments and Other Invested [Member]
Net Investment Income
Interest and Dividend Income, Operating	8,833	2,584	660
Business owned life insurance [Member]
Net Investment Income
Interest and Dividend Income, Operating	$2,006	$1,960	$2,008

Investments_Details_6

Investments (Details 6) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	($1,475)	($71)	($1,566)
Portion of OTTI losses recognized in (reclassified from) other comprehensive income before taxes	-268	0	201
Net impairments recognized in earnings	-1,207	-71	-1,767
Gross realized gains, available-for-sale securities	5,627	18,130	18,645
Gross realized (losses), available-for-sale securities	-1,103	-7,031	-2,076
Net realized gains (losses), trading securities	28,018	20,444	1,485
Net realized gains (losses), Other investments	326	0	0
Change in unrealized holding gains (losses), trading securities	-18,883	35,507	12,673
Change in unrealized holding gains (losses), convertible securities, carried at fair value	1,876	0	0
Decrease (increase) in the fair value of liabilities carried at fair value	0	0	-1,245
Other	0	925	1,148
Total net realized investment gains (losses)	14,654	67,904	28,863
State and municipal bonds [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	-50	-71	0
Residential mortgage-backed securities [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	0	0	-557
Corporate debt [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	-1,425	0	-878
Portion of OTTI losses recognized in (reclassified from) other comprehensive income before taxes	268	0	-201
Other Investments [Member]
Total other-than-temporary impairment losses:
Other-than-temporary impairment (OTTI) losses	$0	$0	($131)

Investments_Details_7

Investments (Details 7) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cumulative credit losses recorded in earnings related to impaired debt securities
Accumulated credit losses related to impaired debt securities, Beginning Balance	$83	$3,301	$5,870
No OTTI has been previously recognized	149	0	0
OTTI has been previously recognized	0	0	268
Securities sold during the period (realized)	0	-3,218	-2,837
Accumulated credit losses related to impaired debt securities, Ending Balance	$232	$83	$3,301

Investments_Details_8

Investments (Details 8) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Information regarding sales and purchases of available-for-sale securities
Proceeds from sales (exclusive of maturities and paydowns)	$244,900,000	$593,300,000	$500,200,000
Purchases	$645,114,000	$519,161,000	$646,198,000

Investments_Details_Textual

Investments (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Affiliate
Schedule of Available-for-sale Securities [Line Items]
Number of investment affiliates exceeding shareholder's equity ten percent threshold limit	0
Threshold limit of investments based on shareholders' equity	10.00%
Securities on deposit with state insurance departments	$49,300,000
Business owned life insurance cost	33,000,000
Investment in unconsolidated subsidiaries	276,501,000	214,236,000
Effect of conversion to equity method, total	10,500,000
Effect of conversion to equity method, prior years	8,400,000
Amortization of operation losses, related to affordable housing tax project tax credits	10,700,000	10,100,000	6,400,000
Tax Credit Partnerships Almost 100% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of tax credit partnerships almost 100% ownership percentage	2
Investment in unconsolidated subsidiaries	58,000,000
Tax Credit Partnerships Less Than 20% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment in unconsolidated subsidiaries	75,100,000
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]
Percentage Ownership	100.00%
Maximum [Member] | Tax Credit Partnerships Less Than 20% Ownership [Member]
Schedule of Available-for-sale Securities [Line Items]
Percentage Ownership	20.00%
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
FAL Deposit assets	85,000,000
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
FAL Deposit assets	200,000
Non Government-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of debt securities in unrealized loss position	588	714
Debt securities in unrealized loss position as percentage of total debt securities held	20.50%	26.30%
Number of issuers in unrealized loss position	434	516
Single greatest unrealized loss position	1,700,000	400,000
Second greatest unrealized loss position	$700,000	$400,000

Reinsurance_Details

Reinsurance (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Summary of the effect of reinsurance on premiums written and earned
Direct premiums written	$761,043		$566,745		$536,318
Premiums earned	755,623	[1]	568,629	[1]	558,200	[1]
Assumed premiums written	18,566		802		113
Premiums assumed	12,987	[1]	804	[1]	116	[1]
Ceded premiums written	-77,760		-42,365		-8,133
Premiums ceded	-68,879	[1]	-41,514	[1]	-7,652	[1]
Premiums written, net	701,849		525,182		528,298
Net premiums earned	$699,731	[1]	$527,919	[1]	$550,664	[1]
[1]	All of ProAssurance’s premiums are related to property and liability coverages.

Reinsurance_Details_Textual

Reinsurance (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	reinsurer
Ceded Credit Risk [Line Items]
Premium ceded reduction amount	$15,700,000	$16,400,000	$34,300,000
Amount due from reinsurers total	259,100,000
Number of major reinsurers	3
Allowance for reinsurance receivables	0	0
Loss on uncollectible accounts in the period	0	0	0
Individual reinsurer balances as percentage of shareholder's equity, maximum	5.00%
Ceded Credit Risk, Secured [Member]
Ceded Credit Risk [Line Items]
Amount of reinsurance recoverables collateralized by letters of credit	35,000,000
Major Reinsurers [Member]
Ceded Credit Risk [Line Items]
Amount due from reinsurers total	66,900,000
Minimum [Member]
Ceded Credit Risk [Line Items]
Major reinsurer threshold	$20,000,000

Income_Taxes_Details

Income Taxes (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets
Unpaid loss discount	$44,002	$51,879
Unearned premium adjustment	23,972	21,861
Compensation related	18,623	18,172
Intangibles	1,957	2,074
Total deferred tax assets	88,554	93,986
Deferred tax liabilities
Deferred acquisition costs	9,180	10,150
Unrealized gains on investments, net	31,342	32,127
Fixed assets	3,689	4,166
Basis differentials–investments	31,657	31,247
Intangibles	27,294	13,238
Other	4,210	1,301
Total deferred tax liabilities	107,372	92,229
Net deferred tax assets (liabilities)	($18,818)	$1,757

Income_Taxes_Details_1

Income Taxes (Details 1) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of unrecognized tax benefits
Balance at January 1	$4,823	$4,823	$18,585
Increase for tax position acquired as result of a business combination	414	0	0
Increases for tax positions taken during the current year	163	0	0
(Decreases) for tax positions taken during the current year	-4,823	0	-10,206
(Decreases) for tax positions taken during prior years	0	0	-3,556
Balance at December 31	$577	$4,823	$4,823

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of expected income tax expense to actual income tax expense
Computed “expected” tax expense	$91,702	$139,005	$138,588
Tax-exempt income	-13,250	-14,509	-14,374
Tax credits, qualified affordable housing	-17,918	-17,888	-10,005
Non-taxable gain on acquisition	0	-11,310	0
Non-U.S. Loss	1,741	0	0
Other	3,165	4,338	6,287
Total income tax expense (benefit)	$65,440	$99,636	$120,496

Income_Taxes_Details_Textual

Income Taxes (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Contingency [Line Items]
Capital loss carryforwards	$0
Amount of available net operating loss (NOL) carryforwards	0
Expected refund from settlement with IRS	30,600,000
Income taxes receivable	1,100,000	27,300,000
Unrecognized tax benefits	577,000	4,823,000	4,823,000	18,585,000
Unrecognized tax benefits interest			500,000
Accrued liability for interest and penalties		1,300,000
Percentage of income before income taxes included in expected income tax expense	35.00%	35.00%	35.00%
Deferred tax assets, alternative minimum tax	$0

Deferred_Policy_Acquisition_Co1

Deferred Policy Acquisition Costs (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Insurance [Abstract]
Amortization of deferred policy acquisition costs	$68.60	$53.20	$54.90

Reserve_for_Losses_and_Loss_Ad2

Reserve for Losses and Loss Adjustment Expenses (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) [Abstract]
Minimum period for claims resolution									5 years
Summary of reserve for losses and loss adjustment expenses
Balance, beginning of year				$2,072,822				$2,054,994	$2,072,822	$2,054,994	$2,247,772
Receivable from reinsurers on unpaid losses and loss adjustment expenses	237,966				247,518				237,966	247,518	191,645	247,658
Net balance, beginning of year				1,825,304				1,863,349	1,825,304	1,863,349	2,000,114
Net reserves acquired from acquisitions									139,549	126,007	22,464
Net losses:
Current year	-124,271	-142,124	-141,126	-137,647	-116,689	-110,987	-109,109	-110,726	-545,168	-447,510	-451,951
Favorable development of reserves established in prior years, net	48,830	42,902	42,213	48,139	81,799	49,350	38,500	53,100	182,084	222,749	272,038
Total									363,084	224,761	179,913
Paid related to:
Current year									-93,737	-43,616	-38,439
Prior years									-413,900	-345,197	-300,703
Total paid									-507,637	-388,813	-339,142
Net balance, end of year	1,820,300				1,825,304				1,820,300	1,825,304	1,863,349
Balance, end of year	$2,058,266				$2,072,822				$2,058,266	$2,072,822	$2,054,994
Liability For unpaid claims and claims adjustment expense incurred claims prior years accident years					2005 through 2011				2007 through 2011		2004 through 2009

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of future minimum lease payments for operating leases
2015	$5,024
2016	4,915
2017	3,601
2018	2,965
2019	2,572
Thereafter	5,232
Total minimum lease payments	$24,309

Commitments_and_Contingencies_2

Commitments and Contingencies (Details Textual)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014
	USD ($)	USD ($)	USD ($)	GBP (£)	Non-Public Equity Funds [Member]	Qualified Affordable Housing Project [Member]	Lloyds Syndicate [Member]
					USD ($)	USD ($)	USD ($)
Other Commitment, Fiscal Year Maturity [Abstract]
Other commitment					$169,400,000	$15,500,000
Other commitment, due in 2015					98,800,000	14,100,000
Other commitment, due in 2016 and 2017					69,200,000	500,000
Other commitment, due in 2018					600,000	300,000
Other commitment, due thereafter					800,000	600,000
FAL Deposit assets							85,200,000
Line of credit extended to Lloyd's Syndicate, lending capacity	16,000,000			10,000,000
Line of credit extended to Lloyd's Syndicate, interest rate	8.50%
Amount receivable under line of credit extended to Lloyd's Syndicate	11,000,000			6,600,000
Rent expense	$5,000,000	$3,200,000	$2,700,000

Longterm_Debt_Details

Long-term Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Outstanding long-term debt
Long-term debt	$250,000,000	$250,000,000
Loss on extinguishment of debt	0	0	2,163,000
Senior notes due 2023 [Member] | Senior Notes [Member]
Outstanding long-term debt
Long-term debt	250,000,000	250,000,000
Interest rate	5.30%
Senior notes due 2023 [Member] | US Treasury Note Rate [Member] | Senior Notes [Member]
Outstanding long-term debt
Variable interest rate of long term debt	0.40%
Revolving credit agreement [Member] | Line of Credit [Member]
Outstanding long-term debt
Long-term debt	0	0
Current Revolving credit capacity	200,000,000
Maximum allowable consolidated funded indebtedness ratio	0.35
Net worth requirement, sum of consolidated net worth	75.00%
Net worth requirement, percentage of consolidated net income earned	50.00%
Net worth requirement, percentage of net cash proceeds from issuance of stock	100.00%
Revolving credit agreement [Member] | Base Rate [Member] | Line of Credit [Member]
Outstanding long-term debt
Description of variable rate basis	base rate
Revolving credit agreement [Member] | Prime Rate [Member] | Line of Credit [Member]
Outstanding long-term debt
Description of variable rate basis	Prime rate
Revolving credit agreement [Member] | Federal Funds Rate [Member] | Line of Credit [Member]
Outstanding long-term debt
Variable interest rate of long term debt	0.50%
Description of variable rate basis	Federal Funds
Revolving credit agreement [Member] | One Month LIBOR [Member] | Line of Credit [Member]
Outstanding long-term debt
Variable interest rate of long term debt	1.00%
Description of variable rate basis	one month LIBOR
Revolving credit agreement [Member] | Minimum [Member] | Line of Credit [Member]
Outstanding long-term debt
Commitment fee percentages	0.15%
Variable interest rate of long term debt	0.00%
Revolving credit agreement [Member] | Maximum [Member] | Line of Credit [Member]
Outstanding long-term debt
Commitment fee percentages	0.30%
Variable interest rate of long term debt	1.88%
Note Payable Due 2019 [Member] | Notes Payable [Member]
Outstanding long-term debt
Loss on extinguishment of debt			$2,200,000

Shareholders_Equity_Shareholde

Shareholders' Equity Shareholders' Equity (Details)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Common Stock Outstanding Rollforward [Roll Forward]
Beginning Balance (in shares)	61,197		61,624		61,107
Repurchase of shares (in shares)	-4,909		-681		0
Shares issued due to exercise of options and vesting of share-based compensation awards (in shares)	154		169		436
Other shares issued as compensation (in shares)	92	[1]	85	[1]	81	[1]
Ending Balance (in shares)	56,534		61,197		61,624
[1]	Shares issued were valued at fair value (the market price of a ProAssurance common share on the date of issue).

Shareholders_Equity_Details_1

Shareholders' Equity (Details 1) (USD $)

3 Months Ended

12 Months Ended

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Class of Stock [Line Items]

Cash dividends declared per common share (USD per share)

$2.96

[1]

$0.30

$0.30

$0.30

$0.30

[1]

$0.25

$0.25

$0.25

$2.75

[1]

$0.13

$0.13

$0.13

$3.86

$1.05

$3.13

Dividends Declared, Special [Member]

Class of Stock [Line Items]

Cash dividends declared per common share (USD per share)

$2.65

$2.50

[1]

* Includes special dividends of $2.65 per share in 2014 and $2.50 per share in 2012.

Shareholders_Equity_Details_2

Shareholders' Equity (Details 2) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification adjustments related to available-for-sale securities
Net realized gains (losses)									$14,654	$67,904	$28,863
Total amounts reclassified, before tax effect									262,005	397,159	395,966
Tax effect (at 35%)									-65,440	-99,636	-120,496
Net income	65,114	34,778	49,942	46,731	70,864	63,357	50,451	112,850	196,565	297,523	275,470
Other Comprehensive Income (Loss), Tax									-785	-46,157	8,262
Reclassifications from accumulated other comprehensive income to net income, available for sale securities [Member]
Reclassification adjustments related to available-for-sale securities
Total amounts reclassified, before tax effect									3,317	11,028	14,933
Tax effect (at 35%)									-1,161	-3,860	-5,227
Net income									2,156	7,168	9,706
Reclassifications from accumulated other comprehensive income to net income, available for sale securities [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification adjustments related to available-for-sale securities
Net realized gains (losses)									3,317	11,375	17,350
Reclassifications from accumulated other comprehensive income to net income, available for sale securities [Member] | Accumulated Other-than-Temporary Impairment [Member]
Reclassification adjustments related to available-for-sale securities
Net realized gains (losses)									$0	($347)	($2,417)

Shareholders_Equity_Details_Te

Shareholders' Equity (Details Textual) (USD $)	3 Months Ended															12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares authorized (in shares)	100,000,000					100,000,000										100,000,000	100,000,000
Authorized preferred stock (in shares)	50,000,000					50,000,000										50,000,000	50,000,000
Dividends declared																$220,500,000	$64,800,000	$192,500,000
Equity attributable to parent	2,157,944,000					2,394,414,000					2,270,580,000					2,157,944,000	2,394,414,000	2,270,580,000	2,164,453,000
Total authorizations which remain available for use (in shares)	181,500,000															181,500,000
Repurchased common shares (in shares)																4,909,000	681,000	0
Authorization common shares for the issuance under incentive compensation plans (in shares)	2,680,075															2,680,075
Number of shares available for grant (in shares)	796,933															796,933
Impairment losses in accumulated other comprehensive income	800,000					500,000										800,000	500,000
Percentage of income before income taxes included in expected income tax expense																35.00%	35.00%	35.00%
Quarterly dividend declared, per share (USD per share)	$2.96	[1]	$0.30	$0.30	$0.30	$0.30	[1]	$0.25	$0.25	$0.25	$2.75	[1]	$0.13	$0.13	$0.13	$3.86	$1.05	$3.13
Retained Earnings, Unappropriated [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity attributable to parent	$239,000,000															$239,000,000
[1]	* Includes special dividends of $2.65 per share in 2014 and $2.50 per share in 2012.

ShareBased_Payments_Details

Share-Based Payments (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of compensation expense and related tax benefit recognized during each period and compensation cost expense in future periods
Share-based compensation expense	$10,056,000	$9,242,000	$8,639,000
Tax benefit recognized	3,500,000	3,200,000	3,000,000
Unrecognized Compensation Cost, Amount	9,900,000
Restricted Stock Units (RSUs) [Member]
Summary of compensation expense and related tax benefit recognized during each period and compensation cost expense in future periods
Share-based compensation expense	1,700,000	1,600,000	1,600,000
Unrecognized Compensation Cost, Amount	2,000,000
Unrecognized Compensation Cost, remaining recognition period	1 year 9 months 18 days
Performance Shares Units [Member]
Summary of compensation expense and related tax benefit recognized during each period and compensation cost expense in future periods
Share-based compensation expense	7,600,000	7,100,000	6,700,000
Unrecognized Compensation Cost, Amount	6,300,000
Unrecognized Compensation Cost, remaining recognition period	1 year 8 months 12 days
Employee Purchase Plan [Member]
Summary of compensation expense and related tax benefit recognized during each period and compensation cost expense in future periods
Share-based compensation expense	800,000	500,000	300,000
Unrecognized Compensation Cost, Amount	$1,600,000
Unrecognized Compensation Cost, remaining recognition period	2 years 2 months 12 days

ShareBased_Payments_Details_1

Share-Based Payments (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of activity for stock options
Stock Options, Outstanding, Beginning of the year (in shares)	18,082	20,302	1,014,661
Stock Options, Outstanding, Granted (in shares)	0	0	0
Stock Options, Outstanding, Exercised (in shares)	-13,626	-2,220	-994,148
Stock Options, Outstanding, Forfeited or Expired (in shares)	0	0	-211
Stock Options, Outstanding, Ending of the year (in shares)	4,456	18,082	20,302
Stock Options, Outstanding, Exercisable at end of year (in shares)	4,456	18,082	20,302
Stock Options, Outstanding at end of year, Vested or Expected to Vest (in shares)	4,456	18,082	20,302
Summary of activity for stock options, weighted average exercise price
Stock Options, Outstanding, Weighted Average Exercise Price, Beginning of the year (USD per share)	$23	$23.15	$22.76
Stock Options, Outstanding, Weighted Average Exercise Price, Granted (USD per share)	$0	$0	$0
Stock Options, Outstanding, Weighted Average Exercise Price ,Exercised (USD per share)	$22.47	$24.28	$22.75
Stock Options, Outstanding, Weighted Average Exercise Price, Forfeited and Expired (USD per share)	$0	$0	$25.67
Stock Options, Outstanding, Weighted Average Exercise Price, End of the Period (USD per share)	$24.64	$23	$23.15
Stock Options, Outstanding, Weighted Average Exercise Price, Exercisable (USD per share)	$24.64	$23	$23.15
Stock Options, Outstanding at end of year, Weighted Average Exercise Price, vested or expected to vest (USD per share)	$24.64	$23	$23.15

ShareBased_Payments_Details_2

Share-Based Payments (Details 2) (Restricted Stock Units (RSUs) [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock Units (RSUs) [Member]
Summary Activity for restricted share units, number of shares
Beginning non-vested balance (in shares)	138,770	157,212	167,236
Granted (in shares)	49,750	39,400	51,864
Forfeited (in shares)	-2,044	-603	-2,823
Vested (in shares)	-49,674	-57,239	-59,065
Ending non-vested balance (in shares)	136,802	138,770	157,212
Summary Activity for restricted share units, weighted average grant date fair value
Beginning balance, weighted average grant date fair value per share (USD per share)	$38.92	$31.94	$25.52
Granted, weighted average grant date fair value per share (USD per share)	$46.34	$46.97	$42.22
Forfeited, weighted average grant date fair value per share (USD per share)	$44.88	$35.91	$35.23
Vested and released, weighted average grant date fair value per share (USD per share)	$29.22	$25.25	$22.61
Ending balance, weighted average grant date fair value per share (USD per share)	$45.02	$38.92	$31.94

ShareBased_Payments_Details_3

Share-Based Payments (Details 3) (Performance Shares Units [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Performance Shares Units [Member]
Summary Activity for restricted share units, number of shares
Beginning non-vested balance (in shares)	486,680	552,417	522,599
Granted (in shares)	160,900	145,580	212,205
Forfeited (in shares)	-14,221	-17,043	-20,492
Vested (in shares)	-166,499	-194,274	-161,895
Ending non-vested balance (in shares)	466,860	486,680	552,417
Summary Activity for restricted share units, weighted average grant date fair value
Beginning balance, weighted average grant date fair value per share (USD per share)	$39.86	$33.21	$26.36
Granted, weighted average grant date fair value per share (USD per share)	$46.34	$46.97	$42.22
Forfeited, weighted average grant date fair value per share (USD per share)	$45.30	$38.90	$31.44
Vested and released, weighted average grant date fair value per share (USD per share)	$31.33	$26.39	$23.13
Ending balance, weighted average grant date fair value per share (USD per share)	$44.97	$39.86	$33.21

Share_Based_Payments_Details_4

Share Based Payments (Details 4) (Employee Purchase Plan [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Purchase Plan [Member]
Summary Activity for restricted share units, number of shares
Beginning non-vested balance (in shares)	63,125	40,985	18,900
Granted (in shares)	29,069	25,151	23,799
Forfeited (in shares)	-2,968	-2,456	-1,610
Vested (in shares)	-17,125	-555	-104
Ending non-vested balance (in shares)	72,101	63,125	40,985
Summary Activity for restricted share units, weighted average grant date fair value
Beginning balance, weighted average grant date fair value per share (USD per share)	$41.34	$39.85	$36.20
Granted, weighted average grant date fair value per share (USD per share)	$44.55	$43.57	$42.59
Forfeited, weighted average grant date fair value per share (USD per share)	$43.14	$40.71	$37.72
Vested and released, weighted average grant date fair value per share (USD per share)	$36.61	$36.33	$36.20
Ending balance, weighted average grant date fair value per share (USD per share)	$43.69	$41.34	$39.85

ShareBased_Payments_Details_Te

Share-Based Payments (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Award_Type
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of award types	4
Aggregate grant date fair value of options vested in period			$900,000
The aggregate grant date intrinsic value of options exercised	300,000	100,000	19,800,000
Aggregate intrinsic value of stock options outstanding	100,000
Weighted average remaining contractual term of stock options	2 years 5 months 8 days
Cash proceeds from stock option exercises	0	0	0
Performance Shares Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average period	3 years
The aggregate grant date fair value of Employee awards	5,200,000	5,100,000	3,700,000
The percentage of award vest	125.00%
Aggregate intrinsic value	7,700,000	9,100,000	7,200,000
Management Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average period	3 years
The aggregate grant date fair value of Employee awards	1,500,000	1,400,000	1,300,000
Aggregate intrinsic value	2,300,000	2,700,000	2,600,000
Employee Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average period	3 years
The aggregate grant date fair value of Employee awards	600,000
Aggregate intrinsic value	800,000
Annual contribution for the purchase of shares	$5,000
Minimum [Member] | Performance Shares Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
The percentage of award vest	75.00%
Maximum [Member] | Performance Shares Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
The percentage of award vest	125.00%

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (Variable Interest Entity, Not Primary Beneficiary [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Investments [Member]
Variable Interest Entity [Line Items]
Variable interest entity nonconsolidated assets	$33.30	$27.30
Variable interest entity, maximum loss exposure	33.3
Equity Method Investments [Member]
Variable Interest Entity [Line Items]
Variable interest entity nonconsolidated assets	65	49.5
Variable interest entity, maximum loss exposure	$65

Segment_Information_Details_Te

Segment Information (Details Textual)	12 Months Ended
	Dec. 31, 2014
	Segment
Segment Reporting Information [Line Items]
Number of operating segments	4
Workers Compensation [Member]
Segment Reporting Information [Line Items]
Alternative market solutions percentage ceded	100.00%
Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Proportion of capital provided to support lloyd's syndicate	58.00%

Segment_Information_Details_1

Segment Information (Details 1) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net premiums earned	$174,670	$177,028	$176,303	$171,730	$129,392	$133,598	$130,352	$134,578	$699,731	$527,919	$550,664
Net investment income									125,557	129,265	136,094
Equity in earnings (loss) of unconsolidated subsidiaries									3,986	7,539	-6,873
Net realized gains (losses)									14,654	67,904	28,863
Other income (loss)									8,398	7,551	7,106
Gain on acquisition									0	32,314	0
Net losses and loss adjustment expenses									-363,084	-224,761	-179,913
Underwriting, policy acquisition and operating expenses									-211,311	-147,817	-135,631
Segregated portfolio cells dividend expense									-1,842	0	0
Interest expense									-14,084	-2,755	-2,181
Loss (gain) on extinguishment of debt									0	0	-2,163
Tax effect (at 35%)									-65,440	-99,636	-120,496
Segment operating results									196,565	297,523	275,470
Depreciation and amortization									50,323	45,967	37,573
Net income	65,114	34,778	49,942	46,731	70,864	63,357	50,451	112,850	196,565	297,523	275,470
Specialty Property and Casualty [Member]
Segment Reporting Information [Line Items]
Net premiums earned									492,733	527,919	550,664
Other income (loss)									5,823	5,648	5,331
Gain on acquisition											0
Net losses and loss adjustment expenses									-228,199	-224,761	-179,913
Underwriting, policy acquisition and operating expenses									-133,132	-132,076	-125,292
Segment operating results									137,225	176,730	250,790
Depreciation and amortization									8,945	7,199	7,355
Workers Compensation [Member]
Segment Reporting Information [Line Items]
Net premiums earned									194,540	0	0
Other income (loss)									645	0	0
Net losses and loss adjustment expenses									-126,447	0	0
Underwriting, policy acquisition and operating expenses									-60,357	0	0
Segregated portfolio cells dividend expense									-1,842
Segment operating results									6,539	0	0
Depreciation and amortization									5,828	0	0
Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Net premiums earned									12,458	0	0
Net investment income									410	0	0
Net realized gains (losses)									4
Other income (loss)									126
Net losses and loss adjustment expenses									-8,438
Underwriting, policy acquisition and operating expenses									-9,535	0	0
Segment operating results									-4,975	0	0
Depreciation and amortization									477	0	0
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Net premiums earned											0
Net investment income									125,147	129,265	136,094
Equity in earnings (loss) of unconsolidated subsidiaries									3,986	7,539	-6,873
Net realized gains (losses)									14,650	67,904	28,863
Other income (loss)									2,285	1,910	1,825
Gain on acquisition										32,314
Underwriting, policy acquisition and operating expenses									-8,768	-15,748	-10,389
Interest expense									-14,084	-2,755	-2,181
Loss (gain) on extinguishment of debt											-2,163
Tax effect (at 35%)									-65,440	-99,636	-120,496
Segment operating results									57,776	120,793	24,680
Depreciation and amortization									35,073	38,768	30,218
Inter-segment Eliminations [Member]
Segment Reporting Information [Line Items]
Other income (loss)									-481	-7	-50
Underwriting, policy acquisition and operating expenses									481	7	50
Segment operating results									0	0	0
Depreciation and amortization											$0

Segment_Information_Details_2

Segment Information (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
Premiums ceded									($68,879,000)	[1]	($41,514,000)	[1]	($7,652,000)	[1]
Net premiums earned	174,670,000	177,028,000	176,303,000	171,730,000	129,392,000	133,598,000	130,352,000	134,578,000	699,731,000		527,919,000		550,664,000
Specialty Property and Casualty [Member]
Segment Reporting Information [Line Items]
Premiums ceded									-50,319,000		-41,514,000		-7,652,000
Net premiums earned									492,733,000		527,919,000		550,664,000
Premiums ceded to lloyd's syndicate segment									4,200,000
Workers Compensation [Member]
Segment Reporting Information [Line Items]
Premiums ceded									-21,793,000		0		0
Net premiums earned									194,540,000		0		0
Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Premiums ceded									-971,000		0		0
Net premiums earned									12,458,000		0		0
Healthcare Professional Liability [Member] | Specialty Property and Casualty [Member]
Segment Reporting Information [Line Items]
Gross premiums earned:									477,031,000		507,222,000		539,729,000
Legal Professional Liability [Member] | Specialty Property and Casualty [Member]
Segment Reporting Information [Line Items]
Gross premiums earned:									28,278,000		27,162,000		17,042,000
Medical Technology and Life Sciences Product Liability [Member] | Specialty Property and Casualty [Member]
Segment Reporting Information [Line Items]
Gross premiums earned:									35,913,000		33,242,000		0
Other Premiums [Member] | Specialty Property and Casualty [Member]
Segment Reporting Information [Line Items]
Gross premiums earned:									1,830,000		1,807,000		1,545,000
Workers' Compensation Traditional Business [Member] | Workers Compensation [Member]
Segment Reporting Information [Line Items]
Gross premiums earned:									160,717,000		0		0
Workers' Compensation Alternative Market Business [Member] | Workers Compensation [Member]
Segment Reporting Information [Line Items]
Gross premiums earned:									55,616,000		0		0
Property, Liability and Casualty Insurance Product Line [Member] | Lloyds Syndicate [Member]
Segment Reporting Information [Line Items]
Gross premiums earned:									$13,429,000	[2]	$0		$0
[1]	All of ProAssurance’s premiums are related to property and liability coverages.
[2]	Includes premium ceded from the Specialty P&C Segment to the Lloyd's Syndicate Segment of $4.2 million for year ended December 31, 2014.

Benefit_Plans_Details

Benefit Plans (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Contribution Plan Disclosure [Line Items]
Incurred expense related to savings and retirement plans	$6	$5.10	$4.60
Incurred expense related to non qualified deferred compensation plans	0.3	0.4	0.4
ProAssurance deferred compensation liabilities total	$14	$13.10
Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of benefit plan contribution by employer	5.00%
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of benefit plan contribution by employer	10.00%

Statutory_Accounting_and_Divid2

Statutory Accounting and Dividend Restrictions (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Net Income Related to Statutory Accounting
Statutory Net Earnings	$246,000,000	$256,000,000	$312,000,000
Statutory Capital and Surplus	1,681,000,000	1,642,000,000
Statutory Capital and Surplus	1,900,000,000
Dividend payments from insurance subsidiaries	$230,000,000

Quarterly_Results_of_Operation2

Quarterly Results of Operations (Unaudited) (Details) (USD $)	3 Months Ended																12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of unaudited quarterly results of operations
Net premiums earned	$174,670		$177,028		$176,303		$171,730		$129,392		$133,598		$130,352		$134,578		$699,731	$527,919	$550,664
Net losses and loss adjustment expenses:
Current year	124,271		142,124		141,126		137,647		116,689		110,987		109,109		110,726		545,168	447,510	451,951
Favorable development of reserves established in prior years, net	48,830		42,902		42,213		48,139		81,799		49,350		38,500		53,100		182,084	222,749	272,038
Net income	$65,114		$34,778		$49,942		$46,731		$70,864		$63,357		$50,451		$112,850		$196,565	$297,523	$275,470
Basic earnings per share (USD per share)	$1.13	[1]	$0.59	[1]	$0.84	[1]	$0.76	[1]	$1.15	[1]	$1.02	[1]	$0.82	[1]	$1.83	[1]	$3.32	$4.82	$4.49
Diluted earnings per share (USD per share)	$1.12	[1]	$0.59	[1]	$0.84	[1]	$0.76	[1]	$1.14	[1]	$1.02	[1]	$0.81	[1]	$1.82	[1]	$3.30	$4.80	$4.46
[1]	Quarterly and year-to-date computations of per share amounts are made independently; therefore, the sum of per share amounts for the quarters may not equal per share amounts for the respective year-to-date periods.

Subsequent_Events_Details

Subsequent Events (Details) (Revolving Credit Facility [Member], Subsequent Event [Member], USD $)	1 Months Ended
In Millions, unless otherwise specified	Jan. 31, 2015
Revolving Credit Facility [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Draw on line of credit	$100

Schedule_I_Summary_of_Investme1

Schedule I - Summary of Investments-Other Than Investments In Related Parties (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	$3,888,782
Total Investments, Fair value	4,012,423
Total Investments, Amount which is presented in the balance sheet	4,009,707
U.S. Government or government agencies and authorities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	201,736
Total Investments, Fair value	206,075
Total Investments, Amount which is presented in the balance sheet	206,075
States, municipalities and political subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	1,015,555
Total Investments, Fair value	1,062,615
Total Investments, Amount which is presented in the balance sheet	1,062,615
Foreign Governments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	2,709
Total Investments, Fair value	2,871
Total Investments, Amount which is presented in the balance sheet	2,871
Public utilities bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	80,086
Total Investments, Fair value	83,668
Total Investments, Amount which is presented in the balance sheet	83,668
All other corporate bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	1,307,025
Total Investments, Fair value	1,330,412
Total Investments, Amount which is presented in the balance sheet	1,330,412
Certificates of deposit [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	150
Total Investments, Fair value	150
Total Investments, Amount which is presented in the balance sheet	150
Mortgage-backed securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	448,216
Total Investments, Fair value	459,236
Total Investments, Amount which is presented in the balance sheet	459,236
Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	3,055,477
Total Investments, Fair value	3,145,027
Total Investments, Amount which is presented in the balance sheet	3,145,027
Public utilities equity, trading [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	6,559
Total Investments, Fair value	7,981
Total Investments, Amount which is presented in the balance sheet	7,981
Banks, trusts and insurance companies, trading [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	75,171
Total Investments, Fair value	79,341
Total Investments, Amount which is presented in the balance sheet	79,341
Industrial, miscellaneous and all other, trading [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	201,377
Total Investments, Fair value	227,160
Total Investments, Amount which is presented in the balance sheet	227,160
Total Equity Securities, trading [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	283,107
Total Investments, Fair value	314,482
Total Investments, Amount which is presented in the balance sheet	314,482
Other long-term investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	418,939
Total Investments, Fair value	421,655
Total Investments, Amount which is presented in the balance sheet	418,939
Short-term Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total Investments, Recorded cost basis	131,259
Total Investments, Fair value	131,259
Total Investments, Amount which is presented in the balance sheet	$131,259

Schedule_II_Condensed_Financia1

Schedule II - Condensed Financial Information of Registrant (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Assets
Fixed maturities available for sale, at fair value	$3,145,027	$3,118,049
Equity securities, trading, at fair value	314,482	253,541
Short-term investments	131,259	248,605
Cash and cash equivalents	197,040	129,383	118,551	130,400
Restricted cash	0	78,000
Other assets	93,263	329,979
Total Assets	5,169,160	5,150,099
Liabilities
Other liabilities	320,853	143,079
Long-term debt	250,000	250,000
Total Liabilities	3,011,216	2,755,685
Shareholders’ Equity:
Common stock	623	621
Total Shareholders’ Equity	2,157,944	2,394,414	2,270,580	2,164,453
Total Liabilities and Shareholders’ Equity	5,169,160	5,150,099
Parent Company [Member]
Assets
Investment in subsidiaries, at equity	2,145,358	1,996,721
Fixed maturities available for sale, at fair value	203,451	86,603
Equity securities, trading, at fair value	0	12,043
Short-term investments	42,790	191,991
Cash and cash equivalents	87,200	37,459	29,397	47,938
Restricted cash	0	78,000
Due from subsidiaries	87,719	12,014
Other assets	25,736	255,313
Total Assets	2,592,254	2,670,144
Liabilities
Other liabilities	184,310	25,730
Long-term debt	250,000	250,000
Total Liabilities	434,310	275,730
Shareholders’ Equity:
Common stock	623	621
Other shareholders’ equity, including unrealized gains (losses) on securities of subsidiaries	2,157,321	2,393,793
Total Shareholders’ Equity	2,157,944	2,394,414
Total Liabilities and Shareholders’ Equity	$2,592,254	$2,670,144

Schedule_II_Condensed_Financia2

Schedule II - Condensed Financial Information of Registrant (Details 1) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Net investment income									$125,557	$129,265	$136,094
Equity in earnings (loss) of unconsolidated subsidiaries									3,986	7,539	-6,873
Other income (loss)									8,398	7,551	7,106
Total revenues									852,326	740,178	715,854
Expenses
Interest expense									14,084	2,755	2,181
Total expenses									590,321	375,333	319,888
Income tax expense (benefit)									65,440	99,636	120,496
Net income	65,114	34,778	49,942	46,731	70,864	63,357	50,451	112,850	196,565	297,523	275,470
Other comprehensive income									-1,457	-85,719	15,343
Comprehensive income									195,108	211,804	290,813
Parent Company [Member]
Revenues
Net investment income									3,295	5,789	5,281
Equity in earnings (loss) of unconsolidated subsidiaries									0	0	-728
Net realized investment gains (losses)									990	5,334	3,230
Other income (loss)									660	170	54
Total revenues									4,945	11,293	7,837
Expenses
Interest expense									14,084	2,747	1,534
Other expenses									7,083	13,213	8,870
Total expenses									21,167	15,960	10,404
Income (loss) before income tax expense (benefit) and equity in net income of consolidated subsidiaries									-16,222	-4,667	-2,567
Income tax expense (benefit)									-6,728	-1,007	773
Income (loss) before equity in net income of consolidated subsidiaries									-9,494	-3,660	-3,340
Equity in net income of consolidated subsidiaries									206,059	301,183	278,810
Net income									196,565	297,523	275,470
Other comprehensive income									-1,457	-85,719	15,343
Comprehensive income									$195,108	$211,804	$290,813

Schedule_II_Condensed_Financia3

Schedule II - Condensed Financial Information of Registrant (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided (used) by operating activities	$96,002	$38,602	$91,250
Purchases of:
Equity securities trading	-119,865	-87,604	-120,555
Proceeds from sale or maturities of:
Fixed maturities, available for sale	703,828	970,708	926,221
Equity securities trading	134,005	123,645	54,670
Net decrease (increase) in short-term investments	140,411	-176,092	48,565
(Increase) decrease in restricted cash	78,000	-78,000	0
Funds at Lloyd's in support of Syndicate 1729, returned (deposited)	8,690	-8,699	0
Other	-4,390	-9,909	-4,409
Net cash provided (used) by investing activities	266,980	-67,803	26,843
Financing Activities
Proceeds from long-term debt	0	250,000	125,000
Principal repayment of debt	0	-127,183	-57,660
Repurchase of common stock	-222,360	-29,089	0
Excess of tax benefit from share-based payment arrangements	2,702	2,128	7,022
Dividends to shareholders	-71,252	-46,375	-200,118
Other	-4,415	-9,448	-4,186
Net cash provided (used) by financing activities	-295,325	40,033	-129,942
Increase (decrease) in cash and cash equivalents	67,657	10,832	-11,849
Cash and cash equivalents at beginning of period	129,383	118,551	130,400
Cash and cash equivalents at end of period	197,040	129,383	118,551
Supplemental Disclosure of Cash Flow Information
Cash paid during the year for income taxes, net of refunds	26,061	117,107	110,278
Cash paid during the year for interest	13,408	913	2,342
Significant non-cash transactions:
Unpaid dividends	167,744	18,532	0
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided (used) by operating activities	20,086	-24,654	3,601
Purchases of:
Equity securities trading	-310	-1,265	-364
Proceeds from sale or maturities of:
Fixed maturities, available for sale	104,844	224,993	150,192
Equity securities trading	12,813	1,113	616
Net decrease (increase) in short-term investments	149,202	-187,625	58,657
Dividends from subsidiaries	67,188	239,484	59,369
Contribution of capital to subsidiaries	-7,000	0	-184,330
Cash paid for acquisitions, net of cash received	0	-205,244	0
(Increase) decrease in restricted cash	78,000	-78,000	0
Funds at Lloyd's in support of Syndicate 1729, returned (deposited)	-76,553	-8,699	0
Funds advanced under Syndicate 1729 credit agreement	9,107	1,665	0
Other	415	-20	-1
Net cash provided (used) by investing activities	319,492	-16,928	84,139
Financing Activities
Proceeds from long-term debt	0	250,000	125,000
Principal repayment of debt	0	-125,000	-32,992
Repurchase of common stock	-222,360	-29,089	0
Subsidiary payments for common shares and share-based compensation awarded to subsidiary employees	8,301	6,258	7,066
Excess of tax benefit from share-based payment arrangements	1,631	2,128	7,022
Dividends to shareholders	-70,490	-46,375	-200,118
Other	-6,919	-8,278	-12,259
Net cash provided (used) by financing activities	-289,837	49,644	-106,281
Increase (decrease) in cash and cash equivalents	49,741	8,062	-18,541
Cash and cash equivalents at beginning of period	37,459	29,397	47,938
Cash and cash equivalents at end of period	87,200	37,459	29,397
Significant non-cash transactions:
Unpaid dividends	167,744	18,532	0
Securities transferred at fair value as dividends from subsidiaries	$227,412	$69,011	$241,081

Schedule_II_Condensed_Financia4

Schedule II - Condensed Financial Information of Registrant (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2013
Outstanding long-term debt
Long-term debt	$250,000,000		$250,000,000
Parent Company [Member]
Outstanding long-term debt
Long-term debt	250,000,000		250,000,000
Payments to Acquire Additional Interest in Subsidiaries	7,000,000	184,300,000
Senior Notes [Member] | Senior notes due 2023 [Member]
Outstanding long-term debt
Long-term debt	250,000,000		250,000,000
Interest rate	5.30%
Senior Notes [Member] | Senior notes due 2023 [Member] | Parent Company [Member]
Outstanding long-term debt
Long-term debt	250,000,000		250,000,000
Interest rate	5.30%
Line of Credit [Member] | Revolving Credit Facility [Member]
Outstanding long-term debt
Long-term debt	0		0
Line of Credit [Member] | Revolving Credit Facility [Member] | Parent Company [Member]
Outstanding long-term debt
Long-term debt	$0		$0

Schedule_II_Condensed_Financia5

Schedule II - Condensed Financial Information of Registrant (Details Textual)

12 Months Ended

0 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Jan. 01, 2014

Dec. 31, 2014

Jan. 01, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2014

Jan. 01, 2014

Jan. 01, 2014

Dec. 31, 2013

USD ($)

USD ($)

GBP (£)

Eastern Insurance Holdings [Member]

Eastern Insurance Holdings [Member]

Eastern Insurance Holdings [Member]

Parent Company [Member]

Parent Company [Member]

Parent Company [Member]

Parent Company [Member]

Parent Company [Member]

Parent Company [Member]

Parent Company [Member]

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

GBP (£)

Eastern Insurance Holdings [Member]

Eastern Insurance Holdings [Member]

Eastern Insurance Holdings [Member]

USD ($)

USD ($)

Voting interests acquired

100.00%

100.00%

Total purchase consideration

$205,000,000

$205,243,000

$205,000,000

Third party conversion agent asset

205,000,000

205,000,000

Dividends paid to parent company by consolidated subsidiaries

294,600,000

308,500,000

300,500,000

Capital contribution

7,000,000

184,300,000

Funds at lloyd's In support of syndicate 1729, advanced from subsidiary

-76,600,000

-8,700,000

Line of credit extended to Lloyd's Syndicate, lending capacity

16,000,000

10,000,000

16,000,000

10,000,000

Amount receivable under line of credit extended to Lloyd's Syndicate

$11,000,000

£ 6,600,000

$11,000,000

£ 6,600,000

Schedule_III_Supplementary_Ins1

Schedule III - Supplementary Insurance Information (Details) (USD $)	3 Months Ended										12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Supplementary Insurance Information, by Segment [Line Items]
Net premiums earned											$699,731		$527,919		$550,664
Net investment income											125,557	[1]	129,265	[1]	136,094	[1]
Losses and loss adjustment expenses incurred related to current year, net of reinsurance	124,271		142,124	141,126	137,647	116,689		110,987	109,109	110,726	545,168		447,510		451,951
Losses and loss adjustment expenses incurred related to prior year, net of reinsurance	-48,830		-42,902	-42,213	-48,139	-81,799		-49,350	-38,500	-53,100	-182,084		-222,749		-272,038
Paid losses and loss adjustment expenses, net of reinsurance											507,637		388,813		339,142
Underwriting, policy acquisition and operating expenses:											68,577		53,207		54,887
Other underwriting, policy acquisition and operating expenses											142,734	[2]	94,610	[2]	80,744	[2]
Net premiums written											701,849		525,182		528,298
Deferred policy acquisition costs	38,790	[1]				28,207	[1]				38,790	[1]	28,207	[1]	23,179	[1]
Reserve for losses and loss adjustment expenses	2,058,266	[1]				2,072,822	[1]				2,058,266	[1]	2,072,822	[1]	2,054,994	[1]
Unearned premiums	345,828	[1]				255,463	[1]				345,828	[1]	255,463	[1]	233,861	[1]
Specialty Property and Casualty [Member]
Supplementary Insurance Information, by Segment [Line Items]
Net premiums earned											492,733		527,919		550,664
Losses and loss adjustment expenses incurred related to current year, net of reinsurance											408,987		447,510		451,951
Losses and loss adjustment expenses incurred related to prior year, net of reinsurance											-180,788		-222,749		-272,038
Paid losses and loss adjustment expenses, net of reinsurance											389,458		388,813		339,142
Underwriting, policy acquisition and operating expenses:											55,105		53,207		54,887
Other underwriting, policy acquisition and operating expenses											78,027		78,869		70,405
Net premiums written											467,046		525,182		528,298
Workers Compensation [Member]
Supplementary Insurance Information, by Segment [Line Items]
Net premiums earned											194,540		0		0
Losses and loss adjustment expenses incurred related to current year, net of reinsurance											127,743		0		0
Losses and loss adjustment expenses incurred related to prior year, net of reinsurance											-1,296		0		0
Paid losses and loss adjustment expenses, net of reinsurance											117,775		0		0
Underwriting, policy acquisition and operating expenses:											10,307		0		0
Other underwriting, policy acquisition and operating expenses											50,050		0		0
Net premiums written											202,697		0		0
Lloyds Syndicate [Member]
Supplementary Insurance Information, by Segment [Line Items]
Net premiums earned											12,458		0		0
Net investment income											410	[1]	0	[1]	0	[1]
Losses and loss adjustment expenses incurred related to current year, net of reinsurance											8,438		0		0
Losses and loss adjustment expenses incurred related to prior year, net of reinsurance											0		0		0
Paid losses and loss adjustment expenses, net of reinsurance											404		0		0
Underwriting, policy acquisition and operating expenses:											3,165		0		0
Other underwriting, policy acquisition and operating expenses											6,370		0		0
Net premiums written											32,106		0		0
Corporate Segment [Member]
Supplementary Insurance Information, by Segment [Line Items]
Net investment income											125,147	[1]	129,265	[1]	136,094	[1]
Other underwriting, policy acquisition and operating expenses											$8,768		$15,748		$10,389
[1]	Assets are not allocated to segments because investments and assets are not managed at the segment level, with the exceptionof the FAL investments held at our Lloyd's Syndicate segment.
[2]	Includes Inter-segment eliminations.

Schedule_IV_Reinsurance_Detail

Schedule IV - Reinsurance (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Property and Liability
Premiums earned	$755,623	[1]	$568,629	[1]	$558,200	[1]
Premiums ceded	-68,879	[1]	-41,514	[1]	-7,652	[1]
Premiums assumed	12,987	[1]	804	[1]	116	[1]
Net premiums earned	$699,731	[1]	$527,919	[1]	$550,664	[1]
Percentage of amount assumed to net	1.86%	[1]	0.15%	[1]	0.02%	[1]
[1]	All of ProAssurance’s premiums are related to property and liability coverages.