W. R. Berkley (WRB) 10-Q 5 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Informatio

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 02, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	BERKLEY W R CORP
Entity Central Index Key	11,544
Current Fiscal Year End Date	--03-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		121,228,108

Consolidated Balance Sheet Cons

Consolidated Balance Sheet Consolidated Balance Sheet - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets [Abstract]
Fixed maturity securities	$ 13,422,979	$ 13,190,668
Loans receivable	611,378	669,200
Equity securities available for sale	753,278	299,999
Investment funds	1,238,558	1,198,146
Loans receivable	103,650	106,798
Real estate	1,237,738	1,184,981
Total investments	17,367,581	16,649,792
Cash and cash equivalents	608,393	795,285
Premiums and fees receivable	1,766,478	1,701,854
Due from reinsurers	1,640,190	1,743,980
Prepaid reinsurance premiums	451,886	413,140
Trading account receivables from brokers and clearing organizations	29,131	484,593
Deferred policy acquisition costs	544,914	537,890
Property, furniture and equipment	356,908	349,432
Goodwill	144,513	144,513
Accrued investment income	135,439	127,047
Other assets	501,981	402,550
Total assets	23,547,414	23,350,076
Liabilities:
Reserves for losses and loss expenses	11,224,324	11,197,195
Unearned premiums	3,402,892	3,283,300
Due to reinsurers	218,040	213,128
Trading account securities sold but not yet purchased	51,348	51,179
Deferred Tax Liabilities, Net, Current	169,959	119,597
Other liabilities	775,039	916,318
Subordinated debentures	727,777	727,630
Senior notes and other debt	1,759,494	1,760,595
Total liabilities	18,328,873	18,268,942
Equity:
Authorized 5,000,000 shares; issued and outstanding - none	0	0
Authorized 500,000,000 shares, issued and outstanding, net of treasury shares, 121,218,479 and 121,193,599 shares, respectively	47,024	47,024
Additional paid-in capital	1,047,589	1,037,446
Retained earnings	6,703,675	6,595,987
Accumulated other comprehensive income	69,491	55,568
Treasury stock, at cost, 113,899,439 and 113,924,319 shares, respectively	2,688,173	2,688,817
Total stockholders’ equity	5,179,606	5,047,208
Noncontrolling interests	38,935	33,926
Total equity	5,218,541	5,081,134
Total liabilities and equity	$ 23,547,414	$ 23,350,076

Consolidated Balance Sheet Con3

Consolidated Balance Sheet Consolidated Balance Sheet (Parenthetical) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value $.10 per share:	$ 0.1	$ 0.1
Preferred shares authorized	5,000,000	5,000,000
Preferred shares issued	0	0
Preferred shares outstanding	0	0
Common stock, par value $.20 per share:	$ 0.2	$ 0.2
Common shares authorized	500,000,000	500,000,000
Common shares issued	122,641,527	123,307,837
Common shares outstanding	122,641,527	123,307,837
Treasury stock issued at cost	112,476,391	111,810,081

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
REVENUES:
Net premiums written	$ 1,646,838	$ 1,663,722
Change in net unearned premiums	(76,796)	(136,387)
Net premiums earned	1,570,042	1,527,335
Net investment income	148,858	130,133
Insurance service fees	33,280	40,362
Net realized investment gains	52,348	25,457
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	0	18,114
Revenues from non-insurance businesses	65,390	101,780
Other income	500	258
Total revenues	1,870,418	1,807,211
OPERATING COSTS AND EXPENSES:
Losses and loss expenses	979,603	922,321
Other operating costs and expenses	603,700	582,459
Expenses from non-insurance businesses	66,019	95,531
Interest expense	36,799	32,224
Total operating costs and expenses	1,686,121	1,632,535
Income before income taxes	184,297	174,676
Income tax expense	(59,623)	(54,428)
Net income before noncontrolling interests	124,674	120,248
Noncontrolling interests	(1,227)	(737)
Net income to common stockholders	$ 123,447	$ 119,511
NET INCOME PER SHARE:
Basic	$ 1.01	$ 0.97
Diluted	$ 0.96	$ 0.93

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income Statement - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net income before noncontrolling interests	$ 124,674	$ 120,248
Other comprehensive income:
Change in unrealized currency translation adjustments	22,735	(2,047)
Change in unrealized investment gains, net of taxes	(8,831)	76,855
Other comprehensive income	13,904	74,808
Comprehensive income	138,578	195,056
Noncontrolling interest	(1,208)	(723)
Comprehensive income to common stockholders	$ 137,370	$ 194,333

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity Statement - USD ($) $ in Thousands	Total	Common stocks	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Accumulated Translation Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Beginning and end of period at Dec. 31, 2015		$ 47,024	$ 1,005,455	$ 6,178,070	$ 180,695	$ (247,393)		$ (2,563,605)	$ 32,962
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(652)
Restricted stock units expensed			8,769
Net income before noncontrolling interests	$ 120,248			119,511					737
Dividends				(14,711)
Change in unrealized investment gains, net of taxes	76,855				76,904
Unrealized gains (losses) on other-than-temporarily impaired securities					(35)
Change in unrealized currency translation adjustments	(2,047)					(2,047)
Stock exercised/vested								652
Stock repurchased								(37,424)
Contributions									3,158
Other comprehensive income (loss)	74,808					(2,047)	$ 74,808		(14)
End of period at Mar. 31, 2016			1,013,572	6,282,870	257,564	(249,440)	8,124	(2,600,377)	36,843
Beginning and end of period at Dec. 31, 2016	5,081,134	$ 47,024	1,037,446	6,595,987	427,154	(371,586)		(2,688,817)	33,926
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(667)
Restricted stock units expensed			10,810
Net income before noncontrolling interests	124,674			123,447					1,227
Dividends				(15,759)
Change in unrealized investment gains, net of taxes	(8,831)				(8,913)
Unrealized gains (losses) on other-than-temporarily impaired securities					101
Change in unrealized currency translation adjustments	22,735					22,735
Stock exercised/vested								644
Stock repurchased								0
Contributions									3,801
Other comprehensive income (loss)	13,904					22,735	13,904		(19)
End of period at Mar. 31, 2017	$ 5,218,541		$ 1,047,589	$ 6,703,675	$ 418,342	$ (348,851)	$ 69,491	$ (2,688,173)	$ 38,935

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FROM (USED IN) OPERATING ACTIVITIES:
Net income to common stockholders	$ 123,447	$ 119,511
Adjustments to reconcile net income to net cash from operating activities:
Net investment gains	(52,348)	(7,343)
Depreciation and amortization	18,133	30,245
Noncontrolling interests	1,227	737
Investment funds	(26,649)	(16,636)
Stock incentive plans	10,780	8,766
Change in:
Arbitrage trading account	2,350	383
Premiums and fees receivable	(59,244)	(79,531)
Reinsurance accounts	67,205	(26,319)
Deferred policy acquisition costs	(6,126)	(33,466)
Income taxes	50,595	46,780
Reserves for losses and loss expenses	10,424	108,057
Unearned premiums	113,483	171,553
Other	(177,805)	(181,969)
Net cash from operating activities	75,472	140,768
CASH USED IN INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	719,969	381,732
Proceeds from sale of equity securities	51,854	1,880
(Contributions to) distributions from investment funds	(11,290)	15,788
Proceeds from maturities and prepayments of fixed maturity securities	888,423	455,463
Purchase of fixed maturity securities	(1,767,208)	(1,032,129)
Purchase of equity securities	(103)	(1,108)
Real estate purchased	(48,710)	(53,781)
Change in loans receivable	3,147	123,737
Net additions to property, furniture and equipment	(12,457)	(12,461)
Change in balances due to security brokers	(22,034)	69,642
Payment for business purchased net of cash aquired	(71,346)	(54,313)
Net cash used in investing activities	(269,755)	(105,550)
CASH (USED IN) FROM FINANCING ACTIVITIES:
Repayment of senior notes and other debt	(1,475)	(33,721)
Proceeds from Issuance of Debt	0	110,093
Cash dividends to common stockholders	0	(14,711)
Purchase of common treasury shares	0	(37,424)
Other, net	(1,281)	3,158
Net cash (used in) from financing activities	(2,756)	27,395
Net impact on cash due to change in foreign exchange rates	10,147	11,271
Net change in cash and cash equivalents	(186,892)	73,884
Cash and cash equivalents at beginning of year	795,285	763,631
Cash and cash equivalents at end of period	$ 608,393	$ 837,515

General General

General General	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	General The unaudited consolidated financial statements, which include the accounts of W. R. Berkley Corporation and its subsidiaries (the “Company”) have been prepared on the basis of U.S. generally accepted accounting principles (“GAAP”) for interim financial information. Accordingly, they do not include all the information and notes required by GAAP for annual financial statements. The unaudited consolidated financial statements reflect all adjustments, consisting only of normal recurring items, which are necessary to present fairly the Company’s financial position and results of operations on a basis consistent with the prior audited consolidated financial statements. Operating results for interim periods are not necessarily indicative of the results that may be expected for the year. All significant intercompany accounts and transactions have been eliminated. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the revenues and expenses reflected during the reporting period. For further information related to a description of areas of judgment and estimates and other information necessary to understand the Company’s financial position and results of operations, refer to the audited consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 . Reclassifications have been made in the 2016 financial statements as originally reported to conform to the presentation of the 2017 financial statements. The income tax provision has been computed based on the Company’s estimated annual effective tax rate. The effective tax rate for the quarter differs from the federal income tax rate of 35% principally because of tax-exempt investment income.

Per Share Data Per Share Data

Per Share Data Per Share Data	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	Per Share Data The Company presents both basic and diluted net income per share (“EPS”) amounts. Basic EPS is calculated by dividing net income by the weighted average number of common shares outstanding during the period (including shares held in a grantor trust established in March 2017). The Company transferred 4,087,731 common shares to the grantor trust for delivery upon settlement of vested but mandatorily deferred restricted stock units (RSUs). Shares held by the grantor trust do not affect diluted shares outstanding since the shares deliverable under vested RSUs were already included in diluted shares outstanding. Diluted EPS is based upon the weighted average number of basic and common equivalent shares outstanding during the period and is calculated using the treasury stock method for stock incentive plans. Common equivalent shares are excluded from the computation in periods in which they have an anti-dilutive effect. The weighted average number of common shares used in the computation of basic and diluted earnings per share was as follows: For the Three Months Ended March 31, (In thousands) 2017 2016 Basic 121,893 122,780 Diluted 128,453 128,529

Recent Accounting Pronouncement

Recent Accounting Pronouncements Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently adopted accounting pronouncements: In May 2015, the Financial Accounting Standards Board ("FASB") issued ASU 2015-09, Disclosures about Short-Duration Contracts. ASU 2015-09 requires companies that issue short duration insurance contracts to disclose additional information, including: (i) incurred and paid claims development tables; (ii) frequency and severity of claims; and (iii) information about material changes in judgments made in calculating the liability for unpaid claim adjustment expenses, including reasons for the change and the effects on the financial statements. The Company adopted this updated guidance on January 1, 2016 with regard to the annual requirements and on January 1, 2017 with regard to the interim requirements. The amendments in ASU 2015-09 are applied retrospectively by providing comparative disclosures for each period presented, except for those requirements that apply only to the current period. As the requirements are disclosure only, the adoption of this guidance did not impact our financial condition or results of operations, but did result in additional disclosures. In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 includes provisions intended to simplify various previous provisions related to how share-based payments are accounted for and presented in the financial statements. Under the new guidance, excess tax benefits (deductions for share based payment awards for tax purposes that exceed the compensation cost recognized for financial reporting purposes) are reported within the income tax expense financial statement line item. Previously, excess tax benefits were reported within additional paid in capital. The Company adopted this updated guidance on January 1, 2017 prospectively. The adoption of this guidance did not have a material impact on the Company's financial condition or results of operations. All other accounting and reporting standards that became effective in 2017 were either not applicable to the Company or their adoption did not have a material impact on the Company. Accounting and reporting standards that are not yet effective: In May 2014, the FASB issued ASU 2014-09, Revenue from Customers. ASU 2014-09 clarifies the principles for recognizing revenue. While insurance contracts are not within the scope of this updated guidance, the Company’s insurance service fee revenue and non-insurance business revenue will be subject to this updated guidance. The updated guidance requires an entity to recognize revenue as performance obligations are met, in order to reflect the transfer of promised goods or services to customers in an amount that reflects the consideration the entity is entitled to receive for those goods or services. The updated guidance, as amended by ASU 2015-14, is effective for public business entities for annual and interim reporting periods beginning after December 15, 2017. The adoption of this guidance is not expected to have a material effect on the Company’s financial condition or results of operations. In January 2016, the FASB issued ASU 2016-01, Financial Instruments. ASU 2016-01 amends the accounting guidance for financial instruments to require all equity investments to be measured at fair value with changes in the fair value recognized through net income (other than those accounted for under equity method of accounting or those that result in consolidation of the investee). The updated guidance is effective for public business entities for annual reporting periods beginning after December 15, 2017 and interim periods within those years. The adoption of this guidance is not expected to have a material effect on the Company’s financial condition upon adoption, but will impact results of operations after adoption of this guidance as unrealized gains and losses on equity securities will no longer be reported directly in accumulated other comprehensive income (AOCI), but will instead be reported in net income. In February 2016, the FASB issued ASU 2016-02, Leases, which amends the accounting and disclosure guidance for leases. This guidance retains the two classifications of a lease, as either an operating or finance lease, both of which will require lessees to recognize a right-of-use asset and a lease liability for leases with terms of more than 12 months. The right-of-use asset and the lease liability will be determined based upon the present value of cash flows. Finance leases will reflect the financial arrangement by recognizing interest expense on the lease liability separately from the amortization expense of the right-of-use asset. Operating leases will recognize lease expense (with no separate recognition of interest expense) on a straight-line basis over the term of the lease. The accounting by lessors is not significantly changed by the updated guidance. The updated guidance is effective for reporting periods beginning after December 15, 2018, and will require that the earliest comparative period presented include the measurement and recognition of existing leases with an adjustment to equity as if the updated guidance had always been applied. The Company is currently evaluating the impact that the adoption of this guidance will have on its results of operations, financial position and liquidity. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses, which amends the accounting guidance for credit losses on financial instruments. The updated guidance amends the current other-than-temporary impairment model for available-for-sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limits the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. This guidance also applies a new current expected credit loss model for determining credit-related impairments for financial instruments measured at amortized cost. The updated guidance is effective for reporting periods beginning after December 15, 2019. The Company will not be able to determine the impact the adoption of this guidance will have on its results of operations, financial position or liquidity until the year the guidance becomes effective. All other recently issued but not yet effective accounting and reporting standards are either not applicable to the Company or are not expected to have a material impact on the Company.

Acquistions Acquisitions

Acquistions Acquisitions	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Business Combination Disclosure	Acquisitions In March 2017, the Company acquired an 89.5% ownership interest for $72.5 million in a company engaged in providing textile solutions world-wide. The fair value of the assets acquired and liabilities assumed have been estimated based on a preliminary valuation. The fair values of the assets and liabilities will be adjusted, as needed, following completion of the final valuation. The following table summarizes the initial estimated fair value of net assets acquired and liabilities assumed for the business combination completed in 2017: (In thousands) 2017 Cash and cash equivalents $ 1,154 Real estate, furniture and equipment 6,434 Goodwill and other intangibles assets 62,406 Other assets 9,417 Total assets acquired 79,411 Other liabilities assumed (1,911 ) Noncontrolling interest (5,000 ) Net assets acquired $ 72,500 In February 2016, the Company acquired an 85% ownership interest for $42.3 million in a company engaged in the distribution of promotional merchandise.

Statements of Comprehensive Inc

Statements of Comprehensive Income (Loss) Statements of Comprehensive Income (Loss) (Notes)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Comprehensive Income (Loss)	(5) Consolidated Statement of Comprehensive Income (Loss) The following tables present the components of the changes in accumulated other comprehensive income (loss) ("AOCI"): (In thousands) Unrealized Investment Gains (Losses) Currency Translation Adjustments Accumulated Other Comprehensive Income (Loss) As of and for the three months ended March 31, 2017: Changes in AOCI Beginning of period $ 427,154 $ (371,586 ) $ 55,568 Other comprehensive income (loss) before reclassifications 19,994 22,735 42,729 Amounts reclassified from AOCI (28,825 ) — (28,825 ) Other comprehensive income (loss) (8,831 ) 22,735 13,904 Unrealized investment gain related to non-controlling interest 19 — 19 End of period $ 418,342 $ (348,851 ) $ 69,491 Amounts reclassified from AOCI Pre-tax $ (44,346 ) (1) $ — $ (44,346 ) Tax effect 15,521 (2) — 15,521 After-tax amounts reclassified $ (28,825 ) $ — $ (28,825 ) Other comprehensive income (loss) Pre-tax $ (9,571 ) $ 22,735 $ 13,164 Tax effect 740 — 740 Other comprehensive income (loss) $ (8,831 ) $ 22,735 $ 13,904 As of and for the three months ended March 31, 2016: Changes in AOCI Beginning of period $ 180,695 $ (247,393 ) $ (66,698 ) Other comprehensive income (loss) before reclassifications 78,242 (2,047 ) 76,195 Amounts reclassified from AOCI (1,387 ) — (1,387 ) Other comprehensive income (loss) 76,855 (2,047 ) 74,808 Unrealized investment gain related to non-controlling interest 14 14 End of period $ 257,564 $ (249,440 ) $ 8,124 Amounts reclassified from AOCI Pre-tax $ (2,134 ) (1) $ — $ (2,134 ) Tax effect 747 (2) — 747 After-tax amounts reclassified $ (1,387 ) $ — $ (1,387 ) Other comprehensive income (loss) Pre-tax $ 114,390 $ (2,047 ) $ 112,343 Tax effect (37,535 ) — (37,535 ) Other comprehensive income (loss) $ 76,855 $ (2,047 ) $ 74,808 _________________________ (1) Net realized investment gains in the consolidated statements of income. (2) Income tax expense in the consolidated statements of income.

Statements of Cash Flow Stateme

Statements of Cash Flow Statements of Cash Flow	3 Months Ended
	Mar. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Cash Flow, Supplemental Disclosures	Statements of Cash Flow Interest payments were $61,782,000 and $56,968,000 and income taxes paid were $1,610,000 and $5,644,000 in the three months ended March 31, 2017 and 2016 , respectively.

Investments In Fixed Maturity S

Investments In Fixed Maturity Securities	3 Months Ended
	Mar. 31, 2017
Debt Securities [Member]
Schedule of Marketable Securities [Line Items]
Investments In Fixed Maturity Securities	Investments in Fixed Maturity Securities At March 31, 2017 and December 31, 2016 , investments in fixed maturity securities were as follows: (In thousands) Amortized Cost Gross Unrealized Fair Value Carrying Value Gains Losses March 31, 2017 Held to maturity: State and municipal $ 73,631 $ 13,374 $ — $ 87,005 $ 73,631 Residential mortgage-backed 15,316 1,651 — 16,967 15,316 Total held to maturity 88,947 15,025 — 103,972 88,947 Available for sale: U.S. government and government agency 472,112 16,784 (2,220 ) 486,676 486,676 State and municipal: Special revenue 2,759,063 69,226 (15,887 ) 2,812,402 2,812,402 State general obligation 504,312 18,952 (3,295 ) 519,969 519,969 Pre-refunded 349,697 20,013 (146 ) 369,564 369,564 Corporate backed 376,664 8,290 (5,639 ) 379,315 379,315 Local general obligation 360,941 20,497 (1,602 ) 379,836 379,836 Total state and municipal 4,350,677 136,978 (26,569 ) 4,461,086 4,461,086 Mortgage-backed securities: Residential (1) 1,067,779 14,081 (13,030 ) 1,068,830 1,068,830 Commercial 144,583 347 (2,126 ) 142,804 142,804 Total mortgage-backed securities 1,212,362 14,428 (15,156 ) 1,211,634 1,211,634 Asset-backed 2,029,812 7,837 (9,480 ) 2,028,169 2,028,169 Corporate: Industrial 2,391,507 70,783 (5,330 ) 2,456,960 2,456,960 Financial 1,445,707 45,431 (6,881 ) 1,484,257 1,484,257 Utilities 238,801 10,578 (2,049 ) 247,330 247,330 Other 55,808 471 (30 ) 56,249 56,249 Total corporate 4,131,823 127,263 (14,290 ) 4,244,796 4,244,796 Foreign 864,556 38,692 (1,577 ) 901,671 901,671 Total available for sale 13,061,342 341,982 (69,292 ) 13,334,032 13,334,032 Total investments in fixed maturity securities $ 13,150,289 $ 357,007 $ (69,292 ) $ 13,438,004 $ 13,422,979 (In thousands) Amortized Gross Unrealized Fair Carrying Gains Losses December 31, 2016 Held to maturity: State and municipal $ 72,582 $ 12,453 $ — $ 85,035 $ 72,582 Residential mortgage-backed 15,944 1,693 — 17,637 15,944 Total held to maturity 88,526 14,146 — 102,672 88,526 Available for sale: U.S. government and government agency 496,187 20,208 (2,593 ) 513,802 513,802 State and municipal: Special revenue 2,791,211 58,559 (26,315 ) 2,823,455 2,823,455 State general obligation 524,682 16,964 (5,139 ) 536,507 536,507 Pre-refunded 356,535 19,181 (165 ) 375,551 375,551 Corporate backed 410,933 6,172 (6,452 ) 410,653 410,653 Local general obligation 360,022 15,682 (2,367 ) 373,337 373,337 Total state and municipal 4,443,383 116,558 (40,438 ) 4,519,503 4,519,503 Mortgage-backed securities: Residential (1) 1,034,301 15,431 (12,950 ) 1,036,782 1,036,782 Commercial 155,540 304 (2,981 ) 152,863 152,863 Total mortgage-backed securities 1,189,841 15,735 (15,931 ) 1,189,645 1,189,645 Asset-backed 1,913,830 5,971 (11,941 ) 1,907,860 1,907,860 Corporate: Industrial 2,315,567 71,007 (7,174 ) 2,379,400 2,379,400 Financial 1,369,001 39,543 (11,270 ) 1,397,274 1,397,274 Utilities 229,154 10,801 (2,411 ) 237,544 237,544 Other 54,073 299 (63 ) 54,309 54,309 Total corporate 3,967,795 121,650 (20,918 ) 4,068,527 4,068,527 Foreign 858,773 46,794 (2,762 ) 902,805 902,805 Total available for sale 12,869,809 326,916 (94,583 ) 13,102,142 13,102,142 Total investments in fixed maturity securities $ 12,958,335 $ 341,062 $ (94,583 ) $ 13,204,814 $ 13,190,668 ____________ (1) Gross unrealized losses for residential mortgage-backed securities include $717,960 and $818,691 as of March 31, 2017 and December 31, 2016 , respectively, related to the non-credit portion of other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income. The amortized cost and fair value of fixed maturity securities at March 31, 2017 , by contractual maturity, are shown below. Actual maturities may differ from contractual maturities because certain issuers may have the right to call or prepay obligations. (In thousands) Amortized Cost Fair Value Due in one year or less $ 1,033,358 $ 1,049,761 Due after one year through five years 5,160,693 5,288,826 Due after five years through ten years 3,273,799 3,386,314 Due after ten years 2,454,761 2,484,502 Mortgage-backed securities 1,227,678 1,228,601 Total $ 13,150,289 $ 13,438,004 At March 31, 2017 and December 31, 2016, there were no investments that exceeded 10% of common stockholders' equity, other than investments in United States government and government agency securities.

Reserves for Loss and Loss Expe

Reserves for Loss and Loss Expenses Reserves for Loss and Loss Expenses	3 Months Ended
	Mar. 31, 2017
Insurance [Abstract]
Reserves for Loss and Loss Expenses	Reserves for Losses and Loss Expenses Loss reserves included in the Company’s financial statements represent management’s best estimates based upon an actuarially derived point estimate and other considerations. The Company uses a variety of actuarial techniques and methods to derive an actuarial point estimate for each operating unit. These methods include paid loss development, incurred loss development, paid and incurred Bornhuetter-Ferguson methods and frequency and severity methods. In circumstances where one actuarial method is considered more credible than the others, that method is used to set the point estimate. The actuarial point estimate may also be based on a judgmental weighting of estimates produced from each of the methods considered. Industry loss experience is used to supplement the Company’s own data in selecting “tail factors” in areas where the Company’s own data is limited. The actuarial data is analyzed by line of business, coverage and accident or policy year, as appropriate, for each operating unit. The establishment of the actuarially derived loss reserve point estimate also includes consideration of qualitative factors that may affect the ultimate losses. These qualitative considerations include, among others, the impact of re-underwriting initiatives, changes in the mix of business, changes in distribution sources and changes in policy terms and conditions. The key assumptions used to arrive at the best estimate of loss reserves are the expected loss ratios, rate of loss cost inflation, and reported and paid loss emergence patterns. Expected loss ratios represent management’s expectation of losses at the time the business is priced and written, before any actual claims experience has emerged. This expectation is a significant determinant of the estimate of loss reserves for recently written business where there is little paid or incurred loss data to consider. Expected loss ratios are generally derived from historical loss ratios adjusted for the impact of rate changes, loss cost trends and known changes in the type of risks underwritten. Expected loss ratios are estimated for each key line of business within each operating unit. Expected loss cost inflation is particularly important for the long-tail lines, such as excess casualty, and claims with a high medical component, such as workers’ compensation. Reported and paid loss emergence patterns are used to project current reported or paid loss amounts to their ultimate settlement value. Loss development factors are based on the historical emergence patterns of paid and incurred losses, and are derived from the Company’s own experience and industry data. The paid loss emergence pattern is also significant to excess and assumed workers’ compensation reserves because those reserves are discounted to their estimated present value based upon such estimated payout patterns. Loss frequency and severity are measures of loss activity that are considered in determining the key assumptions described in our discussion of loss and loss expense reserves, including expected loss ratios, rate of loss cost inflation and reported and paid loss emergence patterns. Loss frequency is a measure of the number of claims per unit of insured exposure, and loss severity is a measure of the average size of claims. Factors affecting loss frequency include the effectiveness of loss controls and safety programs and changes in economic activity or weather patterns. Factors affecting loss severity include changes in policy limits, retentions, rate of inflation and judicial interpretations. Another factor affecting estimates of loss frequency and severity is the loss reporting lag, which is the period of time between the occurrence of a loss and the date the loss is reported to the Company. The length of the loss reporting lag affects our ability to accurately predict loss frequency (loss frequencies are more predictable for lines with short reporting lags) as well as the amount of reserves needed for incurred but not reported losses (less IBNR is required for lines with short reporting lags). As a result, loss reserves for lines with short reporting lags are likely to have less variation from initial loss estimates. For lines with short reporting lags, which include commercial automobile, primary workers’ compensation, other liability (claims-made) and property business, the key assumption is the loss emergence pattern used to project ultimate loss estimates from known losses paid or reported to date. For lines of business with long reporting lags, which include other liability (occurrence), products liability, excess workers’ compensation and liability reinsurance, the key assumption is the expected loss ratio since there is often little paid or incurred loss data to consider. Historically, the Company has experienced less variation from its initial loss estimates for lines of businesses with short reporting lags than for lines of business with long reporting lags. The key assumptions used in calculating the most recent estimate of the loss reserves are reviewed each quarter and adjusted, to the extent necessary, to reflect the latest reported loss data, current trends and other factors observed. The table below provides a reconciliation of the beginning and ending reserve balances: March 31, (In thousands) 2017 2016 Net reserves at beginning of year $ 9,590,265 $ 9,244,872 Net provision for losses and loss expenses: Claims occurring during the current year (1) 958,684 916,649 Increase (decrease) in estimates for claims occurring in prior years (2) (3) 8,727 (5,601 ) Loss reserve discount accretion 12,192 11,273 Total 979,603 922,321 Net payments for claims: Current year 97,461 259,633 Prior year 773,571 555,884 Total 871,032 815,517 Foreign currency translation 23,204 20,760 Net reserves at end of period 9,722,040 9,372,436 Ceded reserve at end of period 1,502,284 1,415,906 Gross reserves at end of period $ 11,224,324 $ 10,788,342 _______________________________________ (1) Claims occurring during the current year are net of loss reserve discounts of $ 5,761,000 and $ 19,072,000 in 2017 and 2016, respectively. (2) The increase in estimates for claims occurring in prior years is net of loss reserve discount. On an undiscounted basis, the estimates for claims occurring in prior years increased by $ 4,841,000 and decreased by $ 23,559,000 in 2017 and 2016, respectively. (3) For certain retrospectively rated insurance policies and reinsurance agreements, reserve development is offset by additional or return premiums. Favorable development, net of additional and return premiums, was $ 2 million and $ 12 million as of March 31, 2017 and 2016, respectively. During the three months ended March 31, 2017, favorable prior year development (net of additional and return premiums) of $2.4 million included $26.2 million of favorable development for the Insurance segment, largely offset by $23.8 million of adverse development for the Reinsurance segment. The favorable development for the Insurance segment was primarily attributable to workers' compensation business, including excess workers' compensation. The favorable workers' compensation development was spread across many accident years, including prior to 2008, but was most significant in accident years 2014 and 2015. The favorable workers' compensation development reflects a continuation of the benign loss cost trends experienced during 2016, particularly the favorable claim frequency trends ( i.e., number of reported claims per unit of exposure). The adverse development for the Reinsurance segment was almost entirely due to reserve strengthening associated with claims impacted by the change in the Ogden discount rate in the UK. The Ogden rate is the discount rate used to calculate lump-sum bodily injury payouts in the UK and was recently reduced by the UK Ministry of Justice from +2.5% to -0.75%. The adverse development mostly related to UK motor bodily injury claims which we reinsured on an excess of loss basis in accident years 2012 through 2016. During the three months ended March 31, 2016, favorable prior year development (net of additional and return premiums) of $ 12.3 million included $ 11.6 million for the Insurance segment and $ 0.7 million for the Reinsurance segment. The favorable development for the Insurance segment was primarily attributable to workers' compensation business from accident years 2010 through 2015, partially offset by adverse development for commercial auto liability from accident years 2011 through 2014. The favorable development for workers' compensation reflects favorable claim frequency trends ( i.e. , number of reported claims per unit of exposure), while the unfavorable development for commercial auto liability was driven by higher large loss activity than expected.

Investments in Equity Securitie

Investments in Equity Securities	3 Months Ended
	Mar. 31, 2017
Equity securities available for sale
Schedule of Available-for-sale Securities [Line Items]
Investments in Equity Securities	Investments in Equity Securities Available for Sale At March 31, 2017 and December 31, 2016 , investments in equity securities were as follows: (In thousands) Cost Gross Unrealized Fair Value Carrying Value Gains Losses March 31, 2017 Common stocks $ 90,080 $ 333,397 $ (2,148 ) $ 421,329 $ 421,329 Preferred stocks 121,360 70,795 (2,106 ) 190,049 190,049 Total $ 211,440 $ 404,192 $ (4,254 ) $ 611,378 $ 611,378 December 31, 2016 Common stocks $ 94,998 $ 351,906 $ (1,046 ) $ 445,858 $ 445,858 Preferred stocks 125,589 101,392 (3,639 ) 223,342 223,342 Total $ 220,587 $ 453,298 $ (4,685 ) $ 669,200 $ 669,200

Arbitrage Trading Account Arbit

Arbitrage Trading Account Arbitrage Trading Account (Notes)	3 Months Ended
	Mar. 31, 2017
Schedule of Investments [Abstract]
Arbitrage Trading Account and Arbitrage Funds [Text Block]	Arbitrage Trading Account At March 31, 2017 and December 31, 2016 , the fair and carrying values of the arbitrage trading account were $753 million and $300 million , respectively. The primary focus of the trading account is merger arbitrage. Merger arbitrage is the business of investing in the securities of publicly held companies which are the targets in announced tender offers and mergers. Arbitrage investing differs from other types of investing in its focus on transactions and events believed likely to bring about a change in value over a relatively short time period (usually four months or less). The Company uses put options, call options and swap contracts in order to mitigate the impact of potential changes in market conditions on the merger arbitrage trading account. These options and contracts are reported at fair value. As of March 31, 2017 , the fair value of long option contracts outstanding was $0.6 million (notional amount of $14 million ) and the fair value of short option contracts outstanding was $0.4 million (notional amount of $40 million ). Other than with respect to the use of these trading account securities, the Company does not make use of derivatives.

Net Investment Income Net Inves

Net Investment Income Net Investment Income	3 Months Ended
	Mar. 31, 2017
Income Statement [Abstract]
Net Investment Income	Net Investment Income Net investment income consisted of the following: For the Three Months Ended March 31, (In thousands) 2017 2016 Investment income earned on: Fixed maturity securities, including cash and cash equivalents and loans receivable $ 112,346 $ 108,835 Investment funds 26,649 16,636 Arbitrage trading account 6,360 3,190 Real estate 4,566 2,717 Equity securities available for sale 639 868 Gross investment income 150,560 132,246 Investment expense (1,702 ) (2,113 ) Net investment income $ 148,858 $ 130,133

Investment Funds Investment Fun

Investment Funds Investment Funds	3 Months Ended
	Mar. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Net Investment Income	Investment Funds The Company evaluates whether it is an investor in a variable interest entity (VIE). Such entities do not have sufficient equity at risk to finance their activities without additional subordinated financial support, or the equity investors, as a group, do not have the characteristics of a controlling financial interest (primary beneficiary). The Company determines whether it is the primary beneficiary of an entity subject to consolidation based on a qualitative assessment of the VIE's capital structure, contractual terms, nature of the VIE's operations and purpose, and the Company's relative exposure to the related risks of the VIE on the date it becomes initially involved in the VIE and on an ongoing basis. The Company is not the primary beneficiary in any of its investment funds, and accordingly, carries its interests in investments funds under the equity method of accounting. The Company’s maximum exposure to loss with respect to these investments is limited to the carrying amount reported on the Company’s consolidated balance sheet and its unfunded commitments which were $362 million as of March 31, 2017. Investment funds consist of the following: Carrying Value as of Income (Loss) from Investment Funds March 31, December 31, For the Three Months Ended March 31, (In thousands) 2017 2016 2017 2016 Real estate $ 654,501 $ 641,783 $ 4,532 $ 17,037 Energy 96,161 91,448 3,245 (3,924 ) Hedge equity 74,779 73,913 866 (2,852 ) Other funds 413,117 391,002 18,006 6,375 Total $ 1,238,558 $ 1,198,146 $ 26,649 $ 16,636 The Company's share of the earnings or losses of investment funds is generally reported on a one-quarter lag in order to facilitate the timely completion of the Company's consolidated financial statements.

Real Estate Real Estate

Real Estate Real Estate	3 Months Ended
	Mar. 31, 2017
Real Estate [Abstract]
Real Estate	Real Estate Investment in real estate represents directly owned property held for investment, as follows: Carrying Value March 31, December 31, (In thousands) 2017 2016 Properties in operation $ 448,422 $ 457,237 Properties under development 789,316 727,744 Total $ 1,237,738 $ 1,184,981 In 2017, properties in operation included a long-term ground lease in Washington, D.C., a hotel in Memphis, Tennessee, an office complex in New York City and office buildings in West Palm Beach and Palm Beach, Florida. Properties in operation are net of accumulated depreciation and amortization of $16,654,000 and $14,996,000 as of March 31, 2017 and December 31, 2016, respectively. Related depreciation expense was $1,648,000 and $1,668,000 for the three months ended March 31, 2017 and 2016, respectively. Future minimum rental income expected on operating leases relating to properties in operation is $13,116,000 in 2017, $26,513,000 in 2018, $27,839,000 in 2019, $26,673,000 in 2020, $26,958,000 in 2021, $26,618,000 in 2022 and $449,273,000 thereafter. Properties under development include an office building in London and a mixed-use project in Washington, D.C.

Loans Receivable Loans Receivab

Loans Receivable Loans Receivable	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Loans Receivable	Loans Receivable Loans receivable are as follows: (In thousands) March 31, 2017 December 31, 2016 Amortized cost (net of valuation allowance): Real estate loans $ 89,206 $ 92,415 Commercial loans 14,444 14,383 Total $ 103,650 $ 106,798 Fair value: Real estate loans $ 89,206 $ 92,415 Commercial loans 15,947 15,884 Total $ 105,153 $ 108,299 Valuation allowance: Specific $ 1,200 $ 1,200 General 2,183 2,197 Total $ 3,383 $ 3,397 For the Three Months Ended March 31, 2017 2016 Increase (decrease) in valuation allowance $ (14 ) $ 568 Loans receivable in non-accrual status were $5.3 million and $5.4 million as of March 31, 2017 and December 31, 2016, respectively. The Company monitors the performance of its loans receivable and assesses the ability of the borrower to pay principal and interest based upon loan structure, underlying property values, cash flow and related financial and operating performance of the property and market conditions. Loans receivable with a potential for default are further assessed using discounted cash flow analysis and comparable cost and sales methodologies, if appropriate. The real estate loans are secured by commercial real estate primarily located in North Carolina and New York. These loans generally earn interest at floating LIBOR-based interest rates and have maturities (inclusive of extension options) through August 2025. The commercial loans are with small business owners who have secured the related financing with the assets of the business. Commercial loans primarily earn interest on a fixed basis and have varying maturities generally not exceeding 10 years. In evaluating the real estate loans, the Company considers their credit quality indicators, including loan to value ratios, which compare the outstanding loan amount to the estimated value of the property, the borrower’s financial condition and performance with respect to loan terms, the position in the capital structure, the overall leverage in the capital structure and other market conditions. Based on these considerations, none of the real estate loans were considered to be impaired at March 31, 2017, and accordingly, the Company determined that a specific valuation allowance was not required.

Realized And Unrealized Investm

Realized And Unrealized Investment Gains (Losses)	3 Months Ended
	Mar. 31, 2017
Realized and Unrealized Investment Gains (Losses) [Abstract]
Realized and Unrealized Investment Gains (Losses)	Realized and Unrealized Investment Gains (Losses) Realized and unrealized investment gains (losses) are as follows: For the Three Months Ended March 31, (In thousands) 2017 2016 Realized investment gains (losses): Fixed maturity securities: Gains $ 5,605 $ 23,064 Losses (3,965 ) (2,940 ) Equity securities available for sale 42,707 125 Investment funds 1,267 (460 ) Real estate 3,300 5,024 Other 3,434 644 Net realized gains on investments sales 52,348 25,457 Other-than-temporary impairments (1) — (18,114 ) Net investment gains 52,348 7,343 Income tax expense (18,322 ) (2,570 ) After-tax net realized investment gains $ 34,026 $ 4,773 Change in unrealized investment gains (losses) of available for sale securities: Fixed maturity securities $ 37,984 $ 92,428 Previously impaired fixed maturity securities 101 (55 ) Equity securities available for sale (48,862 ) 13,137 Investment funds 1,206 8,880 Total change in unrealized investment gains (losses) (9,571 ) 114,390 Income tax benefit (expense) 740 (37,535 ) Noncontrolling interests 19 14 After-tax change in unrealized investment gains (losses) of available for sale securities $ (8,812 ) $ 76,869 ______________________ (1) There were no other than temporary impairments (OTTI) for the three months ended March 31, 2017. OTTI for the three months ended March 31, 2016 of $18.1 million related to common stock.

Securities In An Unrealized Los

Securities In An Unrealized Loss Position	3 Months Ended
	Mar. 31, 2017
Investments [Abstract]
Securities in Unrealized Loss Position	Securities in an Unrealized Loss Position The following tables summarize all securities in an unrealized loss position at March 31, 2017 and December 31, 2016 by the length of time those securities have been continuously in an unrealized loss position: Less Than 12 Months 12 Months or Greater Total (In thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses March 31, 2017 U.S. government and government agency $ 95,253 $ 954 $ 33,071 $ 1,266 $ 128,324 $ 2,220 State and municipal 1,111,978 22,836 150,439 3,733 1,262,417 26,569 Mortgage-backed securities 618,642 10,013 140,791 5,143 759,433 15,156 Asset-backed securities 1,204,310 4,386 95,421 5,094 1,299,731 9,480 Corporate 867,293 8,126 61,732 6,164 929,025 14,290 Foreign government 115,542 1,320 4,495 257 120,037 1,577 Fixed maturity securities 4,013,018 47,635 485,949 21,657 4,498,967 69,292 Common stocks 18,875 1,173 8,803 975 27,678 2,148 Preferred stocks — — 23,567 2,106 23,567 2,106 Equity securities available for sale 18,875 1,173 32,370 3,081 51,245 4,254 Total $ 4,031,893 $ 48,808 $ 518,319 $ 24,738 $ 4,550,212 $ 73,546 December 31, 2016 U.S. government and government agency $ 112,709 $ 1,252 $ 35,450 $ 1,341 $ 148,159 $ 2,593 State and municipal 1,562,614 35,553 133,034 4,885 1,695,648 40,438 Mortgage-backed securities 625,903 11,103 109,066 4,828 734,969 15,931 Asset-backed securities 1,010,836 5,340 201,693 6,601 1,212,529 11,941 Corporate 1,035,245 13,448 65,147 7,470 1,100,392 20,918 Foreign government 213,246 1,985 24,820 777 238,066 2,762 Fixed maturity securities 4,560,553 68,681 569,210 25,902 5,129,763 94,583 Common stocks 336 22 8,755 1,024 9,091 1,046 Preferred stocks — — 22,034 3,639 22,034 3,639 Equity securities available for sale 336 22 30,789 4,663 31,125 4,685 Total $ 4,560,889 $ 68,703 $ 599,999 $ 30,565 $ 5,160,888 $ 99,268 Fixed Maturity Securities – A summary of the Company’s non-investment grade fixed maturity securities that were in an unrealized loss position at March 31, 2017 is presented in the table below: ($ in thousands) Number of Securities Aggregate Fair Value Gross Unrealized Loss State and municipal 1 $ 5,136 $ 3,725 Mortgage-backed securities 9 19,647 924 Corporate 4 19,990 741 Foreign government 11 51,901 681 Asset-backed securities 6 9,615 173 Total 31 $ 106,289 $ 6,244 For OTTI of fixed maturity securities that management does not intend to sell or, to be required to sell, the portion of the decline in value that is considered to be due to credit factors is recognized in earnings, and the portion of the decline in value that is considered to be due to non-credit factors is recognized in other comprehensive income. The Company has evaluated its fixed maturity securities in an unrealized loss position and believes the unrealized losses are due primarily to temporary market and sector-related factors rather than to issuer-specific factors. None of these securities are delinquent or in default under financial covenants. Based on its assessment of these issuers, the Company expects them to continue to meet their contractual payment obligations as they become due and does not consider any of these securities to be OTTI. Preferred Stocks – At March 31, 2017 , there was one preferred stock in an unrealized loss position, with a fair value of $23.6 million and a gross unrealized loss of $2.1 million . Based upon management’s view of the underlying value of this security, the Company does not consider the security to be OTTI. For three months ended March 31, 2017 and 2016, there were no OTTI for preferred stocks. Common Stocks – At March 31, 2017 , there were three common stocks in an unrealized loss position, with an aggregate fair value of $27.7 million and a gross unrealized loss of $2.1 million . Based on management's view of the underlying securities, the Company does not consider these equity securities to be OTTI. There was no OTTI of common stocks for the three months ended March 31, 2017. For the three months ended March 31, 2016, OTTI for common stocks was $ 18.1 million .

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Measurements	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Measurements The Company’s fixed maturity and equity securities classified as available for sale and its trading account securities are carried at fair value. 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.” The Company utilizes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels, as follows: Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 - Quoted prices for similar assets or valuations based on inputs that are observable. Level 3 - Estimates of fair value based on internal pricing methodologies using unobservable inputs. Unobservable inputs are only used to measure fair value to the extent that observable inputs are not available. Substantially, all of the Company’s fixed maturity securities were priced by independent pricing services. The prices provided by the independent pricing services are estimated based on observable market data in active markets utilizing pricing models and processes, which may include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, sector groupings, matrix pricing and reference data. The pricing services may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs are available for each security evaluation on any given day. The pricing services used by the Company have indicated that they will only produce an estimate of fair value if objectively verifiable information is available. The determination of whether markets are active or inactive is based upon the volume and level of activity for a particular asset class. The Company reviews the prices provided by pricing services for reasonableness and periodically performs independent price tests of a sample of securities to ensure proper valuation. If prices from independent pricing services are not available for fixed maturity securities, the Company estimates the fair value. For Level 2 securities, the Company utilizes pricing models and processes which may include benchmark yields, sector groupings, matrix pricing, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, bids, offers and reference data. Where broker quotes are used, the Company generally requests two or more quotes and sets a price within the range of quotes received based on its assessment of the credibility of the quote and its own evaluation of the security. The Company generally does not adjust quotes received from brokers. For securities traded only in private negotiations, the Company determines fair value based primarily on the cost of such securities, which is adjusted to reflect prices of recent placements of securities of the same issuer, financial projections, credit quality and business developments of the issuer and other relevant information. For Level 3 securities, the Company generally uses a discounted cash flow model to estimate the fair value of fixed maturity securities. The cash flow models are based upon assumptions as to prevailing credit spreads, interest rate and interest rate volatility, time to maturity and subordination levels. Projected cash flows are discounted at rates that are adjusted to reflect illiquidity, where appropriate. The following tables present the assets and liabilities measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 by level: (In thousands) Total Level 1 Level 2 Level 3 March 31, 2017 Assets: Fixed maturity securities available for sale: U.S. government and government agency $ 486,676 $ — $ 486,676 $ — State and municipal 4,461,086 — 4,461,086 — Mortgage-backed securities 1,211,634 — 1,211,634 — Asset-backed securities 2,028,169 — 2,027,990 179 Corporate 4,244,796 — 4,244,796 — Foreign government 901,671 — 901,671 — Total fixed maturity securities available for sale 13,334,032 — 13,333,853 179 Equity securities available for sale: Common stocks 421,329 403,855 8,671 8,803 Preferred stocks 190,049 — 186,387 3,662 Total equity securities available for sale 611,378 403,855 195,058 12,465 Arbitrage trading account 753,278 256,752 496,465 61 Total $ 14,698,688 $ 660,607 $ 14,025,376 $ 12,705 Liabilities: Trading account securities sold but not yet purchased $ 51,348 $ 51,348 $ — $ — December 31, 2016 Assets: Fixed maturity securities available for sale: U.S. government and government agency $ 513,802 $ — $ 513,802 $ — State and municipal 4,519,503 — 4,519,503 — Mortgage-backed securities 1,189,645 — 1,189,645 — Asset-backed securities 1,907,860 — 1,907,677 183 Corporate 4,068,527 — 4,068,527 — Foreign government 902,805 — 902,805 — Total fixed maturity securities available for sale 13,102,142 — 13,101,959 183 Equity securities available for sale: Common stocks 445,858 429,647 7,457 8,754 Preferred stocks 223,342 — 219,680 3,662 Total equity securities available for sale 669,200 429,647 227,137 12,416 Arbitrage trading account 299,999 224,623 75,376 — Total $ 14,071,341 $ 654,270 $ 13,404,472 $ 12,599 Liabilities: Trading account securities sold but not yet purchased $ 51,179 $ 51,089 $ 90 $ — There were no significant transfers between Levels 1 and 2 during the three months ended March 31, 2017 or during the year ended December 31, 2016 . The following tables summarize changes in Level 3 assets and liabilities for the three months ended March 31, 2017 and for the year ended December 31, 2016 : Gains (Losses) Included in: (In thousands) Beginning Balance Earnings (Losses) Other Comprehensive Income (Loss) Impairments Purchases (Sales) Paydowns / Maturities Transfers Ending Balance In / (Out) Three Months Ended March 31, 2017: Assets: Fixed maturities securities available for sale: Asset-backed securities $ 183 $ 1 $ 10 $ — $ — $ (15 ) $ — $ — $ 179 Corporate — — — — — — — — — Total 183 1 10 — — (15 ) — — 179 Equity securities available for sale: Common stocks 8,754 — 49 — — — — — 8,803 Preferred stocks 3,662 — — — — — — 3,662 Total 12,416 — 49 — — — — — 12,465 Arbitrage trading account — — 61 — — — — — 61 Total $ 12,599 $ 1 $ 120 $ — $ — $ (15 ) $ — $ — $ 12,705 Year ended December 31, 2016: Assets: Fixed maturities securities available for sale: Asset-backed securities $ 199 $ 3 $ 16 $ — $ — $ — $ (35 ) $ — $ 183 Corporate 154 177 — — — (331 ) — — — Total 353 180 16 — — (331 ) (35 ) — 183 Equity securities available for sale: Common stocks 7,829 — 160 — 765 — — — 8,754 Preferred stocks 3,624 38 — — — — — — 3,662 Total 11,453 38 160 — 765 — — — 12,416 Arbitrage trading account 176 (176 ) — — — — — — Total $ 11,982 $ 42 $ 176 $ — $ 765 $ (331 ) $ (35 ) $ — $ 12,599 During the three months ended March 31, 2017 and the year ended December 31, 2016, there were no t ransfers out of Level 3. Fair Value of Financial Instruments The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments: March 31, 2017 December 31, 2016 (In thousands) Carrying Value Fair Value Carrying Value Fair Value Assets: Fixed maturity securities $ 13,422,979 $ 13,438,004 $ 13,190,668 $ 13,204,814 Equity securities available for sale 611,378 611,378 669,200 669,200 Arbitrage trading account 753,278 753,278 299,999 299,999 Loans receivable 103,650 105,153 106,798 108,299 Cash and cash equivalents 608,393 608,393 795,285 795,285 Trading account receivables from brokers and clearing organizations 29,131 29,131 484,593 484,593 Due from broker 3,749 3,749 — — Liabilities: Due to broker — — 19,416 19,416 Trading account securities sold but not yet purchased 51,348 51,348 51,179 51,179 Subordinated debentures 727,777 750,104 727,630 687,504 Senior notes and other debt 1,759,494 1,927,392 1,760,595 1,914,727 The estimated fair values of the Company’s fixed maturity securities, equity securities available for sale and arbitrage trading account securities are based on various valuation techniques that rely on fair value measurements as described in Note 16 above. The fair value of loans receivable are estimated by using current institutional purchaser yield requirements for loans with similar credit characteristics, which is considered a Level 2 input. The fair value of the senior notes and other debt and the subordinated debentures is based on spreads for similar securities, which is considered a Level 2 input.

Reinsurance Reinsurance

Reinsurance Reinsurance	3 Months Ended
	Mar. 31, 2017
Insurance [Abstract]
Reinsurance [Text Block]	Reinsurance The following is a summary of reinsurance financial information: For the Three Months Ended March 31, (In thousands) 2017 2016 Written premiums: Direct $ 1,721,062 $ 1,709,129 Assumed 215,145 246,568 Ceded (289,369 ) (291,975 ) Total net premiums written $ 1,646,838 $ 1,663,722 Earned premiums: Direct $ 1,613,364 $ 1,568,067 Assumed 208,626 218,367 Ceded (251,948 ) (259,099 ) Total net premiums earned $ 1,570,042 $ 1,527,335 Ceded losses and loss expenses incurred $ 35,192 $ 126,929 Ceded commissions earned $ 56,550 $ 47,973 The Company reinsures a portion of its insurance exposures in order to reduce its net liability on individual risks and catastrophe losses. The Company also cedes premiums to state assigned risk plans and captive insurance companies. Estimated amounts due from reinsurers are reported net of reserves for uncollectible reinsurance of $1 million as of March 31, 2017 and December 31, 2016 .

Fair Value Of Financial Instrum

Fair Value Of Financial Instruments Fair Value of Financial Instruments (Notes)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Measurements The Company’s fixed maturity and equity securities classified as available for sale and its trading account securities are carried at fair value. 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.” The Company utilizes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels, as follows: Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 - Quoted prices for similar assets or valuations based on inputs that are observable. Level 3 - Estimates of fair value based on internal pricing methodologies using unobservable inputs. Unobservable inputs are only used to measure fair value to the extent that observable inputs are not available. Substantially, all of the Company’s fixed maturity securities were priced by independent pricing services. The prices provided by the independent pricing services are estimated based on observable market data in active markets utilizing pricing models and processes, which may include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, sector groupings, matrix pricing and reference data. The pricing services may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs are available for each security evaluation on any given day. The pricing services used by the Company have indicated that they will only produce an estimate of fair value if objectively verifiable information is available. The determination of whether markets are active or inactive is based upon the volume and level of activity for a particular asset class. The Company reviews the prices provided by pricing services for reasonableness and periodically performs independent price tests of a sample of securities to ensure proper valuation. If prices from independent pricing services are not available for fixed maturity securities, the Company estimates the fair value. For Level 2 securities, the Company utilizes pricing models and processes which may include benchmark yields, sector groupings, matrix pricing, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, bids, offers and reference data. Where broker quotes are used, the Company generally requests two or more quotes and sets a price within the range of quotes received based on its assessment of the credibility of the quote and its own evaluation of the security. The Company generally does not adjust quotes received from brokers. For securities traded only in private negotiations, the Company determines fair value based primarily on the cost of such securities, which is adjusted to reflect prices of recent placements of securities of the same issuer, financial projections, credit quality and business developments of the issuer and other relevant information. For Level 3 securities, the Company generally uses a discounted cash flow model to estimate the fair value of fixed maturity securities. The cash flow models are based upon assumptions as to prevailing credit spreads, interest rate and interest rate volatility, time to maturity and subordination levels. Projected cash flows are discounted at rates that are adjusted to reflect illiquidity, where appropriate. The following tables present the assets and liabilities measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 by level: (In thousands) Total Level 1 Level 2 Level 3 March 31, 2017 Assets: Fixed maturity securities available for sale: U.S. government and government agency $ 486,676 $ — $ 486,676 $ — State and municipal 4,461,086 — 4,461,086 — Mortgage-backed securities 1,211,634 — 1,211,634 — Asset-backed securities 2,028,169 — 2,027,990 179 Corporate 4,244,796 — 4,244,796 — Foreign government 901,671 — 901,671 — Total fixed maturity securities available for sale 13,334,032 — 13,333,853 179 Equity securities available for sale: Common stocks 421,329 403,855 8,671 8,803 Preferred stocks 190,049 — 186,387 3,662 Total equity securities available for sale 611,378 403,855 195,058 12,465 Arbitrage trading account 753,278 256,752 496,465 61 Total $ 14,698,688 $ 660,607 $ 14,025,376 $ 12,705 Liabilities: Trading account securities sold but not yet purchased $ 51,348 $ 51,348 $ — $ — December 31, 2016 Assets: Fixed maturity securities available for sale: U.S. government and government agency $ 513,802 $ — $ 513,802 $ — State and municipal 4,519,503 — 4,519,503 — Mortgage-backed securities 1,189,645 — 1,189,645 — Asset-backed securities 1,907,860 — 1,907,677 183 Corporate 4,068,527 — 4,068,527 — Foreign government 902,805 — 902,805 — Total fixed maturity securities available for sale 13,102,142 — 13,101,959 183 Equity securities available for sale: Common stocks 445,858 429,647 7,457 8,754 Preferred stocks 223,342 — 219,680 3,662 Total equity securities available for sale 669,200 429,647 227,137 12,416 Arbitrage trading account 299,999 224,623 75,376 — Total $ 14,071,341 $ 654,270 $ 13,404,472 $ 12,599 Liabilities: Trading account securities sold but not yet purchased $ 51,179 $ 51,089 $ 90 $ — There were no significant transfers between Levels 1 and 2 during the three months ended March 31, 2017 or during the year ended December 31, 2016 . The following tables summarize changes in Level 3 assets and liabilities for the three months ended March 31, 2017 and for the year ended December 31, 2016 : Gains (Losses) Included in: (In thousands) Beginning Balance Earnings (Losses) Other Comprehensive Income (Loss) Impairments Purchases (Sales) Paydowns / Maturities Transfers Ending Balance In / (Out) Three Months Ended March 31, 2017: Assets: Fixed maturities securities available for sale: Asset-backed securities $ 183 $ 1 $ 10 $ — $ — $ (15 ) $ — $ — $ 179 Corporate — — — — — — — — — Total 183 1 10 — — (15 ) — — 179 Equity securities available for sale: Common stocks 8,754 — 49 — — — — — 8,803 Preferred stocks 3,662 — — — — — — 3,662 Total 12,416 — 49 — — — — — 12,465 Arbitrage trading account — — 61 — — — — — 61 Total $ 12,599 $ 1 $ 120 $ — $ — $ (15 ) $ — $ — $ 12,705 Year ended December 31, 2016: Assets: Fixed maturities securities available for sale: Asset-backed securities $ 199 $ 3 $ 16 $ — $ — $ — $ (35 ) $ — $ 183 Corporate 154 177 — — — (331 ) — — — Total 353 180 16 — — (331 ) (35 ) — 183 Equity securities available for sale: Common stocks 7,829 — 160 — 765 — — — 8,754 Preferred stocks 3,624 38 — — — — — — 3,662 Total 11,453 38 160 — 765 — — — 12,416 Arbitrage trading account 176 (176 ) — — — — — — Total $ 11,982 $ 42 $ 176 $ — $ 765 $ (331 ) $ (35 ) $ — $ 12,599 During the three months ended March 31, 2017 and the year ended December 31, 2016, there were no t ransfers out of Level 3. Fair Value of Financial Instruments The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments: March 31, 2017 December 31, 2016 (In thousands) Carrying Value Fair Value Carrying Value Fair Value Assets: Fixed maturity securities $ 13,422,979 $ 13,438,004 $ 13,190,668 $ 13,204,814 Equity securities available for sale 611,378 611,378 669,200 669,200 Arbitrage trading account 753,278 753,278 299,999 299,999 Loans receivable 103,650 105,153 106,798 108,299 Cash and cash equivalents 608,393 608,393 795,285 795,285 Trading account receivables from brokers and clearing organizations 29,131 29,131 484,593 484,593 Due from broker 3,749 3,749 — — Liabilities: Due to broker — — 19,416 19,416 Trading account securities sold but not yet purchased 51,348 51,348 51,179 51,179 Subordinated debentures 727,777 750,104 727,630 687,504 Senior notes and other debt 1,759,494 1,927,392 1,760,595 1,914,727 The estimated fair values of the Company’s fixed maturity securities, equity securities available for sale and arbitrage trading account securities are based on various valuation techniques that rely on fair value measurements as described in Note 16 above. The fair value of loans receivable are estimated by using current institutional purchaser yield requirements for loans with similar credit characteristics, which is considered a Level 2 input. The fair value of the senior notes and other debt and the subordinated debentures is based on spreads for similar securities, which is considered a Level 2 input.

Restricted Stock Units Restrict

Restricted Stock Units Restricted Stock Units (Notes)	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Restricted Stock Units	Restricted Stock Units Pursuant to its stock incentive plan, the Company may issue restricted stock units (RSUs) to employees of the Company and its subsidiaries. The RSUs generally vest three to five years from the award date and are subject to other vesting and forfeiture provisions contained in the award agreement. RSUs are expensed pro-ratably over the vesting period. RSU expenses were $11 million and $9 million for the three months ended March 31, 2017 and 2016 , respectively. A summary of RSUs issued in the three months ended March 31, 2017 and 2016 follows: ($ in thousands) Units Fair Value 2017 1,853 $ 129 2016 5,580 $ 286

Litigation and Contingent Liabi

Litigation and Contingent Liabilities Litigation and Contingent Liabilities	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Text Block]	Litigation and Contingent Liabilities In the ordinary course of business, the Company is subject to disputes, litigation and arbitration arising from its insurance and reinsurance businesses. These matters are generally related to insurance and reinsurance claims and are considered in the establishment of loss and loss expense reserves. In addition, the Company may also become involved in legal actions which seek extra-contractual damages, punitive damages or penalties, including claims alleging bad faith in handling of insurance claims. The Company expects its ultimate liability with respect to such matters will not be material to its financial condition. However, adverse outcomes on such matters are possible, from time to time, and could be material to the Company’s results of operations in any particular financial reporting period.

Industry Segments

Industry Segments	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Industry Segments	The Company’s reportable segments include the following two business segments, plus a corporate segment: • Insurance - primarily commercial insurance business, including excess and surplus lines and admitted lines in the United States, United Kingdom, Continental Europe, South America, Canada, Mexico, Scandinavia, Asia and Australia; and • Reinsurance - reinsurance business on a facultative and treaty basis, primarily in the United States, United Kingdom, Continental Europe, Australia, the Asia-Pacific Region and South Africa. Commencing with the first quarter of 2017, the Company reclassified two businesses from the Insurance segment to the Reinsurance segment. Reclassifications have been made to the Company's 2016 financial information to conform with this presentation. The accounting policies of the segments are the same as those described in the summary of significant accounting policies. Income tax expense and benefits are calculated based upon the Company's overall effective tax rate. Summary financial information about the Company's reporting segments is presented in the following tables. Income (loss) before income taxes by segment includes allocated investment income. Identifiable assets by segment are those assets used in or allocated to the operation of each segment. Revenues (In thousands) Earned Premiums Investment Income Other Total (1) Pre-Tax Income (Loss) Net Income (Loss) to Common Stockholders Three months ended March 31, 2017 Insurance $ 1,413,170 $ 111,909 $ 18,287 $ 1,543,366 $ 199,994 $ 134,095 Reinsurance 156,872 24,778 — 181,650 4,594 3,099 Corporate, other and eliminations (2) — 12,171 80,883 93,054 (72,639 ) (47,773 ) Net investment gains — — 52,348 52,348 52,348 34,026 Total $ 1,570,042 $ 148,858 $ 151,518 $ 1,870,418 $ 184,297 $ 123,447 Three months ended March 31, 2016 Insurance $ 1,366,605 $ 99,860 $ 26,793 $ 1,493,258 $ 199,651 $ 134,778 Reinsurance 160,730 23,770 — 184,500 28,061 19,609 Corporate, other and eliminations (2) — 6,503 115,607 122,110 (60,379 ) (39,649 ) Net investment gains — — 7,343 7,343 7,343 4,773 Total $ 1,527,335 $ 130,133 $ 149,743 $ 1,807,211 $ 174,676 $ 119,511 _________________ (1) Revenues for Insurance includes $184 million and $200 million for the three months ended March 31, 2017 and 2016, respectively, from foreign countries. Revenues for Reinsurance includes $49 million and $54 million for the three months ended March 31, 2017 and 2016, respectively, from foreign countries. (2) Corporate, other and eliminations represent corporate revenues and expenses that are not allocated to business segments. Identifiable Assets (In thousands) March 31, 2017 December 31, 2016 Insurance $ 18,932,563 $ 19,137,758 Reinsurance 2,750,876 2,524,338 Corporate, other and eliminations 1,863,975 1,687,980 Consolidated $ 23,547,414 $ 23,350,076 Net premiums earned by major line of business are as follows: For the Three Months Ended March 31, (In thousands) 2017 2016 Insurance: Other liability $ 451,830 $ 413,528 Workers’ compensation 361,136 343,581 Short-tail lines (1) 309,234 327,076 Commercial automobile 158,126 156,817 Professional liability 132,844 125,603 Total Insurance 1,413,170 1,366,605 Reinsurance: Casualty 94,739 104,305 Property 62,133 56,425 Total Reinsurance 156,872 160,730 Total $ 1,570,042 $ 1,527,335 ______________ (1) Short-tail lines include commercial multi-peril (non-liability), inland marine, accident and health, fidelity and surety, boiler and machinery and other lines.

Per Share Data (Tables)

Per Share Data (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Schedule of Weighted Average Number of Shares [Table Text Block]	The weighted average number of common shares used in the computation of basic and diluted earnings per share was as follows: For the Three Months Ended March 31, (In thousands) 2017 2016 Basic 121,893 122,780 Diluted 128,453 128,529

Acquistions Acquisitions (Table

Acquistions Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Summary of fair value of net assets acquired and liabilities assumed	The following table summarizes the initial estimated fair value of net assets acquired and liabilities assumed for the business combination completed in 2017: (In thousands) 2017 Cash and cash equivalents $ 1,154 Real estate, furniture and equipment 6,434 Goodwill and other intangibles assets 62,406 Other assets 9,417 Total assets acquired 79,411 Other liabilities assumed (1,911 ) Noncontrolling interest (5,000 ) Net assets acquired $ 72,500

Statements of Comprehensive I32

Statements of Comprehensive Income (Loss) Statements of Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Components of changes in accumulated other comprehensive income (loss)	The following tables present the components of the changes in accumulated other comprehensive income (loss) ("AOCI"): (In thousands) Unrealized Investment Gains (Losses) Currency Translation Adjustments Accumulated Other Comprehensive Income (Loss) As of and for the three months ended March 31, 2017: Changes in AOCI Beginning of period $ 427,154 $ (371,586 ) $ 55,568 Other comprehensive income (loss) before reclassifications 19,994 22,735 42,729 Amounts reclassified from AOCI (28,825 ) — (28,825 ) Other comprehensive income (loss) (8,831 ) 22,735 13,904 Unrealized investment gain related to non-controlling interest 19 — 19 End of period $ 418,342 $ (348,851 ) $ 69,491 Amounts reclassified from AOCI Pre-tax $ (44,346 ) (1) $ — $ (44,346 ) Tax effect 15,521 (2) — 15,521 After-tax amounts reclassified $ (28,825 ) $ — $ (28,825 ) Other comprehensive income (loss) Pre-tax $ (9,571 ) $ 22,735 $ 13,164 Tax effect 740 — 740 Other comprehensive income (loss) $ (8,831 ) $ 22,735 $ 13,904 As of and for the three months ended March 31, 2016: Changes in AOCI Beginning of period $ 180,695 $ (247,393 ) $ (66,698 ) Other comprehensive income (loss) before reclassifications 78,242 (2,047 ) 76,195 Amounts reclassified from AOCI (1,387 ) — (1,387 ) Other comprehensive income (loss) 76,855 (2,047 ) 74,808 Unrealized investment gain related to non-controlling interest 14 14 End of period $ 257,564 $ (249,440 ) $ 8,124 Amounts reclassified from AOCI Pre-tax $ (2,134 ) (1) $ — $ (2,134 ) Tax effect 747 (2) — 747 After-tax amounts reclassified $ (1,387 ) $ — $ (1,387 ) Other comprehensive income (loss) Pre-tax $ 114,390 $ (2,047 ) $ 112,343 Tax effect (37,535 ) — (37,535 ) Other comprehensive income (loss) $ 76,855 $ (2,047 ) $ 74,808 _________________________ (1) Net realized investment gains in the consolidated statements of income. (2) Income tax expense in the consolidated statements of income.

Investments In Fixed Maturity33

Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities (Tables)	3 Months Ended
	Mar. 31, 2017
Schedule of Marketable Securities [Line Items]
Amortized cost and fair value of fixed maturity securities by contractual maturity	The amortized cost and fair value of fixed maturity securities at March 31, 2017 , by contractual maturity, are shown below. Actual maturities may differ from contractual maturities because certain issuers may have the right to call or prepay obligations. (In thousands) Amortized Cost Fair Value Due in one year or less $ 1,033,358 $ 1,049,761 Due after one year through five years 5,160,693 5,288,826 Due after five years through ten years 3,273,799 3,386,314 Due after ten years 2,454,761 2,484,502 Mortgage-backed securities 1,227,678 1,228,601 Total $ 13,150,289 $ 13,438,004
Debt Securities [Member]
Schedule of Marketable Securities [Line Items]
Schedule of investments in fixed maturity securities	At March 31, 2017 and December 31, 2016 , investments in fixed maturity securities were as follows: (In thousands) Amortized Cost Gross Unrealized Fair Value Carrying Value Gains Losses March 31, 2017 Held to maturity: State and municipal $ 73,631 $ 13,374 $ — $ 87,005 $ 73,631 Residential mortgage-backed 15,316 1,651 — 16,967 15,316 Total held to maturity 88,947 15,025 — 103,972 88,947 Available for sale: U.S. government and government agency 472,112 16,784 (2,220 ) 486,676 486,676 State and municipal: Special revenue 2,759,063 69,226 (15,887 ) 2,812,402 2,812,402 State general obligation 504,312 18,952 (3,295 ) 519,969 519,969 Pre-refunded 349,697 20,013 (146 ) 369,564 369,564 Corporate backed 376,664 8,290 (5,639 ) 379,315 379,315 Local general obligation 360,941 20,497 (1,602 ) 379,836 379,836 Total state and municipal 4,350,677 136,978 (26,569 ) 4,461,086 4,461,086 Mortgage-backed securities: Residential (1) 1,067,779 14,081 (13,030 ) 1,068,830 1,068,830 Commercial 144,583 347 (2,126 ) 142,804 142,804 Total mortgage-backed securities 1,212,362 14,428 (15,156 ) 1,211,634 1,211,634 Asset-backed 2,029,812 7,837 (9,480 ) 2,028,169 2,028,169 Corporate: Industrial 2,391,507 70,783 (5,330 ) 2,456,960 2,456,960 Financial 1,445,707 45,431 (6,881 ) 1,484,257 1,484,257 Utilities 238,801 10,578 (2,049 ) 247,330 247,330 Other 55,808 471 (30 ) 56,249 56,249 Total corporate 4,131,823 127,263 (14,290 ) 4,244,796 4,244,796 Foreign 864,556 38,692 (1,577 ) 901,671 901,671 Total available for sale 13,061,342 341,982 (69,292 ) 13,334,032 13,334,032 Total investments in fixed maturity securities $ 13,150,289 $ 357,007 $ (69,292 ) $ 13,438,004 $ 13,422,979 (In thousands) Amortized Gross Unrealized Fair Carrying Gains Losses December 31, 2016 Held to maturity: State and municipal $ 72,582 $ 12,453 $ — $ 85,035 $ 72,582 Residential mortgage-backed 15,944 1,693 — 17,637 15,944 Total held to maturity 88,526 14,146 — 102,672 88,526 Available for sale: U.S. government and government agency 496,187 20,208 (2,593 ) 513,802 513,802 State and municipal: Special revenue 2,791,211 58,559 (26,315 ) 2,823,455 2,823,455 State general obligation 524,682 16,964 (5,139 ) 536,507 536,507 Pre-refunded 356,535 19,181 (165 ) 375,551 375,551 Corporate backed 410,933 6,172 (6,452 ) 410,653 410,653 Local general obligation 360,022 15,682 (2,367 ) 373,337 373,337 Total state and municipal 4,443,383 116,558 (40,438 ) 4,519,503 4,519,503 Mortgage-backed securities: Residential (1) 1,034,301 15,431 (12,950 ) 1,036,782 1,036,782 Commercial 155,540 304 (2,981 ) 152,863 152,863 Total mortgage-backed securities 1,189,841 15,735 (15,931 ) 1,189,645 1,189,645 Asset-backed 1,913,830 5,971 (11,941 ) 1,907,860 1,907,860 Corporate: Industrial 2,315,567 71,007 (7,174 ) 2,379,400 2,379,400 Financial 1,369,001 39,543 (11,270 ) 1,397,274 1,397,274 Utilities 229,154 10,801 (2,411 ) 237,544 237,544 Other 54,073 299 (63 ) 54,309 54,309 Total corporate 3,967,795 121,650 (20,918 ) 4,068,527 4,068,527 Foreign 858,773 46,794 (2,762 ) 902,805 902,805 Total available for sale 12,869,809 326,916 (94,583 ) 13,102,142 13,102,142 Total investments in fixed maturity securities $ 12,958,335 $ 341,062 $ (94,583 ) $ 13,204,814 $ 13,190,668 ____________ (1) Gross unrealized losses for residential mortgage-backed securities include $717,960 and $818,691 as of March 31, 2017 and December 31, 2016 , respectively, related to the non-credit portion of other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income.

Reserves for Loss and Loss Ex34

Reserves for Loss and Loss Expenses Reserves for Loss and Loss Expenses (Tables)	3 Months Ended
	Mar. 31, 2017
Insurance [Abstract]
Reconciliation of Net Reserves	The table below provides a reconciliation of the beginning and ending reserve balances: March 31, (In thousands) 2017 2016 Net reserves at beginning of year $ 9,590,265 $ 9,244,872 Net provision for losses and loss expenses: Claims occurring during the current year (1) 958,684 916,649 Increase (decrease) in estimates for claims occurring in prior years (2) (3) 8,727 (5,601 ) Loss reserve discount accretion 12,192 11,273 Total 979,603 922,321 Net payments for claims: Current year 97,461 259,633 Prior year 773,571 555,884 Total 871,032 815,517 Foreign currency translation 23,204 20,760 Net reserves at end of period 9,722,040 9,372,436 Ceded reserve at end of period 1,502,284 1,415,906 Gross reserves at end of period $ 11,224,324 $ 10,788,342 _______________________________________ (1) Claims occurring during the current year are net of loss reserve discounts of $ 5,761,000 and $ 19,072,000 in 2017 and 2016, respectively. (2) The increase in estimates for claims occurring in prior years is net of loss reserve discount. On an undiscounted basis, the estimates for claims occurring in prior years increased by $ 4,841,000 and decreased by $ 23,559,000 in 2017 and 2016, respectively.

Investments in Equity Securit35

Investments in Equity Securities Investments in Equity Securities (Tables)	3 Months Ended
	Mar. 31, 2017
Equity securities available for sale
Schedule of Available-for-sale Securities [Line Items]
Schedule of Investments in Equity Securities	At March 31, 2017 and December 31, 2016 , investments in equity securities were as follows: (In thousands) Cost Gross Unrealized Fair Value Carrying Value Gains Losses March 31, 2017 Common stocks $ 90,080 $ 333,397 $ (2,148 ) $ 421,329 $ 421,329 Preferred stocks 121,360 70,795 (2,106 ) 190,049 190,049 Total $ 211,440 $ 404,192 $ (4,254 ) $ 611,378 $ 611,378 December 31, 2016 Common stocks $ 94,998 $ 351,906 $ (1,046 ) $ 445,858 $ 445,858 Preferred stocks 125,589 101,392 (3,639 ) 223,342 223,342 Total $ 220,587 $ 453,298 $ (4,685 ) $ 669,200 $ 669,200

Net Investment Income (Tables)

Net Investment Income (Tables)	3 Months Ended
	Mar. 31, 2017
Net Investment Income [Abstract]
Schedule of Net Investment Income	Net investment income consisted of the following: For the Three Months Ended March 31, (In thousands) 2017 2016 Investment income earned on: Fixed maturity securities, including cash and cash equivalents and loans receivable $ 112,346 $ 108,835 Investment funds 26,649 16,636 Arbitrage trading account 6,360 3,190 Real estate 4,566 2,717 Equity securities available for sale 639 868 Gross investment income 150,560 132,246 Investment expense (1,702 ) (2,113 ) Net investment income $ 148,858 $ 130,133

Investment Funds Investment F37

Investment Funds Investment Funds (Tables)	3 Months Ended
	Mar. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Net Investment Funds	Investment funds consist of the following: Carrying Value as of Income (Loss) from Investment Funds March 31, December 31, For the Three Months Ended March 31, (In thousands) 2017 2016 2017 2016 Real estate $ 654,501 $ 641,783 $ 4,532 $ 17,037 Energy 96,161 91,448 3,245 (3,924 ) Hedge equity 74,779 73,913 866 (2,852 ) Other funds 413,117 391,002 18,006 6,375 Total $ 1,238,558 $ 1,198,146 $ 26,649 $ 16,636

Real Estate Real Estate (Tables

Real Estate Real Estate (Tables)	3 Months Ended
	Mar. 31, 2017
Real Estate [Abstract]
Schedule of Real Estate Investments	Investment in real estate represents directly owned property held for investment, as follows: Carrying Value March 31, December 31, (In thousands) 2017 2016 Properties in operation $ 448,422 $ 457,237 Properties under development 789,316 727,744 Total $ 1,237,738 $ 1,184,981

Loans Receivable Loans Receiv39

Loans Receivable Loans Receivable (Tables)	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Schedule of Loans Receivable	Loans receivable are as follows: (In thousands) March 31, 2017 December 31, 2016 Amortized cost (net of valuation allowance): Real estate loans $ 89,206 $ 92,415 Commercial loans 14,444 14,383 Total $ 103,650 $ 106,798 Fair value: Real estate loans $ 89,206 $ 92,415 Commercial loans 15,947 15,884 Total $ 105,153 $ 108,299 Valuation allowance: Specific $ 1,200 $ 1,200 General 2,183 2,197 Total $ 3,383 $ 3,397 For the Three Months Ended March 31, 2017 2016 Increase (decrease) in valuation allowance $ (14 ) $ 568

Realized And Unrealized Inves40

Realized And Unrealized Investment Gains (Losses) (Tables)	3 Months Ended
	Mar. 31, 2017
Realized and Unrealized Investment Gains (Losses) [Abstract]
Realized and Unrealized Investment Gains (Losses)	Realized and unrealized investment gains (losses) are as follows: For the Three Months Ended March 31, (In thousands) 2017 2016 Realized investment gains (losses): Fixed maturity securities: Gains $ 5,605 $ 23,064 Losses (3,965 ) (2,940 ) Equity securities available for sale 42,707 125 Investment funds 1,267 (460 ) Real estate 3,300 5,024 Other 3,434 644 Net realized gains on investments sales 52,348 25,457 Other-than-temporary impairments (1) — (18,114 ) Net investment gains 52,348 7,343 Income tax expense (18,322 ) (2,570 ) After-tax net realized investment gains $ 34,026 $ 4,773
Unrealized Gain (Loss) on Investments	Change in unrealized investment gains (losses) of available for sale securities: Fixed maturity securities $ 37,984 $ 92,428 Previously impaired fixed maturity securities 101 (55 ) Equity securities available for sale (48,862 ) 13,137 Investment funds 1,206 8,880 Total change in unrealized investment gains (losses) (9,571 ) 114,390 Income tax benefit (expense) 740 (37,535 ) Noncontrolling interests 19 14 After-tax change in unrealized investment gains (losses) of available for sale securities $ (8,812 ) $ 76,869 ______________________ (1) There were no other than temporary impairments (OTTI) for the three months ended March 31, 2017. OTTI for the three months ended March 31, 2016 of $18.1 million related to common stock.

Securities In An Unrealized L41

Securities In An Unrealized Loss Position Securities In An Unrealized Loss Position (Tables)	3 Months Ended
	Mar. 31, 2017
Statement of Financial Position [Abstract]
Securities in an unrealized loss position	The following tables summarize all securities in an unrealized loss position at March 31, 2017 and December 31, 2016 by the length of time those securities have been continuously in an unrealized loss position: Less Than 12 Months 12 Months or Greater Total (In thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses March 31, 2017 U.S. government and government agency $ 95,253 $ 954 $ 33,071 $ 1,266 $ 128,324 $ 2,220 State and municipal 1,111,978 22,836 150,439 3,733 1,262,417 26,569 Mortgage-backed securities 618,642 10,013 140,791 5,143 759,433 15,156 Asset-backed securities 1,204,310 4,386 95,421 5,094 1,299,731 9,480 Corporate 867,293 8,126 61,732 6,164 929,025 14,290 Foreign government 115,542 1,320 4,495 257 120,037 1,577 Fixed maturity securities 4,013,018 47,635 485,949 21,657 4,498,967 69,292 Common stocks 18,875 1,173 8,803 975 27,678 2,148 Preferred stocks — — 23,567 2,106 23,567 2,106 Equity securities available for sale 18,875 1,173 32,370 3,081 51,245 4,254 Total $ 4,031,893 $ 48,808 $ 518,319 $ 24,738 $ 4,550,212 $ 73,546 December 31, 2016 U.S. government and government agency $ 112,709 $ 1,252 $ 35,450 $ 1,341 $ 148,159 $ 2,593 State and municipal 1,562,614 35,553 133,034 4,885 1,695,648 40,438 Mortgage-backed securities 625,903 11,103 109,066 4,828 734,969 15,931 Asset-backed securities 1,010,836 5,340 201,693 6,601 1,212,529 11,941 Corporate 1,035,245 13,448 65,147 7,470 1,100,392 20,918 Foreign government 213,246 1,985 24,820 777 238,066 2,762 Fixed maturity securities 4,560,553 68,681 569,210 25,902 5,129,763 94,583 Common stocks 336 22 8,755 1,024 9,091 1,046 Preferred stocks — — 22,034 3,639 22,034 3,639 Equity securities available for sale 336 22 30,789 4,663 31,125 4,685 Total $ 4,560,889 $ 68,703 $ 599,999 $ 30,565 $ 5,160,888 $ 99,268
Non-Investment Grade Fixed Maturity Securities	Fixed Maturity Securities – A summary of the Company’s non-investment grade fixed maturity securities that were in an unrealized loss position at March 31, 2017 is presented in the table below: ($ in thousands) Number of Securities Aggregate Fair Value Gross Unrealized Loss State and municipal 1 $ 5,136 $ 3,725 Mortgage-backed securities 9 19,647 924 Corporate 4 19,990 741 Foreign government 11 51,901 681 Asset-backed securities 6 9,615 173 Total 31 $ 106,289 $ 6,244

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Assets And Liabilities Measured At Fair value, On A Recurring Basis	The following tables present the assets and liabilities measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 by level: (In thousands) Total Level 1 Level 2 Level 3 March 31, 2017 Assets: Fixed maturity securities available for sale: U.S. government and government agency $ 486,676 $ — $ 486,676 $ — State and municipal 4,461,086 — 4,461,086 — Mortgage-backed securities 1,211,634 — 1,211,634 — Asset-backed securities 2,028,169 — 2,027,990 179 Corporate 4,244,796 — 4,244,796 — Foreign government 901,671 — 901,671 — Total fixed maturity securities available for sale 13,334,032 — 13,333,853 179 Equity securities available for sale: Common stocks 421,329 403,855 8,671 8,803 Preferred stocks 190,049 — 186,387 3,662 Total equity securities available for sale 611,378 403,855 195,058 12,465 Arbitrage trading account 753,278 256,752 496,465 61 Total $ 14,698,688 $ 660,607 $ 14,025,376 $ 12,705 Liabilities: Trading account securities sold but not yet purchased $ 51,348 $ 51,348 $ — $ — December 31, 2016 Assets: Fixed maturity securities available for sale: U.S. government and government agency $ 513,802 $ — $ 513,802 $ — State and municipal 4,519,503 — 4,519,503 — Mortgage-backed securities 1,189,645 — 1,189,645 — Asset-backed securities 1,907,860 — 1,907,677 183 Corporate 4,068,527 — 4,068,527 — Foreign government 902,805 — 902,805 — Total fixed maturity securities available for sale 13,102,142 — 13,101,959 183 Equity securities available for sale: Common stocks 445,858 429,647 7,457 8,754 Preferred stocks 223,342 — 219,680 3,662 Total equity securities available for sale 669,200 429,647 227,137 12,416 Arbitrage trading account 299,999 224,623 75,376 — Total $ 14,071,341 $ 654,270 $ 13,404,472 $ 12,599 Liabilities: Trading account securities sold but not yet purchased $ 51,179 $ 51,089 $ 90 $ —
Summarize Changes In Level 3 Assets	The following tables summarize changes in Level 3 assets and liabilities for the three months ended March 31, 2017 and for the year ended December 31, 2016 : Gains (Losses) Included in: (In thousands) Beginning Balance Earnings (Losses) Other Comprehensive Income (Loss) Impairments Purchases (Sales) Paydowns / Maturities Transfers Ending Balance In / (Out) Three Months Ended March 31, 2017: Assets: Fixed maturities securities available for sale: Asset-backed securities $ 183 $ 1 $ 10 $ — $ — $ (15 ) $ — $ — $ 179 Corporate — — — — — — — — — Total 183 1 10 — — (15 ) — — 179 Equity securities available for sale: Common stocks 8,754 — 49 — — — — — 8,803 Preferred stocks 3,662 — — — — — — 3,662 Total 12,416 — 49 — — — — — 12,465 Arbitrage trading account — — 61 — — — — — 61 Total $ 12,599 $ 1 $ 120 $ — $ — $ (15 ) $ — $ — $ 12,705 Year ended December 31, 2016: Assets: Fixed maturities securities available for sale: Asset-backed securities $ 199 $ 3 $ 16 $ — $ — $ — $ (35 ) $ — $ 183 Corporate 154 177 — — — (331 ) — — — Total 353 180 16 — — (331 ) (35 ) — 183 Equity securities available for sale: Common stocks 7,829 — 160 — 765 — — — 8,754 Preferred stocks 3,624 38 — — — — — — 3,662 Total 11,453 38 160 — 765 — — — 12,416 Arbitrage trading account 176 (176 ) — — — — — — Total $ 11,982 $ 42 $ 176 $ — $ 765 $ (331 ) $ (35 ) $ — $ 12,599

Reinsurance (Tables)

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2017
Reinsurance Disclosures [Abstract]
Reinsurance Financial Information	The following is a summary of reinsurance financial information: For the Three Months Ended March 31, (In thousands) 2017 2016 Written premiums: Direct $ 1,721,062 $ 1,709,129 Assumed 215,145 246,568 Ceded (289,369 ) (291,975 ) Total net premiums written $ 1,646,838 $ 1,663,722 Earned premiums: Direct $ 1,613,364 $ 1,568,067 Assumed 208,626 218,367 Ceded (251,948 ) (259,099 ) Total net premiums earned $ 1,570,042 $ 1,527,335 Ceded losses and loss expenses incurred $ 35,192 $ 126,929 Ceded commissions earned $ 56,550 $ 47,973

Fair Value of Financial Instr44

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Carrying Amounts And Estimated Fair Values Of Financial Instruments	The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments: March 31, 2017 December 31, 2016 (In thousands) Carrying Value Fair Value Carrying Value Fair Value Assets: Fixed maturity securities $ 13,422,979 $ 13,438,004 $ 13,190,668 $ 13,204,814 Equity securities available for sale 611,378 611,378 669,200 669,200 Arbitrage trading account 753,278 753,278 299,999 299,999 Loans receivable 103,650 105,153 106,798 108,299 Cash and cash equivalents 608,393 608,393 795,285 795,285 Trading account receivables from brokers and clearing organizations 29,131 29,131 484,593 484,593 Due from broker 3,749 3,749 — — Liabilities: Due to broker — — 19,416 19,416 Trading account securities sold but not yet purchased 51,348 51,348 51,179 51,179 Subordinated debentures 727,777 750,104 727,630 687,504 Senior notes and other debt 1,759,494 1,927,392 1,760,595 1,914,727

Restricted Stock Units (Tables)

Restricted Stock Units (Tables)	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary Of Restricted Stock Units Issued	A summary of RSUs issued in the three months ended March 31, 2017 and 2016 follows: ($ in thousands) Units Fair Value 2017 1,853 $ 129 2016 5,580 $ 286

Industry Segments (Tables)

Industry Segments (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Financial Information Of Company Operating Segments	Revenues (In thousands) Earned Premiums Investment Income Other Total (1) Pre-Tax Income (Loss) Net Income (Loss) to Common Stockholders Three months ended March 31, 2017 Insurance $ 1,413,170 $ 111,909 $ 18,287 $ 1,543,366 $ 199,994 $ 134,095 Reinsurance 156,872 24,778 — 181,650 4,594 3,099 Corporate, other and eliminations (2) — 12,171 80,883 93,054 (72,639 ) (47,773 ) Net investment gains — — 52,348 52,348 52,348 34,026 Total $ 1,570,042 $ 148,858 $ 151,518 $ 1,870,418 $ 184,297 $ 123,447 Three months ended March 31, 2016 Insurance $ 1,366,605 $ 99,860 $ 26,793 $ 1,493,258 $ 199,651 $ 134,778 Reinsurance 160,730 23,770 — 184,500 28,061 19,609 Corporate, other and eliminations (2) — 6,503 115,607 122,110 (60,379 ) (39,649 ) Net investment gains — — 7,343 7,343 7,343 4,773 Total $ 1,527,335 $ 130,133 $ 149,743 $ 1,807,211 $ 174,676 $ 119,511 _________________ (1) Revenues for Insurance includes $184 million and $200 million for the three months ended March 31, 2017 and 2016, respectively, from foreign countries. Revenues for Reinsurance includes $49 million and $54 million for the three months ended March 31, 2017 and 2016, respectively, from foreign countries. (2) Corporate, other and eliminations represent corporate revenues and expenses that are not allocated to business segments.
Identifiable Assets By Segment	Identifiable Assets (In thousands) March 31, 2017 December 31, 2016 Insurance $ 18,932,563 $ 19,137,758 Reinsurance 2,750,876 2,524,338 Corporate, other and eliminations 1,863,975 1,687,980 Consolidated $ 23,547,414 $ 23,350,076
Net Premiums Earned By Major Line Of Business	Net premiums earned by major line of business are as follows: For the Three Months Ended March 31, (In thousands) 2017 2016 Insurance: Other liability $ 451,830 $ 413,528 Workers’ compensation 361,136 343,581 Short-tail lines (1) 309,234 327,076 Commercial automobile 158,126 156,817 Professional liability 132,844 125,603 Total Insurance 1,413,170 1,366,605 Reinsurance: Casualty 94,739 104,305 Property 62,133 56,425 Total Reinsurance 156,872 160,730 Total $ 1,570,042 $ 1,527,335

General General (Details)

General General (Details)	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Federal Income Tax Rate	35.00%

Per Share Data (Weighted Averag

Per Share Data (Weighted Average Number of Common Shares Used In the Computation of Basic and Diluted Earnings per Share) (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Basic (shares)	121,893	122,780
Diluted (shares)	128,453	128,529

Acquistions (Details)

Acquistions (Details) - Selling and Marketing Expense [Member] $ in Thousands	Mar. 31, 2017USD ($)
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	90.00%
Net assets acquired	$ 72,500

Estimated Fair Value of Net Ass

Estimated Fair Value of Net Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 144,513	$ 144,513
Premiums and fees receivable	1,766,478	1,701,854
Noncontrolling interests	(38,935)	$ (33,926)
Selling and Marketing Expense [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	1,154
Real estate, furniture and equipment	6,434
Goodwill and other intangibles assets	62,406
Other assets	9,417
Total assets acquired	79,411
Other liabilities assumed	(1,911)
Noncontrolling interests	(5,000)
Net assets acquired	$ 72,500

Statements of Comprehensive I51

Statements of Comprehensive Income (Loss) Statements of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period		$ 55,568
Other comprehensive income (loss)		13,904	$ 74,808
Accumulated Other Comprehensive Income (Loss), End of Period		69,491
Net realized investment gains		52,348	25,457
Income before income taxes		184,297	174,676
Income before taxes		603,700	582,459
Tax effect		(59,623)	(54,428)
After-tax amounts reclassified		124,674	120,248
Unrealized investment gains, pre-tax		(9,571)	114,390
Unrealized investment gains, tax effect		740	(37,535)
Unrealized investment gains, after-tax amounts		(8,831)	76,855
Currency translation adjustment, pre-tax		22,735	(2,047)
Currency translation adjustment, tax effect		0	0
Change in unrealized currency translation adjustments		22,735	(2,047)
Other comprehensive income (loss), pre-tax		13,164	112,343
Other comprehensive income (loss), tax effect		740	(37,535)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period		427,154	180,695
Other comprehensive income (loss) before reclassifications		19,994	78,242
Amounts reclassified from AOCI		(28,825)	(1,387)
Other comprehensive income (loss)		(8,831)	76,855
Unrealized investment gain related to non-controlling interest		19	14
Accumulated Other Comprehensive Income (Loss), End of Period		418,342	257,564
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period		(371,586)	(247,393)
Other comprehensive income (loss) before reclassifications		22,735	(2,047)
Amounts reclassified from AOCI		0	0
Other comprehensive income (loss)		22,735	(2,047)
Unrealized investment gain related to non-controlling interest		0
Accumulated Other Comprehensive Income (Loss), End of Period		(348,851)	(249,440)
Change in unrealized currency translation adjustments		22,735	(2,047)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period		55,568	(66,698)
Other comprehensive income (loss) before reclassifications		42,729	76,195
Amounts reclassified from AOCI		(28,825)	(1,387)
Other comprehensive income (loss)		13,904	74,808
Unrealized investment gain related to non-controlling interest		19	14
Accumulated Other Comprehensive Income (Loss), End of Period		69,491	8,124
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net realized investment gains	[1]	(44,346)	(2,134)
Tax effect	[2]	(15,521)	(747)
After-tax amounts reclassified		(28,825)	(1,387)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes		0	0
Tax effect		0	0
After-tax amounts reclassified		0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes		(44,346)	(2,134)
Tax effect		15,521	747
After-tax amounts reclassified		$ (28,825)	$ (1,387)
[1]	(1) Net realized investment gains in the consolidated statements of income.
[2]	(2) Income tax expense in the consolidated statements of income.

Statements of Cash Flow (Detail

Statements of Cash Flow (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Supplemental Cash Flow Information [Abstract]
Interest payments	$ 61,782,000	$ 56,968,000
Income taxes paid	$ 1,610,000	$ 5,644,000

Investments In Fixed Maturity53

Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities (Investments in fixed maturity securities) (Details) - USD ($)		Mar. 31, 2017		Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		$ 88,947,000		$ 88,526,000
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain		15,025,000		14,146,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0		0
Total held to maturity, Fair Value		103,972,000		102,672,000
Total held to maturity, Carrying Value		88,947,000		88,526,000
Total available for sale, Amortized Cost		13,061,342,000		12,869,809,000
Total available for sale, Gross Unrealized Gains		341,982,000		326,916,000
Total available for sale, Gross Unrealized Losses		(69,292,000)		(94,583,000)
Total available for sale, Fair Value		13,334,032,000		13,102,142,000
Total available for sale, Carrying Value		13,334,032,000		13,102,142,000
Total investments in fixed maturity securities, Amortized Value		13,150,289,000		12,958,335,000
Total investments in fixed maturity securities, Gross Unrealized Gains		357,007,000		341,062,000
Total investments in fixed maturity securities, Gross Unrealized Losses		(69,292,000)		(94,583,000)
Total investments in fixed maturity securities, Fair Value		13,438,004,000		13,204,814,000
Total investments in fixed maturity securities, Carrying Value		$ 13,422,979,000		13,190,668,000
Minimum ownership of Common stockholders equity		10.00%
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		$ 864,556,000		858,773,000
Total available for sale, Gross Unrealized Gains		38,692,000		46,794,000
Total available for sale, Gross Unrealized Losses		(1,577,000)		(2,762,000)
Total available for sale, Fair Value		901,671,000		902,805,000
Total available for sale, Carrying Value		901,671,000		902,805,000
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		144,583,000		155,540,000
Total available for sale, Gross Unrealized Gains		347,000		304,000
Total available for sale, Gross Unrealized Losses		(2,126,000)		(2,981,000)
Total available for sale, Fair Value		142,804,000		152,863,000
Total available for sale, Carrying Value		142,804,000		152,863,000
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		472,112,000		496,187,000
Total available for sale, Gross Unrealized Gains		16,784,000		20,208,000
Total available for sale, Gross Unrealized Losses		(2,220,000)		(2,593,000)
Total available for sale, Fair Value		486,676,000		513,802,000
Total available for sale, Carrying Value		486,676,000		513,802,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		2,759,063,000		2,791,211,000
Total available for sale, Gross Unrealized Gains		69,226,000		58,559,000
Total available for sale, Gross Unrealized Losses		(15,887,000)		(26,315,000)
Total available for sale, Fair Value		2,812,402,000		2,823,455,000
Total available for sale, Carrying Value		2,812,402,000		2,823,455,000
Corporation [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		376,664,000		410,933,000
Total available for sale, Gross Unrealized Gains		8,290,000		6,172,000
Total available for sale, Gross Unrealized Losses		(5,639,000)		(6,452,000)
Total available for sale, Fair Value		379,315,000		410,653,000
Total available for sale, Carrying Value		379,315,000		410,653,000
Debt, State Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		504,312,000		524,682,000
Total available for sale, Gross Unrealized Gains		18,952,000		16,964,000
Total available for sale, Gross Unrealized Losses		(3,295,000)		(5,139,000)
Total available for sale, Fair Value		519,969,000		536,507,000
Total available for sale, Carrying Value		519,969,000		536,507,000
Revenue Subject to Refund [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		349,697,000		356,535,000
Total available for sale, Gross Unrealized Gains		20,013,000		19,181,000
Total available for sale, Gross Unrealized Losses		(146,000)		(165,000)
Total available for sale, Fair Value		369,564,000		375,551,000
Total available for sale, Carrying Value		369,564,000		375,551,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	[1]	1,067,779,000		1,034,301,000
Total available for sale, Gross Unrealized Gains	[1]	14,081,000		15,431,000
Total available for sale, Gross Unrealized Losses	[1]	(13,030,000)		(12,950,000)
Total available for sale, Fair Value		1,068,830,000	[1]	1,036,782,000
Total available for sale, Carrying Value	[1]	1,068,830,000		1,036,782,000
Non-credit portion of other-than-temporary impairments (OTTI)		717,960		818,691
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		4,131,823,000		3,967,795,000
Total available for sale, Gross Unrealized Gains		127,263,000		121,650,000
Total available for sale, Gross Unrealized Losses		(14,290,000)		(20,918,000)
Total available for sale, Fair Value		4,244,796,000		4,068,527,000
Total available for sale, Carrying Value		4,244,796,000		4,068,527,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		4,350,677,000		4,443,383,000
Total available for sale, Gross Unrealized Gains		136,978,000		116,558,000
Total available for sale, Gross Unrealized Losses		(26,569,000)		(40,438,000)
Total available for sale, Fair Value		4,461,086,000		4,519,503,000
Total available for sale, Carrying Value		4,461,086,000		4,519,503,000
Debt, Local Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		360,941,000		360,022,000
Total available for sale, Gross Unrealized Gains		20,497,000		15,682,000
Total available for sale, Gross Unrealized Losses		(1,602,000)		(2,367,000)
Total available for sale, Fair Value		379,836,000		373,337,000
Total available for sale, Carrying Value		379,836,000		373,337,000
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,212,362,000		1,189,841,000
Total available for sale, Gross Unrealized Gains		14,428,000		15,735,000
Total available for sale, Gross Unrealized Losses		(15,156,000)		(15,931,000)
Total available for sale, Fair Value		1,211,634,000		1,189,645,000
Total available for sale, Carrying Value		1,211,634,000		1,189,645,000
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		2,029,812,000		1,913,830,000
Total available for sale, Gross Unrealized Gains		7,837,000		5,971,000
Total available for sale, Gross Unrealized Losses		(9,480,000)		(11,941,000)
Total available for sale, Fair Value		2,028,169,000		1,907,860,000
Total available for sale, Carrying Value		2,028,169,000		1,907,860,000
Industrial Property [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		2,391,507,000		2,315,567,000
Total available for sale, Gross Unrealized Gains		70,783,000		71,007,000
Total available for sale, Gross Unrealized Losses		(5,330,000)		(7,174,000)
Total available for sale, Fair Value		2,456,960,000		2,379,400,000
Total available for sale, Carrying Value		2,456,960,000		2,379,400,000
Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,445,707,000		1,369,001,000
Total available for sale, Gross Unrealized Gains		45,431,000		39,543,000
Total available for sale, Gross Unrealized Losses		(6,881,000)		(11,270,000)
Total available for sale, Fair Value		1,484,257,000		1,397,274,000
Total available for sale, Carrying Value		1,484,257,000		1,397,274,000
Public Utility, Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		238,801,000		229,154,000
Total available for sale, Gross Unrealized Gains		10,578,000		10,801,000
Total available for sale, Gross Unrealized Losses		(2,049,000)		(2,411,000)
Total available for sale, Fair Value		247,330,000		237,544,000
Total available for sale, Carrying Value		247,330,000		237,544,000
Other Security Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		55,808,000		54,073,000
Total available for sale, Gross Unrealized Gains		471,000		299,000
Total available for sale, Gross Unrealized Losses		(30,000)		(63,000)
Total available for sale, Fair Value		56,249,000		54,309,000
Total available for sale, Carrying Value		56,249,000		54,309,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		73,631,000		72,582,000
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain		13,374,000		12,453,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0		0
Total held to maturity, Fair Value		87,005,000		85,035,000
Total held to maturity, Carrying Value		73,631,000		72,582,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		15,316,000		15,944,000
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain		1,651,000		1,693,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0		0
Total held to maturity, Fair Value		16,967,000		17,637,000
Total held to maturity, Carrying Value		$ 15,316,000		$ 15,944,000
[1]	Gross unrealized losses for residential mortgage-backed securities include $717,960 and $818,691 as of March 31, 2017 and December 31, 2016, respectively, related to the non-credit portion of other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income.

Reserves for Loss and Loss Ex54

Reserves for Loss and Loss Expenses (Reconciliation of Net Reserves) (Details) - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Insurance [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Net		$ 9,722,040,000	$ 9,372,436,000	$ 9,590,265,000	$ 9,244,872,000
Current Year Claims and Claims Adjustment Expense	[1]	958,684,000	916,649,000
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims, Adjustment	[2]	(8,727,000)	(5,601,000)
Liability For Unpaid Claims And Claims Adjustment Expense Incurred Loss Reserve Discount Accretion		(12,192,000)	11,273,000
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims		979,603,000	922,321,000
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year		97,461,000	259,633,000
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years		773,571,000	555,884,000
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid		871,032,000	815,517,000
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Exchange Translation		23,204,000	20,760,000
Reinsurance Recoverables, Gross		1,502,284,000	1,415,906,000
Liability for Claims and Claims Adjustment Expense		11,224,324,000	10,788,342,000	11,197,195,000
Workers' Compensation Discount, Amount		5,761,000		19,072,000
Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims Undiscounted Basis Prior Years, Increase (Decrease)		4,841,000		23,559,000
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		$ 2,000,000	12,300,000
Reinsurance-Global Segment [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense			$ 700,000
Insurance-Domestic Segment [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense				$ 11,600,000
[1]	Claims occurring during the current year are net of loss reserve discounts of $5,761,000 and $19,072,000 in 2017 and 2016, respectively.
[2]	The increase in estimates for claims occurring in prior years is net of loss reserve discount. On an undiscounted basis, the estimates for claims occurring in prior years increased by $4,841,000 and decreased by $23,559,000 in 2017 and 2016, respectively.

Investments In Fixed Maturity55

Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities (Amortized cost and fair value of fixed maturity securities) (Details) - USD ($) $ in Thousands		Mar. 31, 2017		Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment		$ 88,947		$ 88,526
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain		15,025		14,146
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss		0		0
Held-to-maturity Securities, Fair Value		103,972		102,672
Held-to-maturity Securities		88,947		88,526
Available-for-sale Debt Securities, Amortized Cost Basis		13,061,342		12,869,809
Available For Sale Securities Debt Securities Gross Unrealized Gain		341,982		326,916
Available For Sale Securities Debt Securities Gross Unrealized Losses		(69,292)		(94,583)
Available For Sale Securities Debt Securities Fair Value		13,334,032		13,102,142
Available-for-sale Securities, Debt Securities		13,334,032		13,102,142
Marketable Securities Fixed Maturities Gross Unrealized Gains		357,007		341,062
Fixed maturity securities		13,422,979		13,190,668
Marketable Securities Fixed Maturities Gross Unrealized Losses		69,292		94,583
Amortized Cost, Due in one year or less		1,033,358
Amortized Cost, Due after one year through five years		5,160,693
Amortized Cost, Due after five years through ten years		3,273,799
Amortized Cost, Due after ten years		2,454,761
Amortized Cost, Mortgaged-backed securities		1,227,678
Total investments in fixed maturity securities, Amortized Value		13,150,289		12,958,335
Fair Value, Due in one year or less		1,049,761
Fair Value, Due after one year through five years		5,288,826
Fair Value, Due after five years through ten years		3,386,314
Fair Value, Due after ten years		2,484,502
Fair Value, Mortgage-backed securities		1,228,601
Total investments in fixed maturity securities, Fair Value		13,438,004		13,204,814
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		864,556		858,773
Available For Sale Securities Debt Securities Gross Unrealized Gain		38,692		46,794
Available For Sale Securities Debt Securities Gross Unrealized Losses		(1,577)		(2,762)
Available For Sale Securities Debt Securities Fair Value		901,671		902,805
Available-for-sale Securities, Debt Securities		901,671		902,805
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		144,583		155,540
Available For Sale Securities Debt Securities Gross Unrealized Gain		347		304
Available For Sale Securities Debt Securities Gross Unrealized Losses		(2,126)		(2,981)
Available For Sale Securities Debt Securities Fair Value		142,804		152,863
Available-for-sale Securities, Debt Securities		142,804		152,863
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	[1]	1,067,779		1,034,301
Available For Sale Securities Debt Securities Gross Unrealized Gain	[1]	14,081		15,431
Available For Sale Securities Debt Securities Gross Unrealized Losses	[1]	(13,030)		(12,950)
Available For Sale Securities Debt Securities Fair Value		1,068,830	[1]	1,036,782
Available-for-sale Securities, Debt Securities	[1]	1,068,830		1,036,782
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		4,350,677		4,443,383
Available For Sale Securities Debt Securities Gross Unrealized Gain		136,978		116,558
Available For Sale Securities Debt Securities Gross Unrealized Losses		(26,569)		(40,438)
Available For Sale Securities Debt Securities Fair Value		4,461,086		4,519,503
Available-for-sale Securities, Debt Securities		4,461,086		4,519,503
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		472,112		496,187
Available For Sale Securities Debt Securities Gross Unrealized Gain		16,784		20,208
Available For Sale Securities Debt Securities Gross Unrealized Losses		(2,220)		(2,593)
Available For Sale Securities Debt Securities Fair Value		486,676		513,802
Available-for-sale Securities, Debt Securities		486,676		513,802
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		2,759,063		2,791,211
Available For Sale Securities Debt Securities Gross Unrealized Gain		69,226		58,559
Available For Sale Securities Debt Securities Gross Unrealized Losses		(15,887)		(26,315)
Available For Sale Securities Debt Securities Fair Value		2,812,402		2,823,455
Available-for-sale Securities, Debt Securities		2,812,402		2,823,455
Debt, State Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		504,312		524,682
Available For Sale Securities Debt Securities Gross Unrealized Gain		18,952		16,964
Available For Sale Securities Debt Securities Gross Unrealized Losses		(3,295)		(5,139)
Available For Sale Securities Debt Securities Fair Value		519,969		536,507
Available-for-sale Securities, Debt Securities		519,969		536,507
Revenue Subject to Refund [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		349,697		356,535
Available For Sale Securities Debt Securities Gross Unrealized Gain		20,013		19,181
Available For Sale Securities Debt Securities Gross Unrealized Losses		(146)		(165)
Available For Sale Securities Debt Securities Fair Value		369,564		375,551
Available-for-sale Securities, Debt Securities		369,564		375,551
Corporation [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		376,664		410,933
Available For Sale Securities Debt Securities Gross Unrealized Gain		8,290		6,172
Available For Sale Securities Debt Securities Gross Unrealized Losses		(5,639)		(6,452)
Available For Sale Securities Debt Securities Fair Value		379,315		410,653
Available-for-sale Securities, Debt Securities		379,315		410,653
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		4,131,823		3,967,795
Available For Sale Securities Debt Securities Gross Unrealized Gain		127,263		121,650
Available For Sale Securities Debt Securities Gross Unrealized Losses		(14,290)		(20,918)
Available For Sale Securities Debt Securities Fair Value		4,244,796		4,068,527
Available-for-sale Securities, Debt Securities		4,244,796		4,068,527
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		1,212,362		1,189,841
Available For Sale Securities Debt Securities Gross Unrealized Gain		14,428		15,735
Available For Sale Securities Debt Securities Gross Unrealized Losses		(15,156)		(15,931)
Available For Sale Securities Debt Securities Fair Value		1,211,634		1,189,645
Available-for-sale Securities, Debt Securities		1,211,634		1,189,645
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		2,029,812		1,913,830
Available For Sale Securities Debt Securities Gross Unrealized Gain		7,837		5,971
Available For Sale Securities Debt Securities Gross Unrealized Losses		(9,480)		(11,941)
Available For Sale Securities Debt Securities Fair Value		2,028,169		1,907,860
Available-for-sale Securities, Debt Securities		2,028,169		1,907,860
Industrial Property [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		2,391,507		2,315,567
Available For Sale Securities Debt Securities Gross Unrealized Gain		70,783		71,007
Available For Sale Securities Debt Securities Gross Unrealized Losses		(5,330)		(7,174)
Available For Sale Securities Debt Securities Fair Value		2,456,960		2,379,400
Available-for-sale Securities, Debt Securities		2,456,960		2,379,400
Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		1,445,707		1,369,001
Available For Sale Securities Debt Securities Gross Unrealized Gain		45,431		39,543
Available For Sale Securities Debt Securities Gross Unrealized Losses		(6,881)		(11,270)
Available For Sale Securities Debt Securities Fair Value		1,484,257		1,397,274
Available-for-sale Securities, Debt Securities		1,484,257		1,397,274
Public Utility, Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		238,801		229,154
Available For Sale Securities Debt Securities Gross Unrealized Gain		10,578		10,801
Available For Sale Securities Debt Securities Gross Unrealized Losses		(2,049)		(2,411)
Available For Sale Securities Debt Securities Fair Value		247,330		237,544
Available-for-sale Securities, Debt Securities		247,330		237,544
Other Security Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		55,808		54,073
Available For Sale Securities Debt Securities Gross Unrealized Gain		471		299
Available For Sale Securities Debt Securities Gross Unrealized Losses		(30)		(63)
Available For Sale Securities Debt Securities Fair Value		56,249		54,309
Available-for-sale Securities, Debt Securities		56,249		54,309
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment		73,631		72,582
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain		13,374		12,453
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss		0		0
Held-to-maturity Securities, Fair Value		87,005		85,035
Held-to-maturity Securities		73,631		72,582
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment		15,316		15,944
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain		1,651		1,693
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss		0		0
Held-to-maturity Securities, Fair Value		16,967		17,637
Held-to-maturity Securities		$ 15,316		$ 15,944
[1]	Gross unrealized losses for residential mortgage-backed securities include $717,960 and $818,691 as of March 31, 2017 and December 31, 2016, respectively, related to the non-credit portion of other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income.

Investments in Equity Securit56

Investments in Equity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 211,440	$ 220,587
Gross Unrealized, Gains	404,192	453,298
Gross Unrealized, Losses	(4,254)	(4,685)
Carrying and fair value of equity securities	611,378	669,200
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	90,080	94,998
Gross Unrealized, Gains	333,397	351,906
Gross Unrealized, Losses	(2,148)	(1,046)
Carrying and fair value of equity securities	421,329	445,858
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	121,360	125,589
Gross Unrealized, Gains	70,795	101,392
Gross Unrealized, Losses	(2,106)	(3,639)
Carrying and fair value of equity securities	$ 190,049	$ 223,342

Arbitrage Trading Account (Deta

Arbitrage Trading Account (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Arbitrage trading account	$ 753,278	$ 299,999
Options Held [Member] | Short [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	400
Derivative, Notional Amount	40,000
Options Held [Member] | Long [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	600
Derivative, Notional Amount	14,000
Arbitrage Trading Account [Member]
Derivative [Line Items]
Arbitrage trading account	$ 753,000	$ 300,000

Net Investment Income Net Inv58

Net Investment Income Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net Investment Income [Line Items]
Investment income	$ 150,560	$ 132,246
Investment expense	(1,702)	(2,113)
Net investment income	148,858	130,133
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Investment income	112,346	108,835
Investment funds
Net Investment Income [Line Items]
Investment income	26,649	16,636
Arbitrage trading account
Net Investment Income [Line Items]
Investment income	6,360	3,190
Equity securities available for sale
Net Investment Income [Line Items]
Investment income	639	868
Real estate
Net Investment Income [Line Items]
Investment income	$ 4,566	$ 2,717

Investment Funds Investment F59

Investment Funds Investment Funds (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Investment funds	$ 1,238,558		$ 1,198,146
Income (Loss) from Investment Funds	26,649	$ 16,636
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	654,501		641,783
Income (Loss) from Investment Funds	4,532
Wholly Owned Properties [Member]
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Investment Funds		17,037
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	96,161		91,448
Income (Loss) from Investment Funds	3,245	(3,924)
Hedge equity
Schedule of Equity Method Investments [Line Items]
Investment funds	74,779		73,913
Income (Loss) from Investment Funds	866	(2,852)
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	413,117		$ 391,002
Income (Loss) from Investment Funds	$ 18,006	$ 6,375

Real Estate Real Estate (Detail

Real Estate Real Estate (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Real Estate [Abstract]
Properties in operation	$ 448,422,000	$ 457,237,000
Properties under development	789,316,000	727,744,000
Total	1,237,738,000	1,184,981,000
Real Estate Investment Property, Accumulated Depreciation	$ 16,654,000	$ 14,996,000

Real Estate Real Estate (Deta61

Real Estate Real Estate (Details 1) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Real Estate [Abstract]
Accumulated depreciation and amortization on properties	$ 16,654,000		$ 14,996,000
Real estate depreciation expense	1,648,000	$ 1,668,000
Operating Leases, Future Minimum Payments Receivable, Remainder of Fiscal Year	13,116,000
Lease future minimum payments Current	26,513,000
Operating Leases, Future Minimum Payments Receivable, in Two Years	27,839,000
Lease future minimum payments 2017	26,673,000
Future Minimum Payments 2018	26,958,000
Lease future minimum payments 2019	26,618,000
Lease future minimum payments there after	$ 449,273,000

Loans Receivable (Details)

Loans Receivable (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 5,300		$ 5,400
Loans and Leases Receivable, Gross	103,650		106,798
Loans receivable	105,153		108,299
Valuation allowance, specific	1,200		1,200
Valuation allowance, general	2,183		2,197
Valuation allowance of loans receivable	3,383		3,397
Decrease in valuation allowance	(14)	$ 568
Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	89,206		92,415
Loans receivable	89,206		92,415
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	14,444		14,383
Loans receivable	$ 15,947		$ 15,884

Realized And Unrealized Inves63

Realized And Unrealized Investment Gains Realized and Unrealized Investment Gains (Loss) (Realized and unrealized investmetns gains(losses)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Fixed maturity securities, gains	$ 5,605	$ 23,064
Fixed maturity securities, losses	(3,965)	(2,940)
Equity securities available for sale	42,707	125
Investment funds	1,267	(460)
Real Estate Realized Gain (Loss) on Disposal	3,300	5,024
Other	3,434	644
Realized Gain (Loss) on Investments, Including Equity Method Investments, Excluding Other than Temporary Impairments and Allowances	52,348	25,457
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	0	(18,114)
Gain (Loss) on Investments	52,348	7,343
Net investment gains	52,348	7,343
Income tax expense	(18,322)	(2,570)
After-tax net realized investment gains	$ 34,026	$ 4,773

Realized and Unrealized Inves64

Realized and Unrealized Investment Gains (Losses) (Change in Unrealized Gains (Losses) of Available For Sales Securities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Realized and Unrealized Investment Gains Losses [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	$ 0	$ 18,114
Change in unrealized gains (losses) before income taxes and noncontrolling interests	(9,571)	114,390
Income tax benefit (expense)	740	(37,535)
Noncontrolling interests	19	14
Total change in unrealized gains	(8,812)	76,869
Debt Securities Previously Impaired [Member]
Realized and Unrealized Investment Gains Losses [Line Items]
Change in unrealized gains (losses) before income taxes and noncontrolling interests	101	(55)
Debt Securities [Member]
Realized and Unrealized Investment Gains Losses [Line Items]
Change in unrealized gains (losses) before income taxes and noncontrolling interests	37,984	92,428
Equity securities available for sale
Realized and Unrealized Investment Gains Losses [Line Items]
Change in unrealized gains (losses) before income taxes and noncontrolling interests	(48,862)	13,137
Investment funds
Realized and Unrealized Investment Gains Losses [Line Items]
Change in unrealized gains (losses) before income taxes and noncontrolling interests	$ 1,206	8,880
Common stocks
Realized and Unrealized Investment Gains Losses [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment		$ 18,100

Securities In An Unrealized L65

Securities In An Unrealized Loss Position Securities in an Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	$ 0	$ (18,114)
Fair Value, Less than 12 Months	4,031,893		$ 4,560,889
Gross Unrealized Losses, Less than 12 Months	48,808		68,703
Fair Value, 12 Months or Greater	518,319		599,999
Gross Unrealized Losses, 12 Months or Greater	24,738		30,565
Fair Value, Total	4,550,212		5,160,888
Gross Unrealized Losses, Total	73,546		99,268
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	95,253		112,709
Gross Unrealized Losses, Less than 12 Months	954		1,252
Fair Value, 12 Months or Greater	33,071		35,450
Gross Unrealized Losses, 12 Months or Greater	1,266		1,341
Fair Value, Total	128,324		148,159
Gross Unrealized Losses, Total	2,220		2,593
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	1,111,978		1,562,614
Gross Unrealized Losses, Less than 12 Months	22,836		35,553
Fair Value, 12 Months or Greater	150,439		133,034
Gross Unrealized Losses, 12 Months or Greater	3,733		4,885
Fair Value, Total	1,262,417		1,695,648
Gross Unrealized Losses, Total	26,569		40,438
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	618,642		625,903
Gross Unrealized Losses, Less than 12 Months	10,013		11,103
Fair Value, 12 Months or Greater	140,791		109,066
Gross Unrealized Losses, 12 Months or Greater	5,143		4,828
Fair Value, Total	759,433		734,969
Gross Unrealized Losses, Total	15,156		15,931
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	1,204,310		1,010,836
Gross Unrealized Losses, Less than 12 Months	4,386		5,340
Fair Value, 12 Months or Greater	95,421		201,693
Gross Unrealized Losses, 12 Months or Greater	5,094		6,601
Fair Value, Total	1,299,731		1,212,529
Gross Unrealized Losses, Total	9,480		11,941
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	867,293		1,035,245
Gross Unrealized Losses, Less than 12 Months	8,126		13,448
Fair Value, 12 Months or Greater	61,732		65,147
Gross Unrealized Losses, 12 Months or Greater	6,164		7,470
Fair Value, Total	929,025		1,100,392
Gross Unrealized Losses, Total	14,290		20,918
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	115,542		213,246
Gross Unrealized Losses, Less than 12 Months	1,320		1,985
Fair Value, 12 Months or Greater	4,495		24,820
Gross Unrealized Losses, 12 Months or Greater	257		777
Fair Value, Total	120,037		238,066
Gross Unrealized Losses, Total	1,577		2,762
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	4,013,018		4,560,553
Gross Unrealized Losses, Less than 12 Months	47,635		68,681
Fair Value, 12 Months or Greater	485,949		569,210
Gross Unrealized Losses, 12 Months or Greater	21,657		25,902
Fair Value, Total	4,498,967		5,129,763
Gross Unrealized Losses, Total	69,292		94,583
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	0		0
Gross Unrealized Losses, Less than 12 Months	0		0
Fair Value, 12 Months or Greater	23,567		22,034
Gross Unrealized Losses, 12 Months or Greater	2,106		3,639
Fair Value, Total	23,600		22,034
Gross Unrealized Losses, Total	2,106		3,639
Equity securities available for sale
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	18,875		336
Gross Unrealized Losses, Less than 12 Months	1,173		22
Fair Value, 12 Months or Greater	32,370		30,789
Gross Unrealized Losses, 12 Months or Greater	3,081		4,663
Fair Value, Total	51,245		31,125
Gross Unrealized Losses, Total	4,254		4,685
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	18,875		336
Gross Unrealized Losses, Less than 12 Months	1,173		22
Fair Value, 12 Months or Greater	8,803		8,755
Gross Unrealized Losses, 12 Months or Greater	975		1,024
Fair Value, Total	27,678		9,091
Gross Unrealized Losses, Total	2,148		$ 1,046
Noninvestment Grade Investments at Loss Less than 5 Million [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	106,289
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	19,647
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	$ 19,990
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount		$ 18,100

Securities In An Unrealized L66

Securities In An Unrealized Loss Position Non-Investment Grade Fixed Maturity Securities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)positionshares	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 4,550,212		$ 5,160,888
Available For Sale Equity Securities Gross Unrealized Gains	404,192		453,298
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	73,546		99,268
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	4,498,967		5,129,763
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	69,292		94,583
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	0	$ 0
Aggregate fair value of securities in a continuous unrealized loss position	23,600		22,034
Available For Sale Equity Securities Gross Unrealized Gains	70,795		101,392
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	2,106		3,639
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	27,700
Aggregate fair value of securities in a continuous unrealized loss position	27,678		9,091
Available For Sale Equity Securities Gross Unrealized Gains	333,397		351,906
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	2,148		1,046
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	759,433		734,969
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	15,156		15,931
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	1,299,731		1,212,529
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	9,480		11,941
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	1,262,417		1,695,648
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	26,569		40,438
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	120,037		238,066
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	1,577		2,762
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	929,025		1,100,392
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	$ 14,290		$ 20,918
Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities | shares	1
Noninvestment Grade Investments at Loss Less than 5 Million [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	31
Aggregate fair value of securities in a continuous unrealized loss position	$ 106,289
Gross Unrealized Loss	$ 6,244
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	9
Aggregate fair value of securities in a continuous unrealized loss position	$ 19,647
Gross Unrealized Loss	$ 924
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Foreign Government Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	11
Aggregate fair value of securities in a continuous unrealized loss position	$ 51,901
Gross Unrealized Loss	$ 681
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	4
Aggregate fair value of securities in a continuous unrealized loss position	$ 19,990
Gross Unrealized Loss	741
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Equity Securities Gross Unrealized Gains	$ 2,100
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities | position	6
Aggregate fair value of securities in a continuous unrealized loss position	$ 9,615
Gross Unrealized Loss	$ 173

Securities In An Unrealized L67

Securities In An Unrealized Loss Position Securities In An Unrealized Loss Position (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)shares	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 4,550,212		$ 5,160,888
Gross Unrealized Losses	73,546		99,268
Available For Sale Equity Securities Gross Unrealized Gains	$ 404,192		453,298
Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities | shares	1
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 23,600		22,034
Gross Unrealized Losses	2,106		3,639
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	0	$ 0
Available For Sale Equity Securities Gross Unrealized Gains	70,795		101,392
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	27,678		9,091
Gross Unrealized Losses	2,148		1,046
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	27,700
Available For Sale Equity Securities Gross Unrealized Gains	333,397		$ 351,906
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Equity Securities Gross Unrealized Gains	$ 2,100

Fair Value Measurements (Assets

Fair Value Measurements (Assets and Liabilities Measured At Fair Value, On a Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	$ 13,334,032	$ 13,102,142
Loans receivable	611,378	669,200
Arbitrage trading account	753,278	299,999
Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	13,334,032	13,102,142
Loans receivable	611,378	669,200
Assets, fair value disclosure	14,698,688	14,071,341
Arbitrage trading account	753,278	299,999
Securities sold but not yet purchased	51,348	51,179
Fair Value, Measurements, Recurring [Member] | U.S. government and government agency
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	486,676	513,802
Fair Value, Measurements, Recurring [Member] | State and municipal
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	4,461,086	4,519,503
Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	1,211,634	1,189,645
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	2,028,169	1,907,860
Fair Value, Measurements, Recurring [Member] | Corporate
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	4,244,796	4,068,527
Fair Value, Measurements, Recurring [Member] | Foreign government
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	901,671	902,805
Fair Value, Measurements, Recurring [Member] | Common stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	421,329	445,858
Fair Value, Measurements, Recurring [Member] | Preferred stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	190,049	223,342
Level 1 | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Loans receivable	403,855	429,647
Assets, fair value disclosure	660,607	654,270
Arbitrage trading account	256,752	224,623
Securities sold but not yet purchased	51,348	51,089
Level 1 | Fair Value, Measurements, Recurring [Member] | U.S. government and government agency
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 1 | Fair Value, Measurements, Recurring [Member] | State and municipal
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 1 | Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 1 | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 1 | Fair Value, Measurements, Recurring [Member] | Corporate
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 1 | Fair Value, Measurements, Recurring [Member] | Foreign government
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 1 | Fair Value, Measurements, Recurring [Member] | Common stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	403,855	429,647
Level 1 | Fair Value, Measurements, Recurring [Member] | Preferred stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	0	0
Level 2 | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	13,333,853	13,101,959
Loans receivable	195,058	227,137
Assets, fair value disclosure	14,025,376	13,404,472
Arbitrage trading account	496,465	75,376
Securities sold but not yet purchased	0	90
Level 2 | Fair Value, Measurements, Recurring [Member] | U.S. government and government agency
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	486,676	513,802
Level 2 | Fair Value, Measurements, Recurring [Member] | State and municipal
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	4,461,086	4,519,503
Level 2 | Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	1,211,634	1,189,645
Level 2 | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	2,027,990	1,907,677
Level 2 | Fair Value, Measurements, Recurring [Member] | Corporate
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	4,244,796	4,068,527
Level 2 | Fair Value, Measurements, Recurring [Member] | Foreign government
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	901,671	902,805
Level 2 | Fair Value, Measurements, Recurring [Member] | Common stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	8,671	7,457
Level 2 | Fair Value, Measurements, Recurring [Member] | Preferred stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	186,387	219,680
Level 3 | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	179	183
Loans receivable	12,465	12,416
Assets, fair value disclosure	12,705	12,599
Arbitrage trading account	61	0
Securities sold but not yet purchased	0	0
Level 3 | Fair Value, Measurements, Recurring [Member] | U.S. government and government agency
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 3 | Fair Value, Measurements, Recurring [Member] | State and municipal
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 3 | Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 3 | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	179	183
Level 3 | Fair Value, Measurements, Recurring [Member] | Corporate
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 3 | Fair Value, Measurements, Recurring [Member] | Foreign government
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	0	0
Level 3 | Fair Value, Measurements, Recurring [Member] | Common stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	8,803	8,754
Level 3 | Fair Value, Measurements, Recurring [Member] | Preferred stocks
Fair Value Measurements, Recurring and Nonrecurring Basis [Line Items]
Loans receivable	$ 3,662	$ 3,662

Fair Value Measurements Fair 69

Fair Value Measurements Fair Value Measurements (Summarize Changes in Level 3 Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0	0
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	$ 12,599	$ 11,982
Assets, earnings	1	42
Assets, other comprehensive income	120	176
Assets, purchases	0	765
Assets, (sales)	(15)	(331)
Assets, maturities		35
Assets, ending balance	12,705	12,599
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
Level 3 | Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	183	199
Assets, earnings	1	3
Assets, other comprehensive income	10	16
Assets, purchases	0	0
Assets, (sales)	15	0
Assets, maturities	0	(35)
Assets, ending balance	179	183
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Impairment of Intangible Assets (Excluding Goodwill)	0	0
Level 3 | Equity securities available for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	12,416	11,453
Assets, earnings	0	38
Assets, other comprehensive income	49	160
Assets, purchases	0	765
Assets, (sales)	0	0
Assets, ending balance	12,465	12,416
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Level 3 | Preferred stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	3,662	3,624
Assets, earnings	0	38
Assets, other comprehensive income	$ 0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0	0
Assets, purchases	$ 0	$ 0
Assets, (sales)	0	0
Assets, ending balance	3,662	3,662
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
Level 3 | Common stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	8,754	7,829
Assets, earnings	0	0
Assets, other comprehensive income	$ 49	$ 160
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0	0
Assets, purchases	$ 0	$ 765
Assets, (sales)	0	0
Assets, ending balance	8,803	8,754
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Level 3 | Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	183	353
Assets, earnings	1	180
Assets, other comprehensive income	$ 10	$ 16
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0	0
Assets, purchases	$ 0	$ 0
Assets, (sales)	(15)	(331)
Assets, maturities		35
Assets, ending balance	179	183
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Level 3 | Corporate Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	0	154
Assets, earnings	0	177
Assets, other comprehensive income	$ 0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0	0
Assets, purchases	$ 0	$ 0
Assets, (sales)	0	(331)
Assets, ending balance	0	0
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Level 3 | Trading Assets, Excluding Debt and Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	0	176
Assets, earnings	0	(176)
Assets, other comprehensive income	$ 61	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0	0
Assets, purchases	$ 0	$ 0
Assets, (sales)	0	0
Assets, ending balance	61	0
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	$ 0

Reinsurance Reinsurance (Detail

Reinsurance Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Premiums Written
Written premiums, direct	$ 1,721,062	$ 1,709,129
Written premiums, assumed	215,145	246,568
Written premiums, ceded	(289,369)	(291,975)
Total net premiums written	1,646,838	1,663,722
Premiums Earned
Earned premiums, direct	1,613,364	1,568,067
Earned premiums, assumed	208,626	218,367
Earned premiums, ceded	(251,948)	(259,099)
Net premiums earned	1,570,042	1,527,335
Ceded losses and loss expenses incurred	35,192	126,929
Uncollectible reinsurance	1,000		$ 1,000
Fees and Commissions, Other	$ 56,550	$ 47,973

Fair Value of Financial Instr71

Fair Value of Financial Instruments (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets:
Equity securities available for sale	$ 753,278	$ 299,999
Loans receivable	105,153	108,299
Carrying Value
Assets:
Fixed maturity securities	13,422,979	13,190,668
Equity securities available for sale	611,378	669,200
Equity securities available for sale	753,278	299,999
Loans receivable	103,650	106,798
Cash and cash equivalents	608,393	795,285
Trading account receivables from brokers and clearing organizations	29,131	484,593
Due From Brokers, Fair Value Disclosure	3,749	0
Due from broker fair value	0	19,416
Liabilities:
Trading account securities sold but not yet purchased	51,348	51,179
Subordinated debentures	727,777	727,630
Senior notes and other debt	1,759,494	1,760,595
Fair Value
Assets:
Fixed maturity securities	13,438,004	13,204,814
Equity securities available for sale	611,378	669,200
Equity securities available for sale	753,278	299,999
Loans receivable	105,153	108,299
Cash and cash equivalents	608,393	795,285
Trading account receivables from brokers and clearing organizations	29,131	484,593
Due From Brokers, Fair Value Disclosure	3,749	0
Due from broker fair value	0	19,416
Liabilities:
Trading account securities sold but not yet purchased	51,348	51,179
Subordinated debentures	750,104	687,504
Senior notes and other debt	$ 1,927,392	$ 1,914,727

Restricted Stock Units (Summary

Restricted Stock Units (Summary of Restricted Stock Units Issued) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]
Share based compensation expense	$ 11,000	$ 9,000
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]
Restricted Stock Units	1,853	5,580,000
Restricted Stock Units, Fair Value	$ 129	$ 286
Minimum [Member] | Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]
Award vesting period	3 years
Maximum [Member] | Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]
Award vesting period	5 years

Industry Segments (Financial In

Industry Segments (Financial Information of Company Operating Segments) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Earned Premiums		$ 1,570,042	$ 1,527,335
Investment Income and Funds		148,858	130,133
Other Revenues		151,518	149,743
Total revenues		1,870,418	1,807,211
Pre-Tax Income (Loss)		184,297	174,676
Net Income (Loss)		123,447	119,511
Net investment gains		52,348	7,343
Net investment gains, net of tax		34,026	4,773
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	[1]	0	0
Investment Income and Funds	[1]	12,171	6,503
Other Revenues	[1]	80,883	115,607
Total revenues	[1]	93,054	122,110
Pre-Tax Income (Loss)	[1]	(72,639)	(60,379)
Net Income (Loss)	[1]	(47,773)	(39,649)
Insurance-Domestic Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums		1,413,170	1,366,605
Insurance-Domestic Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums		1,413,170	1,366,605
Investment Income and Funds		111,909	99,860
Other Revenues		18,287	26,793
Total revenues		1,543,366	1,493,258
Pre-Tax Income (Loss)		199,994	199,651
Net Income (Loss)		134,095	134,778
Reinsurance-Global Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums		156,872	160,730
Reinsurance-Global Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums		156,872	160,730
Investment Income and Funds		24,778	23,770
Other Revenues		0	0
Total revenues		181,650	184,500
Pre-Tax Income (Loss)		4,594	28,061
Net Income (Loss)		3,099	19,609
Net Investment Gains Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums		0	0
Investment Income and Funds		$ 0	$ 0
[1]	Corporate, other and eliminations represent corporate revenues and expenses that are not allocated to business segments.

Industry Segments (Identifiable

Industry Segments (Identifiable Assets by Segment) (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets		$ 23,547,414	$ 23,350,076
Operating Segments [Member] | Reinsurance-Global Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets		2,750,876	2,524,338
Operating Segments [Member] | Insurance-Domestic Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets		18,932,563	19,137,758
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	[1]	$ 1,863,975	$ 1,687,980
[1]	Corporate, other and eliminations represent corporate revenues and expenses that are not allocated to business segments.

Industry Segments Industry Segm

Industry Segments Industry Segments (Net Premiums Earned By Major Line of Business) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenue from External Customer [Line Items]
Premiums Earned, Net	$ 1,570,042	$ 1,527,335
Insurance-Domestic Segment [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	1,413,170	1,366,605
Insurance-Domestic Segment [Member] | Other Insurance Liabilities [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	451,830	413,528
Insurance-Domestic Segment [Member] | Workers' Compensation [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	361,136	343,581
Insurance-Domestic Segment [Member] | Property [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	309,234	327,076
Insurance-Domestic Segment [Member] | Commercial Automobile [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	158,126	156,817
Insurance-Domestic Segment [Member] | Products Liability [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	132,844	125,603
Reinsurance-Global Segment [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	156,872	160,730
Reinsurance-Global Segment [Member] | Property [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	62,133	56,425
Reinsurance-Global Segment [Member] | Casualty [Member]
Revenue from External Customer [Line Items]
Premiums Earned, Net	$ 94,739	$ 104,305