MGIC Investment (MTG) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	MGIC INVESTMENT CORP
Entity Central Index Key	876,437
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		370,566,801
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities, available-for-sale, at fair value:
Fixed income (amortized cost, 2017 - $4,666,165; 2016 - $4,717,211)	$ 4,710,153	$ 4,685,222
Equity securities	7,239	7,128
Total investment portfolio	4,717,392	4,692,350
Cash and cash equivalents	250,701	155,410
Accrued investment income	42,928	44,073
Reinsurance recoverable on loss reserves	45,878	50,493
Reinsurance recoverable on paid losses	4,638	4,964
Premiums receivable	53,938	52,392
Home office and equipment, net	43,157	36,088
Deferred insurance policy acquisition costs	19,024	17,759
Deferred income taxes, net	416,167	607,655
Other assets	82,045	73,345
Total assets	5,675,868	5,734,529
Liabilities:
Loss reserves	1,105,151	1,438,813
Unearned premiums	370,816	329,737
Federal Home Loan Bank advance	155,000	155,000
Senior notes	418,271	417,406
Convertible senior notes	0	349,461
Convertible junior subordinated debentures	256,872	256,872
Other liabilities	239,609	238,398
Total liabilities	2,545,719	3,185,687
Contingencies
Shareholders’ equity:
Common stock (one dollar par value, shares authorized 1,000,000; shares issued 2017 - 370,562; 2016 - 359,400; shares outstanding 2017 - 370,562; 2016 - 340,663)	370,562	359,400
Paid-in capital	1,846,260	1,782,337
Treasury stock at cost (shares 2016 - 18,737)	0	(150,359)
Accumulated other comprehensive loss, net of tax	(26,097)	(75,100)
Retained earnings	939,424	632,564
Total shareholders’ equity	3,130,149	2,548,842
Total liabilities and shareholders’ equity	$ 5,675,868	$ 5,734,529

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 4,666,165	$ 4,717,211
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	370,562,000	359,400,000
Common stock, shares outstanding (in shares)	370,562,000	340,663,000
Treasury stock, shares at cost (in shares)	0	18,737,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Premiums written:
Direct	$ 287,918,000	$ 283,618,000	$ 828,986,000	$ 831,022,000
Assumed	(91,000)	152,000	1,882,000	542,000
Ceded	(31,931,000)	(33,446,000)	(92,436,000)	(99,944,000)
Net premiums written	255,896,000	250,324,000	738,432,000	731,620,000
Increase in unearned premiums, net	(18,813,000)	(12,948,000)	(41,110,000)	(41,447,000)
Net premiums earned	237,083,000	237,376,000	697,322,000	690,173,000
Investment income, net of expenses	30,402,000	27,515,000	89,595,000	82,572,000
Net realized investment (losses) gains	(47,000)	5,092,000	(211,000)	8,984,000
Other revenue	2,922,000	3,867,000	7,846,000	14,234,000
Total revenues	270,360,000	273,850,000	794,552,000	795,963,000
Losses and expenses:
Losses incurred, net	29,747,000	60,897,000	84,705,000	192,499,000
Amortization of deferred policy acquisition costs	2,985,000	2,575,000	7,799,000	6,781,000
Other underwriting and operating expenses, net	39,888,000	37,870,000	119,164,000	112,995,000
Interest expense	13,273,000	13,536,000	43,779,000	40,481,000
Loss on debt extinguishment	0	75,223,000	65,000	90,531,000
Total losses and expenses	85,893,000	190,101,000	255,512,000	443,287,000
Income before tax	184,467,000	83,749,000	539,040,000	352,676,000
Provision for income taxes	64,440,000	27,131,000	210,593,000	117,646,000
Net income	$ 120,027,000	$ 56,618,000	$ 328,447,000	$ 235,030,000
Earnings per share:
Basic (in dollars per share)	$ 0.32	$ 0.16	$ 0.91	$ 0.68
Diluted (in dollars per share)	$ 0.32	$ 0.14	$ 0.86	$ 0.58
Weighted average common shares outstanding - basic (in shares)	370,586	349,376	359,613	343,403
Weighted average common shares outstanding - diluted (in shares)	391,087	406,050	395,870	421,423

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 120,027	$ 56,618	$ 328,447	$ 235,030
Other comprehensive income (loss), net of tax:
Change in unrealized investment gains and losses	11,544	(14,434)	49,414	92,731
Benefit plan adjustments	(147)	(241)	(442)	(722)
Foreign currency translation adjustment	0	(10)	31	(974)
Other comprehensive income (loss), net of tax	11,397	(14,685)	49,003	91,035
Comprehensive income	$ 131,424	$ 41,933	$ 377,450	$ 326,065

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Paid-in capital	Treasury stock	Accumulated other comprehensive (loss) income	Retained earnings
Balance, beginning of period at Dec. 31, 2015		$ 340,097	$ 1,670,238	$ (3,362)	$ (60,880)	$ 290,047
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net common stock issued under share-based compensation plans		985	(5,989)
Issuance of common stock		18,313	113,146
Tax benefit from share-based compensation			100
Equity compensation			8,753
Reacquisition of convertible junior subordinated debentures-equity component			(6,337)
Purchases of common stock	$ (108,100)			(108,097)
Reissuance of treasury stock, net				0		0
Other comprehensive income, net of tax	91,035				91,035
Net income	235,030					235,030
Balance, end of period at Sep. 30, 2016	2,583,079	359,395	1,779,911	(111,459)	30,155	525,077
Balance, beginning of period at Dec. 31, 2016	2,548,842	359,400	1,782,337	(150,359)	(75,100)	632,717
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net common stock issued under share-based compensation plans		776	(7,558)
Issuance of common stock		10,386	60,903
Tax benefit from share-based compensation			0
Equity compensation			10,578
Reacquisition of convertible junior subordinated debentures-equity component			0
Purchases of common stock				0
Reissuance of treasury stock, net				150,359		(21,740)
Other comprehensive income, net of tax	49,003				49,003
Net income	328,447					328,447
Balance, end of period at Sep. 30, 2017	$ 3,130,149	$ 370,562	$ 1,846,260	$ 0	$ (26,097)	$ 939,424

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 328,447,000	$ 235,030,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	48,882,000	44,324,000
Deferred tax expense	165,250,000	111,191,000
Net realized investment losses (gains)	211,000	(8,984,000)
Loss on debt extinguishment	65,000	90,531,000
Change in certain assets and liabilities:
Accrued investment income	1,145,000	(2,086,000)
Reinsurance recoverable on loss reserves	4,615,000	(2,376,000)
Reinsurance recoverable on paid losses	326,000	(1,313,000)
Premium receivable	(1,546,000)	1,048,000
Deferred insurance policy acquisition costs	(1,265,000)	(2,167,000)
Profit commission receivable	(3,899,000)	(2,005,000)
Loss reserves	(333,662,000)	(357,919,000)
Unearned premiums	41,079,000	41,353,000
Return premium accrual	(18,000,000)	(12,800,000)
Income taxes payable - current	33,943,000	822,000
Other, net	(9,235,000)	14,337,000
Net cash provided by operating activities	256,356,000	148,986,000
Purchases of investments:
Fixed income securities	(774,985,000)	(1,105,995,000)
Equity securities	(58,000)	(4,315,000)
Proceeds from sales of fixed income securities	233,198,000	718,894,000
Proceeds from maturity of fixed income securities	547,699,000	432,557,000
Proceeds from sale of equity securities	0	6,425,000
Net increase in payable for securities	3,738,000	3,376,000
Additions to property and equipment	(12,121,000)	(4,969,000)
Net cash (used in) provided by investing activities	(2,529,000)	45,973,000
Cash flows from financing activities:
Proceeds from revolving credit facility	150,000,000	0
Repayment of revolving credit facility	(150,000,000)	0
Proceeds from issuance of long-term debt	0	573,094,000
Purchase or repayment of convertible senior notes	(145,620,000)	(363,778,000)
Payment of original issue discount - convertible senior notes	(4,504,000)	(11,250,000)
Purchase of convertible junior subordinated debentures	0	(100,860,000)
Payment of original issue discount - convertible junior subordinated debentures	0	(41,540,000)
Repurchase of common stock	0	(91,597,000)
Cash portion of loss on debt extinguishment	0	(59,460,000)
Payment of debt issuance costs	(1,630,000)	(938,000)
Payment of withholding taxes related to share-based compensation net share settlement	(6,782,000)	(5,007,000)
Net cash used in financing activities	(158,536,000)	(101,336,000)
Net increase in cash and cash equivalents	95,291,000	93,623,000
Cash and cash equivalents at beginning of period	155,410,000	181,120,000
Cash and cash equivalents at end of period	$ 250,701,000	$ 274,743,000

Nature of Business and Basis of

Nature of Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	Nature of Business and Basis of Presentation MGIC Investment Corporation is a holding company which, through Mortgage Guaranty Insurance Corporation (“MGIC”) is principally engaged in the mortgage insurance business. We provide mortgage insurance to lenders throughout the United States and to government sponsored entities (“GSEs”) to protect against loss from defaults on low down payment residential mortgage loans. The accompanying unaudited consolidated financial statements of MGIC Investment Corporation and its wholly-owned subsidiaries have been prepared in accordance with the instructions to Form 10-Q as prescribed by the Securities and Exchange Commission (“SEC”) for interim reporting and do not include all of the other information and disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). These statements should be read in conjunction with the consolidated financial statements and notes thereto for the year ended December 31, 2016 included in our Annual Report on Form 10-K. As used below, “we,” “our” and “us” refer to MGIC Investment Corporation’s consolidated operations or to MGIC Investment Corporation, as the context requires. In the opinion of management the accompanying financial statements include all adjustments, consisting primarily of normal recurring accruals, necessary to fairly state our consolidated financial position and consolidated results of operations for the periods indicated. The consolidated results of operations for the interim period may not be indicative of the results that may be expected for the year ending December 31, 2017 . Substantially all of our insurance written since 2008 has been for loans purchased by the GSEs. We operate under the Private Mortgage Insurer Eligibility Requirements ("PMIERs") of the GSEs that became effective December 31, 2015 and have been amended from time to time. The financial requirements of the PMIERs require a mortgage insurer’s "Available Assets" (generally only the most liquid assets of an insurer) to equal or exceed its "Minimum Required Assets" (which are based on an insurer's book and are calculated from tables of factors with several risk dimensions and are subject to a floor amount). Based on our interpretation of the PMIERs, as of September 30, 2017 , MGIC’s Available Assets are in excess of its Minimum Required Assets; and MGIC is in compliance with the financial requirements of the PMIERs and eligible to insure loans purchased by the GSEs. Reclassifications Certain reclassifications to 2016 amounts have been made in the accompanying financial statements to conform to the 2017 presentation. Subsequent events We have considered subsequent events through the date of this filing. See Note 12 - “Loss Reserves” for a discussion of the impact recent hurricane activity is having on our notice of default inventory.

New Accounting Pronouncements

New Accounting Pronouncements	9 Months Ended
	Sep. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements Adopted Accounting Standards Improvements to Employee Share-Based Compensation Accounting In March 2016, the Financial Accounting Standards Board (“FASB”) issued updated guidance that simplifies several aspects of the accounting for employee share-based compensation including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification of related amounts within the statement of cash flows. The updated guidance requires that, prospectively, all tax effects related to share-based compensation be made through the statement of operations at the time of settlement. In contrast, the previous guidance required excess tax benefits to be recognized in paid-in capital. The updated guidance also removes the requirement to delay recognition of a tax benefit until it reduces current taxes payable. This change is required to be applied on a modified retrospective basis, with a cumulative effect adjustment to opening retained earnings. Additionally, all tax related cash flows resulting from share-based compensation are to be reported as operating activities on the statement of cash flows, a change from the existing requirement to present tax benefits as an inflow from financing activities and an outflow from operating activities. Finally, for tax withholding purposes, entities will be allowed to withhold an amount of shares up to the employee’s maximum individual tax rate (as opposed to the minimum statutory tax rate) in the relevant jurisdiction without resulting in liability classification of the award. The change in tax withholding is to be applied on a modified retrospective approach. This updated guidance became effective January 1, 2017. We adopted this guidance in the first quarter of 2017 and because of the adoption: • We recognized discrete tax benefits of $1.5 million in the provision for income taxes on our statement of operations for the nine months ended September 30, 2017 related to excess tax benefits upon vesting of share-based awards during the period. • We recognized a cumulative effect adjustment in opening retained earnings as of January 1, 2017 related to the recognition of a deferred tax asset related to suspended tax benefits from vesting transactions occurring in prior years and from the elimination of our forfeiture estimate on share-based awards, which was previously applied only to awards with service conditions. • We reclassified excess tax benefits related to share-based compensation for 2016 to operating activities from financing activities. • We reclassified employee taxes paid for withheld shares for 2016 to financing activities from operating activities. Prospective Accounting Standards Stock Compensation - Scope of Modification Accounting In May 2017, the FASB issued updated guidance related to a change in the terms or conditions (modification) of a share-based award. The updated guidance provides that an entity should account for the effects of a modification unless the fair value and vesting conditions of the modified award and the classification of the award (equity or liability instrument) are the same as the original award immediately before the modification. The updated guidance addresses the current diversity in practice on applying modification accounting, as some entities evaluate whether changes to awards are substantive, which is not prescribed within the current accounting guidance. The updated guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. Early adoption is permitted, including adoption in any interim period. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. Premium Amortization on Purchased Callable Debt Securities In March 2017, the FASB issued updated guidance to amend the amortization period for certain purchased callable debt securities held at a premium shortening the amortization period to the earliest call date. Under current GAAP, there is diversity in practice in the amortization period for premiums of callable debt securities and in how the potential for exercise of a call is factored into current impairment assessments. This updated guidance aligns with how callable debt securities, in the United States, are generally quoted, priced, and traded assuming a model that incorporates consideration of calls (also referred to as “yield-to-worst” pricing). The updated guidance is effective for annual periods beginning after December 15, 2018, including interim periods within those annual periods. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. We currently account for premium amortization on our purchased callable debt securities on a yield-to-worst basis, which generally aligns with the earliest call date. Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost In March 2017, the FASB issued updated guidance that improves the reporting of net benefit cost in the financial statements. The updated guidance requires that an employer report the service cost component in the same financial statement caption as other compensation costs arising from services rendered by employees during the period. The other components of net benefit cost are required to be presented in the statement of operations separately from the service cost component and outside a subtotal of income from operations, if one is presented. Current guidance does not prescribe where the amount of net benefit cost should be presented in an employer’s statement of operations and does not require entities to disclose by line item the amount of net benefit cost that is included in the statement of operations. The updated guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued updated guidance that requires immediate recognition of estimated credit losses expected to occur over the remaining life of many financial instruments. Entities will be required to utilize a current expected credit losses (“CECL”) methodology that incorporates their forecasts of future economic conditions into their loss estimate unless such forecast is not reasonable and supportable, in which case the entity will revert to historical loss experience. Any allowance for CECL reduces the amortized cost basis of the financial instrument to the amount an entity expects to collect. Credit losses relating to available-for-sale fixed maturity securities are to be recorded through an allowance for credit losses, rather than a write-down of the asset, with the amount of the allowance limited to the amount by which fair value is less than amortized cost. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists. The updated guidance is not prescriptive about certain aspects of estimating expected credit losses, including the specific methodology to use, and therefore will require significant judgment in application. The updated guidance is effective for annual periods beginning after December 15, 2019, including interim periods within those annual periods. Early adoption is permitted for annual and interim periods in fiscal years beginning after December 15, 2018. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued updated guidance to address the recognition, measurement, presentation, and disclosure of certain financial instruments. The updated guidance requires equity investments, except those accounted for under the equity method of accounting, that have a readily determinable fair value to be measured at fair value with changes in fair value recognized in net income. Equity investments that do not have readily determinable fair values may be remeasured at fair value either upon the occurrence of an observable price change or upon identification of an impairment. A qualitative assessment for impairment is required for equity investments without readily determinable fair values. The updated guidance also eliminates the requirement to disclose the method and significant assumptions used to estimate the fair value of financial instruments measured at amortized cost on the balance sheet. Further, the updated guidance clarifies that entities should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entities other deferred tax assets. The updated guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods and will require recognition of a cumulative effect adjustment at adoption. We do not currently expect the adoption of this guidance to impact our consolidated financial statements or disclosures.

Debt

Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt	Debt 2017 debt transactions 2% Notes On March 21, 2017, we issued an irrevocable notice of redemption in respect of our outstanding 2% Convertible Senior Notes due on April 1, 2020 (“2% Notes”), with a redemption date of April 21, 2017. In April, holders of approximately $202.5 million of the outstanding principal exercised their rights to convert their notes into shares of our common stock. The remaining $5.1 million of outstanding principal was redeemed for cash. The conversions of the 2% Notes at a rate of 143.8332 shares per $1,000 principal amount resulted in the issuance of approximately 29.1 million shares of our common stock in April. The conversions and cash redemption eliminated our debt obligation. A loss on debt extinguishment of $0.07 million was recognized on the redemption of the $5.1 million of 2% Notes. No gain or loss was recognized from the conversions as the outstanding debt issuance costs associated with the conversions were included in the carrying value of the notes, which was credited to shareholders’ equity at the time of conversion. Credit Facility On March 21, 2017, we entered into a Credit Agreement with various lenders which provides for a $175 million unsecured revolving credit facility maturing on March 21, 2020. Revolving credit borrowings bear interest at a floating rate, which will be, at our option, either a eurocurrency rate or a base rate, in each case plus an applicable margin. The applicable margins are subject to adjustment based on our senior unsecured long-term debt rating, or if we do not have such a rating, our corporate or issuer rating. Amounts under the facility may be borrowed, repaid and reborrowed from time to time until the maturity of the revolving credit facility. Voluntary prepayments and commitment reductions are permitted at any time without fee subject to a minimum dollar requirement and, for outstanding eurocurrency loans, customary breakage costs. We are required under the Credit Agreement to pay commitment fees on the average daily amount of the unused revolving commitments of the lenders, and an annual administrative fee to the administrative agent. The Credit Agreement contains affirmative, negative and financial covenants which are customary for financings of this type, including, among other things, limits on the creation of liens, limits on the incurrence of indebtedness, restrictions on dispositions, maximum debt-to-capital ratio, minimum consolidated stockholders' equity, minimum policyholder's position of MGIC, and compliance with the financial requirements of the PMIERs. The Credit Agreement includes customary events of default for facilities of this type (with customary grace periods, as applicable) and provides that, upon the occurrence of an event of default, payments of all outstanding loans may be accelerated and/or the lenders' commitments may be terminated. Upon the occurrence of certain insolvency or bankruptcy related events of default, all amounts payable under the Credit Agreement shall automatically become immediately due and payable, and the lenders' commitments will automatically terminate. In addition, upon the occurrence of certain insolvency or bankruptcy related events of default, or the failure to pay interest, principal or fees, the interest rates on all outstanding obligations will be increased. In March, we borrowed $150 million under the revolving credit facility, to fund a portion of the redemption price of the 2% Notes if holders did not elect to convert their 2% Notes. In April, we repaid the amount borrowed under the revolving credit facility because most holders elected to convert their notes. Costs incurred to enter into the Credit Agreement have been deferred and recorded as Other assets and will be amortized over the term of the Credit Agreement. 5% Notes On May 1, 2017, our 5% Notes due in 2017 (“ 5% Notes”) matured and we repaid the outstanding $145 million in aggregate par value, plus accrued interest with cash at our holding company. First nine months 2016 debt transactions 5.75% Notes In August 2016, we issued $425 million aggregate principal amount of 5.75% Senior Notes due in 2023 (“5.75% Notes”) and received net proceeds, after the deduction of underwriting fees, of $418.1 million . Interest on the 5.75% Notes is payable semi-annually on February 15 and August 15 of each year, commencing on February 15, 2017. In addition to underwriting fees, we incurred approximately $1.2 million of other expenses associated with the issuance of these notes. The net proceeds from the 5.75% Notes issuance were primarily used (i) as cash consideration to purchase a portion of our 2% Notes, and (ii) to repurchase the shares issued as partial consideration in the purchases of our 2% Notes, as further described below. The remaining proceeds were held for general corporate purposes. 2% Notes In the third quarter of 2016, we entered into privately negotiated agreements to purchase $292.4 million in par value of our outstanding 2% Notes at a purchase price of $362.1 million , plus accrued interest. We funded the purchases with $230.7 million in cash proceeds from the issuance of the 5.75% Notes and by issuing to certain sellers approximately 18.3 million shares of our common stock. The excess of the purchase price over carrying value is reflected as a loss on debt extinguishment on our consolidated statements of operations for the three and nine months ended September 30, 2016. The purchases of the 2% Notes reduced our potentially dilutive shares by approximately 42.1 million shares, without considering the shares issued in partial consideration in the purchase of the 2% Notes or the repurchase of shares to offset such shares issued. For more information about the share repurchases, see Note 13 - “Shareholders’ Equity.” 5% Notes During the first nine months of 2016, we purchased $188.5 million in aggregate par value of our 5% Notes at an aggregate purchase price of $195.5 million for which we recognized losses on debt extinguishment on our consolidated statement of operations for the nine months ended September 30, 2016. The purchases of the 5% Notes reduced our potentially dilutive shares by approximately 14 million shares. 9% Debentures In February 2016, MGIC purchased $132.7 million in aggregate par value of our 9% Convertible Junior Subordinated Debentures (9% Debentures”) at a purchase price of $150.7 million . The purchase of the 9% Debentures resulted in an $8.3 million loss on debt extinguishment on the consolidated statement of operations for the nine months ended September 30, 2016, which represents the difference between the fair value and the carrying value of the liability component on the purchase date. Our shareholders’ equity was separately reduced by $6.3 million related to the reacquisition of the equity component. For GAAP accounting purposes, the 9% Debentures owned by MGIC are considered retired and are eliminated in our consolidated financial statements and the underlying common stock equivalents, approximately 9.8 million shares, are not included in the computation of diluted shares. Debt obligations The par value of our long-term debt obligations and their aggregate carrying values as of September 30, 2017 and December 31, 2016 were as follows. (In millions) September 30, December 31, FHLB Advance $ 155.0 $ 155.0 5% Notes — 145.0 2% Notes — 207.6 5.75% Notes 425.0 425.0 9% Debentures (1) 256.9 256.9 Long-term debt, par value 836.9 1,189.5 Debt issuance costs (6.8 ) (10.8 ) Long-term debt, carrying value $ 830.1 $ 1,178.7 (1) Convertible at any time prior to maturity at the holder’s option, at an initial conversion rate, which is subject to adjustment, of 74.0741 shares per $1,000 principal amount, representing an initial conversion price of approximately $13.50 per share. If a holder elects to convert their debentures, deferred interest owed on the debentures being converted is also converted into shares of our common stock. The conversion rate for any deferred interest is based on the average price that our shares traded at during a 5 -day period immediately prior to the election to convert. In lieu of issuing shares of common stock upon conversion of the debentures, we may, at our option, make a cash payment to converting holders for all or some of the shares of our common stock otherwise issuable upon conversion. The 5.75% Notes and 9% Debentures are obligations of our holding company, MGIC Investment Corporation, and not of its subsidiaries. The Federal Home Loan Bank Advance (the “FHLB Advance”) is an obligation of MGIC. Interest payments on our debt obligations appear below. Nine Months Ended September 30, (In millions) 2017 2016 Revolving credit facility $ 0.5 $ — FHLB Advance 2.2 1.7 5% Notes 3.6 6.9 2% Notes 2.1 7.0 5.75% Notes 25.1 — 9% Debentures 11.6 15.9 Total interest payments $ 45.1 $ 31.5

Reinsurance

Reinsurance	9 Months Ended
	Sep. 30, 2017
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance The reinsurance agreements we have entered into are discussed below. The effect of all of our reinsurance agreements on premiums earned and losses incurred is as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Premiums earned: Direct $ 268,709 $ 270,718 $ 789,317 $ 789,671 Assumed 312 152 472 542 Ceded (31,938 ) (33,494 ) (92,467 ) (100,040 ) Net premiums earned $ 237,083 $ 237,376 $ 697,322 $ 690,173 Losses incurred: Direct $ 35,313 $ 69,579 $ 99,122 $ 216,874 Assumed (97 ) 241 69 681 Ceded (5,469 ) (8,923 ) (14,486 ) (25,056 ) Losses incurred, net $ 29,747 $ 60,897 $ 84,705 $ 192,499 Quota share reinsurance We utilize quota share reinsurance to manage our exposure to losses resulting from our mortgage guaranty insurance policies and to provide reinsurance capital credit under the PMIERs. Our 2017 quota share reinsurance agreement (“2017 QSR Transaction”) provides coverage on new business written January 1, 2017 through December 29, 2017 that meets certain eligibility requirements. Under the agreement we cede losses incurred and premiums on or after the effective date through December 31, 2028, at which time the agreement expires. Early termination of the agreement can be elected by us effective December 31, 2021 for a fee, or under specified scenarios for no fee upon prior written notice including if we will receive less than 90% of the full credit amount under the PMIERs for the risk ceded in any required calculation period. Our 2015 quota share reinsurance agreement (“2015 QSR Transaction”) covers eligible risk in force written before 2017. The 2015 QSR Transaction cedes losses incurred and premiums through December 31, 2024, at which time the agreement expires. Early termination of the agreement can be elected by us effective December 31, 2018 for a fee, or under specified scenarios for no fee upon prior written notice, including if we will receive less than 90% of the full credit amount under the PMIERs for the risk ceded in any required calculation period. Each of the reinsurers under our 2015 and 2017 QSR Transactions has an insurer financial strength rating of A- or better by Standard and Poor’s Rating Services, A.M. Best or both. The structure of both the 2017 QSR Transaction and 2015 QSR Transaction is a 30% quota share for all policies covered, with a 20% ceding commission as well as a profit commission. Generally, under the QSR Transactions, we will receive a profit commission provided that the loss ratio on the loans covered under the agreement remains below 60% . Following is a summary of our quota share reinsurance agreements, excluding captive agreements discussed below, for the three and nine months ended September 30, 2017 and 2016 . Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Ceded premiums written and earned, net of profit commission (1) $ 30,880 $ 31,707 $ 88,692 $ 93,334 Ceded losses incurred 5,879 7,432 14,990 22,015 Ceding commissions (2) 12,500 12,137 36,751 35,659 Profit commission 31,621 28,981 95,063 84,963 (1) Under our QSR Transactions, premiums are ceded on an earned and received basis as defined in the agreements. (2) Ceding commissions are reported within Other underwriting and operating expenses, net on the consolidated statements of operations. Under the terms of QSR Transactions, ceded premiums, ceding commission and profit commission are settled net on a quarterly basis. The ceded premium due after deducting the related ceding commission and profit commission is reported within “Other liabilities” on the consolidated balance sheets. The reinsurance recoverable on loss reserves related to our QSR Transactions was $35.3 million as of September 30, 2017 and $31.8 million as of December 31, 2016 . The reinsurance recoverable balance is secured by funds on deposit from the reinsurers which are based on the funding requirements of PMIERs that address ceded risk. Captive reinsurance In the past, MGIC also obtained captive reinsurance. In a captive reinsurance arrangement, the reinsurer is affiliated with the lender for whom MGIC provides mortgage insurance. As part of our settlement with the Consumer Financial Protection Bureau (“CFPB”) in 2013 and with the Minnesota Department of Commerce in 2015, MGIC has agreed to not enter into any new captive reinsurance agreement or reinsure any new loans under any existing captive reinsurance agreement for a period of ten years subsequent to the respective settlements. In accordance with the CFPB settlement, all of our active captive arrangements were placed into run-off. In addition, the GSEs will not approve any future reinsurance or risk sharing transaction with a mortgage enterprise or an affiliate of a mortgage enterprise. The reinsurance recoverable on loss reserves related to captive agreements was $11 million as of September 30, 2017 , which was supported by $80 million of trust assets, while as of December 31, 2016 , the reinsurance recoverable on loss reserves related to captive agreements was $19 million , which was supported by $91 million of trust assets. Each captive reinsurer is required to maintain a separate trust account to support the risk it has reinsured on all annual books. MGIC is the sole beneficiary of the trusts.

Litigation and Contingencies

Litigation and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Litigation and Contingencies	Litigation and Contingencies Before paying an insurance claim, we review the loan and servicing files to determine the appropriateness of the claim amount. When reviewing the files, we may determine that we have the right to rescind coverage on the loan. In our SEC reports, we refer to insurance rescissions and denials of claims collectively as “rescissions” and variations of that term. In addition, all of our insurance policies provide that we can reduce or deny a claim if the servicer did not comply with its obligations under our insurance policy. We call such reduction of claims “curtailments.” In recent quarters, an immaterial percentage of claims received in a quarter have been resolved by rescissions. In each of 2016 and the first nine months of 2017, curtailments reduced our average claim paid by approximately 5.5% . Our loss reserving methodology incorporates our estimates of future rescissions, curtailments, and reversals of rescissions and curtailments. A variance between ultimate actual rescission, curtailment and reversal rates and our estimates, as a result of the outcome of litigation, settlements or other factors, could materially affect our losses. When the insured disputes our right to rescind coverage or curtail claims, we generally engage in discussions in an attempt to settle the dispute. If we are unable to reach a settlement, the outcome of a dispute ultimately would be determined by legal proceedings. Under ASC 450-20, until a liability associated with settlement discussions or legal proceedings becomes probable and can be reasonably estimated, we consider our claim payment or rescission resolved for financial reporting purposes and do not accrue an estimated loss. Where we have determined that a loss is probable and can be reasonably estimated, we have recorded our best estimate of our probable loss. If we are not able to implement settlements we consider probable, we intend to defend MGIC vigorously against any related legal proceedings. In addition to matters for which we have recorded a probable loss, we are involved in other discussions and/or proceedings with insureds with respect to our claims paying practices. Although it is reasonably possible that when these matters are resolved we will not prevail in all cases, we are unable to make a reasonable estimate or range of estimates of the potential liability. We estimate the maximum exposure associated with matters where a loss is reasonably possible to be approximately $289 million , although we believe (but can give no assurance that) we will ultimately resolve these matters for significantly less than this amount. This estimate of our maximum exposure does not include interest or consequential or exemplary damages. Mortgage insurers, including MGIC, have been involved in litigation and regulatory actions related to alleged violations of the anti-referral fee provisions of the Real Estate Settlement Procedures Act, which is commonly known as RESPA, and the notice provisions of the Fair Credit Reporting Act, which is commonly known as FCRA. While these proceedings in the aggregate have not resulted in material liability for MGIC, there can be no assurance that the outcome of future proceedings, if any, under these laws would not have a material adverse affect on us. In addition, various regulators, including the CFPB, state insurance commissioners and state attorneys general may bring other actions seeking various forms of relief in connection with alleged violations of RESPA. The insurance law provisions of many states prohibit paying for the referral of insurance business and provide various mechanisms to enforce this prohibition. While we believe our practices are in conformity with applicable laws and regulations, it is not possible to predict the eventual scope, duration or outcome of any such reviews or investigations nor is it possible to predict their effect on us or the mortgage insurance industry. Through a non-insurance subsidiary, we utilize our underwriting skills to provide an outsourced underwriting service to our customers known as contract underwriting. As part of the contract underwriting activities, that subsidiary is responsible for the quality of the underwriting decisions in accordance with the terms of the contract underwriting agreements with customers. That subsidiary may be required to provide certain remedies to its customers if certain standards relating to the quality of our underwriting work are not met, and we have an established reserve for such future obligations. Claims for remedies may be made a number of years after the underwriting work was performed. The underwriting remedy expense for 2016 and the first nine months of 2017 was immaterial to our consolidated financial statements. In addition to the matters described above, we are involved in other legal proceedings in the ordinary course of business. In our opinion, based on the facts known at this time, the ultimate resolution of these ordinary course legal proceedings will not have a material adverse effect on our financial position or results of operations. See Note 11 – “Income Taxes” for a description of federal income tax contingencies.

Earnings per Share

Earnings per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share Basic earnings per share (“EPS”) is calculated by dividing net income by the weighted average number of shares of common stock outstanding. Diluted EPS includes the components of basic EPS and also gives effect to dilutive common stock equivalents. We calculate diluted EPS using the treasury stock method and if-converted method. Under the if-converted method, diluted EPS reflects the potential dilution that could occur if our convertible debt instruments result in the issuance of common stock. The determination of potentially issuable shares does not consider the satisfaction of the conversion requirements and the shares are included in the determination of diluted EPS as of the beginning of the period, if dilutive. During the quarter ended September 30, 2017 , we had 9% Debentures outstanding that could result in potentially issuable shares. For purposes of calculating basic and diluted EPS, vested restricted stock and restricted stock units ("RSUs") are considered outstanding. The following table reconciles the numerators and denominators used to calculate basic and diluted EPS. Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2017 2016 2017 2016 Basic earnings per share: Net income $ 120,027 $ 56,618 $ 328,447 $ 235,030 Weighted average common shares outstanding - basic 370,586 349,376 359,613 343,403 Basic earnings per share $ 0.32 $ 0.16 $ 0.91 $ 0.68 Diluted earnings per share: Net income $ 120,027 $ 56,618 $ 328,447 $ 235,030 Interest expense, net of tax (1) : 2% Notes — 1,324 907 5,288 5% Notes — 673 1,709 5,080 9% Debentures 3,757 — 11,270 — Diluted income available to common shareholders $ 123,784 $ 58,615 $ 342,333 $ 245,398 Weighted average common shares outstanding - basic 370,586 349,376 359,613 343,403 Effect of dilutive securities: Unvested RSUs 1,473 1,395 1,367 1,428 2% Notes — 44,488 11,119 62,707 5% Notes — 10,791 4,743 13,885 9% Debentures 19,028 — 19,028 — Weighted average common shares outstanding - diluted 391,087 406,050 395,870 421,423 Diluted earnings per share $ 0.32 $ 0.14 $ 0.86 $ 0.58 Antidilutive securities (in millions) — 19.0 — 20.4 (1) Tax effected at a rate of 35%.

Investments

Investments	9 Months Ended
	Sep. 30, 2017
Investments [Abstract]
Investments	Investments The amortized cost, gross unrealized gains and losses and fair value of the investment portfolio at September 30, 2017 and December 31, 2016 are shown below. September 30, 2017 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses (1) Fair Value U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 104,168 $ 331 $ (799 ) $ 103,700 Obligations of U.S. states and political subdivisions 2,069,592 50,505 (6,814 ) 2,113,283 Corporate debt securities 1,865,640 16,151 (6,536 ) 1,875,255 ABS 9,857 3 — 9,860 RMBS 198,756 113 (5,973 ) 192,896 CMBS 308,735 1,517 (4,827 ) 305,425 CLOs 109,417 446 (129 ) 109,734 Total debt securities 4,666,165 69,066 (25,078 ) 4,710,153 Equity securities 7,202 50 (13 ) 7,239 Total investment portfolio $ 4,673,367 $ 69,116 $ (25,091 ) $ 4,717,392 December 31, 2016 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses (1) Fair Value U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 73,847 $ 407 $ (724 ) $ 73,530 Obligations of U.S. states and political subdivisions 2,147,458 20,983 (25,425 ) 2,143,016 Corporate debt securities 1,756,461 6,059 (18,610 ) 1,743,910 ABS 59,519 74 (28 ) 59,565 RMBS 231,733 102 (7,626 ) 224,209 CMBS 327,042 769 (7,994 ) 319,817 CLOs 121,151 226 (202 ) 121,175 Total debt securities 4,717,211 28,620 (60,609 ) 4,685,222 Equity securities 7,144 8 (24 ) 7,128 Total investment portfolio $ 4,724,355 $ 28,628 $ (60,633 ) $ 4,692,350 (1) At September 30, 2017 and December 31, 2016 , there were no other-than-temporary impairment losses recorded in other comprehensive income. The FHLB Advance is secured by eligible collateral whose fair value must be maintained at 102% of the outstanding principal balance. As of September 30, 2017 , that collateral is included in our total investment portfolio amount with a total fair value of $167.2 million . The amortized cost and fair values of debt securities at September 30, 2017 , by contractual maturity, are shown in the following table. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Because most asset-backed and mortgage-backed securities and collateralized loan obligations provide for periodic payments throughout their lives, they are listed in separate categories. September 30, 2017 (In thousands) Amortized Cost Fair Value Due in one year or less $ 439,771 $ 440,227 Due after one year through five years 1,333,112 1,342,110 Due after five years through ten years 972,932 980,813 Due after ten years 1,293,585 1,329,088 $ 4,039,400 $ 4,092,238 ABS 9,857 9,860 RMBS 198,756 192,896 CMBS 308,735 305,425 CLOs 109,417 109,734 Total as of September 30, 2017 $ 4,666,165 $ 4,710,153 At September 30, 2017 and December 31, 2016 , the investment portfolio had gross unrealized losses of $25.1 million and $60.6 million , respectively. For those securities in an unrealized loss position, the length of time the securities were in such a position, as measured by their month-end fair values, is as follows: September 30, 2017 Less Than 12 Months 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 74,136 $ (524 ) $ 22,423 $ (275 ) $ 96,559 $ (799 ) Obligations of U.S. states and political subdivisions 411,460 (4,520 ) 85,700 (2,294 ) 497,160 (6,814 ) Corporate debt securities 434,056 (4,367 ) 75,592 (2,169 ) 509,648 (6,536 ) ABS 2,613 — — — 2,613 — RMBS 37,676 (713 ) 148,748 (5,260 ) 186,424 (5,973 ) CMBS 126,709 (2,375 ) 57,189 (2,452 ) 183,898 (4,827 ) CLOs 7,276 (129 ) — — 7,276 (129 ) Equity securities 381 (5 ) 171 (8 ) 552 (13 ) Total $ 1,094,307 $ (12,633 ) $ 389,823 $ (12,458 ) $ 1,484,130 $ (25,091 ) December 31, 2016 Less Than 12 Months 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 48,642 $ (724 ) $ — $ — $ 48,642 $ (724 ) Obligations of U.S. states and political subdivisions 1,136,676 (24,918 ) 13,681 (507 ) 1,150,357 (25,425 ) Corporate debt securities 915,777 (16,771 ) 35,769 (1,839 ) 951,546 (18,610 ) ABS 3,366 (28 ) 656 — 4,022 (28 ) RMBS 46,493 (857 ) 171,326 (6,769 ) 217,819 (7,626 ) CMBS 205,545 (7,529 ) 38,587 (465 ) 244,132 (7,994 ) CLOs 13,278 (73 ) 34,760 (129 ) 48,038 (202 ) Equity securities 568 (15 ) 137 (9 ) 705 (24 ) Total $ 2,370,345 $ (50,915 ) $ 294,916 $ (9,718 ) $ 2,665,261 $ (60,633 ) The unrealized losses in all categories of our investments at September 30, 2017 and December 31, 2016 were primarily caused by changes in interest rates between the time of purchase and the respective fair value measurement date. There were 343 and 607 securities in an unrealized loss position at September 30, 2017 and December 31, 2016 , respectively. During each of the three and nine months ended September 30, 2017 and 2016 there were no other-than-temporary impairments (“OTTI”) recognized. The net realized investment gains (losses) on the investment portfolio were as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Fixed maturities $ (50 ) $ 1,511 $ (227 ) $ 5,397 Equity securities 3 3,581 16 3,587 Net realized investments (losses) gains $ (47 ) $ 5,092 $ (211 ) $ 8,984 Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Gains on sales $ 32 $ 6,168 $ 861 $ 11,677 Losses on sales (79 ) (1,076 ) (1,072 ) (2,693 ) Net realized investments (losses) gains $ (47 ) $ 5,092 $ (211 ) $ 8,984

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Under the authoritative guidance, fair value is disclosed using a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value and categorizes assets and liabilities into Levels 1, 2, and 3 based on inputs available to determine their fair values. To determine the fair value of securities available-for-sale in Level 1 and Level 2 of the fair value hierarchy, independent pricing sources have been utilized. One price is provided per security based on observable market data. To ensure securities are appropriately classified in the fair value hierarchy, we review the pricing techniques and methodologies of the independent pricing sources and believe that their policies adequately consider market activity, either based on specific transactions for the issue valued or based on modeling of securities with similar credit quality, duration, yield and structure that were recently traded. A variety of inputs are utilized by the independent pricing sources including benchmark yields, reported trades, non-binding broker/dealer quotes, issuer spreads, two sided markets, benchmark securities, bids, offers and reference data including data published in market research publications. Inputs may be weighted differently for any security, and not all inputs are used for each security evaluation. Market indicators, industry and economic events are also considered. This information is evaluated using a multidimensional pricing model. This model combines all inputs to arrive at a value assigned to each security. Quality controls are performed by the independent pricing sources throughout this process, which include reviewing tolerance reports, trading information, data changes, and directional moves compared to market moves. In addition, on a quarterly basis, we perform quality controls over values received from the pricing sources which also include reviewing tolerance reports, trading information, data changes, and directional moves compared to market moves. We have not made any adjustments to the prices obtained from the independent pricing sources. In accordance with fair value accounting guidance, we applied the following fair value hierarchy to measure fair value for assets and liabilities: Level 1 - Quoted prices for identical instruments in active markets that we can access. Financial assets utilizing Level 1 inputs primarily include U.S. Treasury securities and equity securities. Level 2 - Quoted prices for similar instruments in active markets that we can access; quoted prices for identical or similar instruments in markets that are not active; and inputs, other than quoted prices, that are observable in the marketplace for the instrument. The observable inputs are used in valuation models to calculate the fair value of the instruments. Financial assets utilizing Level 2 inputs primarily include obligations of U.S. government corporations and agencies, corporate bonds, mortgage-backed securities, asset-backed securities, and most municipal bonds. The independent pricing sources utilize these approaches to determine the fair value of the instruments in Level 2 of the fair value hierarchy based on type of instrument: Corporate Debt & U.S. Government and Agency Bonds are evaluated by surveying the dealer community, obtaining relevant trade data, benchmark quotes and spreads and incorporating this information into the evaluation process. Obligations of U.S. States & Political Subdivisions are evaluated by tracking, capturing, and analyzing quotes for active issues and trades reported via the Municipal Securities Rulemaking Board records. Daily briefings and reviews of current economic conditions, trading levels, spread relationships, and the slope of the yield curve provide further data for evaluation. Residential Mortgage-Backed Securities (“RMBS”) are evaluated by monitoring interest rate movements, and other pertinent data daily. Incoming market data is enriched to derive spread, yield and/or price data as appropriate, enabling known data points to be extrapolated for valuation application across a range of related securities. Commercial Mortgage-Backed Securities (“CMBS”) are evaluated using valuation techniques that reflect market participants’ assumptions and maximize the use of relevant observable inputs including quoted prices for similar assets, benchmark yield curves and market corroborated inputs. The inputs for securities covered, including executed trades, broker quotes, credit information, collateral attributes and/or cash flow waterfall as applicable, are regularly reviewed as part of the evaluation. Asset-Backed Securities (“ABS”) are evaluated using spreads and other information solicited from market buy- and sell-side sources, including primary and secondary dealers, portfolio managers, and research analysts. Cash flows are generated for each tranche, benchmark yields are determined, and deal collateral performance and tranche level attributes including trade activity, bids, and offer are applied, resulting in tranche-specific prices. Collateralized loan obligations ("CLO") are evaluated by manager rating, seniority in the capital structure, assumptions about prepayment, default and recovery and their impact on cash flow generation. Loan level net asset values are determined and aggregated for tranches and as a final step, prices are checked against available recent trade activity. Level 3 - Valuations derived from valuation techniques in which one or more significant inputs or value drivers are unobservable or from par values for equity securities restricted in their ability to be redeemed or sold. The inputs used to derive the fair value of Level 3 securities reflect our own assumptions about the assumptions a market participant would use in pricing an asset or liability. Financial assets utilizing Level 3 inputs primarily include equity securities that can only be redeemed or sold at their par value and only to the security issuer and a state premium tax credit investment. Our non-financial assets that are classified as Level 3 securities consist of real estate acquired through claim settlement. The fair value of real estate acquired is the lower of our acquisition cost or a percentage of the appraised value. The percentage applied to the appraised value is based upon our historical sales experience adjusted for current trends. ________________________ Fair value measurements for assets measured at fair value included the following as of September 30, 2017 and December 31, 2016 : September 30, 2017 (In thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 103,700 $ 13,312 $ 90,388 $ — Obligations of U.S. states and political subdivisions 2,113,283 — 2,112,903 380 Corporate debt securities 1,875,255 — 1,875,255 — ABS 9,860 — 9,860 — RMBS 192,896 — 192,896 — CMBS 305,425 — 305,425 — CLOs 109,734 — 109,734 — Total debt securities 4,710,153 13,312 4,696,461 380 Equity securities (1) 7,239 2,971 — 4,268 Total investment portfolio $ 4,717,392 $ 16,283 $ 4,696,461 $ 4,648 Real estate acquired (2) $ 11,728 $ — $ — $ 11,728 (1) Equity securities in Level 3 are carried at cost, which approximates fair value. (2) Real estate acquired through claim settlement, which is held for sale, is reported in Other assets on the consolidated balance sheets. December 31, 2016 (In thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 73,530 $ 30,690 $ 42,840 $ — Obligations of U.S. states and political subdivisions 2,143,016 — 2,142,325 691 Corporate debt securities 1,743,910 — 1,743,910 — ABS 59,565 — 59,565 — RMBS 224,209 — 224,209 — CMBS 319,817 — 319,817 — CLOs 121,175 — 121,175 — Total debt securities 4,685,222 30,690 4,653,841 691 Equity securities (1) 7,128 2,860 — 4,268 Total investment portfolio $ 4,692,350 $ 33,550 $ 4,653,841 $ 4,959 Real estate acquired (2) $ 11,748 $ — $ — $ 11,748 (1) Equity securities in Level 3 are carried at cost, which approximates fair value. (2) Real estate acquired through claim settlement, which is held for sale, is reported in Other assets on the consolidated balance sheets. For assets measured at fair value using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances for the three and nine months ended September 30, 2017 and 2016 is shown in the following tables. There were no transfers into or out of Level 3 in those periods and there were no losses included in earnings for those periods attributable to the change in unrealized losses on assets still held at the end of the applicable period. Three Months Ended September 30, 2017 (In thousands) Debt Securities Equity Securities Total Investments Real Estate Acquired Balance at June 30, 2017 $ 577 $ 4,268 $ 4,845 $ 10,271 Total realized/unrealized gains (losses): Included in earnings and reported as losses incurred, net — — — (592 ) Purchases — — — 8,881 Sales (197 ) — (197 ) (6,832 ) Balance at September 30, 2017 $ 380 $ 4,268 $ 4,648 $ 11,728 Three Months Ended September 30, 2016 (In thousands) Debt Equity Total Real Estate Balance at June 30, 2016 $ 1,056 $ 6,940 $ 7,996 $ 9,642 Total realized/unrealized gains (losses): Included in other comprehensive income — (3,519 ) (3,519 ) — Included in earnings and reported as net realized investment gains — 3,579 3,579 — Included in earnings and reported as losses incurred, net — — — (501 ) Purchases — 1,167 1,167 8,938 Sales (226 ) (3,899 ) (4,125 ) (7,515 ) Balance at September 30, 2016 $ 830 $ 4,268 $ 5,098 $ 10,564 Nine Months Ended September 30, 2017 (In thousands) Debt Securities Equity Securities Total Investments Real Estate Acquired Balance at December 31, 2016 $ 691 $ 4,268 $ 4,959 $ 11,748 Total realized/unrealized gains (losses): Included in earnings and reported as losses incurred, net — — — (818 ) Purchases — — — 26,985 Sales (311 ) — (311 ) (26,187 ) Balance at September 30, 2017 $ 380 $ 4,268 $ 4,648 $ 11,728 Nine Months Ended September 30, 2016 (In thousands) Debt Equity Total Real Estate Balance at December 31, 2015 $ 1,228 $ 2,855 $ 4,083 $ 12,149 Total realized/unrealized gains (losses): Included in earnings and reported as net realized investment gains — 3,579 3,579 — Included in earnings and reported as losses incurred, net — — — (143 ) Purchases — 4,258 4,258 27,953 Sales (398 ) (6,424 ) (6,822 ) (29,395 ) Balance at September 30, 2016 $ 830 $ 4,268 $ 5,098 $ 10,564 Authoritative guidance over disclosures about the fair value of financial instruments requires additional disclosure for financial instruments not measured at fair value. Certain financial instruments, including insurance contracts, are excluded from these fair value disclosure requirements. The carrying values of cash and cash equivalents (Level 1) and accrued investment income (Level 2) approximated their fair values. Additional fair value disclosures related to our investment portfolio are included in Note 7 – “Investments.” Financial Liabilities Not Measured at Fair Value We incur financial liabilities in the normal course of our business. The following table presents the carrying value and fair value of our financial liabilities disclosed, but not carried, at fair value at September 30, 2017 and December 31, 2016 . The fair values of our 5% Notes, 2% Notes, 5.75% Notes, and 9% Debentures were based on observable market prices. The fair value of the FHLB Advance was estimated using discounted cash flows on current incremental borrowing rates for similar borrowing arrangements. In all cases the fair values of the financial liabilities below are categorized as Level 2. September 30, 2017 December 31, 2016 (In thousands) Carrying Value Fair Value Carrying Value Fair Value FHLB Advance 155,000 154,175 $ 155,000 $ 151,905 5% Notes — — 144,789 147,679 2% Notes — — 204,672 308,605 5.75% Notes 418,271 468,248 417,406 445,987 9% Debentures 256,872 349,798 256,872 323,040 Total financial liabilities $ 830,143 $ 972,221 $ 1,178,739 $ 1,377,216

Other Comprehensive Income

Other Comprehensive Income	9 Months Ended
	Sep. 30, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other Comprehensive Income	Other Comprehensive Income The pretax and related income tax (expense) benefit components of our other comprehensive income (loss) for the three and nine months ended September 30, 2017 and 2016 are included in the following table. Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Net unrealized investment gains (losses) arising during the period $ 17,761 $ (22,206 ) $ 76,022 $ 142,852 Income tax (expense) benefit (6,217 ) 7,772 (26,608 ) (50,121 ) Net of taxes 11,544 (14,434 ) 49,414 92,731 Net changes in benefit plan assets and obligations (226 ) (370 ) (680 ) (1,110 ) Income tax benefit 79 129 238 388 Net of taxes (147 ) (241 ) (442 ) (722 ) Net changes in unrealized foreign currency translation adjustment — (16 ) 45 (1,496 ) Income tax benefit (expense) — 6 (14 ) 522 Net of taxes — (10 ) 31 (974 ) Total other comprehensive income (loss) 17,535 (22,592 ) 75,387 140,246 Total income tax (expense) benefit (6,138 ) 7,907 (26,384 ) (49,211 ) Total other comprehensive income (loss), net of tax $ 11,397 $ (14,685 ) $ 49,003 $ 91,035 The pretax and related income tax benefit (expense) components of the amounts reclassified from our accumulated other comprehensive loss (“AOCL”) to our consolidated statements of operations for the three and nine months ended September 30, 2017 and 2016 are included in the following table. Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Reclassification adjustment for net realized (losses) gains (1) $ (427 ) $ 5,248 $ (2,566 ) $ 5,958 Income tax benefit (expense) 150 (1,837 ) 898 (1,963 ) Net of taxes (277 ) 3,411 (1,668 ) 3,995 Reclassification adjustment related to benefit plan assets and obligations (2) 226 370 680 1,110 Income tax (expense) (79 ) (129 ) (238 ) (388 ) Net of taxes 147 241 442 722 Reclassification adjustment related to foreign currency (3) — — — 1,467 Income tax (expense) — — — (513 ) Net of taxes — — — 954 Total reclassifications (201 ) 5,618 (1,886 ) 8,535 Total income tax benefit (expense) 71 (1,966 ) 660 (2,864 ) Total reclassifications, net of tax $ (130 ) $ 3,652 $ (1,226 ) $ 5,671 (1) Increases (decreases) Net realized investment (losses) gains on the consolidated statements of operations. (2) Decreases (increases) Other underwriting and operating expenses, net on the consolidated statements of operations. (3) Increases (decreases) Other revenue on the consolidated statements of operations. A rollforward of AOCL for the nine months ended September 30, 2017 , including amounts reclassified from AOCL, are included in the table below. Nine Months Ended September 30, 2017 (In thousands) Net unrealized gains and losses on available-for-sale securities Net benefit plan assets and obligations recognized in shareholders' equity Net unrealized foreign currency translation Total AOCL Balance, December 31, 2016, net of tax $ (20,797 ) $ (54,272 ) $ (31 ) $ (75,100 ) Other comprehensive income before reclassifications 47,746 — 31 47,777 Less: Amounts reclassified from AOCL (1,668 ) 442 — (1,226 ) Balance, September 30, 2017, net of tax $ 28,617 $ (54,714 ) $ — $ (26,097 )

Benefit Plans

Benefit Plans	9 Months Ended
	Sep. 30, 2017
Retirement Benefits [Abstract]
Benefit Plans	Benefit Plans The following tables provide the components of net periodic benefit cost for our pension, supplemental executive retirement and other postretirement benefit plans for the three and nine months ended September 30, 2017 and 2016 : Three Months Ended September 30, Pension and Supplemental Executive Retirement Plans Other Postretirement Benefit Plans (In thousands) 2017 2016 2017 2016 Service cost $ 2,389 $ 2,283 $ 203 $ 188 Interest cost 3,869 3,976 176 176 Expected return on plan assets (5,025 ) (4,877 ) (1,312 ) (1,222 ) Recognized net actuarial loss 1,543 1,464 — — Amortization of prior service cost (107 ) (172 ) (1,662 ) (1,662 ) Net periodic benefit cost (benefit) $ 2,669 $ 2,674 $ (2,595 ) $ (2,520 ) Nine Months Ended September 30, Pension and Supplemental Executive Retirement Plans Other Postretirement Benefit Plans (In thousands) 2017 2016 2017 2016 Service cost $ 7,167 $ 6,848 $ 610 $ 564 Interest cost 11,606 11,929 529 528 Expected return on plan assets (15,074 ) (14,631 ) (3,936 ) (3,665 ) Recognized net actuarial loss 4,627 4,392 — — Amortization of prior service cost (320 ) (515 ) (4,987 ) (4,987 ) Net periodic benefit cost (benefit) $ 8,006 $ 8,023 $ (7,784 ) $ (7,560 ) We have made contributions totaling $9.3 million to our qualified pension plan and supplemental executive retirement plan in 2017.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We have approximately $987.6 million of net operating loss (“NOL”) carryforwards on a regular tax basis and $117.9 million of NOL carryforwards for computing the alternative minimum tax as of September 30, 2017 . Any unutilized carryforwards are scheduled to expire at the end of tax years 2032 through 2033. We evaluate the realizability of our deferred tax assets including our NOL carryforwards on a quarterly basis. Based on our analysis, we have concluded that all of our deferred tax assets are fully realizable and therefore no valuation allowance existed at September 30, 2017 and December 31, 2016. Tax Contingencies As previously disclosed, the Internal Revenue Service (“IRS”) completed examinations of our federal income tax returns for the years 2000 through 2007 and issued proposed assessments for taxes, interest and penalties related to our treatment of the flow-through income and loss from an investment in a portfolio of residual interests of Real Estate Mortgage Investment Conduits (“REMICs”). The IRS indicated that it did not believe that, for various reasons, we had established sufficient tax basis in the REMIC residual interests to deduct the losses from taxable income. We appealed these assessments within the IRS and in August 2010, we reached a tentative settlement agreement with the IRS which was not finalized. In 2014, we received Notices of Deficiency (commonly referred to as “90 day letters”) covering the 2000-2007 tax years. The Notices of Deficiency reflect taxes and penalties related to the REMIC matters of $197.5 million and at September 30, 2017 , there would also be interest related to these matters of approximately $200.3 million . In 2007, we made a payment of $65.2 million to the United States Department of the Treasury which will reduce any amounts we would ultimately owe. The Notices of Deficiency also reflect additional amounts due of $261.4 million , which are primarily associated with the disallowance of the carryback of the 2009 net operating loss to the 2004-2007 tax years. We believe the IRS included the carryback adjustments as a precaution to keep open the statute of limitations on collection of the tax that was refunded when this loss was carried back, and not because the IRS actually intends to disallow the carryback permanently. Depending on the outcome of this matter, additional state income taxes and state interest may become due when a final resolution is reached. As of September 30, 2017 , those state taxes and interest would approximate $84.1 million . In addition, there could also be state tax penalties. Our total amount of unrecognized tax benefits as of September 30, 2017 is $141.8 million , which represents the tax benefits generated by the REMIC portfolio included in our tax returns that we have not taken benefit for in our financial statements, including any related interest. We filed a petition with the U.S. Tax Court contesting most of the IRS' proposed adjustments reflected in the Notices of Deficiency and the IRS filed an answer to our petition which continued to assert their claim. The case has twice been scheduled for trial and in each instance, the parties jointly filed, and the U.S. Tax Court approved (most recently in February 2016), motions for continuance to postpone the trial date. Also in February 2016, the U.S. Tax Court approved a joint motion to consolidate for trial, briefing and opinion, our case with similar cases of Radian Group, Inc., as successor to Enhance Financial Services Group, Inc., et al. The parties informed the Tax Court in August 2017 that they had reached agreement in principle on all issues in the case and were preparing the documentation reflecting the terms of their agreement. The agreed settlement terms will be subject to review by the Joint Committee on Taxation ("JCT") before a settlement can be completed and there is no assurance that a settlement will be completed. Based on information that we currently have regarding the status of our ongoing dispute, we recorded a provision for additional taxes and interest of $28.4 million in the first nine months of 2017. Should a settlement not be completed, ongoing litigation to resolve our dispute with the IRS could be lengthy and costly in terms of legal fees and related expenses. We would need to make further adjustments, which could be material, to our tax provision and liabilities if our view of the probability of success in this matter changes, and the ultimate resolution of this matter could have a material negative impact on our effective tax rate, results of operations, cash flows, available assets and statutory capital. In this regard, see Note 15 - “Statutory Information.” The total amount of the unrecognized tax benefits, related to our aforementioned REMIC issue that would affect our effective tax rate is $119.8 million . We recognize interest accrued and penalties related to unrecognized tax benefits in income taxes. As of September 30, 2017 and December 31, 2016 , we had accrued $50.8 million and $28.9 million , respectively, for the payment of interest.

Loss Reserves

Loss Reserves	9 Months Ended
	Sep. 30, 2017
Insurance Loss Reserves [Abstract]
Loss Reserves	Loss Reserves We establish reserves to recognize the estimated liability for losses and loss adjustment expenses (“LAE”) related to defaults on insured mortgage loans. Loss reserves are established by estimating the number of loans in our inventory of delinquent loans that will result in a claim payment, which is referred to as the claim rate, and further estimating the amount of the claim payment, which is referred to as claim severity. Estimation of losses is inherently judgmental. The conditions that affect the claim rate and claim severity include the current and future state of the domestic economy, including unemployment and the current and future strength of local housing markets; exposure on insured loans; the amount of time between default and claim filing; and curtailments and rescissions. The actual amount of the claim payments may be substantially different than our loss reserve estimates. Our estimates could be adversely affected by several factors, including a deterioration of regional or national economic conditions, including unemployment, leading to a reduction in borrowers’ income and thus their ability to make mortgage payments, and a drop in housing values which may affect borrower willingness to continue to make mortgage payments when the value of the home is below the mortgage balance. Changes to our estimates could result in a material impact to our consolidated results of operations and financial position, even in a stable economic environment. The “Losses incurred” section of the table below shows losses incurred on defaults that occurred in the current year and in prior years. The amount of losses incurred relating to defaults that occurred in the current year represents the estimated amount to be ultimately paid on such defaults. The amount of losses incurred relating to defaults that occurred in prior years represents the difference between the actual claim rate and severity associated with those defaults resolved in the current year compared to the estimated claim rate and severity at the prior year-end, as well as a re-estimation of amounts to be ultimately paid on defaults continuing from the end of the prior year. This re-estimation of the claim rate and severity is the result of our review of current trends in the default inventory, such as percentages of defaults that have resulted in a claim, the amount of the claims relative to the average loan exposure, changes in the relative level of defaults by geography and changes in average loan exposure. Losses incurred on defaults that occurred in the current year decreased in the first nine months of 2017 compared to the same period in 2016 , primarily due to a decrease in the estimated claim rate on recently reported defaults and a decrease in the number of new defaults, net of related cures. For the nine months ended September 30, 2017 and 2016 we experienced favorable prior year loss reserve development, in large part, due to the resolution of approximately 59% and 54% , respectively, of the prior year default inventory, with improved cure rates. The “Losses paid” section of the table below shows the amount of losses paid on default notices received in the current year and losses paid on default notices received in prior years. For several years, the average time it took to receive a claim associated with a default had increased significantly from our historical experience of approximately twelve months. This was, in part, due to new loss mitigation protocols established by servicers and to changes in some state foreclosure laws that may include, for example, a requirement for additional review and/or mediation processes. In recent quarters, we have experienced a decline in the average time servicers are utilizing to process foreclosures, which has reduced the average time to receive a claim associated with new notices of default that do not cure. All else being equal, the longer the period between default and claim filing, the greater the severity. During the first nine months of 2017 and 2016, our losses paid included amounts paid on commutations of coverage on pools of non-performing loans (“NPLs”) and in 2016, our losses paid also included amounts paid in connection with disputes concerning our claims paying practices. The impacts of the commutations of NPLs and settlements were as follows: • 2017 - 1,337 notices removed from default inventory with an amount paid of $54 million . • 2016 - 1,273 notices removed from default inventory with an amount paid of $52 million . Our estimate of premiums to be refunded on expected claim payments is accrued for separately in “Other Liabilities” on our consolidated balance sheets and approximated $68 million and $85 million at September 30, 2017 and December 31, 2016 , respectively. The following table provides a reconciliation of beginning and ending loss reserves as of and for the nine months ended September 30, 2017 and 2016 : Nine months ended September 30, (In thousands) 2017 2016 Reserve at beginning of period $ 1,438,813 $ 1,893,402 Less reinsurance recoverable 50,493 44,487 Net reserve at beginning of period 1,388,320 1,848,915 Losses incurred: Losses and LAE incurred in respect of default notices received in: Current year 219,485 292,090 Prior years (1) (134,780 ) (99,591 ) Total losses incurred 84,705 192,499 Losses paid: Losses and LAE paid in respect of default notices received in: Current year 5,474 5,942 Prior years 407,977 549,706 Reinsurance terminations (2) 301 (2,854 ) Total losses paid 413,752 552,794 Net reserve at end of period 1,059,273 1,488,620 Plus reinsurance recoverables 45,878 46,863 Reserve at end of period $ 1,105,151 $ 1,535,483 (1) A negative number for prior year losses incurred indicates a redundancy of prior year loss reserves. See the following table for more information about prior year loss development. (2) In a termination, the reinsurance agreement is cancelled, with no future premium ceded and amounts for any incurred but unpaid losses paid to us. Amounts paid to (received from) reinsurers result in an increase (decrease) in net losses paid. The change in net losses paid on our losses incurred is offset by a corresponding change in the reinsurance recoverable, resulting in no net impact on losses incurred. The prior year development of the reserves in the first nine months of 2017 and 2016 is reflected in the following table. Nine months ended September 30, (In millions) 2017 2016 Decrease in estimated claim rate on primary defaults $ (138 ) $ (108 ) (Decrease) increase in estimated severity on primary defaults (2 ) 12 Change in estimates related to pool reserves, LAE reserves and reinsurance 5 (4 ) Total prior year loss development (1) $ (135 ) $ (100 ) (1) A negative number for prior year loss development indicates a redundancy of prior year loss reserves. Default inventory A rollforward of our primary default inventory for the three and nine months ended September 30, 2017 and 2016 appears in the following table. The information concerning new notices and cures is compiled from monthly reports received from loan servicers. The level of new notice and cure activity reported in a particular month can be influenced by, among other things, the date on which a servicer generates its report, the accuracy of the data provided by servicers, the number of business days in a month, transfers of servicing between loan servicers and whether all servicers have provided the reports in a given month. Three months ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Default inventory at beginning of period 41,317 52,558 50,282 62,633 New notices 15,950 17,607 45,352 50,418 Cures (13,546 ) (15,556 ) (45,382 ) (50,249 ) Paids (including those charged to a deductible or captive) (2,195 ) (3,051 ) (7,403 ) (9,619 ) Rescissions and denials (82 ) (125 ) (277 ) (477 ) Other items removed from inventory (209 ) — (1,337 ) (1,273 ) Default inventory at end of period 41,235 51,433 41,235 51,433 The decrease in the primary default inventory experienced during 2017 and 2016 was generally across all markets and primarily in book years 2008 and prior. Historically as a default ages it becomes more likely to result in a claim. Subsequent event As shown in the table below, we received an increased number of new default notices in October 2017 compared to October 2016 related to loans in locations that the Federal Emergency Management Agency has declared Individual Assistance Disaster Areas (“IADA”) in connection with recent hurricane activity primarily impacting Texas, Florida, and Puerto Rico. For the month ended October 31, 2017 2016 Default notices for loans in IADAs 3,394 637 Other default notices 4,549 4,882 Total default notices 7,943 5,519 The number of consecutive months a borrower is delinquent is shown in the following table. Consecutive months in default September 30, 2017 December 31, 2016 September 30, 2016 3 months or less 11,331 27 % 12,194 24 % 12,333 24 % 4-11 months 11,092 27 % 13,450 27 % 12,648 25 % 12 months or more (1) (2) 18,812 46 % 24,638 49 % 26,452 51 % Total primary default inventory 41,235 100 % 50,282 100 % 51,433 100 % Primary claims received inventory included in ending default inventory: 1,063 3 % 1,385 3 % 1,636 3 % (1) Approximately 45% , 47% , and 48% of the primary default inventory in default for 12 consecutive months or more has been in default for at least 36 consecutive months as of September 30, 2017 , December 31, 2016 , and September 30, 2016 , respectively. (2) The majority of items removed from our default inventory were due to commutations of NPLs during the nine months ended September 30, 2017 were in default for 12 consecutive months or more as of December 31, 2016. The number of months a loan is in the default inventory can differ from the number of payments that the borrower has not made or is considered delinquent. These differences typically result from a borrower making monthly payments that do not result in the loan becoming fully current. The number of payments that a borrower is delinquent is shown in the following table. Number of payments delinquent September 30, 2017 December 31, 2016 September 30, 2016 3 payments or less 16,916 41 % 18,419 36 % 18,374 36 % 4-11 payments 10,583 26 % 12,892 26 % 12,282 24 % 12 payments or more (1) 13,736 33 % 18,971 38 % 20,777 40 % Total primary default inventory 41,235 100 % 50,282 100 % 51,433 100 % (1) The majority of items removed from our default inventory were due to commutations of NPLs during the nine months ended September 30, 2017 had 12 or more payments delinquent as of December 31, 2016. Pool insurance default inventory decreased to 1,426 at September 30, 2017 from 1,883 at December 31, 2016 , and 1,979 at September 30, 2016 . Claims paying practices Our loss reserving methodology incorporates our estimates of future rescissions and curtailments. A variance between ultimate actual rescission and curtailment rates and our estimates, as a result of the outcome of litigation, settlements or other factors, could materially affect our losses. Our estimate of premiums to be refunded on expected future rescissions is accrued for separately and is included in “Other liabilities” on our consolidated balance sheets. For information about discussions and legal proceedings with customers with respect to our claims paying practices see Note 5 – “Litigation and Contingencies.”

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders’ Equity Change in accounting principle As described in Note 2 - “New Accounting Pronouncements,” during the first quarter of 2017 we adopted the updated guidance of “ Improvements to Employee Share-Based Compensation Accounting .” The adoption of this guidance resulted in an immaterial cumulative effect adjustment to our 2017 beginning retained earnings. 2017 Capital transactions 2% Notes As described in Note 3 - “Debt,” in April, holders of approximately $202.5 million of the outstanding principal amount of our 2% Notes exercised their rights to convert their notes into shares of our common stock. As a result, we issued approximately 29.1 million shares of our common stock, of which 18.7 million shares were reissued from our treasury stock and 10.4 million were newly issued shares. The conversions of the notes increased our shareholders’ equity by the carrying value of the notes at the time of conversion. 2016 Capital transactions As described in Note 3 - “Debt,” in the third quarter of 2016, we issued approximately 18.3 million shares of our common stock as consideration for the purchase of certain of our 2% Notes. In the third quarter of 2016, we repurchased an aggregate of approximately 13.5 million shares of our common stock, of which approximately 2.1 million shares were unsettled as of September 30, 2016, at a weighted average price per share of $8.02 , which included commissions. The aggregate purchase price of the shares was $108.1 million , which included approximately $16.5 million of cash settled after September 30, 2016. An additional 4.8 million shares were repurchased in October 2016. As described in Note 3 - “Debt” the purchase of a portion of our 9% Debentures by MGIC, and corresponding elimination of the purchased 9% Debentures in consolidation, resulted in a reduction to our consolidated shareholders’ equity of approximately $6.3 million . This reduction represented the allocated portion of the consideration paid to reacquire the equity component of the 9% Debentures. The reduction was recognized in paid-in capital and was less than the amount ascribed to paid-in capital at original issuance of the 9% Debentures. Shareholders Rights Agreement Our Amended and Restated Rights Agreement dated July 23, 2015 seeks to diminish the risk that our ability to use our NOLs to reduce potential future federal income tax obligations may become substantially limited and to deter certain abusive takeover practices. The benefit of the NOLs would be substantially limited, and the timing of the usage of the NOLs could be substantially delayed, if we were to experience an “ownership change” as defined by Section 382 of the Internal Revenue Code. Under the Agreement each outstanding share of our Common Stock is accompanied by one Right. The “Distribution Date” occurs on the earlier of ten days after a public announcement that a person has become an “Acquiring Person,” or ten business days after a person announces or begins a tender offer in which consummation of such offer would result in a person becoming an “Acquiring Person.” An “Acquiring Person” is any person that becomes, by itself or together with its affiliates and associates, a beneficial owner of 5% or more of the shares of our Common Stock then outstanding, but excludes, among others, certain exempt and grandfathered persons as defined in the Agreement. The Rights are not exercisable until the Distribution Date. Each Right will initially entitle shareholders to buy one-tenth of one share of our Common Stock at a Purchase Price of $45 per full share (equivalent to $4.50 for each one-tenth share), subject to adjustment. Each exercisable Right (subject to certain limitations) will entitle its holder to purchase, at the Rights’ then-current Purchase Price, a number of our shares of Common Stock (or if after the Shares Acquisition Date, we are acquired in a business combination, common shares of the acquiror) having a market value at the time equal to twice the Purchase Price. The Rights will expire on August 1, 2018, or earlier as described in the Agreement. The Rights are redeemable at a price of $0.001 per Right at any time prior to the time a person becomes an Acquiring Person. Other than certain amendments, the Board of Directors may amend the Rights in any respect without the consent of the holders of the Rights.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation We have certain share-based compensation plans. Under the fair value method, compensation cost is measured at the grant date based on the fair value of the award and is recognized over the service period which generally corresponds to the vesting period. Awards under our plans generally vest over periods ranging from one to three years . The number of shares granted to employees and the weighted average fair value per share during the periods presented were (shares in thousands): Nine months ended September 30, 2017 2016 Shares Granted Weighted Average Share Fair Value Shares Granted Weighted Average Share Fair Value RSUs subject to performance conditions 1,237 $ 10.41 1,257 $ 5.66 RSUs subject only to service conditions 395 10.41 433 5.67

Statutory Information

Statutory Information	9 Months Ended
	Sep. 30, 2017
Statutory Capital [Abstract]
Statutory Information	Statutory Information Statutory Capital Requirements The insurance laws of 16 jurisdictions, including Wisconsin, our domiciliary state, require a mortgage insurer to maintain a minimum amount of statutory capital relative to the risk in force (or a similar measure) in order for the mortgage insurer to continue to write new business. We refer to these requirements as the “State Capital Requirements.” While they vary among jurisdictions, the most common State Capital Requirements allow for a maximum risk-to-capital ratio of 25 to 1 . A risk-to-capital ratio will increase if (i) the percentage decrease in capital exceeds the percentage decrease in insured risk, or (ii) the percentage increase in capital is less than the percentage increase in insured risk. Wisconsin does not regulate capital by using a risk-to-capital measure but instead requires a minimum policyholder position (“MPP”). The “policyholder position” of a mortgage insurer is its net worth or surplus, contingency reserve and a portion of the reserves for unearned premiums. At September 30, 2017 , MGIC’s risk-to-capital ratio was 10.1 to 1 , below the maximum allowed by the jurisdictions with State Capital Requirements, and its policyholder position was $1.9 billion above the required MPP of $1.2 billion . In calculating our risk-to-capital ratio and MPP, we are allowed full credit for the risk ceded under our reinsurance transactions with a group of unaffiliated reinsurers. It is possible that under the revised State Capital Requirements discussed below, MGIC will not be allowed full credit for the risk ceded to the reinsurers. If MGIC is not allowed an agreed level of credit under either the State Capital Requirements or the financial requirements of the PMIERs, MGIC may terminate the reinsurance transactions, without penalty. At this time, we expect MGIC to continue to comply with the current State Capital Requirements; however, you should read the rest of these financial statement footnotes for information about matters that could negatively affect such compliance. At September 30, 2017 , the risk-to-capital ratio of our combined insurance operations (which includes a reinsurance affiliate) was 11.1 to 1 . Reinsurance agreements with an affiliate permit MGIC to write insurance with a higher coverage percentage than it could on its own under certain state-specific requirements. A higher risk-to-capital ratio on a combined basis may indicate that, in order for MGIC to continue to utilize reinsurance agreements with its affiliate, additional capital contributions to the reinsurance affiliate could be needed. We ask the Commissioner of Insurance of the State of Wisconsin (the “OCI”) not to object before MGIC pays dividends. In the third quarter of 2017, MGIC paid a $40 million dividend to our holding company. MGIC is subject to statutory regulations as to payment of dividends. The maximum amount of dividends that MGIC may pay in any twelve-month period without regulatory approval by the OCI is the lesser of adjusted statutory net income or 10% of statutory policyholders’ surplus as of the preceding calendar year end. Adjusted statutory net income is defined for this purpose to be the greater of statutory net income, net of realized investment gains, for the calendar year preceding the date of the dividend or statutory net income, net of realized investment gains, for the three calendar years preceding the date of the dividend less dividends paid within the first two of the preceding three calendar years. The OCI recognizes only statutory accounting practices prescribed or permitted by the State of Wisconsin for determining and reporting the financial condition and results of operations of an insurance company. The OCI has adopted certain prescribed accounting practices that differ from those found in other states. Specifically, Wisconsin domiciled companies record changes in the contingency reserves through the income statement as changes in underwriting deductions. As a result, in periods in which MGIC is increasing contingency reserves, statutory net income is lowered. For the year ended December 31, 2016 , MGIC’s statutory net income was reduced by $490 million to account for the increase in contingency reserves. The NAIC plans to revise the minimum capital and surplus requirements for mortgage insurers that are provided for in its Mortgage Guaranty Insurance Model Act. In May 2016, a working group of state regulators released an exposure draft of a risk-based capital framework to establish capital requirements for mortgage insurers, although no date has been established by which the NAIC must propose revisions to the capital requirements and certain items have not yet been completely addressed by the framework, including the treatment of ceded risk, minimum capital floors, and action level triggers. Currently, we believe that the PMIERs contain the more restrictive capital requirements in most circumstances. While MGIC currently meets the State Capital Requirements of Wisconsin and all other jurisdictions, it could be prevented from writing new business in the future in all jurisdictions if it fails to meet the State Capital Requirements of Wisconsin, or it could be prevented from writing new business in another jurisdiction if it fails to meet the State Capital Requirements of that jurisdiction, and in each case MGIC does not obtain a waiver of such requirements. It is possible that regulatory action by one or more jurisdictions, including those that do not have specific State Capital Requirements, may prevent MGIC from continuing to write new insurance in such jurisdictions. If we are unable to write business in all jurisdictions, lenders may be unwilling to procure insurance from us anywhere. In addition, a lender’s assessment of the future ability of our insurance operations to meet the State Capital Requirements or the PMIERs may affect its willingness to procure insurance from us. A possible future failure by MGIC to meet the State Capital Requirements or the PMIERs will not necessarily mean that MGIC lacks sufficient resources to pay claims on its insurance liabilities. While we believe MGIC has sufficient claims paying resources to meet its claim obligations on its insurance in force on a timely basis, you should read the rest of these financial statement footnotes for information about matters that could negatively affect MGIC’s claims paying resources.

New Accounting Pronouncements (

New Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Adopted Accounting Standards and Prospective Accounting Standards	Adopted Accounting Standards Improvements to Employee Share-Based Compensation Accounting In March 2016, the Financial Accounting Standards Board (“FASB”) issued updated guidance that simplifies several aspects of the accounting for employee share-based compensation including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification of related amounts within the statement of cash flows. The updated guidance requires that, prospectively, all tax effects related to share-based compensation be made through the statement of operations at the time of settlement. In contrast, the previous guidance required excess tax benefits to be recognized in paid-in capital. The updated guidance also removes the requirement to delay recognition of a tax benefit until it reduces current taxes payable. This change is required to be applied on a modified retrospective basis, with a cumulative effect adjustment to opening retained earnings. Additionally, all tax related cash flows resulting from share-based compensation are to be reported as operating activities on the statement of cash flows, a change from the existing requirement to present tax benefits as an inflow from financing activities and an outflow from operating activities. Finally, for tax withholding purposes, entities will be allowed to withhold an amount of shares up to the employee’s maximum individual tax rate (as opposed to the minimum statutory tax rate) in the relevant jurisdiction without resulting in liability classification of the award. The change in tax withholding is to be applied on a modified retrospective approach. This updated guidance became effective January 1, 2017. We adopted this guidance in the first quarter of 2017 and because of the adoption: • We recognized discrete tax benefits of $1.5 million in the provision for income taxes on our statement of operations for the nine months ended September 30, 2017 related to excess tax benefits upon vesting of share-based awards during the period. • We recognized a cumulative effect adjustment in opening retained earnings as of January 1, 2017 related to the recognition of a deferred tax asset related to suspended tax benefits from vesting transactions occurring in prior years and from the elimination of our forfeiture estimate on share-based awards, which was previously applied only to awards with service conditions. • We reclassified excess tax benefits related to share-based compensation for 2016 to operating activities from financing activities. • We reclassified employee taxes paid for withheld shares for 2016 to financing activities from operating activities. Prospective Accounting Standards Stock Compensation - Scope of Modification Accounting In May 2017, the FASB issued updated guidance related to a change in the terms or conditions (modification) of a share-based award. The updated guidance provides that an entity should account for the effects of a modification unless the fair value and vesting conditions of the modified award and the classification of the award (equity or liability instrument) are the same as the original award immediately before the modification. The updated guidance addresses the current diversity in practice on applying modification accounting, as some entities evaluate whether changes to awards are substantive, which is not prescribed within the current accounting guidance. The updated guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. Early adoption is permitted, including adoption in any interim period. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. Premium Amortization on Purchased Callable Debt Securities In March 2017, the FASB issued updated guidance to amend the amortization period for certain purchased callable debt securities held at a premium shortening the amortization period to the earliest call date. Under current GAAP, there is diversity in practice in the amortization period for premiums of callable debt securities and in how the potential for exercise of a call is factored into current impairment assessments. This updated guidance aligns with how callable debt securities, in the United States, are generally quoted, priced, and traded assuming a model that incorporates consideration of calls (also referred to as “yield-to-worst” pricing). The updated guidance is effective for annual periods beginning after December 15, 2018, including interim periods within those annual periods. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. We currently account for premium amortization on our purchased callable debt securities on a yield-to-worst basis, which generally aligns with the earliest call date. Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost In March 2017, the FASB issued updated guidance that improves the reporting of net benefit cost in the financial statements. The updated guidance requires that an employer report the service cost component in the same financial statement caption as other compensation costs arising from services rendered by employees during the period. The other components of net benefit cost are required to be presented in the statement of operations separately from the service cost component and outside a subtotal of income from operations, if one is presented. Current guidance does not prescribe where the amount of net benefit cost should be presented in an employer’s statement of operations and does not require entities to disclose by line item the amount of net benefit cost that is included in the statement of operations. The updated guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued updated guidance that requires immediate recognition of estimated credit losses expected to occur over the remaining life of many financial instruments. Entities will be required to utilize a current expected credit losses (“CECL”) methodology that incorporates their forecasts of future economic conditions into their loss estimate unless such forecast is not reasonable and supportable, in which case the entity will revert to historical loss experience. Any allowance for CECL reduces the amortized cost basis of the financial instrument to the amount an entity expects to collect. Credit losses relating to available-for-sale fixed maturity securities are to be recorded through an allowance for credit losses, rather than a write-down of the asset, with the amount of the allowance limited to the amount by which fair value is less than amortized cost. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists. The updated guidance is not prescriptive about certain aspects of estimating expected credit losses, including the specific methodology to use, and therefore will require significant judgment in application. The updated guidance is effective for annual periods beginning after December 15, 2019, including interim periods within those annual periods. Early adoption is permitted for annual and interim periods in fiscal years beginning after December 15, 2018. We are currently evaluating the impacts the adoption of this guidance will have on our consolidated financial statements, but do not expect it to have a material impact on our consolidated financial statements or disclosures. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued updated guidance to address the recognition, measurement, presentation, and disclosure of certain financial instruments. The updated guidance requires equity investments, except those accounted for under the equity method of accounting, that have a readily determinable fair value to be measured at fair value with changes in fair value recognized in net income. Equity investments that do not have readily determinable fair values may be remeasured at fair value either upon the occurrence of an observable price change or upon identification of an impairment. A qualitative assessment for impairment is required for equity investments without readily determinable fair values. The updated guidance also eliminates the requirement to disclose the method and significant assumptions used to estimate the fair value of financial instruments measured at amortized cost on the balance sheet. Further, the updated guidance clarifies that entities should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entities other deferred tax assets. The updated guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods and will require recognition of a cumulative effect adjustment at adoption. We do not currently expect the adoption of this guidance to impact our consolidated financial statements or disclosures.

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Long-term debt	The par value of our long-term debt obligations and their aggregate carrying values as of September 30, 2017 and December 31, 2016 were as follows. (In millions) September 30, December 31, FHLB Advance $ 155.0 $ 155.0 5% Notes — 145.0 2% Notes — 207.6 5.75% Notes 425.0 425.0 9% Debentures (1) 256.9 256.9 Long-term debt, par value 836.9 1,189.5 Debt issuance costs (6.8 ) (10.8 ) Long-term debt, carrying value $ 830.1 $ 1,178.7 (1) Convertible at any time prior to maturity at the holder’s option, at an initial conversion rate, which is subject to adjustment, of 74.0741 shares per $1,000 principal amount, representing an initial conversion price of approximately $13.50 per share. If a holder elects to convert their debentures, deferred interest owed on the debentures being converted is also converted into shares of our common stock. The conversion rate for any deferred interest is based on the average price that our shares traded at during a 5 -day period immediately prior to the election to convert. In lieu of issuing shares of common stock upon conversion of the debentures, we may, at our option, make a cash payment to converting holders for all or some of the shares of our common stock otherwise issuable upon conversion.
Interest payments made	Interest payments on our debt obligations appear below. Nine Months Ended September 30, (In millions) 2017 2016 Revolving credit facility $ 0.5 $ — FHLB Advance 2.2 1.7 5% Notes 3.6 6.9 2% Notes 2.1 7.0 5.75% Notes 25.1 — 9% Debentures 11.6 15.9 Total interest payments $ 45.1 $ 31.5

Reinsurance (Tables)

Reinsurance (Tables)	9 Months Ended
	Sep. 30, 2017
Reinsurance Disclosures [Abstract]
Effect of reinsurance agreement	The effect of all of our reinsurance agreements on premiums earned and losses incurred is as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Premiums earned: Direct $ 268,709 $ 270,718 $ 789,317 $ 789,671 Assumed 312 152 472 542 Ceded (31,938 ) (33,494 ) (92,467 ) (100,040 ) Net premiums earned $ 237,083 $ 237,376 $ 697,322 $ 690,173 Losses incurred: Direct $ 35,313 $ 69,579 $ 99,122 $ 216,874 Assumed (97 ) 241 69 681 Ceded (5,469 ) (8,923 ) (14,486 ) (25,056 ) Losses incurred, net $ 29,747 $ 60,897 $ 84,705 $ 192,499
Effect of quota share reinsurance agreements on premiums earned and losses incurred	Following is a summary of our quota share reinsurance agreements, excluding captive agreements discussed below, for the three and nine months ended September 30, 2017 and 2016 . Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Ceded premiums written and earned, net of profit commission (1) $ 30,880 $ 31,707 $ 88,692 $ 93,334 Ceded losses incurred 5,879 7,432 14,990 22,015 Ceding commissions (2) 12,500 12,137 36,751 35,659 Profit commission 31,621 28,981 95,063 84,963 (1) Under our QSR Transactions, premiums are ceded on an earned and received basis as defined in the agreements. (2) Ceding commissions are reported within Other underwriting and operating expenses, net on the consolidated statements of operations.

Earnings per Share (Tables)

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Calculation of earnings (loss) per share	The following table reconciles the numerators and denominators used to calculate basic and diluted EPS. Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2017 2016 2017 2016 Basic earnings per share: Net income $ 120,027 $ 56,618 $ 328,447 $ 235,030 Weighted average common shares outstanding - basic 370,586 349,376 359,613 343,403 Basic earnings per share $ 0.32 $ 0.16 $ 0.91 $ 0.68 Diluted earnings per share: Net income $ 120,027 $ 56,618 $ 328,447 $ 235,030 Interest expense, net of tax (1) : 2% Notes — 1,324 907 5,288 5% Notes — 673 1,709 5,080 9% Debentures 3,757 — 11,270 — Diluted income available to common shareholders $ 123,784 $ 58,615 $ 342,333 $ 245,398 Weighted average common shares outstanding - basic 370,586 349,376 359,613 343,403 Effect of dilutive securities: Unvested RSUs 1,473 1,395 1,367 1,428 2% Notes — 44,488 11,119 62,707 5% Notes — 10,791 4,743 13,885 9% Debentures 19,028 — 19,028 — Weighted average common shares outstanding - diluted 391,087 406,050 395,870 421,423 Diluted earnings per share $ 0.32 $ 0.14 $ 0.86 $ 0.58 Antidilutive securities (in millions) — 19.0 — 20.4 (1) Tax effected at a rate of 35%.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2017
Investments [Abstract]
Amortized cost, gross unrealized gains and losses and fair value of investments portfolio	The amortized cost, gross unrealized gains and losses and fair value of the investment portfolio at September 30, 2017 and December 31, 2016 are shown below. September 30, 2017 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses (1) Fair Value U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 104,168 $ 331 $ (799 ) $ 103,700 Obligations of U.S. states and political subdivisions 2,069,592 50,505 (6,814 ) 2,113,283 Corporate debt securities 1,865,640 16,151 (6,536 ) 1,875,255 ABS 9,857 3 — 9,860 RMBS 198,756 113 (5,973 ) 192,896 CMBS 308,735 1,517 (4,827 ) 305,425 CLOs 109,417 446 (129 ) 109,734 Total debt securities 4,666,165 69,066 (25,078 ) 4,710,153 Equity securities 7,202 50 (13 ) 7,239 Total investment portfolio $ 4,673,367 $ 69,116 $ (25,091 ) $ 4,717,392 December 31, 2016 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses (1) Fair Value U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 73,847 $ 407 $ (724 ) $ 73,530 Obligations of U.S. states and political subdivisions 2,147,458 20,983 (25,425 ) 2,143,016 Corporate debt securities 1,756,461 6,059 (18,610 ) 1,743,910 ABS 59,519 74 (28 ) 59,565 RMBS 231,733 102 (7,626 ) 224,209 CMBS 327,042 769 (7,994 ) 319,817 CLOs 121,151 226 (202 ) 121,175 Total debt securities 4,717,211 28,620 (60,609 ) 4,685,222 Equity securities 7,144 8 (24 ) 7,128 Total investment portfolio $ 4,724,355 $ 28,628 $ (60,633 ) $ 4,692,350 (1) At September 30, 2017 and December 31, 2016 , there were no other-than-temporary impairment losses recorded in other comprehensive income.
Amortized cost and fair values of debt securities by contractual maturity	The amortized cost and fair values of debt securities at September 30, 2017 , by contractual maturity, are shown in the following table. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Because most asset-backed and mortgage-backed securities and collateralized loan obligations provide for periodic payments throughout their lives, they are listed in separate categories. September 30, 2017 (In thousands) Amortized Cost Fair Value Due in one year or less $ 439,771 $ 440,227 Due after one year through five years 1,333,112 1,342,110 Due after five years through ten years 972,932 980,813 Due after ten years 1,293,585 1,329,088 $ 4,039,400 $ 4,092,238 ABS 9,857 9,860 RMBS 198,756 192,896 CMBS 308,735 305,425 CLOs 109,417 109,734 Total as of September 30, 2017 $ 4,666,165 $ 4,710,153
Aging of the fair values of securities in an unrealized loss position	For those securities in an unrealized loss position, the length of time the securities were in such a position, as measured by their month-end fair values, is as follows: September 30, 2017 Less Than 12 Months 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 74,136 $ (524 ) $ 22,423 $ (275 ) $ 96,559 $ (799 ) Obligations of U.S. states and political subdivisions 411,460 (4,520 ) 85,700 (2,294 ) 497,160 (6,814 ) Corporate debt securities 434,056 (4,367 ) 75,592 (2,169 ) 509,648 (6,536 ) ABS 2,613 — — — 2,613 — RMBS 37,676 (713 ) 148,748 (5,260 ) 186,424 (5,973 ) CMBS 126,709 (2,375 ) 57,189 (2,452 ) 183,898 (4,827 ) CLOs 7,276 (129 ) — — 7,276 (129 ) Equity securities 381 (5 ) 171 (8 ) 552 (13 ) Total $ 1,094,307 $ (12,633 ) $ 389,823 $ (12,458 ) $ 1,484,130 $ (25,091 ) December 31, 2016 Less Than 12 Months 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 48,642 $ (724 ) $ — $ — $ 48,642 $ (724 ) Obligations of U.S. states and political subdivisions 1,136,676 (24,918 ) 13,681 (507 ) 1,150,357 (25,425 ) Corporate debt securities 915,777 (16,771 ) 35,769 (1,839 ) 951,546 (18,610 ) ABS 3,366 (28 ) 656 — 4,022 (28 ) RMBS 46,493 (857 ) 171,326 (6,769 ) 217,819 (7,626 ) CMBS 205,545 (7,529 ) 38,587 (465 ) 244,132 (7,994 ) CLOs 13,278 (73 ) 34,760 (129 ) 48,038 (202 ) Equity securities 568 (15 ) 137 (9 ) 705 (24 ) Total $ 2,370,345 $ (50,915 ) $ 294,916 $ (9,718 ) $ 2,665,261 $ (60,633 )
Net realized investment gains (losses) and OTTI on investments	The net realized investment gains (losses) on the investment portfolio were as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Fixed maturities $ (50 ) $ 1,511 $ (227 ) $ 5,397 Equity securities 3 3,581 16 3,587 Net realized investments (losses) gains $ (47 ) $ 5,092 $ (211 ) $ 8,984 Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Gains on sales $ 32 $ 6,168 $ 861 $ 11,677 Losses on sales (79 ) (1,076 ) (1,072 ) (2,693 ) Net realized investments (losses) gains $ (47 ) $ 5,092 $ (211 ) $ 8,984

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair value measurements for items measured at fair value	Fair value measurements for assets measured at fair value included the following as of September 30, 2017 and December 31, 2016 : September 30, 2017 (In thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 103,700 $ 13,312 $ 90,388 $ — Obligations of U.S. states and political subdivisions 2,113,283 — 2,112,903 380 Corporate debt securities 1,875,255 — 1,875,255 — ABS 9,860 — 9,860 — RMBS 192,896 — 192,896 — CMBS 305,425 — 305,425 — CLOs 109,734 — 109,734 — Total debt securities 4,710,153 13,312 4,696,461 380 Equity securities (1) 7,239 2,971 — 4,268 Total investment portfolio $ 4,717,392 $ 16,283 $ 4,696,461 $ 4,648 Real estate acquired (2) $ 11,728 $ — $ — $ 11,728 (1) Equity securities in Level 3 are carried at cost, which approximates fair value. (2) Real estate acquired through claim settlement, which is held for sale, is reported in Other assets on the consolidated balance sheets. December 31, 2016 (In thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 73,530 $ 30,690 $ 42,840 $ — Obligations of U.S. states and political subdivisions 2,143,016 — 2,142,325 691 Corporate debt securities 1,743,910 — 1,743,910 — ABS 59,565 — 59,565 — RMBS 224,209 — 224,209 — CMBS 319,817 — 319,817 — CLOs 121,175 — 121,175 — Total debt securities 4,685,222 30,690 4,653,841 691 Equity securities (1) 7,128 2,860 — 4,268 Total investment portfolio $ 4,692,350 $ 33,550 $ 4,653,841 $ 4,959 Real estate acquired (2) $ 11,748 $ — $ — $ 11,748 (1) Equity securities in Level 3 are carried at cost, which approximates fair value. (2) Real estate acquired through claim settlement, which is held for sale, is reported in Other assets on the consolidated balance sheets.
Reconciliation of beginning and ending balance for assets and liabilities measured at fair value with significant unobservable inputs (level 3)	For assets measured at fair value using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances for the three and nine months ended September 30, 2017 and 2016 is shown in the following tables. There were no transfers into or out of Level 3 in those periods and there were no losses included in earnings for those periods attributable to the change in unrealized losses on assets still held at the end of the applicable period. Three Months Ended September 30, 2017 (In thousands) Debt Securities Equity Securities Total Investments Real Estate Acquired Balance at June 30, 2017 $ 577 $ 4,268 $ 4,845 $ 10,271 Total realized/unrealized gains (losses): Included in earnings and reported as losses incurred, net — — — (592 ) Purchases — — — 8,881 Sales (197 ) — (197 ) (6,832 ) Balance at September 30, 2017 $ 380 $ 4,268 $ 4,648 $ 11,728 Three Months Ended September 30, 2016 (In thousands) Debt Equity Total Real Estate Balance at June 30, 2016 $ 1,056 $ 6,940 $ 7,996 $ 9,642 Total realized/unrealized gains (losses): Included in other comprehensive income — (3,519 ) (3,519 ) — Included in earnings and reported as net realized investment gains — 3,579 3,579 — Included in earnings and reported as losses incurred, net — — — (501 ) Purchases — 1,167 1,167 8,938 Sales (226 ) (3,899 ) (4,125 ) (7,515 ) Balance at September 30, 2016 $ 830 $ 4,268 $ 5,098 $ 10,564 Nine Months Ended September 30, 2017 (In thousands) Debt Securities Equity Securities Total Investments Real Estate Acquired Balance at December 31, 2016 $ 691 $ 4,268 $ 4,959 $ 11,748 Total realized/unrealized gains (losses): Included in earnings and reported as losses incurred, net — — — (818 ) Purchases — — — 26,985 Sales (311 ) — (311 ) (26,187 ) Balance at September 30, 2017 $ 380 $ 4,268 $ 4,648 $ 11,728 Nine Months Ended September 30, 2016 (In thousands) Debt Equity Total Real Estate Balance at December 31, 2015 $ 1,228 $ 2,855 $ 4,083 $ 12,149 Total realized/unrealized gains (losses): Included in earnings and reported as net realized investment gains — 3,579 3,579 — Included in earnings and reported as losses incurred, net — — — (143 ) Purchases — 4,258 4,258 27,953 Sales (398 ) (6,424 ) (6,822 ) (29,395 ) Balance at September 30, 2016 $ 830 $ 4,268 $ 5,098 $ 10,564
Carrying value and fair value of debt	The following table presents the carrying value and fair value of our financial liabilities disclosed, but not carried, at fair value at September 30, 2017 and December 31, 2016 . The fair values of our 5% Notes, 2% Notes, 5.75% Notes, and 9% Debentures were based on observable market prices. The fair value of the FHLB Advance was estimated using discounted cash flows on current incremental borrowing rates for similar borrowing arrangements. In all cases the fair values of the financial liabilities below are categorized as Level 2. September 30, 2017 December 31, 2016 (In thousands) Carrying Value Fair Value Carrying Value Fair Value FHLB Advance 155,000 154,175 $ 155,000 $ 151,905 5% Notes — — 144,789 147,679 2% Notes — — 204,672 308,605 5.75% Notes 418,271 468,248 417,406 445,987 9% Debentures 256,872 349,798 256,872 323,040 Total financial liabilities $ 830,143 $ 972,221 $ 1,178,739 $ 1,377,216

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other comprehensive income	The pretax and related income tax (expense) benefit components of our other comprehensive income (loss) for the three and nine months ended September 30, 2017 and 2016 are included in the following table. Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Net unrealized investment gains (losses) arising during the period $ 17,761 $ (22,206 ) $ 76,022 $ 142,852 Income tax (expense) benefit (6,217 ) 7,772 (26,608 ) (50,121 ) Net of taxes 11,544 (14,434 ) 49,414 92,731 Net changes in benefit plan assets and obligations (226 ) (370 ) (680 ) (1,110 ) Income tax benefit 79 129 238 388 Net of taxes (147 ) (241 ) (442 ) (722 ) Net changes in unrealized foreign currency translation adjustment — (16 ) 45 (1,496 ) Income tax benefit (expense) — 6 (14 ) 522 Net of taxes — (10 ) 31 (974 ) Total other comprehensive income (loss) 17,535 (22,592 ) 75,387 140,246 Total income tax (expense) benefit (6,138 ) 7,907 (26,384 ) (49,211 ) Total other comprehensive income (loss), net of tax $ 11,397 $ (14,685 ) $ 49,003 $ 91,035
Reclassification out of accumulated other comprehensive income	The pretax and related income tax benefit (expense) components of the amounts reclassified from our accumulated other comprehensive loss (“AOCL”) to our consolidated statements of operations for the three and nine months ended September 30, 2017 and 2016 are included in the following table. Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2017 2016 2017 2016 Reclassification adjustment for net realized (losses) gains (1) $ (427 ) $ 5,248 $ (2,566 ) $ 5,958 Income tax benefit (expense) 150 (1,837 ) 898 (1,963 ) Net of taxes (277 ) 3,411 (1,668 ) 3,995 Reclassification adjustment related to benefit plan assets and obligations (2) 226 370 680 1,110 Income tax (expense) (79 ) (129 ) (238 ) (388 ) Net of taxes 147 241 442 722 Reclassification adjustment related to foreign currency (3) — — — 1,467 Income tax (expense) — — — (513 ) Net of taxes — — — 954 Total reclassifications (201 ) 5,618 (1,886 ) 8,535 Total income tax benefit (expense) 71 (1,966 ) 660 (2,864 ) Total reclassifications, net of tax $ (130 ) $ 3,652 $ (1,226 ) $ 5,671 (1) Increases (decreases) Net realized investment (losses) gains on the consolidated statements of operations. (2) Decreases (increases) Other underwriting and operating expenses, net on the consolidated statements of operations. (3) Increases (decreases) Other revenue on the consolidated statements of operations.
Accumulated other comprehensive income (loss)	A rollforward of AOCL for the nine months ended September 30, 2017 , including amounts reclassified from AOCL, are included in the table below. Nine Months Ended September 30, 2017 (In thousands) Net unrealized gains and losses on available-for-sale securities Net benefit plan assets and obligations recognized in shareholders' equity Net unrealized foreign currency translation Total AOCL Balance, December 31, 2016, net of tax $ (20,797 ) $ (54,272 ) $ (31 ) $ (75,100 ) Other comprehensive income before reclassifications 47,746 — 31 47,777 Less: Amounts reclassified from AOCL (1,668 ) 442 — (1,226 ) Balance, September 30, 2017, net of tax $ 28,617 $ (54,714 ) $ — $ (26,097 )

Benefit Plans (Tables)

Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2017
Retirement Benefits [Abstract]
Components of net periodic benefit cost	The following tables provide the components of net periodic benefit cost for our pension, supplemental executive retirement and other postretirement benefit plans for the three and nine months ended September 30, 2017 and 2016 : Three Months Ended September 30, Pension and Supplemental Executive Retirement Plans Other Postretirement Benefit Plans (In thousands) 2017 2016 2017 2016 Service cost $ 2,389 $ 2,283 $ 203 $ 188 Interest cost 3,869 3,976 176 176 Expected return on plan assets (5,025 ) (4,877 ) (1,312 ) (1,222 ) Recognized net actuarial loss 1,543 1,464 — — Amortization of prior service cost (107 ) (172 ) (1,662 ) (1,662 ) Net periodic benefit cost (benefit) $ 2,669 $ 2,674 $ (2,595 ) $ (2,520 ) Nine Months Ended September 30, Pension and Supplemental Executive Retirement Plans Other Postretirement Benefit Plans (In thousands) 2017 2016 2017 2016 Service cost $ 7,167 $ 6,848 $ 610 $ 564 Interest cost 11,606 11,929 529 528 Expected return on plan assets (15,074 ) (14,631 ) (3,936 ) (3,665 ) Recognized net actuarial loss 4,627 4,392 — — Amortization of prior service cost (320 ) (515 ) (4,987 ) (4,987 ) Net periodic benefit cost (benefit) $ 8,006 $ 8,023 $ (7,784 ) $ (7,560 )

Loss Reserves (Tables)

Loss Reserves (Tables)	9 Months Ended
	Sep. 30, 2017
Insurance Loss Reserves [Abstract]
Reconciliation of beginning and ending loss reserves	The following table provides a reconciliation of beginning and ending loss reserves as of and for the nine months ended September 30, 2017 and 2016 : Nine months ended September 30, (In thousands) 2017 2016 Reserve at beginning of period $ 1,438,813 $ 1,893,402 Less reinsurance recoverable 50,493 44,487 Net reserve at beginning of period 1,388,320 1,848,915 Losses incurred: Losses and LAE incurred in respect of default notices received in: Current year 219,485 292,090 Prior years (1) (134,780 ) (99,591 ) Total losses incurred 84,705 192,499 Losses paid: Losses and LAE paid in respect of default notices received in: Current year 5,474 5,942 Prior years 407,977 549,706 Reinsurance terminations (2) 301 (2,854 ) Total losses paid 413,752 552,794 Net reserve at end of period 1,059,273 1,488,620 Plus reinsurance recoverables 45,878 46,863 Reserve at end of period $ 1,105,151 $ 1,535,483 (1) A negative number for prior year losses incurred indicates a redundancy of prior year loss reserves. See the following table for more information about prior year loss development. (2) In a termination, the reinsurance agreement is cancelled, with no future premium ceded and amounts for any incurred but unpaid losses paid to us. Amounts paid to (received from) reinsurers result in an increase (decrease) in net losses paid. The change in net losses paid on our losses incurred is offset by a corresponding change in the reinsurance recoverable, resulting in no net impact on losses incurred.
Prior year development of the reserves	The prior year development of the reserves in the first nine months of 2017 and 2016 is reflected in the following table. Nine months ended September 30, (In millions) 2017 2016 Decrease in estimated claim rate on primary defaults $ (138 ) $ (108 ) (Decrease) increase in estimated severity on primary defaults (2 ) 12 Change in estimates related to pool reserves, LAE reserves and reinsurance 5 (4 ) Total prior year loss development (1) $ (135 ) $ (100 ) (1) A negative number for prior year loss development indicates a redundancy of prior year loss reserves.
Rollforward of primary default inventory	A rollforward of our primary default inventory for the three and nine months ended September 30, 2017 and 2016 appears in the following table. The information concerning new notices and cures is compiled from monthly reports received from loan servicers. The level of new notice and cure activity reported in a particular month can be influenced by, among other things, the date on which a servicer generates its report, the accuracy of the data provided by servicers, the number of business days in a month, transfers of servicing between loan servicers and whether all servicers have provided the reports in a given month. Three months ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Default inventory at beginning of period 41,317 52,558 50,282 62,633 New notices 15,950 17,607 45,352 50,418 Cures (13,546 ) (15,556 ) (45,382 ) (50,249 ) Paids (including those charged to a deductible or captive) (2,195 ) (3,051 ) (7,403 ) (9,619 ) Rescissions and denials (82 ) (125 ) (277 ) (477 ) Other items removed from inventory (209 ) — (1,337 ) (1,273 ) Default inventory at end of period 41,235 51,433 41,235 51,433
Primary default inventory detail of new notices received	As shown in the table below, we received an increased number of new default notices in October 2017 compared to October 2016 related to loans in locations that the Federal Emergency Management Agency has declared Individual Assistance Disaster Areas (“IADA”) in connection with recent hurricane activity primarily impacting Texas, Florida, and Puerto Rico. For the month ended October 31, 2017 2016 Default notices for loans in IADAs 3,394 637 Other default notices 4,549 4,882 Total default notices 7,943 5,519
Aging of the primary default inventory	The number of consecutive months a borrower is delinquent is shown in the following table. Consecutive months in default September 30, 2017 December 31, 2016 September 30, 2016 3 months or less 11,331 27 % 12,194 24 % 12,333 24 % 4-11 months 11,092 27 % 13,450 27 % 12,648 25 % 12 months or more (1) (2) 18,812 46 % 24,638 49 % 26,452 51 % Total primary default inventory 41,235 100 % 50,282 100 % 51,433 100 % Primary claims received inventory included in ending default inventory: 1,063 3 % 1,385 3 % 1,636 3 % (1) Approximately 45% , 47% , and 48% of the primary default inventory in default for 12 consecutive months or more has been in default for at least 36 consecutive months as of September 30, 2017 , December 31, 2016 , and September 30, 2016 , respectively. (2) The majority of items removed from our default inventory were due to commutations of NPLs during the nine months ended September 30, 2017 were in default for 12 consecutive months or more as of December 31, 2016.
Number of payments delinquent	The number of payments that a borrower is delinquent is shown in the following table. Number of payments delinquent September 30, 2017 December 31, 2016 September 30, 2016 3 payments or less 16,916 41 % 18,419 36 % 18,374 36 % 4-11 payments 10,583 26 % 12,892 26 % 12,282 24 % 12 payments or more (1) 13,736 33 % 18,971 38 % 20,777 40 % Total primary default inventory 41,235 100 % 50,282 100 % 51,433 100 % (1) The majority of items removed from our default inventory were due to commutations of NPLs during the nine months ended September 30, 2017 had 12 or more payments delinquent as of December 31, 2016.

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of stock-based compensation, activity	The number of shares granted to employees and the weighted average fair value per share during the periods presented were (shares in thousands): Nine months ended September 30, 2017 2016 Shares Granted Weighted Average Share Fair Value Shares Granted Weighted Average Share Fair Value RSUs subject to performance conditions 1,237 $ 10.41 1,257 $ 5.66 RSUs subject only to service conditions 395 10.41 433 5.67

New Accounting Pronouncements33

New Accounting Pronouncements (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Discrete tax benefits realized upon adoption of ASU	$ 1.5

Debt - Narrative (Details)

Debt - Narrative (Details) shares in Millions	May 01, 2017USD ($)	Apr. 30, 2017USD ($)shares	Aug. 31, 2016USD ($)	Feb. 29, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)shares	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)shares	Mar. 31, 2017USD ($)	Mar. 21, 2017USD ($)
Debt Instrument [Line Items]
Loss on debt extinguishment					$ 0	$ 75,223,000	$ 65,000	$ 90,531,000
Repayments of convertible debt							$ 145,620,000	363,778,000
2% Notes
Debt Instrument [Line Items]
Stated interest rate (in hundredths)					2.00%		2.00%
Principal amount of notes converted into shares		$ 202,500,000
Principal amount of notes redeemed for cash		$ 5,100,000
Conversion rate (in shares per $1,000 note)		0.1438332
Loss on debt extinguishment		$ 70,000
Convertible Senior Notes
Debt Instrument [Line Items]
Stated interest rate (in hundredths)					5.00%		5.00%
Repayments of convertible debt	$ 145,000,000							195,500,000
Extinguishment of debt, amount								$ 188,500,000
Reduction in shares for computation of earnings per share | shares								14
Convertible Senior Notes | 2% Convertible Senior Notes
Debt Instrument [Line Items]
Shares issued during period upon conversion of convertible debt (in shares) | shares		29.1
Repayments of convertible debt						230,700,000
Extinguishment of debt, amount						292,400,000
Repayments of debt, aggregate purchase price						$ 362,100,000
Shares issued for repayment of debt (in shares) | shares						18.3
Reduction in shares for computation of earnings per share | shares						42.1
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity										$ 175,000,000
Revolving credit facility									$ 150,000,000
Senior Notes | 5.75% Notes
Debt Instrument [Line Items]
Stated interest rate (in hundredths)			5.75%		5.75%		5.75%
Aggregate Principal Amount			$ 425,000,000
Net proceeds from issuance of debt			418,100,000
Other expenses associated with the issuance of notes			$ 1,200,000
9% Debentures
Debt Instrument [Line Items]
Stated interest rate (in hundredths)					9.00%		9.00%
Conversion rate (in shares per $1,000 note)							0.0740741
Loss on debt extinguishment				$ 8,300,000
Repayments of convertible debt				150,700,000
Extinguishment of debt, amount				$ 132,700,000
Reduction in shares for computation of earnings per share | shares								9.8
Reacquisition of convertible junior subordinated debentures-equity component								$ 6,300,000

Debt - Summary of Debt Obligati

Debt - Summary of Debt Obligations (Details) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Apr. 30, 2017	Sep. 30, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)	Aug. 31, 2016
Debt Instrument [Line Items]
Long-term debt, par value		$ 836.9	$ 1,189.5
Debt issuance costs		(6.8)	(10.8)
Long-term debt, carrying value		830.1	1,178.7
FHLB Advance
Debt Instrument [Line Items]
Long-term debt, par value		155	155
5% Convertible Senior Notes due 2017
Debt Instrument [Line Items]
Long-term debt, par value		$ 0	145
Stated interest rate (in hundredths)		5.00%
2% Notes
Debt Instrument [Line Items]
Long-term debt, par value		$ 0	207.6
Stated interest rate (in hundredths)		2.00%
Conversion rate (in shares per $1,000 note)	0.1438332
5.75% Notes | 5.75% Notes
Debt Instrument [Line Items]
Long-term debt, par value		$ 425	425
Stated interest rate (in hundredths)		5.75%		5.75%
9% Debentures
Debt Instrument [Line Items]
Long-term debt, par value		$ 256.9	$ 256.9
Stated interest rate (in hundredths)		9.00%
Conversion rate (in shares per $1,000 note)		0.0740741
Convertible debt, conversion price (in dollars per share) | $ / shares		$ 13.50
Period preceding election to convert (in days)		5 days

Debt - Summary of Interest Paid

Debt - Summary of Interest Paid (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Aug. 31, 2016
Debt Instrument [Line Items]
Total interest payments	$ 45.1	$ 31.5
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Total interest payments	0.5	0
FHLB Advance
Debt Instrument [Line Items]
Total interest payments	2.2	1.7
5% Convertible Senior Notes due 2017
Debt Instrument [Line Items]
Total interest payments	$ 3.6	6.9
Stated interest rate (in hundredths)	5.00%
2% Notes
Debt Instrument [Line Items]
Total interest payments	$ 2.1	7
Stated interest rate (in hundredths)	2.00%
5.75% Notes | 5.75% Notes
Debt Instrument [Line Items]
Total interest payments	$ 25.1	0
Stated interest rate (in hundredths)	5.75%		5.75%
9% Debentures
Debt Instrument [Line Items]
Total interest payments	$ 11.6	$ 15.9
Stated interest rate (in hundredths)	9.00%

Reinsurance - Summary of Premiu

Reinsurance - Summary of Premiums Earned and Losses Incurred (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Premiums earned:
Direct	$ 268,709	$ 270,718	$ 789,317	$ 789,671
Assumed	312	152	472	542
Ceded	(31,938)	(33,494)	(92,467)	(100,040)
Net premiums earned	237,083	237,376	697,322	690,173
Losses incurred:
Direct	35,313	69,579	99,122	216,874
Assumed	(97)	241	69	681
Ceded	(5,469)	(8,923)	(14,486)	(25,056)
Losses incurred, net	$ 29,747	$ 60,897	$ 84,705	$ 192,499

Reinsurance - Narrative (Detail

Reinsurance - Narrative (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Effects of Reinsurance [Line Items]
Reinsurance recoverable on loss reserves	$ 45,878,000	$ 50,493,000	$ 46,863,000	$ 44,487,000
Period of existing captive reinsurance agreement	10 years
Fair value of trust fund assets under captive agreements	$ 80,000,000	91,000,000
Quota Share Reinsurance Agreement, 2017
Effects of Reinsurance [Line Items]
Contingent termination fee	$ 0
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent)	90.00%
Quota share for all policies covered (as a percent)	30.00%
Ceding commission, percentage (as a percent)	20.00%
Loss ratio threshold for profit commissions (as a percent)	60.00%
Quota Share Reinsurance Agreement, 2015
Effects of Reinsurance [Line Items]
Contingent termination fee	$ 0
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent)	90.00%
Quota share for all policies covered (as a percent)	30.00%
Ceding commission, percentage (as a percent)	20.00%
Loss ratio threshold for profit commissions (as a percent)	60.00%
Quota Share Reinsurance Agreements, Excluding Captive Agreements
Effects of Reinsurance [Line Items]
Reinsurance recoverable on loss reserves	$ 35,300,000	31,800,000
Reinsurance Agreements, Captive Agreements
Effects of Reinsurance [Line Items]
Reinsurance recoverable on loss reserves related to captive agreements	$ 11,000,000	$ 19,000,000

Reinsurance - Summary of Quota

Reinsurance - Summary of Quota Reinsurance Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Effects of Reinsurance [Line Items]
Ceded losses incurred	$ 5,469	$ 8,923	$ 14,486	$ 25,056
Quota Share Reinsurance Agreements, Excluding Captive Agreements
Effects of Reinsurance [Line Items]
Ceded premiums written and earned, net of profit commission	30,880	31,707	88,692	93,334
Ceded losses incurred	5,879	7,432	14,990	22,015
Ceding commissions	12,500	12,137	36,751	35,659
Profit commission	$ 31,621	$ 28,981	$ 95,063	$ 84,963

Litigation and Contingencies (D

Litigation and Contingencies (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Average paid claim reduction due to curtailments (as a percent)	5.50%	5.50%
Maximum exposure associated with other discussions and legal proceedings	$ 289

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic earnings per share:
Net income	$ 120,027	$ 56,618	$ 328,447	$ 235,030
Weighted average common shares outstanding - basic (in shares)	370,586	349,376	359,613	343,403
Basic earnings per share (in dollars per share)	$ 0.32	$ 0.16	$ 0.91	$ 0.68
Diluted earnings per share:
Net income	$ 120,027	$ 56,618	$ 328,447	$ 235,030
Diluted income available to common shareholders	$ 123,784	$ 58,615	$ 342,333	$ 245,398
Weighted average common shares outstanding - basic (in shares)	370,586	349,376	359,613	343,403
Effect of dilutive securities:
Weighted average common shares outstanding - diluted (in shares)	391,087	406,050	395,870	421,423
Diluted earnings per share (in dollars per share)	$ 0.32	$ 0.14	$ 0.86	$ 0.58
Antidilutive securities (in shares)	0	19,000	0	20,400
Effective income tax rate (in hundredths)	35.00%	35.00%	35.00%	35.00%
Unvested RSUs
Effect of dilutive securities:
Unvested RSUs (in shares)	1,473	1,395	1,367	1,428
2% Notes
Diluted earnings per share:
Dilutive securities	$ 0	$ 1,324	$ 907	$ 5,288
Effect of dilutive securities:
Dilutive securities (in shares)	0	44,488	11,119	62,707
Stated interest rate (in hundredths)	2.00%		2.00%
5% Notes
Diluted earnings per share:
Dilutive securities	$ 0	$ 673	$ 1,709	$ 5,080
Effect of dilutive securities:
Dilutive securities (in shares)	0	10,791	4,743	13,885
Stated interest rate (in hundredths)	5.00%		5.00%
9% Debentures
Diluted earnings per share:
Dilutive securities	$ 3,757	$ 0	$ 11,270	$ 0
Effect of dilutive securities:
Dilutive securities (in shares)	19,028	0	19,028	0
Stated interest rate (in hundredths)	9.00%		9.00%

Investments (Details)

Investments (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017USD ($)security	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)security	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)security
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 4,673,367,000		$ 4,673,367,000		$ 4,724,355,000
Gross Unrealized Gains	69,116,000		69,116,000		28,628,000
Gross Unrealized Losses	(25,091,000)		(25,091,000)		(60,633,000)
Fair Value	4,717,392,000		4,717,392,000		4,692,350,000
Other than Temporary Impairment Losses, Portion in Other Comprehensive Income			$ 0		0
Federal Home Loan Bank advances, collateral, value of principal, percent (as a percent)			102.00%
FHLB advance collateral	167,200,000		$ 167,200,000
Gross accumulated unrealized gain (losses) on available-for-sale securities	$ (25,100,000)		$ (25,100,000)		$ (60,600,000)
Number of securities in unrealized loss position (in securities) | security	343		343		607
Net impairment losses recognized in earnings	$ 0	$ 0	$ 0	$ 0
Total debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,666,165,000		4,666,165,000		$ 4,717,211,000
Gross Unrealized Gains	69,066,000		69,066,000		28,620,000
Gross Unrealized Losses	(25,078,000)		(25,078,000)		(60,609,000)
Fair Value	4,710,153,000		4,710,153,000		4,685,222,000
U.S. Treasury securities and obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	104,168,000		104,168,000		73,847,000
Gross Unrealized Gains	331,000		331,000		407,000
Gross Unrealized Losses	(799,000)		(799,000)		(724,000)
Fair Value	103,700,000		103,700,000		73,530,000
Obligations of U.S. states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,069,592,000		2,069,592,000		2,147,458,000
Gross Unrealized Gains	50,505,000		50,505,000		20,983,000
Gross Unrealized Losses	(6,814,000)		(6,814,000)		(25,425,000)
Fair Value	2,113,283,000		2,113,283,000		2,143,016,000
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,865,640,000		1,865,640,000		1,756,461,000
Gross Unrealized Gains	16,151,000		16,151,000		6,059,000
Gross Unrealized Losses	(6,536,000)		(6,536,000)		(18,610,000)
Fair Value	1,875,255,000		1,875,255,000		1,743,910,000
ABS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,857,000		9,857,000		59,519,000
Gross Unrealized Gains	3,000		3,000		74,000
Gross Unrealized Losses	0		0		(28,000)
Fair Value	9,860,000		9,860,000		59,565,000
RMBS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	198,756,000		198,756,000		231,733,000
Gross Unrealized Gains	113,000		113,000		102,000
Gross Unrealized Losses	(5,973,000)		(5,973,000)		(7,626,000)
Fair Value	192,896,000		192,896,000		224,209,000
CMBS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	308,735,000		308,735,000		327,042,000
Gross Unrealized Gains	1,517,000		1,517,000		769,000
Gross Unrealized Losses	(4,827,000)		(4,827,000)		(7,994,000)
Fair Value	305,425,000		305,425,000		319,817,000
CLOs
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	109,417,000		109,417,000		121,151,000
Gross Unrealized Gains	446,000		446,000		226,000
Gross Unrealized Losses	(129,000)		(129,000)		(202,000)
Fair Value	109,734,000		109,734,000		121,175,000
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,202,000		7,202,000		7,144,000
Gross Unrealized Gains	50,000		50,000		8,000
Gross Unrealized Losses	(13,000)		(13,000)		(24,000)
Fair Value	$ 7,239,000		$ 7,239,000		$ 7,128,000

Investments - Amortized Cost an

Investments - Amortized Cost and Fair Values of Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less	$ 439,771
Due after one year through five years	1,333,112
Due after five years through ten years	972,932
Due after ten years	1,293,585
Total debt securities with single maturity date, amortized cost	4,039,400
Total at end of period	4,666,165	$ 4,717,211
Fair Value
Due in one year or less	440,227
Due after one year through five years	1,342,110
Due after five years through ten years	980,813
Due after ten years	1,329,088
Total debt securities with single maturity date, fair value	4,092,238
Total at end of period	4,710,153	$ 4,685,222
ABS
Amortized Cost
Total debt securities without single maturity date, amortized cost	9,857
Fair Value
Total debt securities without single maturity date, fair value	9,860
RMBS
Amortized Cost
Total debt securities without single maturity date, amortized cost	198,756
Fair Value
Total debt securities without single maturity date, fair value	192,896
CMBS
Amortized Cost
Total debt securities without single maturity date, amortized cost	308,735
Fair Value
Total debt securities without single maturity date, fair value	305,425
CLOs
Amortized Cost
Total debt securities without single maturity date, amortized cost	109,417
Fair Value
Total debt securities without single maturity date, fair value	$ 109,734

Investments - Securities In Unr

Investments - Securities In Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	$ 1,094,307	$ 2,370,345
12 months or greater	389,823	294,916
Total investment portfolio	1,484,130	2,665,261
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(12,633)	(50,915)
12 months or greater	(12,458)	(9,718)
Total investment portfolio	(25,091)	(60,633)
U.S. Treasury securities and obligations of U.S. government corporations and agencies
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	74,136	48,642
12 months or greater	22,423	0
Total investment portfolio	96,559	48,642
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(524)	(724)
12 months or greater	(275)	0
Total investment portfolio	(799)	(724)
Obligations of U.S. states and political subdivisions
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	411,460	1,136,676
12 months or greater	85,700	13,681
Total investment portfolio	497,160	1,150,357
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(4,520)	(24,918)
12 months or greater	(2,294)	(507)
Total investment portfolio	(6,814)	(25,425)
Corporate debt securities
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	434,056	915,777
12 months or greater	75,592	35,769
Total investment portfolio	509,648	951,546
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(4,367)	(16,771)
12 months or greater	(2,169)	(1,839)
Total investment portfolio	(6,536)	(18,610)
ABS
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	2,613	3,366
12 months or greater	0	656
Total investment portfolio	2,613	4,022
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	0	(28)
12 months or greater	0	0
Total investment portfolio	0	(28)
RMBS
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	37,676	46,493
12 months or greater	148,748	171,326
Total investment portfolio	186,424	217,819
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(713)	(857)
12 months or greater	(5,260)	(6,769)
Total investment portfolio	(5,973)	(7,626)
CMBS
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	126,709	205,545
12 months or greater	57,189	38,587
Total investment portfolio	183,898	244,132
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(2,375)	(7,529)
12 months or greater	(2,452)	(465)
Total investment portfolio	(4,827)	(7,994)
CLOs
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	7,276	13,278
12 months or greater	0	34,760
Total investment portfolio	7,276	48,038
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(129)	(73)
12 months or greater	0	(129)
Total investment portfolio	(129)	(202)
Equity securities
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less than 12 months	381	568
12 months or greater	171	137
Total investment portfolio	552	705
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less than 12 months	(5)	(15)
12 months or greater	(8)	(9)
Total investment portfolio	$ (13)	$ (24)

Investments - Gain (Loss) on In

Investments - Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses) on investments	$ (47)	$ 5,092	$ (211)	$ 8,984
Realized investment gains (losses) on investments:
Gains on sales	32	6,168	861	11,677
Losses on sales	(79)	(1,076)	(1,072)	(2,693)
Net realized investment (losses) gains	(47)	5,092	(211)	8,984
Fixed maturities
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses) on investments	(50)	1,511	(227)	5,397
Realized investment gains (losses) on investments:
Net realized investment (losses) gains	(50)	1,511	(227)	5,397
Equity securities
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses) on investments	3	3,581	16	3,587
Realized investment gains (losses) on investments:
Net realized investment (losses) gains	$ 3	$ 3,581	$ 16	$ 3,587

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$ 103,700	$ 73,530
Obligations of U.S. states and political subdivisions	2,113,283	2,143,016
Corporate debt securities	1,875,255	1,743,910
ABS	9,860	59,565
RMBS	192,896	224,209
CMBS	305,425	319,817
CLOs	109,734	121,175
Total debt securities	4,710,153	4,685,222
Equity securities	7,239	7,128
Total investment portfolio	4,717,392	4,692,350
Real estate acquired	11,728	11,748
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities and obligations of U.S. government corporations and agencies	13,312	30,690
Obligations of U.S. states and political subdivisions	0	0
Corporate debt securities	0	0
ABS	0	0
RMBS	0	0
CMBS	0	0
CLOs	0	0
Total debt securities	13,312	30,690
Equity securities	2,971	2,860
Total investment portfolio	16,283	33,550
Real estate acquired	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities and obligations of U.S. government corporations and agencies	90,388	42,840
Obligations of U.S. states and political subdivisions	2,112,903	2,142,325
Corporate debt securities	1,875,255	1,743,910
ABS	9,860	59,565
RMBS	192,896	224,209
CMBS	305,425	319,817
CLOs	109,734	121,175
Total debt securities	4,696,461	4,653,841
Equity securities	0	0
Total investment portfolio	4,696,461	4,653,841
Real estate acquired	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities and obligations of U.S. government corporations and agencies	0	0
Obligations of U.S. states and political subdivisions	380	691
Corporate debt securities	0	0
ABS	0	0
RMBS	0	0
CMBS	0	0
CLOs	0	0
Total debt securities	380	691
Equity securities	4,268	4,268
Total investment portfolio	4,648	4,959
Real estate acquired	$ 11,728	$ 11,748

Fair Value Measurements - Unobs

Fair Value Measurements - Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Total Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 4,845	$ 7,996	$ 4,959	$ 4,083
Total realized/unrealized gains (losses):
Included in other comprehensive income		(3,519)
Included in earnings and reported as net realized investment gains		3,579		3,579
Included in earnings and reported as losses incurred, net	0	0	0	0
Purchases	0	1,167	0	4,258
Sales	(197)	(4,125)	(311)	(6,822)
Balance at end of period	4,648	5,098	4,648	5,098
Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	577	1,056	691	1,228
Total realized/unrealized gains (losses):
Included in other comprehensive income		0
Included in earnings and reported as net realized investment gains		0		0
Included in earnings and reported as losses incurred, net	0	0	0	0
Purchases	0	0	0	0
Sales	(197)	(226)	(311)	(398)
Balance at end of period	380	830	380	830
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	4,268	6,940	4,268	2,855
Total realized/unrealized gains (losses):
Included in other comprehensive income		(3,519)
Included in earnings and reported as net realized investment gains		3,579		3,579
Included in earnings and reported as losses incurred, net	0	0	0	0
Purchases	0	1,167	0	4,258
Sales	0	(3,899)	0	(6,424)
Balance at end of period	4,268	4,268	4,268	4,268
Real Estate Acquired
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	10,271	9,642	11,748	12,149
Total realized/unrealized gains (losses):
Included in other comprehensive income		0
Included in earnings and reported as net realized investment gains		0		0
Included in earnings and reported as losses incurred, net	(592)	(501)	(818)	(143)
Purchases	8,881	8,938	26,985	27,953
Sales	(6,832)	(7,515)	(26,187)	(29,395)
Balance at end of period	$ 11,728	$ 10,564	$ 11,728	$ 10,564

Fair Value Measurements - Liabi

Fair Value Measurements - Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Aug. 31, 2016
5% Convertible Senior Notes due 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (in hundredths)	5.00%
2% Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (in hundredths)	2.00%
Senior Notes | 5.75% Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (in hundredths)	5.75%		5.75%
9% Debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (in hundredths)	9.00%
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FHLB Advance	$ 155,000	$ 155,000
5% Notes	0	144,789
2% Notes	0	204,672
5.75% Notes	418,271	417,406
9% Debentures	256,872	256,872
Total financial liabilities	830,143	1,178,739
Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FHLB Advance	154,175	151,905
5% Notes	0	147,679
2% Notes	0	308,605
5.75% Notes	468,248	445,987
9% Debentures	349,798	323,040
Total financial liabilities	$ 972,221	$ 1,377,216

Other Comprehensive Income (Det

Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	$ 17,535	$ (22,592)	$ 75,387	$ 140,246
Income tax (expense) benefit	(6,138)	7,907	(26,384)	(49,211)
Other comprehensive income (loss), net of tax	11,397	(14,685)	49,003	91,035
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Net realized investment (losses) gains	(47)	5,092	(211)	8,984
Other underwriting and operating expenses, net	(39,888)	(37,870)	(119,164)	(112,995)
Other revenue	2,922	3,867	7,846	14,234
Income before tax	184,467	83,749	539,040	352,676
Income tax benefit (expense)	(64,440)	(27,131)	(210,593)	(117,646)
Net income	120,027	56,618	328,447	235,030
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			2,548,842
Other comprehensive income before reclassifications			47,777
Less: Amounts reclassified from AOCL			(1,226)
Balance, end of period	3,130,149	2,583,079	3,130,149	2,583,079
Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Income before tax	(201)	5,618	(1,886)	8,535
Income tax benefit (expense)	71	(1,966)	660	(2,864)
Net income	(130)	3,652	(1,226)	5,671
Accumulated other comprehensive (loss) income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income (loss), net of tax			49,003	91,035
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			(75,100)	(60,880)
Balance, end of period	(26,097)	30,155	(26,097)	30,155
Net unrealized gains and losses on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	17,761	(22,206)	76,022	142,852
Income tax (expense) benefit	(6,217)	7,772	(26,608)	(50,121)
Other comprehensive income (loss), net of tax	11,544	(14,434)	49,414	92,731
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			(20,797)
Other comprehensive income before reclassifications			47,746
Less: Amounts reclassified from AOCL			(1,668)
Balance, end of period	28,617		28,617
Net unrealized gains and losses on available-for-sale securities | Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Net realized investment (losses) gains	(427)	5,248	(2,566)	5,958
Income tax benefit (expense)	150	(1,837)	898	(1,963)
Net income	(277)	3,411	(1,668)	3,995
Net benefit plan assets and obligations recognized in shareholders' equity
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	(226)	(370)	(680)	(1,110)
Income tax (expense) benefit	79	129	238	388
Other comprehensive income (loss), net of tax	(147)	(241)	(442)	(722)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			(54,272)
Other comprehensive income before reclassifications			0
Less: Amounts reclassified from AOCL			442
Balance, end of period	(54,714)		(54,714)
Net benefit plan assets and obligations recognized in shareholders' equity | Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Other underwriting and operating expenses, net	226	370	680	1,110
Income tax benefit (expense)	(79)	(129)	(238)	(388)
Net income	147	241	442	722
Net unrealized foreign currency translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	0	(16)	45	(1,496)
Income tax (expense) benefit	0	6	(14)	522
Other comprehensive income (loss), net of tax	0	(10)	31	(974)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			(31)
Other comprehensive income before reclassifications			31
Less: Amounts reclassified from AOCL			0
Balance, end of period	0		0
Net unrealized foreign currency translation | Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Other revenue	0	0	0	1,467
Income tax benefit (expense)	0	0	0	(513)
Net income	$ 0	$ 0	$ 0	$ 954

Benefit Plans (Details)

Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension and Supplemental Executive Retirement Plans
Components of Net Periodic Benefit Cost [Abstract]
Service cost	$ 2,389	$ 2,283	$ 7,167	$ 6,848
Interest cost	3,869	3,976	11,606	11,929
Expected return on plan assets	(5,025)	(4,877)	(15,074)	(14,631)
Recognized net actuarial loss	1,543	1,464	4,627	4,392
Amortization of prior service cost	(107)	(172)	(320)	(515)
Net periodic benefit cost (benefit)	2,669	2,674	8,006	8,023
Employer contributions in current fiscal year			9,300
Other Postretirement Benefit Plans
Components of Net Periodic Benefit Cost [Abstract]
Service cost	203	188	610	564
Interest cost	176	176	529	528
Expected return on plan assets	(1,312)	(1,222)	(3,936)	(3,665)
Recognized net actuarial loss	0	0	0	0
Amortization of prior service cost	(1,662)	(1,662)	(4,987)	(4,987)
Net periodic benefit cost (benefit)	$ (2,595)	$ (2,520)	$ (7,784)	$ (7,560)

Income Taxes (Details)

Income Taxes (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2007	Dec. 31, 2016	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Net operating loss carryforwards, regular tax basis	$ 987,600,000
Net operating loss carryforwards for computing the alternative minimum tax	117,900,000
Valuation allowance	0		$ 0
Information regarding income tax examinations [Abstract]
Amount of IRS assessment for unpaid taxes and penalties related to REMIC issue				$ 197,500,000
Estimate of federal interest that may be due	200,300,000
Amount of payment made related to the IRS assessment on the REMIC issue		$ 65,200,000
Amount of IRS assessment for unpaid taxes and penalties related to disallowance of carryback of 2009 net operating loss				$ 261,400,000
Estimate of additional state income taxes and interest that may be due	84,100,000
Total amount of unrecognized tax benefits	141,800,000
Provision for additional taxes and interest recorded	28,400,000
Total amount of the unrecognized tax benefits that would affect our effective tax rate	119,800,000
Unrecognized tax benefits, accrued interest	$ 50,800,000		$ 28,900,000

Loss Reserves - Reconciliation

Loss Reserves - Reconciliation of Beginning and Ending Balances (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Loss Reserve [Roll Forward]
Reserve at beginning of period	$ 1,438,813	$ 1,893,402
Less reinsurance recoverable	50,493	44,487
Net reserve at beginning of period	1,388,320	1,848,915
Losses and LAE incurred in respect of default notices received in:
Current year	219,485	292,090
Prior years	(134,780)	(99,591)
Total losses incurred	84,705	192,499
Losses and LAE paid in respect of default notices received in:
Current year	5,474	5,942
Prior years	407,977	549,706
Reinsurance terminations (2)	301	(2,854)
Total losses paid	413,752	552,794
Net reserve at end of period	1,059,273	1,488,620
Plus reinsurance recoverables	45,878	46,863
Reserve at end of period	$ 1,105,151	$ 1,535,483

Loss Reserves (Details)

Loss Reserves (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2016loan	Sep. 30, 2017USD ($)loan	Sep. 30, 2016loan	Sep. 30, 2017USD ($)loan	Sep. 30, 2016USD ($)loan	Dec. 31, 2016USD ($)
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Other items removed from inventory (in loans) | loan		(209)	0	(1,337)	(1,273)
Prior years | $				$ 407,977	$ 549,706
Premium refund liability, expected claim payments | $		$ 68,000		68,000		$ 85,000
Prior years | $				$ (134,780)	$ (99,591)
Primary Default Inventory [Roll Forward]
Default inventory at the beginning of period (in loans) | loan	51,433	41,317	52,558	50,282	62,633
New notices (in loans) | loan	5,519	15,950	17,607	45,352	50,418
Cures (in loans) | loan		(13,546)	(15,556)	(45,382)	(50,249)
Paids (including those charged to a deductible or captive) (in loans) | loan		(2,195)	(3,051)	(7,403)	(9,619)
Rescissions and denials (in loans) | loan		(82)	(125)	(277)	(477)
Other items removed from inventory (in loans) | loan		(209)	0	(1,337)	(1,273)
Default inventory at end of period (in loans) | loan		41,235	51,433	41,235	51,433
Decrease in estimated claim rate on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Percentage of prior year default inventory resolved (as a percent)				59.00%	54.00%
Prior years | $				$ (138,000)	$ (108,000)
Settlements for commutations of coverage, pools of nonperforming loans
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $				54,000
Settlements for commutations of coverage, pools of nonperforming loans, and claims paying practiices
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $					52,000
(Decrease) increase in estimated severity on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $				(2,000)	12,000
Change in estimates related to pool reserves, LAE reserves and reinsurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $				$ 5,000	$ (4,000)

Loss Reserves - Delinquent Item

Loss Reserves - Delinquent Items (Details) - loan	1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Default notices for loans in IADAs		637
Other default notices		4,882
Total default notices		5,519	15,950	17,607	45,352	50,418
Aging of the Primary Default Inventory [Abstract]
3 months or less (in loans)			11,331	12,333	11,331	12,333		12,194
3 months or less (as a percent)			27.00%	24.00%	27.00%	24.00%		24.00%
4 - 11 months (in loans)			11,092	12,648	11,092	12,648		13,450
4 - 11 months (as a percent)			27.00%	25.00%	27.00%	25.00%		27.00%
12 months or more (in loans)			18,812	26,452	18,812	26,452		24,638
12 months or more (as a percent)			46.00%	51.00%	46.00%	51.00%		49.00%
Total primary default inventory (in loans)			41,235	51,433	41,235	51,433	41,317	50,282	52,558	62,633
Total primary default inventory (as a percent)			100.00%	100.00%	100.00%	100.00%		100.00%
Primary claims received inventory included in ending default inventory (in loans)			1,063	1,636	1,063	1,636		1,385
Primary claims received inventory included in ending default inventory (as a percent)			3.00%	3.00%	3.00%	3.00%		3.00%
Percent of default inventory in default for more than 36 months (as a percent)			45.00%	48.00%	45.00%	48.00%		47.00%
Number of payments delinquent [Abstract]
3 payments or less (in loans)			16,916	18,374	16,916	18,374		18,419
3 payments or less (as a percent)			41.00%	36.00%	41.00%	36.00%		36.00%
4 - 11 payments (in loans)			10,583	12,282	10,583	12,282		12,892
4 - 11 payments (as a percent)			26.00%	24.00%	26.00%	24.00%		26.00%
12 payments or more (in loans)			13,736	20,777	13,736	20,777		18,971
12 payments or more (as a percent)			33.00%	40.00%	33.00%	40.00%		38.00%
Total primary default inventory (in loans)			41,235	51,433	41,235	51,433	41,317	50,282	52,558	62,633
Total primary default inventory (as a percent)			100.00%	100.00%	100.00%	100.00%		100.00%
Pool insurance notice inventory (in loans)			1,426	1,979	1,426	1,979		1,883
Subsequent event
Liability for Claims and Claims Adjustment Expense [Line Items]
Default notices for loans in IADAs	3,394
Other default notices	4,549
Total default notices	7,943

Shareholders' Equity (Details)

Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 23, 2015	Apr. 30, 2017	Oct. 31, 2016	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017
Class of Warrant or Right [Line Items]
Shares repurchased during period (in shares)			4,800,000	13,500,000
Shares repurchased during period, number of unsettled shares				2,100,000	2,100,000
Shares repurchased, weighted average price per share				$ 8.02
Shares repurchased, value			$ 16.5		$ 108.1
Common stock, beneficial ownership threshold to be considered an Acquiring Person (as a percent)	5.00%
Common shares purchasable per Right (in shares)	0.1
Shareholder rights accompanying each outstanding share of the company's common stock (in number of Rights)	1
Purchase price (in dollars per share)	$ 45
Purchase price, one-tenth share (in dollars per share)	4.50
Redemption price (in dollars per Right)	$ 0.001
Rights
Class of Warrant or Right [Line Items]
Number of rights per outstanding share of common stock (in shares)	1
Period after public announcement that a person has become an acquirer (in days)	10 days
Period after a person announces a tender offer which would make them an acquirer (in days)	10 days
2% Notes
Class of Warrant or Right [Line Items]
Stated interest rate (in hundredths)						2.00%
Principal amount of notes converted into shares		$ 202.5
Convertible Senior Notes
Class of Warrant or Right [Line Items]
Stated interest rate (in hundredths)						5.00%
Convertible Senior Notes | 2% Convertible Senior Notes
Class of Warrant or Right [Line Items]
Shares issued during period upon conversion of convertible debt (in shares)		29,100,000
Treasury stock reissued during period upon conversion of notes (in shares)		18,700,000
Stock issued during period upon conversion of notes (in shares)		10,400,000
Shares issued for repayment of debt (in shares)				18,300,000
9% Debentures
Class of Warrant or Right [Line Items]
Stated interest rate (in hundredths)						9.00%
Reacquisition of convertible junior subordinated debentures-equity component					$ 6.3

Share-Based Compensation (Detai

Share-Based Compensation (Details) - $ / shares shares in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
RSUs subject to performance conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,237	1,257
Weighted Average Share Fair Value (in dollars per share)	$ 10.41	$ 5.66
RSUs subject only to service conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	395	433
Weighted Average Share Fair Value (in dollars per share)	$ 10.41	$ 5.67
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years

Statutory Information (Details)

Statutory Information (Details) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)jurisdiction	Sep. 30, 2017USD ($)jurisdiction	Dec. 31, 2016USD ($)
Statutory capital requirements [Abstract]
Number of jurisdictions with risk-to-capital requirements (in jurisdictions) | jurisdiction	16	16
Maximum permitted risk-to-capital ratio commonly applied		25 to 1
Risk to capital ratio of combined insurance operations, including reinsurance affiliates, at end of period		11.1 to 1
Risk-to-capital ratio for combined insurance operations	11.1	11.1
Percentage of statutory policyholders surplus used to determine maximum allowable dividends (as a percent)	10.00%	10.00%
Mortgage Guaranty Insurance Corporation
Statutory capital requirements [Abstract]
Maximum risk-to-capital ratio		25
Risk to capital ratio at end of period		10.1 to 1
Risk-to-capital ratio	10.1	10.1
Amount of policyholders position above or below required MPP	$ 1,900	$ 1,900
Amount of required MPP	1,200	$ 1,200
Cash dividends paid	$ 40
Adjusted statutory net income measurement period (in years)		3 years
Adjusted statutory net income dividend payment measurement period (in years)		2 years
Reduction in statutory net income due to increase in contingency reserve			$ 490