MGIC Investment (MTG) 10-Q 8 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
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		371,347,632
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment portfolio:
Fixed income, available for sale, at fair value (amortized cost, 2018 - $4,974,616; 2017 - $4,946,278)	$ 4,930,063	$ 4,983,315
Equity securities, at fair value (cost, 2018 - $4,143; 2017 - $7,223)	4,099
Equity securities, at fair value (cost, 2018 - $4,143; 2017 - $7,223)		7,246
Other invested assets, at cost	3,100	0
Total investment portfolio	4,937,262	4,990,561
Cash and cash equivalents	177,488	99,851
Accrued investment income	45,123	46,060
Reinsurance recoverable on loss reserves	45,474	48,474
Reinsurance recoverable on paid losses	3,718	3,872
Premiums receivable	52,701	54,045
Home office and equipment, net	48,382	44,936
Deferred insurance policy acquisition costs	18,928	18,841
Deferred income taxes, net	211,994	234,381
Other assets	75,273	78,478
Total assets	5,616,343	5,619,499
Liabilities:
Loss reserves	924,171	985,635
Unearned premiums	397,688	392,934
Federal Home Loan Bank advance	155,000	155,000
Senior notes	418,848	418,560
Convertible junior subordinated debentures	256,872	256,872
Other liabilities	232,361	255,972
Total liabilities	2,384,940	2,464,973
Contingencies
Shareholders’ equity:
Common stock (one dollar par value, shares authorized 1,000,000; shares issued 2018 - 371,348; 2017 - 370,567; shares outstanding 2018 - 371,348; 2017 - 370,567)	371,348	370,567
Paid-in capital	1,847,000	1,850,582
Accumulated other comprehensive loss, net of tax	(107,760)	(43,783)
Retained earnings	1,120,815	977,160
Total shareholders’ equity	3,231,403	3,154,526
Total liabilities and shareholders’ equity	$ 5,616,343	$ 5,619,499

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 4,974,616	$ 4,946,278
Equity securities, cost	$ 4,143
Equity securities, cost		$ 7,223
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)	371,348,000	370,567,000
Common stock, shares outstanding (in shares)	371,348,000	370,567,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Premiums written:
Direct	$ 270,034	$ 265,823
Assumed	92	1,288
Ceded	(33,220)	(30,409)
Net premiums written	236,906	236,702
Increase in unearned premiums, net	(4,799)	(7,599)
Net premiums earned	232,107	229,103
Investment income, net of expenses	32,121	29,477
Net realized investment losses	(329)	(125)
Other revenue	1,871	2,425
Total revenues	265,770	260,880
Losses and expenses:
Losses incurred, net	23,850	27,619
Amortization of deferred policy acquisition costs	2,572	2,230
Other underwriting and operating expenses, net	46,090	40,765
Interest expense	13,233	16,309
Total losses and expenses	85,745	86,923
Income before tax	180,025	173,957
Provision for income taxes	36,388	84,159
Net income	$ 143,637	$ 89,798
Earnings per share:
Basic (in dollars per share)	$ 0.39	$ 0.26
Diluted (in dollars per share)	$ 0.38	$ 0.24
Weighted average common shares outstanding - basic (in shares)	370,908	341,009
Weighted average common shares outstanding - diluted (in shares)	391,562	402,175

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 143,637	$ 89,798
Other comprehensive (loss) income, net of tax:
Change in unrealized investment gains and losses	(64,453)	12,121
Benefit plan adjustments	494	(153)
Foreign currency translation adjustment	0	31
Other comprehensive (loss) income, net of tax	(63,959)	11,999
Comprehensive income	$ 79,678	$ 101,797

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, 2016		$ 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		771	(7,493)
Equity compensation			3,461
Other comprehensive income, net of tax	$ 11,999				11,999
Net income	89,798					89,798
Balance, end of period at Mar. 31, 2017	2,647,531	360,171	1,778,305	(150,359)	(63,101)	722,515
Balance, beginning of period at Dec. 31, 2017	3,154,526	370,567	1,850,582	0	(43,801)	977,178
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net common stock issued under share-based compensation plans		781	(8,854)
Equity compensation			5,272
Other comprehensive income, net of tax	(63,959)				(63,959)
Net income	143,637					143,637
Balance, end of period at Mar. 31, 2018	$ 3,231,403	$ 371,348	$ 1,847,000	$ 0	$ (107,760)	$ 1,120,815

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 143,637	$ 89,798
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15,833	17,079
Deferred tax expense	39,388	48,932
Net realized investment losses	329	125
Change in certain assets and liabilities:
Accrued investment income	937	287
Reinsurance recoverable on loss reserves	3,000	3,835
Reinsurance recoverable on paid losses	154	(165)
Premium receivable	1,344	485
Deferred insurance policy acquisition costs	(87)	(477)
Profit commission receivable	377	(3,395)
Loss reserves	(61,464)	(103,771)
Unearned premiums	4,754	7,585
Return premium accrual	(5,500)	(4,800)
Income taxes payable - current	(3,117)	34,654
Other, net	(5,619)	(12,703)
Net cash provided by operating activities	133,966	77,469
Purchases of investments:
Fixed income securities	(209,477)	(187,077)
Equity securities	(20)	(19)
Proceeds from sales of fixed income securities	10,844	33,980
Proceeds from maturity of fixed income securities	155,605	199,234
Net increase in payable for securities	0	10,336
Additions to property and equipment	(5,208)	(4,014)
Net cash (used in) provided by investing activities	(48,256)	52,440
Cash flows from financing activities:
Proceeds from revolving credit facility	0	150,000
Payment of debt issuance costs	0	(1,523)
Payment of withholding taxes related to share-based compensation net share settlement	(8,073)	(6,722)
Net cash (used in) provided by financing activities	(8,073)	141,755
Net increase in cash and cash equivalents	77,637	271,664
Cash and cash equivalents at beginning of period	99,851	155,410
Cash and cash equivalents at end of period	$ 177,488	$ 427,074

Nature of Business and Basis of

Nature of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
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 to protect against loss from defaults on low down payment residential mortgage loans. An insurance subsidiary of MGIC provides credit insurance for certain mortgages under Fannie Mae and Freddie Mac (the “GSEs”) credit risk transfer programs. 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, 2017 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, 2018 . 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 which 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 of insurance in force, calculated from tables of factors with several risk dimensions and subject to a floor amount). Based on our interpretation of the PMIERs, as of March 31, 2018 , 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 2017 amounts have been made in the accompanying financial statements to conform to the 2018 presentation. Subsequent events We have considered subsequent events through the date of this filing. Share repurchase program On April 26, 2018, our Board of Directors authorized a share repurchase program under which we may repurchase up to $200 million of our common stock through the end of 2019. Repurchases may be made from time to time on the open market or through privately negotiated transactions. The repurchase program may be suspended for periods or discontinued at any time.

New Accounting Pronouncements

New Accounting Pronouncements	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements Accounting standards effective in 2018, or early adopted, and relevant to our financial statements Table 2.1 shows the relevant amendments to accounting standards that have been implemented for the fiscal year beginning January 1, 2018; none had a material impact on our consolidated financial statements or disclosures. Table 2.1 Standard / Interpretation Effective date Amended Standards ASC 718 Compensation - Stock Compensation • ASU 2017-09 - Scope of Modification Accounting January 1, 2018 ASC 310 Receivables - Nonrefundable Fees and Other Costs • ASU 2017-08 - Premium Amortization on Purchased Callable Debt Securities January 1, 2019 ASC 715 Compensation - Retirement Benefits • ASU 2017-07 - Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost January 1, 2018 ASC 825 Financial Instruments - Overall • ASU 2016-01 - Recognition and Measurement of Financial Assets and Financial Liabilities January 1, 2018 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. ◦ Adoption impact: The adoption of this guidance had no 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. ◦ Adoption impact: We adopted this guidance as of January 1, 2018 with no impact to our consolidated financial statements or disclosures as our accounting practice adhered to the updated guidance. 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. ◦ Adoption impact: The adoption of this guidance had no impact on our consolidated financial statements or disclosures as the service cost component is reported in the same financial statement caption as other compensation costs and we do not present a subtotal of income outside of income from operations. The service cost component of our benefit plans is disclosed in Note 10 - “Benefit Plans” to our consolidated financial statements. 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. ◦ Adoption impact: The adoption of this guidance resulted in an immaterial cumulative effect adjustment to our 2018 beginning accumulated other comprehensive (loss) income and retained earnings to recognize unrealized gains on equity investments. At December 31, 2017, equity investments were classified as available-for-sale on the consolidated balance sheet. Upon adoption the updated guidance eliminated the available-for-sale balance sheet classification for equity securities. In February 2018, the FASB issued a separate update for technical corrections and improvements to clarify certain aspects of the guidance issued above. This update clarifies the presentation of investments in Federal Home Loan Bank stock and prohibits the investment from being shown with equity securities. ◦ Adoption impact: As of March 31, 2018, the value of our investment in Federal Home Loan Bank of Chicago (“FHLB”) stock, which is carried at cost, is presented within “Other invested assets” on our consolidated balance sheet. Prospective Accounting Standards Table 2.2 shows the relevant new amendments to accounting standards, which are not yet effective or adopted. Table 2.2 Standard / Interpretation Effective date Amended Standards ASC 326 Financial Instruments - Credit Losses • ASU 2016-13 - Measurement of Credit Losses on Financial Instruments January 1, 2020 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.

Debt

Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt Debt obligations The par value of our long-term debt obligations and their aggregate carrying values as of March 31, 2018 and December 31, 2017 are presented in table 3.1 below. Table 3.1 Long-term debt obligations (In millions) March 31, December 31, FHLB Advance $ 155.0 $ 155.0 5.75% Notes 425.0 425.0 9% Debentures (1) 256.9 256.9 Long-term debt, par value 836.9 836.9 Debt issuance costs (6.2 ) (6.5 ) Long-term debt, carrying value $ 830.7 $ 830.4 (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, 9% Debentures, and any amounts drawn on our revolving credit facility, are obligations of our holding company, MGIC Investment Corporation, and not of its subsidiaries. In addition to interest on amounts drawn, the unused portion of our revolving credit facility is subject to recurring commitment fees, which is charged to interest expense. The Federal Home Loan Bank Advance (the “FHLB Advance”) is an obligation of MGIC. Table 3.2 below presents interest payments on our debt obligations. Table 3.2 Interest payments on debt obligations Three Months Ended March 31, (In millions) 2018 2017 Revolving credit facility $ 0.2 $ — FHLB Advance 0.7 0.7 5.75% Notes 12.2 12.9 Total interest payments $ 13.1 $ 13.6

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2018
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance The reinsurance agreements we have entered into, excluding captive agreements (which were immaterial), are discussed below. The effect of all of our reinsurance agreements on premiums earned and losses incurred is shown in table 4.1 below. Table 4.1 Reinsurance Three Months Ended March 31, (In thousands) 2018 2017 Premiums earned: Direct $ 265,251 $ 259,428 Assumed 121 98 Ceded (33,265 ) (30,423 ) Net premiums earned $ 232,107 $ 229,103 Losses incurred: Direct $ 31,501 $ 32,413 Assumed 90 105 Ceded (7,741 ) (4,899 ) Losses incurred, net $ 23,850 $ 27,619 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. Each of the reinsurers under our QSR Transactions has an insurer financial strength rating of A- or better by Standard and Poor’s Rating Services, A.M. Best or both. 2018 QSR Transaction. We entered into a 2018 QSR Transaction with a group of unaffiliated reinsurers to manage our exposure to losses resulting from the covered mortgage guaranty insurance policies and to provide reinsurance capital credit under the PMIERs. The 2018 QSR Transaction has an effective date of January 1, 2018, and provides coverage on new business written in 2018 that meets certain eligibility requirements. Under the 2018 QSR Transaction, we will cede losses incurred and premiums on or after the effective date through December 31, 2029, at which time the agreement expires. Early termination of the agreement can be elected by us effective December 31, 2021, and annually thereafter, 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. The structure of the 2018 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 2018 QSR Transaction, we will receive a profit commission provided that the loss ratio on the loans covered under the agreement remains below 62% . 2015 and 2017 QSR Transactions. 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. 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% . Table 4.2 below presents a summary of our quota share reinsurance agreements, excluding captive agreements (which were immaterial), for the three months ended March 31, 2018 and 2017 . Table 4.2 Quota share reinsurance Three Months Ended March 31, (In thousands) 2018 2017 Ceded premiums written and earned, net of profit commission (1) $ 33,036 $ 28,895 Ceded losses incurred 7,788 4,687 Ceding commissions (2) 12,645 12,003 Profit commission 30,189 31,117 (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 $43.5 million as of March 31, 2018 and $39.3 million as of December 31, 2017 . 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.

Litigation and Contingencies

Litigation and Contingencies	3 Months Ended
	Mar. 31, 2018
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. We refer to insurance rescissions and denials of claims collectively as “rescissions” and variations of that term. In addition, our insurance policies generally 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 2017 and the first quarter of 2018, curtailments reduced our average claim paid by approximately 5.6% and 7.3% , respectively. 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 $282 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 2017 and the first three months of 2018 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 consolidated results of operations. See Note 11 – “Income Taxes” for a description of federal income tax contingencies.

Earnings per Share

Earnings per Share	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 , 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. Table 6.1 reconciles the numerators and denominators used to calculate basic and diluted EPS. Table 6.1 Earnings per share Three Months Ended March 31, (In thousands, except per share data) 2018 2017 Basic earnings per share: Net income $ 143,637 $ 89,798 Weighted average common shares outstanding - basic 370,908 341,009 Basic earnings per share $ 0.39 $ 0.26 Diluted earnings per share: Net income $ 143,637 $ 89,798 Interest expense, net of tax (1) : 2% Notes — 823 5% Notes — 1,282 9% Debentures 4,566 3,757 Diluted income available to common shareholders $ 148,203 $ 95,660 Weighted average common shares outstanding - basic 370,908 341,009 Effect of dilutive securities: Unvested RSUs 1,626 1,488 2% Notes — 29,859 5% Notes — 10,791 9% Debentures 19,028 19,028 Weighted average common shares outstanding - diluted 391,562 402,175 Diluted earnings per share $ 0.38 $ 0.24 (1) The three months ended March 31, 2018 and 2017 were tax effected at a rate of 21% and 35% , respectively.

Investments

Investments	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Investments	Investments Fixed maturities The amortized cost, gross unrealized gains and losses, and fair value of investments in fixed income securities classified as available-for-sale at March 31, 2018 and December 31, 2017 are shown in tables 7.1a and 7.1b below. Table 7.1a Details of fixed income investments by category - current year March 31, 2018 (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 $ 191,018 $ 256 $ (2,212 ) $ 189,062 Obligations of U.S. states and political subdivisions 2,093,901 27,926 (19,130 ) 2,102,697 Corporate debt securities 2,087,977 1,921 (33,819 ) 2,056,079 Asset backed securities (“ABS”) 9,451 — (29 ) 9,422 Residential mortgage backed securities (“RMBS”) 182,050 48 (10,558 ) 171,540 Commercial mortgage backed securities (“CMBS”) 302,434 722 (9,800 ) 293,356 Collateralized loan obligations (“CLO”) 107,785 163 (41 ) 107,907 Total fixed income securities 4,974,616 31,036 (75,589 ) 4,930,063 Table 7.1b Details of fixed income investments by category - prior year-end December 31, 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 $ 179,850 $ 274 $ (1,278 ) $ 178,846 Obligations of U.S. states and political subdivisions 2,105,063 56,210 (8,749 ) 2,152,524 Corporate debt securities 2,065,475 10,532 (9,169 ) 2,066,838 ABS 4,925 — (2 ) 4,923 RMBS 189,153 60 (7,364 ) 181,849 CMBS 301,014 1,204 (4,906 ) 297,312 CLOs 100,798 304 (79 ) 101,023 Total fixed income securities 4,946,278 68,584 (31,547 ) 4,983,315 (1) At March 31, 2018 and December 31, 2017 , there were no other-than-temporary impairment losses recorded in other comprehensive income. The amortized cost and fair values of fixed income securities at March 31, 2018 , by contractual maturity, are shown in table 7.2 below. 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 ABS, RMBS, CMBS, and CLOs provide for periodic payments throughout their lives, they are listed in separate categories. Table 7.2 Fixed income securities maturity schedule March 31, 2018 (In thousands) Amortized Cost Fair Value Due in one year or less $ 650,415 $ 649,088 Due after one year through five years 1,507,245 1,487,678 Due after five years through ten years 909,711 893,329 Due after ten years 1,305,525 1,317,743 $ 4,372,896 $ 4,347,838 ABS 9,451 9,422 RMBS 182,050 171,540 CMBS 302,434 293,356 CLOs 107,785 107,907 Total as of March 31, 2018 $ 4,974,616 $ 4,930,063 Proceeds from sales of fixed income securities classified as available-for-sale were $10.8 million and $34.0 million during the three months ended March 31, 2018 and 2017 , respectively. Gross gains of $0.1 million and $0.2 million and gross losses of $0.3 million and $0.3 million were realized on those sales during the three months ended March 31, 2018 and 2017 , respectively. Equity securities The cost and fair value of investments in equity securities at March 31, 2018 and December 31, 2017 are shown in tables 7.3a and 7.3b below. As described in Note 2 - “New Accounting Pronouncements,” updated guidance regarding the “ Recognition and Measurement of Financial Assets and Financial Liabilities” became effective on January 1, 2018, which prohibits our investment in FHLB stock from being presented with equity securities. The amount of our FHLB stock investment has been reclassified and presented in “Other invested assets” on our consolidated balance sheet as of March 31, 2018. Table 7.3a Details of equity security investments - current year March 31, 2018 (In thousands) Cost Gross Gains Gross Losses Fair Value Equity securities $ 4,143 $ 8 $ (52 ) $ 4,099 Table 7.3b Details of equity security investments - prior year-end December 31, 2017 (In thousands) Cost Gross Gains Gross Losses Fair Value Equity securities $ 7,223 $ 39 $ (16 ) $ 7,246 For the three months ended March 31, 2018 , we recognized $0.1 million of net losses on equity securities still held as of March 31, 2018 . Other invested assets Other invested assets include an investment in FHLB stock that is carried at cost, which due to its nature approximates fair value. Ownership of FHLB stock provides access to a secured lending facility, and our current FHLB Advance amount is secured by eligible collateral whose fair value is maintained at least at 102% of the outstanding principal balance. As of March 31, 2018 , that collateral consisting of fixed income securities is included in our total investment portfolio amount with a total fair value of $165.6 million . Unrealized investment losses Tables 7.4a and 7.4b below summarize, for all available-for-sale investments in an unrealized loss position at March 31, 2018 and December 31, 2017 , the aggregate fair value and gross unrealized loss by the length of time those securities have been continuously in an unrealized loss position. The fair value amounts reported in tables 7.4a and 7.4b are estimated using the process described in Note 8 - “Fair Value Measurements” to these consolidated financial statements and in Note 3 - “Significant Accounting Policies” of the notes to the consolidated financial statements in our 2017 Annual Report on Form 10-K. Table 7.4a Investments unrealized losses - current year March 31, 2018 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 $ 77,510 $ (1,532 ) $ 31,491 $ (680 ) $ 109,001 $ (2,212 ) Obligations of U.S. states and political subdivisions 905,755 (11,622 ) 201,094 (7,508 ) 1,106,849 (19,130 ) Corporate debt securities 1,743,627 (26,797 ) 148,468 (7,022 ) 1,892,095 (33,819 ) ABS 9,423 (29 ) — — 9,423 (29 ) RMBS 14,226 (416 ) 156,842 (10,142 ) 171,068 (10,558 ) CMBS 114,206 (2,162 ) 126,941 (7,638 ) 241,147 (9,800 ) CLOs — — 1,936 (41 ) 1,936 (41 ) Total $ 2,864,747 $ (42,558 ) $ 666,772 $ (33,031 ) $ 3,531,519 $ (75,589 ) Table 7.4b Investments unrealized losses - prior year-end December 31, 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 $ 144,042 $ (796 ) $ 31,196 $ (482 ) $ 175,238 $ (1,278 ) Obligations of U.S. states and political subdivisions 505,311 (3,624 ) 211,684 (5,125 ) 716,995 (8,749 ) Corporate debt securities 932,350 (4,288 ) 200,716 (4,881 ) 1,133,066 (9,169 ) ABS 4,923 (2 ) — — 4,923 (2 ) RMBS 14,979 (280 ) 166,329 (7,084 ) 181,308 (7,364 ) CMBS 51,096 (358 ) 138,769 (4,548 ) 189,865 (4,906 ) CLOs 14,243 (7 ) 3,568 (72 ) 17,811 (79 ) Equity securities 226 (2 ) 431 (14 ) 657 (16 ) Total $ 1,667,170 $ (9,357 ) $ 752,693 $ (22,206 ) $ 2,419,863 $ (31,563 ) The unrealized losses in all categories of our investments at March 31, 2018 and December 31, 2017 were primarily caused by changes in interest rates between the time of purchase and the respective fair value measurement date. There were 788 and 586 securities in an unrealized loss position at March 31, 2018 and December 31, 2017 , respectively. During each of the three months ended March 31, 2018 and 2017 there were no other-than-temporary impairments (“OTTI”) recognized.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Recurring fair value measurements 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 based on the type of instrument. 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. Level 3 - Valuations derived from valuation techniques in which one or more significant inputs or value drivers are unobservable. 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. 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. Assets measured at fair value, by hierarchy level, as of March 31, 2018 and December 31, 2017 as shown in tables 8.1a and 8.1b below are estimated using the process described above, and more fully in Note 3 - “Significant Accounting Policies” of the notes to the consolidated financial statements in our 2017 Annual Report on Form 10-K. Table 8.1a Fair value hierarchy - current year March 31, 2018 (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 $ 189,062 $ 81,418 $ 107,644 $ — Obligations of U.S. states and political subdivisions 2,102,697 — 2,102,443 254 Corporate debt securities 2,056,079 — 2,056,079 — ABS 9,422 — 9,422 — RMBS 171,540 — 171,540 — CMBS 293,356 — 293,356 — CLOs 107,907 — 107,907 — Total fixed income securities 4,930,063 81,418 4,848,391 254 Equity securities (1) 4,099 2,931 — 1,168 Total investments at fair value $ 4,934,162 $ 84,349 $ 4,848,391 $ 1,422 Real estate acquired (2) $ 10,078 $ — $ — $ 10,078 (1) Equity securities in Level 3 are carried at cost, which approximates fair value. See “Reconciliations of Level 3 assets” below for information regarding a change in presentation of amounts previously included in Level 3 Equity securities. (2) Real estate acquired through claim settlement, which is held for sale, is reported in Other assets on the consolidated balance sheets. Table 8.1b Fair value hierarchy - prior year-end December 31, 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 $ 178,846 $ 81,598 $ 97,248 $ — Obligations of U.S. states and political subdivisions 2,152,524 — 2,152,253 271 Corporate debt securities 2,066,838 — 2,066,838 — ABS 4,923 — 4,923 — RMBS 181,849 — 181,849 — CMBS 297,312 — 297,312 — CLOs 101,023 — 101,023 — Total fixed income securities 4,983,315 81,598 4,901,446 271 Equity securities (1) 7,246 2,978 — 4,268 Total investments at fair value $ 4,990,561 $ 84,576 $ 4,901,446 $ 4,539 Real estate acquired (2) $ 12,713 $ — $ — $ 12,713 (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. Reconciliations of Level 3 assets For assets measured at fair value using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances for the three months ended March 31, 2018 and 2017 is shown in tables 8.2a and 8.2b below. As described in Note 2 - “New Accounting Pronouncements,” updated guidance regarding the Recognition and Measurement of Financial Assets and Financial Liabilities became effective on January 1, 2018, which requires that our investment in FHLB stock not be presented with equity securities. Prior to the updated guidance, our FHLB stock was included in our Level 3 equity securities. As shown in table 8.2a below, for the three months ended March 31, 2018, we have transferred our FHLB stock out of Level 3 assets, and they are carried at cost, which approximates fair value on our consolidated balance sheet as of March 31, 2018. The amount of FHLB stock is presented in “Other invested assets” as of March 31, 2018. 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. Table 8.2a Development of assets and liabilities classified within level 3 - current year quarter Three Months Ended March 31, 2018 (In thousands) Debt Securities Equity Securities Total Investments Real Estate Acquired Balance at December 31, 2017 $ 271 $ 4,268 $ 4,539 $ 12,713 Transfers out of Level 3 — (3,100 ) (3,100 ) — Total realized/unrealized gains (losses): Included in earnings and reported as losses incurred, net — — — 341 Purchases — — — 5,894 Sales (17 ) — (17 ) (8,870 ) Balance at March 31, 2018 $ 254 $ 1,168 $ 1,422 $ 10,078 Table 8.2b Development of assets and liabilities classified within level 3 - prior year quarter Three Months Ended March 31, 2017 (In thousands) Debt Equity Total Real Estate 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 — — — (163 ) Purchases — — — 8,683 Sales (8 ) — (8 ) (9,538 ) Balance at March 31, 2017 $ 683 $ 4,268 $ 4,951 $ 10,730 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. Table 8.3 presents the carrying value and fair value of our financial liabilities disclosed, but not carried, at fair value at March 31, 2018 and December 31, 2017 . The fair values of our 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. Table 8.3 Fair value measurements - liabilities March 31, 2018 December 31, 2017 (In thousands) Carrying Value Fair Value Carrying Value Fair Value FHLB Advance 155,000 149,756 $ 155,000 $ 152,124 5.75% Notes 418,848 446,730 418,560 465,473 9% Debentures 256,872 350,897 256,872 353,507 Total financial liabilities $ 830,720 $ 947,383 $ 830,432 $ 971,104

Other Comprehensive Income

Other Comprehensive Income	3 Months Ended
	Mar. 31, 2018
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 months ended March 31, 2018 and 2017 are included in table 9.1 below. Table 9.1 Components of other comprehensive (loss) income Three Months Ended March 31, (In thousands) 2018 2017 Net unrealized investment (losses) gains arising during the period $ (81,587 ) $ 18,647 Income tax benefit (expense) 17,134 (6,526 ) Net of taxes (64,453 ) 12,121 Net changes in benefit plan assets and obligations 625 (234 ) Income tax (expense) benefit (131 ) 81 Net of taxes 494 (153 ) Net changes in unrealized foreign currency translation adjustment — 45 Income tax (expense) — (14 ) Net of taxes — 31 Total other comprehensive (loss) income (80,962 ) 18,458 Total income tax benefit (expense) 17,003 (6,459 ) Total other comprehensive (loss) income, net of tax $ (63,959 ) $ 11,999 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 months ended March 31, 2018 and 2017 are included in table 9.2 below. Table 9.2 Reclassifications from AOCL Three Months Ended March 31, (In thousands) 2018 2017 Reclassification adjustment for net realized (losses) gains (1) $ (91 ) $ (747 ) Income tax benefit 19 261 Net of taxes (72 ) (486 ) Reclassification adjustment related to benefit plan assets and obligations (2) (625 ) 234 Income tax benefit (expense) 131 (81 ) Net of taxes (494 ) 153 Total reclassifications (716 ) (513 ) Total income tax benefit 150 180 Total reclassifications, net of tax $ (566 ) $ (333 ) (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. A rollforward of AOCL for the three months ended March 31, 2018 , including amounts reclassified from AOCL, are included in table 9.3 below. Table 9.3 Rollforward of AOCL Three Months Ended March 31, 2018 (In thousands) Net unrealized gains and losses on available-for-sale securities Net benefit plan assets and obligations recognized in shareholders' equity Total AOCL Balance, December 31, 2017, net of tax $ 29,257 $ (73,058 ) $ (43,801 ) Other comprehensive income before reclassifications (64,525 ) — (64,525 ) Less: Amounts reclassified from AOCL (72 ) (494 ) (566 ) Balance, March 31, 2018, net of tax $ (35,196 ) $ (72,564 ) $ (107,760 )

Benefit Plans

Benefit Plans	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Benefit Plans	Benefit Plans Table 10.1 provides the components of net periodic benefit cost for our pension, supplemental executive retirement and other postretirement benefit plans for the three months ended March 31, 2018 and 2017 . Table 10.1 Components of net periodic benefit cost Three Months Ended March 31, Pension and Supplemental Executive Retirement Plans Other Postretirement Benefit Plans (In thousands) 2018 2017 2018 2017 Service cost $ 2,562 $ 2,294 $ 270 $ 187 Interest cost 3,782 3,858 214 167 Expected return on plan assets (5,570 ) (5,036 ) (1,588 ) (1,312 ) Recognized net actuarial loss 1,785 1,535 (46 ) — Amortization of prior service cost (87 ) (107 ) (1,026 ) (1,662 ) Net periodic benefit cost (benefit) $ 2,472 $ 2,544 $ (2,176 ) $ (2,620 ) We currently intend to make contributions totaling $11 million to our qualified pension plan and supplemental executive retirement plan in 2018.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We have approximately $585.7 million of net operating loss (“NOL”) carryforwards as of March 31, 2018 . 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 March 31, 2018 and December 31, 2017. 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 March 31, 2018 , there would also be interest related to these matters of approximately $209.7 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 March 31, 2018 , those state taxes and interest would approximate $87.4 million . In addition, there could also be state tax penalties. Our total amount of unrecognized tax benefits as of March 31, 2018 is $143.7 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 reached agreement with the IRS to settle all issues in the case and the IRS subsequently submitted documentation reflecting the terms of the agreement to the Joint Committee on Taxation (“JCT”) for its review, which must be performed before a settlement can be completed. In the second quarter of 2018, we were notified that the JCT had no objection to the terms of the agreement and that the IRS was working toward finalizing the matter. The expected impact of the agreed upon settlement was previously reflected in our consolidated financial statements . Although we expect the settlement to be completed, 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 $125.0 million . We recognize interest accrued and penalties related to unrecognized tax benefits in income taxes. As of March 31, 2018 and December 31, 2017 , we had accrued $52.9 million and $52.0 million , respectively, for the payment of interest.

Loss Reserves

Loss Reserves	3 Months Ended
	Mar. 31, 2018
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 table 12.1 below shows losses incurred on delinquencies that occurred in the current year and in prior years. The amount of losses incurred relating to delinquencies that occurred in the current year represents the estimated amount to be ultimately paid on such delinquencies. The amount of losses incurred relating to delinquencies that occurred in prior years represents the difference between the actual claim rate and severity associated with those delinquencies 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 delinquencies 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 delinquent inventory, such as percentages of delinquencies that have resulted in a claim, the amount of the claims relative to the average loan exposure, changes in the relative level of delinquencies by geography and changes in average loan exposure. Losses incurred on delinquencies that occurred in the current year decreased in the first three months of 2018 compared to the same period in 2017 , primarily due to a decrease in the estimated claim rate on recently reported delinquencies and a decrease in the number of new delinquencies, net of related cures. For the three months ended March 31, 2018 and 2017 , we experienced favorable loss reserve development on previously received delinquencies, in large part, due to the resolution of approximately 31% and 29% , respectively, of the prior year delinquent inventory, with improved cure rates. The favorable loss reserve development resulting from a reduction in the estimated claim rate was partially offset in each of the three months ended March 31, 2018 and 2017 by an increase in our severity assumption on previously received delinquencies. The “Losses paid” section of table 12.1 below shows the amount of losses paid on delinquent notices received in the current year and losses paid on delinquent notices received in prior years. For several years, the average time it took to receive a claim associated with a delinquency 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 delinquent notices that do not cure. All else being equal, the longer the period between delinquency and claim filing, the greater the severity. During the first three months of 2018, our losses paid included $7 million paid upon commutation of coverage on pools of non-performing loans (“NPLs”). The commutations reduced our delinquent inventory by 224 delinquencies. These commutations had no material impact on our losses incurred, net. 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 $56 million and $61 million at March 31, 2018 and December 31, 2017 , respectively. Table 12.1 provides a reconciliation of beginning and ending loss reserves as of and for the three months ended March 31, 2018 and 2017 . Table 12.1 Development of reserves for losses and loss adjustment expenses Three Months Ended March 31, (In thousands) 2018 2017 Reserve at beginning of period $ 985,635 $ 1,438,813 Less reinsurance recoverable 48,474 50,493 Net reserve at beginning of period 937,161 1,388,320 Losses incurred: Losses and LAE incurred in respect of delinquency notices received in: Current year 59,070 80,416 Prior years (1) (35,220 ) (52,797 ) Total losses incurred 23,850 27,619 Losses paid: Losses and LAE paid in respect of delinquency notices received in: Current year 95 331 Prior years 81,983 127,224 Reinsurance terminations 236 — Total losses paid 82,314 127,555 Net reserve at end of period 878,697 1,288,384 Plus reinsurance recoverables 45,474 46,658 Reserve at end of period $ 924,171 $ 1,335,042 (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. The prior year development of the reserves in the first three months of 2018 and 2017 is reflected in table 12.2 below. Table 12.2 Reserve development on previously received delinquencies Three Months Ended March 31, (in millions) 2018 2017 Decrease in estimated claim rate on primary defaults $ (47 ) $ (54 ) Increase in estimated severity on primary defaults 16 4 Change in estimates related to pool reserves, LAE reserves and reinsurance (4 ) (3 ) Total prior year loss development (1) $ (35 ) $ (53 ) (1) A negative number for prior year loss development indicates a redundancy of prior year loss reserves. Default inventory A rollforward of our primary delinquent inventory for the three months ended March 31, 2018 and 2017 appears in table 12.3 below. 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. Table 12.3 Delinquent inventory rollforward Three Months Ended March 31, 2018 2017 Delinquent inventory at beginning of period 46,556 50,282 New notices 14,623 14,939 Cures (18,073 ) (17,128 ) Paids (including those charged to a deductible or captive) (1,571 ) (2,635 ) Rescissions and denials (68 ) (95 ) Other items removed from inventory (224 ) (14 ) Delinquent inventory at end of period 41,243 45,349 The decrease in the primary delinquent inventory experienced during 2018 and 2017 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. Hurricane activity New delinquent notice activity increased in the fourth quarter of 2017 because of hurricane activity that primarily impacted Puerto Rico, Texas, and Florida in the third quarter of 2017. In response to the hurricanes, the Federal Emergency Management Agency has declared Individual Assistance Disaster Areas (“IADA”), and during the fourth quarter of 2017 we received 9,294 new notices from the IADA. As a result, the number of loans delinquent three months or less was a higher percentage of our total inventory as of December 31, 2017 than it had been as of March 31, 2017 . Many of the loans in the IADA first reported as delinquent in the fourth quarter of 2017 remained delinquent through the period ending March 31, 2018 and are shown as 4-11 months delinquent in table 12.4 below. Correspondingly, the combined number of loans in our delinquent inventory with up to eleven missed payments was elevated as of December 31, 2017, compared to March 31, 2017, and remained elevated as of March 31, 2018 as shown in table 12.5 below. Table 12.4 below shows the number of consecutive months a borrower is delinquent. Table 12.4 Delinquent inventory - consecutive months in default March 31, 2018 December 31, 2017 March 31, 2017 3 months or less 8,770 21 % 17,119 37 % 9,184 20 % 4-11 months 16,429 40 % 12,050 26 % 13,617 30 % 12 months or more (1) (2) 16,044 39 % 17,387 37 % 22,548 50 % Total primary delinquent inventory 41,243 100 % 46,556 100 % 45,349 100 % Primary claims received inventory included in ending delinquent inventory: 819 2 % 954 2 % 1,390 3 % (1) Approximately 44% , 45% , and 48% of the primary delinquent inventory delinquent for 12 consecutive months or more has been delinquent for at least 36 consecutive months as of March 31, 2018 , December 31, 2017 , and March 31, 2017 , respectively. (2) The majority of items removed from our delinquent inventory were due to commutations of NPLs during the three months ended March 31, 2018 were delinquent for 12 consecutive months or more as of December 31, 2017. The number of months a loan is in the delinquent 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. Table 12.5 below shows the number of payments that a borrower is delinquent. Table 12.5 Delinquent inventory - number of payments delinquent March 31, 2018 December 31, 2017 March 31, 2017 3 payments or less 16,023 39 % 21,678 46 % 15,692 35 % 4-11 payments 13,734 33 % 12,446 27 % 12,275 27 % 12 payments or more (1) (2) 11,486 28 % 12,432 27 % 17,382 38 % Total primary delinquent inventory 41,243 100 % 46,556 100 % 45,349 100 % (1) Approximately 42% , 43% , and 45% of the primary delinquent inventory with 12 payments or more delinquent has at least 36 payments delinquent as of March 31, 2018 , December 31, 2017 , and March 31, 2017 , respectively. (2) The majority of items removed from our delinquent inventory were due to commutations of NPLs during the three months ended March 31, 2018 had 12 or more payments delinquent as of December 31, 2017. Pool insurance delinquent inventory decreased to 1,200 at March 31, 2018 from 1,309 at December 31, 2017 , and 1,714 at March 31, 2017 . 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	3 Months Ended
	Mar. 31, 2018
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 2018 the updated guidance of “Recognition and Measurement of Financial Assets and Financial Liabilities” became effective. The application of this guidance resulted in an immaterial cumulative effect adjustment to our 2018 beginning accumulated other comprehensive (loss) income and retained earnings to recognize unrealized gains on equity securities. Shareholders Rights Agreement Our Amended and Restated Rights Agreement dated July 23, 2015 (“the 2015 Agreement”) 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 2015 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 2015 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. On April 26, 2018, our Board of Directors approved amendments to the 2015 Agreement described above (as amended and restated, the “2018 Agreement”). The only material amendment made to the 2015 Agreement was an extension of the final expiration date until March 1, 2020. The approval and effectiveness of the 2018 Agreement is subject to shareholder approval at the Annual Meeting of Shareholders, scheduled to be held in July 2018. Until such shareholder approval, the 2015 Rights Agreement remains in effect.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2018
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 . Table 14.1 shows the number of shares granted to employees and the weighted average fair value per share during the periods presented (shares in thousands). Table 14.1 Restricted stock grants Three months ended March 31, 2018 2017 Shares Granted Weighted Average Share Fair Value Shares Granted Weighted Average Share Fair Value RSUs subject to performance conditions 1,239 $ 15.80 1,237 $ 10.41 RSUs subject only to service conditions 412 15.71 395 10.41

Statutory Information

Statutory Information	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 , MGIC’s risk-to-capital ratio was 9.4 to 1 , below the maximum allowed by the jurisdictions with State Capital Requirements, and its policyholder position was $2.2 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 March 31, 2018 , the risk-to-capital ratio of our combined insurance operations (which includes a reinsurance affiliate) was 10.3 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. 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 a particular 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. Dividend restrictions In the first quarter of 2018, MGIC paid a $50 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 such dividends being subject to regulatory disapproval 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 principles prescribed, or practices 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 a change in underwriting deduction. As a result, in periods in which MGIC is increasing contingency reserves, statutory net income is lowered. For the year ended December 31, 2017 , MGIC’s statutory net income was reduced by $473 million to account for the increase in contingency reserves.

New Accounting Pronouncements (

New Accounting Pronouncements (Policies)	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Prospective Accounting Standards	Accounting standards effective in 2018, or early adopted, and relevant to our financial statements Table 2.1 shows the relevant amendments to accounting standards that have been implemented for the fiscal year beginning January 1, 2018; none had a material impact on our consolidated financial statements or disclosures. Table 2.1 Standard / Interpretation Effective date Amended Standards ASC 718 Compensation - Stock Compensation • ASU 2017-09 - Scope of Modification Accounting January 1, 2018 ASC 310 Receivables - Nonrefundable Fees and Other Costs • ASU 2017-08 - Premium Amortization on Purchased Callable Debt Securities January 1, 2019 ASC 715 Compensation - Retirement Benefits • ASU 2017-07 - Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost January 1, 2018 ASC 825 Financial Instruments - Overall • ASU 2016-01 - Recognition and Measurement of Financial Assets and Financial Liabilities January 1, 2018 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. ◦ Adoption impact: The adoption of this guidance had no 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. ◦ Adoption impact: We adopted this guidance as of January 1, 2018 with no impact to our consolidated financial statements or disclosures as our accounting practice adhered to the updated guidance. 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. ◦ Adoption impact: The adoption of this guidance had no impact on our consolidated financial statements or disclosures as the service cost component is reported in the same financial statement caption as other compensation costs and we do not present a subtotal of income outside of income from operations. The service cost component of our benefit plans is disclosed in Note 10 - “Benefit Plans” to our consolidated financial statements. 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. ◦ Adoption impact: The adoption of this guidance resulted in an immaterial cumulative effect adjustment to our 2018 beginning accumulated other comprehensive (loss) income and retained earnings to recognize unrealized gains on equity investments. At December 31, 2017, equity investments were classified as available-for-sale on the consolidated balance sheet. Upon adoption the updated guidance eliminated the available-for-sale balance sheet classification for equity securities. In February 2018, the FASB issued a separate update for technical corrections and improvements to clarify certain aspects of the guidance issued above. This update clarifies the presentation of investments in Federal Home Loan Bank stock and prohibits the investment from being shown with equity securities. ◦ Adoption impact: As of March 31, 2018, the value of our investment in Federal Home Loan Bank of Chicago (“FHLB”) stock, which is carried at cost, is presented within “Other invested assets” on our consolidated balance sheet. Prospective Accounting Standards Table 2.2 shows the relevant new amendments to accounting standards, which are not yet effective or adopted. Table 2.2 Standard / Interpretation Effective date Amended Standards ASC 326 Financial Instruments - Credit Losses • ASU 2016-13 - Measurement of Credit Losses on Financial Instruments January 1, 2020 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.

New Accounting Pronouncements N

New Accounting Pronouncements New Accounting Pronouncements (Tables)	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	Table 2.1 shows the relevant amendments to accounting standards that have been implemented for the fiscal year beginning January 1, 2018; none had a material impact on our consolidated financial statements or disclosures. Table 2.1 Standard / Interpretation Effective date Amended Standards ASC 718 Compensation - Stock Compensation • ASU 2017-09 - Scope of Modification Accounting January 1, 2018 ASC 310 Receivables - Nonrefundable Fees and Other Costs • ASU 2017-08 - Premium Amortization on Purchased Callable Debt Securities January 1, 2019 ASC 715 Compensation - Retirement Benefits • ASU 2017-07 - Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost January 1, 2018 ASC 825 Financial Instruments - Overall • ASU 2016-01 - Recognition and Measurement of Financial Assets and Financial Liabilities January 1, 2018
Schedule of Prospective Accounting Standards, Not Yet Effective Or Adopted	Table 2.2 shows the relevant new amendments to accounting standards, which are not yet effective or adopted. Table 2.2 Standard / Interpretation Effective date Amended Standards ASC 326 Financial Instruments - Credit Losses • ASU 2016-13 - Measurement of Credit Losses on Financial Instruments January 1, 2020

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-term debt	The par value of our long-term debt obligations and their aggregate carrying values as of March 31, 2018 and December 31, 2017 are presented in table 3.1 below. Table 3.1 Long-term debt obligations (In millions) March 31, December 31, FHLB Advance $ 155.0 $ 155.0 5.75% Notes 425.0 425.0 9% Debentures (1) 256.9 256.9 Long-term debt, par value 836.9 836.9 Debt issuance costs (6.2 ) (6.5 ) Long-term debt, carrying value $ 830.7 $ 830.4 (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	Table 3.2 below presents interest payments on our debt obligations. Table 3.2 Interest payments on debt obligations Three Months Ended March 31, (In millions) 2018 2017 Revolving credit facility $ 0.2 $ — FHLB Advance 0.7 0.7 5.75% Notes 12.2 12.9 Total interest payments $ 13.1 $ 13.6

Reinsurance (Tables)

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2018
Reinsurance Disclosures [Abstract]
Effect of reinsurance agreement	The effect of all of our reinsurance agreements on premiums earned and losses incurred is shown in table 4.1 below. Table 4.1 Reinsurance Three Months Ended March 31, (In thousands) 2018 2017 Premiums earned: Direct $ 265,251 $ 259,428 Assumed 121 98 Ceded (33,265 ) (30,423 ) Net premiums earned $ 232,107 $ 229,103 Losses incurred: Direct $ 31,501 $ 32,413 Assumed 90 105 Ceded (7,741 ) (4,899 ) Losses incurred, net $ 23,850 $ 27,619
Effect of quota share reinsurance agreements on premiums earned and losses incurred	Table 4.2 below presents a summary of our quota share reinsurance agreements, excluding captive agreements (which were immaterial), for the three months ended March 31, 2018 and 2017 . Table 4.2 Quota share reinsurance Three Months Ended March 31, (In thousands) 2018 2017 Ceded premiums written and earned, net of profit commission (1) $ 33,036 $ 28,895 Ceded losses incurred 7,788 4,687 Ceding commissions (2) 12,645 12,003 Profit commission 30,189 31,117 (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)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Calculation of earnings (loss) per share	Table 6.1 reconciles the numerators and denominators used to calculate basic and diluted EPS. Table 6.1 Earnings per share Three Months Ended March 31, (In thousands, except per share data) 2018 2017 Basic earnings per share: Net income $ 143,637 $ 89,798 Weighted average common shares outstanding - basic 370,908 341,009 Basic earnings per share $ 0.39 $ 0.26 Diluted earnings per share: Net income $ 143,637 $ 89,798 Interest expense, net of tax (1) : 2% Notes — 823 5% Notes — 1,282 9% Debentures 4,566 3,757 Diluted income available to common shareholders $ 148,203 $ 95,660 Weighted average common shares outstanding - basic 370,908 341,009 Effect of dilutive securities: Unvested RSUs 1,626 1,488 2% Notes — 29,859 5% Notes — 10,791 9% Debentures 19,028 19,028 Weighted average common shares outstanding - diluted 391,562 402,175 Diluted earnings per share $ 0.38 $ 0.24 (1) The three months ended March 31, 2018 and 2017 were tax effected at a rate of 21% and 35% , respectively.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Amortized cost, gross unrealized gains and losses and fair value of fixed income securities	The amortized cost, gross unrealized gains and losses, and fair value of investments in fixed income securities classified as available-for-sale at March 31, 2018 and December 31, 2017 are shown in tables 7.1a and 7.1b below. Table 7.1a Details of fixed income investments by category - current year March 31, 2018 (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 $ 191,018 $ 256 $ (2,212 ) $ 189,062 Obligations of U.S. states and political subdivisions 2,093,901 27,926 (19,130 ) 2,102,697 Corporate debt securities 2,087,977 1,921 (33,819 ) 2,056,079 Asset backed securities (“ABS”) 9,451 — (29 ) 9,422 Residential mortgage backed securities (“RMBS”) 182,050 48 (10,558 ) 171,540 Commercial mortgage backed securities (“CMBS”) 302,434 722 (9,800 ) 293,356 Collateralized loan obligations (“CLO”) 107,785 163 (41 ) 107,907 Total fixed income securities 4,974,616 31,036 (75,589 ) 4,930,063 Table 7.1b Details of fixed income investments by category - prior year-end December 31, 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 $ 179,850 $ 274 $ (1,278 ) $ 178,846 Obligations of U.S. states and political subdivisions 2,105,063 56,210 (8,749 ) 2,152,524 Corporate debt securities 2,065,475 10,532 (9,169 ) 2,066,838 ABS 4,925 — (2 ) 4,923 RMBS 189,153 60 (7,364 ) 181,849 CMBS 301,014 1,204 (4,906 ) 297,312 CLOs 100,798 304 (79 ) 101,023 Total fixed income securities 4,946,278 68,584 (31,547 ) 4,983,315 (1) At March 31, 2018 and December 31, 2017 , 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 fixed income securities at March 31, 2018 , by contractual maturity, are shown in table 7.2 below. 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 ABS, RMBS, CMBS, and CLOs provide for periodic payments throughout their lives, they are listed in separate categories. Table 7.2 Fixed income securities maturity schedule March 31, 2018 (In thousands) Amortized Cost Fair Value Due in one year or less $ 650,415 $ 649,088 Due after one year through five years 1,507,245 1,487,678 Due after five years through ten years 909,711 893,329 Due after ten years 1,305,525 1,317,743 $ 4,372,896 $ 4,347,838 ABS 9,451 9,422 RMBS 182,050 171,540 CMBS 302,434 293,356 CLOs 107,785 107,907 Total as of March 31, 2018 $ 4,974,616 $ 4,930,063
Cost and fair value of investments in equity securities	The cost and fair value of investments in equity securities at March 31, 2018 and December 31, 2017 are shown in tables 7.3a and 7.3b below. As described in Note 2 - “New Accounting Pronouncements,” updated guidance regarding the “ Recognition and Measurement of Financial Assets and Financial Liabilities” became effective on January 1, 2018, which prohibits our investment in FHLB stock from being presented with equity securities. The amount of our FHLB stock investment has been reclassified and presented in “Other invested assets” on our consolidated balance sheet as of March 31, 2018. Table 7.3a Details of equity security investments - current year March 31, 2018 (In thousands) Cost Gross Gains Gross Losses Fair Value Equity securities $ 4,143 $ 8 $ (52 ) $ 4,099 Table 7.3b Details of equity security investments - prior year-end December 31, 2017 (In thousands) Cost Gross Gains Gross Losses Fair Value Equity securities $ 7,223 $ 39 $ (16 ) $ 7,246
Aging of the fair values of securities in an unrealized loss position	Tables 7.4a and 7.4b below summarize, for all available-for-sale investments in an unrealized loss position at March 31, 2018 and December 31, 2017 , the aggregate fair value and gross unrealized loss by the length of time those securities have been continuously in an unrealized loss position. The fair value amounts reported in tables 7.4a and 7.4b are estimated using the process described in Note 8 - “Fair Value Measurements” to these consolidated financial statements and in Note 3 - “Significant Accounting Policies” of the notes to the consolidated financial statements in our 2017 Annual Report on Form 10-K. Table 7.4a Investments unrealized losses - current year March 31, 2018 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 $ 77,510 $ (1,532 ) $ 31,491 $ (680 ) $ 109,001 $ (2,212 ) Obligations of U.S. states and political subdivisions 905,755 (11,622 ) 201,094 (7,508 ) 1,106,849 (19,130 ) Corporate debt securities 1,743,627 (26,797 ) 148,468 (7,022 ) 1,892,095 (33,819 ) ABS 9,423 (29 ) — — 9,423 (29 ) RMBS 14,226 (416 ) 156,842 (10,142 ) 171,068 (10,558 ) CMBS 114,206 (2,162 ) 126,941 (7,638 ) 241,147 (9,800 ) CLOs — — 1,936 (41 ) 1,936 (41 ) Total $ 2,864,747 $ (42,558 ) $ 666,772 $ (33,031 ) $ 3,531,519 $ (75,589 ) Table 7.4b Investments unrealized losses - prior year-end December 31, 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 $ 144,042 $ (796 ) $ 31,196 $ (482 ) $ 175,238 $ (1,278 ) Obligations of U.S. states and political subdivisions 505,311 (3,624 ) 211,684 (5,125 ) 716,995 (8,749 ) Corporate debt securities 932,350 (4,288 ) 200,716 (4,881 ) 1,133,066 (9,169 ) ABS 4,923 (2 ) — — 4,923 (2 ) RMBS 14,979 (280 ) 166,329 (7,084 ) 181,308 (7,364 ) CMBS 51,096 (358 ) 138,769 (4,548 ) 189,865 (4,906 ) CLOs 14,243 (7 ) 3,568 (72 ) 17,811 (79 ) Equity securities 226 (2 ) 431 (14 ) 657 (16 ) Total $ 1,667,170 $ (9,357 ) $ 752,693 $ (22,206 ) $ 2,419,863 $ (31,563 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair value measurements for items measured at fair value	Assets measured at fair value, by hierarchy level, as of March 31, 2018 and December 31, 2017 as shown in tables 8.1a and 8.1b below are estimated using the process described above, and more fully in Note 3 - “Significant Accounting Policies” of the notes to the consolidated financial statements in our 2017 Annual Report on Form 10-K. Table 8.1a Fair value hierarchy - current year March 31, 2018 (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 $ 189,062 $ 81,418 $ 107,644 $ — Obligations of U.S. states and political subdivisions 2,102,697 — 2,102,443 254 Corporate debt securities 2,056,079 — 2,056,079 — ABS 9,422 — 9,422 — RMBS 171,540 — 171,540 — CMBS 293,356 — 293,356 — CLOs 107,907 — 107,907 — Total fixed income securities 4,930,063 81,418 4,848,391 254 Equity securities (1) 4,099 2,931 — 1,168 Total investments at fair value $ 4,934,162 $ 84,349 $ 4,848,391 $ 1,422 Real estate acquired (2) $ 10,078 $ — $ — $ 10,078 (1) Equity securities in Level 3 are carried at cost, which approximates fair value. See “Reconciliations of Level 3 assets” below for information regarding a change in presentation of amounts previously included in Level 3 Equity securities. (2) Real estate acquired through claim settlement, which is held for sale, is reported in Other assets on the consolidated balance sheets. Table 8.1b Fair value hierarchy - prior year-end December 31, 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 $ 178,846 $ 81,598 $ 97,248 $ — Obligations of U.S. states and political subdivisions 2,152,524 — 2,152,253 271 Corporate debt securities 2,066,838 — 2,066,838 — ABS 4,923 — 4,923 — RMBS 181,849 — 181,849 — CMBS 297,312 — 297,312 — CLOs 101,023 — 101,023 — Total fixed income securities 4,983,315 81,598 4,901,446 271 Equity securities (1) 7,246 2,978 — 4,268 Total investments at fair value $ 4,990,561 $ 84,576 $ 4,901,446 $ 4,539 Real estate acquired (2) $ 12,713 $ — $ — $ 12,713 (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 months ended March 31, 2018 and 2017 is shown in tables 8.2a and 8.2b below. As described in Note 2 - “New Accounting Pronouncements,” updated guidance regarding the Recognition and Measurement of Financial Assets and Financial Liabilities became effective on January 1, 2018, which requires that our investment in FHLB stock not be presented with equity securities. Prior to the updated guidance, our FHLB stock was included in our Level 3 equity securities. As shown in table 8.2a below, for the three months ended March 31, 2018, we have transferred our FHLB stock out of Level 3 assets, and they are carried at cost, which approximates fair value on our consolidated balance sheet as of March 31, 2018. The amount of FHLB stock is presented in “Other invested assets” as of March 31, 2018. 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. Table 8.2a Development of assets and liabilities classified within level 3 - current year quarter Three Months Ended March 31, 2018 (In thousands) Debt Securities Equity Securities Total Investments Real Estate Acquired Balance at December 31, 2017 $ 271 $ 4,268 $ 4,539 $ 12,713 Transfers out of Level 3 — (3,100 ) (3,100 ) — Total realized/unrealized gains (losses): Included in earnings and reported as losses incurred, net — — — 341 Purchases — — — 5,894 Sales (17 ) — (17 ) (8,870 ) Balance at March 31, 2018 $ 254 $ 1,168 $ 1,422 $ 10,078 Table 8.2b Development of assets and liabilities classified within level 3 - prior year quarter Three Months Ended March 31, 2017 (In thousands) Debt Equity Total Real Estate 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 — — — (163 ) Purchases — — — 8,683 Sales (8 ) — (8 ) (9,538 ) Balance at March 31, 2017 $ 683 $ 4,268 $ 4,951 $ 10,730
Carrying value and fair value of debt	Table 8.3 presents the carrying value and fair value of our financial liabilities disclosed, but not carried, at fair value at March 31, 2018 and December 31, 2017 . The fair values of our 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. Table 8.3 Fair value measurements - liabilities March 31, 2018 December 31, 2017 (In thousands) Carrying Value Fair Value Carrying Value Fair Value FHLB Advance 155,000 149,756 $ 155,000 $ 152,124 5.75% Notes 418,848 446,730 418,560 465,473 9% Debentures 256,872 350,897 256,872 353,507 Total financial liabilities $ 830,720 $ 947,383 $ 830,432 $ 971,104

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2018
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 months ended March 31, 2018 and 2017 are included in table 9.1 below. Table 9.1 Components of other comprehensive (loss) income Three Months Ended March 31, (In thousands) 2018 2017 Net unrealized investment (losses) gains arising during the period $ (81,587 ) $ 18,647 Income tax benefit (expense) 17,134 (6,526 ) Net of taxes (64,453 ) 12,121 Net changes in benefit plan assets and obligations 625 (234 ) Income tax (expense) benefit (131 ) 81 Net of taxes 494 (153 ) Net changes in unrealized foreign currency translation adjustment — 45 Income tax (expense) — (14 ) Net of taxes — 31 Total other comprehensive (loss) income (80,962 ) 18,458 Total income tax benefit (expense) 17,003 (6,459 ) Total other comprehensive (loss) income, net of tax $ (63,959 ) $ 11,999
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 months ended March 31, 2018 and 2017 are included in table 9.2 below. Table 9.2 Reclassifications from AOCL Three Months Ended March 31, (In thousands) 2018 2017 Reclassification adjustment for net realized (losses) gains (1) $ (91 ) $ (747 ) Income tax benefit 19 261 Net of taxes (72 ) (486 ) Reclassification adjustment related to benefit plan assets and obligations (2) (625 ) 234 Income tax benefit (expense) 131 (81 ) Net of taxes (494 ) 153 Total reclassifications (716 ) (513 ) Total income tax benefit 150 180 Total reclassifications, net of tax $ (566 ) $ (333 ) (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.
Accumulated other comprehensive income (loss)	A rollforward of AOCL for the three months ended March 31, 2018 , including amounts reclassified from AOCL, are included in table 9.3 below. Table 9.3 Rollforward of AOCL Three Months Ended March 31, 2018 (In thousands) Net unrealized gains and losses on available-for-sale securities Net benefit plan assets and obligations recognized in shareholders' equity Total AOCL Balance, December 31, 2017, net of tax $ 29,257 $ (73,058 ) $ (43,801 ) Other comprehensive income before reclassifications (64,525 ) — (64,525 ) Less: Amounts reclassified from AOCL (72 ) (494 ) (566 ) Balance, March 31, 2018, net of tax $ (35,196 ) $ (72,564 ) $ (107,760 )

Benefit Plans (Tables)

Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Components of net periodic benefit cost	Table 10.1 provides the components of net periodic benefit cost for our pension, supplemental executive retirement and other postretirement benefit plans for the three months ended March 31, 2018 and 2017 . Table 10.1 Components of net periodic benefit cost Three Months Ended March 31, Pension and Supplemental Executive Retirement Plans Other Postretirement Benefit Plans (In thousands) 2018 2017 2018 2017 Service cost $ 2,562 $ 2,294 $ 270 $ 187 Interest cost 3,782 3,858 214 167 Expected return on plan assets (5,570 ) (5,036 ) (1,588 ) (1,312 ) Recognized net actuarial loss 1,785 1,535 (46 ) — Amortization of prior service cost (87 ) (107 ) (1,026 ) (1,662 ) Net periodic benefit cost (benefit) $ 2,472 $ 2,544 $ (2,176 ) $ (2,620 )

Loss Reserves (Tables)

Loss Reserves (Tables)	3 Months Ended
	Mar. 31, 2018
Insurance Loss Reserves [Abstract]
Reconciliation of beginning and ending loss reserves	Table 12.1 provides a reconciliation of beginning and ending loss reserves as of and for the three months ended March 31, 2018 and 2017 . Table 12.1 Development of reserves for losses and loss adjustment expenses Three Months Ended March 31, (In thousands) 2018 2017 Reserve at beginning of period $ 985,635 $ 1,438,813 Less reinsurance recoverable 48,474 50,493 Net reserve at beginning of period 937,161 1,388,320 Losses incurred: Losses and LAE incurred in respect of delinquency notices received in: Current year 59,070 80,416 Prior years (1) (35,220 ) (52,797 ) Total losses incurred 23,850 27,619 Losses paid: Losses and LAE paid in respect of delinquency notices received in: Current year 95 331 Prior years 81,983 127,224 Reinsurance terminations 236 — Total losses paid 82,314 127,555 Net reserve at end of period 878,697 1,288,384 Plus reinsurance recoverables 45,474 46,658 Reserve at end of period $ 924,171 $ 1,335,042 (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.
Prior year development of the reserves	The prior year development of the reserves in the first three months of 2018 and 2017 is reflected in table 12.2 below. Table 12.2 Reserve development on previously received delinquencies Three Months Ended March 31, (in millions) 2018 2017 Decrease in estimated claim rate on primary defaults $ (47 ) $ (54 ) Increase in estimated severity on primary defaults 16 4 Change in estimates related to pool reserves, LAE reserves and reinsurance (4 ) (3 ) Total prior year loss development (1) $ (35 ) $ (53 ) (1) A negative number for prior year loss development indicates a redundancy of prior year loss reserves.
Rollforward of primary delinquent inventory	A rollforward of our primary delinquent inventory for the three months ended March 31, 2018 and 2017 appears in table 12.3 below. 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. Table 12.3 Delinquent inventory rollforward Three Months Ended March 31, 2018 2017 Delinquent inventory at beginning of period 46,556 50,282 New notices 14,623 14,939 Cures (18,073 ) (17,128 ) Paids (including those charged to a deductible or captive) (1,571 ) (2,635 ) Rescissions and denials (68 ) (95 ) Other items removed from inventory (224 ) (14 ) Delinquent inventory at end of period 41,243 45,349
Aging of the primary delinquent inventory	Table 12.4 below shows the number of consecutive months a borrower is delinquent. Table 12.4 Delinquent inventory - consecutive months in default March 31, 2018 December 31, 2017 March 31, 2017 3 months or less 8,770 21 % 17,119 37 % 9,184 20 % 4-11 months 16,429 40 % 12,050 26 % 13,617 30 % 12 months or more (1) (2) 16,044 39 % 17,387 37 % 22,548 50 % Total primary delinquent inventory 41,243 100 % 46,556 100 % 45,349 100 % Primary claims received inventory included in ending delinquent inventory: 819 2 % 954 2 % 1,390 3 % (1) Approximately 44% , 45% , and 48% of the primary delinquent inventory delinquent for 12 consecutive months or more has been delinquent for at least 36 consecutive months as of March 31, 2018 , December 31, 2017 , and March 31, 2017 , respectively. (2) The majority of items removed from our delinquent inventory were due to commutations of NPLs during the three months ended March 31, 2018 were delinquent for 12 consecutive months or more as of December 31, 2017.
Number of payments delinquent	Table 12.5 below shows the number of payments that a borrower is delinquent. Table 12.5 Delinquent inventory - number of payments delinquent March 31, 2018 December 31, 2017 March 31, 2017 3 payments or less 16,023 39 % 21,678 46 % 15,692 35 % 4-11 payments 13,734 33 % 12,446 27 % 12,275 27 % 12 payments or more (1) (2) 11,486 28 % 12,432 27 % 17,382 38 % Total primary delinquent inventory 41,243 100 % 46,556 100 % 45,349 100 % (1) Approximately 42% , 43% , and 45% of the primary delinquent inventory with 12 payments or more delinquent has at least 36 payments delinquent as of March 31, 2018 , December 31, 2017 , and March 31, 2017 , respectively. (2) The majority of items removed from our delinquent inventory were due to commutations of NPLs during the three months ended March 31, 2018 had 12 or more payments delinquent as of December 31, 2017.

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of stock-based compensation, activity	Table 14.1 shows the number of shares granted to employees and the weighted average fair value per share during the periods presented (shares in thousands). Table 14.1 Restricted stock grants Three months ended March 31, 2018 2017 Shares Granted Weighted Average Share Fair Value Shares Granted Weighted Average Share Fair Value RSUs subject to performance conditions 1,239 $ 15.80 1,237 $ 10.41 RSUs subject only to service conditions 412 15.71 395 10.41

Nature of Business and Basis 34

Nature of Business and Basis of Presentation Nature of Business and Basis of Presentation (Details)	Apr. 26, 2018USD ($)
Subsequent event
Subsequent Event [Line Items]
Stock repurchase program, authorized amount	$ 200,000,000

Debt - Summary of Debt Obligati

Debt - Summary of Debt Obligations (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, par value	$ 836.9	$ 836.9
Debt issuance costs	(6.2)	(6.5)
Long-term debt, carrying value	830.7	830.4
FHLB Advance
Debt Instrument [Line Items]
Long-term debt, par value	155	155
Senior Notes | 5.75% Senior Notes Due 2023
Debt Instrument [Line Items]
Long-term debt, par value	$ 425	425
Stated interest rate	5.75%
9% Debentures
Debt Instrument [Line Items]
Long-term debt, par value	$ 256.9	$ 256.9
Stated interest rate	9.00%

Debt - Narrative (Details)

Debt - Narrative (Details)	3 Months Ended
	Mar. 31, 2018$ / shares
9% Debentures
Debt Instrument [Line Items]
Conversion rate (in shares per $1,000 note)	0.0740741
Convertible debt, conversion price (in dollars per share)	$ 13.50
Period preceding election to convert (in days)	5 days
Stated interest rate	9.00%
Senior Notes | 5.75% Senior Notes Due 2023
Debt Instrument [Line Items]
Stated interest rate	5.75%

Debt - Summary of Interest Paid

Debt - Summary of Interest Paid (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Debt Instrument [Line Items]
Total interest payments	$ 13.1	$ 13.6
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Total interest payments	0.2	0
FHLB Advance
Debt Instrument [Line Items]
Total interest payments	0.7	0.7
Senior Notes | 5.75% Senior Notes Due 2023
Debt Instrument [Line Items]
Total interest payments	$ 12.2	$ 12.9
Stated interest rate	5.75%

Reinsurance - Summary of Premiu

Reinsurance - Summary of Premiums Earned and Losses Incurred (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Premiums earned:
Direct	$ 265,251	$ 259,428
Assumed	121	98
Ceded	(33,265)	(30,423)
Net premiums earned	232,107	229,103
Losses incurred:
Direct	31,501	32,413
Assumed	90	105
Ceded	(7,741)	(4,899)
Losses incurred, net	$ 23,850	$ 27,619

Reinsurance - Narrative (Detail

Reinsurance - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Effects of Reinsurance [Line Items]
Reinsurance recoverable on loss reserves	$ 45,474,000	$ 48,474,000	$ 46,658,000	$ 50,493,000
Quota Share Reinsurance Agreement, 2018
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)	62.00%
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	$ 43,500,000	$ 39,300,000

Reinsurance - Summary of Quota

Reinsurance - Summary of Quota Reinsurance Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Effects of Reinsurance [Line Items]
Ceded losses incurred	$ 7,741	$ 4,899
Quota Share Reinsurance Agreements, Excluding Captive Agreements
Effects of Reinsurance [Line Items]
Ceded premiums written and earned, net of profit commission	33,036	28,895
Ceded losses incurred	7,788	4,687
Ceding commissions	12,645	12,003
Profit commission	$ 30,189	$ 31,117

Litigation and Contingencies (D

Litigation and Contingencies (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Average paid claim reduction due to curtailments (as a percent)	7.30%	5.60%
Maximum exposure associated with other discussions and legal proceedings	$ 282

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic earnings per share:
Net income	$ 143,637	$ 89,798
Weighted average common shares outstanding - basic (in shares)	370,908	341,009
Basic earnings per share (in dollars per share)	$ 0.39	$ 0.26
Diluted earnings per share:
Net income	$ 143,637	$ 89,798
Diluted income available to common shareholders	$ 148,203	$ 95,660
Weighted average common shares outstanding - basic (in shares)	370,908	341,009
Effect of dilutive securities:
Weighted average common shares outstanding - diluted (in shares)	391,562	402,175
Diluted earnings per share (in dollars per share)	$ 0.38	$ 0.24
Effective income tax rate	21.00%	35.00%
9% Debentures
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate	9.00%
2% Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate		2.00%
Diluted earnings per share:
Dilutive securities	$ 0	$ 823
Effect of dilutive securities:
Dilutive securities (in shares)	0	29,859
5% Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate		5.00%
Diluted earnings per share:
Dilutive securities	$ 0	$ 1,282
Effect of dilutive securities:
Dilutive securities (in shares)	0	10,791
9% Debentures
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate	9.00%
Diluted earnings per share:
Dilutive securities	$ 4,566	$ 3,757
Effect of dilutive securities:
Dilutive securities (in shares)	19,028	19,028
Unvested RSUs
Effect of dilutive securities:
Unvested RSUs (in shares)	1,626	1,488

Investments (Details)

Investments (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)security	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)security
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 4,974,616,000		$ 4,946,278,000
Fair Value	4,930,063,000		4,983,315,000
Other than Temporary Impairment Losses, Portion in Other Comprehensive Income	0		$ 0
Proceeds from sales of fixed income securities	10,844,000	$ 33,980,000
Gross realized gains	100,000	200,000
Gross realized losses	$ 300,000	300,000
Number of securities in unrealized loss position (in securities) | security	788		586
Net impairment losses recognized in earnings	$ 0	$ 0
Federal Home Loan Bank advances, collateral, value of principal, percent (as a percent)	102.00%
FHLB advance collateral	$ 165,600,000
Total fixed income securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,974,616,000		$ 4,946,278,000
Gross Unrealized Gains	31,036,000		68,584,000
Gross Unrealized Losses	(75,589,000)		(31,547,000)
Fair Value	4,930,063,000		4,983,315,000
U.S. Treasury securities and obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	191,018,000		179,850,000
Gross Unrealized Gains	256,000		274,000
Gross Unrealized Losses	(2,212,000)		(1,278,000)
Fair Value	189,062,000		178,846,000
Obligations of U.S. states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,093,901,000		2,105,063,000
Gross Unrealized Gains	27,926,000		56,210,000
Gross Unrealized Losses	(19,130,000)		(8,749,000)
Fair Value	2,102,697,000		2,152,524,000
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,087,977,000		2,065,475,000
Gross Unrealized Gains	1,921,000		10,532,000
Gross Unrealized Losses	(33,819,000)		(9,169,000)
Fair Value	2,056,079,000		2,066,838,000
Asset backed securities (“ABS”)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,451,000		4,925,000
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(29,000)		(2,000)
Fair Value	9,422,000		4,923,000
Residential mortgage backed securities (“RMBS”)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	182,050,000		189,153,000
Gross Unrealized Gains	48,000		60,000
Gross Unrealized Losses	(10,558,000)		(7,364,000)
Fair Value	171,540,000		181,849,000
Commercial mortgage backed securities (“CMBS”)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	302,434,000		301,014,000
Gross Unrealized Gains	722,000		1,204,000
Gross Unrealized Losses	(9,800,000)		(4,906,000)
Fair Value	293,356,000		297,312,000
Collateralized loan obligations (“CLO”)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	107,785,000		100,798,000
Gross Unrealized Gains	163,000		304,000
Gross Unrealized Losses	(41,000)		(79,000)
Fair Value	$ 107,907,000		$ 101,023,000

Investments - Amortized Cost an

Investments - Amortized Cost and Fair Values of Debt Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less	$ 650,415
Due after one year through five years	1,507,245
Due after five years through ten years	909,711
Due after ten years	1,305,525
Total debt securities with single maturity date, amortized cost	4,372,896
Amortized Cost	4,974,616	$ 4,946,278
Fair Value
Due in one year or less	649,088
Due after one year through five years	1,487,678
Due after five years through ten years	893,329
Due after ten years	1,317,743
Total debt securities with single maturity date, fair value	4,347,838
Total at end of period	4,930,063	$ 4,983,315
Asset backed securities (“ABS”)
Amortized Cost
Total debt securities without single maturity date, amortized cost	9,451
Fair Value
Total debt securities without single maturity date, fair value	9,422
Residential mortgage backed securities (“RMBS”)
Amortized Cost
Total debt securities without single maturity date, amortized cost	182,050
Fair Value
Total debt securities without single maturity date, fair value	171,540
Commercial mortgage backed securities (“CMBS”)
Amortized Cost
Total debt securities without single maturity date, amortized cost	302,434
Fair Value
Total debt securities without single maturity date, fair value	293,356
Collateralized loan obligations (“CLO”)
Amortized Cost
Total debt securities without single maturity date, amortized cost	107,785
Fair Value
Total debt securities without single maturity date, fair value	$ 107,907

Investments - Securities In Unr

Investments - Securities In Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	$ 2,864,747
12 Months or Greater	666,772
Total	3,531,519
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	(42,558)
12 Months or Greater	(33,031)
Total	(75,589)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		$ 1,667,170
12 Months or Greater		752,693
Total		2,419,863
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(9,357)
12 Months or Greater		(22,206)
Total		(31,563)
U.S. Treasury securities and obligations of U.S. government corporations and agencies
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	77,510
12 Months or Greater	31,491
Total	109,001
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	(1,532)
12 Months or Greater	(680)
Total	(2,212)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		144,042
12 Months or Greater		31,196
Total		175,238
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(796)
12 Months or Greater		(482)
Total		(1,278)
Obligations of U.S. states and political subdivisions
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	905,755
12 Months or Greater	201,094
Total	1,106,849
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	(11,622)
12 Months or Greater	(7,508)
Total	(19,130)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		505,311
12 Months or Greater		211,684
Total		716,995
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(3,624)
12 Months or Greater		(5,125)
Total		(8,749)
Corporate debt securities
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	1,743,627
12 Months or Greater	148,468
Total	1,892,095
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	(26,797)
12 Months or Greater	(7,022)
Total	(33,819)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		932,350
12 Months or Greater		200,716
Total		1,133,066
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(4,288)
12 Months or Greater		(4,881)
Total		(9,169)
Asset backed securities (“ABS”)
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	9,423
12 Months or Greater	0
Total	9,423
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	(29)
12 Months or Greater	0
Total	(29)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		4,923
12 Months or Greater		0
Total		4,923
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(2)
12 Months or Greater		0
Total		(2)
Residential mortgage backed securities (“RMBS”)
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	14,226
12 Months or Greater	156,842
Total	171,068
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	(416)
12 Months or Greater	(10,142)
Total	(10,558)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		14,979
12 Months or Greater		166,329
Total		181,308
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(280)
12 Months or Greater		(7,084)
Total		(7,364)
Commercial mortgage backed securities (“CMBS”)
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	114,206
12 Months or Greater	126,941
Total	241,147
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	(2,162)
12 Months or Greater	(7,638)
Total	(9,800)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		51,096
12 Months or Greater		138,769
Total		189,865
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(358)
12 Months or Greater		(4,548)
Total		(4,906)
Collateralized loan obligations (“CLO”)
Continuous Unrealized Loss Portion, Fair Value [Abstract]
Less Than 12 Months	0
12 Months or Greater	1,936
Total	1,936
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract]
Less Than 12 Months	0
12 Months or Greater	(41)
Total	$ (41)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		14,243
12 Months or Greater		3,568
Total		17,811
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(7)
12 Months or Greater		(72)
Total		(79)
Equity securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months		226
12 Months or Greater		431
Total		657
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract]
Less Than 12 Months		(2)
12 Months or Greater		(14)
Total		$ (16)

Investments Investments - Equit

Investments Investments - Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Equity Securities, FV-NI, Gain (Loss) [Abstract]
Cost	$ 4,143
Gross Gains	8
Gross Losses	(52)
Fair Value	4,099
Recognized net losses on equity securities sill held	$ 100
Unrealized Gain (Loss) on Equity Securities [Abstract]
Cost		$ 7,223
Gross Gains		39
Gross Losses		(16)
Fair Value		$ 7,246

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
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	$ 189,062	$ 178,846
Obligations of U.S. states and political subdivisions	2,102,697	2,152,524
Corporate debt securities	2,056,079	2,066,838
ABS	9,422	4,923
RMBS	171,540	181,849
CMBS	293,356	297,312
CLOs	107,907	101,023
Total fixed income securities	4,930,063	4,983,315
Equity securities	4,099	7,246
Total investments at fair value	4,934,162	4,990,561
Real estate acquired	10,078	12,713
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	81,418	81,598
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 fixed income securities	81,418	81,598
Equity securities	2,931	2,978
Total investments at fair value	84,349	84,576
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	107,644	97,248
Obligations of U.S. states and political subdivisions	2,102,443	2,152,253
Corporate debt securities	2,056,079	2,066,838
ABS	9,422	4,923
RMBS	171,540	181,849
CMBS	293,356	297,312
CLOs	107,907	101,023
Total fixed income securities	4,848,391	4,901,446
Equity securities	0	0
Total investments at fair value	4,848,391	4,901,446
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	254	271
Corporate debt securities	0	0
ABS	0	0
RMBS	0	0
CMBS	0	0
CLOs	0	0
Total fixed income securities	254	271
Equity securities	1,168	4,268
Total investments at fair value	1,422	4,539
Real estate acquired	$ 10,078	$ 12,713

Fair Value Measurements - Unobs

Fair Value Measurements - Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Total Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 4,539	$ 4,959
Transfers out of Level 3	(3,100)
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	0	0
Purchases	0	0
Sales	(17)	(8)
Balance at end of period	1,422	4,951
Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	271	691
Transfers out of Level 3	0
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	0	0
Purchases	0	0
Sales	(17)	(8)
Balance at end of period	254	683
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	4,268	4,268
Transfers out of Level 3	(3,100)
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	0	0
Purchases	0	0
Sales	0	0
Balance at end of period	1,168	4,268
Real Estate Acquired
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	12,713	11,748
Transfers out of Level 3	0
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	341	(163)
Purchases	5,894	8,683
Sales	(8,870)	(9,538)
Balance at end of period	$ 10,078	$ 10,730

Fair Value Measurements - Liabi

Fair Value Measurements - Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Senior Notes | 5.75% Senior Notes Due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate	5.75%
9% Debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate	9.00%
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FHLB Advance	$ 155,000	$ 155,000
5.75% Notes	418,848	418,560
9% Debentures	256,872	256,872
Total financial liabilities	830,720	830,432
Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FHLB Advance	149,756	152,124
5.75% Notes	446,730	465,473
9% Debentures	350,897	353,507
Total financial liabilities	$ 947,383	$ 971,104

Other Comprehensive Income (Det

Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive (loss) income	$ (80,962)	$ 18,458
Income tax benefit (expense)	17,003	(6,459)
Other comprehensive (loss) income, net of tax	(63,959)	11,999
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Net realized investment losses	(329)	(125)
Other underwriting and operating expenses, net	(46,090)	(40,765)
Income before tax	180,025	173,957
Income tax benefit (expense)	(36,388)	(84,159)
Net income	143,637	89,798
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	3,154,526
Other comprehensive income before reclassifications	(64,525)
Less: Amounts reclassified from AOCL	(566)
Balance, end of period	3,231,403	2,647,531
Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Income before tax	(716)	(513)
Income tax benefit (expense)	150	180
Net income	(566)	(333)
Accumulated other comprehensive (loss) income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive (loss) income, net of tax	(63,959)	11,999
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(43,801)	(75,100)
Balance, end of period	(107,760)	(63,101)
Net unrealized gains and losses on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive (loss) income	(81,587)	18,647
Income tax benefit (expense)	17,134	(6,526)
Other comprehensive (loss) income, net of tax	(64,453)	12,121
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	29,257
Other comprehensive income before reclassifications	(64,525)
Less: Amounts reclassified from AOCL	(72)
Balance, end of period	(35,196)
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	(91)	(747)
Income tax benefit (expense)	19	261
Net income	(72)	(486)
Net benefit plan assets and obligations recognized in shareholders' equity
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive (loss) income	625	(234)
Income tax benefit (expense)	(131)	81
Other comprehensive (loss) income, net of tax	494	(153)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(73,058)
Other comprehensive income before reclassifications	0
Less: Amounts reclassified from AOCL	(494)
Balance, end of period	(72,564)
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	(625)	234
Income tax benefit (expense)	131	(81)
Net income	(494)	153
Net unrealized foreign currency translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive (loss) income	0	45
Income tax benefit (expense)	0	(14)
Other comprehensive (loss) income, net of tax	$ 0	$ 31

Benefit Plans (Details)

Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension and Supplemental Executive Retirement Plans
Components of Net Periodic Benefit Cost [Abstract]
Service cost	$ 2,562	$ 2,294
Interest cost	3,782	3,858
Expected return on plan assets	(5,570)	(5,036)
Recognized net actuarial loss	1,785	1,535
Amortization of prior service cost	(87)	(107)
Net periodic benefit cost (benefit)	2,472	2,544
Estimated future employer contributions in current fiscal year	11,000
Other Postretirement Benefit Plans
Components of Net Periodic Benefit Cost [Abstract]
Service cost	270	187
Interest cost	214	167
Expected return on plan assets	(1,588)	(1,312)
Recognized net actuarial loss	(46)	0
Amortization of prior service cost	(1,026)	(1,662)
Net periodic benefit cost (benefit)	$ (2,176)	$ (2,620)

Income Taxes (Details)

Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2007	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Net operating loss carryforwards		$ 585,700,000
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		209,700,000
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		87,400,000
Total amount of unrecognized tax benefits		143,700,000
Total amount of the unrecognized tax benefits that would affect our effective tax rate		125,000,000
Unrecognized tax benefits, accrued interest		$ 52,900,000	$ 52,000,000

Loss Reserves - Reconciliation

Loss Reserves - Reconciliation of Beginning and Ending Balances (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Loss Reserve [Roll Forward]
Reserve at beginning of period	$ 985,635	$ 1,438,813
Less reinsurance recoverable	48,474	50,493
Net reserve at beginning of period	937,161	1,388,320
Losses and LAE incurred in respect of delinquency notices received in:
Current year	59,070	80,416
Prior years	(35,220)	(52,797)
Total losses incurred	23,850	27,619
Losses and LAE paid in respect of delinquency notices received in:
Current year	95	331
Prior years	81,983	127,224
Reinsurance terminations	236	0
Total losses paid	82,314	127,555
Net reserve at end of period	878,697	1,288,384
Plus reinsurance recoverables	45,474	46,658
Reserve at end of period	$ 924,171	$ 1,335,042

Loss Reserves (Details)

Loss Reserves (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)loan	Dec. 31, 2017USD ($)loan	Mar. 31, 2017USD ($)loan
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Percentage of prior year delinquent inventory resolved (as a percent)	31.00%		29.00%
Prior years | $	$ 81,983		$ 127,224
Premium refund liability, expected claim payments | $	56,000	$ 61,000
Prior years | $	$ (35,220)		$ (52,797)
Default notices for loans in IADAs (in loans)		9,294
Primary Delinquent Inventory [Roll Forward]
Delinquent inventory at the beginning of period (in loans)	46,556		50,282
New notices (in loans)	14,623		14,939
Cures (in loans)	(18,073)		(17,128)
Paids (including those charged to a deductible or captive) (in loans)	(1,571)		(2,635)
Rescissions and denials (in loans)	(68)		(95)
Other items removed from inventory (in loans)	(224)		(14)
Delinquent inventory at end of period (in loans)	41,243	46,556	45,349
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 | $	$ 7,000
Decrease in estimated claim rate on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $	(47,000)		$ (54,000)
Increase in estimated severity on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $	16,000		4,000
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 | $	$ (4,000)		$ (3,000)

Loss Reserves - Delinquent Item

Loss Reserves - Delinquent Items (Details) - loan	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Aging of the Primary Delinquent Inventory [Abstract]
3 months or less (in loans)	8,770	17,119	9,184
3 months or less (as a percent)	21.00%	37.00%	20.00%
4 - 11 months (in loans)	16,429	12,050	13,617
4 - 11 months (as a percent)	40.00%	26.00%	30.00%
12 months or more (in loans)	16,044	17,387	22,548
12 months or more (as a percent)	39.00%	37.00%	50.00%
Total primary delinquent inventory (in loans)	41,243	46,556	45,349	50,282
Total primary delinquent inventory (as a percent)	100.00%	100.00%	100.00%
Primary claims received inventory included in ending delinquent inventory (in loans)	819	954	1,390
Primary claims received inventory included in ending delinquent inventory (as a percent)	2.00%	2.00%	3.00%
Percent of 12 months or more delinquent inventory, delinquent for more than 36 months (as a percent)	44.00%	45.00%	48.00%
Number of payments delinquent [Abstract]
3 payments or less (in loans)	16,023	21,678	15,692
3 payments or less (as a percent)	39.00%	46.00%	35.00%
4 - 11 payments (in loans)	13,734	12,446	12,275
4 - 11 payments (as a percent)	33.00%	27.00%	27.00%
12 payments or more (in loans)	11,486	12,432	17,382
12 payments or more (as a percent)	28.00%	27.00%	38.00%
Total primary delinquent inventory (in loans)	41,243	46,556	45,349	50,282
Total primary delinquent inventory (as a percent)	100.00%	100.00%	100.00%
Percent of 12 payments or more delinquent inventory, 36 payments or more delinquent (as a percent)	42.00%	43.00%	45.00%
Pool insurance delinquent inventory (in loans)	1,200	1,309	1,714

Shareholders' Equity (Details)

Shareholders' Equity (Details)	Jul. 23, 2015$ / sharesshares
Class of Warrant or Right [Line Items]
Common stock, beneficial ownership threshold to be considered an Acquiring Person (as a percent)	5.00%
Common shares purchasable per Right (in shares) | shares	0.1
Shareholder rights accompanying each outstanding share of the company's common stock (in number of Rights) | shares	1
Purchase price (in dollars per share) | $ / shares	$ 45
Purchase price, one-tenth share (in dollars per share) | $ / shares	4.50
Redemption price (in dollars per Right) | $ / shares	$ 0.001
Rights
Class of Warrant or Right [Line Items]
Number of rights per outstanding share of common stock (in shares) | 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

Share-Based Compensation (Detai

Share-Based Compensation (Details) - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
RSUs subject to performance conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,239	1,237
Weighted Average Share Fair Value (in dollars per share)	$ 15.80	$ 10.41
RSUs subject only to service conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	412	395
Weighted Average Share Fair Value (in dollars per share)	$ 15.71	$ 10.41
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	12 Months Ended
	Mar. 31, 2018USD ($)jurisdiction	Dec. 31, 2017USD ($)
Statutory capital requirements [Abstract]
Number of jurisdictions with risk-to-capital requirements (in jurisdictions) | jurisdiction	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	10.3 to 1
Risk-to-capital ratio for combined insurance operations	10.3
Percentage of statutory policyholders surplus used to determine maximum allowable dividends (as a percent)	10.00%
Mortgage Guaranty Insurance Corporation
Statutory capital requirements [Abstract]
Maximum risk-to-capital ratio	25
Risk to capital ratio at end of period	9.4 to 1
Risk-to-capital ratio	9.4
Amount of policyholders position above or below required MPP	$ 2,200
Amount of required MPP	1,200
Cash dividends paid	$ 50
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		$ 473