BankFinancial (BFIN) 10-Q 30 Apr 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 27, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2,018
Entity Registrant Name	BankFinancial CORP
Entity Central Index Key	1,303,942
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		17,739,054
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and due from other financial institutions	$ 10,613	$ 13,572
Interest-bearing deposits in other financial institutions	81,963	114,020
Cash and cash equivalents	92,576	127,592
Securities, at fair value		93,383
Loans receivable, net of allowance for loan losses: March 31, 2018, $8,341 and December 31, 2017, $8,366	1,277,553	1,314,651
Other real estate owned, net	1,802	2,351
Stock in Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB), at cost	8,290	8,290
Premises held-for-sale	5,581	5,667
Premises and equipment, net	24,628	24,856
Accrued interest receivable	4,900	4,619
Core deposit intangible	164	286
Bank owned life insurance	22,925	22,859
Deferred taxes	11,363	12,563
Other assets	7,486	8,441
Total assets	1,559,929	1,625,558
Deposits
Noninterest-bearing	232,593	234,354
Interest-bearing	1,045,414	1,105,697
Total deposits	1,278,007	1,340,051
Borrowings	60,983	60,768
Advance payments by borrowers for taxes and insurance	9,558	11,645
Accrued interest payable and other liabilities	13,029	15,460
Total liabilities	1,361,577	1,427,924
Commitments and contingent liabilities
Stockholders’ equity
Preferred Stock, $0.01 par value, 25,000,000 shares authorized, none issued or outstanding	0	0
Common Stock, $0.01 par value, 100,000,000 shares authorized; 17,877,223 shares issued at March 31, 2018 and 17,958,723 issued at December 31, 2017	178	179
Additional paid-in capital	152,489	153,811
Retained earnings	45,397	43,274
Accumulated other comprehensive income	288	370
Total stockholders’ equity	198,352	197,634
Total liabilities and stockholders’ equity	$ 1,559,929	$ 1,625,558

Consolidated Statements of Fin3

Consolidated Statements of Financial Condition (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for loan losses	$ 8,341	$ 8,366
Preferred Stock, par value (usd per share)	$ 0.01	$ 0.01
Preferred Stock, shares authorized	25,000,000	25,000,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Common Stock, par value (usd per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	100,000,000	100,000,000
Common Stock, shares issued	17,877,223	17,958,723

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest and dividend income
Loans, including fees	$ 13,820	$ 12,760
Securities	464	349
Other	464	253
Total interest income	14,748	13,362
Interest expense
Deposits	1,525	1,180
Borrowings	202	96
Borrowings	1,727	1,276
Net interest income	13,021	12,086
Provision for (recovery of) loan losses	(258)	161
Net interest income after provision for (recovery of) loan losses	13,279	11,925
Noninterest income
Deposit service charges and fees	978	950
Loan fee income	70	60
Commercial mortgage brokerage fees	41	0
Residential mortgage banking fees	30	44
Trust and insurance commissions and annuities income	213	249
Earnings on bank owned life insurance	66	63
Other	141	178
Total noninterest income	1,539	1,544
Noninterest expense
Compensation and benefits	5,322	6,352
Office occupancy and equipment	1,731	1,622
Advertising and public relations	143	381
Information technology	641	753
Supplies, telephone, and postage	333	332
Amortization of intangibles	122	129
Nonperforming asset management	202	104
Operations of other real estate owned	161	213
FDIC insurance premiums	119	187
Other	1,185	1,193
Total noninterest expense	9,959	11,266
Income before income taxes	4,859	2,203
Income tax expense	1,300	322
Net income	$ 3,559	$ 1,881
Basic earnings per common share (usd per share)	$ 0.20	$ 0.10
Diluted earnings per common share (usd per share)	$ 0.20	$ 0.10
Weighted average common shares outstanding (shares)	17,930,639	18,642,054
Diluted weighted average common shares outstanding (shares)	17,931,100	18,647,516

Consolidated Statements Compreh

Consolidated Statements Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net income	$ 3,559	$ 1,881
Unrealized holding loss arising during the period	104	20
Tax effect	22	7
Net of tax	(82)	(13)
Comprehensive income	$ 3,477	$ 1,868

Consolidated Statements of Chan

Consolidated Statements of Changes In Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Unearned Employee Stock Ownership Plan Shares	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2016	$ 204,780	$ 192	$ 173,047	$ 39,483	$ (8,318)	$ 376
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,881			1,881
Other comprehensive loss, net of tax	(13)					(13)
Net exercise of stock options (192,215 shares)	(1,218)	2	(1,220)
Prepayment of ESOP Share Acquisition Loan	1,125	(8)	(7,185)		8,318
Repurchase and retirement of common stock (81,500 and 232,045 shares for quarters ended March 31, 2017 and 2016, respectively)	(3,379)	(2)	(3,377)
Cash dividends declared on common stock ($0.08 and $0.06 per share for quarters ended March 31, 2017 and 2016, respectively)	(1,155)			(1,155)
Ending Balance at Mar. 31, 2017	202,021	184	161,265	40,209	0	363
Beginning Balance at Dec. 31, 2017	197,634	179	153,811	43,274	0	370
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,559			3,559
Other comprehensive loss, net of tax	(82)					(82)
Repurchase and retirement of common stock (81,500 and 232,045 shares for quarters ended March 31, 2017 and 2016, respectively)	(1,323)	(1)	(1,322)
Cash dividends declared on common stock ($0.08 and $0.06 per share for quarters ended March 31, 2017 and 2016, respectively)	(1,436)			(1,436)
Ending Balance at Mar. 31, 2018	$ 198,352	$ 178	$ 152,489	$ 45,397	$ 0	$ 288

Consolidated Statements of Cha7

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Stockholders' Equity [Abstract]
Cash dividends declared on common stock (in dollars per share)	$ 0.08	$ 0.06
Repurchase and retirement of common stock (in shares)	81,500	232,045,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flow - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 3,559	$ 1,881
Adjustments to reconcile to net income to net cash from operating activities
Provision for (recovery of) loan losses	(258)	161
Prepayment of ESOP Share Acquisition Loan	0	1,125
Depreciation and amortization	916	958
Amortization of premiums and discounts on securities and loans	3	(65)
Amortization of core deposit intangible	122	129
Amortization of servicing assets	27	31
Net change in net deferred loan origination costs	36	129
Loss on sale of other real estate owned	21	16
Net gain on sale of loans	0	(7)
Loans originated for sale	0	(239)
Proceeds from sale of loans	0	246
Other real estate owned valuation adjustments	25	20
Net change in:
Accrued interest receivable	(281)	(97)
Earnings on bank owned life insurance	(66)	(63)
Other assets	2,037	1,834
Accrued interest payable and other liabilities	(2,431)	(2,701)
Net cash from operating activities	3,710	3,358
Securities
Proceeds from maturities	27,499	13,623
Proceeds from principal repayments	1,030	637
Purchases of securities	(37,923)	(17,302)
Loans receivable
Loan participations sold	0	1,615
Principal payments on loans receivable	226,439	136,090
Purchase of loans	0	(20,406)
Originated for investment	(189,659)	(125,813)
Proceeds of redemption of FHLB stock	0	3,514
Purchase of FHLB and FRB stock	0	11
Proceeds from sale of other real estate owned	713	494
Purchase of premises and equipment, net	(150)	(179)
Net cash from (used in) investing activities	27,949	(7,738)
Cash flows from financing activities
Net change in deposits	(62,044)	(10,108)
Net change in borrowings	215	977
Net change in advance payments by borrowers for taxes and insurance	(2,087)	(1,973)
Payments for Repurchase of Common Stock	(1,323)	(3,379)
Payments of Ordinary Dividends, Common Stock	(1,436)	(1,155)
Payments for Deposits Applied to Debt Retirements	0	1,200
Net cash used in financing activities	(66,675)	(16,838)
Net change in cash and cash equivalents	(35,016)	(21,218)
Beginning cash and cash equivalents	127,592	96,684
Ending cash and cash equivalents	92,576	75,466
Supplemental disclosures of cash flow information:
Interest paid	1,694	1,243
Income taxes paid	43	1
Loans transferred to other real estate owned	$ 562	$ 1,936

Summary of Significant Accounti

Summary of Significant Accounting Policies (Notes)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Basis of Presentation : BankFinancial Corporation, a Maryland corporation headquartered in Burr Ridge, Illinois (the “Company”), is the owner of all of the issued and outstanding capital stock of BankFinancial, NA (the “Bank”). The interim unaudited consolidated financial statements include the accounts and transactions of BankFinancial Corporation, the Bank, and the Bank’s wholly-owned subsidiaries, Financial Assurance Services, Inc. and BFIN Asset Recovery Company, LLC (collectively, “the Company”), and reflect all normal and recurring adjustments that are, in the opinion of management, considered necessary for a fair presentation of the financial condition and results of operations for the periods presented. Such adjustments are the only adjustments reflected in the accompanying financial statements. All significant intercompany accounts and transactions have been eliminated. The results of operations for the three -month period ended March 31, 2018 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2018 or for any other period. Certain information and note disclosures normally included in financial statements prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission. Use of Estimates : To prepare financial statements in conformity with GAAP, management makes estimates and assumptions based on available information. These estimates and assumptions affect the amounts reported in the financial statements and the disclosures provided, and future results could differ. Reclassifications : Certain reclassifications have been made in the prior period’s financial statements to conform them to the current period’s presentation. These unaudited consolidated financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 , as filed with the Securities and Exchange Commission. Recent Accounti

Earnings Per Share (Notes)

Earnings Per Share (Notes)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	ngs per share reflect earnings available to common stockholders for the period divided by the weighted average number of shares of common stock outstanding during the period, exclusive of unearned BankFinancial, NA Employee Stock Ownership Plan (the "ESOP") shares in 2017 and unvested restricted stock shares. Stock options and restricted stock are regarded as potential common stock and are considered in the diluted earnings per share calculations to the extent that they would have a dilutive effect if converted to common stock. Three Months Ended 2018 2017 Net income available to common stockholders $ 3,559 $ 1,881 Average common shares outstanding 17,931,579 19,243,941 Less: Unearned ESOP shares — (600,947 ) Unvested restricted stock shares (940 ) (940 ) Weighted average common shares outstanding 17,930,639 18,642,054 Add - Net effect of dilutive unvested restricted stock 461 5,462 Diluted weighted average common shares outstanding 17,931,100 18,647,516 Basic earnings per common share $ 0.20 $ 0.10 Diluted earnings per common share $ 0.20 $ 0.10

Securities (Notes)

Securities (Notes)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
SECURITIES	The fair value of securities and the related gross unrealized gains and losses recognized in accumulated other comprehensive income are shown below. Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value March 31, 2018 Certificates of deposit $ 86,340 $ — $ — $ 86,340 Mortgage-backed securities - residential 11,146 441 (43 ) 11,544 Collateralized mortgage obligations - residential 4,272 16 (11 ) 4,277 SBA-guaranteed loan participation certificates 9 — — 9 $ 101,767 $ 457 $ (54 ) $ 102,170 December 31, 2017 Certificates of deposit $ 75,916 $ — $ — $ 75,916 Equity mutual fund 500 — (1 ) 499 Mortgage-backed securities - residential 11,969 520 (17 ) 12,472 Collateralized mortgage obligations - residential 4,481 16 (11 ) 4,486 SBA-guaranteed loan participation certificates 10 — — 10 $ 92,876 $ 536 $ (29 ) $ 93,383 The mortgage-backed securities and collateralized mortgage obligations reflected in the preceding table were issued by U.S. government-sponsored entities or agencies, Freddie Mac, Fannie Mae and Ginnie Mae, and are obligations which the government has affirmed its commitment to support. All securities reflected in the preceding table were classified as available-for-sale at March 31, 2018 and December 31, 2017 . The amortized cost and fair values of securities by contractual maturity are shown below. Securities not due at a single maturity date are shown separately. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. March 31, 2018 Amortized Cost Fair Value Due in one year or less $ 86,340 $ 86,340 Mortgage-backed securities - residential 11,146 11,544 Collateralized mortgage obligations - residential 4,272 4,277 SBA-guaranteed loan participation certificates 9 9 $ 101,767 $ 102,170 There were no sales of securities for the periods ended March 31, 2018 and 2017 . Securities with unrealized losses not recognized in income are as follows: Less than 12 Months 12 Months or More Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss March 31, 2018 Mortgage-backed securities - residential $ — $ — $ 1,111 $ (43 ) $ 1,111 $ (43 ) Collateralized mortgage obligations - residential — — 1,983 (11 ) 1,983 (11 ) $ — $ — $ 3,094 $ (54 ) $ 3,094 $ (54 ) December 31, 2017 Equity mutual fund $ 499 $ (1 ) $ — $ — $ 499 $ (1 ) Mortgage-backed securities - residential — — 1,149 (17 ) 1,149 (17 ) Collateralized mortgage obligations - residential — — 2,083 (11 ) 2,083 (11 ) $ 499 $ (1 ) $ 3,232 $ (28 ) $ 3,731 $ (29 ) The Company evaluates marketable investment securities with significant declines in fair value on a quarterly basis to determine whether they should be considered other-than-temporarily impaired under current accounting guidance, which generally provides that if a marketable security is in an unrealized loss position, whether due to general market conditions or industry or issuer-specific factors, the holder of the securities must assess whether the impairment is other-than-temporary. Certain mortgage-backed securities and collateralized mortgage obligations that the Company holds in its investment portfolio were in an unrealized loss position at March 31, 2018 , but the unrealized losses were not considered significant under the Company’s impairment testing methodology. In addition, the Company does not intend to sell these securities, and it is likely that the Company will not be required to sell these securities before their anticipated recovery occurs.

Loans Receivable (Notes)

Loans Receivable (Notes)	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Loans, Notes, Trade and Other Receivables Disclosure [Text Block]	Loans receivable are as follows: March 31, 2018 December 31, 2017 One-to-four family residential real estate $ 92,056 $ 97,814 Multi-family mortgage 578,144 588,383 Nonresidential real estate 163,856 169,971 Construction and land 1,328 1,358 Commercial loans 162,564 152,552 Commercial leases 285,222 310,076 Consumer 1,494 1,597 1,284,664 1,321,751 Net deferred loan origination costs 1,230 1,266 Allowance for loan losses (8,341 ) (8,366 ) Loans, net $ 1,277,553 $ 1,314,651 The following tables present the balance in the allowance for loan losses and the loans receivable by portfolio segment and based on impairment method: Allowance for loan losses Loan Balances Individually evaluated for impairment Collectively evaluated for impairment Total Individually evaluated for impairment Collectively evaluated for impairment Total March 31, 2018 One-to-four family residential real estate $ — $ 765 $ 765 $ 3,576 $ 88,480 $ 92,056 Multi-family mortgage — 3,866 3,866 947 577,197 578,144 Nonresidential real estate — 1,577 1,577 — 163,856 163,856 Construction and land — 32 32 — 1,328 1,328 Commercial loans — 1,441 1,441 — 162,564 162,564 Commercial leases — 650 650 — 285,222 285,222 Consumer — 10 10 — 1,494 1,494 $ — $ 8,341 $ 8,341 $ 4,523 $ 1,280,141 1,284,664 Net deferred loan origination costs 1,230 Allowance for loan losses (8,341 ) Loans, net $ 1,277,553 Allowance for loan losses Loan Balances Individually evaluated for impairment Collectively evaluated for impairment Total Individually evaluated for impairment Collectively evaluated for impairment Total December 31, 2017 One-to-four family residential real estate $ — $ 850 $ 850 $ 4,265 $ 93,549 $ 97,814 Multi-family mortgage — 3,849 3,849 949 587,434 588,383 Nonresidential real estate — 1,605 1,605 — 169,971 169,971 Construction and land — 32 32 — 1,358 1,358 Commercial loans — 1,357 1,357 — 152,552 152,552 Commercial leases — 655 655 — 310,076 310,076 Consumer — 18 18 — 1,597 1,597 $ — $ 8,366 $ 8,366 $ 5,214 $ 1,316,537 1,321,751 Net deferred loan origination costs 1,266 Allowance for loan losses (8,366 ) Loans, net $ 1,314,651 Activity in the allowance for loan losses is as follows: Three Months Ended 2018 2017 Beginning balance $ 8,366 $ 8,127 Loans charged off: One-to-four family residential real estate (97 ) (171 ) Multi-family mortgage — (3 ) Nonresidential real estate — (165 ) (97 ) (339 ) Recoveries: One-to-four family residential real estate 99 6 Multi-family mortgage 8 11 Commercial loans 223 5 330 22 Net recoveries (charge-offs) 233 (317 ) Provision for (recovery of) loan losses (258 ) 161 Ending balance $ 8,341 $ 7,971 The following tables present the recorded investment in nonaccrual loans and loans past due over 90 days still on accrual by class of loans: Loan Balance Recorded Investment Loans Past Due Over 90 Days, Still Accruing March 31, 2018 One-to-four family residential real estate $ 1,675 $ 1,543 $ — One-to-four family residential real estate – non-owner occupied 86 46 — Multi-family mortgage - Illinois 375 369 — $ 2,136 $ 1,958 $ — December 31, 2017 One-to-four family residential real estate $ 3,413 $ 1,918 $ — One-to-four family residential real estate – non-owner occupied 308 109 — Multi-family mortgage - Illinois 376 363 — $ 4,097 $ 2,390 $ — Nonaccrual loans and impaired loans are defined differently. Some loans may be included in both categories, and some loans may only be included in one category. Nonaccrual loans include both smaller balance homogeneous loans that are collectively evaluated for impairment and individually classified impaired loans. The Company’s reserve for uncollected loan interest was $76,000 and $103,000 at March 31, 2018 and December 31, 2017 , respectively. When a loan is on nonaccrual status and the ultimate collectability of the total principal of an impaired loan is in doubt, all payments are applied to principal under the cost recovery method. Alternatively, when a loan is on non-accrual status but there is doubt concerning only the ultimate collectability of interest, contractual interest is credited to interest income only when received, under the cash basis method pursuant to the provisions of FASB ASC 310–10, as applicable. In all cases, the average balances are calculated based on the month–end balances of the financing receivables within the period reported pursuant to the provisions of FASB ASC 310–10, as applicable. The following tables present the aging of the recorded investment of loans at March 31, 2018 by class of loans: 30-59 Days Past Due 60-89 Days Past Due 90 Days or Greater Past Due Total Past Due Loans Not Past Due Total One-to-four family residential real estate loans $ 1,875 $ 58 $ 1,398 $ 3,331 $ 68,216 $ 71,547 One-to-four family residential real estate loans – non-owner occupied 368 10 46 424 19,676 20,100 Multi-family mortgage - Illinois 268 — 271 539 273,950 274,489 Multi-family mortgage - Other — — — — 299,725 299,725 Nonresidential real estate 940 — — 940 161,265 162,205 Construction — — — — 1,096 1,096 Land — — — — 234 234 Commercial loans: Regional commercial banking — — — — 48,160 48,160 Health care — — — — 69,980 69,980 Direct commercial lessor — — — — 44,939 44,939 Commercial leases: Investment rated commercial leases 1,727 152 — 1,879 185,386 187,265 Other commercial leases 572 255 — 827 98,900 99,727 Consumer — 22 — 22 1,481 1,503 $ 5,750 $ 497 $ 1,715 $ 7,962 $ 1,273,008 $ 1,280,970 The following tables present the aging of the recorded investment of loans at December 31, 2017 by class of loans: 30-59 Days Past Due 60-89 Days Past Due 90 Days or Total Past Due Loans Not Past Due Total One-to-four family residential real estate loans $ 86 $ 99 $ 1,801 $ 1,986 $ 74,216 $ 76,202 One-to-four family residential real estate loans – non-owner occupied 10 3 86 99 20,944 21,043 Multi-family mortgage - Illinois 172 — 364 536 287,171 287,707 Multi-family mortgage - Other — — — — 296,440 296,440 Nonresidential real estate 608 — — 608 166,071 166,679 Construction — — — — 1,103 1,103 Land — — — — 259 259 Commercial loans: Regional commercial banking — — — — 40,935 40,935 Health care — — — — 71,738 71,738 Direct commercial lessor — — — — 40,237 40,237 Commercial leases: Investment rated commercial leases 934 — — 934 207,747 208,681 Other commercial leases 288 — — 288 102,873 103,161 Consumer — — — — 1,605 1,605 $ 2,098 $ 102 $ 2,251 $ 4,451 $ 1,311,339 $ 1,315,790 The Company evaluates loan extensions or modifications in accordance with FASB ASC 310–40 with respect to the classification of the loan as a Troubled Debt Restructuring ("TDR"). In general, if the Company grants a loan extension or modification to a borrower for other than an insignificant period of time that includes a below–market interest rate, principal forgiveness, payment forbearance or other concession intended to minimize the economic loss to the Company, the loan extension or loan modification is classified as a TDR. In cases where borrowers are granted new terms that provide for a reduction of either interest or principal then due and payable, management measures any impairment on the restructured loan in the same manner as for impaired loans as noted above. The Company had $17,000 of TDRs at March 31, 2018 and December 31, 2017 . No specific valuation reserves were allocated to those loans at March 31, 2018 and December 31, 2017 . The Company had no outstanding commitments to borrowers whose loans were classified as TDRs at either date. The following table presents loans classified as TDRs: March 31, 2018 December 31, 2017 One-to-four family residential real estate - nonaccrual $ 17 $ 17 During the three months ended March 31, 2018 and 2017 , there were no loans modified and classified as TDRs. A TDR is considered to be in payment default once it is 90 days contractually past due under the modified terms. There were no payment defaults on TDRs during the three months ended March 31, 2018 and 2017 within twelve months following the modification. There were no loan modifications during the three months ended March 31, 2018 . There were certain loan modifications during the three months ended March 31, 2017 that did not meet the definition of a TDR. These loans had a total recorded investment of $133,000 at March 31, 2017 . The modification of these loans involved either a modification of the terms of a loan to borrowers who were not experiencing financial difficulties or a delay in a payment that was considered to be insignificant. In order to determine whether a borrower is experiencing financial difficulty, an evaluation is performed of the probability that the borrower will be in payment default on any of its debt in the foreseeable future without the modification. This evaluation is performed under the Company’s internal underwriting policy. The Company categorizes loans into risk categories based on relevant information about the ability of borrowers to service their debt, including current financial information, historical payment experience, credit documentation, public information, and current economic trends, among other factors. The Company analyzes loans individually by classifying the loans based on credit risk. This analysis includes non-homogeneous loans, such as commercial and commercial real estate loans. This analysis is performed on a monthly basis. The Company uses the following definitions for risk ratings: Special Mention. A Special Mention asset has potential weaknesses that deserve management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the asset or in the institution’s credit position at some future date. Special Mention assets are not adversely classified and do not expose an institution to sufficient risk to warrant adverse classification. Substandard. Loans categorized as Substandard continue to accrue interest, but exhibit a well-defined weakness or weaknesses that may jeopardize the liquidation of the debt. The loans continue to accrue interest because they are well secured and collection of principal and interest is expected within a reasonable time. The risk rating guidance published by the Office of the Comptroller of the Currency clarifies that a loan with a well-defined weakness does not have to present a probability of default for the loan to be rated Substandard, and that an individual loan’s loss potential does not have to be distinct for the loan to be rated Substandard. Nonaccrual. An asset classified Nonaccrual has all the weaknesses inherent in one classified Substandard with the added characteristic that the weaknesses make collection or liquidation in full, on the basis of currently existing facts, conditions, and values, highly questionable and improbable. Loans not meeting the criteria above that are analyzed individually as part of the above described process are considered “Pass” rated loans. As of March 31, 2018 , based on the most recent analysis performed, the risk categories of loans by class of loans are as follows: Pass Special Mention Substandard Nonaccrual Total One-to-four family residential real estate loans $ 70,004 $ — $ 323 $ 1,539 $ 71,866 One-to-four family residential real estate loans – non-owner occupied 20,105 — 39 46 20,190 Multi-family mortgage loans - Illinois 275,552 — 222 370 276,144 Multi-family mortgage loans - Other 302,000 — — — 302,000 Nonresidential real estate loans 163,707 — 149 — 163,856 Construction loans 1,093 — — — 1,093 Land loans 235 — — — 235 Commercial loans: Regional commercial banking 43,467 4,644 — — 48,111 Health care 67,669 — 2,258 — 69,927 Direct commercial lessor 44,526 — — — 44,526 Commercial leases: Investment rated commercial leases 186,052 — — — 186,052 Other commercial leases 99,170 — — — 99,170 Consumer 1,494 — — — 1,494 $ 1,275,074 $ 4,644 $ 2,991 $ 1,955 $ 1,284,664 As of December 31, 2017 , the risk categories of loans by class of loans are as follows: Pass Special Mention Substandard Nonaccrual Total One-to-four family residential real estate loans $ 74,437 $ — $ 255 $ 1,914 $ 76,606 One-to-four family residential real estate loans – non-owner occupied 21,059 — 40 109 21,208 Multi-family mortgage loans - Illinois 290,765 — 225 368 291,358 Multi-family mortgage loans - Other 297,025 — — — 297,025 Nonresidential real estate loans 169,817 — 154 — 169,971 Construction loans 1,099 — — — 1,099 Land loans 259 — — — 259 Commercial loans: Regional commercial banking 36,373 4,528 — — 40,901 Health care 69,480 — 2,248 — 71,728 Direct commercial lessor 39,923 — — — 39,923 Commercial leases: Investment rated commercial leases 207,460 — — — 207,460 Other commercial leases 102,616 — — — 102,616 Consumer 1,597 — — — 1,597 $ 1,311,910 $ 4,528 $ 2,922 $ 2,391 $ 1,321,751

Other Real Estate Owned (Notes)

Other Real Estate Owned (Notes)	3 Months Ended
	Mar. 31, 2018
Other Real Estate [Abstract]
Real Estate Owned [Text Block]	eal estate that is acquired through foreclosure or a deed in lieu of foreclosure is classified as other real estate owned ("OREO") until it is sold. When real estate is acquired through foreclosure or by deed in lieu of foreclosure, it is recorded at its fair value, less the estimated costs of disposal. If the fair value of the property is less than the loan balance, the difference is charged against the allowance for loan losses. March 31, 2018 December 31, 2017 Balance Valuation Allowance Net OREO Balance Balance Valuation Allowance Net OREO Balance One–to–four family residential $ 935 $ — $ 935 $ 836 $ (9 ) $ 827 Nonresidential real estate 1,140 (277 ) 863 1,772 (252 ) 1,520 Land 48 (44 ) 4 48 (44 ) 4 $ 2,123 $ (321 ) $ 1,802 $ 2,656 $ (305 ) $ 2,351 The following represents the roll forward of OREO and the composition of OREO properties: For the Three Months Ended March 31, 2018 2017 Beginning balance $ 2,351 $ 3,895 New foreclosed properties 562 1,936 Valuation adjustments (25 ) (20 ) Sales and payments (1,086 ) (510 ) Ending balance $ 1,802 $ 5,301 Activity in the valuation allowance is as follows: For the Three Months Ended March 31, 2018 2017 Beginning balance $ 305 $ 449 Additions charged to expense 25 20 Reductions from sales of OREO (9 ) (59 ) Ending balance $ 321 $ 410 At March 31, 2018 , the balance of OREO included no foreclosed residential real estate properties recorded as a result of obtaining physical possession of the property without title. At December 31, 2017 the balance of OREO included $352,000 foreclosed residential real estate properties recorded as a result of obtaining physical possession of the property without title. At March 31, 2018 and December 31, 2017 , the recorded investment of consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings were in process was $1.3 million and $1.5 million , respectively.

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Mar. 31, 2018
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	Stock Ownership Plan . On March 29, 2017, the ESOP was terminated and the ESOP repaid all amounts owing under the ESOP’s Term Loan Agreement with the Company (the “Share Acquisition Loan”). The ESOP repaid the Share Acquisition Loan by transferring 753,490 unallocated shares of the Company’s common stock to the Company in exchange for the full satisfaction of the Share Acquisition Loan, using the valuation method provided for in the ESOP. A total of 78,362 unallocated shares remained in the ESOP after the Share Acquisition Loan was repaid, and these shares were released and will be allocated to the accounts of eligible ESOP participants who were actively employed by the Bank as of March 29, 2017, based on their account balances, subject to the receipt of a favorable IRS determination letter. These transactions resulted in the recording of one-time, non-cash, non-tax deductible equity compensation expense of $1.1 million in the first quarter of 2017. The Share Acquisition Loan had no outstanding principal balance at March 31, 2018 and an outstanding principal balance of $10.8 million at December 31, 2017 . The Company made the Share Acquisition Loan to the ESOP in the original principal amount of $19.6 million in connection with the Company’s mutual to stock conversion in June of 2005. The proceeds of the Share Acquisition Loan were used by the ESOP to purchase 1,957,300 shares of the Company’s common stock issued in the subscription offering at a price of $10.00 per share. The Share Acquisition Loan was secured by a pledge of the acquired shares and the ESOP made annual loan payments with funds it received from the Bank’s discretionary contributions to the ESOP in subsequent years and dividends it received on unallocated shares. As loan payments were made, the Company recorded compensation expense based on the allocation of shares released. ESOP benefit expense was recorded based upon the fair value of the awarded shares, net of dividends and interest received on unallocated ESOP shares. ESOP benefit expense totaled $1.3 million for the year ended December 31, 2017 . Shares held by the ESOP were as follows: March 31, 2018 December 31, 2017 Allocated to participants 1,203,810 1,125,448 Distributed to participants (317,914 ) (313,223 ) Unearned — 831,852 Total ESOP shares 885,896 1,644,077 Fair value of unearned shares $ — $ 12,328

Equity Incentive Plans (Notes)

Equity Incentive Plans (Notes)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Incentive Plans	EQUITY INCENTIVE PLAN On June 27, 2006, the Company’s stockholders approved the BankFinancial Corporation 2006 Equity Incentive Plan, which authorized the Human Resources Committee of the Board of Directors of the Company to grant a variety of cash- and equity-based incentive awards, including stock options, stock appreciation rights, restricted stock, performance shares and other incentive awards, to employees and directors aggregating up to 3,425,275 shares of the Company’s common stock. The Plan provides that no awards may be granted under the Plan after the ten -year anniversary of the Effective Date. Consequently, no further awards will be granted under this Plan. As of December 31, 2017 , there were 1,752,156 stock options outstanding. The Company recognized $979,000 of equity-based compensation expense relating to the granting of stock options for the year ended December 31, 2017 . There was no equity-based compensation expense for the three months ended March 31, 2018 . A summary of the activity in the stock option plan for 2018 and 2016 follows: Stock Options Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (1) Stock options outstanding at December 31, 2015 1,752,156 $ 12.30 1.48 $ 778 Stock options granted — — Stock options exercised — — Stock options outstanding at December 31, 2016 1,752,156 $ 12.30 0.48 $ 4,422 Stock options granted — — Stock options exercised (1,752,156 ) 12.30 Stock options outstanding at September 30, 2017 — $ — 0 $ — (1) Stock option aggregate intrinsic value represents the number of shares subject to options multiplied by the difference (if positive) in the closing market price of the common stock underlying the options on the date shown and the weighted average exercise price. During the nine months ended March 31, 2018 , 1,752,156 stock options were exercised. All stock options were exercised on a net settlement basis, using a portion of the shares obtained upon exercise to pay the exercise price of the stock option. The net settlements resulted in the issuance of 280,554 shares of the Company's common stock. Certain employees also chose to use a portion of the net shares received upon the exercise to pay required tax withholdings. This reduced the net shares issued by 82,528 shares to 198,026 shares.

Fair Value (Notes)

Fair Value (Notes)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value	FAIR VALUE Fair value is the exchange price that would be received for an asset or paid to transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There are three levels of inputs that may be used to measure fair values: • Level 1 – Quoted prices (unadjusted) for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date. • Level 2 – Significant other observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data. • Level 3 – Significant unobservable inputs that reflect a company’s own assumptions about the assumptions that market participants would use in pricing an asset or liability. The Company used the following methods and significant assumptions to estimate the fair value of each type of financial instrument: Securities : The fair values of marketable equity securities are generally determined by quoted prices, in active markets, for each specific security (Level 1). If Level 1 measurement inputs are not available for a marketable equity security, we determine its fair value based on the quoted price of a similar security traded in an active market (Level 2). The fair values of debt securities are generally determined by matrix pricing, which is a mathematical technique widely used in the industry to value debt securities without relying exclusively on quoted prices for the specific securities, but rather by relying on the securities’ relationship to other benchmark quoted securities (Level 2). Impaired Loans: The fair value of impaired loans with specific allocations of the allowance for loan losses is generally based on recent real estate appraisals. These appraisals may utilize a single valuation approach or a combination of approaches including comparable sales and the income approach. Adjustments are routinely made in the appraisal process by the independent appraisers to adjust for differences between the comparable sales and income data available for similar loans and collateral underlying such loans. Non-real estate collateral may be valued using an appraisal, net book value per the borrower’s financial statements, or aging reports, adjusted or discounted based on management’s historical knowledge, changes in market conditions from the time of the valuation, and management’s expertise and knowledge of the client and client’s business, resulting in a Level 3 fair value classification. Impaired loans are evaluated on a quarterly basis for additional impairment and adjusted in accordance with the allowance policy. Other Real Estate Owned: Assets acquired through or instead of loan foreclosure are initially recorded at fair value less costs to sell when acquired, establishing a new cost basis. These assets are subsequently accounted for at lower of cost or fair value less estimated costs to sell. Fair value is commonly based on recent real estate appraisals which are updated no less frequently than annually. These appraisals may utilize a single valuation approach or a combination of approaches including comparable sales and the income approach with data from comparable properties. Adjustments are routinely made in the appraisal process by the independent appraisers to adjust for differences between the comparable sales and income data available. Real estate owned properties are evaluated on a quarterly basis for additional impairment and adjusted accordingly. The following table sets forth the Company’s financial assets that were accounted for at fair value and are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value March 31, 2018 Securities: Certificates of deposit $ — $ 86,340 $ — $ 86,340 Equity mutual fund 491 — — 491 Mortgage-backed securities – residential — 11,544 — 11,544 Collateralized mortgage obligations – residential — 4,277 — 4,277 SBA-guaranteed loan participation certificates — 9 — 9 $ 491 $ 102,170 $ — $ 102,661 December 31, 2017 Securities: Certificates of deposit $ — $ 75,916 $ — $ 75,916 Equity mutual fund 499 — — 499 Mortgage-backed securities - residential — 12,472 — 12,472 Collateralized mortgage obligations – residential — 4,486 — 4,486 SBA-guaranteed loan participation certificates — 10 — 10 $ 499 $ 92,884 $ — $ 93,383 The following table sets forth the Company’s assets that were measured at fair value on a non-recurring basis: Fair Value Measurement Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value March 31, 2018 Other real estate owned - nonresidential real estate $ — $ — $ 409 $ 409 December 31, 2017 Other real estate owned: One-to-four family residential real estate $ — $ — $ 102 $ 102 Nonresidential real estate — — 814 814 $ — $ — $ 916 $ 916 At March 31, 2018 and December 31, 2017 there were no impaired loans that were measured for impairment using the fair value of the collateral for collateral–dependent loans and which had specific valuation allowances. OREO, which is carried at the lower of cost or fair value less costs to sell, had a carrying value of $494,000 less a valuation allowance of $85,000 , or $409,000 , at March 31, 2018 , compared to a carrying value of $1.2 million less a valuation allowance of $261,000 , or $916,000 , at December 31, 2017 . There were $25,000 and $20,000 of valuation adjustments of OREO recorded for the three months ended March 31, 2018 and 2017 , respectively. The following table presents quantitative information, based on certain empirical data with respect to Level 3 fair value measurements for financial instruments measured at fair value on a non-recurring basis: Fair Value Valuation Significant Unobservable Range March 31, 2018 Other real estate owned - nonresidential real estate loans $ 409 Sales comparison Comparison between sales and income approaches 12.70% to 26.77% December 31, 2017 Other real estate owned One-to-four family residential real estate $ 102 Sales comparison Discount applied to valuation 5.6% Nonresidential real estate 814 Sales comparison Comparison between sales and income approaches -3.66% to 15.22% (11.0%) $ 916 The carrying amount and estimated fair value of financial instruments are as follows: Fair Value Measurements at March 31, 2018 Using: Carrying Amount Level 1 Level 2 Level 3 Total Financial assets Cash and cash equivalents $ 92,576 $ 10,613 $ 81,963 $ — $ 92,576 Securities 102,661 491 102,170 — 102,661 Loans receivable, net of allowance for loan losses 1,277,553 — — 1,276,635 1,276,635 FHLB and FRB stock 8,290 — — — N/A Accrued interest receivable 4,900 — 4,900 — 4,900 Financial liabilities Noninterest-bearing demand deposits $ 232,593 $ — $ 232,593 $ — $ 232,593 NOW and money market accounts 573,886 — 573,886 — 573,886 Savings deposits 160,093 — 160,093 — 160,093 Certificates of deposit 311,435 — 308,904 — 308,904 Borrowings 60,983 — 60,832 — 60,832 Accrued interest payable 180 — 180 — 180 Fair Value Measurements at December 31, 2017 Using: Carrying Amount Level 1 Level 2 Level 3 Total Financial assets Cash and cash equivalents $ 127,592 $ 13,572 $ 114,020 $ — $ 127,592 Securities 93,383 499 92,884 — 93,383 Loans receivable, net of allowance for loan losses 1,314,651 — 1,323,139 — 1,323,139 FHLB and FRB stock 8,290 — — — N/A Accrued interest receivable 4,619 — 4,619 — 4,619 Financial liabilities Noninterest-bearing demand deposits $ 234,354 $ — $ 234,354 $ — $ 234,354 NOW and money market accounts 589,238 — 589,238 — 589,238 Savings deposits 160,501 — 160,501 — 160,501 Certificates of deposit 355,958 — 353,969 — 353,969 Borrowings 60,768 — 60,627 — 60,627 Accrued interest payable 147 — 147 — 147 For purposes of the above, the following assumptions were used: Cash and Cash Equivalents : The estimated fair values for cash and cash equivalents are based on their carrying value due to the short-term nature of these assets. Loans : At March 31, 2018, the exit price observations are obtained from an independent third-party using its proprietary valuation model and methodology and may not reflect actual or prospective market valuations. The valuation is based on the probability of default, loss given default, recovery delay, prepayment, and discount rate assumptions. The new methodology is a result of the adoption of ASU 2016-01. At December 31, 2017, the estimated fair value for loans has been determined by calculating the present value of future cash flows based on the current rate the Company would charge for similar loans with similar maturities, applied for an estimated time period until the loan is assumed to be repriced or repaid. The methods utilized to estimate fair value of loans do not necessarily represent an exit price. FHLB and FRB Stock : It is not practicable to determine the fair value of FHLB and FRB stock due to the restrictions placed on their transferability. Deposit Liabilities : The estimated fair value for certificates of deposit has been determined by calculating the present value of future cash flows based on estimates of rates the Company would pay on such deposits, applied for the time period until maturity. The estimated fair values of noninterest-bearing demand, NOW, money market, and savings deposits are assumed to approximate their carrying values as management establishes rates on these deposits at a level that approximates the local market area. Additionally, these deposits can be withdrawn on demand. Borrowings : The estimated fair values of advances from the FHLB and notes payable are based on current market rates for similar financing. The estimated fair value of securities sold under agreements to repurchase is assumed to equal its carrying value due to the short-term nature of the liability. Accrued Interest : The estimated fair values of accrued interest receivable and payable are assumed to equal their carrying value. Off - Balance-Sheet Instruments : Off-balance-sheet items consist principally of unfunded loan commitments, standby letters of credit, and unused lines of credit. The estimated fair values of unfunded loan commitments, standby letters of credit, and unused lines of credit are not material. While the above estimates are based on management’s judgment of the most appropriate factors, as of the balance sheet date, there is no assurance that the estimated fair values would have been realized if the assets were disposed of or the liabilities settled at that date, since market values may differ depending on the various circumstances. The estimated fair values would also not apply to subsequent dates. In addition, other assets and liabilities that are not financial instruments, such as premises and equipment, are not included in the above disclosures.

Revenue From Contracts With Cus

Revenue From Contracts With Customers	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Revenue From Contracts With Customers	REVENUE FROM CONTRACTS WITH CUSTOMERS All of the Company's revenue from contracts with customers in the scope of ASC 606 is recognized within noninterest income. The following table presents the Company's sources of noninterest income for the three months ended March 31, 2018 and 2017 . Items outside of the scope of the ASC 606 are noted as such. Three Months Ended 2018 2017 Deposit service charges and fees $ 978 $ 950 Loan fee income (1) 70 60 Commercial mortgage brokerage fees (1) 41 — Residential mortgage banking fees (1) 30 44 Trust and insurance commissions and annuities income 213 249 Earnings on bank owned life insurance (1) 66 63 Other (1) 141 178 Total noninterest income $ 1,539 $ 1,544 (1) Not within the scope of ASC 606 A description of the Company's revenue streams accounted for under ASC 606 follows: Deposit service charges and fees: The Company earns fees from its deposit customers for transaction-based, account maintenance, and overdraft services. Transaction-based fees, which include services such as ATM use fees, stop payment charges, statement rendering, and ACH fees, are recognized at the time the transaction is executed as that is the point in time the Company fulfills the customer's request. Account maintenance fees, which relate primarily to monthly maintenance, are earned over the course of a month, representing the period over which the Company satisfies the performance obligation. Overdraft fees are recognized at the point in time that the overdraft occurs. Service charges on deposits are withdrawn from the customer's account balance. Interchange Income: The Company earns interchange fees from debit cardholder transactions conducted through the Visa payment network. Interchange fees from cardholder transactions represent a percentage of the underlying transaction value and are recognized daily, concurrently with the transaction processing services provided to the cardholder. Interchange income for the three months ended March 31, 2018 and 2017 were $361,000 and $350,000 , respectively. These are included in deposit service charges and fees. Trust and insurance commissions and annuities income: The Company earns trust, insurance commissions and annuities income from its contracts with trust customers to manage assets for investment, and/or to transact on their accounts. These fees are primarily earned over time as the Company provides the contracted monthly or quarterly services and are generally assessed based on a tiered scale of the market value of assets under management (AUM) at month-end. Fees that are transaction based, including trade execution services, are recognized at the point in time that the transaction is executed, i.e., the trade date. Other related services provided include fees the Company earns, which are based on a fixed fee schedule, are recognized when the services are rendered. Gains/Losses on Sales of OREO: The Company records a gain or loss from the sale of OREO when control of the property transfers to the buyer, which generally occurs at the time of an executed deed. When the Company finances the sale of OREO to the buyer, the Company assesses whether the buyer is committed to perform their obligations under the contract and whether collectability of the transaction price is probable. Once these criteria are met, the OREO asset is derecognized and the gain or loss on sale is recorded upon the transfer of control of the property to the buyer. In determining the gain or loss on the sale, the Company adjusts the transaction price and related gain (loss) on sale if a significant financing component is present. OREO sales for the three months ended March 31, 2018 and March 31, 2017 were not financed by the Bank.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS In April 2018, the Bank recorded income from a death benefit on BOLI of $1.4 million related to the death of a former Bank executive. On April 23, 2018, the Bank sold its office building located at 15W060 North Frontage Road, Burr Ridge, Illinois, for a purchase price of $6 million . A net gain in the approximate amount $100,000 will be recorded in the second quarter of 2018 in connection with the sale. Concurrently with the sale, the Bank entered into a six-month lease of the office building with the purchaser, and intends to lease space in a different building following the expiration of the lease with the purchaser. The Company shares space with the Bank in the office building pursuant to an expense allocation agreement.

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Basis of Presentation : BankFinancial Corporation, a Maryland corporation headquartered in Burr Ridge, Illinois (the “Company”), is the owner of all of the issued and outstanding capital stock of BankFinancial, NA (the “Bank”). The interim unaudited consolidated financial statements include the accounts and transactions of BankFinancial Corporation, the Bank, and the Bank’s wholly-owned subsidiaries, Financial Assurance Services, Inc. and BFIN Asset Recovery Company, LLC (collectively, “the Company”), and reflect all normal and recurring adjustments that are, in the opinion of management, considered necessary for a fair presentation of the financial condition and results of operations for the periods presented. Such adjustments are the only adjustments reflected in the accompanying financial statements. All significant intercompany accounts and transactions have been eliminated. The results of operations for the three -month period ended March 31, 2018 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2018 or for any other period. Certain information and note disclosures normally included in financial statements prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission. Use of Estimates : To prepare financial statements in conformity with GAAP, management makes estimates and assumptions based on available information. These estimates and assumptions affect the amounts reported in the financial statements and the disclosures provided, and future results could differ. Reclassifications : Certain reclassifications have been made in the prior period’s financial statements to conform them to the current period’s presentation. These unaudited consolidated financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 , as filed with the Securities and Exchange Commission. Recent Accounti
Basis of Presentation	Basis of Presentation : BankFinancial Corporation, a Maryland corporation headquartered in Burr Ridge, Illinois (the “Company”), is the owner of all of the issued and outstanding capital stock of BankFinancial, NA (the “Bank”).
Principles of Consolidation	The interim unaudited consolidated financial statements include the accounts and transactions of BankFinancial Corporation, the Bank, and the Bank’s wholly-owned subsidiaries, Financial Assurance Services, Inc. and BFIN Asset Recovery Company, LLC (collectively, “the Company”), and reflect all normal and recurring adjustments that are, in the opinion of management, considered necessary for a fair presentation of the financial condition and results of operations for the periods presented. Such adjustments are the only adjustments reflected in the accompanying financial statements. All significant intercompany accounts and transactions have been eliminated. The results of operations for the three -month period ended March 31, 2018 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2018 or for any other period. Certain information and note disclosures normally included in financial statements prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission. Use of Estimate
Use of Estimates	Use of Estimates : To prepare financial statements in conformity with GAAP, management makes estimates and assumptions based on available information. These estimates and assumptions affect the amounts reported in the financial statements and the disclosures provided, and future results could differ.
Uncollected Interest Policy	The Company’s reserve for uncollected loan interest was $76,000 and $103,000 at March 31, 2018 and December 31, 2017 , respectively. When a loan is on nonaccrual status and the ultimate collectability of the total principal of an impaired loan is in doubt, all payments are applied to principal under the cost recovery method. Alternatively, when a loan is on non-accrual status but there is doubt concerning only the ultimate collectability of interest, contractual interest is credited to interest income only when received, under the cash basis method pursuant to the provisions of FASB ASC 310–10, as applicable. In all cases, the average balances are calculated based on the month–end balances of the financing receivables within the period reported pursuant to the provisions of FASB ASC 310–10, as applicable.
Reclassifications	Reclassifications : Certain reclassifications have been made in the prior period’s financial statements to conform them to the current period’s presentation. These unaudited consolidated financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 , as filed with the Securities and Exchange Commission.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued an update (ASU No. 2014-09, Revenue from Contracts with Customers) creating FASB Topic 606, Revenue from Contracts with Customers. The guidance in this update affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (for example, insurance contracts or lease contracts). The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance provides steps to follow to achieve the core principle. An entity should disclose sufficient information to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Qualitative and quantitative information is required about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. The amendments in this update became effective for annual periods and interim periods within those annual periods beginning after December 15, 2017. We have evaluated the impact of adopting the update and have concluded that it does not have a significant impact to our consolidated financial statements. The Company’s revenue streams that are in-scope from the update include: financed OREO sales; deposit fees, including ATM fees, overdraft fees, maintenance fees and dormancy fees; debit card fees, and trust fees. For the in-scope revenue streams, our current revenue recognition is not different than our prior revenue recognition under the update. The Company has infrequently financed an OREO sale. Our customer contracts generally do not have performance obligations and fees are assessed and collected as the transaction occurs. The Company’s fee income is not material for any individual income streams. The adoption of ASC 606 did not result in a change to the accounting for any of the in-scope revenue stream; as such, no cumulative effect adjustment was recorded. Refer to Note 8 - Revenue for Contracts with Customers for further discussion on the Company's accounting policies for revenue sources within the scope of ASC 606. In January 2016, the FASB issued an update (ASU No. 2016-01, Financial Instruments - Recognition and Measurement of Financial Assets and Liabilities). The new guidance is intended to improve the recognition and measurement of financial instruments by requiring: equity investments (other than equity method or consolidation) to be measured at fair value with changes in fair value recognized in net income; public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; separate presentation of financial assets and financial liabilities by measurement category and form of financial assets ( i.e., securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; eliminating the requirement to disclose the fair value of financial instruments measured at amortized cost for organizations that are not public business entities; eliminating the requirement for non-public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is to be required to be disclosed for financial instruments measured at amortized cost on the balance sheet; and requiring a reporting organization to present separately in other comprehensive income the portion of the total change in fair value of a liability resulting from the change in the instrument-specific credit risk (also referred to as “own credit”) when the organization has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. The new guidance became effective for public business entities for fiscal years beginning after December 15, 2017. The new pronouncement does not have a significant impact on our Statement of Operations, as we only have one equity security that was valued at $491,000 and $499,000 at March 31, 2018 and December 31, 2017 , respectively. The equity security is reported separately on the Statement of Condition as a result the adoption of this pronouncement. In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842)” (“ASU 2016-02”). The standard requires a lessee to recognize assets and liabilities on the balance sheet for leases with lease terms greater than 12 months. ASU 2016-02 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. We are currently evaluating the impact that the standard will have on our consolidated financial statements. Our preliminary finding is that the new pronouncement will not have a significant impact on our consolidated financial statements as the projected minimum lease payments under existing leases subject to the new pronouncement are less than one percent of our current total assets. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). These amendments require the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. Financial institutions and other organizations will now use forward-looking information to better inform their credit loss estimates. Many of the loss estimation techniques applied today will still be permitted, although the inputs to those techniques will change to reflect the full amount of expected credit losses. In addition, the ASU amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 is effective for SEC filers for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019 ( i.e. , January 1, 2020, for calendar year entities). Early application will be permitted for all organizations for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We are currently evaluating the impact that the standard will have on our consolidated financial statements. Our initial review indicates that we have maintained sufficient historical loan data to support the requirements of this pronouncement. In addition, we have begun tracking the average life of the various segments of our loan portfolio. We are currently evaluating various loss methodologies to determine their correlation to our various loan categories' historical performance. In March of 2017, the FASB issued ASU No. 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities” (“ASU 2017-08”). This guidance shortens the amortization period for premiums on certain callable debt securities to the earliest call date (with an explicit, noncontingent call feature that is callable at a fixed price and on a preset dates), rather than contractual maturity date as currently required under GAAP. The ASU does not impact instruments without preset call dates such as mortgage-backed securities. For instruments with contingent call features, once the contingency is resolved and the security is callable at a fixed price and preset date, the security is within the scope of the ASU. ASU 2017-08 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, and early adoption is permitted. Effective January 2017, we early adopted the pronouncement. Adoption of the new pronouncement was immaterial to the consolidated financial statements.

Summary of Significant Accoun20

Summary of Significant Accounting Policies New Accounting Pronouncements (Policies)	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued an update (ASU No. 2014-09, Revenue from Contracts with Customers) creating FASB Topic 606, Revenue from Contracts with Customers. The guidance in this update affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (for example, insurance contracts or lease contracts). The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance provides steps to follow to achieve the core principle. An entity should disclose sufficient information to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Qualitative and quantitative information is required about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. The amendments in this update became effective for annual periods and interim periods within those annual periods beginning after December 15, 2017. We have evaluated the impact of adopting the update and have concluded that it does not have a significant impact to our consolidated financial statements. The Company’s revenue streams that are in-scope from the update include: financed OREO sales; deposit fees, including ATM fees, overdraft fees, maintenance fees and dormancy fees; debit card fees, and trust fees. For the in-scope revenue streams, our current revenue recognition is not different than our prior revenue recognition under the update. The Company has infrequently financed an OREO sale. Our customer contracts generally do not have performance obligations and fees are assessed and collected as the transaction occurs. The Company’s fee income is not material for any individual income streams. The adoption of ASC 606 did not result in a change to the accounting for any of the in-scope revenue stream; as such, no cumulative effect adjustment was recorded. Refer to Note 8 - Revenue for Contracts with Customers for further discussion on the Company's accounting policies for revenue sources within the scope of ASC 606. In January 2016, the FASB issued an update (ASU No. 2016-01, Financial Instruments - Recognition and Measurement of Financial Assets and Liabilities). The new guidance is intended to improve the recognition and measurement of financial instruments by requiring: equity investments (other than equity method or consolidation) to be measured at fair value with changes in fair value recognized in net income; public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; separate presentation of financial assets and financial liabilities by measurement category and form of financial assets ( i.e., securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; eliminating the requirement to disclose the fair value of financial instruments measured at amortized cost for organizations that are not public business entities; eliminating the requirement for non-public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is to be required to be disclosed for financial instruments measured at amortized cost on the balance sheet; and requiring a reporting organization to present separately in other comprehensive income the portion of the total change in fair value of a liability resulting from the change in the instrument-specific credit risk (also referred to as “own credit”) when the organization has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. The new guidance became effective for public business entities for fiscal years beginning after December 15, 2017. The new pronouncement does not have a significant impact on our Statement of Operations, as we only have one equity security that was valued at $491,000 and $499,000 at March 31, 2018 and December 31, 2017 , respectively. The equity security is reported separately on the Statement of Condition as a result the adoption of this pronouncement. In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842)” (“ASU 2016-02”). The standard requires a lessee to recognize assets and liabilities on the balance sheet for leases with lease terms greater than 12 months. ASU 2016-02 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. We are currently evaluating the impact that the standard will have on our consolidated financial statements. Our preliminary finding is that the new pronouncement will not have a significant impact on our consolidated financial statements as the projected minimum lease payments under existing leases subject to the new pronouncement are less than one percent of our current total assets. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). These amendments require the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. Financial institutions and other organizations will now use forward-looking information to better inform their credit loss estimates. Many of the loss estimation techniques applied today will still be permitted, although the inputs to those techniques will change to reflect the full amount of expected credit losses. In addition, the ASU amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 is effective for SEC filers for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019 ( i.e. , January 1, 2020, for calendar year entities). Early application will be permitted for all organizations for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We are currently evaluating the impact that the standard will have on our consolidated financial statements. Our initial review indicates that we have maintained sufficient historical loan data to support the requirements of this pronouncement. In addition, we have begun tracking the average life of the various segments of our loan portfolio. We are currently evaluating various loss methodologies to determine their correlation to our various loan categories' historical performance. In March of 2017, the FASB issued ASU No. 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities” (“ASU 2017-08”). This guidance shortens the amortization period for premiums on certain callable debt securities to the earliest call date (with an explicit, noncontingent call feature that is callable at a fixed price and on a preset dates), rather than contractual maturity date as currently required under GAAP. The ASU does not impact instruments without preset call dates such as mortgage-backed securities. For instruments with contingent call features, once the contingency is resolved and the security is callable at a fixed price and preset date, the security is within the scope of the ASU. ASU 2017-08 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, and early adoption is permitted. Effective January 2017, we early adopted the pronouncement. Adoption of the new pronouncement was immaterial to the consolidated financial statements.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	ngs per share reflect earnings available to common stockholders for the period divided by the weighted average number of shares of common stock outstanding during the period, exclusive of unearned BankFinancial, NA Employee Stock Ownership Plan (the "ESOP") shares in 2017 and unvested restricted stock shares. Stock options and restricted stock are regarded as potential common stock and are considered in the diluted earnings per share calculations to the extent that they would have a dilutive effect if converted to common stock. Three Months Ended 2018 2017 Net income available to common stockholders $ 3,559 $ 1,881 Average common shares outstanding 17,931,579 19,243,941 Less: Unearned ESOP shares — (600,947 ) Unvested restricted stock shares (940 ) (940 ) Weighted average common shares outstanding 17,930,639 18,642,054 Add - Net effect of dilutive unvested restricted stock 461 5,462 Diluted weighted average common shares outstanding 17,931,100 18,647,516 Basic earnings per common share $ 0.20 $ 0.10 Diluted earnings per common share $ 0.20 $ 0.10

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	The fair value of securities and the related gross unrealized gains and losses recognized in accumulated other comprehensive income are shown below. Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value March 31, 2018 Certificates of deposit $ 86,340 $ — $ — $ 86,340 Mortgage-backed securities - residential 11,146 441 (43 ) 11,544 Collateralized mortgage obligations - residential 4,272 16 (11 ) 4,277 SBA-guaranteed loan participation certificates 9 — — 9 $ 101,767 $ 457 $ (54 ) $ 102,170 December 31, 2017 Certificates of deposit $ 75,916 $ — $ — $ 75,916 Equity mutual fund 500 — (1 ) 499 Mortgage-backed securities - residential 11,969 520 (17 ) 12,472 Collateralized mortgage obligations - residential 4,481 16 (11 ) 4,486 SBA-guaranteed loan participation certificates 10 — — 10 $ 92,876 $ 536 $ (29 ) $ 93,383 The mortgage-backed securities and collateralized mortgage obligations reflected in the preceding table were issued by U.S. government-sponsored entities or agencies, Freddie Mac, Fannie Mae and Ginnie Mae, and are obligations which the government has affirmed its commitment to support. All securities reflected in the preceding table were classified as available-for-sale at March 31, 2018 and December 31, 2017 . The amortized cost and fair values of securities by contractual maturity are shown below. Securities not due at a single maturity date are shown separately. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. March 31, 2018 Amortized Cost Fair Value Due in one year or less $ 86,340 $ 86,340 Mortgage-backed securities - residential 11,146 11,544 Collateralized mortgage obligations - residential 4,272 4,277 SBA-guaranteed loan participation certificates 9 9 $ 101,767 $ 102,170 There were no sales of securities for the periods ended March 31, 2018 and 2017 . Securities with unrealized losses not recognized in income are as follows: Less than 12 Months 12 Months or More Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss March 31, 2018 Mortgage-backed securities - residential $ — $ — $ 1,111 $ (43 ) $ 1,111 $ (43 ) Collateralized mortgage obligations - residential — — 1,983 (11 ) 1,983 (11 ) $ — $ — $ 3,094 $ (54 ) $ 3,094 $ (54 ) December 31, 2017 Equity mutual fund $ 499 $ (1 ) $ — $ — $ 499 $ (1 ) Mortgage-backed securities - residential — — 1,149 (17 ) 1,149 (17 ) Collateralized mortgage obligations - residential — — 2,083 (11 ) 2,083 (11 ) $ 499 $ (1 ) $ 3,232 $ (28 ) $ 3,731 $ (29 ) The Company evaluates marketable investment securities with significant declines in fair value on a quarterly basis to determine whether they should be considered other-than-temporarily impaired under current accounting guidance, which generally provides that if a marketable security is in an unrealized loss position, whether due to general market conditions or industry or issuer-specific factors, the holder of the securities must assess whether the impairment is other-than-temporary. Certain mortgage-backed securities and collateralized mortgage obligations that the Company holds in its investment portfolio were in an unrealized loss position at March 31, 2018 , but the unrealized losses were not considered significant under the Company’s impairment testing methodology. In addition, the Company does not intend to sell these securities, and it is likely that the Company will not be required to sell these securities before their anticipated recovery occurs.
Unrealized gains and losses recognized in accumulated other comprehensive income (loss)	The fair value of securities and the related gross unrealized gains and losses recognized in accumulated other comprehensive income are shown below. Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value March 31, 2018 Certificates of deposit $ 86,340 $ — $ — $ 86,340 Mortgage-backed securities - residential 11,146 441 (43 ) 11,544 Collateralized mortgage obligations - residential 4,272 16 (11 ) 4,277 SBA-guaranteed loan participation certificates 9 — — 9 $ 101,767 $ 457 $ (54 ) $ 102,170 December 31, 2017 Certificates of deposit $ 75,916 $ — $ — $ 75,916 Equity mutual fund 500 — (1 ) 499 Mortgage-backed securities - residential 11,969 520 (17 ) 12,472 Collateralized mortgage obligations - residential 4,481 16 (11 ) 4,486 SBA-guaranteed loan participation certificates 10 — — 10 $ 92,876 $ 536 $ (29 ) $ 93,383
Amortized cost and fair values of securities	The amortized cost and fair values of securities by contractual maturity are shown below. Securities not due at a single maturity date are shown separately. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. March 31, 2018 Amortized Cost Fair Value Due in one year or less $ 86,340 $ 86,340 Mortgage-backed securities - residential 11,146 11,544 Collateralized mortgage obligations - residential 4,272 4,277 SBA-guaranteed loan participation certificates 9 9 $ 101,767 $ 102,170
Securities with unrealized losses	Securities with unrealized losses not recognized in income are as follows: Less than 12 Months 12 Months or More Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss March 31, 2018 Mortgage-backed securities - residential $ — $ — $ 1,111 $ (43 ) $ 1,111 $ (43 ) Collateralized mortgage obligations - residential — — 1,983 (11 ) 1,983 (11 ) $ — $ — $ 3,094 $ (54 ) $ 3,094 $ (54 ) December 31, 2017 Equity mutual fund $ 499 $ (1 ) $ — $ — $ 499 $ (1 ) Mortgage-backed securities - residential — — 1,149 (17 ) 1,149 (17 ) Collateralized mortgage obligations - residential — — 2,083 (11 ) 2,083 (11 ) $ 499 $ (1 ) $ 3,232 $ (28 ) $ 3,731 $ (29 )

Loans Receivable (Tables)

Loans Receivable (Tables)	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Loans By Class Modified As Troubled Debt Restructurings With Payment Default [Table Text Block]	TDRs during the three months ended March 31, 2018 and 2017 within twelve months following the modification.
Loans, Notes, Trade and Other Receivables Disclosure [Text Block]	Loans receivable are as follows: March 31, 2018 December 31, 2017 One-to-four family residential real estate $ 92,056 $ 97,814 Multi-family mortgage 578,144 588,383 Nonresidential real estate 163,856 169,971 Construction and land 1,328 1,358 Commercial loans 162,564 152,552 Commercial leases 285,222 310,076 Consumer 1,494 1,597 1,284,664 1,321,751 Net deferred loan origination costs 1,230 1,266 Allowance for loan losses (8,341 ) (8,366 ) Loans, net $ 1,277,553 $ 1,314,651 The following tables present the balance in the allowance for loan losses and the loans receivable by portfolio segment and based on impairment method: Allowance for loan losses Loan Balances Individually evaluated for impairment Collectively evaluated for impairment Total Individually evaluated for impairment Collectively evaluated for impairment Total March 31, 2018 One-to-four family residential real estate $ — $ 765 $ 765 $ 3,576 $ 88,480 $ 92,056 Multi-family mortgage — 3,866 3,866 947 577,197 578,144 Nonresidential real estate — 1,577 1,577 — 163,856 163,856 Construction and land — 32 32 — 1,328 1,328 Commercial loans — 1,441 1,441 — 162,564 162,564 Commercial leases — 650 650 — 285,222 285,222 Consumer — 10 10 — 1,494 1,494 $ — $ 8,341 $ 8,341 $ 4,523 $ 1,280,141 1,284,664 Net deferred loan origination costs 1,230 Allowance for loan losses (8,341 ) Loans, net $ 1,277,553 Allowance for loan losses Loan Balances Individually evaluated for impairment Collectively evaluated for impairment Total Individually evaluated for impairment Collectively evaluated for impairment Total December 31, 2017 One-to-four family residential real estate $ — $ 850 $ 850 $ 4,265 $ 93,549 $ 97,814 Multi-family mortgage — 3,849 3,849 949 587,434 588,383 Nonresidential real estate — 1,605 1,605 — 169,971 169,971 Construction and land — 32 32 — 1,358 1,358 Commercial loans — 1,357 1,357 — 152,552 152,552 Commercial leases — 655 655 — 310,076 310,076 Consumer — 18 18 — 1,597 1,597 $ — $ 8,366 $ 8,366 $ 5,214 $ 1,316,537 1,321,751 Net deferred loan origination costs 1,266 Allowance for loan losses (8,366 ) Loans, net $ 1,314,651 Activity in the allowance for loan losses is as follows: Three Months Ended 2018 2017 Beginning balance $ 8,366 $ 8,127 Loans charged off: One-to-four family residential real estate (97 ) (171 ) Multi-family mortgage — (3 ) Nonresidential real estate — (165 ) (97 ) (339 ) Recoveries: One-to-four family residential real estate 99 6 Multi-family mortgage 8 11 Commercial loans 223 5 330 22 Net recoveries (charge-offs) 233 (317 ) Provision for (recovery of) loan losses (258 ) 161 Ending balance $ 8,341 $ 7,971 The following tables present the recorded investment in nonaccrual loans and loans past due over 90 days still on accrual by class of loans: Loan Balance Recorded Investment Loans Past Due Over 90 Days, Still Accruing March 31, 2018 One-to-four family residential real estate $ 1,675 $ 1,543 $ — One-to-four family residential real estate – non-owner occupied 86 46 — Multi-family mortgage - Illinois 375 369 — $ 2,136 $ 1,958 $ — December 31, 2017 One-to-four family residential real estate $ 3,413 $ 1,918 $ — One-to-four family residential real estate – non-owner occupied 308 109 — Multi-family mortgage - Illinois 376 363 — $ 4,097 $ 2,390 $ — Nonaccrual loans and impaired loans are defined differently. Some loans may be included in both categories, and some loans may only be included in one category. Nonaccrual loans include both smaller balance homogeneous loans that are collectively evaluated for impairment and individually classified impaired loans. The Company’s reserve for uncollected loan interest was $76,000 and $103,000 at March 31, 2018 and December 31, 2017 , respectively. When a loan is on nonaccrual status and the ultimate collectability of the total principal of an impaired loan is in doubt, all payments are applied to principal under the cost recovery method. Alternatively, when a loan is on non-accrual status but there is doubt concerning only the ultimate collectability of interest, contractual interest is credited to interest income only when received, under the cash basis method pursuant to the provisions of FASB ASC 310–10, as applicable. In all cases, the average balances are calculated based on the month–end balances of the financing receivables within the period reported pursuant to the provisions of FASB ASC 310–10, as applicable. The following tables present the aging of the recorded investment of loans at March 31, 2018 by class of loans: 30-59 Days Past Due 60-89 Days Past Due 90 Days or Greater Past Due Total Past Due Loans Not Past Due Total One-to-four family residential real estate loans $ 1,875 $ 58 $ 1,398 $ 3,331 $ 68,216 $ 71,547 One-to-four family residential real estate loans – non-owner occupied 368 10 46 424 19,676 20,100 Multi-family mortgage - Illinois 268 — 271 539 273,950 274,489 Multi-family mortgage - Other — — — — 299,725 299,725 Nonresidential real estate 940 — — 940 161,265 162,205 Construction — — — — 1,096 1,096 Land — — — — 234 234 Commercial loans: Regional commercial banking — — — — 48,160 48,160 Health care — — — — 69,980 69,980 Direct commercial lessor — — — — 44,939 44,939 Commercial leases: Investment rated commercial leases 1,727 152 — 1,879 185,386 187,265 Other commercial leases 572 255 — 827 98,900 99,727 Consumer — 22 — 22 1,481 1,503 $ 5,750 $ 497 $ 1,715 $ 7,962 $ 1,273,008 $ 1,280,970 The following tables present the aging of the recorded investment of loans at December 31, 2017 by class of loans: 30-59 Days Past Due 60-89 Days Past Due 90 Days or Total Past Due Loans Not Past Due Total One-to-four family residential real estate loans $ 86 $ 99 $ 1,801 $ 1,986 $ 74,216 $ 76,202 One-to-four family residential real estate loans – non-owner occupied 10 3 86 99 20,944 21,043 Multi-family mortgage - Illinois 172 — 364 536 287,171 287,707 Multi-family mortgage - Other — — — — 296,440 296,440 Nonresidential real estate 608 — — 608 166,071 166,679 Construction — — — — 1,103 1,103 Land — — — — 259 259 Commercial loans: Regional commercial banking — — — — 40,935 40,935 Health care — — — — 71,738 71,738 Direct commercial lessor — — — — 40,237 40,237 Commercial leases: Investment rated commercial leases 934 — — 934 207,747 208,681 Other commercial leases 288 — — 288 102,873 103,161 Consumer — — — — 1,605 1,605 $ 2,098 $ 102 $ 2,251 $ 4,451 $ 1,311,339 $ 1,315,790 The Company evaluates loan extensions or modifications in accordance with FASB ASC 310–40 with respect to the classification of the loan as a Troubled Debt Restructuring ("TDR"). In general, if the Company grants a loan extension or modification to a borrower for other than an insignificant period of time that includes a below–market interest rate, principal forgiveness, payment forbearance or other concession intended to minimize the economic loss to the Company, the loan extension or loan modification is classified as a TDR. In cases where borrowers are granted new terms that provide for a reduction of either interest or principal then due and payable, management measures any impairment on the restructured loan in the same manner as for impaired loans as noted above. The Company had $17,000 of TDRs at March 31, 2018 and December 31, 2017 . No specific valuation reserves were allocated to those loans at March 31, 2018 and December 31, 2017 . The Company had no outstanding commitments to borrowers whose loans were classified as TDRs at either date. The following table presents loans classified as TDRs: March 31, 2018 December 31, 2017 One-to-four family residential real estate - nonaccrual $ 17 $ 17 During the three months ended March 31, 2018 and 2017 , there were no loans modified and classified as TDRs. A TDR is considered to be in payment default once it is 90 days contractually past due under the modified terms. There were no payment defaults on TDRs during the three months ended March 31, 2018 and 2017 within twelve months following the modification. There were no loan modifications during the three months ended March 31, 2018 . There were certain loan modifications during the three months ended March 31, 2017 that did not meet the definition of a TDR. These loans had a total recorded investment of $133,000 at March 31, 2017 . The modification of these loans involved either a modification of the terms of a loan to borrowers who were not experiencing financial difficulties or a delay in a payment that was considered to be insignificant. In order to determine whether a borrower is experiencing financial difficulty, an evaluation is performed of the probability that the borrower will be in payment default on any of its debt in the foreseeable future without the modification. This evaluation is performed under the Company’s internal underwriting policy. The Company categorizes loans into risk categories based on relevant information about the ability of borrowers to service their debt, including current financial information, historical payment experience, credit documentation, public information, and current economic trends, among other factors. The Company analyzes loans individually by classifying the loans based on credit risk. This analysis includes non-homogeneous loans, such as commercial and commercial real estate loans. This analysis is performed on a monthly basis. The Company uses the following definitions for risk ratings: Special Mention. A Special Mention asset has potential weaknesses that deserve management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the asset or in the institution’s credit position at some future date. Special Mention assets are not adversely classified and do not expose an institution to sufficient risk to warrant adverse classification. Substandard. Loans categorized as Substandard continue to accrue interest, but exhibit a well-defined weakness or weaknesses that may jeopardize the liquidation of the debt. The loans continue to accrue interest because they are well secured and collection of principal and interest is expected within a reasonable time. The risk rating guidance published by the Office of the Comptroller of the Currency clarifies that a loan with a well-defined weakness does not have to present a probability of default for the loan to be rated Substandard, and that an individual loan’s loss potential does not have to be distinct for the loan to be rated Substandard. Nonaccrual. An asset classified Nonaccrual has all the weaknesses inherent in one classified Substandard with the added characteristic that the weaknesses make collection or liquidation in full, on the basis of currently existing facts, conditions, and values, highly questionable and improbable. Loans not meeting the criteria above that are analyzed individually as part of the above described process are considered “Pass” rated loans. As of March 31, 2018 , based on the most recent analysis performed, the risk categories of loans by class of loans are as follows: Pass Special Mention Substandard Nonaccrual Total One-to-four family residential real estate loans $ 70,004 $ — $ 323 $ 1,539 $ 71,866 One-to-four family residential real estate loans – non-owner occupied 20,105 — 39 46 20,190 Multi-family mortgage loans - Illinois 275,552 — 222 370 276,144 Multi-family mortgage loans - Other 302,000 — — — 302,000 Nonresidential real estate loans 163,707 — 149 — 163,856 Construction loans 1,093 — — — 1,093 Land loans 235 — — — 235 Commercial loans: Regional commercial banking 43,467 4,644 — — 48,111 Health care 67,669 — 2,258 — 69,927 Direct commercial lessor 44,526 — — — 44,526 Commercial leases: Investment rated commercial leases 186,052 — — — 186,052 Other commercial leases 99,170 — — — 99,170 Consumer 1,494 — — — 1,494 $ 1,275,074 $ 4,644 $ 2,991 $ 1,955 $ 1,284,664 As of December 31, 2017 , the risk categories of loans by class of loans are as follows: Pass Special Mention Substandard Nonaccrual Total One-to-four family residential real estate loans $ 74,437 $ — $ 255 $ 1,914 $ 76,606 One-to-four family residential real estate loans – non-owner occupied 21,059 — 40 109 21,208 Multi-family mortgage loans - Illinois 290,765 — 225 368 291,358 Multi-family mortgage loans - Other 297,025 — — — 297,025 Nonresidential real estate loans 169,817 — 154 — 169,971 Construction loans 1,099 — — — 1,099 Land loans 259 — — — 259 Commercial loans: Regional commercial banking 36,373 4,528 — — 40,901 Health care 69,480 — 2,248 — 71,728 Direct commercial lessor 39,923 — — — 39,923 Commercial leases: Investment rated commercial leases 207,460 — — — 207,460 Other commercial leases 102,616 — — — 102,616 Consumer 1,597 — — — 1,597 $ 1,311,910 $ 4,528 $ 2,922 $ 2,391 $ 1,321,751
Loans receivable	Loans receivable are as follows: March 31, 2018 December 31, 2017 One-to-four family residential real estate $ 92,056 $ 97,814 Multi-family mortgage 578,144 588,383 Nonresidential real estate 163,856 169,971 Construction and land 1,328 1,358 Commercial loans 162,564 152,552 Commercial leases 285,222 310,076 Consumer 1,494 1,597 1,284,664 1,321,751 Net deferred loan origination costs 1,230 1,266 Allowance for loan losses (8,341 ) (8,366 ) Loans, net $ 1,277,553 $ 1,314,651
Loans Receivable Based On Impairment Method [Table Text Block]	The following tables present the balance in the allowance for loan losses and the loans receivable by portfolio segment and based on impairment method: Allowance for loan losses Loan Balances Individually evaluated for impairment Collectively evaluated for impairment Total Individually evaluated for impairment Collectively evaluated for impairment Total March 31, 2018 One-to-four family residential real estate $ — $ 765 $ 765 $ 3,576 $ 88,480 $ 92,056 Multi-family mortgage — 3,866 3,866 947 577,197 578,144 Nonresidential real estate — 1,577 1,577 — 163,856 163,856 Construction and land — 32 32 — 1,328 1,328 Commercial loans — 1,441 1,441 — 162,564 162,564 Commercial leases — 650 650 — 285,222 285,222 Consumer — 10 10 — 1,494 1,494 $ — $ 8,341 $ 8,341 $ 4,523 $ 1,280,141 1,284,664 Net deferred loan origination costs 1,230 Allowance for loan losses (8,341 ) Loans, net $ 1,277,553
Allowance for loan losses	ctivity in the allowance for loan losses is as follows: Three Months Ended 2018 2017 Beginning balance $ 8,366 $ 8,127 Loans charged off: One-to-four family residential real estate (97 ) (171 ) Multi-family mortgage — (3 ) Nonresidential real estate — (165 ) (97 ) (339 ) Recoveries: One-to-four family residential real estate 99 6 Multi-family mortgage 8 11 Commercial loans 223 5 330 22 Net recoveries (charge-offs) 233 (317 ) Provision for (recovery of) loan losses (258 ) 161 Ending balance $ 8,341 $ 7,971
Schedule of Financing Receivables, Non Accrual Status	The following tables present the recorded investment in nonaccrual loans and loans past due over 90 days still on accrual by class of loans: Loan Balance Recorded Investment Loans Past Due Over 90 Days, Still Accruing March 31, 2018 One-to-four family residential real estate $ 1,675 $ 1,543 $ — One-to-four family residential real estate – non-owner occupied 86 46 — Multi-family mortgage - Illinois 375 369 — $ 2,136 $ 1,958 $ — December 31, 2017 One-to-four family residential real estate $ 3,413 $ 1,918 $ — One-to-four family residential real estate – non-owner occupied 308 109 — Multi-family mortgage - Illinois 376 363 — $ 4,097 $ 2,390 $ —
Past Due Financing Receivables	The following tables present the aging of the recorded investment of loans at March 31, 2018 by class of loans: 30-59 Days Past Due 60-89 Days Past Due 90 Days or Greater Past Due Total Past Due Loans Not Past Due Total One-to-four family residential real estate loans $ 1,875 $ 58 $ 1,398 $ 3,331 $ 68,216 $ 71,547 One-to-four family residential real estate loans – non-owner occupied 368 10 46 424 19,676 20,100 Multi-family mortgage - Illinois 268 — 271 539 273,950 274,489 Multi-family mortgage - Other — — — — 299,725 299,725 Nonresidential real estate 940 — — 940 161,265 162,205 Construction — — — — 1,096 1,096 Land — — — — 234 234 Commercial loans: Regional commercial banking — — — — 48,160 48,160 Health care — — — — 69,980 69,980 Direct commercial lessor — — — — 44,939 44,939 Commercial leases: Investment rated commercial leases 1,727 152 — 1,879 185,386 187,265 Other commercial leases 572 255 — 827 98,900 99,727 Consumer — 22 — 22 1,481 1,503 $ 5,750 $ 497 $ 1,715 $ 7,962 $ 1,273,008 $ 1,280,970
Troubled Debt Restructurings on Financing Receivables	The following table presents loans classified as TDRs: March 31, 2018 December 31, 2017 One-to-four family residential real estate - nonaccrual $ 17 $ 17
Financing Receivable Credit Quality Indicators	As of March 31, 2018 , based on the most recent analysis performed, the risk categories of loans by class of loans are as follows: Pass Special Mention Substandard Nonaccrual Total One-to-four family residential real estate loans $ 70,004 $ — $ 323 $ 1,539 $ 71,866 One-to-four family residential real estate loans – non-owner occupied 20,105 — 39 46 20,190 Multi-family mortgage loans - Illinois 275,552 — 222 370 276,144 Multi-family mortgage loans - Other 302,000 — — — 302,000 Nonresidential real estate loans 163,707 — 149 — 163,856 Construction loans 1,093 — — — 1,093 Land loans 235 — — — 235 Commercial loans: Regional commercial banking 43,467 4,644 — — 48,111 Health care 67,669 — 2,258 — 69,927 Direct commercial lessor 44,526 — — — 44,526 Commercial leases: Investment rated commercial leases 186,052 — — — 186,052 Other commercial leases 99,170 — — — 99,170 Consumer 1,494 — — — 1,494 $ 1,275,074 $ 4,644 $ 2,991 $ 1,955 $ 1,284,664
Loans By Class Modified As Troubled Debt Restructuring On Financing Receivables [Table Text Block]

Other Real Estate Owned (Tables

Other Real Estate Owned (Tables)	3 Months Ended
	Mar. 31, 2018
Other Real Estate [Abstract]
Schedule of Real Estate Properties [Table Text Block]	March 31, 2018 December 31, 2017 Balance Valuation Allowance Net OREO Balance Balance Valuation Allowance Net OREO Balance One–to–four family residential $ 935 $ — $ 935 $ 836 $ (9 ) $ 827 Nonresidential real estate 1,140 (277 ) 863 1,772 (252 ) 1,520 Land 48 (44 ) 4 48 (44 ) 4 $ 2,123 $ (321 ) $ 1,802 $ 2,656 $ (305 ) $ 2,351
Real Estate Owned, rollforward [Table Text Block]	March 31, 2018 December 31, 2017 Balance Valuation Allowance Net OREO Balance Balance Valuation Allowance Net OREO Balance One–to–four family residential $ 935 $ — $ 935 $ 836 $ (9 ) $ 827 Nonresidential real estate 1,140 (277 ) 863 1,772 (252 ) 1,520 Land 48 (44 ) 4 48 (44 ) 4 $ 2,123 $ (321 ) $ 1,802 $ 2,656 $ (305 ) $ 2,351 The following represents the roll forward of OREO and the composition of OREO properties: For the Three Months Ended March 31, 2018 2017 Beginning balance $ 2,351 $ 3,895 New foreclosed properties 562 1,936 Valuation adjustments (25 ) (20 ) Sales and payments (1,086 ) (510 ) Ending balance $ 1,802 $ 5,301
OREO valuation allowance, rollforward [Table Text Block]	Activity in the valuation allowance is as follows: For the Three Months Ended March 31, 2018 2017 Beginning balance $ 305 $ 449 Additions charged to expense 25 20 Reductions from sales of OREO (9 ) (59 ) Ending balance $ 321 $ 410 At March 31, 2018 , the balance of OREO included no foreclosed residential real estate properties recorded as a result of obtaining physical possession of the property without title. At December 31, 2017 the balance of OREO included $352,000 foreclosed residential real estate properties recorded as a result of obtaining physical possession of the property without title. At March 31, 2018 and December 31, 2017 , the recorded investment of consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings were in process was $1.3 million and $1.5 million , respectively.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Compensation and Retirement Disclosure [Abstract]
Schedule of Employee Stock Ownership Plan (ESOP) Disclosures	Shares held by the ESOP were as follows: March 31, 2018 December 31, 2017 Allocated to participants 1,203,810 1,125,448 Distributed to participants (317,914 ) (313,223 ) Unearned — 831,852 Total ESOP shares 885,896 1,644,077 Fair value of unearned shares $ — $ 12,328

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Stock Option Activity	A summary of the activity in the stock option plan for 2018 and 2016 follows: Stock Options Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (1) Stock options outstanding at December 31, 2015 1,752,156 $ 12.30 1.48 $ 778 Stock options granted — — Stock options exercised — — Stock options outstanding at December 31, 2016 1,752,156 $ 12.30 0.48 $ 4,422 Stock options granted — — Stock options exercised (1,752,156 ) 12.30 Stock options outstanding at September 30, 2017 — $ — 0 $ — (1) Stock option aggregate intrinsic value represents the number of shares subject to options multiplied by the difference (if positive) in the closing market price of the common stock underlying the options on the date shown and the weighted average exercise price.

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Company's financial instruments measured at fair values	The following table sets forth the Company’s financial assets that were accounted for at fair value and are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value March 31, 2018 Securities: Certificates of deposit $ — $ 86,340 $ — $ 86,340 Equity mutual fund 491 — — 491 Mortgage-backed securities – residential — 11,544 — 11,544 Collateralized mortgage obligations – residential — 4,277 — 4,277 SBA-guaranteed loan participation certificates — 9 — 9 $ 491 $ 102,170 $ — $ 102,661 December 31, 2017 Securities: Certificates of deposit $ — $ 75,916 $ — $ 75,916 Equity mutual fund 499 — — 499 Mortgage-backed securities - residential — 12,472 — 12,472 Collateralized mortgage obligations – residential — 4,486 — 4,486 SBA-guaranteed loan participation certificates — 10 — 10 $ 499 $ 92,884 $ — $ 93,383
Schedule of Company's financial instruments measured on non recurring at fair values	The following table sets forth the Company’s assets that were measured at fair value on a non-recurring basis: Fair Value Measurement Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value March 31, 2018 Other real estate owned - nonresidential real estate $ — $ — $ 409 $ 409 December 31, 2017 Other real estate owned: One-to-four family residential real estate $ — $ — $ 102 $ 102 Nonresidential real estate — — 814 814 $ — $ — $ 916 $ 916
Schedule of fair value quantitative information	The following table presents quantitative information, based on certain empirical data with respect to Level 3 fair value measurements for financial instruments measured at fair value on a non-recurring basis: Fair Value Valuation Significant Unobservable Range March 31, 2018 Other real estate owned - nonresidential real estate loans $ 409 Sales comparison Comparison between sales and income approaches 12.70% to 26.77% December 31, 2017 Other real estate owned One-to-four family residential real estate $ 102 Sales comparison Discount applied to valuation 5.6% Nonresidential real estate 814 Sales comparison Comparison between sales and income approaches -3.66% to 15.22% (11.0%) $ 916
Carrying amount and estimated fair value of financial instruments	The carrying amount and estimated fair value of financial instruments are as follows: Fair Value Measurements at March 31, 2018 Using: Carrying Amount Level 1 Level 2 Level 3 Total Financial assets Cash and cash equivalents $ 92,576 $ 10,613 $ 81,963 $ — $ 92,576 Securities 102,661 491 102,170 — 102,661 Loans receivable, net of allowance for loan losses 1,277,553 — — 1,276,635 1,276,635 FHLB and FRB stock 8,290 — — — N/A Accrued interest receivable 4,900 — 4,900 — 4,900 Financial liabilities Noninterest-bearing demand deposits $ 232,593 $ — $ 232,593 $ — $ 232,593 NOW and money market accounts 573,886 — 573,886 — 573,886 Savings deposits 160,093 — 160,093 — 160,093 Certificates of deposit 311,435 — 308,904 — 308,904 Borrowings 60,983 — 60,832 — 60,832 Accrued interest payable 180 — 180 — 180 Fair Value Measurements at December 31, 2017 Using: Carrying Amount Level 1 Level 2 Level 3 Total Financial assets Cash and cash equivalents $ 127,592 $ 13,572 $ 114,020 $ — $ 127,592 Securities 93,383 499 92,884 — 93,383 Loans receivable, net of allowance for loan losses 1,314,651 — 1,323,139 — 1,323,139 FHLB and FRB stock 8,290 — — — N/A Accrued interest receivable 4,619 — 4,619 — 4,619 Financial liabilities Noninterest-bearing demand deposits $ 234,354 $ — $ 234,354 $ — $ 234,354 NOW and money market accounts 589,238 — 589,238 — 589,238 Savings deposits 160,501 — 160,501 — 160,501 Certificates of deposit 355,958 — 353,969 — 353,969 Borrowings 60,768 — 60,627 — 60,627 Accrued interest payable 147 — 147 — 147

Revenue From Contracts With C28

Revenue From Contracts With Customers (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Noninterest Income Outside the Scope of ASC 606	The following table presents the Company's sources of noninterest income for the three months ended March 31, 2018 and 2017 . Items outside of the scope of the ASC 606 are noted as such. Three Months Ended 2018 2017 Deposit service charges and fees $ 978 $ 950 Loan fee income (1) 70 60 Commercial mortgage brokerage fees (1) 41 — Residential mortgage banking fees (1) 30 44 Trust and insurance commissions and annuities income 213 249 Earnings on bank owned life insurance (1) 66 63 Other (1) 141 178 Total noninterest income $ 1,539 $ 1,544 (1) Not within the scope of ASC 606

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Basic and Diluted [Abstract]
Net income available to common stockholders	$ 3,559	$ 1,881
Average common shares outstanding (shares)	17,931,579	19,243,941
Less:
Unearned ESOP shares (shares)	0	(600,947)
Unvested restricted stock shares (shares)	(940)	(940)
Weighted average common shares outstanding (shares)	17,930,639	18,642,054
Add - Net effect of dilutive stock options and unvested restricted stock	461	5,462
Weighted average diluted common shares outstanding (shares)	17,931,100	18,647,516
Basic earnings per common share (usd per share)	$ 0.20	$ 0.10
Diluted earnings per common share (usd per share)	$ 0.20	$ 0.10

Securities - Fair Value of Secu

Securities - Fair Value of Securites (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Unrealized gains and losses recognized in accumulated other comprehensive income (loss)
Amortized Cost	$ 101,767	$ 92,876
Available for sale securities, accumulated gross unrealized gain before tax	457	536
Available for sale securities, accumulated gross unrealized loss before tax	(54)	(29)
Total Fair value	102,170	93,383
Certificates of deposit [Member]
Unrealized gains and losses recognized in accumulated other comprehensive income (loss)
Amortized Cost	86,340	75,916
Available for sale securities, accumulated gross unrealized gain before tax	0	0
Available for sale securities, accumulated gross unrealized loss before tax	0	0
Total Fair value	86,340	75,916
Equity mutual fund [Member]
Unrealized gains and losses recognized in accumulated other comprehensive income (loss)
Amortized Cost		500
Available for sale securities, accumulated gross unrealized gain before tax		0
Available for sale securities, accumulated gross unrealized loss before tax		(1)
Total Fair value	491	499
Mortgage - backed securities - residential [Member]
Unrealized gains and losses recognized in accumulated other comprehensive income (loss)
Amortized Cost	11,146	11,969
Available for sale securities, accumulated gross unrealized gain before tax	441	520
Available for sale securities, accumulated gross unrealized loss before tax	(43)	(17)
Total Fair value	11,544	12,472
Collateralized mortgage obligations - residential [Member]
Unrealized gains and losses recognized in accumulated other comprehensive income (loss)
Amortized Cost	4,272	4,481
Available for sale securities, accumulated gross unrealized gain before tax	16	16
Available for sale securities, accumulated gross unrealized loss before tax	(11)	(11)
Total Fair value	4,277	4,486
SBA-guaranteed loan participation certificates [Member]
Unrealized gains and losses recognized in accumulated other comprehensive income (loss)
Amortized Cost	9	10
Available for sale securities, accumulated gross unrealized gain before tax	0	0
Available for sale securities, accumulated gross unrealized loss before tax	0	0
Total Fair value	$ 9	$ 10

Securities - Amortized Cost and

Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortized cost and fair values of securities
Due in one year or less, amortized cost	$ 86,340
Due in one year or less, fair value	86,340
Total amortized cost	101,767	$ 92,876
Total Fair value	102,170	93,383
Equity mutual fund [Member]
Amortized cost and fair values of securities
Total amortized cost		500
Total Fair value	491	499
Mortgage - backed securities - residential [Member]
Amortized cost and fair values of securities
Total amortized cost	11,146	11,969
Total Fair value	11,544	12,472
Collateralized mortgage obligations - residential [Member]
Amortized cost and fair values of securities
Total amortized cost	4,272	4,481
Total Fair value	4,277	4,486
SBA-guaranteed loan participation certificates [Member]
Amortized cost and fair values of securities
Total amortized cost	9	10
Total Fair value	$ 9	$ 10

Securities - Proceeds and Gross

Securities - Proceeds and Gross Gains (Losses) From Sale of Securities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Proceeds and Gross Gains (Losses) from Sale of Securities [Abstract]
Gain on Sale of Securities, Net	$ 0

Securities - Unrealized Losses

Securities - Unrealized Losses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Amortized cost and fair values of securities
Less than 12 Months, Fair Value	$ 0	$ 499
12 Months or More, Fair Value	3,094	3,232
Fair Value, Total	3,094	3,731
Unrealized loss of securities
Less than 12 Months, Unrealized Loss	0	(1)
12 Months or More, Unrealized Loss	(54)	(28)
Unrealized Loss, Total	(54)	(29)
Mortgage Backed Securities Residential [Member]
Amortized cost and fair values of securities
Less than 12 Months, Fair Value	0	0
12 Months or More, Fair Value	1,111	1,149
Fair Value, Total	1,111	1,149
Unrealized loss of securities
Less than 12 Months, Unrealized Loss	0	0
12 Months or More, Unrealized Loss	(43)	(17)
Unrealized Loss, Total	(43)	(17)
Collateralized mortgage obligations - residential [Member]
Amortized cost and fair values of securities
Less than 12 Months, Fair Value	0	0
12 Months or More, Fair Value	1,983	2,083
Fair Value, Total	1,983	2,083
Unrealized loss of securities
Less than 12 Months, Unrealized Loss	0	0
12 Months or More, Unrealized Loss	(11)	(11)
Unrealized Loss, Total	$ (11)	(11)
Equity Funds [Member]
Amortized cost and fair values of securities
Less than 12 Months, Fair Value		499
12 Months or More, Fair Value		0
Fair Value, Total		499
Unrealized loss of securities
Less than 12 Months, Unrealized Loss		(1)
12 Months or More, Unrealized Loss		0
Unrealized Loss, Total		$ (1)

Loans Receivable (Details)

Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Loans receivable
Total loans	$ 1,284,664	$ 1,321,751
Net deferred loan origination costs	1,230	1,266
Allowance for loan losses	(8,341)	(8,366)	$ (7,971)	$ (8,127)
Loans, net	1,277,553	1,314,651
One-to-four family residential real estate loans [Member]
Loans receivable
Total loans	92,056	97,814
Allowance for loan losses	(765)	(850)
Multi-family mortgage loans [Member]
Loans receivable
Total loans	578,144	588,383
Allowance for loan losses	(3,866)	(3,849)
Nonresidential real estate loans [Member]
Loans receivable
Total loans	163,856	169,971
Allowance for loan losses	(1,577)	(1,605)
Construction and land loans [Member]
Loans receivable
Total loans	1,328	1,358
Allowance for loan losses	(32)	(32)
Commercial loans [Member]
Loans receivable
Total loans	162,564	152,552
Allowance for loan losses	(1,441)	(1,357)
Commercial leases [Member]
Loans receivable
Total loans	285,222	310,076
Allowance for loan losses	(650)	(655)
Consumer loans [Member]
Loans receivable
Total loans	1,494	1,597
Allowance for loan losses	$ (10)	$ (18)

Loans Receivable - Loan Origina

Loans Receivable - Loan Origination and Risk Management (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	$ 1,284,664	$ 1,321,751
Multi-family mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	578,144	588,383
Nonresidential Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	163,856	169,971
Commercial leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	$ 285,222	$ 310,076

Loans Receivable - Allowance fo

Loans Receivable - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Allowance for loan losses and the loans receivable by portfolio segment
Net deferred loan origination costs	$ 1,230	$ 1,266
Loans, net	$ 1,277,553	$ 1,314,651

Loans Receivable - Activity in

Loans Receivable - Activity in the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 8,366	$ 8,127
Loans charged off	97	339
Recoveries	330	22
Net charge-off	(233)	317
Provision for (recovery of) loan losses	(258)	161
Ending balance	8,341	7,971
One-to-four family residential real estate loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	850
Loans charged off	(97)	(171)
Recoveries	99	6
Ending balance	765
Multi-family mortgage loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,849
Loans charged off	0	(3)
Recoveries	8	11
Ending balance	3,866
Nonresidential real estate loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,605
Loans charged off	0	(165)
Ending balance	1,577
Construction and land loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	32
Ending balance	32
Commercial loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,357
Recoveries	223	$ 5
Ending balance	1,441
Commercial leases [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	655
Ending balance	650
Consumer loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	18
Ending balance	$ 10

Loans Receivable - Loans Indivi

Loans Receivable - Loans Individually Evaluated for Impairment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 1,284,664	$ 1,321,751
Loans individually evaluated for impairment by class loans
Loan Balance		6,007
Recorded Investment		5,196
Partial Charge-off		806
Average Investment in Impaired Loans		5,059
Interest Income Recognized		238
Allowance for loan losses (With an allowance recorded)	0	0
Impaired Loan, Total	5,163
Recorded Investment, Total	4,506
Partial Charge-offs, Total	651
Average Investment in Impaired Loans, Total	4,954
Interest Income Recognized, Total	26
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	8,341	8,366
Net deferred loan origination costs	1,230	1,266
Loans and Leases Receivable, Allowance	8,341	8,366	$ 7,971	$ 8,127
Financing Receivable, Individually Evaluated for Impairment	4,523	5,214
Financing Receivable, Collectively Evaluated for Impairment	1,280,141	1,316,537
Loans, net	1,277,553	1,314,651
One-to-four family residential real estate loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	92,056	97,814
Loans individually evaluated for impairment by class loans
Loan Balance	4,211	5,049
Recorded Investment	3,556	4,248
Partial Charge-off	651	806
Average Investment in Impaired Loans	4,002	4,212
Interest Income Recognized	15	197
Allowance for loan losses (With an allowance recorded)	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	765	850
Loans and Leases Receivable, Allowance	765	850
Financing Receivable, Individually Evaluated for Impairment	3,576	4,265
Financing Receivable, Collectively Evaluated for Impairment	88,480	93,549
One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	20,190	21,208
Multi-family mortgage loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	578,144	588,383
Loans individually evaluated for impairment by class loans
Loan Balance	952	958
Recorded Investment	950	948
Partial Charge-off	0	0
Average Investment in Impaired Loans	952	847
Interest Income Recognized	11	41
Allowance for loan losses (With an allowance recorded)	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,866	3,849
Loans and Leases Receivable, Allowance	3,866	3,849
Financing Receivable, Individually Evaluated for Impairment	947	949
Financing Receivable, Collectively Evaluated for Impairment	577,197	587,434
Multi Family Mortgage Loans without wholesale [Member] [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	276,144	291,358
Wholesale commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	302,000	297,025
Nonresidential real estate loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	163,856	169,971
Loans individually evaluated for impairment by class loans
Allowance for loan losses (With an allowance recorded)	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,577	1,605
Loans and Leases Receivable, Allowance	1,577	1,605
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	163,856	169,971
Construction Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,093	1,099
Land loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	235	259
Commercial loans - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	48,111	40,901
Commercial loans - other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	99,170	102,616
Consumer loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,494	1,597
Loans individually evaluated for impairment by class loans
Allowance for loan losses (With an allowance recorded)	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	10	18
Loans and Leases Receivable, Allowance	10	18
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	1,494	1,597
Construction And Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,328	1,358
Loans individually evaluated for impairment by class loans
Allowance for loan losses (With an allowance recorded)	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	32	32
Loans and Leases Receivable, Allowance	32	32
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	1,328	1,358
Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	162,564	152,552
Loans individually evaluated for impairment by class loans
Allowance for loan losses (With an allowance recorded)	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,441	1,357
Loans and Leases Receivable, Allowance	1,441	1,357
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	162,564	152,552
Finance Leases Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	285,222	310,076
Loans individually evaluated for impairment by class loans
Allowance for loan losses (With an allowance recorded)	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	650	655
Loans and Leases Receivable, Allowance	650	655
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	285,222	310,076
One to Four Family Residential Real Estate Loans-Owner occupied [Member] [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 71,866	$ 76,606

Loans Receivable - Nonaccrual L

Loans Receivable - Nonaccrual Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Reserve For Uncollected Loan Interest	$ 76	$ 103
Unpaid Principal Balance	2,136	4,097
Recorded Investment	1,958	2,390
Loans Past Due Over 90 Days, still accruing	0	0
One-to-four family residential real estate loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Principal Balance	1,675	3,413
Recorded Investment	1,543	1,918
Loans Past Due Over 90 Days, still accruing	0	0
One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Principal Balance	86	308
Recorded Investment	46	109
Loans Past Due Over 90 Days, still accruing	0	0
Multi-family mortgage loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Principal Balance	375	376
Recorded Investment	369	363
Loans Past Due Over 90 Days, still accruing	$ 0	$ 0

Loans Receivable - Past Due Loa

Loans Receivable - Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	$ 7,962	$ 4,451
Recorded Investment, Loans Not Past Due	1,273,008	1,311,339
Recorded investment, total	1,280,970	1,315,790
Commercial Leases Investment Rated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	1,879	934
Recorded Investment, Loans Not Past Due	185,386	207,747
Recorded investment, total	187,265	208,681
Commercial Loans Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	827	288
Recorded Investment, Loans Not Past Due	98,900	102,873
Recorded investment, total	99,727	103,161
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	22	0
Recorded Investment, Loans Not Past Due	1,481	1,605
Recorded investment, total	1,503	1,605
Commercial Loans Health Care [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Loans Not Past Due	69,980	71,738
Recorded investment, total	69,980	71,738
Commercial Loans Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Recorded Investment, Loans Not Past Due	44,939	40,237
Recorded investment, total	44,939	40,237
Commercial loans - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Commercial loans - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Recorded Investment, Loans Not Past Due	48,160	40,935
Recorded investment, total	48,160	40,935
Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Recorded Investment, Loans Not Past Due	234	259
Recorded investment, total	234	259
Construction Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Recorded Investment, Loans Not Past Due	1,096	1,103
Recorded investment, total	1,096	1,103
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	940	608
Recorded Investment, Loans Not Past Due	161,265	166,071
Recorded investment, total	162,205	166,679
Wholesale Commercial Lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Recorded Investment, Loans Not Past Due	299,725	296,440
Recorded investment, total	299,725	296,440
Multi Family Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	539	536
Recorded Investment, Loans Not Past Due	273,950	287,171
Recorded investment, total	274,489	287,707
One To Four Family Residential Real Estate Loans Non Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	424	99
Recorded Investment, Loans Not Past Due	19,676	20,944
Recorded investment, total	20,100	21,043
One to Four Family Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	3,331	1,986
Recorded Investment, Loans Not Past Due	68,216	74,216
Recorded investment, total	71,547	76,202
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	5,750	2,098
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Leases Investment Rated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	1,727	934
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Loans Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	572	288
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Loans Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial loans - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial loans - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	940	608
Financing Receivables, 30 to 59 Days Past Due [Member] | Wholesale Commercial Lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Multi Family Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	268	172
Financing Receivables, 30 to 59 Days Past Due [Member] | One To Four Family Residential Real Estate Loans Non Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	368	10
Financing Receivables, 30 to 59 Days Past Due [Member] | One to Four Family Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	1,875	86
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	497	102
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Leases Investment Rated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due		0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Loans Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	255	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	22	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Loans Health Care [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	152
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Loans Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial loans - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial loans - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Wholesale Commercial Lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Multi Family Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | One To Four Family Residential Real Estate Loans Non Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	10	3
Financing Receivables, 60 to 89 Days Past Due [Member] | One to Four Family Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	58	99
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Leases Investment Rated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	1,715	2,251
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Loans Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Loans Health Care [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Loans Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial loans - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial loans - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Wholesale Commercial Lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Multi Family Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	271	364
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | One To Four Family Residential Real Estate Loans Non Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	46	86
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | One to Four Family Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment, Total Past Due	$ 1,398	$ 1,801

Loans Receivable - Troubled Deb

Loans Receivable - Troubled Debt Restructuring (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Outstanding Commitments To Borrowers Loans Classified As Troubled Debt Restructurings	$ 0	$ 0
Troubled Debt Restructurings
Financing receivable modifications	17,000
One-to-four family residential real estate loans - non-owner occupied loans [Member] | Non Accrual Loans [Member]
Troubled Debt Restructurings
Financing receivable modifications	17,000	17,000
Allowance for Loan and Lease Losses [Member]
Troubled Debt Restructurings
Valuation Allowances and Reserves, Balance	$ 0	$ 0

Loans Receivable - Modified Tro

Loans Receivable - Modified Troubled Debt Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Modifications [Line Items]
Loans modified	$ 0	$ 133

Loans Receivable - Credit Quali

Loans Receivable - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 7,962	$ 4,451
Financing Receivable Credit Quality Indicators
Total loans	1,284,664	1,321,751
One-to-four family residential real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	3,331	1,986
Financing Receivable Credit Quality Indicators
Total loans	92,056	97,814
One to Four Family Residential Real Estate Loans-Owner occupied [Member] [Member]
Financing Receivable Credit Quality Indicators
Total loans	71,866	76,606
One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	424	99
Financing Receivable Credit Quality Indicators
Total loans	20,190	21,208
Multi-family mortgage loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	539	536
Financing Receivable Credit Quality Indicators
Total loans	578,144	588,383
Multi Family Mortgage Loans without wholesale [Member] [Member]
Financing Receivable Credit Quality Indicators
Total loans	276,144	291,358
Wholesale commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivable Credit Quality Indicators
Total loans	302,000	297,025
Nonresidential Real Estate Loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	163,856	169,971
Construction loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivable Credit Quality Indicators
Total loans	1,093	1,099
Land loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivable Credit Quality Indicators
Total loans	235	259
Commercial loans - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivable Credit Quality Indicators
Total loans	48,111	40,901
Commercial Loans - Municipal loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivable Credit Quality Indicators
Total loans	44,526	39,923
Commercial Loans - Warehouse Lines [Member]
Financing Receivable Credit Quality Indicators
Total loans
Commercial Loans - Health Care [Member]
Financing Receivable Credit Quality Indicators
Total loans	69,927	71,728
Commercial loans - other [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	827	288
Financing Receivable Credit Quality Indicators
Total loans	99,170	102,616
Commercial Leases - Investment Rated [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,879	934
Financing Receivable Credit Quality Indicators
Total loans	186,052	207,460
Consumer loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	1,494	1,597
Nonaccrual [Member]
Financing Receivable Credit Quality Indicators
Total loans	1,955	2,391
Nonaccrual [Member] | One-to-four family residential real estate loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	1,539	1,914
Nonaccrual [Member] | One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	46	109
Nonaccrual [Member] | Multi-family mortgage loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	370	368
Nonaccrual [Member] | Wholesale commercial lending [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Nonresidential Real Estate Loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Construction loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Land loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Commercial loans - Secured [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Commercial Loans - Municipal loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Commercial Loans - Health Care [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Commercial loans - other [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Nonaccrual [Member] | Commercial Leases - Investment Rated [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member]
Financing Receivable Credit Quality Indicators
Total loans	2,991	2,922
Substandard [Member] | One-to-four family residential real estate loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	323	255
Substandard [Member] | One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	39	40
Substandard [Member] | Multi-family mortgage loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	222	225
Substandard [Member] | Wholesale commercial lending [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member] | Nonresidential Real Estate Loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	149	154
Substandard [Member] | Construction loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member] | Land loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member] | Commercial loans - Secured [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member] | Commercial Loans - Municipal loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member] | Commercial Loans - Health Care [Member]
Financing Receivable Credit Quality Indicators
Total loans	2,258	2,248
Substandard [Member] | Commercial loans - other [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member] | Commercial Leases - Investment Rated [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Substandard [Member] | Consumer loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Pass [Member]
Financing Receivable Credit Quality Indicators
Total loans	1,275,074	1,311,910
Pass [Member] | One-to-four family residential real estate loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	70,004	74,437
Pass [Member] | One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	20,105	21,059
Pass [Member] | Multi-family mortgage loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	275,552	290,765
Pass [Member] | Wholesale commercial lending [Member]
Financing Receivable Credit Quality Indicators
Total loans	302,000	297,025
Pass [Member] | Nonresidential Real Estate Loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	163,707	169,817
Pass [Member] | Construction loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	1,093	1,099
Pass [Member] | Land loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	235	259
Pass [Member] | Commercial loans - Secured [Member]
Financing Receivable Credit Quality Indicators
Total loans	43,467	36,373
Pass [Member] | Commercial Loans - Municipal loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	44,526	39,923
Pass [Member] | Commercial Loans - Health Care [Member]
Financing Receivable Credit Quality Indicators
Total loans	67,669	69,480
Pass [Member] | Commercial loans - other [Member]
Financing Receivable Credit Quality Indicators
Total loans	99,170	102,616
Pass [Member] | Commercial Leases - Investment Rated [Member]
Financing Receivable Credit Quality Indicators
Total loans	186,052	207,460
Pass [Member] | Consumer loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	1,494	1,597
Special Mention [Member]
Financing Receivable Credit Quality Indicators
Total loans	4,644	4,528
Special Mention [Member] | One-to-four family residential real estate loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Multi-family mortgage loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Wholesale commercial lending [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Nonresidential Real Estate Loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Construction loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Land loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Commercial loans - Secured [Member]
Financing Receivable Credit Quality Indicators
Total loans	4,644	4,528
Special Mention [Member] | Commercial Loans - Municipal loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Commercial Loans - Health Care [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Commercial loans - other [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Commercial Leases - Investment Rated [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Special Mention [Member] | Consumer loans [Member]
Financing Receivable Credit Quality Indicators
Total loans	0	0
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	5,750	2,098
Financing Receivables, 30 to 59 Days Past Due [Member] | One-to-four family residential real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,875	86
Financing Receivables, 30 to 59 Days Past Due [Member] | One-to-four family residential real estate loans - non-owner occupied loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	368	10
Financing Receivables, 30 to 59 Days Past Due [Member] | Multi-family mortgage loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	268	172
Financing Receivables, 30 to 59 Days Past Due [Member] | Wholesale commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Land loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial loans - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Loans - Municipal loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial loans - other [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	572	288
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Leases - Investment Rated [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 1,727	$ 934

Loans Receivable - Narrative (D

Loans Receivable - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Valuation and Qualifying Accounts Disclosure [Line Items]
Reserve For Uncollected Loan Interest	$ 76,000		$ 103,000
Financing receivable modifications	17,000
Outstanding Commitments To Borrowers Loans Classified As Troubled Debt Restructurings	0		0
Loans modified	0	$ 133,000
Allowance for Loan and Lease Losses [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation of reserves allocation	$ 0		$ 0

Other Real Estate Owned (Detail

Other Real Estate Owned (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Mortgage Loans in Process of Foreclosure, Amount	$ 1,300		$ 1,500
Other Real Estate Owned At Carrying Value	1,802	$ 5,301	2,351	$ 3,895
Real Estate Owned, Valuation Allowance, Amounts Applied	(9)	(59)
Real Estate Owned, Valuation Allowance, Valuation Increase	25	20
Real Estate Owned, Valuation Allowance	(321)	(410)	(305)	$ (449)
Other Real Estate, Disposals	(1,086)	(510)
Other Real Estate, Valuation Adjustments	(25)	(20)
Other Real Estate, Additions	562	$ 1,936
Other real estate owned at carrying value before valuation allowance	2,123		2,656
Foreclosed Residential Real Estate [Member]
Real Estate Owned, Valuation Allowance			(352)
One to Four Family Residential Real Estate Loans [Member]
Other Real Estate Owned At Carrying Value	935		827
Real Estate Owned, Valuation Allowance	0		(9)
Other real estate owned at carrying value before valuation allowance	935		836
Nonresidential Real Estate [Member]
Other Real Estate Owned At Carrying Value	863		1,520
Real Estate Owned, Valuation Allowance	(277)		(252)
Other real estate owned at carrying value before valuation allowance	1,140		1,772
Land [Member]
Other Real Estate Owned At Carrying Value	4		4
Real Estate Owned, Valuation Allowance	(44)		(44)
Other real estate owned at carrying value before valuation allowance	$ 48		$ 48

Securities Sold Under Agreement

Securities Sold Under Agreements to Repurchase (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Abstract]
Available-for-sale Securities Pledged as Collateral	$ 3,300	$ 3,700
Carrying Value of Federal Funds Purchased, Securities Sold under Agreements to Repurchase, and Deposits Received for Securities Loaned	983	768
Federal Home Loan Bank Advances [Member] | Period One [Member]
Federal Home Loan Bank, Advances [Line Items]
Debt, Long-term and Short-term, Combined Amount	$ 60,000	$ 60,000

Employee Benefit Plans - Employ

Employee Benefit Plans - Employee Stock Ownership Plan (Details) - USD ($)	Mar. 29, 2017	Jun. 30, 2005	Mar. 31, 2018	Dec. 31, 2017
Compensation Related Costs, Retirement and Share Based Payment [Line Items]
ESOP compensation expense			$ 1,100,000	$ 1,300,000
Loan receivable from ESOP		$ 19,600,000
ESOP issued price (usd per share)		$ 10
Employee Stock Ownership Plan (ESOP), Shares in ESOP [Abstract]
Allocated to participants (shares)			1,203,810	1,125,448
Distributed to participants			(317,914)	(313,223)
Unearned (shares)			0	831,852
Total ESOP shares (shares)	78,362		885,896	1,644,077
Fair value of unearned shares			$ 0	$ 12,328,000
Common Stock [Member]
Compensation Related Costs, Retirement and Share Based Payment [Line Items]
Repayments of debt, shares issued (shares)	753,490
ESOP shares purchased (shares)		1,957,300
Share Acquisition Loan [Member]
Compensation Related Costs, Retirement and Share Based Payment [Line Items]
Loans payable			$ 0	$ 10,800,000

Equity Incentive Plans - Narrat

Equity Incentive Plans - Narrative (Details) - USD ($) $ in Thousands	Jun. 27, 2006	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding		0	1,752,156	1,752,156
Share-based compensation expense		$ 0	$ 979
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			1,752,156
Share-based Compensation Arrangement by Share-based Payment Award, Net Settlement Share Issuance		280,554
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period		198,026
Share-based Compensation Arrangement by Share-based Payment Award, Shares Withheld For Taxes		82,528
2006 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (shares)	3,425,275
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years

Equity Incentive Plans - Schedu

Equity Incentive Plans - Schedule of Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock Options Outstanding	0	1,752,156	1,752,156
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 0	$ 0	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term		5 months 23 days	1 year 5 months 23 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value			$ 778
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 0	$ 4,422
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross		(1,752,156)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 0

Fair Value - Financial Assets A

Fair Value - Financial Assets Accounted for at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Company's financial instruments measured at fair values
Total Fair value	$ 102,170		$ 93,383
Real Estate Acquired Through Foreclosure Fair Value			916
Real Estate Owned, Valuation Allowance, Valuation Increase	25	$ 20
Certificates of deposit [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	86,340		75,916
Equity Funds [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	491		499
Residential Mortgage Backed Securities [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	11,544		12,472
Collateralized Debt Obligations [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	4,277		4,486
SBA-guaranteed loan participation certificates [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	9		10
Nonrecurring [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	102,661		93,383
Real Estate Acquired Through Foreclosure Fair Value			916
Nonrecurring [Member] | Certificates of deposit [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	86,340		75,916
Nonrecurring [Member] | Equity mutual fund [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	491		499
Nonrecurring [Member] | Mortgage-backed securities - residential [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	11,544		12,472
Nonrecurring [Member] | Collateralized mortgage obligations - residential [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	4,277		4,486
Nonrecurring [Member] | SBA-guaranteed loan participation certificates [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	9		10
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	491		499
Real Estate Acquired Through Foreclosure Fair Value			0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Certificates of deposit [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage-backed securities - residential [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Collateralized mortgage obligations - residential [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | SBA-guaranteed loan participation certificates [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	102,170		92,884
Real Estate Acquired Through Foreclosure Fair Value			0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member] | Equity mutual fund [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Real Estate Acquired Through Foreclosure Fair Value	409		916
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Certificates of deposit [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity mutual fund [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mortgage-backed securities - residential [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Collateralized mortgage obligations - residential [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | SBA-guaranteed loan participation certificates [Member]
Schedule of Company's financial instruments measured at fair values
Total Fair value	0		0
One to Four Family Residential Real Estate Loans [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value			102
One to Four Family Residential Real Estate Loans [Member] | Nonrecurring [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value			102
One to Four Family Residential Real Estate Loans [Member] | Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value			0
One to Four Family Residential Real Estate Loans [Member] | Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value			0
Commercial Real Estate [Member] | Nonrecurring [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value	409		814
Commercial Real Estate [Member] | Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value	0		0
Commercial Real Estate [Member] | Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value	0		0
Commercial Real Estate [Member] | Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value	$ 409
Nonresidential Real Estate Loans [Member]
Schedule of Company's financial instruments measured at fair values
Real Estate Acquired Through Foreclosure Fair Value			$ 814
Sales Comparison Valuation Technique [Member] | Commercial Real Estate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Processes, Description	Sales comparison
Fair Value Measurements, Sensitivity Analysis, Description	Comparison between sales and income approaches

Fair Value - Assets Measured at

Fair Value - Assets Measured at Fair Value on a Non-Recurring Basis (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Other Real Estate	$ 494,000		$ 1,200,000
Real Estate Owned, Valuation Allowance, Component	85,000		261,000
Fair Value, Other real estate owned			916,000
Other Real Estate Owned Write Downs	25,000	$ 20,000
One-to-four family residential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			102,000
Nonresidential Real Estate Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			814,000
Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			916,000
Nonrecurring [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			102,000
Nonrecurring [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned	409,000		814,000
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned	0		0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned			0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned	0		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned	409,000		$ 916,000
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Other real estate owned	$ 409,000
Sales Comparison Valuation Technique [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Processes, Description	Sales comparison
Fair Value Measurements, Sensitivity Analysis, Description	Comparison between sales and income approaches
Maximum [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate			20.04%
Maximum [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | Nonresidential Real Estate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments			4.58%
Maximum [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments			31.60%
Minimum [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate			8.62%
Minimum [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | Nonresidential Real Estate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments			(3.22%)
Minimum [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments			5.74%
Weighted Average [Member] | impaired loans [Member] | Sales Comparison Valuation Technique [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments	3.60%		(10.20%)
Weighted Average [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate			11.90%
Weighted Average [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | Nonresidential Real Estate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments			3.77%
Weighted Average [Member] | Real Estate [Domain] | Sales Comparison Valuation Technique [Member] | Nonresidential real estate loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments			25.20%

Fair Value - Carrying Amount an

Fair Value - Carrying Amount and Estimated Fair Value of Finanical Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 92,576	$ 127,592	$ 75,466	$ 96,684
Financial assets
Securities, carrying amount	102,170	93,383
Loans receivable, net of allowance for loan losses, carrying amounts	1,277,553	1,314,651
FHLBC stock, carrying amount	8,290	8,290
Accrued interest receivable, carrying amount	4,900	4,619
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets
Available-for-sale Securities, Fair Value Disclosure	102,661	93,383
Loans Receivable, Fair Value Disclosure	1,276,635	1,323,139
Accounts Receivable, Fair Value Disclosure	4,900	4,619
Financial liabilities
Cash and Cash Equivalents, Fair Value Disclosure	92,576	127,592
Demand Deposit Accounts Fair Value Disclosure	232,593	234,354
Deposits Savings Deposits Fair Value Disclosure	160,093	160,501
Now Money Market Accounts		589,238
Now Money Market Accounts Fair Value Disclosure	573,886
Certificates Of Deposit Fair Value Disclosure	308,904	353,969
Short Term Borrowings Fair Value Disclosure	60,832	60,627
Accrued Liabilities, Fair Value Disclosure	180	147
Estimate of Fair Value, Fair Value Disclosure [Member] | Level 1 [Member]
Financial assets
Loans Receivable, Fair Value Disclosure		0
Accounts Receivable, Fair Value Disclosure		0
Financial liabilities
Cash and Cash Equivalents, Fair Value Disclosure	10,613	13,572
Demand Deposit Accounts Fair Value Disclosure		0
Deposits Savings Deposits Fair Value Disclosure		0
Certificates Of Deposit Fair Value Disclosure		0
Short Term Borrowings Fair Value Disclosure		0
Accrued Liabilities, Fair Value Disclosure		0
Estimate of Fair Value, Fair Value Disclosure [Member] | Level 2 [Member]
Financial assets
Available-for-sale Securities, Fair Value Disclosure	102,170	92,884
Loans Receivable, Fair Value Disclosure	1,276,635	1,323,139
Accounts Receivable, Fair Value Disclosure	4,900	4,619
Financial liabilities
Cash and Cash Equivalents, Fair Value Disclosure	81,963	114,020
Demand Deposit Accounts Fair Value Disclosure	232,593	234,354
Deposits Savings Deposits Fair Value Disclosure	160,093	160,501
Now Money Market Accounts		589,238
Now Money Market Accounts Fair Value Disclosure	573,886
Certificates of Deposit, at Carrying Value	308,904
Certificates Of Deposit Fair Value Disclosure		353,969
Short-term Debt	60,832	60,627
Accrued Liabilities, Fair Value Disclosure	180	147
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Loans Receivable, Fair Value Disclosure		0
Reported Value Measurement [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Cash and Cash Equivalents, at Carrying Value	92,576	127,592
Financial assets
Securities, carrying amount	102,661	93,383
Loans receivable, net of allowance for loan losses, carrying amounts	1,277,553	1,314,651
FHLBC stock, carrying amount	8,290	8,290
Accrued interest receivable, carrying amount	4,900	4,619
Financial liabilities
Demand Deposit Accounts	232,593	234,354
Deposits, Savings Deposits	160,093	160,501
Now Money Market Accounts		589,238
Now Money Market Accounts Fair Value Disclosure	573,886
Certificates of Deposit, at Carrying Value	311,435	355,958
Short-term Debt	60,983	60,768
Accrued Interest Payable	180	147
Equity Funds [Member]
Financial assets
Securities, carrying amount	$ 491	$ 499

Revenue From Contracts With C53

Revenue From Contracts With Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue Recognition [Abstract]
Deposit service charges and fees	$ 978	$ 950
Loan fee income	70	60
Commercial mortgage brokerage fees	41	0
Residential mortgage banking fees	30	44
Trust and insurance commissions and annuities income	213	249
Earnings on bank owned life insurance	66	63
Other	141	178
Total noninterest income	1,539	1,544
Interchange income	$ 361	$ 350

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Thousands	Apr. 23, 2018	Jun. 30, 2018	Apr. 01, 2018	Mar. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Bank owned life insurance				$ 22,925	$ 22,859
Scenario, Forecast [Member] | 15W060 North Frontage Road, Burr Ridge, Illinois [Member]
Subsequent Event [Line Items]
Gain (loss) on disposition of real estate		$ 100
Subsequent Event [Member]
Subsequent Event [Line Items]
Bank owned life insurance			$ 1,400
Subsequent Event [Member] | 15W060 North Frontage Road, Burr Ridge, Illinois [Member]
Subsequent Event [Line Items]
Sales price	$ 6,000