First Midwest Bancorp (ONBPP) 10-K 1 Mar 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 26, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	FIRST MIDWEST BANCORP INC
Entity Central Index Key	702,325
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 2,568,432,801
Entity Common Stock, Shares Outstanding		106,848,075

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 211,189	$ 192,800
Interest-bearing deposits in other banks	78,069	153,770
Trading securities, at fair value	0	20,447	[1]
Equity securities, at fair value	30,806	0
Securities available-for-sale, at fair value	2,272,009
Securities available-for-sale, at fair value		1,884,209
Securities held-to-maturity, at amortized cost (fair value 2018 – $9,871; 2017 – $12,013)	10,176	13,760
Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB) stock, at cost	80,302	69,708
Loans	11,446,783	10,437,812
Allowance for loan losses	(102,219)	(95,729)
Net loans	11,344,564	10,342,083
Other real estate owned (OREO)	12,821	20,851
Premises, furniture, and equipment, net	132,502	123,316
Investment in bank-owned life insurance (BOLI)	296,733	279,900
Goodwill and other intangible assets	790,744	754,757
Accrued interest receivable and other assets	245,734	221,451
Total assets	15,505,649	14,077,052
Liabilities
Noninterest-bearing deposits	3,642,989	3,576,190
Interest-bearing deposits	8,441,123	7,477,135
Total deposits	12,084,112	11,053,325
Borrowed funds	906,079	714,884
Senior and subordinated debt	203,808	195,170
Accrued interest payable and other liabilities	256,652	248,799
Total liabilities	13,450,651	12,212,178
Stockholders' Equity
Common stock	1,157	1,123
Additional paid-in capital	1,114,580	1,031,870
Retained earnings	1,192,767	1,074,990
Accumulated other comprehensive loss, net of tax	(52,512)	(33,036)
Treasury stock, at cost	(200,994)	(210,073)
Total stockholders' equity	2,054,998	1,864,874
Total liabilities and stockholders' equity	$ 15,505,649	$ 14,077,052
[1]	As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	115,672,000	112,351,000
Common stock, shares outstanding	106,375,000	102,717,000
Treasury stock, shares	9,297,000	9,634,000
Securities held-to-maturity, at fair value	$ 9,871	$ 12,013

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest Income
Loans	$ 523,229	$ 463,331	$ 337,998
Investment securities – taxable	49,409	35,569	28,724
Investment securities – tax-exempt	5,060	6,296	8,737
Other short-term investments	4,794	4,520	2,873
Total interest income	582,492	509,716	378,332
Interest Expense
Deposits	37,774	16,184	9,863
Borrowed funds	15,388	9,100	6,313
Senior and subordinated debt	12,708	12,428	12,465
Total interest expense	65,870	37,712	28,641
Net interest income	516,622	472,004	349,691
Provision for loan losses	47,854	31,290	30,983
Net interest income after provision for loan losses	468,768	440,714	318,708
Noninterest Income
Service charges on deposit accounts	48,715	48,368	40,665
Wealth management fees	43,512	41,321	33,071
Card-based fees	17,024	28,992	29,104
Capital market products income	7,721	8,171	10,024
Mortgage banking income	7,094	8,131	10,162
Merchant servicing fees	1,465	10,340	12,533
Other service charges, commissions, and fees	9,425	9,843	9,542
Net securities gains (losses)	0
Net securities gains (losses)		(1,876)	1,420
Other income	9,636	9,859	7,282
Net gain on sale-leaseback transaction	0	0	5,509
Total noninterest income	144,592	163,149	159,312
Noninterest Expense
Salaries and wages	181,164	182,507	151,341
Retirement and other employee benefits	43,104	41,886	33,309
Net occupancy and equipment expense	53,434	49,751	41,154
Professional services	32,681	33,689	25,122
Technology and related costs	19,220	18,068	14,765
Federal Deposit Insurance Corporation (FDIC) premiums	10,584	8,987	6,268
Advertising and promotions	9,248	8,694	7,787
Amortization of Intangible Assets	7,444	7,865	4,682
Net OREO expense	1,162	4,683	3,024
Merchant card expense	0	8,377	10,782
Cardholder expense	0	7,323	5,812
Other expenses	28,236	23,956	20,152
Delivering Excellence implementation costs	20,413	0	0
Acquisition and integration related expenses	9,613	20,123	14,352
Lease cancellation fee	0	0	950
Total noninterest expense	416,303	415,909	339,500
Income before income tax expense	197,057	187,954	138,520
Income tax expense	39,187	89,567	46,171
Net income	$ 157,870	$ 98,387	$ 92,349
Per Common Share Data
Basic earnings per common share (EPS) (in dollars per share)	$ 1.52	$ 0.96	$ 1.14
Diluted earnings per common share (in dollars per share)	$ 1.52	$ 0.96	$ 1.14
Weighted-average common shares outstanding (in shares)	102,850	101,423	79,797
Weighted-average diluted common shares outstanding (in shares)	102,854	101,443	79,810

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 157,870	$ 98,387	$ 92,349
Unrealized holding (losses) gains:
Before tax	(16,294)	12,641	(19,204)
Tax effect	4,342	(5,077)	7,682
Net of tax	(11,952)	7,564	(11,522)
Reclassification of net gains (losses) included in net income:
Before tax	0	(1,876)	1,420
Tax effect	0	771	(568)
Net of tax	0	(1,105)	852
Net unrealized holding (losses) gains	(11,952)	8,669	(12,374)
Derivative Instruments
Before tax	2,786	(4,333)	2,175
Tax effect	(789)	1,746	(883)
Net of tax	1,997	(2,587)	1,292
Net unrealized holding (losses) gains
Before tax	(3,850)	2,988	(2,002)
Tax effect	1,018	(1,196)	563
Net of tax	(2,832)	1,792	(1,439)
Total other comprehensive (loss) income	(12,787)	7,874	(12,521)
Total comprehensive income	$ 145,083	$ 106,261	$ 79,828

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income - AOCI - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ 1,864,874	$ 1,257,080	$ 1,146,268
Other comprehensive (loss) income		(12,787)	7,874	(12,521)
Adjustments to apply recent accounting pronouncements	[1]		0
Ending balance		2,054,998	1,864,874	1,257,080
Accumulated Unrealized Loss on Securities Available- for-Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(13,976)	(22,645)	(10,271)
Other comprehensive (loss) income		(11,952)	8,669	(12,374)
Adjustments to apply recent accounting pronouncements	[1]	(2,864)
Ending balance		(28,792)	(13,976)	(22,645)
Accumulated Unrealized Loss on Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(3,763)	(1,176)	(2,468)
Other comprehensive (loss) income		1,997	(2,587)	1,292
Adjustments to apply recent accounting pronouncements	[1]	(784)
Ending balance		(2,550)	(3,763)	(1,176)
Unrecognized Net Pension Costs
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(15,297)	(17,089)	(15,650)
Other comprehensive (loss) income		(2,832)	1,792	(1,439)
Adjustments to apply recent accounting pronouncements	[1]	(3,041)
Ending balance		(21,170)	(15,297)	(17,089)
Total Accumulated Other Comprehensive Loss, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(33,036)	(40,910)	(28,389)
Other comprehensive (loss) income		(12,787)	7,874	(12,521)
Adjustments to apply recent accounting pronouncements	[1]	(6,689)	(6,689)
Ending balance		$ (52,512)	$ (33,036)	$ (40,910)
[1]	As a result of accounting guidance adopted in 2018, certain reclassifications were made from accumulated other comprehensive loss to retained earnings as of January 1, 2018. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders’ Equity - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2015			77,952
Beginning balance at Dec. 31, 2015		$ 1,146,268	$ 882	$ 446,672	$ 953,516	$ (28,389)	$ (226,413)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		92,349			92,349
Other comprehensive (loss) income		(12,521)				(12,521)
Common dividends declared ($0.36, $0.39 and $0.45)		(29,191)			(29,191)
Acquisition, net of issuance costs (in shares)			3,042
Acquisition, net of issuance costs		54,896	$ 31	54,865
Common stock issued (in shares)			13
Common stock issued		227		227
Restricted stock activity (in shares)			326
Restricted stock activity		(2,673)		(10,685)			8,012
Treasury stock issued to benefit plans (in shares)			(8)
Treasury stock issued to benefit plans		(154)		(21)			(133)
Share-based compensation expense		7,879		7,879
Ending balance (in shares) at Dec. 31, 2016			81,325
Ending balance at Dec. 31, 2016		1,257,080	$ 913	498,937	1,016,674	(40,910)	(218,534)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		98,387			98,387
Other comprehensive (loss) income		7,874				7,874
Common dividends declared ($0.36, $0.39 and $0.45)		(40,071)			(40,071)
Acquisition, net of issuance costs (in shares)			21,078
Acquisition, net of issuance costs		534,090	$ 210	533,322			558
Common stock issued (in shares)			9
Common stock issued		240		240
Restricted stock activity (in shares)			317
Restricted stock activity		(3,659)		(11,855)			8,196
Treasury stock issued to benefit plans (in shares)			(12)
Treasury stock issued to benefit plans		(290)		3			(293)
Share-based compensation expense		$ 11,223		11,223
Ending balance (in shares) at Dec. 31, 2017		102,717	102,717
Ending balance at Dec. 31, 2017		$ 1,864,874	$ 1,123	1,031,870	1,074,990	(33,036)	(210,073)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to apply recent accounting pronouncements	[1]	0			6,689	(6,689)
Net income		157,870			157,870
Other comprehensive (loss) income		(12,787)				(12,787)
Common dividends declared ($0.36, $0.39 and $0.45)		(46,782)			(46,782)
Acquisition, net of issuance costs (in shares)			3,311
Acquisition, net of issuance costs		83,303	$ 33	83,270
Common stock issued (in shares)			39
Common stock issued		961	$ 1	293			667
Restricted stock activity (in shares)			311
Restricted stock activity		(4,421)		(12,983)			8,562
Treasury stock issued to benefit plans (in shares)			(3)
Treasury stock issued to benefit plans		(82)		68			(150)
Share-based compensation expense		$ 12,062		12,062
Ending balance (in shares) at Dec. 31, 2018		106,375	106,375
Ending balance at Dec. 31, 2018		$ 2,054,998	$ 1,157	$ 1,114,580	$ 1,192,767	(52,512)	$ (200,994)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to apply recent accounting pronouncements	[1]					$ (6,689)
[1]	As a result of accounting guidance adopted in 2018, certain reclassifications were made from accumulated other comprehensive loss to retained earnings as of January 1, 2018. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders’ Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock
Common dividends declared per common share (in dollars per share)	$ 0.45	$ 0.39	$ 0.36

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities
Net income		$ 157,870	$ 98,387	$ 92,349
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses		47,854	31,290	30,983
Depreciation of premises, furniture, and equipment		15,865	13,995	12,804
Net amortization of premium on securities		15,348	16,142	13,653
Net securities losses (gains)		0
Net securities losses (gains)			1,876	(1,420)
Gains on sales of 1-4 family mortgages and corporate loans held-for-sale		(5,562)	(7,078)	(8,931)
Net (gains) losses on sales and valuation adjustments of OREO		(347)	585	1,196
Amortization of the FDIC indemnification asset		1,208	1,208	1,185
Net losses (gains)		5,227	(125)	(4,762)
BOLI income		(5,835)	(5,946)	(3,647)
Net pension cost (income)		1,447	981	(513)
Share-based compensation expense	[1]	12,062	11,223	7,879
Tax benefit (expense) related to share-based compensation		258	349	(197)
Provision for deferred income tax expense (benefit)		26,309	(4,077)	(1,367)
Amortization of other intangible assets		7,444	7,865	4,682
Originations of mortgage loans held-for-sale		(224,303)	(254,030)	(238,192)
Proceeds from sales of mortgage loans held-for-sale		245,967	258,626	246,642
Net decrease in equity securities		964	0	0
Net increase in trading securities		0	(2,527)	(1,026)
Net (increase) decrease in accrued interest receivable and other assets		(44,246)	121,577	(76,902)
Net (decrease) increase in accrued interest payables and other liabilities		(4,346)	(56,055)	47,315
Net cash provided by operating activities		253,184	234,266	121,731
Investing Activities
Proceeds from maturities, repayments, and calls of securities available-for-sale		331,026	349,444	360,303
Proceeds from sales of securities available-for-sale		24,974	629,843	53,186
Purchases of securities available-for-sale		(735,701)	(733,440)	(933,317)
Proceeds from maturities, repayments, and calls of securities held-to-maturity		3,584	8,546	8,077
Purchases of securities held-to-maturity		0	(15)	(5,352)
Net purchases of FHLB stock		(10,040)	(7,330)	(18,276)
Net increase in loans		(770,039)	(457,501)	(714,213)
Proceeds from claims on BOLI, net of premiums paid		(49)	1,722	1,588
Proceeds from sales of OREO		16,953	19,326	7,539
Proceeds from sales of premises, furniture, and equipment		4,561	18,031	152,863
Purchases of premises, furniture, and equipment		(27,800)	(16,123)	(19,083)
Net cash received from acquisitions		160,145	41,717	57,347
Net cash used in investing activities		(1,002,386)	(145,780)	(1,049,338)
Financing Activities
Net increase in deposit accounts		567,627	200,848	135,944
Net increase (decrease) in borrowed funds		172,977	(164,124)	711,496
Net proceeds from the issuance of subordinated debt		0	0	146,484
Payments for the retirement of senior and subordinated debt		0	0	(153,500)
Cash dividends paid		(44,293)	(37,129)	(29,198)
Restricted stock activity		(4,421)	(3,659)	(2,673)
Net cash provided by (used in) financing activities		691,890	(4,064)	808,553
Net (decrease) increase in cash and cash equivalents		(57,312)	84,422	(119,054)
Cash and cash equivalents at beginning of year		346,570	262,148	381,202
Cash and cash equivalents at end of year		289,258	346,570	262,148
Supplemental Disclosures of Cash Flow Information:
Income taxes (refunded) paid		(1,108)	15,191	57,553
Interest paid to depositors and creditors		60,569	36,424	27,400
Dividends declared, but unpaid			10,185	7,243
Common stock issued for acquisitions, net of issuance costs		83,303	534,090	54,896
Non-cash transfers of loans to OREO		6,027	6,255	4,173
Non-cash transfers of loans held-for-investment to loans held-for-sale		15,060	48,999	93,981
Non-cash transfer of trading securities and securities available-for-sale to equity securities		$ 27,855	$ 0	$ 0
[1]	Comprised of restricted stock, restricted stock unit, and performance share awards expense.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations – First Midwest Bancorp, Inc. (the "Company") is a bank holding company that was incorporated in Delaware in 1982 and began operations on March 31, 1983. The Company is headquartered in Chicago, Illinois with operations throughout metropolitan Chicago, northwest Indiana, central and western Illinois, and eastern Iowa. The Company operates three wholly-owned subsidiaries: First Midwest Bank (the "Bank"), Catalyst Asset Holdings, LLC ("Catalyst"), and Premier Asset Management LLC ("Premier"). The Bank conducts the majority of the Company's operations, Catalyst manages certain non-performing assets of the Company, and Premier is a registered investment advisor providing advisory services to certain of the Company's wealth management clients. The Company is engaged in commercial and retail banking and offers a full range of commercial, retail, treasury management, and wealth management products and services to commercial and industrial, agricultural, commercial real estate, municipal, and consumer customers. Basis of Presentation – The accounting and reporting policies of the Company and its subsidiaries conform to U.S. generally accepted accounting principles ("GAAP") and general practices within the banking industry. The Company uses the accrual basis of accounting for financial reporting purposes. Certain reclassifications were made to prior year amounts to conform to the current year presentation. Use of Estimates – The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Although these estimates and assumptions are based on the best available information, actual results could differ from those estimates. Principles of Consolidation – The accompanying consolidated financial statements include the financial position and results of operations of the Company and its subsidiaries after elimination of all significant intercompany accounts and transactions. Assets held in a fiduciary or agency capacity are not assets of the Company or its subsidiaries and are not included in the consolidated financial statements. Segment Disclosures – The Company has one reportable segment. The Company's chief operating decision maker evaluates the operations of the Company using consolidated information for purposes of allocating resources and assessing performance. Therefore, segment disclosures are not required. The following is a summary of the Company's significant accounting policies. Business Combinations – Business combinations are accounted for under the acquisition method of accounting. Assets acquired and liabilities assumed are recorded at their estimated fair values as of the date of acquisition, with any excess of the purchase price of the acquisition over the fair value of the identifiable net tangible and intangible assets acquired recorded as goodwill. Alternatively, a gain is recorded if the fair value of assets purchased exceeds the fair value of liabilities assumed and consideration paid. The results of operations of the acquired business are included in the Consolidated Statements of Income from the effective date of the acquisition. Cash and Cash Equivalents – For purposes of the Consolidated Statements of Cash Flows, management defines cash and cash equivalents to include cash and due from banks, interest-bearing deposits in other banks, and other short-term investments, if any, such as federal funds sold and securities purchased under agreements to resell. Securities – Securities are classified as held-to-maturity, equity, or available-for-sale at the time of purchase. Securities Held-to-Maturity – Securities classified as held-to-maturity are securities for which management has the intent and ability to hold to maturity. These securities are stated at cost and adjusted for amortization of premiums and accretion of discounts over the estimated lives of the securities using the effective interest method. Equity Securities – The Company's equity securities consist primarily of community development investments and certain diversified investment securities held in a grantor trust for participants in the Company's nonqualified deferred compensation plan that are invested in money market and mutual funds. These securities are carried at fair value with changes in fair value recognized in net income. Securities Available-for-Sale – All other securities are classified as available-for-sale. Securities available-for-sale are carried at fair value with unrealized gains and losses, net of related deferred income taxes, recorded in stockholders' equity as a separate component of accumulated other comprehensive loss. The historical cost of debt securities is adjusted for amortization of premiums and accretion of discounts over the estimated life of the security using the effective interest method. Amortization of premiums and accretion of discounts are included in interest income. Purchases and sales of securities are recognized on a trade date basis. Realized securities gains or losses are reported in net securities gains (losses) in the Consolidated Statements of Income. The cost of securities sold is based on the specific identification method. On a quarterly basis, the Company individually assesses securities with unrealized losses to determine whether there were any events or circumstances indicating that an other-than-temporary impairment ("OTTI") has occurred. In evaluating OTTI, the Company considers many factors, including (i) the severity and duration of the impairment, (ii) the financial condition and near-term prospects of the issuer, including external credit ratings and recent downgrades for debt securities, (iii) its intent to hold the security until its value recovers, and (iv) the likelihood that it will be required to sell the security before a recovery in value, which may be at maturity. If management intends to sell the security or believes it is more likely than not that it will be required to sell the security prior to full recovery, an OTTI charge will be recognized through income as a realized loss and included in net securities gains (losses) in the Consolidated Statements of Income. If management does not expect to sell the security or believes it is not more likely than not that it will be required to sell the security prior to full recovery, the OTTI is separated into the amount related to credit deterioration, which is recognized through income as a realized loss, and the amount resulting from other factors, which is recognized in other comprehensive loss. FHLB and FRB Stock – The Company, as a member of the FHLB and FRB, is required to maintain an investment in the capital stock of the FHLB and FRB. No ready market exists for these stocks, and they have no quoted market values. The stock is redeemable at par by the FHLB and FRB and is, therefore, carried at cost and periodically evaluated for impairment. Loans – Loans held-for-investment are loans that the Company intends to hold until they are paid in full and are carried at the principal amount outstanding, including certain net deferred loan origination fees. Loan origination fees, commitment fees, and certain direct loan origination costs are deferred, and the net amount is amortized as a yield adjustment over the contractual life of the related loans or commitments and included in interest income. Fees related to letters of credit are amortized into fee income over the contractual life of the commitment. Other credit-related fees are recognized as fee income when earned. The Company's net investment in direct financing leases is included in loans and consists of future minimum lease payments and estimated residual values, net of unearned income. Interest income on loans is accrued based on principal amounts outstanding. Loans held-for-sale are carried at the lower of aggregate cost or fair value and included in other assets in the Consolidated Statements of Financial Condition. Acquired and Covered Loans – Covered loans consist of loans acquired by the Company in Federal Deposit Insurance Corporation ("FDIC")-assisted transactions, which are covered by loss share agreements with the FDIC (the "FDIC Agreements"), under which the FDIC reimburses the Company for the majority of the losses and eligible expenses related to these assets during the coverage period. Acquired loans consist of all other loans that were acquired in business combinations that are not covered by the FDIC Agreements. Certain loans that were previously classified as covered loans are no longer covered under the FDIC Agreements, and are included in acquired loans. Covered loans and acquired loans are included within loans held-for-investment. Acquired and covered loans are separated into (i) non-purchased credit impaired ("non-PCI") and (ii) purchased credit impaired ("PCI") loans. Non-PCI loans include loans that did not have evidence of credit deterioration since origination at the acquisition date. PCI loans include loans that had evidence of credit deterioration since origination and for which it was probable at acquisition that the Company would not collect all contractually required principal and interest payments. Evidence of credit deterioration was evaluated using various indicators, such as past due and non-accrual status. Leases and revolving loans do not qualify to be accounted for as PCI loans and are accounted for as non-PCI loans. The acquisition adjustment related to non-PCI loans is amortized into interest income over the contractual life of the related loans. If an acquired non-PCI loan is renewed subsequent to the acquisition date, any remaining acquisition adjustment is accreted into interest income and the loan is considered a new loan that is no longer classified as an acquired loan. PCI loans are accounted for based on estimates of expected future cash flows. To estimate the fair value, the Company generally aggregates purchased consumer loans and commercial loans into pools of loans with common risk characteristics, such as delinquency status, credit score, and internal risk ratings. The fair values of larger balance commercial loans are estimated on an individual basis. Expected future cash flows in excess of the fair value of loans at the purchase date ("accretable yield") are recorded as interest income over the life of the loans if the timing and amount of the expected future cash flows can be reasonably estimated. The non-accretable yield represents the difference between contractually required payments and the expected future cash flows determined at acquisition. Subsequent increases in expected future cash flows are offset against the allowance for credit losses to the extent an allowance has been established or otherwise recognized as interest income prospectively. The present value of any decreases in expected future cash flows is recognized by recording a charge-off through the allowance for loan losses or providing an allowance for loan losses. 90-Days Past Due Loans – The Company's accrual of interest on loans is generally discontinued at the time the loan is 90 days past due unless the credit is sufficiently collateralized and in the process of renewal or collection. Non-accrual Loans – Generally, corporate loans are placed on non-accrual status (i) when either principal or interest payments become 90 days or more past due unless the credit is sufficiently collateralized and in the process of renewal or collection, or (ii) when an individual analysis of a borrower's creditworthiness warrants a downgrade to non-accrual regardless of past due status. When a loan is placed on non-accrual status, unpaid interest credited to income in the current year is reversed, and unpaid interest accrued in prior years is charged against the allowance for loan losses. After the loan is placed on non-accrual status, all debt service payments are applied to the principal on the loan. Future interest income may only be recorded on a cash basis after recovery of principal is reasonably assured. Non-accrual loans are returned to accrual status when the financial position of the borrower and other relevant factors indicate that the Company will collect all principal and interest. Commercial loans and loans secured by real estate are charged-off when deemed uncollectible. A loss is recorded if the net realizable value of the underlying collateral is less than the outstanding principal and interest. Consumer loans that are not secured by real estate are subject to mandatory charge-off at a specified delinquency date and are usually not classified as non-accrual prior to being charged-off. Closed-end consumer loans, which include installment, consumer secured, and single payment loans, are usually charged-off no later than the end of the month in which the loan becomes 120 days past due. PCI loans are generally considered accruing loans unless reasonable estimates of the timing and amount of expected future cash flows cannot be determined. Loans without reasonable future cash flow estimates are classified as non-accrual loans, and interest income is not recognized on those loans until the timing and amount of the expected future cash flows can be reasonably determined. Troubled Debt Restructurings ("TDRs") – A restructuring is considered a TDR when (i) the borrower is experiencing financial difficulties, and (ii) the creditor grants a concession, such as forgiveness of principal, reduction of the interest rate, changes in payments, or extension of the maturity date. Loans are not classified as TDRs when the modification is short-term or results in an insignificant delay in payments. The Company's TDRs are determined on a case-by-case basis. The Company does not accrue interest on a TDR unless it believes collection of all principal and interest under the modified terms is reasonably assured. For a TDR to begin accruing interest, the borrower must demonstrate some level of past performance and the future capacity to perform under the modified terms. Generally, six months of consecutive payment performance under the restructured terms is required before a TDR is returned to accrual status. However, the period could vary depending on the individual facts and circumstances of the loan. An evaluation of the borrower's current creditworthiness is used to assess the borrower's capacity to repay the loan under the modified terms. This evaluation includes an estimate of expected future cash flows, evidence of strong financial position, and estimates of the value of collateral, if applicable. For TDRs to be removed from TDR status in the calendar year after the restructuring, the loans must (i) have an interest rate and terms that reflect market conditions at the time of restructuring, and (ii) be in compliance with the modified terms. If the loan was restructured at below market rates and terms, it continues to be separately reported as a TDR until it is paid in full or charged-off. Impaired Loans – Impaired loans consist of corporate non-accrual loans and TDRs. A loan is considered impaired when it is probable that the Company will not collect all contractual principal and interest. With the exception of accruing TDRs, impaired loans are classified as non-accrual and are exclusive of smaller homogeneous loans, such as home equity, 1-4 family mortgages, and installment loans. Impaired loans with balances under a specified threshold are not individually evaluated for impairment. For all other impaired loans, impairment is measured by comparing the estimated value of the loan to the recorded book value. The value of collateral-dependent loans is based on the fair value of the underlying collateral, less costs to sell. The value of other loans is measured using the present value of expected future cash flows discounted at the loan's initial effective interest rate. Allowance for Credit Losses – The allowance for credit losses is comprised of the allowance for loan losses and the reserve for unfunded commitments, and is maintained by management at a level believed adequate to absorb estimated losses inherent in the existing loan portfolio. Determination of the allowance for credit losses is subjective since it requires significant estimates and management judgment, including the amounts and timing of expected future cash flows on impaired loans, estimated losses on pools of homogeneous loans, consideration of current economic trends, and other factors. Loans deemed to be uncollectible are charged-off against the allowance for loan losses, while recoveries of amounts previously charged-off are credited to the allowance for loan losses. Additions to the allowance for loan losses are charged to expense through the provision for loan losses. The amount of provision depends on a number of factors, including net charge-off levels, loan growth, changes in the composition of the loan portfolio, and the Company's assessment of the allowance for loan losses based on the methodology discussed below. Allowance for Loan Losses – The allowance for loan losses consists of (i) specific reserves for individual loans where the recorded investment exceeds the value, (ii) an allowance based on a loss migration analysis that uses historical credit loss experience for each loan category, and (iii) an allowance based on other internal and external qualitative factors. The specific reserves component of the allowance for loan losses is based on a periodic analysis of impaired loans exceeding a fixed dollar amount. If the value of an impaired loan is less than the recorded book value, the Company either establishes a valuation allowance (i.e., a specific reserve) equal to the excess of the book value over the collateral value of the loan as a component of the allowance for loan losses or charges off the amount if it is a confirmed loss. The general reserve component is based on a loss migration analysis, which examines actual loss experience by loan category for a rolling 8-quarter period and the related internal risk rating for corporate loans. The loss migration analysis is updated quarterly primarily using actual loss experience. This component is then adjusted based on management's consideration of many internal and external qualitative factors, including: • Changes in the composition of the loan portfolio, trends in the volume of loans, and trends in delinquent and non-accrual loans that could indicate that historical trends do not reflect current conditions. • Changes in credit policies and procedures, such as underwriting standards and collection, charge-off, and recovery practices. • Changes in the experience, ability, and depth of credit management and other relevant staff. • Changes in the quality of the Company's loan review system and Board of Directors oversight. • The effect of any concentration of credit and changes in the level of concentrations, such as loan type or risk rating. • Changes in the value of the underlying collateral for collateral-dependent loans. • Changes in the national and local economy that affect the collectability of various segments of the portfolio. • The effect of other external factors, such as competition and legal and regulatory requirements, on the Company's loan portfolio. The allowance for loan losses also consists of an allowance on acquired and covered non-PCI and PCI loans. No allowance for loan losses is recorded on acquired loans at the acquisition date. Subsequent to the acquisition date, an allowance for credit losses is established as necessary to reflect credit deterioration. The acquired non-PCI allowance is based on management's evaluation of the acquired non-PCI loan portfolio giving consideration to the current portfolio balance including the remaining acquisition adjustments, maturity dates, and overall credit quality. The allowance for covered non-PCI loans is calculated in the same manner as the general reserve component based on a loss migration analysis as discussed above. The acquired and covered PCI allowance reflects the difference between the carrying value and the discounted expected future cash flows of the acquired and covered PCI loans. On a periodic basis, the adequacy of this allowance is determined through a re-estimation of expected future cash flows on all of the outstanding acquired and covered PCI loans using either a probability of default/loss given default ("PD/LGD") methodology or a specific review methodology. The PD/LGD model is a loss model that estimates expected future cash flows using a probability of default curve and loss given default estimates. Acquired non-PCI loans that have renewed subsequent to the respective acquisition dates are no longer classified as acquired loans. Instead, they are included in the general loan population and allocated an allowance based on a loss migration analysis. Reserve for Unfunded Commitments – The Company also maintains a reserve for unfunded commitments, including letters of credit, for the risk of loss inherent in these arrangements. The reserve for unfunded commitments is estimated using the loss migration analysis from the allowance for loan losses, adjusted for probabilities of future funding requirements. The reserve for unfunded commitments is included in other liabilities in the Consolidated Statements of Financial Condition. The establishment of the allowance for credit losses involves a high degree of judgment given the difficulty of assessing the factors impacting loan repayment and estimating the timing and amount of losses. While management utilizes its best judgment and information available, the adequacy of the allowance for credit losses depends on a variety of factors beyond the Company's control, including the performance of its loan portfolio, the economy, changes in interest rates and property values, and the interpretation of loan risk classifications by regulatory authorities. OREO – OREO consists of properties acquired through foreclosure in partial or total satisfaction of defaulted loans. At initial transfer into OREO, properties are recorded at fair value, less estimated selling costs. Subsequently, OREO is carried at the lower of the cost basis or fair value, less estimated selling costs. OREO write-downs occurring at the transfer date are charged against the allowance for loan losses, establishing a new cost basis. Subsequent to the initial transfer, the carrying values of OREO may be adjusted through a valuation allowance to reflect reductions in value resulting from new appraisals, new list prices, changes in market conditions, or changes in disposition strategies. Increases in value can be recognized through a reduction in the valuation allowance, but may not exceed the established cost basis. These valuation adjustments, along with expenses related to maintenance of the properties, are included in net OREO expense in the Consolidated Statements of Income. FDIC Indemnification Asset – The majority of loans and OREO acquired through FDIC-assisted transactions are covered by the FDIC Agreements, under which the FDIC reimburses the Company for the majority of the losses and eligible expenses related to these assets during the coverage period. The FDIC indemnification asset represents the present value of expected future reimbursements from the FDIC. Since the indemnified items are covered loans and covered OREO, which are initially measured at fair value, the FDIC indemnification asset is also initially measured at fair value by discounting the expected future cash flows to be received from the FDIC. These expected future cash flows are estimated by multiplying estimated losses on covered PCI loans and covered OREO by the reimbursement rates in the FDIC Agreements. The balance of the FDIC indemnification asset is adjusted periodically to reflect changes in expected future cash flows. Decreases in estimated reimbursements from the FDIC are recorded prospectively through amortization and increases in estimated reimbursements from the FDIC are recognized by an increase in the carrying value of the indemnification asset. Payments from the FDIC for reimbursement of losses result in a reduction of the FDIC indemnification asset. Depreciable Assets – Premises, furniture, and equipment are stated at cost, less accumulated depreciation. Depreciation expense is determined by the straight-line method over the estimated useful lives of the assets. Useful lives range from 3 to 10 years for furniture and equipment and 25 to 40 years for premises. Leasehold improvements are amortized over the shorter of the life of the asset or the lease term. Gains on dispositions are included in other noninterest income and losses on dispositions are included in other noninterest expense in the Consolidated Statements of Income. Maintenance and repairs are charged to operating expenses as incurred, while improvements that extend the useful life of assets are capitalized and depreciated over the estimated remaining life. Certain assets, such as buildings and land, that the Company intends to sell and meet held-for-sale criteria are transferred into the held-for-sale category at the lower of their fair value, as determined by a current appraisal, or their recorded investment. Long-lived depreciable assets are evaluated periodically for impairment when events or changes in circumstances indicate the carrying amount may not be recoverable. Impairment exists when the undiscounted expected future cash flows of a long-lived asset are less than its carrying value. In that event, the Company recognizes a loss for the difference between the carrying amount and the estimated fair value of the asset based on a quoted market price, if applicable, or a discounted cash flow analysis. Impairment losses are recorded in other noninterest expense in the Consolidated Statements of Income. BOLI – BOLI represents life insurance policies on the lives of certain Company directors and officers for which the Company is the sole owner and beneficiary. These policies are recorded as an asset in the Consolidated Statements of Financial Condition at their cash surrender value ("CSV") or the current amount that could be realized if settled. The change in CSV and insurance proceeds received are included as a component of noninterest income in the Consolidated Statements of Income. Goodwill and Other Intangible Assets – Goodwill represents the excess of the purchase price of the acquisition over the fair value of the net tangible and intangible assets acquired using the acquisition method of accounting. Goodwill is not amortized. Instead, impairment testing is conducted annually as of October 1 or more often if events or circumstances between annual tests indicate that there may be impairment. Impairment testing is performed using either a qualitative or quantitative approach at the reporting unit level. All of the Company's goodwill is allocated to First Midwest Bancorp, Inc., which is the Company's only applicable reporting unit for purposes of testing goodwill for impairment. Impairment testing performed using a qualitative approach assesses recent events and circumstances to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount. Qualitative factors include, but are not limited to, macroeconomic conditions, industry and market specific conditions and trends, the Company's financial performance, market capitalization, stock price, and Company-specific events relevant to the assessment. If the assessment of qualitative factors indicates that it is not more-likely-than-not that an impairment exists, no further testing is performed; otherwise, the Company would proceed with a quantitative two-step goodwill impairment test. In the first step, the Company compares its estimate of the fair value of the reporting unit, which is based on a discounted cash flow analysis, with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill of the reporting unit is not impaired and the second step is not required. If necessary, the second step compares the implied fair value of the reporting unit goodwill with the carrying amount of that goodwill. The implied fair value of goodwill is determined by assigning the value of the reporting unit to all of the assets and liabilities of that unit, including any other identifiable intangible assets. An impairment loss is recognized if the carrying amount of the reporting unit goodwill exceeds the implied fair value of goodwill. Other intangible assets represent purchased assets that lack physical substance, but can be distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged either on its own or in combination with a related contract, asset, or liability. Identified intangible assets that have a finite useful life are amortized over that life in a manner that reflects the estimated decline in the economic value of the identified intangible asset. All of the Company's other intangible assets have finite lives and are amortized over varying periods not exceeding 13 years. Intangible assets are reviewed for impairment annually or more frequently when events or circumstances indicate that its carrying amount may not be recoverable. Wealth Management – Assets held in a fiduciary or agency capacity for customers are not included in the consolidated financial statements as they are not assets of the Company or its subsidiaries. Fee income is recognized on an accrual basis and is included as a component of noninterest income in the Consolidated Statements of Income. Derivative Financial Instruments – To provide derivative products to customers and in the ordinary course of business, the Company enters into derivative transactions as part of its overall interest rate risk management strategy to minimize significant unplanned fluctuations in earnings and expected future cash flows caused by interest rate volatility. All derivative instruments are recorded at fair value as either other assets or other liabilities in the Consolidated Statements of Financial Condition. Subsequent changes in a derivative's fair value are recognized in earnings unless specific hedge accounting criteria are met. On the date the Company enters into a derivative contract, the derivative is designated as a fair value hedge, a cash flow hedge, or a non-hedge derivative instrument. Fair value hedges are designed to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk. Cash flow hedges are designed to mitigate exposure to variability in expected future cash flows to be received or paid related to an asset, liability, or other type of forecasted transaction. The Company formally documents all relationships between hedging instruments and hedged items, including its risk management objective and strategy at inception. At the hedge's inception and quarterly thereafter, a formal assessment is performed to determine the effectiveness of the derivative in offsetting changes in the fair values or expected future cash flows of the hedged items in the current period and prospectively. If a derivative instrument designated as a hedge is terminated or ceases to be highly effective, hedge accounting is discontinued prospectively, and the gain or loss is amortized into earnings. For fair value hedges, the gain or loss is amortized over the remaining life of the hedged asset or liability. For cash flow hedges, the gain or loss is amortized over the same period that the forecasted hedged transactions impact earnings. If the hedged item is disposed of, any fair value adjustments are included in the gain or loss from the disposition of the hedged item. If the forecasted transaction is no longer probable, the gain or loss is included in earnings immediately. For fair value hedges, changes in the fair value of the derivative instruments, as well as changes in the fair value of the hedged item, are recognized in earnings. For cash flow hedges, the effective portion of the change in fair value of the derivative instrument is reported as a component of accumulated other comprehensive loss and is reclassified to earnings when the hedged transaction is reflected in earnings. Ineffectiveness is calculated based on the change in fair value of the hedged item compared with the change in fair value of the hedging instrument. For all types of hedges, any

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	RECENT ACCOUNTING PRONOUNCEMENTS Adopted Accounting Pronouncements Revenue from Contracts with Customers: In May of 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09 that requires an entity to 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. In March of 2016, the FASB issued an amendment to this guidance to clarify the implementation of guidance on principal versus agent consideration. Additional amendments to clarify the implementation guidance on the identification of performance obligations and licensing were issued in April of 2016 and narrow-scope improvements and practical expedients were issued in May of 2016. The guidance is effective for annual and interim reporting periods beginning on or after December 15, 2017, and must be applied either retrospectively or using the modified retrospective approach. The Company's revenue is comprised of net interest income on financial assets and liabilities, which is excluded from the scope of this guidance, and noninterest income. The primary sources of revenue within noninterest income are service charges on deposit accounts, wealth management fees, card-based fees, and merchant servicing fees. The adoption of this guidance on January 1, 2018, using the modified retrospective approach, affected how the Company presents merchant servicing fees, merchant card expenses, card-based fees, and cardholder expenses, which are presented on a gross basis within noninterest income and noninterest expense for the prior period and are presented on a net basis within noninterest income for the current period. Total expenses of $16.1 million for the year ended December 31, 2018 were netted in noninterest income. The adoption of this guidance did not impact net income; therefore, a cumulative effect adjustment to opening retained earnings was not deemed necessary. Consistent with the modified retrospective approach, the Company did not adjust prior period amounts for the reclassification of merchant card expenses and cardholder expenses. A description of the Company's revenue streams accounted for under the scope of this guidance follows: Service charges on deposit accounts – Service charges on deposit accounts consist of account analysis fees (net fees earned on analyzed business and public checking accounts), monthly service fees, and other deposit account related fees. The Company's performance obligation for account analysis fees and monthly service fees is generally satisfied, and the related revenue recognized, over the period in which the service is provided. Other deposit account related fees are largely transactional based and, therefore, the Company's performance obligation is satisfied, and related revenue recognized, at a point in time. Payment for service charges on deposit accounts is primarily received as a direct charge to customers' accounts. As a result of the adoption of this guidance, there was no impact to the method of recognizing revenue related to service charges on deposit accounts for the year ended December 31, 2018. Wealth management fees – Wealth management fees represents quarterly fees due from wealth management customers as consideration for managing the customers' assets. Wealth management services include custody of assets, investment management, escrow services, fees for trust services and similar fiduciary activities. Revenue is recognized when our performance obligation is completed each quarter, which is generally the time that payment is received. Also included are fees received from a third-party broker-dealer as part of a revenue-sharing agreement. These fees are paid to us by the third-party on a quarterly basis and recognized ratably throughout the quarter as our performance obligation is satisfied. As a result of the adoption of this guidance, there was no impact to the method of recognizing revenue related to wealth management fees for the year ended December 31, 2018. Card-based fees, net – Card-based fees, net consists of debit and credit card interchange fees for processing transactions, as well as various fees for automated teller machine ("ATM") and point-of-sale transactions processed through the related networks. Interchange, ATM, and point-of-sale fees from cardholder transactions represent a percentage of the underlying transaction value or a flat fee and are recognized daily in connection with the transaction processing services provided to the cardholder. Card-based fees are presented net of certain contract costs associated with the debit, credit and ATM card interchange networks. As a result of the adoption of this guidance, $7.5 million of cardholder expenses are netted against card-based fees for the year ended December 31, 2018. Merchant servicing fees, net – Merchant servicing fees, net is included in other service charges, commissions, and fees in the Consolidated Statements of Income. The Company acts in an agency capacity with respect to its merchants to process their debit and credit card transactions, deriving revenue from assisting another entity in transactions with the Company's customers. Merchant servicing fees represent a percentage of the underlying net transaction volume or a flat fee and are recognized monthly. Merchant servicing fees are presented net of certain contract costs associated with the third-party merchant processor. As a result of the adoption of this guidance, $8.6 million of merchant card expenses are netted against merchant servicing fees for the year ended December 31, 2018. Amendments to Guidance on Classifying and Measuring Financial Instruments: In January of 2016, the FASB issued ASU 2016-01 that will require entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value. Any subsequent changes in fair value will be recognized in net income unless the investments qualify for a new practicability exception. Equity securities totaling $30.8 million are no longer classified as trading securities or securities available-for-sale. This guidance also requires entities to adjust the fair value disclosures for financial instruments carried at amortized cost from an entry price to an exit price. No changes were made to the guidance for classifying and measuring investments in debt securities and loans. Except as discussed above, the adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Classification of Certain Cash Receipts and Cash Payments: In August of 2016, the FASB issued ASU 2016-15 clarifying certain cash flow presentation and classification issues to reduce diversity in practice. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Income Taxes: In October of 2016, the FASB issued ASU 2016-16 that requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Clarifying the Definition of a Business: In January of 2017, the FASB issued ASU 2017-01 that clarifies the definition of a business to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The adoption of this guidance on January 1, 2018 did not impact the Company's financial condition, results of operations, or liquidity. Presentation of Defined Benefit Retirement Plan Costs: In March of 2017, the FASB issued ASU 2017-07 that changes how employers that sponsor defined pension and or other postretirement benefit plans present the net periodic benefit cost in the income statement. Employers are required to present the service cost component of the net periodic benefit cost in the same income statement line item as other employee compensation costs arising from services rendered during the period. Other components of net periodic benefit cost are required to be presented separately from the line item(s) that includes the service cost. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Share-based Payment Award Modifications: In May of 2017, the FASB issued ASU 2017-09 to reduce diversity in practice by clarifying when changes to the terms or conditions of a share-based payment award must be accounted for as a modification. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Derivatives and Hedging: In August of 2017, the FASB issued ASU 2017-12 to better align the financial reporting related to hedging activities with the economic objectives of those activities and to simplify the application of current hedge accounting guidance. Entities are required to apply the guidance using a modified retrospective method as of the period of adoption. This guidance is effective for annual and interim periods beginning after December 31, 2018. Early adoption is permitted, and the Company elected to do so on January 1, 2018, which did not materially impact the Company's financial condition, results of operations, or liquidity. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income: In February of 2018, the FASB issued ASU 2018-02 that requires a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017 . Entities electing the reclassification are required to apply the guidance either at the beginning of the period of adoption or retrospectively for all periods impacted. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted and the Company elected to do so on January 1, 2018, which resulted in the reclassification of $6.8 million of stranded tax effects from accumulated other comprehensive loss to retained earnings as of the beginning of the period of adoption. Accounting Pronouncements Pending Adoption Leases: In February of 2016, the FASB issued ASU 2016-02 to increase transparency and comparability across entities for leasing arrangements. This guidance requires lessees to recognize assets and liabilities for most leases. For lessors, this guidance modifies the lease classification criteria and the accounting for sales-type and direct financing leases. In addition, this guidance clarifies criteria for the determination of whether a contract is or contains a lease. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. The Company will adopt this guidance on January 1, 2019, which will result in the recognition of right-of-use assets and an increase in the associated lease liabilities for its operating leases of approximately $145 million . The amount of right-of-use assets and associated lease liabilities recorded upon adoption will be based on the present value of future minimum lease payments, the amount of which will depend on the population of leases in effect at the date of adoption. In addition, First Midwest Bank (the "Bank") entered into a sale-leaseback transaction in 2016 that resulted in a deferred gain. Upon adoption of this guidance, the remaining deferred gain of $47.3 million after tax will be recognized immediately as a cumulative-effect adjustment to equity. As a result, the deferred gain will no longer be accreted as a reduction to lease expense in net occupancy and equipment expense in the amount of approximately $6.0 million annually. See Note 8 "Premises, Furniture, and Equipment" for additional discussion of the sale-leaseback transaction. Management expects the adoption of the guidance will materially increase assets, liabilities, and equity, but does not expect it will materially impact the Company's results of operations or liquidity. Measurement of Credit Losses on Financial Instruments: In June of 2016, the FASB issued ASU 2016-13 that will require entities to present financial assets measured at amortized cost at the net amount expected to be collected, considering an entity's current estimate of all expected credit losses. In addition, credit losses relating to available-for-sale debt securities will be required to be recorded through an allowance for credit losses, with changes in credit loss estimates recognized through current earnings. This guidance is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted, but not for periods beginning before December 15, 2018. Management is evaluating the guidance and the impact to the Company's financial condition, results of operations, or liquidity. Accounting for Goodwill Impairment: In January of 2017, the FASB issued ASU 2017-04 that simplifies the accounting for goodwill impairment for all entities. The new guidance eliminates the requirement to calculate the implied fair value of goodwill using the second step of the quantitative two-step goodwill impairment model prescribed under current accounting guidance. Under the new guidance, if a reporting unit's carrying amount exceeds its fair value, an entity will record an impairment charge based on that difference. This guidance is effective for annual and interim goodwill impairment testing dates beginning after December 15, 2019. Early adoption is permitted for annual and interim goodwill impairment testing dates after January 1, 2017. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Premium Amortization on Purchased Callable Debt Securities: In March of 2017, the FASB issued ASU 2017-08 that shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Improvements to Nonemployee Share-based Payment Accounting: In June of 2018, the FASB issued ASU 2018-07 that aligns the measurement and classification guidance for share-based payments to nonemployees with the guidance for share-based payments to employees. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Changes to the Disclosure Requirements for Fair Value Measurement: In August of 2018, the FASB issued ASU 2018-13 that eliminates, modifies, and adds to certain fair value measurement disclosure requirements associated with the three-tiered fair value hierarchy. This guidance is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Changes to the Disclosure Requirements for Defined Benefit Plans: In August of 2018, the FASB issued ASU 2018-14 that makes minor changes and clarifications to the disclosure requirements for entities that sponsor defined benefit plans. This guidance is effective for annual and interim periods beginning after December 15, 2020. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract: In August of 2018, the FASB issued ASU 2018-15 to reduce diversity in practice by clarifying when implementation costs are required to be capitalized in a cloud computing arrangement that is a service contract. This guidance is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Derivatives and Hedging, Inclusion of the Secured Overnight Financing Rate ("SOFR") Overnight Index Swap Rate as a Benchmark Interest Rate for Hedge Accounting Purposes: In October of 2018, the FASB issued ASU 2018-16 adding the overnight index swap rate based on the SOFR to the list of United States benchmark interest rates eligible for hedge accounting purposes. This guidance is effective for annual and interim periods beginning after December 15, 2018. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Acquisitions	ACQUISITIONS Pending Acquisitions Bridgeview Bancorp, Inc. On December 6, 2018, the Company entered into a merger agreement to acquire Bridgeview Bancorp, Inc. ("Bridgeview"), the holding company for Bridgeview Bank Group. As of September 30, 2018, Bridgeview had approximately $1.2 billion of assets, $1.1 billion of deposits, and $800 million of loans, excluding Bridgeview's mortgage division, which the Company is not acquiring. The merger agreement provides for a fixed exchange ratio of 0.2767 shares of Company common stock, plus $1.79 in cash, for each share of Bridgeview common stock, subject to certain adjustments. As of the date of announcement, the overall transaction was valued at approximately $145 million . The acquisition is subject to customary regulatory approvals, the approval of Bridgeview's stockholders, and the completion of various closing conditions, and is expected to close in the second quarter of 2019. Completed Acquisitions Northern Oak Wealth Management, Inc. On January 16, 2019, the Company completed its acquisition of Northern Oak Wealth Management, Inc. ("Northern Oak"), a registered investment adviser based in Milwaukee, Wisconsin with approximately $800.0 million of assets under management at closing. Northern States Financial Corporation On October 12, 2018, the Company completed its acquisition of Northern States Financial Corporation, ("Northern States"), the holding company for NorStates Bank, based in Waukegan, Illinois. At closing, the Company acquired $578.7 million of total assets, $463.2 million of deposits, and $284.9 million of loans. Under the terms of the merger agreement, on October 12, 2018, each outstanding share of Northern States common stock, excluding shares held in treasury or otherwise owned by the Company or Northern States, was canceled and converted into the right to receive 0.0363 of a share of Company common stock. The merger consideration totaled $83.3 million and resulted in the Company issuing 3,310,912 shares of Company common stock. Goodwill of $29.3 million associated with the acquisition was recorded by the Company. All Northern States operating systems were converted during the fourth quarter of 2018. The fair value adjustments, including goodwill, associated with this transaction remain preliminary and may change as the Company continues to finalize the fair value of the assets and liabilities acquired. Premier Asset Management LLC On February 28, 2017, the Company completed its acquisition of Premier, a registered investment adviser based in Chicago, Illinois with approximately $550.0 million of assets under management at closing. During 2018, the Company finalized the fair value adjustments associated with the Premier transaction, which required a measurement period adjustment of $1.9 million to increase goodwill. This adjustment was recognized in the current period in accordance with accounting guidance applicable to business combinations. Standard Bancshares, Inc. On January 6, 2017, the Company completed its acquisition of Standard Bancshares, Inc. ("Standard") the holding company for Standard Bank and Trust Company. At closing, the Company acquired $2.6 billion of total assets, $2.0 billion of deposits, and $1.8 billion of loans. Under the terms of the merger agreement, each outstanding share of Standard common stock was canceled and converted into the right to receive 0.4350 of a share of Company common stock. The merger consideration totaled $580.7 million , which consisted of 21,057,085 shares of Company common stock and $47.1 million of cash. Goodwill of $345.3 million associated with the acquisition was recorded by the Company. All operating systems were converted during the first quarter of 2017. During 2017, the Company finalized the fair value adjustments associated with the Standard transaction. The following table presents the assets acquired and liabilities assumed, net of the fair value adjustments, in the Northern States and Standard transactions as of the acquisition date. The assets acquired and liabilities assumed, both intangible and tangible, were recorded at their estimated fair values as of the acquisition date and have been accounted for under the acquisition method of accounting. Acquisition Activity (Dollar amounts in thousands, except share and per share data) Northern States Standard October 12, 2018 January 6, 2017 Assets Cash and due from banks and interest-bearing deposits in other banks $ 160,145 $ 102,149 Equity securities 3,915 — Securities available-for-sale 47,149 214,107 FHLB and FRB stock 554 3,247 Loans 284,924 1,762,303 OREO 2,549 8,424 Investment in BOLI 11,104 55,629 Goodwill 29,343 345,334 Other intangible assets 12,230 31,072 Premises, furniture, and equipment 7,039 56,517 Accrued interest receivable and other assets 19,717 60,278 Total assets $ 578,669 $ 2,639,060 Liabilities Noninterest-bearing deposits $ 346,714 $ 675,354 Interest-bearing deposits 116,446 1,348,520 Total deposits 463,160 2,023,874 Borrowed funds 18,218 — Senior and subordinated debt 8,038 — Accrued interest payable and other liabilities 5,950 34,471 Total liabilities 495,366 2,058,345 Consideration Paid Common stock (2018 - 3,310,912, shares issued at $25.16 per share, 2017 - 21,057,085 share issued at $25.34 per share), net of issuance costs 83,303 533,590 Cash paid — 47,125 Total consideration paid 83,303 580,715 $ 578,669 $ 2,639,060 Expenses related to the acquisition and integration of completed and pending transactions totaled $9.6 million , $20.1 million and $14.4 million during the years ended December 31, 2018 , 2017 and 2016 , respectively, and are reported as a separate component within noninterest expense in the Consolidated Statements of Income.

Securities

Securities	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Securities	SECURITIES A summary of the Company's securities portfolio by category and maturity is presented in the following tables. Securities Portfolio (Dollar amounts in thousands) As of December 31, 2018 2017 Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Fair Gains Losses Gains Losses Securities Available-for-Sale U.S. treasury securities $ 37,925 $ 17 $ (175 ) $ 37,767 $ 46,529 $ — $ (184 ) $ 46,345 U.S. agency securities 144,125 45 (1,607 ) 142,563 157,636 197 (986 ) 156,847 Collateralized mortgage 1,336,531 3,362 (24,684 ) 1,315,209 1,113,019 121 (17,954 ) 1,095,186 Other mortgage-backed 477,665 520 (11,251 ) 466,934 373,676 201 (4,334 ) 369,543 Municipal securities 229,600 461 (2,874 ) 227,187 209,558 693 (1,260 ) 208,991 Corporate debt securities 86,074 — (3,725 ) 82,349 — — — — Equity securities (1) — — — — 7,408 194 (305 ) 7,297 Total securities available-for-sale $ 2,311,920 $ 4,405 $ (44,316 ) $ 2,272,009 $ 1,907,826 $ 1,406 $ (25,023 ) $ 1,884,209 Securities Held-to-Maturity Municipal securities $ 10,176 $ — $ (305 ) $ 9,871 $ 13,760 $ — $ (1,747 ) $ 12,013 Equity Securities (1) $ 30,806 $ — Trading Securities (1) $ — $ 20,447 (1) As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements." Remaining Contractual Maturity of Securities (Dollar amounts in thousands) As of December 31, 2018 Available-for-Sale Held-to-Maturity Amortized Cost Fair Value Amortized Cost Fair Value One year or less $ 113,548 $ 111,755 $ 7,580 $ 7,353 After one year to five years 176,349 173,565 2,236 2,169 After five years to ten years 207,827 204,546 360 349 After ten years — — — — Securities that do not have a single contractual maturity date 1,814,196 1,782,143 — — Total $ 2,311,920 $ 2,272,009 $ 10,176 $ 9,871 The carrying value of securities available-for-sale that were pledged to secure deposits or for other purposes as permitted or required by law totaled $1.2 billion for December 31, 2018 and $1.1 billion for December 31, 2017 . No securities held-to-maturity were pledged as of December 31, 2018 or 2017 . Excluding securities issued or backed by the U.S. government and its agencies and U.S. government-sponsored enterprises, there were no investments in securities from one issuer that exceeded 10% of total stockholders' equity as of December 31, 2018 or 2017 . During the years ended December 31, 2018 , 2017 , and 2016 there were no material gross trading gains (losses). The following table presents net realized gains (losses) on securities available-for-sale for the three years ended December 31, 2018 . Securities Available-for-Sale Gains (Losses) (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Gains (losses) on sales of securities: Gross realized gains $ — $ 5,478 $ 1,589 Gross realized losses — (7,354 ) (169 ) Net realized gains (losses) on sales of securities — (1,876 ) 1,420 Non-cash impairment charges: OTTI — — — Net realized gains (losses) $ — $ (1,876 ) $ 1,420 There were no net securities gains (losses) recognized during the year ended December 31, 2018. Securities of $47.1 million were acquired in the Northern States transaction during the fourth quarter of 2018, of which $25.0 million were sold shortly after the acquisition and resulted in no gains or losses as they were recorded at fair value upon acquisition. During 2017, net realized losses on sales of securities consisted primarily of sales of CMOs and trust-preferred collateralized debt obligations at net losses of $3.2 million and partially offset by sales of municipal and other securities at net gains of $1.3 million . Net securities gains for 2016 consisted primarily of sales of municipal securities at net gains of $1.1 million and equity securities at net gains of $304,000 . Accounting guidance requires that the credit portion of an OTTI charge be recognized through income. If a decline in fair value below carrying value is not attributable to credit deterioration and the Company does not intend to sell the security or believe it would not be more likely than not required to sell the security prior to recovery, the Company records the non-credit related portion of the decline in fair value in other comprehensive (loss) income . The following table presents a rollforward of life-to-date OTTI recognized in earnings related to all securities available-for-sale held by the Company for the years ended December 31, 2018 , 2017 , and 2016 . Changes in OTTI Recognized in Earnings (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ — $ 23,345 $ 23,345 OTTI included in earnings (1) : Reduction for securities sales (2) — (23,345 ) — Ending balance $ — $ — $ 23,345 (1) Included in net securities gains (losses) in the Consolidated Statements of Income. (2) These reductions were driven by the sale of 11 CDOs with a carrying value of $47.7 million during the year ended December 31, 2017. The following table presents the aggregate amount of unrealized losses and the aggregate related fair values of securities with unrealized losses as of December 31, 2018 and 2017 . Securities in an Unrealized Loss Position (Dollar amounts in thousands) Less Than 12 Months Greater Than 12 Months Total Number of Securities Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses As of December 31, 2018 Securities Available-for-Sale U.S. treasury securities 17 $ 15,894 $ 57 $ 13,886 $ 118 $ 29,780 $ 175 U.S. agency securities 74 34,263 320 93,227 1,287 127,490 1,607 CMOs 234 171,901 1,671 863,747 23,013 1,035,648 24,684 MBSs 118 135,791 1,715 284,273 9,536 420,064 11,251 Municipal securities 423 60,863 558 109,935 2,316 170,798 2,874 Corporate debt securities 16 82,349 3,725 — — 82,349 3,725 Total 882 $ 501,061 $ 8,046 $ 1,365,068 $ 36,270 $ 1,866,129 $ 44,316 Securities Held-to-Maturity Municipal securities 5 $ — $ — $ 9,871 $ 305 $ 9,871 $ 305 As of December 31, 2017 Securities Available-for-Sale U.S. treasury securities 20 $ 19,918 $ 87 $ 26,427 $ 97 $ 46,345 $ 184 U.S. agency securities 72 66,899 300 58,021 686 124,920 986 CMOs 211 365,131 3,265 633,227 14,689 998,358 17,954 MBSs 86 126,136 902 210,017 3,432 336,153 4,334 Municipal securities 265 35,500 479 81,360 781 116,860 1,260 Equity securities (1) 2 391 214 6,386 91 6,777 305 Total 656 $ 613,975 $ 5,247 $ 1,015,438 $ 19,776 $ 1,629,413 $ 25,023 Securities Held-to-Maturity Municipal securities 8 $ — $ — $ 12,013 $ 1,747 $ 12,013 $ 1,747 (1) As a result of accounting guidance adopted in 2018, equity securities are no longer presented within securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2, "Recent Accounting Pronouncements." Substantially all of the Company's CMOs and other MBSs are either backed by U.S. government-owned agencies or issued by U.S. government-sponsored enterprises. Municipal securities are issued by municipal authorities, and the majority are supported by third-party insurance or some other form of credit enhancement. Management does not believe any of these securities with unrealized losses as of December 31, 2018 represent OTTI related to credit deterioration. These unrealized losses are attributed to changes in interest rates and temporary market movements. The Company does not intend to sell these securities and it is not more likely than not that the Company will be required to sell them before recovery of their amortized cost basis, which may be at maturity.

Loans

Loans	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Loans	LOANS Loans Held-for-Investment The following table presents the Company's loans held-for-investment by class. Loan Portfolio (Dollar amounts in thousands) As of December 31, 2018 2017 Commercial and industrial $ 4,120,293 $ 3,529,914 Agricultural 430,928 430,886 Commercial real estate: Office, retail, and industrial 1,820,917 1,979,820 Multi-family 764,185 675,463 Construction 649,337 539,820 Other commercial real estate 1,361,810 1,358,515 Total commercial real estate 4,596,249 4,553,618 Total corporate loans 9,147,470 8,514,418 Home equity 851,607 827,055 1-4 family mortgages 1,017,181 774,357 Installment 430,525 321,982 Total consumer loans 2,299,313 1,923,394 Total loans $ 11,446,783 $ 10,437,812 Deferred loan fees included in total loans $ 6,715 $ 4,986 Overdrawn demand deposits included in total loans 8,583 8,587 The Company primarily lends to community-based and mid-sized businesses, commercial real estate customers, and consumers in its markets. Within these areas, the Company diversifies its loan portfolio by loan type, industry, and borrower. Commercial and industrial loans are underwritten after evaluating and understanding the borrower's ability to operate its business. As part of the underwriting process, the Company examines current and expected future cash flows to determine the ability of the borrower to repay its obligation. Commercial and industrial loans are primarily made based on the identified cash flows of the borrower and secondarily on the underlying collateral provided by the borrower. The cash flows of the borrower may not be as expected, and the collateral securing these loans may fluctuate in value due to the success of the business or economic conditions. Most commercial and industrial loans are secured by the assets being financed or other business assets, such as accounts receivable or inventory, and may incorporate a personal guarantee. In the case of loans secured by accounts receivable, the availability of funds for the repayment of these loans substantially depend on the ability of the borrower to collect amounts due from its customers. Some short-term loans may be made on an unsecured basis. Agricultural loans are generally provided to meet seasonal production, equipment, and farm real estate borrowing needs of individual and corporate crop and livestock producers. Seasonal crop production loans are repaid by the liquidation of the financed crop that is typically covered by crop insurance. Equipment and real estate term loans are repaid through cash flows of the farming operation. As part of the underwriting process, the Company examines projected future cash flows, financial statement stability, and the value of the underlying collateral. Commercial real estate loans are subject to underwriting standards and processes similar to commercial and industrial loans. The repayment of commercial real estate loans depends on the successful operation of the property securing the loan or the business conducted on the property securing the loan. This category of loans may be more adversely affected by conditions in real estate markets. Management monitors and evaluates commercial real estate loans based on cash flow, collateral, geography, and risk rating criteria. The mix of properties securing the loans in our commercial real estate portfolio is balanced between owner-occupied and investor categories and is diverse in terms of type and geographic location, generally within the Company's markets. Construction loans are generally made based on estimates of costs and values associated with the completed projects and are underwritten utilizing feasibility studies, independent appraisal reviews, sensitivity analyses of absorption and lease rates, and financial analyses of the developers and property owners. Sources of repayment may be permanent long-term financing, sales of developed property, or an interim loan commitment until permanent financing is obtained. Generally, construction loans have a higher risk profile than other real estate loans since repayment is impacted by real estate values, interest rate changes, governmental regulation of real property, demand and supply of alternative real estate, the availability of long-term financing, and changes in general economic conditions. Consumer loans are centrally underwritten using a credit scoring model developed by the Fair Isaac Corporation ("FICO"), which employs a risk-based system to determine the probability that a borrower may default. Underwriting standards for home equity loans are heavily influenced by statutory requirements, which include loan-to-value and affordability ratios, risk-based pricing strategies, and documentation requirements. The home equity category consists mainly of revolving lines of credit secured by junior liens on owner-occupied real estate. Loan-to-value ratios on home equity loans and 1-4 family mortgages are based on the current appraised value of the collateral. Repayment for these loans is dependent on the borrower's continued financial stability, and is more likely to be impacted by adverse personal circumstances. The Bank is a member of the FHLB and FRB and has access to financing secured by designated assets that may include qualifying commercial real estate, residential and multi-family mortgages, home equity loans, and certain municipal and mortgage-backed securities. The carrying value of loans that were pledged to secure liabilities as of December 31, 2018 and 2017 are presented below. Carrying Value of Loans Pledged (Dollar amounts in thousands) As of December 31 2018 2017 Loans pledged to secure: FHLB advances (blanket pledge) $ 4,443,268 $ 4,587,240 FRB's Discount Window Primary Credit Program 1,166,128 1,099,712 Total $ 5,609,396 $ 5,686,952 As of both December 31, 2018 and 2017 , based on loans pledged under a blanket pledge agreement noted in the table above, the Bank was eligible to borrow up to $2.5 billion in FHLB advances. As of December 31, 2018 and 2017 , the Bank was eligible to borrow up to $881.1 million and $843.6 million , respectively, through the FRB's Discount Window Primary Credit Program based on assets pledged. For additional disclosure related to the Company's outstanding balance of borrowings, see Note 11 , " Borrowed Funds ." Loan Sales The following table presents loan sales for the years ended December 31, 2018 , 2017 , and 2016 . Loan Sales (Dollar amounts in thousands) As of December 31, 2018 2017 2016 Corporate loan sales Proceeds from sales $ 17,900 $ 52,974 $ 54,681 Less book value of loans sold 17,498 51,781 52,821 Net gains on corporate sales (1) 402 1,193 1,860 1-4 family mortgage loan sales Proceeds from sales 245,967 258,626 290,383 Less book value of loans sold 240,807 252,741 283,312 Net gains on 1-4 family mortgage sales (2) 5,160 5,885 7,071 Total net gains on loan sales $ 5,562 $ 7,078 $ 8,931 (1) Net gains on corporate loan sales are included in other service charges, commissions, and fees in the Consolidated Statements of Income. (2) Net gains on 1-4 family mortgage loan sales are included in mortgage banking income in the Consolidated Statements of Income. The Company retained servicing responsibilities for a portion of the 1-4 family mortgage loans sold and collects servicing fees equal to a percentage of the outstanding principal balance. For additional disclosure related to the Company's obligations resulting from the sale of certain 1-4 family mortgage loans, see Note 20 , " Commitments, Guarantees, and Contingent Liabilities ."

Acquired and Covered Loans

Acquired and Covered Loans	12 Months Ended
	Dec. 31, 2018
Transfers and Servicing [Abstract]
Acquired and Covered Loans	ACQUIRED AND COVERED LOANS Covered loans consist of loans acquired by the Company in FDIC-assisted transactions which are covered by the FDIC Agreements. Acquired loans consist of all other loans that were acquired in business combinations that are not covered by the FDIC Agreements. Both acquired and covered loans are included in loans in the Consolidated Statements of Financial Condition. The significant accounting policies related to acquired and covered loans, which are classified as PCI and non-PCI, and the related FDIC indemnification asset, are presented in Note 1 , " Summary of Significant Accounting Policies ." Non-residential mortgage loans related to FDIC-assisted transactions are no longer covered under the FDIC Agreements. These non-residential loans, which totaled $10.4 million and $12.7 million as of December 31, 2018 and 2017 , respectively, are included in acquired loans and no longer classified as covered loans. The losses on residential mortgage loans will continue to be covered under the FDIC Agreements through various dates between December 31, 2019 and September 30, 2020. The following table presents acquired and covered PCI and Non-PCI loans as of December 31, 2018 and 2017 . Acquired and Covered Loans (Dollar amounts in thousands) As of December 31, 2018 2017 PCI Non-PCI Total PCI Non-PCI Total Acquired loans $ 108,049 $ 1,247,492 $ 1,355,541 $ 130,694 $ 1,512,664 $ 1,643,358 Covered loans 5,819 4,869 10,688 6,759 11,789 18,548 Total acquired and covered loans $ 113,868 $ 1,252,361 $ 1,366,229 $ 137,453 $ 1,524,453 $ 1,661,906 The outstanding balance of PCI loans was $175.2 million and $210.7 million as of December 31, 2018 and 2017 , respectively. Acquired non-PCI loans that are renewed are no longer classified as acquired loans. These loans totaled $458.0 million and $366.0 million as of December 31, 2018 and 2017 , respectively. In connection with the FDIC Agreements, the Company recorded an indemnification asset. To maintain eligibility for the loss share reimbursement, the Company is required to follow certain servicing procedures as specified in the FDIC Agreements. The Company was in compliance with those requirements as of December 31, 2018 , 2017 , and 2016 . A rollforward of the carrying value of the FDIC indemnification asset for the three years ended December 31, 2018 is presented in the following table. Changes in the FDIC Indemnification Asset (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 3,314 $ 4,522 $ 3,903 Amortization (1,208 ) (1,208 ) (1,185 ) Change in expected reimbursements from the FDIC for changes in expected credit losses (237 ) (792 ) 330 Net payments to the FDIC 235 792 1,474 Ending balance $ 2,104 $ 3,314 $ 4,522 Changes in the accretable yield for acquired and covered PCI loans were as follows. Changes in Accretable Yield (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 32,957 $ 19,386 $ 24,912 Additions 3,699 27,316 3,981 Accretion (12,354 ) (15,529 ) (8,063 ) Other (1) 19,423 1,784 (1,444 ) Ending balance $ 43,725 $ 32,957 $ 19,386 (1) Increases represent a rise in the expected future cash flows to be collected over the remaining estimated life of the underlying portfolio while decreases result from the resolution of certain loans occurring earlier than anticipated. Total accretion on acquired and covered PCI and non-PCI loans for December 31, 2018 , 2017 , and 2016 was $19.5 million , $33.9 million , and $14.6 million , respectively.

Past Due Loans, Allowance For C

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs	12 Months Ended
	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs	PAST DUE LOANS, ALLOWANCE FOR CREDIT LOSSES, IMPAIRED LOANS, AND TDRS Past Due and Non-accrual Loans The following table presents an aging analysis of the Company's past due loans as of December 31, 2018 and 2017 . The aging is determined without regard to accrual status. The table also presents non-performing loans, consisting of non-accrual loans (the majority of which are past due) and loans 90 days or more past due and still accruing interest, as of each balance sheet date. Aging Analysis of Past Due Loans and Non-Performing Loans by Class (Dollar amounts in thousands) Aging Analysis (Accruing and Non-accrual) Non-performing Loans Current (1) 30-89 Days Past Due 90 Days or More Past Due Total Past Due Total Loans Non-accrual (2) 90 Days or More Past Due, Still Accruing Interest As of December 31, 2018 Commercial and industrial $ 4,085,164 $ 8,832 $ 26,297 $ 35,129 $ 4,120,293 $ 33,507 $ 422 Agricultural 428,357 940 1,631 2,571 430,928 1,564 101 Commercial real estate: Office, retail, and industrial 1,803,059 8,209 9,649 17,858 1,820,917 6,510 4,081 Multi-family 759,402 1,487 3,296 4,783 764,185 3,107 189 Construction 645,774 3,419 144 3,563 649,337 144 — Other commercial real estate 1,353,442 4,921 3,447 8,368 1,361,810 2,854 2,197 Total commercial real estate 4,561,677 18,036 16,536 34,572 4,596,249 12,615 6,467 Total corporate loans 9,075,198 27,808 44,464 72,272 9,147,470 47,686 6,990 Home equity 843,217 6,285 2,105 8,390 851,607 5,393 104 1-4 family mortgages 1,009,925 4,361 2,895 7,256 1,017,181 3,856 1,147 Installment 428,836 1,648 41 1,689 430,525 — 41 Total consumer loans 2,281,978 12,294 5,041 17,335 2,299,313 9,249 1,292 Total loans $ 11,357,176 $ 40,102 $ 49,505 $ 89,607 $ 11,446,783 $ 56,935 $ 8,282 As of December 31, 2017 Commercial and industrial $ 3,490,783 $ 34,620 $ 4,511 $ 39,131 $ 3,529,914 $ 40,580 $ 1,830 Agricultural 430,221 280 385 665 430,886 219 177 Commercial real estate: Office, retail, and industrial 1,970,564 3,156 6,100 9,256 1,979,820 11,560 345 Multi-family 672,098 3,117 248 3,365 675,463 377 20 Construction 539,043 198 579 777 539,820 209 371 Other commercial real estate 1,353,263 2,545 2,707 5,252 1,358,515 3,621 317 Total commercial real estate 4,534,968 9,016 9,634 18,650 4,553,618 15,767 1,053 Total corporate loans 8,455,972 43,916 14,530 58,446 8,514,418 56,566 3,060 Home equity 820,099 4,102 2,854 6,956 827,055 5,946 98 1-4 family mortgages 770,120 2,145 2,092 4,237 774,357 4,412 — Installment 319,178 2,407 397 2,804 321,982 — 397 Total consumer loans 1,909,397 8,654 5,343 13,997 1,923,394 10,358 495 Total loans $ 10,365,369 $ 52,570 $ 19,873 $ 72,443 $ 10,437,812 $ 66,924 $ 3,555 (1) PCI loans with an accretable yield are considered current. (2) Includes PCI loans of $58,000 and $763,000 as of December 31, 2018 and December 31, 2017 , respectively, which no longer have an accretable yield as estimates of expected future cash flows have decreased since the acquisition due to credit deterioration. Allowance for Credit Losses The Company maintains an allowance for credit losses at a level deemed adequate by management to absorb estimated losses inherent in the existing loan portfolio. See Note 1 , " Summary of Significant Accounting Policies ," for the accounting policy for the allowance for credit losses. A rollforward of the allowance for credit losses by portfolio segment for the years ended December 31, 2018 , 2017 , and 2016 is presented in the table below. Allowance for Credit Losses by Portfolio Segment (Dollar amounts in thousands) Commercial, Industrial, and Agricultural Office, Retail, and Industrial Multi-family Construction Other Commercial Real Estate Consumer Reserve for Unfunded Commitments Total Allowance for Credit Losses Year Ended December 31, 2018 Beginning balance $ 55,791 $ 10,996 $ 2,534 $ 3,481 $ 6,381 $ 16,546 $ 1,000 $ 96,729 Charge-offs (36,477 ) (2,286 ) (5 ) (1 ) (410 ) (8,806 ) — (47,985 ) Recoveries 2,946 334 3 125 1,532 1,681 — 6,621 Net charge-offs (33,531 ) (1,952 ) (2 ) 124 1,122 (7,125 ) — (41,364 ) Provision for loan 41,016 (1,144 ) (68 ) (1,432 ) (2,569 ) 12,051 200 48,054 Ending Balance $ 63,276 $ 7,900 $ 2,464 $ 2,173 $ 4,934 $ 21,472 $ 1,200 $ 103,419 Year Ended December 31, 2017 Beginning balance $ 40,709 $ 17,595 $ 3,261 $ 3,444 $ 7,739 $ 13,335 $ 1,000 $ 87,083 Charge-offs (22,885 ) (190 ) — (38 ) (755 ) (6,955 ) — (30,823 ) Recoveries 4,150 2,935 39 270 244 1,541 — 9,179 Net charge-offs (18,735 ) 2,745 39 232 (511 ) (5,414 ) — (21,644 ) Provision for loan losses and other 33,817 (9,344 ) (766 ) (195 ) (847 ) 8,625 — 31,290 Ending balance $ 55,791 $ 10,996 $ 2,534 $ 3,481 $ 6,381 $ 16,546 $ 1,000 $ 96,729 Year Ended December 31, 2016 Beginning balance $ 37,074 $ 13,124 $ 2,469 $ 1,440 $ 6,109 $ 13,414 $ 1,225 $ 74,855 Charge-offs (9,982 ) (4,707 ) (307 ) (134 ) (2,932 ) (5,231 ) — (23,293 ) Recoveries 2,451 337 97 56 524 1,298 — 4,763 Net charge-offs (7,531 ) (4,370 ) (210 ) (78 ) (2,408 ) (3,933 ) — (18,530 ) Provision for loan 11,166 8,841 1,002 2,082 4,038 3,854 (225 ) 30,758 Ending balance $ 40,709 $ 17,595 $ 3,261 $ 3,444 $ 7,739 $ 13,335 $ 1,000 $ 87,083 The table below provides a breakdown of loans and the related allowance for credit losses by portfolio segment as of December 31, 2018 and 2017 . Loans and Related Allowance for Credit Losses by Portfolio Segment (Dollar amounts in thousands) Loans Allowance for Credit Losses Individually Evaluated for Impairment Collectively Evaluated for Impairment PCI Total Individually Evaluated for Impairment Collectively Evaluated for Impairment PCI Total As of December 31, 2018 Commercial, industrial, and $ 32,415 $ 4,514,349 $ 4,457 $ 4,551,221 $ 3,961 $ 58,947 $ 368 $ 63,276 Commercial real estate: Office, retail, and industrial 5,057 1,799,304 16,556 1,820,917 748 5,984 1,168 7,900 Multi-family 3,492 747,030 13,663 764,185 — 2,154 310 2,464 Construction — 644,499 4,838 649,337 — 2,019 154 2,173 Other commercial real estate 1,545 1,305,444 54,821 1,361,810 — 4,180 754 4,934 Total commercial real estate 10,094 4,496,277 89,878 4,596,249 748 14,337 2,386 17,471 Total corporate loans 42,509 9,010,626 94,335 9,147,470 4,709 73,284 2,754 80,747 Consumer — 2,279,780 19,533 2,299,313 — 20,094 1,378 21,472 Reserve for unfunded — — — — — 1,200 — 1,200 Total loans $ 42,509 $ 11,290,406 $ 113,868 $ 11,446,783 $ 4,709 $ 94,578 $ 4,132 $ 103,419 As of December 31, 2017 Commercial, industrial, and $ 38,718 $ 3,909,380 $ 12,702 $ 3,960,800 $ 10,074 $ 45,293 $ 424 $ 55,791 Commercial real estate: Office, retail, and industrial 10,810 1,954,435 14,575 1,979,820 — 9,333 1,663 10,996 Multi-family 621 660,771 14,071 675,463 — 2,436 98 2,534 Construction — 530,977 8,843 539,820 — 3,331 150 3,481 Other commercial real estate 1,468 1,291,723 65,324 1,358,515 — 5,415 966 6,381 Total commercial real estate 12,899 4,437,906 102,813 4,553,618 — 20,515 2,877 23,392 Total corporate loans 51,617 8,347,286 115,515 8,514,418 10,074 65,808 3,301 79,183 Consumer — 1,901,456 21,938 1,923,394 — 15,533 1,013 16,546 Reserve for unfunded — — — — — 1,000 — 1,000 Total loans $ 51,617 $ 10,248,742 $ 137,453 $ 10,437,812 $ 10,074 $ 82,341 $ 4,314 $ 96,729 Loans Individually Evaluated for Impairment The following table presents loans individually evaluated for impairment by class of loan as of December 31, 2018 and 2017 . PCI loans are excluded from this disclosure. Impaired Loans Individually Evaluated by Class (Dollar amounts in thousands) As of December 31, 2018 2017 Recorded Investment In Recorded Investment In Loans with No Specific Reserve Loans with a Specific Reserve Unpaid Principal Balance Specific Reserve Loans with No Specific Reserve Loans with a Specific Reserve Unpaid Principal Balance Specific Reserve Commercial and industrial $ 7,550 $ 23,349 $ 49,102 $ 3,960 $ 4,234 $ 34,484 $ 53,192 $ 10,074 Agricultural 1,318 198 3,997 1 — — — — Commercial real estate: Office, retail, and industrial 1,861 3,196 6,141 748 7,154 3,656 14,246 — Multi-family 3,492 — 3,492 — 621 — 621 — Construction — — — — — — — — Other commercial real estate 1,545 — 1,612 — 1,468 — 1,566 — Total commercial real estate 6,898 3,196 11,245 748 9,243 3,656 16,433 — Total impaired loans $ 15,766 $ 26,743 $ 64,344 $ 4,709 $ 13,477 $ 38,140 $ 69,625 $ 10,074 The following table presents the average recorded investment and interest income recognized on impaired loans by class for the years ended December 31, 2018 , 2017 , and 2016 . PCI loans are excluded from this disclosure. Average Recorded Investment and Interest Income Recognized on Impaired Loans by Class (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Average Recorded Investment Interest Income Recognized (1) Average Recorded Investment Interest Income Recognized (1) Average Interest (1) Commercial and industrial $ 33,732 $ 225 $ 33,956 $ 1,059 $ 9,178 $ 104 Agricultural 2,026 32 279 101 — — Commercial real estate: Office, retail, and industrial 8,105 892 13,106 325 12,867 291 Multi-family 2,404 66 441 28 479 11 Construction — — 7 136 63 — Other commercial real estate 2,179 406 1,615 41 2,809 86 Total commercial real estate 12,688 1,364 15,170 530 16,218 388 Total impaired loans $ 48,445 $ 1,621 $ 49,404 $ 1,690 $ 25,396 $ 492 (1) Recorded using the cash basis of accounting. Credit Quality Indicators Corporate loans and commitments are assessed for credit risk and assigned ratings based on various characteristics, such as the borrower's cash flow, leverage, and collateral. Ratings for commercial credits are reviewed periodically. The following tables present credit quality indicators by class for corporate and consumer loans as of December 31, 2018 and 2017 . Corporate Credit Quality Indicators by Class (Dollar amounts in thousands) Pass Special (1)(4) Substandard (2)(4) Non-accrual (3) Total As of December 31, 2018 Commercial and industrial $ 3,952,066 $ 74,878 $ 59,842 $ 33,507 $ 4,120,293 Agricultural 407,542 10,070 11,752 1,564 430,928 Commercial real estate: Office, retail, and industrial 1,735,426 35,853 43,128 6,510 1,820,917 Multi-family 745,131 9,273 6,674 3,107 764,185 Construction 624,446 16,370 8,377 144 649,337 Other commercial real estate 1,294,128 47,736 17,092 2,854 1,361,810 Total commercial real estate 4,399,131 109,232 75,271 12,615 4,596,249 Total corporate loans $ 8,758,739 $ 194,180 $ 146,865 $ 47,686 $ 9,147,470 As of December 31, 2017 Commercial and industrial $ 3,388,133 $ 70,863 $ 30,338 $ 40,580 $ 3,529,914 Agricultural 413,946 10,989 5,732 219 430,886 Commercial real estate: Office, retail, and industrial 1,903,737 25,546 38,977 11,560 1,979,820 Multi-family 665,496 7,395 2,195 377 675,463 Construction 521,911 10,184 7,516 209 539,820 Other commercial real estate 1,304,337 29,624 20,933 3,621 1,358,515 Total commercial real estate 4,395,481 72,749 69,621 15,767 4,553,618 Total corporate loans $ 8,197,560 $ 154,601 $ 105,691 $ 56,566 $ 8,514,418 (1) Loans categorized as special mention exhibit potential weaknesses that require the close attention of management since these potential weaknesses may result in the deterioration of repayment prospects in the future. (2) Loans categorized as substandard exhibit a well-defined weakness that may jeopardize the liquidation of the debt. These loans continue to accrue interest because they are well-secured and collection of principal and interest is expected within a reasonable time. (3) Loans categorized as non-accrual exhibit a well-defined weakness that may jeopardize the liquidation of the debt or result in a loss if the deficiencies are not corrected. (4) Total special mention and substandard loans includes accruing TDRs of $630,000 as of December 31, 2018 and $657,000 as of December 31, 2017 . Consumer Credit Quality Indicators by Class (Dollar amounts in thousands) Performing Non-accrual Total As of December 31, 2018 Home equity $ 846,214 $ 5,393 $ 851,607 1-4 family mortgages 1,013,325 3,856 1,017,181 Installment 430,525 — 430,525 Total consumer loans $ 2,290,064 $ 9,249 $ 2,299,313 As of December 31, 2017 Home equity $ 821,109 $ 5,946 $ 827,055 1-4 family mortgages 769,945 4,412 774,357 Installment 321,982 — 321,982 Total consumer loans $ 1,913,036 $ 10,358 $ 1,923,394 TDRs TDRs are generally performed at the request of the individual borrower and may include forgiveness of principal, reduction in interest rates, changes in payments, and maturity date extensions. The table below presents TDRs by class as of December 31, 2018 and 2017 . See Note 1 , " Summary of Significant Accounting Policies ," for the accounting policy for TDRs. TDRs by Class (Dollar amounts in thousands) As of December 31, 2018 2017 Accruing Non-accrual (1) Total Accruing Non-accrual (1) Total Commercial and industrial $ 246 $ 5,994 $ 6,240 $ 264 $ 18,959 $ 19,223 Agricultural — — — — — — Commercial real estate: Office, retail, and industrial — — — — 4,236 4,236 Multi-family 557 — 557 574 149 723 Construction — — — — — — Other commercial real estate 181 — 181 192 — 192 Total commercial real estate 738 — 738 766 4,385 5,151 Total corporate loans 984 5,994 6,978 1,030 23,344 24,374 Home equity 113 327 440 86 738 824 1-4 family mortgages 769 291 1,060 680 451 1,131 Installment — — — — — — Total consumer loans 882 618 1,500 766 1,189 1,955 Total loans $ 1,866 $ 6,612 $ 8,478 $ 1,796 $ 24,533 $ 26,329 (1) These TDRs are included in non-accrual loans in the preceding tables. TDRs are included in the calculation of the allowance for credit losses in the same manner as impaired loans. There were no specific reserves related to TDRs as of December 31, 2018 , and there were $2.0 million specific reserves related to TDRs as of December 31, 2017 . There were no material restructurings during the year ended December 31, 2018 . The following table presents a summary of loans that were restructured during the years ended December 31, 2017 , and 2016 . Loans Restructured During the Period (Dollar amounts in thousands) Number of Loans Pre-Modification Recorded Investment Funds Disbursed Interest and Escrow Capitalized Charge-offs Post-Modification Recorded Investment Year Ended December 31, 2017 Commercial and industrial 12 $ 26,733 $ 9,035 $ — $ 6,232 $ 29,536 Office, retail, and industrial 2 3,656 — — — 3,656 Total loans restructured during the period 14 $ 30,389 $ 9,035 $ — $ 6,232 $ 33,192 Year Ended December 31, 2016 Office, retail, and industrial 1 $ 5,460 $ — $ — $ 1,083 $ 4,377 Other commercial real estate 1 745 — — — 745 Total loans restructured during the period 2 $ 6,205 $ — $ — $ 1,083 $ 5,122 Accruing TDRs that do not perform in accordance with their modified terms are transferred to non-accrual. No TDRs had payment defaults during the years ended December 31, 2018 , and 2017 where the default occurred within twelve months of the restructure date. For the year ended December 31, 2016, one home equity TDR totaling $119,000 defaulted within twelve months of the restructure date. A rollforward of the carrying value of TDRs for the years ended December 31, 2018 , 2017 , and 2016 is presented in the following table. TDR Rollforward (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Accruing Beginning balance $ 1,796 $ 2,291 $ 2,743 Additions — 15,819 — Net payments (50 ) (1,923 ) (120 ) Returned to performing status — — — Net transfers from (to) non-accrual 120 (14,391 ) (332 ) Ending balance 1,866 1,796 2,291 Non-accrual Beginning balance 24,533 6,297 2,324 Additions 527 14,570 6,205 Net payments (14,403 ) (4,380 ) (1,072 ) Charge-offs (3,925 ) (6,345 ) (1,492 ) Transfers to OREO — — — Loans sold — — — Net transfers (to) from accruing (120 ) 14,391 332 Ending balance 6,612 24,533 6,297 Total TDRs $ 8,478 $ 26,329 $ 8,588 There were $3.8 million of commitments to lend additional funds to borrowers with TDRs as of December 31, 2018 and there were no material commitments to lend additional funds to borrowers with TDRs as of December 31, 2017 .

Premises, Furniture, and Equipm

Premises, Furniture, and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Premises, Furniture, and Equipment	PREMISES, FURNITURE, AND EQUIPMENT The following table summarizes the Company's premises, furniture, and equipment by category. Premises, Furniture, and Equipment (Dollar amounts in thousands) As of December 31, 2018 2017 Land $ 28,187 $ 30,470 Premises 122,003 123,873 Furniture and equipment 127,421 115,013 Total cost 277,611 269,356 Accumulated depreciation (148,831 ) (148,248 ) Net book value of premises, furniture, and equipment 128,780 121,108 Assets held-for-sale 3,722 2,208 Premises, furniture, and equipment, net $ 132,502 $ 123,316 During 2016, the Bank completed a sale-leaseback transaction, whereby the Bank sold to a third-party 55 branches and concurrently entered into triple net lease agreements with certain affiliates of the third-party for each of the branches sold. The sale-leaseback transaction resulted in a pre-tax gain of $88.0 million , net of transaction related expenses, of which $5.5 million was immediately recognized in earnings. Remaining pre-tax gains were $65.5 million and $74.6 million as of December 31, 2018 and 2017 , respectively and are accreted as a reduction to lease expense in net occupancy and equipment expense in the Consolidated Statement of Income on a straight-line basis over the initial terms of the lease. Upon adoption of new lease guidance on January 1, 2019, the pre-tax gain will be recognized immediately as a cumulative-effect adjustment to equity in the Consolidated Statements of Financial Condition. For additional detail regarding the new lease guidance see Note 2 "Recent Accounting Pronouncements". As of December 31, 2018 and 2017 , assets held-for-sale consisted of former branches that are no longer in operation and parcels of land previously purchased for expansion. Depreciation on premises, furniture, and equipment totaled $15.9 million in 2018 , $14.0 million in 2017 , and $12.8 million in 2016 . Operating Leases As of December 31, 2018 , the Company was obligated to utilize certain premises and equipment under certain non-cancelable operating leases, which expire at various dates through the year ending December 31, 2033 . Many of these leases contain renewal options and certain leases provide options to purchase the leased property during or at the expiration of the lease period at specific prices. Some leases contain escalation clauses calling for rentals to be adjusted for increased real estate taxes and other operating expenses or proportionately adjusted for increases in consumer or other price indices. The following summary reflects the future minimum payments by year required under operating leases that have initial or remaining non-cancelable lease terms in excess of one year as of December 31, 2018 . Future Minimum Operating Lease Payments (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 15,811 2020 16,780 2021 16,976 2022 16,967 2023 17,100 2024 and thereafter 117,806 Total minimum lease payments $ 201,440 The Company assumed certain operating leases related to various branches in previous acquisitions. An intangible liability is recorded when the cash flows of a lease exceed its fair market value. This intangible liability is accreted into income as a reduction to net occupancy and equipment expense using the straight-line method over the initial term of each lease, which expire between 2022 and 2030. The intangible liability is included in accrued interest and other liabilities in the Consolidated Statements of Financial Condition. The following table presents the remaining scheduled accretion of the intangible liability by year. Scheduled Accretion of Operating Lease Intangible (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 648 2020 648 2021 648 2022 639 2023 612 2024 and thereafter 2,745 Total accretion $ 5,940 The following table presents net operating lease expense for the years ended December 31, 2018 , 2017 , and 2016 . Net Operating Lease Expense (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Lease expense charged to operations $ 24,880 $ 18,666 $ 11,207 Accretion of operating lease intangible (1) (972 ) (1,180 ) (1,171 ) Accretion of deferred gain on sale-leaseback transaction (1) (9,126 ) (5,872 ) (1,473 ) Rental income from premises leased to others (1) (510 ) (682 ) (527 ) Net operating lease expense $ 14,272 $ 10,932 $ 8,036 (1) Included as reductions to net occupancy and equipment expense in the Consolidated Statements of Income.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	GOODWILL AND OTHER INTANGIBLE ASSETS The Company's annual goodwill impairment test was performed as of October 1, 2018 . It was determined that no impairment existed as of that date or as of December 31, 2018 . For a discussion of the accounting policies for goodwill and other intangible assets, see Note 1 , " Summary of Significant Accounting Policies ." The following table presents changes in the carrying amount of goodwill for the years ended December 31, 2018 , 2017 , and 2016 . Changes in the Carrying Amount of Goodwill (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 697,608 $ 340,879 $ 319,007 Acquisitions 31,201 356,729 21,872 Ending balance $ 728,809 $ 697,608 $ 340,879 The increase in goodwill for the year ended December 31, 2018 resulted from the Northern States acquisition and measurement period adjustment related to finalizing the fair values of the assets acquired and liabilities assumed in the Premier acquisition. During the year ended December 31, 2017 the increase resulted from the Standard and Premier acquisitions and measurement period adjustments related to the NI Bancshares acquisition. During the year ended December 31, 2016 , the increase in goodwill resulted from the NI Bancshares acquisition and measurement period adjustments related to the Peoples Bancorp, Inc. acquisition. See Note 3 , " Acquisitions ," for additional detail regarding transactions completed in 2018 and 2017. The Company's other intangible assets consist of core deposit intangibles and trust department customer relationship intangibles, which are being amortized over their estimated useful lives. Other intangible assets are subject to impairment testing when events or circumstances indicate that its carrying amount may not be recoverable. The increase in other intangible assets for the year ended December 31, 2018 resulted from the Northern States acquisition. The increase in other intangible assets for the year ended December 31, 2017 resulted from the Standard and Premier acquisitions. During 2018 there were no events or circumstances to indicate impairment. Other Intangible Assets (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Gross Accumulated Amortization Net Gross Accumulated Amortization Net Gross Accumulated Amortization Net Beginning balance $ 97,976 $ 40,827 $ 57,149 $ 58,959 $ 32,962 $ 25,997 $ 48,550 $ 28,280 $ 20,270 Additions 12,230 — 12,230 39,017 — 39,017 10,409 — 10,409 Amortization expense — 7,444 (7,444 ) — 7,865 (7,865 ) — 4,682 (4,682 ) Ending balance $ 110,206 $ 48,271 $ 61,935 $ 97,976 $ 40,827 $ 57,149 $ 58,959 $ 32,962 $ 25,997 Weighted-average remaining life (in years) 7.8 8.3 7.6 Estimated remaining useful lives (in years) 0.7 to 9.8 0.2 to 9.3 0.6 to 9.3 Scheduled Amortization of Other Intangible Assets (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 8,296 2020 8,246 2021 8,170 2022 8,090 2023 7,713 2024 and thereafter 21,420 Total $ 61,935

Deposits

Deposits	12 Months Ended
	Dec. 31, 2018
Deposits [Abstract]
Deposits	DEPOSITS The following table presents the Company's deposits by type. Summary of Deposits (Dollar amounts in thousands) As of December 31, 2018 2017 Demand deposits $ 3,642,989 $ 3,576,190 Savings deposits 2,053,494 2,011,999 NOW accounts 2,063,213 1,962,304 Money market deposits 1,783,512 1,856,049 Time deposits less than $100,000 1,348,664 904,882 Time deposits greater than $100,000 1,192,240 741,901 Total deposits $ 12,084,112 $ 11,053,325 The following table provides maturity information related to the Company's time deposits. Scheduled Maturities of Time Deposits (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 1,907,914 2020 535,237 2021 60,897 2022 19,380 2023 17,299 2024 and thereafter 177 Total $ 2,540,904

Borrowed Funds

Borrowed Funds	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Borrowed Funds	BORROWED FUNDS The following table summarizes the Company's borrowed funds by funding source. Summary of Borrowed Funds (Dollar amounts in thousands) As of December 31, 2018 2017 Securities sold under agreements to repurchase $ 121,079 $ 124,884 FHLB advances 785,000 590,000 Total borrowed funds $ 906,079 $ 714,884 Securities sold under agreements to repurchase are treated as financings and the obligations to repurchase securities sold are included as a liability in the Consolidated Statements of Financial Condition. Repurchase agreements are secured by U.S. treasury and agency securities which are held in third-party pledge accounts, if required. The securities underlying the agreements remain in the respective asset accounts. As of December 31, 2018 , the Company did not have amounts at risk under repurchase agreements with any individual counterparty or group of counterparties that exceeded 10% of stockholders' equity. The Bank is a member of the FHLB and has access to term financing from the FHLB. These advances are secured by designated assets that may include qualifying commercial real estate, residential and multi-family mortgages, home equity loans, and certain municipal and mortgage-backed securities. See Note 5 , " Loans ," for detail of the carrying value of loans pledged. As of December 31, 2018 , FHLB advances had fixed interest rates that range from 2.51% to 2.58% and maturity dates that range from January 2, 2019 to March 1, 2019. The Company hedges interest rates on borrowed funds using interest rate swaps through which the Company receives variable amounts and pays fixed amounts. See Note 19 " Derivative Instruments and Hedging Activities " for a detailed discussion of interest rate swaps. The following table presents short-term credit lines available for use, for which the Company did not have an outstanding balance as of December 31, 2018 and 2017 . Short-Term Credit Lines Available for Use (Dollar amounts in thousands) As of December 31, 2018 2017 FRBs Discount Window Primary Credit Program $ 881,113 $ 843,618 Available federal funds lines 684,000 667,000 Correspondent bank line of credit 50,000 50,000 On September 27, 2016, the Company entered into a loan agreement with U.S. Bank National Association providing for a $50.0 million short-term, unsecured revolving credit facility. On September 26, 2018, the Company entered into a second amendment to this credit facility, which extends the maturity to September 26, 2019. Advances will bear interest at a rate equal to one-month LIBOR plus 1.75% , adjusted on a monthly basis, and the Company must pay an unused facility fee equal to 0.35% per annum on a quarterly basis. Management may use this line of credit for general corporate purposes. As of December 31, 2018 and 2017, no amount was outstanding under the facility. None of the Company's borrowings have any related compensating balance requirements that restrict the use of Company assets.

Senior and Subordinated Debt

Senior and Subordinated Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Senior and Subordinated Debt	SENIOR AND SUBORDINATED DEBT The following table presents the Company's senior and subordinated debt by issuance. Senior and Subordinated Debt (Dollar amounts in thousands) As of December 31, Issuance Date Maturity Date Interest Rate 2018 2017 Subordinated notes September 2016 September 2026 5.875% $ 147,282 $ 146,927 Junior subordinated debentures: First Midwest Capital Trust I ("FMCT") November 2003 December 2033 6.950% 37,803 37,801 Great Lakes Statutory Trust II ("GLST II") (1) December 2005 December 2035 L+1.400% (2) 4,580 4,486 Great Lakes Statutory Trust III ("GLST III") (1) June 2007 September 2037 L+1.700% (2) 6,071 5,956 Northern States Statutory Trust I ("NSST I") (1) September 2005 September 2035 L+1.800% (2) 8,072 — Total junior subordinated debentures 56,526 48,243 Total senior and subordinated debt $ 203,808 $ 195,170 (1) The junior subordinated debentures related to GLST II, GLST III, and NSST I were assumed by the Company through acquisitions. These amounts include acquisition adjustment discounts that total $6.0 million and $4.0 million as of December 31, 2018 and 2017 , respectively. (2) The interest rates are a variable rate, based on three-month LIBOR plus 1.400% , 1.700% and $ 1.800% for GLST II, GLST III, and NSST I, respectively. Junior Subordinated Debentures FMCT, GLST II, GLST III and NSST I are Delaware statutory business trusts. These trusts were established for the purpose of issuing trust-preferred securities and lending the proceeds to the Company in return for junior subordinated debentures of the Company. The junior subordinated debentures are the sole assets of each trust. Therefore, each trust's ability to pay amounts due on the trust-preferred securities is solely dependent on the Company making payments on the related junior subordinated debentures. The trust-preferred securities are subject to mandatory redemption, in whole or in part, on repayment of the junior subordinated debentures at the stated maturity date or on redemption. The Company guarantees payments of distributions and redemptions on the trust-preferred securities on a limited basis. For regulatory capital purposes, the Tier 1 capital treatment of trust-preferred securities ended during 2018 due to asset growth, and those securities are instead treated as Tier 2 capital. The statutory trusts qualify as variable interest entities for which the Company is not the primary beneficiary. Consequently, the accounts of those entities are not consolidated in the Company's financial statements.

Material Transactions Affecting

Material Transactions Affecting Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Material Transactions Affecting Stockholders' Equity	MATERIAL TRANSACTIONS AFFECTING STOCKHOLDERS' EQUITY Issued Common Stock On October 12, 2018, the Company issued 3,310,912 shares of it $0.01 par value common stock at a price of $25.16 as part of the consideration in the Northern States acquisition. Additional information regarding the Northern States acquisition is presented in Note 3 , " Acquisitions ." On January 6, 2017, the Company issued 21,057,085 shares of its $0.01 par value common stock at a price of $25.34 as part of the consideration in the Standard acquisition. Additional information regarding the Standard acquisition is presented in Note 3 , " Acquisitions ." Authorized Common Stock On May 17, 2017, the Company's stockholders approved and adopted an amendment to the Company's Restated Certificate of Incorporation. The amendment increased the Company's authorized common stock by 100,000,000 shares. Following this amendment, the Company is now authorized to issue a total of 251,000,000 shares, including 1,000,000 shares of preferred stock, without a par value, and 250,000,000 shares of common stock, $0.01 par value per share. Quarterly Dividend on Common Shares The Company's Board of Directors (the "Board") declared cash dividends on the Company's common stock of $0.09 per share for the first quarter of 2016, and for each of the quarters through the first quarter of 2017. The Company increased the quarterly cash dividend to $0.10 per share for each of the quarters from the second quarter of 2017 through the fourth quarter of 2017. The Company increased the quarterly cash dividend to $0.11 per share for the first through the third quarters of 2018 and increased the quarterly cash dividend to $0.12 per share for the fourth quarter of 2018. Other than share-based compensation which is disclosed in Note 17 , " Share-Based Compensation ", there were no additional material transactions that affected stockholders' equity during the three years ended December 31, 2018 .

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Common Share	EARNINGS PER COMMON SHARE The table below displays the calculation of basic and diluted earnings per common share ("EPS"). Basic and Diluted EPS (Amounts in thousands, except per share data) Years Ended December 31, 2018 2017 2016 Net income $ 157,870 $ 98,387 $ 92,349 Net income applicable to non-vested restricted shares (1,312 ) (916 ) (1,043 ) Net income applicable to common shares $ 156,558 $ 97,471 $ 91,306 Weighted-average common shares outstanding: Weighted-average common shares outstanding (basic) 102,850 101,423 79,797 Dilutive effect of common stock equivalents 4 20 13 Weighted-average diluted common shares outstanding 102,854 101,443 79,810 Basic EPS $ 1.52 $ 0.96 $ 1.14 Diluted EPS 1.52 0.96 1.14 Anti-dilutive shares not included in the computation of diluted EPS (1) 27 229 494 (1) This amount represents outstanding stock options for which the exercise price is greater than the average market price of the Company's common stock. The final outstanding stock options were exercised during the first quarter of 2018.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Components of Income Tax Expense (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Current income tax expense (benefit): Federal $ 13,497 $ 93,540 $ 46,748 State (619 ) 104 790 Total 12,878 93,644 47,538 Deferred income tax expense (benefit): Federal 14,489 (12,219 ) (7,786 ) State 11,820 8,142 6,419 Total 26,309 (4,077 ) (1,367 ) Total income tax expense $ 39,187 $ 89,567 $ 46,171 Federal income tax reform was enacted on December 22, 2017. The new law enacted various changes to the federal corporate income tax, the most impactful being the reduction in the corporate tax rate to a flat 21%. In conjunction with federal income tax reform, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118") to provide guidance on the accounting for the tax law change under GAAP. SAB 118 requires that the final determination of the impacts of federal income tax reform be completed within a measurement period not to exceed one year from the date of enactment. In compliance with that mandate, the Company has completed its accounting for the impact of federal income tax reform in the fourth quarter of 2018. As of December 31, 2017, the Company's revaluation of its deferred tax assets and liabilities at the newly enacted 21% rate resulted in additional tax expense of $26.6 million . Upon further refinement of our calculations, a benefit of $8.7 million was recorded in the year ended December 31, 2018. Federal income tax expense and the related effective income tax rate are influenced by the amount of tax-exempt income derived from investment securities and BOLI in relation to pre-tax income as well as state income taxes. State income tax expense and the related effective income tax rate are driven by both the amount of state tax-exempt income in relation to pre-tax income and state tax rules for consolidated/combined reporting and sourcing of income and expense. In addition to the impacts of federal income tax reform mentioned above, the Company recognized a $2.8 million benefit in 2017 as a result of changes in Illinois income tax rates. Components of Effective Tax Rate (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Amount % of Pretax Income Amount % of Pretax Income Amount % of Pretax Income Statutory federal income tax $ 41,382 21.0 % $ 65,784 35.0 % $ 48,482 35.0 % (Decrease) increase in income taxes resulting from: Deferred tax asset revaluation (8,721 ) (4.4 ) 23,709 12.6 — — Tax-exempt income, net of interest expense disallowance (3,104 ) (1.6 ) (5,065 ) (2.7 ) (5,439 ) (3.9 ) State income tax, net of federal income tax effect 8,846 4.5 5,069 2.7 4,323 3.1 Other 784 0.4 70 0.1 (1,195 ) (0.9 ) Total $ 39,187 19.9 % $ 89,567 47.7 % $ 46,171 33.3 % The decrease in income tax expense and the effective tax rate from the years ended December 31, 2017 to 2018 was due primarily to the decrease in the applicable federal income tax rate from 35% to 21% and the 2018 recognition of $8.7 million of income tax benefits resulting from federal income tax reform, partially offset by higher pre-tax income subject to tax at statutory rates and a decrease in tax-exempt income. The increase in income tax expense and the effective tax rate from the years ended December 31, 2016 to 2017 resulted primarily from downward revaluation of deferred tax assets by $26.6 million as a result of federal income tax reform, higher pre-tax income subject to tax at statutory rates, and a decrease in tax-exempt income, partly offset by a $2.8 million benefit due to a change in the Illinois income tax rate. As of December 31, 2018 , the Company's retained earnings included an appropriation for an acquired thrift's tax bad debt reserves of approximately $5.8 million , as well as $2.5 million for both December 31, 2017 and 2016, for which no provision for federal or state income taxes has been made. If, in the future, this portion of retained earnings were distributed as a result of the liquidation of the Company or its subsidiaries, federal and state income taxes would be imposed at the then applicable rates. Differences between the amounts reported in the consolidated financial statements and the tax basis of assets and liabilities result in temporary differences for which deferred tax assets and liabilities were recorded. Deferred Tax Assets and Liabilities (Dollar amounts in thousands) As of December 31, 2018 2017 Deferred tax assets: Allowance for credit losses $ 19,591 $ 20,285 Deferred gain on sale-leaseback transaction 13,752 15,668 Federal net operating loss ("NOL") carryforwards 8,871 — Equity based compensation 3,971 3,605 State NOL carryforwards 3,293 3,384 Non-equity based compensation 2,210 897 OREO 1,460 2,089 Deferred incentives 1,382 29 Property valuation adjustments 1,214 69 AMT and other credit carryforwards 244 667 Other 8,179 12,419 Total deferred tax assets 64,167 59,112 Deferred tax liabilities: Accrued retirement benefits (8,502 ) (3,517 ) Fixed assets (7,322 ) (1,660 ) Deferred loan fees and costs (4,985 ) (4,169 ) Cancellation of indebtedness income — (641 ) Acquisition adjustments (686 ) 2,489 Other (2,823 ) (2,449 ) Total deferred tax liabilities (24,318 ) (9,947 ) Deferred tax valuation allowance — — Net deferred tax assets 39,849 49,165 Tax effect of adjustments related to other comprehensive (loss) income 20,280 15,571 Net deferred tax assets including adjustments $ 60,129 $ 64,736 NOL carryforwards available to offset future taxable income: Federal gross NOL carryforwards, begin to expire in 2028 $ 42,242 $ — Illinois gross NOL carryforwards, begin to expire in 2024 209,802 188,995 Indiana gross NOL carryforwards, begin to expire in 2025 14,260 16,174 Wisconsin gross NOL carryforwards, begin to expire in 2032 1,212 — AMT credits — 410 During the year ended December 31, 2018, the Company recorded net deferred tax assets of $17.0 million related to the Northern States acquisition. During the year ended December 31, 2017, the Company recorded net deferred tax assets of $41.5 million related to the Standard acquisition and a measurement period adjustment related to finalizing the fair values of the assets acquired and liabilities assumed in the NI Bancshares acquisition. During the years ended December 31, 2018 and 2017, the Company transferred certain loans into Real Estate Mortgage Investment Conduit trusts which are classified as loans in the financial statements and as securities for tax purposes. Net deferred tax assets are included in other assets in the accompanying Consolidated Statements of Financial Condition. Management believes that it is more likely than not that net deferred tax assets will be fully realized and no valuation allowance is required. Uncertainty in Income Taxes The Company files a U.S. federal income tax return and state income tax returns in various states. Income tax returns filed by the Company are no longer subject to examination by federal and state income tax authorities for years prior to 2015 , except for amended changes to 2014 federal and Illinois tax returns. Rollforward of Unrecognized Tax Benefits (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 16,248 $ 2,039 $ 1,408 Additions for tax positions relating to the current year 1,209 845 640 Additions for tax positions relating to prior years 582 13,389 — Reductions for tax positions relating to prior years (60 ) (25 ) (9 ) Reductions for settlements with taxing authorities (1,629 ) — — Ending balance $ 16,350 $ 16,248 $ 2,039 Interest and penalties not included above (1) : Interest (income) expense, net of tax effect, and penalties $ (21 ) $ 118 $ 49 Accrued interest and penalties, net of tax effect, at end of year 170 191 73 (1) Included in income tax expense in the Consolidated Statements of Income. The Company does not anticipate that the amount of uncertain tax positions will significantly increase or decrease in the next twelve months. Included in the balance as of December 31, 2018 , 2017 , and 2016 are tax positions totaling $13.1 million , $12.9 million and $1.4 million , respectively, which would favorably affect the Company's effective tax rate if recognized in future periods.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS Profit Sharing Plan The Company has a defined contribution retirement savings plan (the "Profit Sharing Plan") that covers qualified employees who meet certain eligibility requirements. The Profit Sharing Plan gives qualified employees the option to contribute up to 100% (including certain highly compensated employees) of their pre-tax base salary through salary deductions under Section 401(k) of the Internal Revenue Code. At the employees' direction, employee contributions are invested among a variety of investment alternatives. In addition, the Company makes a matching contribution of 4% of the eligible employee's compensation. On an annual basis, the Company automatically contributes 2% of the employee's eligible compensation regardless of voluntary contributions made by the employee. There is also a discretionary profit sharing component of the Profit Sharing Plan, which permits the Company to distribute up to 15% of the employee's compensation. The Company's matching contributions vest immediately, while the automatic and discretionary components vest over six years. Profit Sharing Plan (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Profit sharing expense (1) $ 7,803 $ 7,346 $ 6,171 Company dividends received by the Profit Sharing Plan $ 457 $ 441 $ 494 Company shares held by the Profit Sharing Plan at the end of the year: Number of shares 1,047,213 1,079,975 1,175,858 Fair value $ 20,745 $ 25,930 $ 29,667 (1) Included in retirement and other employee benefits in the Consolidated Statements of Income. Pension Plan The Company sponsors the Pension Plan which provides for retirement benefits based on years of service and compensation levels of the participants. The Pension Plan covers employees who met certain eligibility requirements and were hired before April 1, 2007, the date it was amended to eliminate new enrollment of new participants. Effective on January 1, 2014, benefit accruals were frozen under the Pension Plan. Actuarially determined pension costs are charged to current operations and included in retirement and other employee benefits in the Consolidated Statements of Income. The Company's funding policy is to contribute amounts to the Pension Plan that are sufficient to meet the minimum funding requirements of the Employee Retirement Income Security Act of 1974 plus additional amounts as the Company deems appropriate. Pension Plan Cost and Obligations (Dollar amounts in thousands) As of December 31, 2018 2017 Accumulated benefit obligation $ 58,271 $ 67,923 Change in projected benefit obligation Beginning balance $ 67,923 $ 68,959 Service cost — — Interest cost 2,031 1,712 Settlements (7,199 ) (6,271 ) Actuarial (gain) loss (3,717 ) 4,240 Benefits paid (767 ) (717 ) Ending balance $ 58,271 $ 67,923 Change in fair value of plan assets Beginning balance $ 66,159 $ 65,189 Actual return on plan assets (6,983 ) 7,958 Benefits paid (767 ) (717 ) Employer contributions 25,000 — Settlements (7,199 ) (6,271 ) Ending balance $ 76,210 $ 66,159 Funded status recognized in the Consolidated Statements of Financial Condition Noncurrent asset (liability) $ 17,939 $ (1,764 ) Amounts recognized in accumulated other comprehensive loss Prior service cost $ — $ — Net loss 29,345 25,495 Net amount recognized $ 29,345 $ 25,495 Actuarial losses included in accumulated other comprehensive loss as a percent of Accumulated benefit obligation 50.4 % 37.5 % Fair value of plan assets 38.5 % 38.5 % Amounts expected to be amortized from accumulated other comprehensive loss into net periodic benefit cost in the next fiscal year Prior service cost $ — $ — Net loss 426 561 Net amount expected to be recognized $ 426 $ 561 Weighted-average assumptions at the end of the year used to determine the actuarial present value of the projected benefit obligation Discount rate 4.10 % 3.45 % To estimate the interest cost component of the net periodic benefit expense for the Pension Plan, the Company utilizes a full yield curve approach by applying specific spot rates along the yield curve used in the determination of the benefit obligation to the relevant projected cash flows. To the extent the cumulative actuarial losses included in accumulated other comprehensive loss exceed 10% of the greater of the accumulated benefit obligation or the market-related value of the Pension Plan assets, it is the Company's policy to amortize the Pension Plan's net actuarial losses into income over the average remaining life expectancy of the Pension Plan participants. Actuarial losses included in accumulated other comprehensive loss as of December 31, 2018 exceeded 10% of the accumulated benefit obligation and the fair value of Pension Plan assets. The amortization of net actuarial losses is a component of the net periodic benefit cost. Amortization of the net actuarial losses and prior service cost included in other comprehensive (loss) income is not expected to have a material impact on the Company's future results of operations, financial position, or liquidity. Net Periodic Benefit Pension Cost (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Components of net periodic benefit cost Interest cost $ 2,031 $ 1,712 $ 1,635 Expected return on plan assets (3,820 ) (3,802 ) (4,057 ) Recognized net actuarial loss 533 591 571 Amortization of prior service cost — — — Recognized settlement loss 2,703 2,480 1,338 Net periodic cost (income) 1,447 981 (513 ) Other changes in plan assets and benefit obligations recognized as a charge to other comprehensive (loss) income Net loss for the period (7,086 ) (83 ) (3,911 ) Amortization of net loss 3,236 3,071 1,909 Total unrealized (loss) gain (3,850 ) 2,988 (2,002 ) Total recognized in net periodic pension cost and other comprehensive (loss) income $ (5,297 ) $ 2,007 $ (1,489 ) Weighted-average assumptions used to determine the net periodic cost Discount rate 3.45 % 3.86 % 3.99 % Expected return on plan assets 5.75 % 6.25 % 6.50 % Pension Plan Asset Allocation (Dollar amounts in thousands) Percentage of Plan Assets as of December 31, Target Allocation Fair Value of Plan Assets (1) 2018 2017 Asset Category Equity securities 50 - 60% $ 46,772 61 % 60 % Fixed income 30 - 48% 27,887 37 % 35 % Cash equivalents 2 - 10% 1,551 2 % 5 % Total $ 76,210 100 % 100 % (1) Additional information regarding the fair value of Pension Plan assets as of December 31, 2018 can be found in Note 21 , " Fair Value ." As of December 31, 2018, the equity securities category allocation was outside the target range due to improved market performance. Subsequent to December 31, 2018, the Pension Plan assets were rebalanced and all asset categories were within the target allocation. The expected long-term rate of return on Pension Plan assets represents the average rate of return expected to be earned over the period the benefits included in the benefit obligation are to be paid. In developing the expected rate of return, the Company considers long-term returns based on historical market data and projections of future returns for each asset category, as well as historical actual returns on the Pension Plan assets with the assistance of its independent actuarial consultant. Using this reference data, the Company develops a forward-looking return expectation for each asset category and a weighted-average expected long-term rate of return based on the target asset allocation. The investment objective of the Pension Plan is to maximize the return on Pension Plan assets over a long-term horizon to satisfy the Pension Plan obligations. In establishing its investment and asset allocation strategies, the Company considers expected returns and the volatility associated with different strategies. The investment strategies established by the Company's Retirement Plan Committee provide for growth of capital with a moderate level of volatility by investing assets according to the target allocations stated above and reallocating those assets as needed to stay within those allocations. Investments are weighted toward publicly traded securities. Investment strategies that include alternative asset classes, such as private equity hedge funds and real estate, are generally avoided. The following table presents estimated future pension benefit payments under the Pension Plan for retirees already receiving benefits and future retirees, assuming they retire and begin receiving unreduced benefits as soon as they are eligible. Estimated Future Pension Benefit Payments (Dollar amounts in thousands) Total Year ending December 31, 2019 $ 5,589 2020 5,000 2021 4,681 2022 4,978 2023 3,827 2024-2027 19,488

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION The Company maintains various equity-based compensation plans in order to grant equity awards to certain key employees and non-employee directors. Share-Based Plans First Midwest Bancorp, Inc. 2018 Stock and Incentive Plan ("2018 Stock and Incentive Plan") – In May of 2018, the Company's stockholders approved the 2018 Stock and Incentive Plan which succeeds the Omnibus Stock and Incentive Plan ("Omnibus Plan") described below, under which the Company has ceased making new awards. The Company's stockholders authorized an additional 2,000,000 shares of the Company's common stock for award under the plan, with the remaining shares eligible for issuance under the Omnibus Plan now being eligible for issuance under the 2018 Stock and Incentive Plan. The 2018 Stock and Incentive Plan allows for the grant of both incentive and non-statutory ("nonqualified") stock options, stock appreciation rights, restricted stock, restricted stock units, performance units, and performance shares to certain key employees. The Company's current equity compensation program for key employees includes restricted stock, restricted stock units, and performance shares. Both restricted stock and restricted stock unit awards vest over three years, with 50% vesting on the second anniversary of the grant date and the remaining 50% vesting on the third anniversary of the grant date, provided the employee remains employed by the Company during this period (subject to accelerated vesting under certain circumstances in the event of a change-in-control or upon certain terminations of employment, as set forth in the applicable award agreement). The fair value of the awards is determined based on the average of the high and low price of the Company's common stock on the grant date. For participants who are granted performance shares, they may earn performance shares totaling between 0% and 200% of the number of performance shares granted based on achieving certain performance metrics. Performance shares may be earned based on achieving an internal metric (core return on average tangible common equity) and an external metric (relative total shareholder return) over a three year period. Each metric is weighted at 50% of the total award opportunity. If earned, and assuming continued employment, the performance shares vest one-third on the March 15th immediately following the end of the performance period, one-third vest the following March 15th and the remaining one-third vest on the second March 15th. Beginning with awards granted in 2018, the performance shares will vest completely, to the extent earned and assuming continued employment, on the March 15th immediately following the end of the performance period. The fair value of the performance shares that are dependent on the internal metric is determined based on the average of the high and low stock price on the grant date. An estimate is made as to the number of shares expected to vest as a result of actual performance against the internal metric to determine the amount of compensation expense to be recognized, which is re-evaluated quarterly. The fair value of the performance shares that are dependent on the external metric is determined using a Monte Carlo simulation model on the grant date assuming 100% of the shares are earned and issued. The Company has not granted stock options since 2008. Through the end of 2008, certain key employees were granted nonqualified stock options. The option exercise price is the average of the high and low price of the Company's common stock on the grant date. There are no outstanding stock options as of December 31, 2018. Omnibus Stock and Incentive Plan (the "Omnibus Plan") – In 1989, the Board adopted the Omnibus Plan, which allowed for the grant of both incentive and nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, performance units, and other awards to certain key employees. Effective May 16, 2018, the Omnibus Plan has been succeeded by the 2018 Stock and Incentive Plan and the Company no longer makes awards under the Omnibus Plan. All outstanding equity awards granted prior to the approval of the 2018 Stock and Incentive Plan will continue to be governed by the Omnibus Plan. Nonemployee Directors Stock Plan (the "Directors Plan") – In 1997, the Board adopted the Directors Plan, which provided for the grant of equity awards to non-management Board members. Until 2008, only nonqualified stock options were issued under the Directors Plan. There are no outstanding stock options as of December 31, 2018. In 2008, the Company amended the Directors Plan to allow for the grant of restricted stock awards, among other items. Since 2015, non-management members receive fully vested shares of the Company's common stock rather than restricted stock. The 2018 Stock and Incentive Plan, the Omnibus Plan, and the Directors Plan, and material amendments, were submitted to and approved by the stockholders of the Company. The Company issues treasury shares to satisfy stock option exercises and the vesting of restricted stock, restricted stock units, and performance share awards. Shares of Common Stock Available Under Share-Based Plans As of December 31, 2018 Shares Authorized Shares Available For Grant 2018 Stock and Incentive Plan (1) 3,254,706 3,223,548 Directors Plan 481,250 116,532 (1) The shares of the Company's Common Stock underlying all outstanding equity awards governed by the Omnibus Plan that are canceled, forfeited, or expire will be available for issuance under the 2018 Stock and Incentive Plan. Stock Options Nonqualified Stock Option Transactions (Amounts in thousands, except per share data) Year Ended December 31, 2018 Number of Options Weighted Average Exercise Price Options outstanding beginning balance 232 $ 25.19 Exercised (42 ) 12.17 Expired (190 ) 28.10 Options outstanding ending balance — $ — Stock Option Valuation Assumptions – The Company estimates the fair value of stock options at the grant date using a Black-Scholes option-pricing model. No stock options were granted and no stock option award modifications were made during the three years ended December 31, 2018 . Restricted Stock, Restricted Stock Unit, and Performance Share Awards Restricted Stock, Restricted Stock Unit, and Performance Share Award Transactions (Amounts in thousands, except per share data) Year Ended December 31, 2018 Restricted Stock/Unit Awards Performance Shares Number of Shares/Units Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Non-vested awards beginning balance 1,053 $ 20.36 466 $ 18.16 Granted 427 24.96 133 24.96 Vested (454 ) 17.54 (97 ) 17.54 Forfeited (79 ) 22.86 (34 ) 22.86 Non-vested awards ending balance 947 $ 23.32 468 $ 19.88 In addition, non-management board members received, in the aggregate, 14,000 shares and 16,000 shares of common stock during the years ended December 31, 2018 and 2017 , respectively. Other Restricted Stock, Restricted Stock Unit, and Performance Share Award Information (Amounts in thousands, except per share data) Years Ended December 31, 2018 2017 2016 Weighted-average grant date fair value of restricted stock, restricted stock unit, and performance share awards granted during the year $ 24.96 $ 24.71 $ 17.28 Total fair value of restricted stock, restricted stock unit, and performance share awards vested during the year 10,870 13,760 12,231 Income tax benefit realized from the vesting/release of restricted stock, restricted stock unit, and performance share awards 2,970 4,007 2,529 No restricted stock, restricted stock unit, or performance share award modifications were made during the periods presented. Compensation Expense The Company recognizes share-based compensation expense based on the estimated fair value of the option or award at the grant or modification date. Share-based compensation expense is included in salaries and wages in the Consolidated Statements of Income. Effect of Recording Share-Based Compensation Expense (Dollar amounts in thousands) Years ended December 31, 2018 2017 2016 Total share-based compensation expense (1) $ 12,062 $ 11,223 $ 7,879 Income tax benefit 3,365 4,601 3,152 Share-based compensation expense, net of tax $ 8,697 $ 6,622 $ 4,727 Unrecognized compensation expense $ 13,982 $ 13,266 $ 9,990 Weighted-average amortization period remaining (in years) 1.2 1.3 1.3 (1) Comprised of restricted stock, restricted stock unit, and performance share awards expense.

Regulatory and Capital Matters

Regulatory and Capital Matters	12 Months Ended
	Dec. 31, 2018
Banking and Thrift [Abstract]
Regulatory and Capital Matters	REGULATORY AND CAPITAL MATTERS The Company and its subsidiaries are subject to various regulatory requirements that impose restrictions on cash, loans or advances, and dividends. The Bank is also required to maintain reserves against deposits. Reserves are held either in the form of vault cash or noninterest-bearing balances maintained with the FRB and are based on the average daily balances and statutory reserve ratios prescribed by the type of deposit account. Reserve balances totaling $149.2 million as of December 31, 2018 and $121.0 million as of December 31, 2017 were maintained in accordance with these requirements. Under current Federal Reserve regulations, the Bank is limited in the amount it may loan or advance to First Midwest Bancorp, Inc. on an unconsolidated basis (the "Parent Company") and its non-bank subsidiaries. Loans or advances to a single subsidiary may not exceed 10% , and loans to all subsidiaries may not exceed 20% , of the Bank's capital stock and surplus. Loans from subsidiary banks to non-bank subsidiaries, including the Parent Company, are also required to be collateralized. The principal source of cash flow for the Parent Company is dividends from the Bank. Various federal and state banking regulations and capital guidelines limit the amount of dividends that the Bank may pay to the Parent Company. Without prior regulatory approval and while maintaining its well-capitalized status, the Bank can initiate aggregate dividend payments in 2019 of $149.9 million plus its net profits for 2019 , as defined by statute, up to the date of any such dividend declaration. Future payment of dividends by the Bank depends on individual regulatory capital requirements and levels of profitability. The Company and the Bank are also subject to various capital requirements set up and administered by federal banking agencies. Under capital adequacy guidelines, the Company and the Bank must meet specific guidelines that involve quantitative measures given the risk levels of assets and certain off-balance sheet items calculated under regulatory accounting practices ("risk-weighted assets"). The capital amounts and classification are also subject to qualitative judgments by the regulators regarding components of capital and assets, risk weightings, and other factors. The Federal Reserve, the primary regulator of the Company and the Bank, establishes minimum capital requirements that must be met by the Company and the Bank. As defined in the regulations, quantitative measures established by regulation to ensure capital adequacy require the Company and the Bank to maintain minimum amounts and ratios of total capital to risk-weighted assets, Tier 1 capital to risk-weighted assets, common equity Tier 1 ("CET1") to risk-weighted assets, and Tier 1 capital to adjusted average assets. Failure to meet minimum capital requirements could result in actions by regulators that could have a material adverse effect on the Company's financial statements. As of December 31, 2018 , the Company and the Bank met all capital adequacy requirements. As of December 31, 2018 , the Bank was "well-capitalized" under the regulatory framework for prompt corrective action. There are no conditions or events since that management believes would change the Bank's classification. The following table outlines the Company's and the Bank's measures of capital as of the dates presented and the capital guidelines established by the Federal Reserve for the Company and the Bank to be categorized as adequately capitalized and the Bank to be categorized as "well-capitalized." Summary of Regulatory Capital Ratios (Dollar amounts in thousands) Actual Adequately Capitalized To Be Well-Capitalized Under Prompt Corrective Action Provisions Capital Ratio % Capital Ratio % Capital Ratio % As of December 31, 2018 Total capital to risk-weighted assets: First Midwest Bancorp, Inc. $ 1,626,489 12.62 $ 1,273,103 9.875 N/A N/A First Midwest Bank 1,463,026 11.39 1,268,662 9.875 $ 1,284,721 10.00 Tier 1 capital to risk-weighted assets: First Midwest Bancorp, Inc. 1,315,098 10.20 1,015,259 7.875 N/A N/A First Midwest Bank 1,359,607 10.58 1,011,718 7.875 1,027,777 8.00 CET1 to risk-weighted assets: First Midwest Bancorp, Inc. 1,315,432 10.20 821,876 6.375 N/A N/A First Midwest Bank 1,359,607 10.58 819,009 6.375 835,068 6.50 Tier 1 capital to average assets: First Midwest Bancorp, Inc. 1,315,098 8.90 591,293 4.000 N/A N/A First Midwest Bank 1,359,607 9.41 577,991 4.000 722,488 5.00 As of December 31, 2017 Total capital to risk-weighted assets: First Midwest Bancorp, Inc. $ 1,448,124 12.15 $ 1,102,634 9.250 N/A N/A First Midwest Bank 1,300,809 10.95 1,099,133 9.250 $ 1,188,252 10.00 Tier 1 capital to risk-weighted assets: First Midwest Bancorp, Inc. 1,204,468 10.10 864,227 7.250 N/A N/A First Midwest Bank 1,204,080 10.13 861,482 7.250 950,601 8.00 CET1 to risk-weighted assets: First Midwest Bancorp, Inc. 1,153,939 9.68 685,421 5.750 N/A N/A First Midwest Bank 1,204,080 10.13 683,245 5.750 772,364 6.50 Tier 1 capital to average assets: First Midwest Bancorp, Inc. 1,204,468 8.99 536,200 4.000 N/A N/A First Midwest Bank 1,204,080 9.10 529,147 4.000 661,434 5.00 N/A – Not applicable. In July of 2013, the Federal Reserve published final rules (the "Basel III Capital Rules") implementing the Basel III framework set forth by the Basel Committee on Banking Supervision (the "Basel Committee"). The phase-in period for the final rules began for the Company on January 1, 2015, and was completed on January 1, 2019. Under the Basel III Capital Rules, bank holding companies with less than $15 billion in consolidated assets as of December 31, 2009 are permitted to include trust-preferred securities in Additional Tier 1 Capital. During 2018, the Company surpassed $15 billion in consolidated assets as the result of both organic growth and acquisition-related activity. As a result, the Tier 1 treatment of its outstanding trust-preferred securities ended, and those securities are instead treated as Tier 2 capital. As of December 31, 2018 , the Company had $60.7 million of trust-preferred securities included in Tier 2 capital. Since full phase-in on January 1, 2019, the Basel III Capital Rules have required the Company and the Bank to maintain the following: • A minimum ratio of CET1 to risk-weighted assets of at least 4.5% , plus a 2.5% "capital conservation buffer" (resulting in a minimum ratio of CET1 to risk-weighted assets of at least 7.0% ). • A minimum ratio of Tier 1 capital to risk-weighted assets of at least 6.0% , plus the capital conservation buffer (resulting in a minimum Tier 1 capital ratio of 8.5% ). • A minimum ratio of total capital (Tier 1 capital plus Tier 2 capital) to risk-weighted assets of at least 8.0% , plus the capital conservation buffer (resulting in a minimum total capital ratio of 10.5% ). • A minimum leverage ratio of 4.0% , calculated as the ratio of Tier 1 capital to average assets. The Basel III Capital Rules also provide for a number of deductions from and adjustments to CET1 that were phased-in over a four -year period through January 1, 2019 (beginning at 40% on January 1, 2015 and an additional 20% per year thereafter). In November of 2017, the Federal Reserve issued a final rule that retains certain existing transition provisions related to deductions from and adjustments to CET1. Examples of these include the requirement that mortgage servicing rights, deferred tax assets depending on future taxable income, and significant investments in non-consolidated financial entities be deducted from CET1 to the extent that any one such category exceeds 10% of CET1 or all such categories in the aggregate exceed 15% of CET1. Under the Basel III Capital Rules, the effects of certain accumulated other comprehensive items are included for purposes of determining regulatory capital ratios; however, the Company and the Bank made a one-time permanent election to exclude these items. The Company and the Bank believe they would meet all capital adequacy requirements under the Basel III Capital Rules on a fully phased-in basis as if such requirements were currently in effect as of December 31, 2018 and 2017 . In September of 2017, the federal bank regulators proposed to revise and simplify the capital treatment for certain deferred tax assets, mortgage servicing assets, investments in non-consolidated financial entities and minority interests for banking organizations, such as the Company and the Bank, that are not subject to the advanced approaches framework. In November of 2017, the federal banking regulators revised the Basel III Rules to extend the current transitional treatment of these items for non-advanced approaches banking organizations until the September 2017 proposal is finalized. The September 2017 proposal would also change the capital treatment of certain commercial real estate loans under the standardized approach, which the Company and the Bank use to calculate their capital ratios. In December of 2017, the Basel Committee published standards that it described as the finalization of the Basel III post-crisis regulatory reforms (the standards are commonly referred to as "Basel IV"). Among other things, these standards revise the Basel Committee's standardized approach for credit risk (including the recalibration of risk weights and introducing new capital requirements for certain "unconditionally cancellable commitments," such as unused credit card lines of credit) and provide a new standardized approach for operational risk capital. Under the Basel framework, these standards will generally be effective on January 1, 2022, with an aggregate output floor phasing in through January 1, 2027. Under the current U.S. capital rules, operational risk capital requirements and a capital floor apply only to advanced approaches banking organizations, and not to the Company or the Bank. The impact of Basel IV on the Company and the Bank will depend on the manner in which it is implemented by the federal bank regulators.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES In the ordinary course of business, the Company enters into derivative transactions as part of its overall interest rate risk management strategy. The significant accounting policies related to derivative instruments and hedging activities are presented in Note 1 , " Summary of Significant Accounting Policies ." Fair Value Hedges The Company hedges the fair value of fixed rate commercial real estate loans using interest rate swaps through which the Company pays fixed amounts and receives variable amounts. These derivative contracts are designated as fair value hedges. The Company did not have any fair value hedges as of December 31, 2018 . Fair Value Hedges (Dollar amounts in thousands) As of December 31, 2017 Gross notional amount outstanding $ 5,458 Derivative liability fair value in other liabilities (101 ) Weighted-average interest rate received 3.38 % Weighted-average interest rate paid 5.96 % Weighted-average maturity (in years) 0.84 Fair value of derivative (1) $ 110 (1) This amount represents the fair value if credit risk related contingent features were triggered. Changes in the fair value of fair value hedges are recognized in other noninterest income in the Consolidated Statements of Income. Cash Flow Hedges As of December 31, 2018 , the Company hedged $1.1 billion of certain corporate variable rate loans using interest rate swaps through which the Company receives fixed amounts and pays variable amounts. The Company also hedged $1.1 billion of borrowed funds using forward starting interest rate swaps through which the Company receives variable amounts and pays fixed amounts. These transactions allow the Company to add stability to net interest income and manage its exposure to interest rate movements. Forward starting interest rate swaps totaling $740.0 million began on various dates between June of 2015 and December of 2018, and mature between June of 2019 and December of 2021. The remaining forward starting interest rate swaps totaling $400.0 million begin on various dates between April of 2019 and February of 2021 and mature between December of 2021 and February of 2023. The weighted-average fixed interest rate to be paid on these interest rate swaps that have not yet begun was 2.53% as of December 31, 2018 . These derivative contracts are designated as cash flow hedges. Cash Flow Hedges (Dollar amounts in thousands) As of December 31, 2018 2017 Gross notional amount outstanding $ 2,280,000 $ 1,960,000 Derivative asset fair value in other assets (1) 6,889 3,989 Derivative liability fair value in other liabilities (1) (11,328 ) (10,219 ) Weighted-average interest rate received 2.12 % 1.58 % Weighted-average interest rate paid 2.20 % 1.61 % Weighted-average maturity (in years) 1.53 2.25 (1) Certain cash flow hedges are transacted through a clearinghouse ("centrally cleared") and their change in fair value is settled by the counterparties to the transaction, which results in no fair value. Changes in the fair value of cash flow hedges are recorded in accumulated other comprehensive loss on an after-tax basis and are subsequently reclassified to interest income or expense in the period that the forecasted hedged item impacts earnings. As of December 31, 2018 , the Company estimates that $1.8 million will be reclassified from accumulated other comprehensive loss as a decrease to interest income over the next twelve months. Other Derivative Instruments The Company also enters into derivative transactions through capital market products with its commercial customers and simultaneously enters into an offsetting interest rate derivative transaction with third-parties. This transaction allows the Company's customers to effectively convert a variable rate loan into a fixed rate loan. Due to the offsetting nature of these transactions, the Company does not apply hedge accounting treatment. The Company's credit exposure on these derivative transactions results primarily from counterparty credit risk. The credit valuation adjustment ("CVA") is a fair value adjustment to the derivative to account for this risk. As of December 31, 2018 and 2017 , the Company's credit exposure was fully secured by the underlying collateral on customer loans and mitigated through netting arrangements with third-parties, therefore, no CVA was recorded. Capital market products income related to commercial customer derivative instruments of $7.7 million , $8.2 million , and $10.0 million was recorded in noninterest income for the years ended December 31, 2018 , 2017 , and 2016 , respectively. Other Derivative Instruments (Dollar amounts in thousands) As of December 31, 2018 2017 Gross notional amount outstanding $ 3,085,226 $ 2,665,358 Derivative asset fair value in other assets (1) 25,168 17,079 Derivative liability fair value in other liabilities (1) (17,533 ) (14,930 ) Fair value of derivative (2) 18,013 15,059 (1) Certain other derivative instruments are centrally cleared and their change in fair value is settled by the counterparties to the transaction, which resuts in no fair value. (2) This amount represents the fair value if credit risk related contingent factors were triggered. The Company occasionally enters into risk participation agreements with counterparty banks to transfer or assume a portion of the credit risk related to customer transactions. The amounts of these instruments were not material for any period presented. The Company had no other derivative instruments as of December 31, 2018 and 2017 . The Company does not enter into derivative transactions for purely speculative purposes. The following table presents the impact of derivative instruments on comprehensive income and the reclassification of gains (losses) from accumulated other comprehensive loss to net interest income for the years ended December 31, 2018 and 2017 , and 2016 . Cash Flow Hedge Accounting on Accumulated Other Comprehensive Income (Dollar amounts in thousands) Years Ended December 30, 2018 2017 2016 (Gains) losses recognized in other comprehensive income Interest rate swaps in interest income $ 18,776 $ 11,150 $ (4,674 ) Interest rate swaps in interest expense (20,500 ) (8,025 ) (1,068 ) Reclassification of (gains) losses included in net income Interest rate swaps in interest income $ 2,611 $ 5,159 $ 7,641 Interest rate swaps in interest expense (3,673 ) (3,951 ) (4,074 ) The following table presents the impact of derivative instruments on net interest income for the years ended December 31, 2018 , 2017 , and 2016 . Hedge Income (Dollar amounts in thousands) Years Ended December 30, 2018 2017 2016 Fair Value Hedges Interest rate swaps in interest income $ (92 ) $ (167 ) $ (413 ) Cash Flow Hedges Interest rate swaps in interest income 2,611 5,159 7,641 Interest rate swaps in interest expense (3,673 ) (3,951 ) (4,074 ) Total cash flow hedges (1,062 ) 1,208 3,567 Total net (losses) gains on hedges $ (1,154 ) $ 1,041 $ 3,154 Credit Risk Derivative instruments are inherently subject to credit risk, which represents the Company's risk of loss when the counterparty to a derivative contract fails to perform according to the terms of the agreement. Credit risk is managed by limiting and collateralizing the aggregate amount of net unrealized losses by transaction, monitoring the size and the maturity structure of the derivatives, and applying uniform credit standards. Company policy establishes limits on credit exposure to any single counterparty. In addition, the Company established bilateral collateral agreements with derivative counterparties that provide for exchanges of marketable securities or cash to collateralize either party's net losses above a stated minimum threshold. As of December 31, 2018 and 2017 , these collateral agreements covered 100% of the fair value of the Company's outstanding fair value hedges. Derivative assets and liabilities are presented gross, rather than net, of pledged collateral amounts. Certain derivative instruments are subject to master netting agreements with counterparties. The Company records these transactions at their gross fair values and does not offset derivative assets and liabilities in the Consolidated Statements of Financial Condition. The following table presents the fair value of the Company's derivatives and offsetting positions as of December 31, 2018 and 2017 . Fair Value of Offsetting Derivatives (Dollar amounts in thousands) As of December 31, 2018 2017 Assets Liabilities Assets Liabilities Gross amounts recognized $ 32,057 $ 28,861 $ 21,068 $ 25,250 Less: amounts offset in the Consolidated Statements of Financial Condition — — — — Net amount presented in the Consolidated Statements of Financial Condition (1) 32,057 28,861 21,068 25,250 Gross amounts not offset in the Consolidated Statements of Financial Condition: Offsetting derivative positions (11,678 ) (11,678 ) (16,880 ) (16,880 ) Cash collateral pledged (9,060 ) (3,506 ) — (8,370 ) Net credit exposure $ 11,319 $ 13,677 $ 4,188 $ — (1) Included in other assets or other liabilities in the Consolidated Statements of Financial Condition. As of December 31, 2018 and 2017 , the Company's derivative instruments generally contained provisions that require the Company's debt to remain above a certain credit rating by each of the major credit rating agencies or that the Company maintain certain capital levels. If the Company's debt were to fall below that credit rating or the Company's capital were to fall below the required levels, it would be in violation of those provisions, and the counterparties to the derivative instruments could terminate the swap transaction and demand cash settlement of the derivative instrument in an amount equal to the derivative liability fair value. As of December 31, 2018 and 2017 , the Company was in compliance with these provisions.

Commitments, Guarantees, and Co

Commitments, Guarantees, and Contingent Liabilities	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments, Guarantees, and Contingent Liabilities	COMMITMENTS, GUARANTEES, AND CONTINGENT LIABILITIES Credit Commitments and Guarantees In the normal course of business, the Company enters into a variety of financial instruments with off-balance sheet risk to meet the financing needs of its customers and to conduct lending activities, including commitments to extend credit and standby and commercial letters of credit. These instruments involve elements of credit and interest rate risk in excess of the amount recognized in the Consolidated Statements of Financial Condition. Contractual or Notional Amounts of Financial Instruments (Dollar amounts in thousands) As of December 31, 2018 2017 Commitments to extend credit: Commercial, industrial, and agricultural $ 1,729,286 $ 1,729,426 Commercial real estate 296,882 377,551 Home equity 570,553 514,973 Other commitments (1) 244,917 244,222 Total commitments to extend credit $ 2,841,638 $ 2,866,172 Letters of credit $ 112,728 $ 128,801 (1) Other commitments includes installment and overdraft protection program commitments. Commitments to extend credit are agreements to lend funds to a customer, subject to contractual terms and covenants. Commitments generally have fixed expiration dates or other termination clauses, variable interest rates, and fee requirements, when applicable. Since many of the commitments are expected to expire without being drawn, the total commitment amounts do not necessarily represent future cash flow requirements. In the event of a customer's non-performance, the Company's credit loss exposure is equal to the contractual amount of the commitments. The credit risk is essentially the same as extending loans to customers for the full contractual amount. The Company uses the same credit policies for credit commitments as its loans and minimizes exposure to credit loss through various collateral requirements. Letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third-party. Letters of credit generally are contingent on the failure of the customer to perform according to the terms of the contract with the third-party and are often issued in favor of a municipality where construction is taking place to ensure the borrower adequately completes the construction. Commercial letters of credit are issued to facilitate transactions between a customer and a third-party based on agreed upon terms. The maximum potential future payments guaranteed by the Company under letters of credit arrangements are equal to the contractual amount of the commitment. If a commitment is funded, the Company may seek recourse through the liquidation of the underlying collateral, including real estate, production plants and property, marketable securities, or receipt of cash. As a result of the sale of certain 1-4 family mortgage loans, the Company is contractually obligated to repurchase early payment default loans or loans that do not meet underwriting requirements at recorded value. In accordance with the sales agreements, there is no limitation to the maximum potential future payments or expiration of the Company's recourse obligation. There were no material loan repurchases during the years ended December 31, 2018 or 2017 . Legal Proceedings In the ordinary course of business, there were certain legal proceedings pending against the Company and its subsidiaries at December 31, 2018 . While the outcome of any legal proceeding is inherently uncertain, based on information currently available, the Company's management does not expect that any liabilities arising from pending legal matters will have a material adverse effect on the Company's business, financial condition, results of operations, or cash flows.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value	FAIR VALUE Fair value represents the amount expected to be received to sell an asset or paid to transfer a liability in its principal or most advantageous market in an orderly transaction between market participants at the measurement date. In accordance with fair value accounting guidance, the Company measures, records, and reports various types of assets and liabilities at fair value on either a recurring or non-recurring basis in the Consolidated Statements of Financial Condition. Those assets and liabilities are presented below in the sections titled "Assets and Liabilities Required to be Measured at Fair Value on a Recurring Basis" and "Assets and Liabilities Required to be Measured at Fair Value on a Non-Recurring Basis." Other assets and liabilities are not required to be measured at fair value in the Consolidated Statements of Financial Condition, but must be disclosed at fair value. See the "Fair Value Measurements of Other Financial Instruments" section of this note. Any aggregation of the estimated fair values presented in this note does not represent the value of the Company. Depending on the nature of the asset or liability, the Company uses various valuation methodologies and assumptions to estimate fair value. GAAP provides a three-tiered fair value hierarchy based on the inputs used to measure fair value. The hierarchy is defined as follows: • Level 1 – Quoted prices in active markets for identical assets or liabilities. • Level 2 – Observable inputs other than level 1 prices, such as quoted prices for similar instruments, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. • Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. These inputs require significant management judgment or estimation, some of which use model-based techniques and may be internally developed. Assets and liabilities are assigned to a level within the fair value hierarchy based on the lowest level of significant input used to measure fair value. Assets and liabilities may change levels within the fair value hierarchy due to market conditions or other circumstances. Those transfers are recognized on the date of the event that prompted the transfer. There were no transfers of assets or liabilities required to be measured at fair value on a recurring basis between levels of the fair value hierarchy during the periods presented. Assets and Liabilities Required to be Measured at Fair Value on a Recurring Basis The following table provides the fair value for assets and liabilities required to be measured at fair value on a recurring basis in the Consolidated Statements of Financial Condition by level in the fair value hierarchy. Recurring Fair Value Measurements (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets Trading securities: Money market funds $ — $ — $ — $ 1,685 $ — $ — Mutual funds — — — 18,762 — — Total trading securities (1) — — — 20,447 — — Equity securities (1) 19,658 11,148 — — — — Securities available-for-sale (1) U.S. treasury securities 37,767 — — 46,345 — — U.S. agency securities — 142,563 — — 156,847 — CMOs — 1,315,209 — — 1,095,186 — MBSs — 466,934 — — 369,543 — Municipal securities — 227,187 — — 208,991 — Corporate debt securities — 82,349 — — — — Equity securities — — — — 7,297 — Total securities available-for-sale 37,767 2,234,242 — 46,345 1,837,864 — Mortgage servicing rights ("MSRs") (2) — — 6,730 — — 5,894 Derivative assets (2) — 32,057 — — 21,068 — Liabilities Derivative liabilities (3) $ — $ 28,861 $ — $ — $ 25,250 $ — (1) As a result of recently adopted accounting guidance, equity securities are no longer presented within trading securities or securities available-for-sale for the prior period and are not presented within equity securities for the current period. For further discussion of this guidance, see Note 2 of "Notes to the Consolidated Financial Statements" in Item 8 of this Form 10-K. (2) Included in other assets in the Consolidated Statements of Financial Condition. (3) Included in other liabilities in the Consolidated Statements of Financial Condition. The following sections describe the specific valuation techniques and inputs used to measure financial assets and liabilities at fair value. Equity Securities The Company's equity securities consist primarily of community development investments and certain diversified investment securities held in a grantor trust for participants in the Company's nonqualified deferred compensation plan that are invested in money market and mutual funds. The fair value of community development investments is based on quoted prices in active markets or market prices for similar securities obtained from external pricing services or dealer market participants and is classified in level 2 in the fair value hierarchy. The fair value of the money market and mutual funds is based on quoted market prices in active exchange markets and is classified in level 1 of the fair value hierarchy. Securities Available-for-Sale The Company's securities available-for-sale are primarily fixed income instruments that are not quoted on an exchange, but may be traded in active markets. The fair values for these securities are based on quoted prices in active markets or market prices for similar securities obtained from external pricing services or dealer market participants and are classified in level 2 in the fair value hierarchy. The fair value of U.S. treasury securities is based on quoted market prices in active exchange markets and is classified in level 1 of the fair value hierarchy. Quarterly, the Company evaluates the methodologies used by its external pricing services to estimate the fair value of these securities to determine whether the valuations represent an exit price in the Company's principal markets. The Company liquidated all of its remaining CDOs during 2017. A rollforward of the carrying value of CDOs for the two years ended December 31, 2017 is presented in the following table. Carrying Value of CDOs (Dollar amounts in thousands) Years Ended December 31, 2017 2016 Beginning balance $ 33,260 $ 31,529 Additions — — Change in other comprehensive income (1) 14,421 2,337 Paydowns and sales (47,681 ) (606 ) Ending balance $ — $ 33,260 (1) Included in unrealized holding (losses) gains in the Consolidated Statements of Comprehensive Income. Mortgage Servicing Rights The Company services loans for others totaling $627.3 million and $607.0 million as of December 31, 2018 and 2017 , respectively. These loans are owned by third-parties and are not included in the Consolidated Statements of Financial Condition. The Company determines the fair value of MSRs by estimating the present value of expected future cash flows associated with the mortgage loans being serviced and classifies them in level 3 of the fair value hierarchy. The following table presents the ranges of significant, unobservable inputs used by the Company to determine the fair value of MSRs as of December 31, 2018 and 2017 . Significant Unobservable Inputs Used in the Valuation of MSRs As of December 31, 2018 2017 Prepayment speed 6.5 % - 13.5% 4.2 % - 13.1% Maturity (months) 20 - 104 6 - 92 Discount rate 9.5 % - 12.0% 9.5 % - 12.0% The impact of changes in these key inputs could result in a significantly higher or lower fair value measurement for MSRs. Significant increases in expected prepayment speeds and discount rates have negative impacts on the valuation. Higher maturity assumptions have a favorable effect on the estimated fair value. A rollforward of the carrying value of MSRs for the three years ended December 31, 2018 is presented in the following table. Carrying Value of MSRs (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 5,894 $ 6,120 $ 1,853 Additions from acquisition — — 3,092 New MSRs 1,080 673 1,263 Total gains (losses) included in earnings (1) : Changes in valuation inputs and assumptions 475 (41 ) 610 Other changes in fair value (2) (719 ) (858 ) (698 ) Ending balance (3) $ 6,730 $ 5,894 $ 6,120 Contractual servicing fees earned during the year (1) $ 1,517 $ 1,536 $ 1,312 Total amount of loans being serviced for the benefit of others at the end of the year 627,323 607,016 640,530 (1) Included in mortgage banking income in the Consolidated Statements of Income and related to assets held as of December 31, 2018 , 2017 , and 2016 . (2) Primarily represents changes in expected future cash flows over time due to payoffs and paydowns. (3) Included in other assets in the Consolidated Statements of Financial Condition. Derivative Assets and Derivative Liabilities The Company enters into interest rate swaps and derivative transactions with commercial customers. These derivative transactions are executed in the dealer market, and pricing is based on market quotes obtained from the counterparties. The market quotes were developed using market observable inputs, which primarily include LIBOR. Therefore, derivatives are classified in level 2 of the fair value hierarchy. For its derivative assets and liabilities, the Company also considers non-performance risk, including the likelihood of default by itself and its counterparties, when evaluating whether the market quotes from the counterparties are representative of an exit price. Pension Plan Assets Although Pension Plan assets are not consolidated in the Company's Consolidated Statements of Financial Condition, they are required to be measured at fair value on an annual basis. The fair value of Pension Plan assets is presented in the following table by level in the fair value hierarchy. Annual Fair Value Measurements for Pension Plan Assets (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Total Level 1 Level 2 Total Pension plan assets: Mutual funds (1) $ 27,246 $ — $ 27,246 $ 41,002 $ — $ 41,002 U.S. government and government agency securities 4,389 3,626 8,015 3,678 9,397 13,075 Corporate bonds — 10,472 10,472 — 9,171 9,171 Common stocks 26,882 — 26,882 — — — Common trust funds — 3,595 3,595 — 2,911 2,911 Total pension plan assets $ 58,517 $ 17,693 $ 76,210 $ 44,680 $ 21,479 $ 66,159 (1) Includes mutual funds, money market funds, cash, cash equivalents, and accrued interest. Mutual funds, certain U.S. government agency securities, and common stocks are based on quoted market prices in active exchange markets and classified in level 1 of the fair value hierarchy. Corporate bonds and certain U.S. government and government agency securities are valued at quoted prices from independent sources that are based on observable market trades or observable prices for similar bonds where a price for the identical bond is not observable and, therefore, are classified in level 2 of the fair value hierarchy. Common trust funds are valued at quoted redemption values on the last business day of the Pension Plan's fiscal year and are classified in level 2 of the fair value hierarchy. There were no Pension Plan assets classified in level 3 of the fair value hierarchy. Assets and Liabilities Required to be Measured at Fair Value on a Non-Recurring Basis The following table provides the fair value for each class of assets and liabilities required to be measured at fair value on a non-recurring basis in the Consolidated Statements of Financial Condition by level in the fair value hierarchy. Non-Recurring Fair Value Measurements (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Collateral-dependent impaired loans (1) $ — $ — $ 24,565 $ — $ — $ 33,240 OREO (2) — — 6,012 — — 12,340 Loans held-for-sale (3) — — 3,478 — — 21,098 Assets held-for-sale (4) — — 3,722 — — 2,208 (1) Includes impaired loans with charge-offs and impaired loans with a specific reserve during the periods presented. (2) Includes OREO with fair value adjustments subsequent to initial transfer that occurred during the periods presented. (3) Included in other assets in the Consolidated Statements of Financial Condition. (4) Included in premises, furniture, and equipment in the Consolidated Statements of Financial Condition. Collateral-Dependent Impaired Loans Certain collateral-dependent impaired loans are subject to fair value adjustments to reflect the difference between the carrying value of the loan and the value of the underlying collateral. The fair values of collateral-dependent impaired loans are primarily determined by current appraised values of the underlying collateral. Based on the age and/or type, appraisals may be adjusted in the range of 0% to 15% . In certain cases, an internal valuation may be used when the underlying collateral is located in areas where comparable sales data is limited or unavailable. Accordingly, collateral-dependent impaired loans are classified in level 3 of the fair value hierarchy. Collateral-dependent impaired loans for which the fair value is greater than the recorded investment are not measured at fair value in the Consolidated Statements of Financial Condition and are not included in this disclosure. OREO The fair value of OREO is measured using the current appraised value of the properties. In certain circumstances, a current appraisal may not be available or may not represent an accurate measurement of the property's fair value due to outdated market information or other factors. In these cases, the fair value is determined based on the lower of the (i) most recent appraised value, (ii) broker price opinion, (iii) current listing price, or (iv) signed sales contract. Given these valuation methods, OREO is classified in level 3 of the fair value hierarchy. Loans Held-for-Sale Loans held-for-sale consists of 1-4 family mortgage loans, which were originated with the intent to sell as of December 31, 2018 and 2017 . These loans were recorded in the held-for-sale category at the contract price, which approximates fair value, and, accordingly, are classified in level 3 of the fair value hierarchy. Assets Held-for-Sale As of December 31, 2018 , assets held-for-sale consists of former branches that are no longer in operation and parcels of land previously purchased for expansion. These properties are being actively marketed and were transferred into the held-for-sale category at their fair value as determined by current appraisals. Based on these valuation methods, they are classified in level 3 of the fair value hierarchy. Goodwill and Other Intangible Assets Goodwill and other intangible assets are subject to annual impairment testing, which requires a significant degree of management judgment. If the testing had resulted in impairment, the Company would have classified goodwill and other intangible assets in level 3 of the fair value hierarchy as a non-recurring fair value measurement. Additional information regarding goodwill, other intangible assets, and impairment policies can be found in Note 1 , " Summary of Significant Accounting Policies ," and Note 9 , " Goodwill and Other Intangible Assets ." Financial Instruments Not Required to be Measured at Fair Value For certain financial instruments that are not required to be measured at fair value in the Consolidated Statements of Financial Condition, the Company must disclose the estimated fair values and the level within the fair value hierarchy as shown in the following table. Fair Value Measurements of Other Financial Instruments (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Fair Value Hierarchy Carrying Fair Value Carrying Fair Value Assets Cash and due from banks 1 $ 211,189 $ 211,189 $ 192,800 $ 192,800 Interest-bearing deposits in other banks 2 78,069 78,069 153,770 153,770 Securities held-to-maturity 2 10,176 9,871 13,760 12,013 FHLB and FRB stock 2 80,302 80,302 69,708 69,708 Loans 3 11,346,668 11,052,040 10,345,397 10,059,992 Investment in BOLI 3 296,733 296,733 279,900 279,900 Accrued interest receivable 3 54,847 54,847 45,261 45,261 Other interest-earning assets 3 5 5 228 228 Liabilities Deposits 2 $ 12,084,112 $ 12,064,604 $ 11,053,325 $ 11,038,819 Borrowed funds 2 906,079 906,079 714,884 714,884 Senior and subordinated debt 2 203,808 211,207 195,170 208,666 Accrued interest payable 2 10,005 10,005 4,704 4,704 Management uses various methodologies and assumptions to determine the estimated fair values of the financial instruments in the table above. The fair value estimates are made at a discrete point in time based on relevant market information and consider management's judgments regarding future expected economic conditions, loss experience, and specific risk characteristics of the financial instruments. Loans include the FDIC indemnification asset and net loans, which consists of loans held-for-investment, acquired loans, and the allowance for loan losses. As of both December 31, 2018 and 2017, the Company estimated the fair value of lending commitments outstanding to be immaterial.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS The Company, through the Bank, makes loans to and has transactions with certain of its directors and executive officers. All of these loans and transactions were made on substantially the same terms, including interest rates and collateral requirements, for comparable transactions with unrelated persons and did not involve more than the normal risk of collectability or present unfavorable features. For the years ended December 31, 2018 and 2017 , loans to directors and executive officers were not greater than 5% of stockholders' equity.

Condensed Parent Company Financ

Condensed Parent Company Financial Statements	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Condensed Parent Company Financial Statements	CONDENSED PARENT COMPANY FINANCIAL STATEMENTS The following represents the condensed financial statements of First Midwest Bancorp, Inc., the Parent Company. Statements of Financial Condition (Parent Company only) (Dollar amounts in thousands) As of December 31, 2018 2017 Assets Cash and due from banks $ 158,026 $ 120,812 Investments in and advances to subsidiaries 2,091,158 1,952,414 Other assets 55,782 43,606 Total assets $ 2,304,966 $ 2,116,832 Liabilities and Stockholders' Equity Senior and subordinated debt $ 203,808 $ 195,170 Accrued interest payable and other liabilities 46,160 56,788 Stockholders' equity 2,054,998 1,864,874 Total liabilities and stockholders' equity $ 2,304,966 $ 2,116,832 Statements of Income (Parent Company only) (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Income Dividends from subsidiaries $ 86,095 $ 74,091 $ 86,791 Interest income 453 2,211 2,188 Securities transactions and other 280 (1,372 ) 215 Total income 86,828 74,930 89,194 Expenses Interest expense 12,708 12,428 12,477 Salaries and employee benefits 22,430 20,978 16,104 Other expenses 9,440 9,126 7,110 Total expenses 44,578 42,532 35,691 Income before income tax benefit and equity in undistributed income of subsidiaries 42,250 32,398 53,503 Income tax benefit 13,299 14,851 12,878 Income before equity in undistributed income of subsidiaries 55,549 47,249 66,381 Equity in undistributed income of subsidiaries 102,321 51,138 25,968 Net income 157,870 98,387 92,349 Net income applicable to non-vested restricted shares (1,312 ) (916 ) (1,043 ) Net income applicable to common shares $ 156,558 $ 97,471 $ 91,306 Statements of Cash Flows (Parent Company only) (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Operating Activities Net income $ 157,870 $ 98,387 $ 92,349 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed income of subsidiaries (102,321 ) (51,138 ) (25,968 ) Depreciation of premises, furniture, and equipment 42 9 2 Net securities losses — 1,523 — Share-based compensation expense 12,062 11,223 7,879 Tax benefit (expense) related to share-based compensation 258 349 (197 ) Net decrease (increase) in other assets 35,981 18,667 (75,104 ) Net (decrease) increase in other liabilities (17,942 ) (52,377 ) 74,571 Net cash provided by operating activities 85,950 26,643 73,532 Investing Activities Purchases of securities available-for-sale — — (14 ) Proceeds from sales and maturities of securities available-for-sale — 42,516 601 Purchase of premises, furniture, and equipment (61 ) (119 ) — Net cash received (paid) for acquisitions 39 (47,364 ) (14,905 ) Net cash used in investing activities (22 ) (4,967 ) (14,318 ) Financing Activities Net proceeds from the issuance of subordinated debt — — 146,484 Payments for the retirement of senior and subordinated debt — — (153,500 ) Cash dividends paid (44,293 ) (37,129 ) (29,198 ) Restricted stock activity (4,421 ) (3,952 ) (2,476 ) Net cash used in financing activities (48,714 ) (41,081 ) (38,690 ) Net increase in cash and cash equivalents 37,214 (19,405 ) 20,524 Cash and cash equivalents at beginning of year 120,812 140,217 119,693 Cash and cash equivalents at end of year $ 158,026 $ 120,812 $ 140,217 Supplemental Disclosures of Cash Flow Information: Common stock issued for acquisitions, net of issuance costs $ 83,303 $ 534,090 $ 54,896

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Nature of Operations and Basis of Presentation	Nature of Operations – First Midwest Bancorp, Inc. (the "Company") is a bank holding company that was incorporated in Delaware in 1982 and began operations on March 31, 1983. The Company is headquartered in Chicago, Illinois with operations throughout metropolitan Chicago, northwest Indiana, central and western Illinois, and eastern Iowa. The Company operates three wholly-owned subsidiaries: First Midwest Bank (the "Bank"), Catalyst Asset Holdings, LLC ("Catalyst"), and Premier Asset Management LLC ("Premier"). The Bank conducts the majority of the Company's operations, Catalyst manages certain non-performing assets of the Company, and Premier is a registered investment advisor providing advisory services to certain of the Company's wealth management clients. The Company is engaged in commercial and retail banking and offers a full range of commercial, retail, treasury management, and wealth management products and services to commercial and industrial, agricultural, commercial real estate, municipal, and consumer customers. Basis of Presentation – The accounting and reporting policies of the Company and its subsidiaries conform to U.S. generally accepted accounting principles ("GAAP") and general practices within the banking industry. The Company uses the accrual basis of accounting for financial reporting purposes.
Reclassification	Certain reclassifications were made to prior year amounts to conform to the current year presentation.
Use of Estimates	Use of Estimates – The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Although these estimates and assumptions are based on the best available information, actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation – The accompanying consolidated financial statements include the financial position and results of operations of the Company and its subsidiaries after elimination of all significant intercompany accounts and transactions. Assets held in a fiduciary or agency capacity are not assets of the Company or its subsidiaries and are not included in the consolidated financial statements.
Segment Disclosures	Segment Disclosures – The Company has one reportable segment. The Company's chief operating decision maker evaluates the operations of the Company using consolidated information for purposes of allocating resources and assessing performance. Therefore, segment disclosures are not required.
Business Combinations	Business Combinations – Business combinations are accounted for under the acquisition method of accounting. Assets acquired and liabilities assumed are recorded at their estimated fair values as of the date of acquisition, with any excess of the purchase price of the acquisition over the fair value of the identifiable net tangible and intangible assets acquired recorded as goodwill. Alternatively, a gain is recorded if the fair value of assets purchased exceeds the fair value of liabilities assumed and consideration paid. The results of operations of the acquired business are included in the Consolidated Statements of Income from the effective date of the acquisition.
Cash and Cash Equivalents	Cash and Cash Equivalents – For purposes of the Consolidated Statements of Cash Flows, management defines cash and cash equivalents to include cash and due from banks, interest-bearing deposits in other banks, and other short-term investments, if any, such as federal funds sold and securities purchased under agreements to resell.
Securities	Securities – Securities are classified as held-to-maturity, equity, or available-for-sale at the time of purchase. Securities Held-to-Maturity – Securities classified as held-to-maturity are securities for which management has the intent and ability to hold to maturity. These securities are stated at cost and adjusted for amortization of premiums and accretion of discounts over the estimated lives of the securities using the effective interest method. Equity Securities – The Company's equity securities consist primarily of community development investments and certain diversified investment securities held in a grantor trust for participants in the Company's nonqualified deferred compensation plan that are invested in money market and mutual funds. These securities are carried at fair value with changes in fair value recognized in net income. Securities Available-for-Sale – All other securities are classified as available-for-sale. Securities available-for-sale are carried at fair value with unrealized gains and losses, net of related deferred income taxes, recorded in stockholders' equity as a separate component of accumulated other comprehensive loss. The historical cost of debt securities is adjusted for amortization of premiums and accretion of discounts over the estimated life of the security using the effective interest method. Amortization of premiums and accretion of discounts are included in interest income. Purchases and sales of securities are recognized on a trade date basis. Realized securities gains or losses are reported in net securities gains (losses) in the Consolidated Statements of Income. The cost of securities sold is based on the specific identification method. On a quarterly basis, the Company individually assesses securities with unrealized losses to determine whether there were any events or circumstances indicating that an other-than-temporary impairment ("OTTI") has occurred. In evaluating OTTI, the Company considers many factors, including (i) the severity and duration of the impairment, (ii) the financial condition and near-term prospects of the issuer, including external credit ratings and recent downgrades for debt securities, (iii) its intent to hold the security until its value recovers, and (iv) the likelihood that it will be required to sell the security before a recovery in value, which may be at maturity. If management intends to sell the security or believes it is more likely than not that it will be required to sell the security prior to full recovery, an OTTI charge will be recognized through income as a realized loss and included in net securities gains (losses) in the Consolidated Statements of Income. If management does not expect to sell the security or believes it is not more likely than not that it will be required to sell the security prior to full recovery, the OTTI is separated into the amount related to credit deterioration, which is recognized through income as a realized loss, and the amount resulting from other factors, which is recognized in other comprehensive loss.
FHLB and FRB Stock	FHLB and FRB Stock – The Company, as a member of the FHLB and FRB, is required to maintain an investment in the capital stock of the FHLB and FRB. No ready market exists for these stocks, and they have no quoted market values. The stock is redeemable at par by the FHLB and FRB and is, therefore, carried at cost and periodically evaluated for impairment.
Loans	Loans – Loans held-for-investment are loans that the Company intends to hold until they are paid in full and are carried at the principal amount outstanding, including certain net deferred loan origination fees. Loan origination fees, commitment fees, and certain direct loan origination costs are deferred, and the net amount is amortized as a yield adjustment over the contractual life of the related loans or commitments and included in interest income. Fees related to letters of credit are amortized into fee income over the contractual life of the commitment. Other credit-related fees are recognized as fee income when earned. The Company's net investment in direct financing leases is included in loans and consists of future minimum lease payments and estimated residual values, net of unearned income. Interest income on loans is accrued based on principal amounts outstanding. Loans held-for-sale are carried at the lower of aggregate cost or fair value and included in other assets in the Consolidated Statements of Financial Condition.
Acquired and Covered Loans	Acquired and Covered Loans – Covered loans consist of loans acquired by the Company in Federal Deposit Insurance Corporation ("FDIC")-assisted transactions, which are covered by loss share agreements with the FDIC (the "FDIC Agreements"), under which the FDIC reimburses the Company for the majority of the losses and eligible expenses related to these assets during the coverage period. Acquired loans consist of all other loans that were acquired in business combinations that are not covered by the FDIC Agreements. Certain loans that were previously classified as covered loans are no longer covered under the FDIC Agreements, and are included in acquired loans. Covered loans and acquired loans are included within loans held-for-investment. Acquired and covered loans are separated into (i) non-purchased credit impaired ("non-PCI") and (ii) purchased credit impaired ("PCI") loans. Non-PCI loans include loans that did not have evidence of credit deterioration since origination at the acquisition date. PCI loans include loans that had evidence of credit deterioration since origination and for which it was probable at acquisition that the Company would not collect all contractually required principal and interest payments. Evidence of credit deterioration was evaluated using various indicators, such as past due and non-accrual status. Leases and revolving loans do not qualify to be accounted for as PCI loans and are accounted for as non-PCI loans. The acquisition adjustment related to non-PCI loans is amortized into interest income over the contractual life of the related loans. If an acquired non-PCI loan is renewed subsequent to the acquisition date, any remaining acquisition adjustment is accreted into interest income and the loan is considered a new loan that is no longer classified as an acquired loan. PCI loans are accounted for based on estimates of expected future cash flows. To estimate the fair value, the Company generally aggregates purchased consumer loans and commercial loans into pools of loans with common risk characteristics, such as delinquency status, credit score, and internal risk ratings. The fair values of larger balance commercial loans are estimated on an individual basis. Expected future cash flows in excess of the fair value of loans at the purchase date ("accretable yield") are recorded as interest income over the life of the loans if the timing and amount of the expected future cash flows can be reasonably estimated. The non-accretable yield represents the difference between contractually required payments and the expected future cash flows determined at acquisition. Subsequent increases in expected future cash flows are offset against the allowance for credit losses to the extent an allowance has been established or otherwise recognized as interest income prospectively. The present value of any decreases in expected future cash flows is recognized by recording a charge-off through the allowance for loan losses or providing an allowance for loan losses.
90-Days Past Due Loans	90-Days Past Due Loans – The Company's accrual of interest on loans is generally discontinued at the time the loan is 90 days past due unless the credit is sufficiently collateralized and in the process of renewal or collection.
Non-accrual Loans	Non-accrual Loans – Generally, corporate loans are placed on non-accrual status (i) when either principal or interest payments become 90 days or more past due unless the credit is sufficiently collateralized and in the process of renewal or collection, or (ii) when an individual analysis of a borrower's creditworthiness warrants a downgrade to non-accrual regardless of past due status. When a loan is placed on non-accrual status, unpaid interest credited to income in the current year is reversed, and unpaid interest accrued in prior years is charged against the allowance for loan losses. After the loan is placed on non-accrual status, all debt service payments are applied to the principal on the loan. Future interest income may only be recorded on a cash basis after recovery of principal is reasonably assured. Non-accrual loans are returned to accrual status when the financial position of the borrower and other relevant factors indicate that the Company will collect all principal and interest. Commercial loans and loans secured by real estate are charged-off when deemed uncollectible. A loss is recorded if the net realizable value of the underlying collateral is less than the outstanding principal and interest. Consumer loans that are not secured by real estate are subject to mandatory charge-off at a specified delinquency date and are usually not classified as non-accrual prior to being charged-off. Closed-end consumer loans, which include installment, consumer secured, and single payment loans, are usually charged-off no later than the end of the month in which the loan becomes 120 days past due. PCI loans are generally considered accruing loans unless reasonable estimates of the timing and amount of expected future cash flows cannot be determined. Loans without reasonable future cash flow estimates are classified as non-accrual loans, and interest income is not recognized on those loans until the timing and amount of the expected future cash flows can be reasonably determined.
Troubled Debt Restructurings (TDRs)	Troubled Debt Restructurings ("TDRs") – A restructuring is considered a TDR when (i) the borrower is experiencing financial difficulties, and (ii) the creditor grants a concession, such as forgiveness of principal, reduction of the interest rate, changes in payments, or extension of the maturity date. Loans are not classified as TDRs when the modification is short-term or results in an insignificant delay in payments. The Company's TDRs are determined on a case-by-case basis. The Company does not accrue interest on a TDR unless it believes collection of all principal and interest under the modified terms is reasonably assured. For a TDR to begin accruing interest, the borrower must demonstrate some level of past performance and the future capacity to perform under the modified terms. Generally, six months of consecutive payment performance under the restructured terms is required before a TDR is returned to accrual status. However, the period could vary depending on the individual facts and circumstances of the loan. An evaluation of the borrower's current creditworthiness is used to assess the borrower's capacity to repay the loan under the modified terms. This evaluation includes an estimate of expected future cash flows, evidence of strong financial position, and estimates of the value of collateral, if applicable. For TDRs to be removed from TDR status in the calendar year after the restructuring, the loans must (i) have an interest rate and terms that reflect market conditions at the time of restructuring, and (ii) be in compliance with the modified terms. If the loan was restructured at below market rates and terms, it continues to be separately reported as a TDR until it is paid in full or charged-off.
Impaired Loans	Impaired Loans – Impaired loans consist of corporate non-accrual loans and TDRs. A loan is considered impaired when it is probable that the Company will not collect all contractual principal and interest. With the exception of accruing TDRs, impaired loans are classified as non-accrual and are exclusive of smaller homogeneous loans, such as home equity, 1-4 family mortgages, and installment loans. Impaired loans with balances under a specified threshold are not individually evaluated for impairment. For all other impaired loans, impairment is measured by comparing the estimated value of the loan to the recorded book value. The value of collateral-dependent loans is based on the fair value of the underlying collateral, less costs to sell. The value of other loans is measured using the present value of expected future cash flows discounted at the loan's initial effective interest rate.
Allowance for Credit Losses	Allowance for Credit Losses – The allowance for credit losses is comprised of the allowance for loan losses and the reserve for unfunded commitments, and is maintained by management at a level believed adequate to absorb estimated losses inherent in the existing loan portfolio. Determination of the allowance for credit losses is subjective since it requires significant estimates and management judgment, including the amounts and timing of expected future cash flows on impaired loans, estimated losses on pools of homogeneous loans, consideration of current economic trends, and other factors. Loans deemed to be uncollectible are charged-off against the allowance for loan losses, while recoveries of amounts previously charged-off are credited to the allowance for loan losses. Additions to the allowance for loan losses are charged to expense through the provision for loan losses. The amount of provision depends on a number of factors, including net charge-off levels, loan growth, changes in the composition of the loan portfolio, and the Company's assessment of the allowance for loan losses based on the methodology discussed below. Allowance for Loan Losses – The allowance for loan losses consists of (i) specific reserves for individual loans where the recorded investment exceeds the value, (ii) an allowance based on a loss migration analysis that uses historical credit loss experience for each loan category, and (iii) an allowance based on other internal and external qualitative factors. The specific reserves component of the allowance for loan losses is based on a periodic analysis of impaired loans exceeding a fixed dollar amount. If the value of an impaired loan is less than the recorded book value, the Company either establishes a valuation allowance (i.e., a specific reserve) equal to the excess of the book value over the collateral value of the loan as a component of the allowance for loan losses or charges off the amount if it is a confirmed loss. The general reserve component is based on a loss migration analysis, which examines actual loss experience by loan category for a rolling 8-quarter period and the related internal risk rating for corporate loans. The loss migration analysis is updated quarterly primarily using actual loss experience. This component is then adjusted based on management's consideration of many internal and external qualitative factors, including: • Changes in the composition of the loan portfolio, trends in the volume of loans, and trends in delinquent and non-accrual loans that could indicate that historical trends do not reflect current conditions. • Changes in credit policies and procedures, such as underwriting standards and collection, charge-off, and recovery practices. • Changes in the experience, ability, and depth of credit management and other relevant staff. • Changes in the quality of the Company's loan review system and Board of Directors oversight. • The effect of any concentration of credit and changes in the level of concentrations, such as loan type or risk rating. • Changes in the value of the underlying collateral for collateral-dependent loans. • Changes in the national and local economy that affect the collectability of various segments of the portfolio. • The effect of other external factors, such as competition and legal and regulatory requirements, on the Company's loan portfolio. The allowance for loan losses also consists of an allowance on acquired and covered non-PCI and PCI loans. No allowance for loan losses is recorded on acquired loans at the acquisition date. Subsequent to the acquisition date, an allowance for credit losses is established as necessary to reflect credit deterioration. The acquired non-PCI allowance is based on management's evaluation of the acquired non-PCI loan portfolio giving consideration to the current portfolio balance including the remaining acquisition adjustments, maturity dates, and overall credit quality. The allowance for covered non-PCI loans is calculated in the same manner as the general reserve component based on a loss migration analysis as discussed above. The acquired and covered PCI allowance reflects the difference between the carrying value and the discounted expected future cash flows of the acquired and covered PCI loans. On a periodic basis, the adequacy of this allowance is determined through a re-estimation of expected future cash flows on all of the outstanding acquired and covered PCI loans using either a probability of default/loss given default ("PD/LGD") methodology or a specific review methodology. The PD/LGD model is a loss model that estimates expected future cash flows using a probability of default curve and loss given default estimates. Acquired non-PCI loans that have renewed subsequent to the respective acquisition dates are no longer classified as acquired loans. Instead, they are included in the general loan population and allocated an allowance based on a loss migration analysis. Reserve for Unfunded Commitments – The Company also maintains a reserve for unfunded commitments, including letters of credit, for the risk of loss inherent in these arrangements. The reserve for unfunded commitments is estimated using the loss migration analysis from the allowance for loan losses, adjusted for probabilities of future funding requirements. The reserve for unfunded commitments is included in other liabilities in the Consolidated Statements of Financial Condition. The establishment of the allowance for credit losses involves a high degree of judgment given the difficulty of assessing the factors impacting loan repayment and estimating the timing and amount of losses. While management utilizes its best judgment and information available, the adequacy of the allowance for credit losses depends on a variety of factors beyond the Company's control, including the performance of its loan portfolio, the economy, changes in interest rates and property values, and the interpretation of loan risk classifications by regulatory authorities.
OREO	OREO – OREO consists of properties acquired through foreclosure in partial or total satisfaction of defaulted loans. At initial transfer into OREO, properties are recorded at fair value, less estimated selling costs. Subsequently, OREO is carried at the lower of the cost basis or fair value, less estimated selling costs. OREO write-downs occurring at the transfer date are charged against the allowance for loan losses, establishing a new cost basis. Subsequent to the initial transfer, the carrying values of OREO may be adjusted through a valuation allowance to reflect reductions in value resulting from new appraisals, new list prices, changes in market conditions, or changes in disposition strategies. Increases in value can be recognized through a reduction in the valuation allowance, but may not exceed the established cost basis. These valuation adjustments, along with expenses related to maintenance of the properties, are included in net OREO expense in the Consolidated Statements of Income.
FDIC Indemnification Asset	FDIC Indemnification Asset – The majority of loans and OREO acquired through FDIC-assisted transactions are covered by the FDIC Agreements, under which the FDIC reimburses the Company for the majority of the losses and eligible expenses related to these assets during the coverage period. The FDIC indemnification asset represents the present value of expected future reimbursements from the FDIC. Since the indemnified items are covered loans and covered OREO, which are initially measured at fair value, the FDIC indemnification asset is also initially measured at fair value by discounting the expected future cash flows to be received from the FDIC. These expected future cash flows are estimated by multiplying estimated losses on covered PCI loans and covered OREO by the reimbursement rates in the FDIC Agreements. The balance of the FDIC indemnification asset is adjusted periodically to reflect changes in expected future cash flows. Decreases in estimated reimbursements from the FDIC are recorded prospectively through amortization and increases in estimated reimbursements from the FDIC are recognized by an increase in the carrying value of the indemnification asset. Payments from the FDIC for reimbursement of losses result in a reduction of the FDIC indemnification asset.
Depreciable Assets	Depreciable Assets – Premises, furniture, and equipment are stated at cost, less accumulated depreciation. Depreciation expense is determined by the straight-line method over the estimated useful lives of the assets. Useful lives range from 3 to 10 years for furniture and equipment and 25 to 40 years for premises. Leasehold improvements are amortized over the shorter of the life of the asset or the lease term. Gains on dispositions are included in other noninterest income and losses on dispositions are included in other noninterest expense in the Consolidated Statements of Income. Maintenance and repairs are charged to operating expenses as incurred, while improvements that extend the useful life of assets are capitalized and depreciated over the estimated remaining life. Certain assets, such as buildings and land, that the Company intends to sell and meet held-for-sale criteria are transferred into the held-for-sale category at the lower of their fair value, as determined by a current appraisal, or their recorded investment. Long-lived depreciable assets are evaluated periodically for impairment when events or changes in circumstances indicate the carrying amount may not be recoverable. Impairment exists when the undiscounted expected future cash flows of a long-lived asset are less than its carrying value. In that event, the Company recognizes a loss for the difference between the carrying amount and the estimated fair value of the asset based on a quoted market price, if applicable, or a discounted cash flow analysis. Impairment losses are recorded in other noninterest expense in the Consolidated Statements of Income.
BOLI	BOLI – BOLI represents life insurance policies on the lives of certain Company directors and officers for which the Company is the sole owner and beneficiary. These policies are recorded as an asset in the Consolidated Statements of Financial Condition at their cash surrender value ("CSV") or the current amount that could be realized if settled. The change in CSV and insurance proceeds received are included as a component of noninterest income in the Consolidated Statements of Income.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets – Goodwill represents the excess of the purchase price of the acquisition over the fair value of the net tangible and intangible assets acquired using the acquisition method of accounting. Goodwill is not amortized. Instead, impairment testing is conducted annually as of October 1 or more often if events or circumstances between annual tests indicate that there may be impairment. Impairment testing is performed using either a qualitative or quantitative approach at the reporting unit level. All of the Company's goodwill is allocated to First Midwest Bancorp, Inc., which is the Company's only applicable reporting unit for purposes of testing goodwill for impairment. Impairment testing performed using a qualitative approach assesses recent events and circumstances to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount. Qualitative factors include, but are not limited to, macroeconomic conditions, industry and market specific conditions and trends, the Company's financial performance, market capitalization, stock price, and Company-specific events relevant to the assessment. If the assessment of qualitative factors indicates that it is not more-likely-than-not that an impairment exists, no further testing is performed; otherwise, the Company would proceed with a quantitative two-step goodwill impairment test. In the first step, the Company compares its estimate of the fair value of the reporting unit, which is based on a discounted cash flow analysis, with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill of the reporting unit is not impaired and the second step is not required. If necessary, the second step compares the implied fair value of the reporting unit goodwill with the carrying amount of that goodwill. The implied fair value of goodwill is determined by assigning the value of the reporting unit to all of the assets and liabilities of that unit, including any other identifiable intangible assets. An impairment loss is recognized if the carrying amount of the reporting unit goodwill exceeds the implied fair value of goodwill. Other intangible assets represent purchased assets that lack physical substance, but can be distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged either on its own or in combination with a related contract, asset, or liability. Identified intangible assets that have a finite useful life are amortized over that life in a manner that reflects the estimated decline in the economic value of the identified intangible asset. All of the Company's other intangible assets have finite lives and are amortized over varying periods not exceeding 13 years. Intangible assets are reviewed for impairment annually or more frequently when events or circumstances indicate that its carrying amount may not be recoverable.
Wealth Management	Wealth Management – Assets held in a fiduciary or agency capacity for customers are not included in the consolidated financial statements as they are not assets of the Company or its subsidiaries. Fee income is recognized on an accrual basis and is included as a component of noninterest income in the Consolidated Statements of Income.
Derivative Financial Instruments	Derivative Financial Instruments – To provide derivative products to customers and in the ordinary course of business, the Company enters into derivative transactions as part of its overall interest rate risk management strategy to minimize significant unplanned fluctuations in earnings and expected future cash flows caused by interest rate volatility. All derivative instruments are recorded at fair value as either other assets or other liabilities in the Consolidated Statements of Financial Condition. Subsequent changes in a derivative's fair value are recognized in earnings unless specific hedge accounting criteria are met. On the date the Company enters into a derivative contract, the derivative is designated as a fair value hedge, a cash flow hedge, or a non-hedge derivative instrument. Fair value hedges are designed to mitigate exposure to changes in the fair value of an asset or liability attributable to a particular risk, such as interest rate risk. Cash flow hedges are designed to mitigate exposure to variability in expected future cash flows to be received or paid related to an asset, liability, or other type of forecasted transaction. The Company formally documents all relationships between hedging instruments and hedged items, including its risk management objective and strategy at inception. At the hedge's inception and quarterly thereafter, a formal assessment is performed to determine the effectiveness of the derivative in offsetting changes in the fair values or expected future cash flows of the hedged items in the current period and prospectively. If a derivative instrument designated as a hedge is terminated or ceases to be highly effective, hedge accounting is discontinued prospectively, and the gain or loss is amortized into earnings. For fair value hedges, the gain or loss is amortized over the remaining life of the hedged asset or liability. For cash flow hedges, the gain or loss is amortized over the same period that the forecasted hedged transactions impact earnings. If the hedged item is disposed of, any fair value adjustments are included in the gain or loss from the disposition of the hedged item. If the forecasted transaction is no longer probable, the gain or loss is included in earnings immediately. For fair value hedges, changes in the fair value of the derivative instruments, as well as changes in the fair value of the hedged item, are recognized in earnings. For cash flow hedges, the effective portion of the change in fair value of the derivative instrument is reported as a component of accumulated other comprehensive loss and is reclassified to earnings when the hedged transaction is reflected in earnings. Ineffectiveness is calculated based on the change in fair value of the hedged item compared with the change in fair value of the hedging instrument. For all types of hedges, any ineffectiveness in the hedging relationship is recognized in earnings during the period the ineffectiveness occurs.
Comprehensive Income	Comprehensive Income – Comprehensive income is the total of reported net income and other comprehensive (loss) income which includes all other revenues, expenses, gains, and losses that are not reported in net income under GAAP. The Company includes the following items, net of tax, in other comprehensive (loss) income in the Consolidated Statements of Comprehensive Income: (i) changes in unrealized gains or losses on securities available-for-sale, (ii) changes in the fair value of derivatives designated as cash flow hedges, and (iii) changes in unrecognized net pension costs related to the Company's pension plan.
Treasury Stock	Treasury Stock – Treasury stock acquired is recorded at cost and is carried as a reduction of stockholders' equity in the Consolidated Statements of Financial Condition. Treasury stock issued is valued based on the "last in, first out" inventory method. The difference between the consideration received on issuance and the carrying value is charged or credited to additional paid-in capital.
Share-Based Compensation	Share-Based Compensation – The Company recognizes share-based compensation expense based on the estimated fair value of the award at the grant or modification date over the period during which an employee is required to provide service in exchange for such award. Share-based compensation expense is included in salaries and wages in the Consolidated Statements of Income.
Income Taxes	Income Taxes – The Company files U.S. federal income tax returns and state income tax returns in various states. The provision for income taxes is based on income in the consolidated financial statements, rather than amounts reported on the Company's income tax return. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using the enacted tax rates that are expected to apply to taxable income in years in which those temporary differences are expected to be recovered or settled. A valuation allowance is established for any deferred tax asset for which recovery or settlement is not more-likely-than-not. The effect of a change in tax rates on deferred tax assets and liabilities is recognized as income or expense in the period that includes the enactment date.
Earnings per Common Share (EPS)	Earnings per Common Share – EPS is computed using the two-class method. Basic EPS is computed by dividing net income applicable to common shares by the weighted-average number of common shares outstanding during the applicable period, excluding outstanding participating securities. Participating securities include non-vested restricted stock awards and restricted stock units, which contain nonforfeitable rights to dividends or dividend equivalents. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of stock compensation using the treasury stock method.
Adopted Accounting Pronouncements and Accounting Pronouncements Pending Adoption	Adopted Accounting Pronouncements Revenue from Contracts with Customers: In May of 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09 that requires an entity to 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. In March of 2016, the FASB issued an amendment to this guidance to clarify the implementation of guidance on principal versus agent consideration. Additional amendments to clarify the implementation guidance on the identification of performance obligations and licensing were issued in April of 2016 and narrow-scope improvements and practical expedients were issued in May of 2016. The guidance is effective for annual and interim reporting periods beginning on or after December 15, 2017, and must be applied either retrospectively or using the modified retrospective approach. The Company's revenue is comprised of net interest income on financial assets and liabilities, which is excluded from the scope of this guidance, and noninterest income. The primary sources of revenue within noninterest income are service charges on deposit accounts, wealth management fees, card-based fees, and merchant servicing fees. The adoption of this guidance on January 1, 2018, using the modified retrospective approach, affected how the Company presents merchant servicing fees, merchant card expenses, card-based fees, and cardholder expenses, which are presented on a gross basis within noninterest income and noninterest expense for the prior period and are presented on a net basis within noninterest income for the current period. Total expenses of $16.1 million for the year ended December 31, 2018 were netted in noninterest income. The adoption of this guidance did not impact net income; therefore, a cumulative effect adjustment to opening retained earnings was not deemed necessary. Consistent with the modified retrospective approach, the Company did not adjust prior period amounts for the reclassification of merchant card expenses and cardholder expenses. A description of the Company's revenue streams accounted for under the scope of this guidance follows: Service charges on deposit accounts – Service charges on deposit accounts consist of account analysis fees (net fees earned on analyzed business and public checking accounts), monthly service fees, and other deposit account related fees. The Company's performance obligation for account analysis fees and monthly service fees is generally satisfied, and the related revenue recognized, over the period in which the service is provided. Other deposit account related fees are largely transactional based and, therefore, the Company's performance obligation is satisfied, and related revenue recognized, at a point in time. Payment for service charges on deposit accounts is primarily received as a direct charge to customers' accounts. As a result of the adoption of this guidance, there was no impact to the method of recognizing revenue related to service charges on deposit accounts for the year ended December 31, 2018. Wealth management fees – Wealth management fees represents quarterly fees due from wealth management customers as consideration for managing the customers' assets. Wealth management services include custody of assets, investment management, escrow services, fees for trust services and similar fiduciary activities. Revenue is recognized when our performance obligation is completed each quarter, which is generally the time that payment is received. Also included are fees received from a third-party broker-dealer as part of a revenue-sharing agreement. These fees are paid to us by the third-party on a quarterly basis and recognized ratably throughout the quarter as our performance obligation is satisfied. As a result of the adoption of this guidance, there was no impact to the method of recognizing revenue related to wealth management fees for the year ended December 31, 2018. Card-based fees, net – Card-based fees, net consists of debit and credit card interchange fees for processing transactions, as well as various fees for automated teller machine ("ATM") and point-of-sale transactions processed through the related networks. Interchange, ATM, and point-of-sale fees from cardholder transactions represent a percentage of the underlying transaction value or a flat fee and are recognized daily in connection with the transaction processing services provided to the cardholder. Card-based fees are presented net of certain contract costs associated with the debit, credit and ATM card interchange networks. As a result of the adoption of this guidance, $7.5 million of cardholder expenses are netted against card-based fees for the year ended December 31, 2018. Merchant servicing fees, net – Merchant servicing fees, net is included in other service charges, commissions, and fees in the Consolidated Statements of Income. The Company acts in an agency capacity with respect to its merchants to process their debit and credit card transactions, deriving revenue from assisting another entity in transactions with the Company's customers. Merchant servicing fees represent a percentage of the underlying net transaction volume or a flat fee and are recognized monthly. Merchant servicing fees are presented net of certain contract costs associated with the third-party merchant processor. As a result of the adoption of this guidance, $8.6 million of merchant card expenses are netted against merchant servicing fees for the year ended December 31, 2018. Amendments to Guidance on Classifying and Measuring Financial Instruments: In January of 2016, the FASB issued ASU 2016-01 that will require entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value. Any subsequent changes in fair value will be recognized in net income unless the investments qualify for a new practicability exception. Equity securities totaling $30.8 million are no longer classified as trading securities or securities available-for-sale. This guidance also requires entities to adjust the fair value disclosures for financial instruments carried at amortized cost from an entry price to an exit price. No changes were made to the guidance for classifying and measuring investments in debt securities and loans. Except as discussed above, the adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Classification of Certain Cash Receipts and Cash Payments: In August of 2016, the FASB issued ASU 2016-15 clarifying certain cash flow presentation and classification issues to reduce diversity in practice. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Income Taxes: In October of 2016, the FASB issued ASU 2016-16 that requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Clarifying the Definition of a Business: In January of 2017, the FASB issued ASU 2017-01 that clarifies the definition of a business to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The adoption of this guidance on January 1, 2018 did not impact the Company's financial condition, results of operations, or liquidity. Presentation of Defined Benefit Retirement Plan Costs: In March of 2017, the FASB issued ASU 2017-07 that changes how employers that sponsor defined pension and or other postretirement benefit plans present the net periodic benefit cost in the income statement. Employers are required to present the service cost component of the net periodic benefit cost in the same income statement line item as other employee compensation costs arising from services rendered during the period. Other components of net periodic benefit cost are required to be presented separately from the line item(s) that includes the service cost. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Share-based Payment Award Modifications: In May of 2017, the FASB issued ASU 2017-09 to reduce diversity in practice by clarifying when changes to the terms or conditions of a share-based payment award must be accounted for as a modification. The adoption of this guidance on January 1, 2018 did not materially impact the Company's financial condition, results of operations, or liquidity. Derivatives and Hedging: In August of 2017, the FASB issued ASU 2017-12 to better align the financial reporting related to hedging activities with the economic objectives of those activities and to simplify the application of current hedge accounting guidance. Entities are required to apply the guidance using a modified retrospective method as of the period of adoption. This guidance is effective for annual and interim periods beginning after December 31, 2018. Early adoption is permitted, and the Company elected to do so on January 1, 2018, which did not materially impact the Company's financial condition, results of operations, or liquidity. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income: In February of 2018, the FASB issued ASU 2018-02 that requires a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017 . Entities electing the reclassification are required to apply the guidance either at the beginning of the period of adoption or retrospectively for all periods impacted. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted and the Company elected to do so on January 1, 2018, which resulted in the reclassification of $6.8 million of stranded tax effects from accumulated other comprehensive loss to retained earnings as of the beginning of the period of adoption. Accounting Pronouncements Pending Adoption Leases: In February of 2016, the FASB issued ASU 2016-02 to increase transparency and comparability across entities for leasing arrangements. This guidance requires lessees to recognize assets and liabilities for most leases. For lessors, this guidance modifies the lease classification criteria and the accounting for sales-type and direct financing leases. In addition, this guidance clarifies criteria for the determination of whether a contract is or contains a lease. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. The Company will adopt this guidance on January 1, 2019, which will result in the recognition of right-of-use assets and an increase in the associated lease liabilities for its operating leases of approximately $145 million . The amount of right-of-use assets and associated lease liabilities recorded upon adoption will be based on the present value of future minimum lease payments, the amount of which will depend on the population of leases in effect at the date of adoption. In addition, First Midwest Bank (the "Bank") entered into a sale-leaseback transaction in 2016 that resulted in a deferred gain. Upon adoption of this guidance, the remaining deferred gain of $47.3 million after tax will be recognized immediately as a cumulative-effect adjustment to equity. As a result, the deferred gain will no longer be accreted as a reduction to lease expense in net occupancy and equipment expense in the amount of approximately $6.0 million annually. See Note 8 "Premises, Furniture, and Equipment" for additional discussion of the sale-leaseback transaction. Management expects the adoption of the guidance will materially increase assets, liabilities, and equity, but does not expect it will materially impact the Company's results of operations or liquidity. Measurement of Credit Losses on Financial Instruments: In June of 2016, the FASB issued ASU 2016-13 that will require entities to present financial assets measured at amortized cost at the net amount expected to be collected, considering an entity's current estimate of all expected credit losses. In addition, credit losses relating to available-for-sale debt securities will be required to be recorded through an allowance for credit losses, with changes in credit loss estimates recognized through current earnings. This guidance is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted, but not for periods beginning before December 15, 2018. Management is evaluating the guidance and the impact to the Company's financial condition, results of operations, or liquidity. Accounting for Goodwill Impairment: In January of 2017, the FASB issued ASU 2017-04 that simplifies the accounting for goodwill impairment for all entities. The new guidance eliminates the requirement to calculate the implied fair value of goodwill using the second step of the quantitative two-step goodwill impairment model prescribed under current accounting guidance. Under the new guidance, if a reporting unit's carrying amount exceeds its fair value, an entity will record an impairment charge based on that difference. This guidance is effective for annual and interim goodwill impairment testing dates beginning after December 15, 2019. Early adoption is permitted for annual and interim goodwill impairment testing dates after January 1, 2017. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Premium Amortization on Purchased Callable Debt Securities: In March of 2017, the FASB issued ASU 2017-08 that shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Improvements to Nonemployee Share-based Payment Accounting: In June of 2018, the FASB issued ASU 2018-07 that aligns the measurement and classification guidance for share-based payments to nonemployees with the guidance for share-based payments to employees. This guidance is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Changes to the Disclosure Requirements for Fair Value Measurement: In August of 2018, the FASB issued ASU 2018-13 that eliminates, modifies, and adds to certain fair value measurement disclosure requirements associated with the three-tiered fair value hierarchy. This guidance is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Changes to the Disclosure Requirements for Defined Benefit Plans: In August of 2018, the FASB issued ASU 2018-14 that makes minor changes and clarifications to the disclosure requirements for entities that sponsor defined benefit plans. This guidance is effective for annual and interim periods beginning after December 15, 2020. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity. Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract: In August of 2018, the FASB issued ASU 2018-15 to reduce diversity in practice by clarifying when implementation costs are required to be capitalized in a cloud computing arrangement that is a service contract. This guidance is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted. Management does not expect the adoption of this guidance will materially impact the Company's financial condition, results of operations, or liquidity.
Pension and Other Postretirement Plans	To the extent the cumulative actuarial losses included in accumulated other comprehensive loss exceed 10% of the greater of the accumulated benefit obligation or the market-related value of the Pension Plan assets, it is the Company's policy to amortize the Pension Plan's net actuarial losses into income over the average remaining life expectancy of the Pension Plan participants. Actuarial losses included in accumulated other comprehensive loss as of December 31, 2018 exceeded 10% of the accumulated benefit obligation and the fair value of Pension Plan assets. The amortization of net actuarial losses is a component of the net periodic benefit cost. Amortization of the net actuarial losses and prior service cost included in other comprehensive (loss) income is not expected to have a material impact on the Company's future results of operations, financial position, or liquidity.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of Acquisition Activity	The following table presents the assets acquired and liabilities assumed, net of the fair value adjustments, in the Northern States and Standard transactions as of the acquisition date. The assets acquired and liabilities assumed, both intangible and tangible, were recorded at their estimated fair values as of the acquisition date and have been accounted for under the acquisition method of accounting. Acquisition Activity (Dollar amounts in thousands, except share and per share data) Northern States Standard October 12, 2018 January 6, 2017 Assets Cash and due from banks and interest-bearing deposits in other banks $ 160,145 $ 102,149 Equity securities 3,915 — Securities available-for-sale 47,149 214,107 FHLB and FRB stock 554 3,247 Loans 284,924 1,762,303 OREO 2,549 8,424 Investment in BOLI 11,104 55,629 Goodwill 29,343 345,334 Other intangible assets 12,230 31,072 Premises, furniture, and equipment 7,039 56,517 Accrued interest receivable and other assets 19,717 60,278 Total assets $ 578,669 $ 2,639,060 Liabilities Noninterest-bearing deposits $ 346,714 $ 675,354 Interest-bearing deposits 116,446 1,348,520 Total deposits 463,160 2,023,874 Borrowed funds 18,218 — Senior and subordinated debt 8,038 — Accrued interest payable and other liabilities 5,950 34,471 Total liabilities 495,366 2,058,345 Consideration Paid Common stock (2018 - 3,310,912, shares issued at $25.16 per share, 2017 - 21,057,085 share issued at $25.34 per share), net of issuance costs 83,303 533,590 Cash paid — 47,125 Total consideration paid 83,303 580,715 $ 578,669 $ 2,639,060

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	A summary of the Company's securities portfolio by category and maturity is presented in the following tables. Securities Portfolio (Dollar amounts in thousands) As of December 31, 2018 2017 Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Fair Gains Losses Gains Losses Securities Available-for-Sale U.S. treasury securities $ 37,925 $ 17 $ (175 ) $ 37,767 $ 46,529 $ — $ (184 ) $ 46,345 U.S. agency securities 144,125 45 (1,607 ) 142,563 157,636 197 (986 ) 156,847 Collateralized mortgage 1,336,531 3,362 (24,684 ) 1,315,209 1,113,019 121 (17,954 ) 1,095,186 Other mortgage-backed 477,665 520 (11,251 ) 466,934 373,676 201 (4,334 ) 369,543 Municipal securities 229,600 461 (2,874 ) 227,187 209,558 693 (1,260 ) 208,991 Corporate debt securities 86,074 — (3,725 ) 82,349 — — — — Equity securities (1) — — — — 7,408 194 (305 ) 7,297 Total securities available-for-sale $ 2,311,920 $ 4,405 $ (44,316 ) $ 2,272,009 $ 1,907,826 $ 1,406 $ (25,023 ) $ 1,884,209 Securities Held-to-Maturity Municipal securities $ 10,176 $ — $ (305 ) $ 9,871 $ 13,760 $ — $ (1,747 ) $ 12,013 Equity Securities (1) $ 30,806 $ — Trading Securities (1) $ — $ 20,447 (1) As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."
Securities Available-for-Sale	A summary of the Company's securities portfolio by category and maturity is presented in the following tables. Securities Portfolio (Dollar amounts in thousands) As of December 31, 2018 2017 Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Fair Gains Losses Gains Losses Securities Available-for-Sale U.S. treasury securities $ 37,925 $ 17 $ (175 ) $ 37,767 $ 46,529 $ — $ (184 ) $ 46,345 U.S. agency securities 144,125 45 (1,607 ) 142,563 157,636 197 (986 ) 156,847 Collateralized mortgage 1,336,531 3,362 (24,684 ) 1,315,209 1,113,019 121 (17,954 ) 1,095,186 Other mortgage-backed 477,665 520 (11,251 ) 466,934 373,676 201 (4,334 ) 369,543 Municipal securities 229,600 461 (2,874 ) 227,187 209,558 693 (1,260 ) 208,991 Corporate debt securities 86,074 — (3,725 ) 82,349 — — — — Equity securities (1) — — — — 7,408 194 (305 ) 7,297 Total securities available-for-sale $ 2,311,920 $ 4,405 $ (44,316 ) $ 2,272,009 $ 1,907,826 $ 1,406 $ (25,023 ) $ 1,884,209 Securities Held-to-Maturity Municipal securities $ 10,176 $ — $ (305 ) $ 9,871 $ 13,760 $ — $ (1,747 ) $ 12,013 Equity Securities (1) $ 30,806 $ — Trading Securities (1) $ — $ 20,447 (1) As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."
Securities Held-to-Maturity	A summary of the Company's securities portfolio by category and maturity is presented in the following tables. Securities Portfolio (Dollar amounts in thousands) As of December 31, 2018 2017 Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Fair Gains Losses Gains Losses Securities Available-for-Sale U.S. treasury securities $ 37,925 $ 17 $ (175 ) $ 37,767 $ 46,529 $ — $ (184 ) $ 46,345 U.S. agency securities 144,125 45 (1,607 ) 142,563 157,636 197 (986 ) 156,847 Collateralized mortgage 1,336,531 3,362 (24,684 ) 1,315,209 1,113,019 121 (17,954 ) 1,095,186 Other mortgage-backed 477,665 520 (11,251 ) 466,934 373,676 201 (4,334 ) 369,543 Municipal securities 229,600 461 (2,874 ) 227,187 209,558 693 (1,260 ) 208,991 Corporate debt securities 86,074 — (3,725 ) 82,349 — — — — Equity securities (1) — — — — 7,408 194 (305 ) 7,297 Total securities available-for-sale $ 2,311,920 $ 4,405 $ (44,316 ) $ 2,272,009 $ 1,907,826 $ 1,406 $ (25,023 ) $ 1,884,209 Securities Held-to-Maturity Municipal securities $ 10,176 $ — $ (305 ) $ 9,871 $ 13,760 $ — $ (1,747 ) $ 12,013 Equity Securities (1) $ 30,806 $ — Trading Securities (1) $ — $ 20,447 (1) As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."
Trading Securities	A summary of the Company's securities portfolio by category and maturity is presented in the following tables. Securities Portfolio (Dollar amounts in thousands) As of December 31, 2018 2017 Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Fair Gains Losses Gains Losses Securities Available-for-Sale U.S. treasury securities $ 37,925 $ 17 $ (175 ) $ 37,767 $ 46,529 $ — $ (184 ) $ 46,345 U.S. agency securities 144,125 45 (1,607 ) 142,563 157,636 197 (986 ) 156,847 Collateralized mortgage 1,336,531 3,362 (24,684 ) 1,315,209 1,113,019 121 (17,954 ) 1,095,186 Other mortgage-backed 477,665 520 (11,251 ) 466,934 373,676 201 (4,334 ) 369,543 Municipal securities 229,600 461 (2,874 ) 227,187 209,558 693 (1,260 ) 208,991 Corporate debt securities 86,074 — (3,725 ) 82,349 — — — — Equity securities (1) — — — — 7,408 194 (305 ) 7,297 Total securities available-for-sale $ 2,311,920 $ 4,405 $ (44,316 ) $ 2,272,009 $ 1,907,826 $ 1,406 $ (25,023 ) $ 1,884,209 Securities Held-to-Maturity Municipal securities $ 10,176 $ — $ (305 ) $ 9,871 $ 13,760 $ — $ (1,747 ) $ 12,013 Equity Securities (1) $ 30,806 $ — Trading Securities (1) $ — $ 20,447 (1) As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."
Remaining Contractual Maturity of Securities	Remaining Contractual Maturity of Securities (Dollar amounts in thousands) As of December 31, 2018 Available-for-Sale Held-to-Maturity Amortized Cost Fair Value Amortized Cost Fair Value One year or less $ 113,548 $ 111,755 $ 7,580 $ 7,353 After one year to five years 176,349 173,565 2,236 2,169 After five years to ten years 207,827 204,546 360 349 After ten years — — — — Securities that do not have a single contractual maturity date 1,814,196 1,782,143 — — Total $ 2,311,920 $ 2,272,009 $ 10,176 $ 9,871
Securities Available-for-Sale (Losses) Gains	The following table presents net realized gains (losses) on securities available-for-sale for the three years ended December 31, 2018 . Securities Available-for-Sale Gains (Losses) (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Gains (losses) on sales of securities: Gross realized gains $ — $ 5,478 $ 1,589 Gross realized losses — (7,354 ) (169 ) Net realized gains (losses) on sales of securities — (1,876 ) 1,420 Non-cash impairment charges: OTTI — — — Net realized gains (losses) $ — $ (1,876 ) $ 1,420
Changes in OTTI Recognized in Earnings	The following table presents a rollforward of life-to-date OTTI recognized in earnings related to all securities available-for-sale held by the Company for the years ended December 31, 2018 , 2017 , and 2016 . Changes in OTTI Recognized in Earnings (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ — $ 23,345 $ 23,345 OTTI included in earnings (1) : Reduction for securities sales (2) — (23,345 ) — Ending balance $ — $ — $ 23,345 (1) Included in net securities gains (losses) in the Consolidated Statements of Income. (2) These reductions were driven by the sale of 11 CDOs with a carrying value of $47.7 million during the year ended December 31, 2017.
Securities in an Unrealized Loss Position	The following table presents the aggregate amount of unrealized losses and the aggregate related fair values of securities with unrealized losses as of December 31, 2018 and 2017 . Securities in an Unrealized Loss Position (Dollar amounts in thousands) Less Than 12 Months Greater Than 12 Months Total Number of Securities Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses As of December 31, 2018 Securities Available-for-Sale U.S. treasury securities 17 $ 15,894 $ 57 $ 13,886 $ 118 $ 29,780 $ 175 U.S. agency securities 74 34,263 320 93,227 1,287 127,490 1,607 CMOs 234 171,901 1,671 863,747 23,013 1,035,648 24,684 MBSs 118 135,791 1,715 284,273 9,536 420,064 11,251 Municipal securities 423 60,863 558 109,935 2,316 170,798 2,874 Corporate debt securities 16 82,349 3,725 — — 82,349 3,725 Total 882 $ 501,061 $ 8,046 $ 1,365,068 $ 36,270 $ 1,866,129 $ 44,316 Securities Held-to-Maturity Municipal securities 5 $ — $ — $ 9,871 $ 305 $ 9,871 $ 305 As of December 31, 2017 Securities Available-for-Sale U.S. treasury securities 20 $ 19,918 $ 87 $ 26,427 $ 97 $ 46,345 $ 184 U.S. agency securities 72 66,899 300 58,021 686 124,920 986 CMOs 211 365,131 3,265 633,227 14,689 998,358 17,954 MBSs 86 126,136 902 210,017 3,432 336,153 4,334 Municipal securities 265 35,500 479 81,360 781 116,860 1,260 Equity securities (1) 2 391 214 6,386 91 6,777 305 Total 656 $ 613,975 $ 5,247 $ 1,015,438 $ 19,776 $ 1,629,413 $ 25,023 Securities Held-to-Maturity Municipal securities 8 $ — $ — $ 12,013 $ 1,747 $ 12,013 $ 1,747 (1) As a result of accounting guidance adopted in 2018, equity securities are no longer presented within securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2, "Recent Accounting Pronouncements."

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Composition Of Loan Portfolio	The following table presents the Company's loans held-for-investment by class. Loan Portfolio (Dollar amounts in thousands) As of December 31, 2018 2017 Commercial and industrial $ 4,120,293 $ 3,529,914 Agricultural 430,928 430,886 Commercial real estate: Office, retail, and industrial 1,820,917 1,979,820 Multi-family 764,185 675,463 Construction 649,337 539,820 Other commercial real estate 1,361,810 1,358,515 Total commercial real estate 4,596,249 4,553,618 Total corporate loans 9,147,470 8,514,418 Home equity 851,607 827,055 1-4 family mortgages 1,017,181 774,357 Installment 430,525 321,982 Total consumer loans 2,299,313 1,923,394 Total loans $ 11,446,783 $ 10,437,812 Deferred loan fees included in total loans $ 6,715 $ 4,986 Overdrawn demand deposits included in total loans 8,583 8,587
Schedule of Financial Instruments Owned and Pledged as Collateral	The carrying value of loans that were pledged to secure liabilities as of December 31, 2018 and 2017 are presented below. Carrying Value of Loans Pledged (Dollar amounts in thousands) As of December 31 2018 2017 Loans pledged to secure: FHLB advances (blanket pledge) $ 4,443,268 $ 4,587,240 FRB's Discount Window Primary Credit Program 1,166,128 1,099,712 Total $ 5,609,396 $ 5,686,952
Schedule of Loans Sold	The following table presents loan sales for the years ended December 31, 2018 , 2017 , and 2016 . Loan Sales (Dollar amounts in thousands) As of December 31, 2018 2017 2016 Corporate loan sales Proceeds from sales $ 17,900 $ 52,974 $ 54,681 Less book value of loans sold 17,498 51,781 52,821 Net gains on corporate sales (1) 402 1,193 1,860 1-4 family mortgage loan sales Proceeds from sales 245,967 258,626 290,383 Less book value of loans sold 240,807 252,741 283,312 Net gains on 1-4 family mortgage sales (2) 5,160 5,885 7,071 Total net gains on loan sales $ 5,562 $ 7,078 $ 8,931 (1) Net gains on corporate loan sales are included in other service charges, commissions, and fees in the Consolidated Statements of Income. (2) Net gains on 1-4 family mortgage loan sales are included in mortgage banking income in the Consolidated Statements of Income.

Acquired and Covered Loans (Tab

Acquired and Covered Loans (Tables)	12 Months Ended
	Dec. 31, 2018
Transfers and Servicing [Abstract]
Acquired and Covered Loans	The following table presents acquired and covered PCI and Non-PCI loans as of December 31, 2018 and 2017 . Acquired and Covered Loans (Dollar amounts in thousands) As of December 31, 2018 2017 PCI Non-PCI Total PCI Non-PCI Total Acquired loans $ 108,049 $ 1,247,492 $ 1,355,541 $ 130,694 $ 1,512,664 $ 1,643,358 Covered loans 5,819 4,869 10,688 6,759 11,789 18,548 Total acquired and covered loans $ 113,868 $ 1,252,361 $ 1,366,229 $ 137,453 $ 1,524,453 $ 1,661,906
Changes In The FDIC Indemnification Asset	A rollforward of the carrying value of the FDIC indemnification asset for the three years ended December 31, 2018 is presented in the following table. Changes in the FDIC Indemnification Asset (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 3,314 $ 4,522 $ 3,903 Amortization (1,208 ) (1,208 ) (1,185 ) Change in expected reimbursements from the FDIC for changes in expected credit losses (237 ) (792 ) 330 Net payments to the FDIC 235 792 1,474 Ending balance $ 2,104 $ 3,314 $ 4,522
Changes In Accretable Yield For Purchased Credit Impaired Loans	Changes in the accretable yield for acquired and covered PCI loans were as follows. Changes in Accretable Yield (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 32,957 $ 19,386 $ 24,912 Additions 3,699 27,316 3,981 Accretion (12,354 ) (15,529 ) (8,063 ) Other (1) 19,423 1,784 (1,444 ) Ending balance $ 43,725 $ 32,957 $ 19,386 (1) Increases represent a rise in the expected future cash flows to be collected over the remaining estimated life of the underlying portfolio while decreases result from the resolution of certain loans occurring earlier than anticipated.

Past Due Loans, Allowance For_2

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs (Tables)	12 Months Ended
	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Past Due Financing Receivables	The following table presents an aging analysis of the Company's past due loans as of December 31, 2018 and 2017 . The aging is determined without regard to accrual status. The table also presents non-performing loans, consisting of non-accrual loans (the majority of which are past due) and loans 90 days or more past due and still accruing interest, as of each balance sheet date. Aging Analysis of Past Due Loans and Non-Performing Loans by Class (Dollar amounts in thousands) Aging Analysis (Accruing and Non-accrual) Non-performing Loans Current (1) 30-89 Days Past Due 90 Days or More Past Due Total Past Due Total Loans Non-accrual (2) 90 Days or More Past Due, Still Accruing Interest As of December 31, 2018 Commercial and industrial $ 4,085,164 $ 8,832 $ 26,297 $ 35,129 $ 4,120,293 $ 33,507 $ 422 Agricultural 428,357 940 1,631 2,571 430,928 1,564 101 Commercial real estate: Office, retail, and industrial 1,803,059 8,209 9,649 17,858 1,820,917 6,510 4,081 Multi-family 759,402 1,487 3,296 4,783 764,185 3,107 189 Construction 645,774 3,419 144 3,563 649,337 144 — Other commercial real estate 1,353,442 4,921 3,447 8,368 1,361,810 2,854 2,197 Total commercial real estate 4,561,677 18,036 16,536 34,572 4,596,249 12,615 6,467 Total corporate loans 9,075,198 27,808 44,464 72,272 9,147,470 47,686 6,990 Home equity 843,217 6,285 2,105 8,390 851,607 5,393 104 1-4 family mortgages 1,009,925 4,361 2,895 7,256 1,017,181 3,856 1,147 Installment 428,836 1,648 41 1,689 430,525 — 41 Total consumer loans 2,281,978 12,294 5,041 17,335 2,299,313 9,249 1,292 Total loans $ 11,357,176 $ 40,102 $ 49,505 $ 89,607 $ 11,446,783 $ 56,935 $ 8,282 As of December 31, 2017 Commercial and industrial $ 3,490,783 $ 34,620 $ 4,511 $ 39,131 $ 3,529,914 $ 40,580 $ 1,830 Agricultural 430,221 280 385 665 430,886 219 177 Commercial real estate: Office, retail, and industrial 1,970,564 3,156 6,100 9,256 1,979,820 11,560 345 Multi-family 672,098 3,117 248 3,365 675,463 377 20 Construction 539,043 198 579 777 539,820 209 371 Other commercial real estate 1,353,263 2,545 2,707 5,252 1,358,515 3,621 317 Total commercial real estate 4,534,968 9,016 9,634 18,650 4,553,618 15,767 1,053 Total corporate loans 8,455,972 43,916 14,530 58,446 8,514,418 56,566 3,060 Home equity 820,099 4,102 2,854 6,956 827,055 5,946 98 1-4 family mortgages 770,120 2,145 2,092 4,237 774,357 4,412 — Installment 319,178 2,407 397 2,804 321,982 — 397 Total consumer loans 1,909,397 8,654 5,343 13,997 1,923,394 10,358 495 Total loans $ 10,365,369 $ 52,570 $ 19,873 $ 72,443 $ 10,437,812 $ 66,924 $ 3,555 (1) PCI loans with an accretable yield are considered current. (2) Includes PCI loans of $58,000 and $763,000 as of December 31, 2018 and December 31, 2017 , respectively, which no longer have an accretable yield as estimates of expected future cash flows have decreased since the acquisition due to credit deterioration.
Allowance For Credit Losses On Financing Receivables	A rollforward of the allowance for credit losses by portfolio segment for the years ended December 31, 2018 , 2017 , and 2016 is presented in the table below. Allowance for Credit Losses by Portfolio Segment (Dollar amounts in thousands) Commercial, Industrial, and Agricultural Office, Retail, and Industrial Multi-family Construction Other Commercial Real Estate Consumer Reserve for Unfunded Commitments Total Allowance for Credit Losses Year Ended December 31, 2018 Beginning balance $ 55,791 $ 10,996 $ 2,534 $ 3,481 $ 6,381 $ 16,546 $ 1,000 $ 96,729 Charge-offs (36,477 ) (2,286 ) (5 ) (1 ) (410 ) (8,806 ) — (47,985 ) Recoveries 2,946 334 3 125 1,532 1,681 — 6,621 Net charge-offs (33,531 ) (1,952 ) (2 ) 124 1,122 (7,125 ) — (41,364 ) Provision for loan 41,016 (1,144 ) (68 ) (1,432 ) (2,569 ) 12,051 200 48,054 Ending Balance $ 63,276 $ 7,900 $ 2,464 $ 2,173 $ 4,934 $ 21,472 $ 1,200 $ 103,419 Year Ended December 31, 2017 Beginning balance $ 40,709 $ 17,595 $ 3,261 $ 3,444 $ 7,739 $ 13,335 $ 1,000 $ 87,083 Charge-offs (22,885 ) (190 ) — (38 ) (755 ) (6,955 ) — (30,823 ) Recoveries 4,150 2,935 39 270 244 1,541 — 9,179 Net charge-offs (18,735 ) 2,745 39 232 (511 ) (5,414 ) — (21,644 ) Provision for loan losses and other 33,817 (9,344 ) (766 ) (195 ) (847 ) 8,625 — 31,290 Ending balance $ 55,791 $ 10,996 $ 2,534 $ 3,481 $ 6,381 $ 16,546 $ 1,000 $ 96,729 Year Ended December 31, 2016 Beginning balance $ 37,074 $ 13,124 $ 2,469 $ 1,440 $ 6,109 $ 13,414 $ 1,225 $ 74,855 Charge-offs (9,982 ) (4,707 ) (307 ) (134 ) (2,932 ) (5,231 ) — (23,293 ) Recoveries 2,451 337 97 56 524 1,298 — 4,763 Net charge-offs (7,531 ) (4,370 ) (210 ) (78 ) (2,408 ) (3,933 ) — (18,530 ) Provision for loan 11,166 8,841 1,002 2,082 4,038 3,854 (225 ) 30,758 Ending balance $ 40,709 $ 17,595 $ 3,261 $ 3,444 $ 7,739 $ 13,335 $ 1,000 $ 87,083
Schedule of Loans and The Related Allowance for Credit Losses	The table below provides a breakdown of loans and the related allowance for credit losses by portfolio segment as of December 31, 2018 and 2017 . Loans and Related Allowance for Credit Losses by Portfolio Segment (Dollar amounts in thousands) Loans Allowance for Credit Losses Individually Evaluated for Impairment Collectively Evaluated for Impairment PCI Total Individually Evaluated for Impairment Collectively Evaluated for Impairment PCI Total As of December 31, 2018 Commercial, industrial, and $ 32,415 $ 4,514,349 $ 4,457 $ 4,551,221 $ 3,961 $ 58,947 $ 368 $ 63,276 Commercial real estate: Office, retail, and industrial 5,057 1,799,304 16,556 1,820,917 748 5,984 1,168 7,900 Multi-family 3,492 747,030 13,663 764,185 — 2,154 310 2,464 Construction — 644,499 4,838 649,337 — 2,019 154 2,173 Other commercial real estate 1,545 1,305,444 54,821 1,361,810 — 4,180 754 4,934 Total commercial real estate 10,094 4,496,277 89,878 4,596,249 748 14,337 2,386 17,471 Total corporate loans 42,509 9,010,626 94,335 9,147,470 4,709 73,284 2,754 80,747 Consumer — 2,279,780 19,533 2,299,313 — 20,094 1,378 21,472 Reserve for unfunded — — — — — 1,200 — 1,200 Total loans $ 42,509 $ 11,290,406 $ 113,868 $ 11,446,783 $ 4,709 $ 94,578 $ 4,132 $ 103,419 As of December 31, 2017 Commercial, industrial, and $ 38,718 $ 3,909,380 $ 12,702 $ 3,960,800 $ 10,074 $ 45,293 $ 424 $ 55,791 Commercial real estate: Office, retail, and industrial 10,810 1,954,435 14,575 1,979,820 — 9,333 1,663 10,996 Multi-family 621 660,771 14,071 675,463 — 2,436 98 2,534 Construction — 530,977 8,843 539,820 — 3,331 150 3,481 Other commercial real estate 1,468 1,291,723 65,324 1,358,515 — 5,415 966 6,381 Total commercial real estate 12,899 4,437,906 102,813 4,553,618 — 20,515 2,877 23,392 Total corporate loans 51,617 8,347,286 115,515 8,514,418 10,074 65,808 3,301 79,183 Consumer — 1,901,456 21,938 1,923,394 — 15,533 1,013 16,546 Reserve for unfunded — — — — — 1,000 — 1,000 Total loans $ 51,617 $ 10,248,742 $ 137,453 $ 10,437,812 $ 10,074 $ 82,341 $ 4,314 $ 96,729
Impaired Financing Receivables	The following table presents loans individually evaluated for impairment by class of loan as of December 31, 2018 and 2017 . PCI loans are excluded from this disclosure. Impaired Loans Individually Evaluated by Class (Dollar amounts in thousands) As of December 31, 2018 2017 Recorded Investment In Recorded Investment In Loans with No Specific Reserve Loans with a Specific Reserve Unpaid Principal Balance Specific Reserve Loans with No Specific Reserve Loans with a Specific Reserve Unpaid Principal Balance Specific Reserve Commercial and industrial $ 7,550 $ 23,349 $ 49,102 $ 3,960 $ 4,234 $ 34,484 $ 53,192 $ 10,074 Agricultural 1,318 198 3,997 1 — — — — Commercial real estate: Office, retail, and industrial 1,861 3,196 6,141 748 7,154 3,656 14,246 — Multi-family 3,492 — 3,492 — 621 — 621 — Construction — — — — — — — — Other commercial real estate 1,545 — 1,612 — 1,468 — 1,566 — Total commercial real estate 6,898 3,196 11,245 748 9,243 3,656 16,433 — Total impaired loans $ 15,766 $ 26,743 $ 64,344 $ 4,709 $ 13,477 $ 38,140 $ 69,625 $ 10,074 The following table presents the average recorded investment and interest income recognized on impaired loans by class for the years ended December 31, 2018 , 2017 , and 2016 . PCI loans are excluded from this disclosure. Average Recorded Investment and Interest Income Recognized on Impaired Loans by Class (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Average Recorded Investment Interest Income Recognized (1) Average Recorded Investment Interest Income Recognized (1) Average Interest (1) Commercial and industrial $ 33,732 $ 225 $ 33,956 $ 1,059 $ 9,178 $ 104 Agricultural 2,026 32 279 101 — — Commercial real estate: Office, retail, and industrial 8,105 892 13,106 325 12,867 291 Multi-family 2,404 66 441 28 479 11 Construction — — 7 136 63 — Other commercial real estate 2,179 406 1,615 41 2,809 86 Total commercial real estate 12,688 1,364 15,170 530 16,218 388 Total impaired loans $ 48,445 $ 1,621 $ 49,404 $ 1,690 $ 25,396 $ 492 (1) Recorded using the cash basis of accounting.
Financing Receivable Credit Quality Indicators	The following tables present credit quality indicators by class for corporate and consumer loans as of December 31, 2018 and 2017 . Corporate Credit Quality Indicators by Class (Dollar amounts in thousands) Pass Special (1)(4) Substandard (2)(4) Non-accrual (3) Total As of December 31, 2018 Commercial and industrial $ 3,952,066 $ 74,878 $ 59,842 $ 33,507 $ 4,120,293 Agricultural 407,542 10,070 11,752 1,564 430,928 Commercial real estate: Office, retail, and industrial 1,735,426 35,853 43,128 6,510 1,820,917 Multi-family 745,131 9,273 6,674 3,107 764,185 Construction 624,446 16,370 8,377 144 649,337 Other commercial real estate 1,294,128 47,736 17,092 2,854 1,361,810 Total commercial real estate 4,399,131 109,232 75,271 12,615 4,596,249 Total corporate loans $ 8,758,739 $ 194,180 $ 146,865 $ 47,686 $ 9,147,470 As of December 31, 2017 Commercial and industrial $ 3,388,133 $ 70,863 $ 30,338 $ 40,580 $ 3,529,914 Agricultural 413,946 10,989 5,732 219 430,886 Commercial real estate: Office, retail, and industrial 1,903,737 25,546 38,977 11,560 1,979,820 Multi-family 665,496 7,395 2,195 377 675,463 Construction 521,911 10,184 7,516 209 539,820 Other commercial real estate 1,304,337 29,624 20,933 3,621 1,358,515 Total commercial real estate 4,395,481 72,749 69,621 15,767 4,553,618 Total corporate loans $ 8,197,560 $ 154,601 $ 105,691 $ 56,566 $ 8,514,418 (1) Loans categorized as special mention exhibit potential weaknesses that require the close attention of management since these potential weaknesses may result in the deterioration of repayment prospects in the future. (2) Loans categorized as substandard exhibit a well-defined weakness that may jeopardize the liquidation of the debt. These loans continue to accrue interest because they are well-secured and collection of principal and interest is expected within a reasonable time. (3) Loans categorized as non-accrual exhibit a well-defined weakness that may jeopardize the liquidation of the debt or result in a loss if the deficiencies are not corrected. (4) Total special mention and substandard loans includes accruing TDRs of $630,000 as of December 31, 2018 and $657,000 as of December 31, 2017 . Consumer Credit Quality Indicators by Class (Dollar amounts in thousands) Performing Non-accrual Total As of December 31, 2018 Home equity $ 846,214 $ 5,393 $ 851,607 1-4 family mortgages 1,013,325 3,856 1,017,181 Installment 430,525 — 430,525 Total consumer loans $ 2,290,064 $ 9,249 $ 2,299,313 As of December 31, 2017 Home equity $ 821,109 $ 5,946 $ 827,055 1-4 family mortgages 769,945 4,412 774,357 Installment 321,982 — 321,982 Total consumer loans $ 1,913,036 $ 10,358 $ 1,923,394
Troubled Debt Restructurings on Financing Receivables	The table below presents TDRs by class as of December 31, 2018 and 2017 . See Note 1 , " Summary of Significant Accounting Policies ," for the accounting policy for TDRs. TDRs by Class (Dollar amounts in thousands) As of December 31, 2018 2017 Accruing Non-accrual (1) Total Accruing Non-accrual (1) Total Commercial and industrial $ 246 $ 5,994 $ 6,240 $ 264 $ 18,959 $ 19,223 Agricultural — — — — — — Commercial real estate: Office, retail, and industrial — — — — 4,236 4,236 Multi-family 557 — 557 574 149 723 Construction — — — — — — Other commercial real estate 181 — 181 192 — 192 Total commercial real estate 738 — 738 766 4,385 5,151 Total corporate loans 984 5,994 6,978 1,030 23,344 24,374 Home equity 113 327 440 86 738 824 1-4 family mortgages 769 291 1,060 680 451 1,131 Installment — — — — — — Total consumer loans 882 618 1,500 766 1,189 1,955 Total loans $ 1,866 $ 6,612 $ 8,478 $ 1,796 $ 24,533 $ 26,329 (1) These TDRs are included in non-accrual loans in the preceding tables. A rollforward of the carrying value of TDRs for the years ended December 31, 2018 , 2017 , and 2016 is presented in the following table. TDR Rollforward (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Accruing Beginning balance $ 1,796 $ 2,291 $ 2,743 Additions — 15,819 — Net payments (50 ) (1,923 ) (120 ) Returned to performing status — — — Net transfers from (to) non-accrual 120 (14,391 ) (332 ) Ending balance 1,866 1,796 2,291 Non-accrual Beginning balance 24,533 6,297 2,324 Additions 527 14,570 6,205 Net payments (14,403 ) (4,380 ) (1,072 ) Charge-offs (3,925 ) (6,345 ) (1,492 ) Transfers to OREO — — — Loans sold — — — Net transfers (to) from accruing (120 ) 14,391 332 Ending balance 6,612 24,533 6,297 Total TDRs $ 8,478 $ 26,329 $ 8,588 The following table presents a summary of loans that were restructured during the years ended December 31, 2017 , and 2016 . Loans Restructured During the Period (Dollar amounts in thousands) Number of Loans Pre-Modification Recorded Investment Funds Disbursed Interest and Escrow Capitalized Charge-offs Post-Modification Recorded Investment Year Ended December 31, 2017 Commercial and industrial 12 $ 26,733 $ 9,035 $ — $ 6,232 $ 29,536 Office, retail, and industrial 2 3,656 — — — 3,656 Total loans restructured during the period 14 $ 30,389 $ 9,035 $ — $ 6,232 $ 33,192 Year Ended December 31, 2016 Office, retail, and industrial 1 $ 5,460 $ — $ — $ 1,083 $ 4,377 Other commercial real estate 1 745 — — — 745 Total loans restructured during the period 2 $ 6,205 $ — $ — $ 1,083 $ 5,122

Premises, Furniture, and Equi_2

Premises, Furniture, and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	The following table summarizes the Company's premises, furniture, and equipment by category. Premises, Furniture, and Equipment (Dollar amounts in thousands) As of December 31, 2018 2017 Land $ 28,187 $ 30,470 Premises 122,003 123,873 Furniture and equipment 127,421 115,013 Total cost 277,611 269,356 Accumulated depreciation (148,831 ) (148,248 ) Net book value of premises, furniture, and equipment 128,780 121,108 Assets held-for-sale 3,722 2,208 Premises, furniture, and equipment, net $ 132,502 $ 123,316
Schedule of Future Minimum Lease Payments for Capital Leases	The following summary reflects the future minimum payments by year required under operating leases that have initial or remaining non-cancelable lease terms in excess of one year as of December 31, 2018 . Future Minimum Operating Lease Payments (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 15,811 2020 16,780 2021 16,976 2022 16,967 2023 17,100 2024 and thereafter 117,806 Total minimum lease payments $ 201,440
Scheduled Accretion of Operating Leases	The following table presents the remaining scheduled accretion of the intangible liability by year. Scheduled Accretion of Operating Lease Intangible (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 648 2020 648 2021 648 2022 639 2023 612 2024 and thereafter 2,745 Total accretion $ 5,940
Schedule Of Rental Expense And Income	The following table presents net operating lease expense for the years ended December 31, 2018 , 2017 , and 2016 . Net Operating Lease Expense (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Lease expense charged to operations $ 24,880 $ 18,666 $ 11,207 Accretion of operating lease intangible (1) (972 ) (1,180 ) (1,171 ) Accretion of deferred gain on sale-leaseback transaction (1) (9,126 ) (5,872 ) (1,473 ) Rental income from premises leased to others (1) (510 ) (682 ) (527 ) Net operating lease expense $ 14,272 $ 10,932 $ 8,036 (1) Included as reductions to net occupancy and equipment expense in the Consolidated Statements of Income.

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table presents changes in the carrying amount of goodwill for the years ended December 31, 2018 , 2017 , and 2016 . Changes in the Carrying Amount of Goodwill (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 697,608 $ 340,879 $ 319,007 Acquisitions 31,201 356,729 21,872 Ending balance $ 728,809 $ 697,608 $ 340,879
Schedule of Finite-Lived Intangible Assets	Other Intangible Assets (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Gross Accumulated Amortization Net Gross Accumulated Amortization Net Gross Accumulated Amortization Net Beginning balance $ 97,976 $ 40,827 $ 57,149 $ 58,959 $ 32,962 $ 25,997 $ 48,550 $ 28,280 $ 20,270 Additions 12,230 — 12,230 39,017 — 39,017 10,409 — 10,409 Amortization expense — 7,444 (7,444 ) — 7,865 (7,865 ) — 4,682 (4,682 ) Ending balance $ 110,206 $ 48,271 $ 61,935 $ 97,976 $ 40,827 $ 57,149 $ 58,959 $ 32,962 $ 25,997 Weighted-average remaining life (in years) 7.8 8.3 7.6 Estimated remaining useful lives (in years) 0.7 to 9.8 0.2 to 9.3 0.6 to 9.3
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Scheduled Amortization of Other Intangible Assets (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 8,296 2020 8,246 2021 8,170 2022 8,090 2023 7,713 2024 and thereafter 21,420 Total $ 61,935

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2018
Deposits [Abstract]
Schedule of Deposits	The following table presents the Company's deposits by type. Summary of Deposits (Dollar amounts in thousands) As of December 31, 2018 2017 Demand deposits $ 3,642,989 $ 3,576,190 Savings deposits 2,053,494 2,011,999 NOW accounts 2,063,213 1,962,304 Money market deposits 1,783,512 1,856,049 Time deposits less than $100,000 1,348,664 904,882 Time deposits greater than $100,000 1,192,240 741,901 Total deposits $ 12,084,112 $ 11,053,325
Schedule of Maturities of Time Deposits	The following table provides maturity information related to the Company's time deposits. Scheduled Maturities of Time Deposits (Dollar amounts in thousands) Total Year Ending December 31, 2019 $ 1,907,914 2020 535,237 2021 60,897 2022 19,380 2023 17,299 2024 and thereafter 177 Total $ 2,540,904

Borrowed Funds (Tables)

Borrowed Funds (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt	The following table summarizes the Company's borrowed funds by funding source. Summary of Borrowed Funds (Dollar amounts in thousands) As of December 31, 2018 2017 Securities sold under agreements to repurchase $ 121,079 $ 124,884 FHLB advances 785,000 590,000 Total borrowed funds $ 906,079 $ 714,884
Unused Short-Term Credit Lines Available for Use	The following table presents short-term credit lines available for use, for which the Company did not have an outstanding balance as of December 31, 2018 and 2017 . Short-Term Credit Lines Available for Use (Dollar amounts in thousands) As of December 31, 2018 2017 FRBs Discount Window Primary Credit Program $ 881,113 $ 843,618 Available federal funds lines 684,000 667,000 Correspondent bank line of credit 50,000 50,000

Senior and Subordinated Debt (T

Senior and Subordinated Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table presents the Company's senior and subordinated debt by issuance. Senior and Subordinated Debt (Dollar amounts in thousands) As of December 31, Issuance Date Maturity Date Interest Rate 2018 2017 Subordinated notes September 2016 September 2026 5.875% $ 147,282 $ 146,927 Junior subordinated debentures: First Midwest Capital Trust I ("FMCT") November 2003 December 2033 6.950% 37,803 37,801 Great Lakes Statutory Trust II ("GLST II") (1) December 2005 December 2035 L+1.400% (2) 4,580 4,486 Great Lakes Statutory Trust III ("GLST III") (1) June 2007 September 2037 L+1.700% (2) 6,071 5,956 Northern States Statutory Trust I ("NSST I") (1) September 2005 September 2035 L+1.800% (2) 8,072 — Total junior subordinated debentures 56,526 48,243 Total senior and subordinated debt $ 203,808 $ 195,170 (1) The junior subordinated debentures related to GLST II, GLST III, and NSST I were assumed by the Company through acquisitions. These amounts include acquisition adjustment discounts that total $6.0 million and $4.0 million as of December 31, 2018 and 2017 , respectively. (2) The interest rates are a variable rate, based on three-month LIBOR plus 1.400% , 1.700% and $ 1.800% for GLST II, GLST III, and NSST I, respectively.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The table below displays the calculation of basic and diluted earnings per common share ("EPS"). Basic and Diluted EPS (Amounts in thousands, except per share data) Years Ended December 31, 2018 2017 2016 Net income $ 157,870 $ 98,387 $ 92,349 Net income applicable to non-vested restricted shares (1,312 ) (916 ) (1,043 ) Net income applicable to common shares $ 156,558 $ 97,471 $ 91,306 Weighted-average common shares outstanding: Weighted-average common shares outstanding (basic) 102,850 101,423 79,797 Dilutive effect of common stock equivalents 4 20 13 Weighted-average diluted common shares outstanding 102,854 101,443 79,810 Basic EPS $ 1.52 $ 0.96 $ 1.14 Diluted EPS 1.52 0.96 1.14 Anti-dilutive shares not included in the computation of diluted EPS (1) 27 229 494 (1) This amount represents outstanding stock options for which the exercise price is greater than the average market price of the Company's common stock. The final outstanding stock options were exercised during the first quarter of 2018.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Components of Income Tax Expense (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Current income tax expense (benefit): Federal $ 13,497 $ 93,540 $ 46,748 State (619 ) 104 790 Total 12,878 93,644 47,538 Deferred income tax expense (benefit): Federal 14,489 (12,219 ) (7,786 ) State 11,820 8,142 6,419 Total 26,309 (4,077 ) (1,367 ) Total income tax expense $ 39,187 $ 89,567 $ 46,171
Schedule of Effective Income Tax Rate Reconciliation	Components of Effective Tax Rate (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Amount % of Pretax Income Amount % of Pretax Income Amount % of Pretax Income Statutory federal income tax $ 41,382 21.0 % $ 65,784 35.0 % $ 48,482 35.0 % (Decrease) increase in income taxes resulting from: Deferred tax asset revaluation (8,721 ) (4.4 ) 23,709 12.6 — — Tax-exempt income, net of interest expense disallowance (3,104 ) (1.6 ) (5,065 ) (2.7 ) (5,439 ) (3.9 ) State income tax, net of federal income tax effect 8,846 4.5 5,069 2.7 4,323 3.1 Other 784 0.4 70 0.1 (1,195 ) (0.9 ) Total $ 39,187 19.9 % $ 89,567 47.7 % $ 46,171 33.3 %
Schedule of Deferred Tax Assets and Liabilities	Deferred Tax Assets and Liabilities (Dollar amounts in thousands) As of December 31, 2018 2017 Deferred tax assets: Allowance for credit losses $ 19,591 $ 20,285 Deferred gain on sale-leaseback transaction 13,752 15,668 Federal net operating loss ("NOL") carryforwards 8,871 — Equity based compensation 3,971 3,605 State NOL carryforwards 3,293 3,384 Non-equity based compensation 2,210 897 OREO 1,460 2,089 Deferred incentives 1,382 29 Property valuation adjustments 1,214 69 AMT and other credit carryforwards 244 667 Other 8,179 12,419 Total deferred tax assets 64,167 59,112 Deferred tax liabilities: Accrued retirement benefits (8,502 ) (3,517 ) Fixed assets (7,322 ) (1,660 ) Deferred loan fees and costs (4,985 ) (4,169 ) Cancellation of indebtedness income — (641 ) Acquisition adjustments (686 ) 2,489 Other (2,823 ) (2,449 ) Total deferred tax liabilities (24,318 ) (9,947 ) Deferred tax valuation allowance — — Net deferred tax assets 39,849 49,165 Tax effect of adjustments related to other comprehensive (loss) income 20,280 15,571 Net deferred tax assets including adjustments $ 60,129 $ 64,736 NOL carryforwards available to offset future taxable income: Federal gross NOL carryforwards, begin to expire in 2028 $ 42,242 $ — Illinois gross NOL carryforwards, begin to expire in 2024 209,802 188,995 Indiana gross NOL carryforwards, begin to expire in 2025 14,260 16,174 Wisconsin gross NOL carryforwards, begin to expire in 2032 1,212 — AMT credits — 410
Summary of Income Tax Contingencies	Rollforward of Unrecognized Tax Benefits (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 16,248 $ 2,039 $ 1,408 Additions for tax positions relating to the current year 1,209 845 640 Additions for tax positions relating to prior years 582 13,389 — Reductions for tax positions relating to prior years (60 ) (25 ) (9 ) Reductions for settlements with taxing authorities (1,629 ) — — Ending balance $ 16,350 $ 16,248 $ 2,039 Interest and penalties not included above (1) : Interest (income) expense, net of tax effect, and penalties $ (21 ) $ 118 $ 49 Accrued interest and penalties, net of tax effect, at end of year 170 191 73 (1) Included in income tax expense in the Consolidated Statements of Income.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Profit Sharing Plan	Profit Sharing Plan (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Profit sharing expense (1) $ 7,803 $ 7,346 $ 6,171 Company dividends received by the Profit Sharing Plan $ 457 $ 441 $ 494 Company shares held by the Profit Sharing Plan at the end of the year: Number of shares 1,047,213 1,079,975 1,175,858 Fair value $ 20,745 $ 25,930 $ 29,667 (1) Included in retirement and other employee benefits in the Consolidated Statements of Income.
Schedule of Pension Plan Cost and Obligation	Pension Plan Cost and Obligations (Dollar amounts in thousands) As of December 31, 2018 2017 Accumulated benefit obligation $ 58,271 $ 67,923 Change in projected benefit obligation Beginning balance $ 67,923 $ 68,959 Service cost — — Interest cost 2,031 1,712 Settlements (7,199 ) (6,271 ) Actuarial (gain) loss (3,717 ) 4,240 Benefits paid (767 ) (717 ) Ending balance $ 58,271 $ 67,923 Change in fair value of plan assets Beginning balance $ 66,159 $ 65,189 Actual return on plan assets (6,983 ) 7,958 Benefits paid (767 ) (717 ) Employer contributions 25,000 — Settlements (7,199 ) (6,271 ) Ending balance $ 76,210 $ 66,159 Funded status recognized in the Consolidated Statements of Financial Condition Noncurrent asset (liability) $ 17,939 $ (1,764 ) Amounts recognized in accumulated other comprehensive loss Prior service cost $ — $ — Net loss 29,345 25,495 Net amount recognized $ 29,345 $ 25,495 Actuarial losses included in accumulated other comprehensive loss as a percent of Accumulated benefit obligation 50.4 % 37.5 % Fair value of plan assets 38.5 % 38.5 % Amounts expected to be amortized from accumulated other comprehensive loss into net periodic benefit cost in the next fiscal year Prior service cost $ — $ — Net loss 426 561 Net amount expected to be recognized $ 426 $ 561 Weighted-average assumptions at the end of the year used to determine the actuarial present value of the projected benefit obligation Discount rate 4.10 % 3.45 %
Schedule of Net Periodic Benefit Pension Costs	Net Periodic Benefit Pension Cost (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Components of net periodic benefit cost Interest cost $ 2,031 $ 1,712 $ 1,635 Expected return on plan assets (3,820 ) (3,802 ) (4,057 ) Recognized net actuarial loss 533 591 571 Amortization of prior service cost — — — Recognized settlement loss 2,703 2,480 1,338 Net periodic cost (income) 1,447 981 (513 ) Other changes in plan assets and benefit obligations recognized as a charge to other comprehensive (loss) income Net loss for the period (7,086 ) (83 ) (3,911 ) Amortization of net loss 3,236 3,071 1,909 Total unrealized (loss) gain (3,850 ) 2,988 (2,002 ) Total recognized in net periodic pension cost and other comprehensive (loss) income $ (5,297 ) $ 2,007 $ (1,489 ) Weighted-average assumptions used to determine the net periodic cost Discount rate 3.45 % 3.86 % 3.99 % Expected return on plan assets 5.75 % 6.25 % 6.50 %
Schedule of Pension Plan Asset Allocation	Pension Plan Asset Allocation (Dollar amounts in thousands) Percentage of Plan Assets as of December 31, Target Allocation Fair Value of Plan Assets (1) 2018 2017 Asset Category Equity securities 50 - 60% $ 46,772 61 % 60 % Fixed income 30 - 48% 27,887 37 % 35 % Cash equivalents 2 - 10% 1,551 2 % 5 % Total $ 76,210 100 % 100 % (1) Additional information regarding the fair value of Pension Plan assets as of December 31, 2018 can be found in Note 21 , " Fair Value ."
Schedule of Estimated Future Pension Benefit Payments	The following table presents estimated future pension benefit payments under the Pension Plan for retirees already receiving benefits and future retirees, assuming they retire and begin receiving unreduced benefits as soon as they are eligible. Estimated Future Pension Benefit Payments (Dollar amounts in thousands) Total Year ending December 31, 2019 $ 5,589 2020 5,000 2021 4,681 2022 4,978 2023 3,827 2024-2027 19,488

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares of Common Stock Available Under Share-Based Plans	Shares of Common Stock Available Under Share-Based Plans As of December 31, 2018 Shares Authorized Shares Available For Grant 2018 Stock and Incentive Plan (1) 3,254,706 3,223,548 Directors Plan 481,250 116,532
Nonqualified Stock Option Transactions	Nonqualified Stock Option Transactions (Amounts in thousands, except per share data) Year Ended December 31, 2018 Number of Options Weighted Average Exercise Price Options outstanding beginning balance 232 $ 25.19 Exercised (42 ) 12.17 Expired (190 ) 28.10 Options outstanding ending balance — $ —
Restricted Stock, Restricted Stock Unit, and Performance Share Award Transactions	Restricted Stock, Restricted Stock Unit, and Performance Share Award Transactions (Amounts in thousands, except per share data) Year Ended December 31, 2018 Restricted Stock/Unit Awards Performance Shares Number of Shares/Units Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Non-vested awards beginning balance 1,053 $ 20.36 466 $ 18.16 Granted 427 24.96 133 24.96 Vested (454 ) 17.54 (97 ) 17.54 Forfeited (79 ) 22.86 (34 ) 22.86 Non-vested awards ending balance 947 $ 23.32 468 $ 19.88
Schedule of Other Share-based Compensation, Activity	Other Restricted Stock, Restricted Stock Unit, and Performance Share Award Information (Amounts in thousands, except per share data) Years Ended December 31, 2018 2017 2016 Weighted-average grant date fair value of restricted stock, restricted stock unit, and performance share awards granted during the year $ 24.96 $ 24.71 $ 17.28 Total fair value of restricted stock, restricted stock unit, and performance share awards vested during the year 10,870 13,760 12,231 Income tax benefit realized from the vesting/release of restricted stock, restricted stock unit, and performance share awards 2,970 4,007 2,529
Effect of Recording Share-Based Compensation Expense	Effect of Recording Share-Based Compensation Expense (Dollar amounts in thousands) Years ended December 31, 2018 2017 2016 Total share-based compensation expense (1) $ 12,062 $ 11,223 $ 7,879 Income tax benefit 3,365 4,601 3,152 Share-based compensation expense, net of tax $ 8,697 $ 6,622 $ 4,727 Unrecognized compensation expense $ 13,982 $ 13,266 $ 9,990 Weighted-average amortization period remaining (in years) 1.2 1.3 1.3 (1) Comprised of restricted stock, restricted stock unit, and performance share awards expense.

Regulatory and Capital Matters

Regulatory and Capital Matters (Tables)	12 Months Ended
	Dec. 31, 2018
Banking and Thrift [Abstract]
Summary of Regulatory Capital Ratios	The following table outlines the Company's and the Bank's measures of capital as of the dates presented and the capital guidelines established by the Federal Reserve for the Company and the Bank to be categorized as adequately capitalized and the Bank to be categorized as "well-capitalized." Summary of Regulatory Capital Ratios (Dollar amounts in thousands) Actual Adequately Capitalized To Be Well-Capitalized Under Prompt Corrective Action Provisions Capital Ratio % Capital Ratio % Capital Ratio % As of December 31, 2018 Total capital to risk-weighted assets: First Midwest Bancorp, Inc. $ 1,626,489 12.62 $ 1,273,103 9.875 N/A N/A First Midwest Bank 1,463,026 11.39 1,268,662 9.875 $ 1,284,721 10.00 Tier 1 capital to risk-weighted assets: First Midwest Bancorp, Inc. 1,315,098 10.20 1,015,259 7.875 N/A N/A First Midwest Bank 1,359,607 10.58 1,011,718 7.875 1,027,777 8.00 CET1 to risk-weighted assets: First Midwest Bancorp, Inc. 1,315,432 10.20 821,876 6.375 N/A N/A First Midwest Bank 1,359,607 10.58 819,009 6.375 835,068 6.50 Tier 1 capital to average assets: First Midwest Bancorp, Inc. 1,315,098 8.90 591,293 4.000 N/A N/A First Midwest Bank 1,359,607 9.41 577,991 4.000 722,488 5.00 As of December 31, 2017 Total capital to risk-weighted assets: First Midwest Bancorp, Inc. $ 1,448,124 12.15 $ 1,102,634 9.250 N/A N/A First Midwest Bank 1,300,809 10.95 1,099,133 9.250 $ 1,188,252 10.00 Tier 1 capital to risk-weighted assets: First Midwest Bancorp, Inc. 1,204,468 10.10 864,227 7.250 N/A N/A First Midwest Bank 1,204,080 10.13 861,482 7.250 950,601 8.00 CET1 to risk-weighted assets: First Midwest Bancorp, Inc. 1,153,939 9.68 685,421 5.750 N/A N/A First Midwest Bank 1,204,080 10.13 683,245 5.750 772,364 6.50 Tier 1 capital to average assets: First Midwest Bancorp, Inc. 1,204,468 8.99 536,200 4.000 N/A N/A First Midwest Bank 1,204,080 9.10 529,147 4.000 661,434 5.00 N/A – Not applicable.

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Interest Rate Derivatives	The following table presents the impact of derivative instruments on net interest income for the years ended December 31, 2018 , 2017 , and 2016 . Hedge Income (Dollar amounts in thousands) Years Ended December 30, 2018 2017 2016 Fair Value Hedges Interest rate swaps in interest income $ (92 ) $ (167 ) $ (413 ) Cash Flow Hedges Interest rate swaps in interest income 2,611 5,159 7,641 Interest rate swaps in interest expense (3,673 ) (3,951 ) (4,074 ) Total cash flow hedges (1,062 ) 1,208 3,567 Total net (losses) gains on hedges $ (1,154 ) $ 1,041 $ 3,154 Cash Flow Hedges (Dollar amounts in thousands) As of December 31, 2018 2017 Gross notional amount outstanding $ 2,280,000 $ 1,960,000 Derivative asset fair value in other assets (1) 6,889 3,989 Derivative liability fair value in other liabilities (1) (11,328 ) (10,219 ) Weighted-average interest rate received 2.12 % 1.58 % Weighted-average interest rate paid 2.20 % 1.61 % Weighted-average maturity (in years) 1.53 2.25 (1) Certain cash flow hedges are transacted through a clearinghouse ("centrally cleared") and their change in fair value is settled by the counterparties to the transaction, which results in no fair value. Fair Value Hedges (Dollar amounts in thousands) As of December 31, 2017 Gross notional amount outstanding $ 5,458 Derivative liability fair value in other liabilities (101 ) Weighted-average interest rate received 3.38 % Weighted-average interest rate paid 5.96 % Weighted-average maturity (in years) 0.84 Fair value of derivative (1) $ 110 (1) This amount represents the fair value if credit risk related contingent features were triggered.
Schedule of Derivative Instruments	Other Derivative Instruments (Dollar amounts in thousands) As of December 31, 2018 2017 Gross notional amount outstanding $ 3,085,226 $ 2,665,358 Derivative asset fair value in other assets (1) 25,168 17,079 Derivative liability fair value in other liabilities (1) (17,533 ) (14,930 ) Fair value of derivative (2) 18,013 15,059 (1) Certain other derivative instruments are centrally cleared and their change in fair value is settled by the counterparties to the transaction, which resuts in no fair value. (2) This amount represents the fair value if credit risk related contingent factors were triggered.
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table presents the impact of derivative instruments on comprehensive income and the reclassification of gains (losses) from accumulated other comprehensive loss to net interest income for the years ended December 31, 2018 and 2017 , and 2016 . Cash Flow Hedge Accounting on Accumulated Other Comprehensive Income (Dollar amounts in thousands) Years Ended December 30, 2018 2017 2016 (Gains) losses recognized in other comprehensive income Interest rate swaps in interest income $ 18,776 $ 11,150 $ (4,674 ) Interest rate swaps in interest expense (20,500 ) (8,025 ) (1,068 ) Reclassification of (gains) losses included in net income Interest rate swaps in interest income $ 2,611 $ 5,159 $ 7,641 Interest rate swaps in interest expense (3,673 ) (3,951 ) (4,074 )
Offsetting Assets	The following table presents the fair value of the Company's derivatives and offsetting positions as of December 31, 2018 and 2017 . Fair Value of Offsetting Derivatives (Dollar amounts in thousands) As of December 31, 2018 2017 Assets Liabilities Assets Liabilities Gross amounts recognized $ 32,057 $ 28,861 $ 21,068 $ 25,250 Less: amounts offset in the Consolidated Statements of Financial Condition — — — — Net amount presented in the Consolidated Statements of Financial Condition (1) 32,057 28,861 21,068 25,250 Gross amounts not offset in the Consolidated Statements of Financial Condition: Offsetting derivative positions (11,678 ) (11,678 ) (16,880 ) (16,880 ) Cash collateral pledged (9,060 ) (3,506 ) — (8,370 ) Net credit exposure $ 11,319 $ 13,677 $ 4,188 $ — (1) Included in other assets or other liabilities in the Consolidated Statements of Financial Condition.
Offsetting Liabilities	The following table presents the fair value of the Company's derivatives and offsetting positions as of December 31, 2018 and 2017 . Fair Value of Offsetting Derivatives (Dollar amounts in thousands) As of December 31, 2018 2017 Assets Liabilities Assets Liabilities Gross amounts recognized $ 32,057 $ 28,861 $ 21,068 $ 25,250 Less: amounts offset in the Consolidated Statements of Financial Condition — — — — Net amount presented in the Consolidated Statements of Financial Condition (1) 32,057 28,861 21,068 25,250 Gross amounts not offset in the Consolidated Statements of Financial Condition: Offsetting derivative positions (11,678 ) (11,678 ) (16,880 ) (16,880 ) Cash collateral pledged (9,060 ) (3,506 ) — (8,370 ) Net credit exposure $ 11,319 $ 13,677 $ 4,188 $ — (1) Included in other assets or other liabilities in the Consolidated Statements of Financial Condition.

Commitments, Guarantees, and _2

Commitments, Guarantees, and Contingent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments Disclosure	Contractual or Notional Amounts of Financial Instruments (Dollar amounts in thousands) As of December 31, 2018 2017 Commitments to extend credit: Commercial, industrial, and agricultural $ 1,729,286 $ 1,729,426 Commercial real estate 296,882 377,551 Home equity 570,553 514,973 Other commitments (1) 244,917 244,222 Total commitments to extend credit $ 2,841,638 $ 2,866,172 Letters of credit $ 112,728 $ 128,801 (1) Other commitments includes installment and overdraft protection program commitments.

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following table provides the fair value for assets and liabilities required to be measured at fair value on a recurring basis in the Consolidated Statements of Financial Condition by level in the fair value hierarchy. Recurring Fair Value Measurements (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets Trading securities: Money market funds $ — $ — $ — $ 1,685 $ — $ — Mutual funds — — — 18,762 — — Total trading securities (1) — — — 20,447 — — Equity securities (1) 19,658 11,148 — — — — Securities available-for-sale (1) U.S. treasury securities 37,767 — — 46,345 — — U.S. agency securities — 142,563 — — 156,847 — CMOs — 1,315,209 — — 1,095,186 — MBSs — 466,934 — — 369,543 — Municipal securities — 227,187 — — 208,991 — Corporate debt securities — 82,349 — — — — Equity securities — — — — 7,297 — Total securities available-for-sale 37,767 2,234,242 — 46,345 1,837,864 — Mortgage servicing rights ("MSRs") (2) — — 6,730 — — 5,894 Derivative assets (2) — 32,057 — — 21,068 — Liabilities Derivative liabilities (3) $ — $ 28,861 $ — $ — $ 25,250 $ — (1) As a result of recently adopted accounting guidance, equity securities are no longer presented within trading securities or securities available-for-sale for the prior period and are not presented within equity securities for the current period. For further discussion of this guidance, see Note 2 of "Notes to the Consolidated Financial Statements" in Item 8 of this Form 10-K. (2) Included in other assets in the Consolidated Statements of Financial Condition. (3) Included in other liabilities in the Consolidated Statements of Financial Condition.
Significant Unobservable Inputs Used in the Valuation of CDOs	The following table presents the ranges of significant, unobservable inputs used by the Company to determine the fair value of MSRs as of December 31, 2018 and 2017 . Significant Unobservable Inputs Used in the Valuation of MSRs As of December 31, 2018 2017 Prepayment speed 6.5 % - 13.5% 4.2 % - 13.1% Maturity (months) 20 - 104 6 - 92 Discount rate 9.5 % - 12.0% 9.5 % - 12.0%
Carrying Value of CDOs	A rollforward of the carrying value of CDOs for the two years ended December 31, 2017 is presented in the following table. Carrying Value of CDOs (Dollar amounts in thousands) Years Ended December 31, 2017 2016 Beginning balance $ 33,260 $ 31,529 Additions — — Change in other comprehensive income (1) 14,421 2,337 Paydowns and sales (47,681 ) (606 ) Ending balance $ — $ 33,260 (1) Included in unrealized holding (losses) gains in the Consolidated Statements of Comprehensive Income.
Significant Unobservable Inputs Used in the Valuation of MSRs	The following table presents the ranges of significant, unobservable inputs used by the Company to determine the fair value of MSRs as of December 31, 2018 and 2017 . Significant Unobservable Inputs Used in the Valuation of MSRs As of December 31, 2018 2017 Prepayment speed 6.5 % - 13.5% 4.2 % - 13.1% Maturity (months) 20 - 104 6 - 92 Discount rate 9.5 % - 12.0% 9.5 % - 12.0%
Fair Value Inputs Mortgage Servicing Assets Quantitative Information	A rollforward of the carrying value of MSRs for the three years ended December 31, 2018 is presented in the following table. Carrying Value of MSRs (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Beginning balance $ 5,894 $ 6,120 $ 1,853 Additions from acquisition — — 3,092 New MSRs 1,080 673 1,263 Total gains (losses) included in earnings (1) : Changes in valuation inputs and assumptions 475 (41 ) 610 Other changes in fair value (2) (719 ) (858 ) (698 ) Ending balance (3) $ 6,730 $ 5,894 $ 6,120 Contractual servicing fees earned during the year (1) $ 1,517 $ 1,536 $ 1,312 Total amount of loans being serviced for the benefit of others at the end of the year 627,323 607,016 640,530 (1) Included in mortgage banking income in the Consolidated Statements of Income and related to assets held as of December 31, 2018 , 2017 , and 2016 . (2) Primarily represents changes in expected future cash flows over time due to payoffs and paydowns. (3) Included in other assets in the Consolidated Statements of Financial Condition.
Fair Value Assets Measured On Annual Basis	The fair value of Pension Plan assets is presented in the following table by level in the fair value hierarchy. Annual Fair Value Measurements for Pension Plan Assets (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Total Level 1 Level 2 Total Pension plan assets: Mutual funds (1) $ 27,246 $ — $ 27,246 $ 41,002 $ — $ 41,002 U.S. government and government agency securities 4,389 3,626 8,015 3,678 9,397 13,075 Corporate bonds — 10,472 10,472 — 9,171 9,171 Common stocks 26,882 — 26,882 — — — Common trust funds — 3,595 3,595 — 2,911 2,911 Total pension plan assets $ 58,517 $ 17,693 $ 76,210 $ 44,680 $ 21,479 $ 66,159 (1) Includes mutual funds, money market funds, cash, cash equivalents, and accrued interest.
Fair Value Measurements, Nonrecurring	The following table provides the fair value for each class of assets and liabilities required to be measured at fair value on a non-recurring basis in the Consolidated Statements of Financial Condition by level in the fair value hierarchy. Non-Recurring Fair Value Measurements (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Collateral-dependent impaired loans (1) $ — $ — $ 24,565 $ — $ — $ 33,240 OREO (2) — — 6,012 — — 12,340 Loans held-for-sale (3) — — 3,478 — — 21,098 Assets held-for-sale (4) — — 3,722 — — 2,208 (1) Includes impaired loans with charge-offs and impaired loans with a specific reserve during the periods presented. (2) Includes OREO with fair value adjustments subsequent to initial transfer that occurred during the periods presented. (3) Included in other assets in the Consolidated Statements of Financial Condition. (4) Included in premises, furniture, and equipment in the Consolidated Statements of Financial Condition.
Fair Value, by Balance Sheet Grouping	For certain financial instruments that are not required to be measured at fair value in the Consolidated Statements of Financial Condition, the Company must disclose the estimated fair values and the level within the fair value hierarchy as shown in the following table. Fair Value Measurements of Other Financial Instruments (Dollar amounts in thousands) As of December 31, 2018 As of December 31, 2017 Fair Value Hierarchy Carrying Fair Value Carrying Fair Value Assets Cash and due from banks 1 $ 211,189 $ 211,189 $ 192,800 $ 192,800 Interest-bearing deposits in other banks 2 78,069 78,069 153,770 153,770 Securities held-to-maturity 2 10,176 9,871 13,760 12,013 FHLB and FRB stock 2 80,302 80,302 69,708 69,708 Loans 3 11,346,668 11,052,040 10,345,397 10,059,992 Investment in BOLI 3 296,733 296,733 279,900 279,900 Accrued interest receivable 3 54,847 54,847 45,261 45,261 Other interest-earning assets 3 5 5 228 228 Liabilities Deposits 2 $ 12,084,112 $ 12,064,604 $ 11,053,325 $ 11,038,819 Borrowed funds 2 906,079 906,079 714,884 714,884 Senior and subordinated debt 2 203,808 211,207 195,170 208,666 Accrued interest payable 2 10,005 10,005 4,704 4,704

Condensed Parent Company Fina_2

Condensed Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Statements of Financial Condition - Parent Company Only	The following represents the condensed financial statements of First Midwest Bancorp, Inc., the Parent Company. Statements of Financial Condition (Parent Company only) (Dollar amounts in thousands) As of December 31, 2018 2017 Assets Cash and due from banks $ 158,026 $ 120,812 Investments in and advances to subsidiaries 2,091,158 1,952,414 Other assets 55,782 43,606 Total assets $ 2,304,966 $ 2,116,832 Liabilities and Stockholders' Equity Senior and subordinated debt $ 203,808 $ 195,170 Accrued interest payable and other liabilities 46,160 56,788 Stockholders' equity 2,054,998 1,864,874 Total liabilities and stockholders' equity $ 2,304,966 $ 2,116,832
Statements of Income - Parent Company Only	Statements of Income (Parent Company only) (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Income Dividends from subsidiaries $ 86,095 $ 74,091 $ 86,791 Interest income 453 2,211 2,188 Securities transactions and other 280 (1,372 ) 215 Total income 86,828 74,930 89,194 Expenses Interest expense 12,708 12,428 12,477 Salaries and employee benefits 22,430 20,978 16,104 Other expenses 9,440 9,126 7,110 Total expenses 44,578 42,532 35,691 Income before income tax benefit and equity in undistributed income of subsidiaries 42,250 32,398 53,503 Income tax benefit 13,299 14,851 12,878 Income before equity in undistributed income of subsidiaries 55,549 47,249 66,381 Equity in undistributed income of subsidiaries 102,321 51,138 25,968 Net income 157,870 98,387 92,349 Net income applicable to non-vested restricted shares (1,312 ) (916 ) (1,043 ) Net income applicable to common shares $ 156,558 $ 97,471 $ 91,306
Statements of Cash Flows - Parent Company Only	Statements of Cash Flows (Parent Company only) (Dollar amounts in thousands) Years Ended December 31, 2018 2017 2016 Operating Activities Net income $ 157,870 $ 98,387 $ 92,349 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed income of subsidiaries (102,321 ) (51,138 ) (25,968 ) Depreciation of premises, furniture, and equipment 42 9 2 Net securities losses — 1,523 — Share-based compensation expense 12,062 11,223 7,879 Tax benefit (expense) related to share-based compensation 258 349 (197 ) Net decrease (increase) in other assets 35,981 18,667 (75,104 ) Net (decrease) increase in other liabilities (17,942 ) (52,377 ) 74,571 Net cash provided by operating activities 85,950 26,643 73,532 Investing Activities Purchases of securities available-for-sale — — (14 ) Proceeds from sales and maturities of securities available-for-sale — 42,516 601 Purchase of premises, furniture, and equipment (61 ) (119 ) — Net cash received (paid) for acquisitions 39 (47,364 ) (14,905 ) Net cash used in investing activities (22 ) (4,967 ) (14,318 ) Financing Activities Net proceeds from the issuance of subordinated debt — — 146,484 Payments for the retirement of senior and subordinated debt — — (153,500 ) Cash dividends paid (44,293 ) (37,129 ) (29,198 ) Restricted stock activity (4,421 ) (3,952 ) (2,476 ) Net cash used in financing activities (48,714 ) (41,081 ) (38,690 ) Net increase in cash and cash equivalents 37,214 (19,405 ) 20,524 Cash and cash equivalents at beginning of year 120,812 140,217 119,693 Cash and cash equivalents at end of year $ 158,026 $ 120,812 $ 140,217 Supplemental Disclosures of Cash Flow Information: Common stock issued for acquisitions, net of issuance costs $ 83,303 $ 534,090 $ 54,896

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2018segmentsubsidiary
Property, Plant and Equipment [Line Items]
Number of wholly-owned subsidiaries | subsidiary	3
Number of reportable segments | segment	1
Finite-lived intangible assets amortization period	13 years
Furniture And Equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Furniture And Equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	10 years
Premises | Minimum
Property, Plant and Equipment [Line Items]
Useful life	25 years
Premises | Maximum
Property, Plant and Equipment [Line Items]
Useful life	40 years

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Noninterest Expense		$ 416,303	$ 415,909	$ 339,500
Non-cash transfer of equity securities previously classified as trading securities and securities and securities available-for-sale		30,800
Estimated sale-leaseback deferred gain, net		65,500	$ 74,600
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated sale-leaseback deferred gain, net		47,300
Reduction to lease expense		6,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Noninterest Expense		16,100
Difference between Revenue Guidance in Effect before and after Topic 606 | Card-based | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Noninterest Expense		7,500
Difference between Revenue Guidance in Effect before and after Topic 606 | Merchant servicing | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Noninterest Expense		$ 8,600
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of tax effects from AOCI to retained earnings	$ 6,800
Subsequent Event | Scenario, Forecast | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability					$ 145,000
Right-of-use asset					$ 145,000

Acquisitions - Narrative (Deta

Acquisitions - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 06, 2018	Oct. 12, 2018	Jan. 06, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 16, 2019	Sep. 30, 2018	Feb. 28, 2017	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill				$ 728,809	$ 697,608	$ 340,879				$ 319,007
Acquisition and integration related expenses				9,613	$ 20,123	$ 14,352
Bridgeview Bancorp, Inc.
Business Acquisition [Line Items]
Announced assets to be acquired								$ 1,200,000
Announced deposits to be acquired	$ 1,100,000
Announced loans to be acquired	$ 800,000
Fixed exchange ratio (in shares)	0.2767
Cash paid per share in business acquisition	$ 1.79
Announced consideration to be transferred	$ 145,000
Northern States Financial Corporation
Business Acquisition [Line Items]
Fixed exchange ratio (in shares)		0.0363
Total assets		$ 578,669
Total deposits		463,160
Total loans		284,924
Consideration transferred		$ 83,303
Common stock, shares issued (in shares)		3,310,912
Goodwill		$ 29,343
Cash paid		$ 0
Premier Asset Management LLC
Business Acquisition [Line Items]
Assets under management acquired									$ 550,000
Measurement period adjustment to increase goodwill				$ 1,900
Standard Bancshares, Inc.
Business Acquisition [Line Items]
Fixed exchange ratio (in shares)			0.4350
Total assets			$ 2,639,060
Total deposits			2,023,874
Total loans			1,762,303
Consideration transferred			$ 580,715
Common stock, shares issued (in shares)			21,057,085
Goodwill			$ 345,334
Cash paid			$ 47,125
Subsequent Event | Northern Oak Wealth Management, Inc.
Business Acquisition [Line Items]
Assets under management acquired							$ 800,000

Acquisitions - Acquisition Act

Acquisitions - Acquisition Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 12, 2018	Jan. 06, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Goodwill			$ 728,809	$ 697,608	$ 340,879	$ 319,007
Northern States Financial Corporation
Assets
Cash and due from banks and interest-bearing deposits in other banks	$ 160,145
Equity securities	3,915
Securities available-for-sale	47,149
FHLB and FRB stock	554
Loans	284,924
OREO	2,549
Investment in BOLI	11,104
Goodwill	29,343
Other intangible assets	12,230
Premises, furniture, and equipment	7,039
Accrued interest receivable and other assets	19,717
Total assets	578,669
Liabilities
Noninterest-bearing deposits	346,714
Interest-bearing deposits	116,446
Total deposits	463,160
Borrowed funds	18,218
Senior and subordinated debt	8,038
Accrued interest payable and other liabilities	5,950
Total liabilities	495,366
Consideration Paid
Common stock (2018 - 3,310,912, shares issued at $25.16 per share, 2017 - 21,057,085 share issued at $25.34 per share), net of issuance costs	83,303
Cash paid	0
Total consideration paid	$ 83,303
Common stock, shares issued (in shares)	3,310,912
Shares issued (in dollars per share)	$ 25.16
Standard Bancshares, Inc.
Assets
Cash and due from banks and interest-bearing deposits in other banks		$ 102,149
Equity securities		0
Securities available-for-sale		214,107
FHLB and FRB stock		3,247
Loans		1,762,303
OREO		8,424
Investment in BOLI		55,629
Goodwill		345,334
Other intangible assets		31,072
Premises, furniture, and equipment		56,517
Accrued interest receivable and other assets		60,278
Total assets		2,639,060
Liabilities
Noninterest-bearing deposits		675,354
Interest-bearing deposits		1,348,520
Total deposits		2,023,874
Borrowed funds		0
Senior and subordinated debt		0
Accrued interest payable and other liabilities		34,471
Total liabilities		2,058,345
Consideration Paid
Common stock (2018 - 3,310,912, shares issued at $25.16 per share, 2017 - 21,057,085 share issued at $25.34 per share), net of issuance costs		533,590
Cash paid		47,125
Total consideration paid		$ 580,715
Common stock, shares issued (in shares)		21,057,085
Shares issued (in dollars per share)		$ 25.34

Securities - Securities Portfo

Securities - Securities Portfolio (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		$ 2,311,920
Amortized Cost			$ 1,907,826
Gross Unrealized Gains		4,405
Gross Unrealized Gains			1,406
Gross Unrealized Losses		(44,316)
Gross Unrealized Losses			(25,023)
Fair Value		2,272,009
Fair Value			1,884,209
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost		10,176	13,760
Fair Value		9,871	12,013
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities		30,806	0
Trading Securities		0	20,447	[1]
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		37,925
Amortized Cost			46,529
Gross Unrealized Gains		17
Gross Unrealized Gains			0
Gross Unrealized Losses		(175)
Gross Unrealized Losses			(184)
Fair Value		37,767
Fair Value			46,345
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		144,125
Amortized Cost			157,636
Gross Unrealized Gains		45
Gross Unrealized Gains			197
Gross Unrealized Losses		(1,607)
Gross Unrealized Losses			(986)
Fair Value		142,563
Fair Value			156,847
Collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		1,336,531
Amortized Cost			1,113,019
Gross Unrealized Gains		3,362
Gross Unrealized Gains			121
Gross Unrealized Losses		(24,684)
Gross Unrealized Losses			(17,954)
Fair Value		1,315,209
Fair Value			1,095,186
Other Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		477,665
Amortized Cost			373,676
Gross Unrealized Gains		520
Gross Unrealized Gains			201
Gross Unrealized Losses		(11,251)
Gross Unrealized Losses			(4,334)
Fair Value		466,934
Fair Value			369,543
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		229,600
Amortized Cost			209,558
Gross Unrealized Gains		461
Gross Unrealized Gains			693
Gross Unrealized Losses		(2,874)
Gross Unrealized Losses			(1,260)
Fair Value		227,187
Fair Value			208,991
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost		10,176	13,760
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(305)	(1,747)
Fair Value		9,871	12,013
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		86,074
Amortized Cost			0
Gross Unrealized Gains		0
Gross Unrealized Gains			0
Gross Unrealized Losses		(3,725)
Gross Unrealized Losses			0
Fair Value		82,349
Fair Value			0
Equity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]		7,408
Gross Unrealized Gains	[1]		194
Gross Unrealized Losses	[1]		(305)
Fair Value	[1]		$ 7,297
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities	[1]	$ 30,806
[1]	As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."

Securities - Remaining Contrac

Securities - Remaining Contractual Maturity of Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available-for-Sale Securities, Amortized Cost Basis [Abstract]
One year or less	$ 113,548
After one year to five years	176,349
After five years to ten years	207,827
After ten years	0
Securities that do not have a single contractual maturity date	1,814,196
Amortized Cost	2,311,920
Available-for-Sale Securities, Fair Value [Abstract]
One year or less	111,755
After one year to five years	173,565
After five years to ten years	204,546
After ten years	0
Securities that do not have a single contractual maturity date	1,782,143
Total	2,272,009
Held-to-Maturity Securities, Amortized Cost [Abstract]
One year or less	7,580
After one year to five years	2,236
After five years to ten years	360
After ten years	0
Securities that do not have a single contractual maturity date	0
Amortized Cost	10,176	$ 13,760
Held-to-Maturity Securities, Fair Value [Abstract]
One year or less	7,353
After one year to five years	2,169
After five years to ten years	349
After ten years	0
Securities that do not have a single contractual maturity date	0
Total	$ 9,871	$ 12,013

Securities - Narrative (Detail

Securities - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, pledged	$ 1,200,000,000	$ 1,200,000,000	$ 1,100,000,000
Debt securities, held-to-maturity, pledged	0	0	0
Purchases of securities	47,100,000	$ 735,701,000	733,440,000	$ 933,317,000
Securities sold	$ 25,000,000
Net realized (losses) gains on sales of securities			(1,876,000)	1,420,000
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Net realized (losses) gains on sales of securities			(3,200,000)	1,100,000
Equity securities
Debt Securities, Available-for-sale [Line Items]
Net realized (losses) gains on sales of securities			$ 1,300,000	$ 304,000

Securities - Securities Gains

Securities - Securities Gains (Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gains (losses) on sales of securities:
Gross realized gains	$ 0
Gross realized gains		$ 5,478	$ 1,589
Gross realized losses	0
Gross realized losses		(7,354)	(169)
Net realized gains (losses) on sales of securities	0
Net realized gains (losses) on sales of securities		(1,876)	1,420
Non-cash impairment charges:
OTTI	0
OTTI		0	0
Net realized gains (losses)	$ 0
Net realized gains (losses)		$ (1,876)	$ 1,420

Securities - Changes In Credit

Securities - Changes In Credit Losses Recognized In Earnings (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)security	Dec. 31, 2016USD ($)
Changes in Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		$ 0	$ 23,345	$ 23,345
OTTI included in earnings:
Reduction for securities sales	[1],[2]	0	(23,345)	0
Ending balance		$ 0	0	$ 23,345
CDOs
OTTI included in earnings:
Reduction for securities sales			$ (47,700)
Number of CDOs sold (security) | security			11
[1]	Included in net securities gains (losses) in the Consolidated Statements of Income.
[2]	These reductions were driven by the sale of 11 CDOs with a carrying value of $47.7 million during the year ended December 31, 2017.

Securities - Securities In An

Securities - Securities In An Unrealized Loss Position (Details) $ in Thousands		Dec. 31, 2018USD ($)security	Dec. 31, 2017USD ($)security
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security		882
Number of Securities | security			656
Fair Value
Fair Value - Less Than 12 Months		$ 501,061
Fair Value - Less Than 12 Months			$ 613,975
Fair Value - 12 Months or Longer		1,365,068
Fair Value - 12 Months or Longer			1,015,438
Fair Value - Total		1,866,129
Fair Value - Total			1,629,413
Unrealized Losses
Unrealized Losses - Less Than 12 Months		8,046
Unrealized Losses - Less Than 12 Months			5,247
Unrealized Losses - 12 Months or Longer		36,270
Unrealized Losses - 12 Months or Longer			19,776
Unrealized Losses - Total		$ 44,316
Unrealized Losses - Total			$ 25,023
U.S. treasury securities
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security		17
Number of Securities | security			20
Fair Value
Fair Value - Less Than 12 Months		$ 15,894
Fair Value - Less Than 12 Months			$ 19,918
Fair Value - 12 Months or Longer		13,886
Fair Value - 12 Months or Longer			26,427
Fair Value - Total		29,780
Fair Value - Total			46,345
Unrealized Losses
Unrealized Losses - Less Than 12 Months		57
Unrealized Losses - Less Than 12 Months			87
Unrealized Losses - 12 Months or Longer		118
Unrealized Losses - 12 Months or Longer			97
Unrealized Losses - Total		$ 175
Unrealized Losses - Total			$ 184
U.S. agency securities
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security		74
Number of Securities | security			72
Fair Value
Fair Value - Less Than 12 Months		$ 34,263
Fair Value - Less Than 12 Months			$ 66,899
Fair Value - 12 Months or Longer		93,227
Fair Value - 12 Months or Longer			58,021
Fair Value - Total		127,490
Fair Value - Total			124,920
Unrealized Losses
Unrealized Losses - Less Than 12 Months		320
Unrealized Losses - Less Than 12 Months			300
Unrealized Losses - 12 Months or Longer		1,287
Unrealized Losses - 12 Months or Longer			686
Unrealized Losses - Total		$ 1,607
Unrealized Losses - Total			$ 986
CMOs
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security		234
Number of Securities | security			211
Fair Value
Fair Value - Less Than 12 Months		$ 171,901
Fair Value - Less Than 12 Months			$ 365,131
Fair Value - 12 Months or Longer		863,747
Fair Value - 12 Months or Longer			633,227
Fair Value - Total		1,035,648
Fair Value - Total			998,358
Unrealized Losses
Unrealized Losses - Less Than 12 Months		1,671
Unrealized Losses - Less Than 12 Months			3,265
Unrealized Losses - 12 Months or Longer		23,013
Unrealized Losses - 12 Months or Longer			14,689
Unrealized Losses - Total		$ 24,684
Unrealized Losses - Total			$ 17,954
MBSs
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security		118
Number of Securities | security			86
Fair Value
Fair Value - Less Than 12 Months		$ 135,791
Fair Value - Less Than 12 Months			$ 126,136
Fair Value - 12 Months or Longer		284,273
Fair Value - 12 Months or Longer			210,017
Fair Value - Total		420,064
Fair Value - Total			336,153
Unrealized Losses
Unrealized Losses - Less Than 12 Months		1,715
Unrealized Losses - Less Than 12 Months			902
Unrealized Losses - 12 Months or Longer		9,536
Unrealized Losses - 12 Months or Longer			3,432
Unrealized Losses - Total		$ 11,251
Unrealized Losses - Total			$ 4,334
Municipal securities
Schedule of Held-to-Maturity Securities [Line Items]
Number of Securities | security		5	8
Fair Value - Less than 12 Months		$ 0	$ 0
Unrealized Losses - Less than 12 Months		0	0
Fair Value - 12 Months or Longer		9,871	12,013
Unrealized Losses - 12 Months or Longer		305	1,747
Fair Value - Total		9,871	12,013
Unrealized Losses - Total		$ 305	$ 1,747
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security		423
Number of Securities | security			265
Fair Value
Fair Value - Less Than 12 Months		$ 60,863
Fair Value - Less Than 12 Months			$ 35,500
Fair Value - 12 Months or Longer		109,935
Fair Value - 12 Months or Longer			81,360
Fair Value - Total		170,798
Fair Value - Total			116,860
Unrealized Losses
Unrealized Losses - Less Than 12 Months		558
Unrealized Losses - Less Than 12 Months			479
Unrealized Losses - 12 Months or Longer		2,316
Unrealized Losses - 12 Months or Longer			781
Unrealized Losses - Total		$ 2,874
Unrealized Losses - Total			$ 1,260
Corporate debt securities
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security		16
Fair Value
Fair Value - Less Than 12 Months		$ 82,349
Fair Value - 12 Months or Longer		0
Fair Value - Total		82,349
Unrealized Losses
Unrealized Losses - Less Than 12 Months		3,725
Unrealized Losses - 12 Months or Longer		0
Unrealized Losses - Total		$ 3,725
Equity securities
Securities in An Unrealized Loss Position [Line Items]
Number of Securities | security	[1]		2
Fair Value
Fair Value - Less Than 12 Months	[1]		$ 391
Fair Value - 12 Months or Longer	[1]		6,386
Fair Value - Total	[1]		6,777
Unrealized Losses
Unrealized Losses - Less Than 12 Months	[1]		214
Unrealized Losses - 12 Months or Longer	[1]		91
Unrealized Losses - Total	[1]		$ 305
[1]	As a result of accounting guidance adopted in 2018, equity securities are no longer presented within securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2, "Recent Accounting Pronouncements."

Loans - Loan Portfolio (Detail

Loans - Loan Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 11,446,783	$ 10,437,812
Deferred loan fees included in total loans	6,715	4,986
Overdrawn demand deposits included in total loans	8,583	8,587
Commercial, industrial, and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,551,221	3,960,800
Commercial, industrial, and agricultural | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,120,293	3,529,914
Total loans	4,120,293	3,529,914
Commercial, industrial, and agricultural | Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	430,928	430,886
Total loans	430,928	430,886
Commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,596,249	4,553,618
Total loans	4,596,249	4,553,618
Commercial real estate loans | Office, retail, and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,820,917	1,979,820
Total loans	1,820,917	1,979,820
Commercial real estate loans | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	764,185	675,463
Total loans	764,185	675,463
Commercial real estate loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	649,337	539,820
Total loans	649,337	539,820
Commercial real estate loans | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,361,810	1,358,515
Total loans	1,361,810	1,358,515
Total corporate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,147,470	8,514,418
Total loans	9,147,470	8,514,418
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,299,313	1,923,394
Total loans	2,299,313	1,923,394
Consumer loans | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	851,607	827,055
Total loans	851,607	827,055
Consumer loans | 1-4 family mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,017,181	774,357
Total loans	1,017,181	774,357
Consumer loans | Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	430,525	321,982
Total loans	$ 430,525	$ 321,982

Loans - Carrying Value of Loan

Loans - Carrying Value of Loans Pledged (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Loans pledged to secure:
FHLB advances (blanket pledge)	$ 4,443,268	$ 4,587,240
FRB's Discount Window Primary Credit Program	1,166,128	1,099,712
Total	$ 5,609,396	$ 5,686,952

Loans - Narrative (Details)

Loans - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Eligible borrowing capacity in FHLB advances	$ 2,500,000	$ 2,600,000
FRBs Discount Window Primary Credit Program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Eligible borrowing capacity through FRB's Discount Window Primary Credit Program	$ 881,113	$ 843,618

Loans - Loans Sales (Details)

Loans - Loans Sales (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains on loan sales		$ 5,562	$ 7,078	$ 8,931
Corporate loan sales
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales		17,900	52,974	54,681
Less book value of loans sold		17,498	51,781	52,821
Total net gains on loan sales	[1]	402	1,193	1,860
1-4 family mortgage loan sales
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales		245,967	258,626	290,383
Less book value of loans sold		240,807	252,741	283,312
Total net gains on loan sales	[2]	$ 5,160	$ 5,885	$ 7,071
[1]	Net gains on corporate loan sales are included in other service charges, commissions, and fees in the Consolidated Statements of Income.
[2]	Net gains on 1-4 family mortgage loan sales are included in mortgage banking income in the Consolidated Statements of Income.

Acquired and Covered Loans - N

Acquired and Covered Loans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Certain Loans Acquired in Transfer Accounted for as Debt Securities Accretable Yield Movement Schedule [Line Items]
Non-residential mortgage loans with expired loss share agreements	$ 10.4	$ 12.7
Outstanding balance of PCI loans	175.2	210.7
Renewed non-purchased credit impaired loans	458	366
Acquired and Covered Receivables
Certain Loans Acquired in Transfer Accounted for as Debt Securities Accretable Yield Movement Schedule [Line Items]
Accretion on acquired loans	$ 19.5	$ 33.9	$ 14.6

Acquired and Covered Loans - A

Acquired and Covered Loans - Acquired and Covered Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Acquired Loans [Line Items]
Non-PCI	$ 1,252,361	$ 1,524,453
Total	1,366,229	1,661,906
Acquired loans
Acquired Loans [Line Items]
Non-PCI	1,247,492	1,512,664
Total	1,355,541	1,643,358
Covered loans
Acquired Loans [Line Items]
Non-PCI	4,869	11,789
Total	10,688	18,548
Receivables acquired with deteriorated credit quality
Acquired Loans [Line Items]
PCI	113,868	137,453
Receivables acquired with deteriorated credit quality | Acquired loans
Acquired Loans [Line Items]
PCI	108,049	130,694
Receivables acquired with deteriorated credit quality | Covered loans
Acquired Loans [Line Items]
PCI	$ 5,819	$ 6,759

Acquired and Covered Loans - C

Acquired and Covered Loans - Changes in FDIC Indemnification Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
FDIC Indemnification Asset [Roll Forward]
Beginning balance	$ 3,314	$ 4,522	$ 3,903
Amortization	(1,208)	(1,208)	(1,185)
Change in expected reimbursements from the FDIC for changes in expected credit losses	(237)	(792)	330
Net payments to the FDIC	235	792	1,474
Ending balance	$ 2,104	$ 3,314	$ 4,522

Acquired and Covered Loans -_2

Acquired and Covered Loans - Changes in Accretable Yield (Details) - Receivables acquired with deteriorated credit quality - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in Accretable Yield [Roll Forward]
Beginning balance		$ 32,957	$ 19,386	$ 24,912
Additions		3,699	27,316	3,981
Accretion		(12,354)	(15,529)	(8,063)
Other	[1]	19,423	1,784	(1,444)
Ending balance		$ 43,725	$ 32,957	$ 19,386
[1]	Increases represent a rise in the expected future cash flows to be collected over the remaining estimated life of the underlying portfolio while decreases result from the resolution of certain loans occurring earlier than anticipated.

Past Due Loans, Allowance For_3

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Aging Analysis of Past Due Loans and Non-Performing Loans by Class (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	$ 11,357,176	$ 10,365,369
Past Due		89,607	72,443
Total loans		11,446,783	10,437,812
Non-accrual	[2]	56,935	66,924
90 Days or More Past Due, Still Accruing Interest		8,282	3,555
Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		113,868	137,453
Receivables acquired with deteriorated credit quality | Non-accrual
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		58	763
30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		40,102	52,570
90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		49,505	19,873
Commercial, industrial, and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		4,551,221	3,960,800
Commercial, industrial, and agricultural | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		4,457	12,702
Commercial, industrial, and agricultural | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	4,085,164	3,490,783
Past Due		35,129	39,131
Total loans		4,120,293	3,529,914
Non-accrual	[2]	33,507	40,580
90 Days or More Past Due, Still Accruing Interest		422	1,830
Commercial, industrial, and agricultural | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	428,357	430,221
Past Due		2,571	665
Total loans		430,928	430,886
Non-accrual	[2]	1,564	219
90 Days or More Past Due, Still Accruing Interest		101	177
Commercial, industrial, and agricultural | 30-89 Days Past Due | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		8,832	34,620
Commercial, industrial, and agricultural | 30-89 Days Past Due | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		940	280
Commercial, industrial, and agricultural | 90 Days or More Past Due | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		26,297	4,511
Commercial, industrial, and agricultural | 90 Days or More Past Due | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		1,631	385
Commercial real estate loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	4,561,677	4,534,968
Past Due		34,572	18,650
Total loans		4,596,249	4,553,618
Non-accrual	[2]	12,615	15,767
90 Days or More Past Due, Still Accruing Interest		6,467	1,053
Commercial real estate loans | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		89,878	102,813
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	1,803,059	1,970,564
Past Due		17,858	9,256
Total loans		1,820,917	1,979,820
Non-accrual	[2]	6,510	11,560
90 Days or More Past Due, Still Accruing Interest		4,081	345
Commercial real estate loans | Office, retail, and industrial | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		16,556	14,575
Commercial real estate loans | Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	759,402	672,098
Past Due		4,783	3,365
Total loans		764,185	675,463
Non-accrual	[2]	3,107	377
90 Days or More Past Due, Still Accruing Interest		189	20
Commercial real estate loans | Multi-family | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		13,663	14,071
Commercial real estate loans | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	645,774	539,043
Past Due		3,563	777
Total loans		649,337	539,820
Non-accrual	[2]	144	209
90 Days or More Past Due, Still Accruing Interest		0	371
Commercial real estate loans | Construction | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		4,838	8,843
Commercial real estate loans | Other commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	1,353,442	1,353,263
Past Due		8,368	5,252
Total loans		1,361,810	1,358,515
Non-accrual	[2]	2,854	3,621
90 Days or More Past Due, Still Accruing Interest		2,197	317
Commercial real estate loans | Other commercial real estate | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		54,821	65,324
Commercial real estate loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		18,036	9,016
Commercial real estate loans | 30-89 Days Past Due | Office, retail, and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		8,209	3,156
Commercial real estate loans | 30-89 Days Past Due | Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		1,487	3,117
Commercial real estate loans | 30-89 Days Past Due | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		3,419	198
Commercial real estate loans | 30-89 Days Past Due | Other commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		4,921	2,545
Commercial real estate loans | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		16,536	9,634
Commercial real estate loans | 90 Days or More Past Due | Office, retail, and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		9,649	6,100
Commercial real estate loans | 90 Days or More Past Due | Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		3,296	248
Commercial real estate loans | 90 Days or More Past Due | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		144	579
Commercial real estate loans | 90 Days or More Past Due | Other commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		3,447	2,707
Total corporate loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	9,075,198	8,455,972
Past Due		72,272	58,446
Total loans		9,147,470	8,514,418
Non-accrual	[2]	47,686	56,566
90 Days or More Past Due, Still Accruing Interest		6,990	3,060
Total corporate loans | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		94,335	115,515
Total corporate loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		27,808	43,916
Total corporate loans | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		44,464	14,530
Consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	2,281,978	1,909,397
Past Due		17,335	13,997
Total loans		2,299,313	1,923,394
Non-accrual	[2]	9,249	10,358
90 Days or More Past Due, Still Accruing Interest		1,292	495
Consumer loans | Receivables acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
PCI		19,533	21,938
Consumer loans | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	843,217	820,099
Past Due		8,390	6,956
Total loans		851,607	827,055
Non-accrual	[2]	5,393	5,946
90 Days or More Past Due, Still Accruing Interest		104	98
Consumer loans | 1-4 family mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	1,009,925	770,120
Past Due		7,256	4,237
Total loans		1,017,181	774,357
Non-accrual	[2]	3,856	4,412
90 Days or More Past Due, Still Accruing Interest		1,147	0
Consumer loans | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	428,836	319,178
Past Due		1,689	2,804
Total loans		430,525	321,982
Non-accrual	[2]	0	0
90 Days or More Past Due, Still Accruing Interest		41	397
Consumer loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		12,294	8,654
Consumer loans | 30-89 Days Past Due | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		6,285	4,102
Consumer loans | 30-89 Days Past Due | 1-4 family mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		4,361	2,145
Consumer loans | 30-89 Days Past Due | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		1,648	2,407
Consumer loans | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		5,041	5,343
Consumer loans | 90 Days or More Past Due | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		2,105	2,854
Consumer loans | 90 Days or More Past Due | 1-4 family mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		2,895	2,092
Consumer loans | 90 Days or More Past Due | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		$ 41	$ 397
[1]	PCI loans with an accretable yield are considered current.
[2]	Includes PCI loans of $58,000 and $763,000 as of December 31, 2018 and December 31, 2017, respectively, which no longer have an accretable yield as estimates of expected future cash flows have decreased since the acquisition due to credit deterioration.

Past Due Loans, Allowance For_4

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	$ 96,729	$ 87,083	$ 74,855
Charge-offs	(47,985)	(30,823)	(23,293)
Recoveries	6,621	9,179	4,763
Net charge-offs	(41,364)	(21,644)	(18,530)
Provision for loan losses and other	48,054	31,290	30,758
Ending Balance	103,419	96,729	87,083
Reserve for Unfunded Commitments
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	1,000	1,000	1,225
Charge-offs	0	0	0
Recoveries	0	0	0
Net charge-offs	0	0	0
Provision for loan losses and other	200	0	(225)
Ending Balance	1,200	1,000	1,000
Commercial, Industrial, and Agricultural
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	55,791	40,709	37,074
Charge-offs	(36,477)	(22,885)	(9,982)
Recoveries	2,946	4,150	2,451
Net charge-offs	(33,531)	(18,735)	(7,531)
Provision for loan losses and other	41,016	33,817	11,166
Ending Balance	63,276	55,791	40,709
Commercial Real Estate Loans
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	23,392
Ending Balance	17,471	23,392
Commercial Real Estate Loans | Office, Retail, and Industrial
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	10,996	17,595	13,124
Charge-offs	(2,286)	(190)	(4,707)
Recoveries	334	2,935	337
Net charge-offs	(1,952)	2,745	(4,370)
Provision for loan losses and other	(1,144)	(9,344)	8,841
Ending Balance	7,900	10,996	17,595
Commercial Real Estate Loans | Multi-family
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	2,534	3,261	2,469
Charge-offs	(5)	0	(307)
Recoveries	3	39	97
Net charge-offs	(2)	39	(210)
Provision for loan losses and other	(68)	(766)	1,002
Ending Balance	2,464	2,534	3,261
Commercial Real Estate Loans | Construction
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	3,481	3,444	1,440
Charge-offs	(1)	(38)	(134)
Recoveries	125	270	56
Net charge-offs	124	232	(78)
Provision for loan losses and other	(1,432)	(195)	2,082
Ending Balance	2,173	3,481	3,444
Commercial Real Estate Loans | Other Commercial Real Estate
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	6,381	7,739	6,109
Charge-offs	(410)	(755)	(2,932)
Recoveries	1,532	244	524
Net charge-offs	1,122	(511)	(2,408)
Provision for loan losses and other	(2,569)	(847)	4,038
Ending Balance	4,934	6,381	7,739
Consumer Loans
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	16,546
Ending Balance	21,472	16,546
Consumer Loans | Consumer Loans
Allowance for Credit Losses by Portfolio Segment [Roll Forward]
Beginning balance	16,546	13,335	13,414
Charge-offs	(8,806)	(6,955)	(5,231)
Recoveries	1,681	1,541	1,298
Net charge-offs	(7,125)	(5,414)	(3,933)
Provision for loan losses and other	12,051	8,625	3,854
Ending Balance	$ 21,472	$ 16,546	$ 13,335

Past Due Loans, Allowance For_5

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Loans and Related Allowance for Credit Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	$ 42,509	$ 51,617
Loans Collectively Evaluated for Impairment	11,290,406	10,248,742
Total loans	11,446,783	10,437,812
Allowance for Credit Losses Individually Evaluated for Impairment	4,709	10,074
Allowance for Credit Losses Collectively Evaluated for Impairment	94,578	82,341
Total Allowance for Credit Losses	103,419	96,729	$ 87,083	$ 74,855
PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	113,868	137,453
Total Allowance for Credit Losses	4,132	4,314
Reserve for unfunded commitments
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	0	0
Loans Collectively Evaluated for Impairment	0	0
Total loans	0	0
Allowance for Credit Losses Individually Evaluated for Impairment	0	0
Allowance for Credit Losses Collectively Evaluated for Impairment	1,200	1,000
Total Allowance for Credit Losses	1,200	1,000	1,000	1,225
Reserve for unfunded commitments | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	0	0
Total Allowance for Credit Losses	0	0
Commercial, industrial, and agricultural
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	32,415	38,718
Loans Collectively Evaluated for Impairment	4,514,349	3,909,380
Total loans	4,551,221	3,960,800
Allowance for Credit Losses Individually Evaluated for Impairment	3,961	10,074
Allowance for Credit Losses Collectively Evaluated for Impairment	58,947	45,293
Total Allowance for Credit Losses	63,276	55,791	40,709	37,074
Commercial, industrial, and agricultural | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	4,457	12,702
Total Allowance for Credit Losses	368	424
Commercial real estate loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	10,094	12,899
Loans Collectively Evaluated for Impairment	4,496,277	4,437,906
Total loans	4,596,249	4,553,618
Allowance for Credit Losses Individually Evaluated for Impairment	748	0
Allowance for Credit Losses Collectively Evaluated for Impairment	14,337	20,515
Total Allowance for Credit Losses	17,471	23,392
Commercial real estate loans | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	89,878	102,813
Total Allowance for Credit Losses	2,386	2,877
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	5,057	10,810
Loans Collectively Evaluated for Impairment	1,799,304	1,954,435
Total loans	1,820,917	1,979,820
Allowance for Credit Losses Individually Evaluated for Impairment	748	0
Allowance for Credit Losses Collectively Evaluated for Impairment	5,984	9,333
Total Allowance for Credit Losses	7,900	10,996	17,595	13,124
Commercial real estate loans | Office, retail, and industrial | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	16,556	14,575
Total Allowance for Credit Losses	1,168	1,663
Commercial real estate loans | Multi-family
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	3,492	621
Loans Collectively Evaluated for Impairment	747,030	660,771
Total loans	764,185	675,463
Allowance for Credit Losses Individually Evaluated for Impairment	0	0
Allowance for Credit Losses Collectively Evaluated for Impairment	2,154	2,436
Total Allowance for Credit Losses	2,464	2,534	3,261	2,469
Commercial real estate loans | Multi-family | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	13,663	14,071
Total Allowance for Credit Losses	310	98
Commercial real estate loans | Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	0	0
Loans Collectively Evaluated for Impairment	644,499	530,977
Total loans	649,337	539,820
Allowance for Credit Losses Individually Evaluated for Impairment	0	0
Allowance for Credit Losses Collectively Evaluated for Impairment	2,019	3,331
Total Allowance for Credit Losses	2,173	3,481	3,444	1,440
Commercial real estate loans | Construction | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	4,838	8,843
Total Allowance for Credit Losses	154	150
Commercial real estate loans | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	1,545	1,468
Loans Collectively Evaluated for Impairment	1,305,444	1,291,723
Total loans	1,361,810	1,358,515
Allowance for Credit Losses Individually Evaluated for Impairment	0	0
Allowance for Credit Losses Collectively Evaluated for Impairment	4,180	5,415
Total Allowance for Credit Losses	4,934	6,381	$ 7,739	$ 6,109
Commercial real estate loans | Other commercial real estate | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	54,821	65,324
Total Allowance for Credit Losses	754	966
Total corporate loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	42,509	51,617
Loans Collectively Evaluated for Impairment	9,010,626	8,347,286
Total loans	9,147,470	8,514,418
Allowance for Credit Losses Individually Evaluated for Impairment	4,709	10,074
Allowance for Credit Losses Collectively Evaluated for Impairment	73,284	65,808
Total Allowance for Credit Losses	80,747	79,183
Total corporate loans | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	94,335	115,515
Total Allowance for Credit Losses	2,754	3,301
Consumer loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans Individually Evaluated for Impairment	0	0
Loans Collectively Evaluated for Impairment	2,279,780	1,901,456
Total loans	2,299,313	1,923,394
Allowance for Credit Losses Individually Evaluated for Impairment	0	0
Allowance for Credit Losses Collectively Evaluated for Impairment	20,094	15,533
Total Allowance for Credit Losses	21,472	16,546
Consumer loans | PCI
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI	19,533	21,938
Total Allowance for Credit Losses	$ 1,378	$ 1,013

Past Due Loans, Allowance For_6

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Impaired Loans Individually Evaluated by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	$ 15,766	$ 13,477
Recorded Investment in Loans with a Specific Reserve	26,743	38,140
Unpaid Principal Balance	64,344	69,625
Specific Reserve	4,709	10,074
Commercial, industrial, and agricultural | Commercial and industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	7,550	4,234
Recorded Investment in Loans with a Specific Reserve	23,349	34,484
Unpaid Principal Balance	49,102	53,192
Specific Reserve	3,960	10,074
Commercial, industrial, and agricultural | Agricultural
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	1,318	0
Recorded Investment in Loans with a Specific Reserve	198	0
Unpaid Principal Balance	3,997	0
Specific Reserve	1	0
Commercial real estate loans
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	6,898	9,243
Recorded Investment in Loans with a Specific Reserve	3,196	3,656
Unpaid Principal Balance	11,245	16,433
Specific Reserve	748	0
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	1,861	7,154
Recorded Investment in Loans with a Specific Reserve	3,196	3,656
Unpaid Principal Balance	6,141	14,246
Specific Reserve	748	0
Commercial real estate loans | Multi-family
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	3,492	621
Recorded Investment in Loans with a Specific Reserve	0	0
Unpaid Principal Balance	3,492	621
Specific Reserve	0	0
Commercial real estate loans | Construction
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	0	0
Recorded Investment in Loans with a Specific Reserve	0	0
Unpaid Principal Balance	0	0
Specific Reserve	0	0
Commercial real estate loans | Other commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment in Loans with No Specific Reserve	1,545	1,468
Recorded Investment in Loans with a Specific Reserve	0	0
Unpaid Principal Balance	1,612	1,566
Specific Reserve	$ 0	$ 0

Past Due Loans, Allowance For_7

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Impaired Loans Individually Evaluated by Class (Continued) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		$ 48,445	$ 49,404	$ 25,396
Interest Income Recognized	[1]	1,621	1,690	492
Commercial, industrial, and agricultural | Commercial and industrial
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		33,732	33,956	9,178
Interest Income Recognized	[1]	225	1,059	104
Commercial, industrial, and agricultural | Agricultural
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		2,026	279	0
Interest Income Recognized	[1]	32	101	0
Commercial real estate loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		12,688	15,170	16,218
Interest Income Recognized	[1]	1,364	530	388
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		8,105	13,106	12,867
Interest Income Recognized	[1]	892	325	291
Commercial real estate loans | Multi-family
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		2,404	441	479
Interest Income Recognized	[1]	66	28	11
Commercial real estate loans | Construction
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		0	7	63
Interest Income Recognized	[1]	0	136	0
Commercial real estate loans | Other commercial real estate
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		2,179	1,615	2,809
Interest Income Recognized	[1]	$ 406	$ 41	$ 86
[1]	Recorded using the cash basis of accounting.

Past Due Loans, Allowance For_8

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Credit Quality Indicators by Class, Excluding Covered Loans (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Accruing		$ 1,866	$ 1,796
Special mention and substandard loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Accruing		630	657
Commercial, industrial, and agricultural | Commercial and industrial
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		4,120,293	3,529,914
Accruing		246	264
Commercial, industrial, and agricultural | Commercial and industrial | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		3,952,066	3,388,133
Commercial, industrial, and agricultural | Commercial and industrial | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	74,878	70,863
Commercial, industrial, and agricultural | Commercial and industrial | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	59,842	30,338
Commercial, industrial, and agricultural | Commercial and industrial | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	33,507	40,580
Commercial, industrial, and agricultural | Agricultural
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		430,928	430,886
Accruing		0	0
Commercial, industrial, and agricultural | Agricultural | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		407,542	413,946
Commercial, industrial, and agricultural | Agricultural | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	10,070	10,989
Commercial, industrial, and agricultural | Agricultural | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	11,752	5,732
Commercial, industrial, and agricultural | Agricultural | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	1,564	219
Commercial real estate loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		4,596,249	4,553,618
Accruing		738	766
Commercial real estate loans | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		4,399,131	4,395,481
Commercial real estate loans | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	109,232	72,749
Commercial real estate loans | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	75,271	69,621
Commercial real estate loans | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	12,615	15,767
Commercial real estate loans | Office, retail, and industrial
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		1,820,917	1,979,820
Accruing		0	0
Commercial real estate loans | Office, retail, and industrial | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		1,735,426	1,903,737
Commercial real estate loans | Office, retail, and industrial | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	35,853	25,546
Commercial real estate loans | Office, retail, and industrial | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	43,128	38,977
Commercial real estate loans | Office, retail, and industrial | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	6,510	11,560
Commercial real estate loans | Multi-family
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		764,185	675,463
Accruing		557	574
Commercial real estate loans | Multi-family | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		745,131	665,496
Commercial real estate loans | Multi-family | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	9,273	7,395
Commercial real estate loans | Multi-family | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	6,674	2,195
Commercial real estate loans | Multi-family | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	3,107	377
Commercial real estate loans | Construction
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		649,337	539,820
Accruing		0	0
Commercial real estate loans | Construction | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		624,446	521,911
Commercial real estate loans | Construction | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	16,370	10,184
Commercial real estate loans | Construction | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	8,377	7,516
Commercial real estate loans | Construction | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	144	209
Commercial real estate loans | Other commercial real estate
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		1,361,810	1,358,515
Accruing		181	192
Commercial real estate loans | Other commercial real estate | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		1,294,128	1,304,337
Commercial real estate loans | Other commercial real estate | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	47,736	29,624
Commercial real estate loans | Other commercial real estate | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	17,092	20,933
Commercial real estate loans | Other commercial real estate | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	2,854	3,621
Total corporate loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		9,147,470	8,514,418
Accruing		984	1,030
Total corporate loans | Pass
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class		8,758,739	8,197,560
Total corporate loans | Special Mention
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[1],[2]	194,180	154,601
Total corporate loans | Substandard
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[2],[3]	146,865	105,691
Total corporate loans | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans [Line Items
Credit Quality Indicators by Class	[4]	$ 47,686	$ 56,566
[1]	Loans categorized as special mention exhibit potential weaknesses that require the close attention of management since these potential weaknesses may result in the deterioration of repayment prospects in the future.
[2]	Total special mention and substandard loans includes accruing TDRs of $630,000 as of December 31, 2018 and $657,000 as of December 31, 2017.
[3]	Loans categorized as substandard exhibit a well-defined weakness that may jeopardize the liquidation of the debt. These loans continue to accrue interest because they are well-secured and collection of principal and interest is expected within a reasonable time.
[4]	Loans categorized as non-accrual exhibit a well-defined weakness that may jeopardize the liquidation of the debt or result in a loss if the deficiencies are not corrected.

Past Due Loans, Allowance For_9

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) (Details) - Consumer loans - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	$ 2,299,313	$ 1,923,394
Performing
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	2,290,064	1,913,036
Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	9,249	10,358
Home equity
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	851,607	827,055
Home equity | Performing
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	846,214	821,109
Home equity | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	5,393	5,946
1-4 family mortgages
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	1,017,181	774,357
1-4 family mortgages | Performing
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	1,013,325	769,945
1-4 family mortgages | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	3,856	4,412
Installment
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	430,525	321,982
Installment | Performing
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	430,525	321,982
Installment | Non-accrual
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) [Line Items]
Credit Quality Indicators by Class	$ 0	$ 0

Past Due Loans, Allowance Fo_10

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - TDRs By Class (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Accruing		$ 1,866	$ 1,796
Non-accrual	[1]	6,612	24,533
Total		8,478	26,329	$ 8,588
Commercial, industrial, and agricultural | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Accruing		246	264
Non-accrual	[1]	5,994	18,959
Total		6,240	19,223
Commercial, industrial, and agricultural | Agricultural
Financing Receivable, Modifications [Line Items]
Accruing		0	0
Non-accrual	[1]	0	0
Total		0	0
Commercial real estate loans
Financing Receivable, Modifications [Line Items]
Accruing		738	766
Non-accrual	[1]	0	4,385
Total		738	5,151
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Modifications [Line Items]
Accruing		0	0
Non-accrual	[1]	0	4,236
Total		0	4,236
Commercial real estate loans | Multi-family
Financing Receivable, Modifications [Line Items]
Accruing		557	574
Non-accrual	[1]	0	149
Total		557	723
Commercial real estate loans | Construction
Financing Receivable, Modifications [Line Items]
Accruing		0	0
Non-accrual	[1]	0	0
Total		0	0
Commercial real estate loans | Other commercial real estate
Financing Receivable, Modifications [Line Items]
Accruing		181	192
Non-accrual	[1]	0	0
Total		181	192
Total corporate loans
Financing Receivable, Modifications [Line Items]
Accruing		984	1,030
Non-accrual	[1]	5,994	23,344
Total		6,978	24,374
Consumer loans
Financing Receivable, Modifications [Line Items]
Accruing		882	766
Non-accrual	[1]	618	1,189
Total		1,500	1,955
Consumer loans | Home equity
Financing Receivable, Modifications [Line Items]
Accruing		113	86
Non-accrual	[1]	327	738
Total		440	824
Consumer loans | 1-4 family mortgages
Financing Receivable, Modifications [Line Items]
Accruing		769	680
Non-accrual	[1]	291	451
Total		1,060	1,131
Consumer loans | Installment
Financing Receivable, Modifications [Line Items]
Accruing		0	0
Non-accrual	[1]	0	0
Total		$ 0	$ 0
[1]	These TDRs are included in non-accrual loans in the preceding tables.

Past Due Loans, Allowance Fo_11

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - Narrative (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Valuation allowance on TDR loans	$ 0	$ 2,000,000
Commitments to lend additional funds on TDR loans	$ 3,800,000	$ 0

Past Due Loans, Allowance Fo_12

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - TDRs That Were Restructured (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	14	2
Pre-Modification Recorded Investment	$ 30,389	$ 6,205
Funds Disbursed	9,035	0
Interest and Escrow Capitalized	0	0
Charge-offs	6,232	1,083
Post-Modification Recorded Investment	$ 33,192	$ 5,122
Commercial, industrial, and agricultural | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	12
Pre-Modification Recorded Investment	$ 26,733
Funds Disbursed	9,035
Interest and Escrow Capitalized	0
Charge-offs	6,232
Post-Modification Recorded Investment	$ 29,536
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2	1
Pre-Modification Recorded Investment	$ 3,656	$ 5,460
Funds Disbursed	0	0
Interest and Escrow Capitalized	0	0
Charge-offs	0	1,083
Post-Modification Recorded Investment	$ 3,656	$ 4,377
Commercial real estate loans | Other commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans | loan		1
Pre-Modification Recorded Investment		$ 745
Funds Disbursed		0
Interest and Escrow Capitalized		0
Charge-offs		0
Post-Modification Recorded Investment		$ 745

Past Due Loans, Allowance Fo_13

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - TDRs That Defaulted Within Twelve Months of the Restructured Date (Details) - Consumer loans - Home equity $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Financing Receivable, Modifications [Line Items]
Number of Loans	1
Recorded Investment	$ 119

Past Due Loans, Allowance Fo_14

Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs - TDR Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Troubled Debt Restructuring Activity [Roll Forward]
Beginning balance	$ 26,329	$ 8,588
Additions		33,192	$ 5,122
Ending balance	8,478	26,329	8,588
Accruing
Troubled Debt Restructuring Activity [Roll Forward]
Beginning balance	1,796	2,291	2,743
Additions	0	15,819	0
Net payments	(50)	(1,923)	(120)
Returned to performing status	0	0	0
Net transfers from (to) non-accrual	120	(14,391)	(332)
Ending balance	1,866	1,796	2,291
Non-accrual
Troubled Debt Restructuring Activity [Roll Forward]
Beginning balance	24,533	6,297	2,324
Additions	527	14,570	6,205
Net payments	(14,403)	(4,380)	(1,072)
Charge-offs	(3,925)	(6,345)	(1,492)
Transfers to OREO	0	0	0
Loans sold	0	0	0
Net transfers (to) from accruing	(120)	14,391	332
Ending balance	$ 6,612	$ 24,533	$ 6,297

Premises, Furniture, and Equi_3

Premises, Furniture, and Equipment - Premises, Furniture, and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Land	$ 28,187	$ 30,470
Premises	122,003	123,873
Furniture and equipment	127,421	115,013
Total cost	277,611	269,356
Accumulated depreciation	(148,831)	(148,248)
Net book value of premises, furniture, and equipment	128,780	121,108
Assets held-for-sale	3,722	2,208
Premises, furniture, and equipment, net	$ 132,502	$ 123,316

Premises, Furniture, and Equi_4

Premises, Furniture, and Equipment - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)retail_branch
Property, Plant and Equipment [Abstract]
Number of branches sold | retail_branch			55
Pre-tax gain on sale-leaseback transaction			$ 88,000
Net gain on sale-leaseback transaction	$ 0	$ 0	5,509
Deferred gain, net	65,500	74,600
Depreciation of premises, furniture, and equipment	$ 15,865	$ 13,995	$ 12,804

Premises, Furniture, and Equi_5

Premises, Furniture, and Equipment - Future Minimum Operating Lease Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Property, Plant and Equipment [Abstract]
2,019	$ 15,811
2,020	16,780
2,021	16,976
2,022	16,967
2,023	17,100
2024 and thereafter	117,806
Total minimum lease payments	$ 201,440

Premises, Furniture, and Equi_6

Premises, Furniture, and Equipment - Accretion of Operating Leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Property, Plant and Equipment [Abstract]
2,019	$ 648
2,020	648
2,021	648
2,022	639
2,023	612
2024 and thereafter	2,745
Total accretion	$ 5,940

Premises, Furniture, and Equi_7

Premises, Furniture, and Equipment - Rental Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Lease expense charged to operations		$ 24,880	$ 18,666	$ 11,207
Accretion of operating lease intangible	[1]	(972)	(1,180)	(1,171)
Accretion of deferred gain on sale-leaseback transaction	[1]	(9,126)	(5,872)	(1,473)
Rental income from premises leased to others	[1]	(510)	(682)	(527)
Net operating lease expense		$ 14,272	$ 10,932	$ 8,036
[1]	Included as reductions to net occupancy and equipment expense in the Consolidated Statements of Income.

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning balance	$ 697,608	$ 340,879	$ 319,007
Acquisitions	31,201	356,729	21,872
Ending balance	$ 728,809	$ 697,608	$ 340,879

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-lived Intangible Assets [Roll Forward]
Balance at the beginning of the year, gross	$ 97,976	$ 58,959	$ 48,550
Balance at the beginning of the year, accumulated amortization	40,827	32,962	28,280
Balance at the beginning of the year, net	57,149	25,997	20,270
Additions	12,230	39,017	10,409
Amortization expense	(7,444)	(7,865)	(4,682)
Balance at the end of the year, gross	110,206	97,976	58,959
Balance at the end of the year, accumulated amortization	48,271	40,827	32,962
Balance at the end of the year, net	$ 61,935	$ 57,149	$ 25,997
Weighted-average remaining life (in years)	7 years 10 months	8 years 4 months	7 years 6 months 20 days
Minimum
Finite-lived Intangible Assets [Roll Forward]
Estimated useful lives (in years)	8 months	2 months	7 months
Maximum
Finite-lived Intangible Assets [Roll Forward]
Estimated useful lives (in years)	9 years 10 months	9 years 3 months	9 years 3 months

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Amortization of Other Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
2,019	$ 8,296
2,020	8,246
2,021	8,170
2,022	8,090
2,023	7,713
2024 and thereafter	21,420
Total	$ 61,935	$ 57,149	$ 25,997	$ 20,270

Deposits - Summary of Deposits

Deposits - Summary of Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deposits [Abstract]
Demand deposits	$ 3,642,989	$ 3,576,190
Savings deposits	2,053,494	2,011,999
NOW accounts	2,063,213	1,962,304
Money market deposits	1,783,512	1,856,049
Time deposits less than $100,000	1,348,664	904,882
Time deposits greater than $100,000	1,192,240	741,901
Total deposits	$ 12,084,112	$ 11,053,325

Deposits - Maturities of Time

Deposits - Maturities of Time Deposits (Details) $ in Thousands	Dec. 31, 2018USD ($)
Maturities of Time Deposits [Abstract]
2,019	$ 1,907,914
2,020	535,237
2,021	60,897
2,022	19,380
2,023	17,299
2024 and thereafter	177
Total	$ 2,540,904

Borrowed Funds - Summary of Bo

Borrowed Funds - Summary of Borrowed Funds (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Securities sold under agreements to repurchase	$ 121,079	$ 124,884
FHLB advances	785,000	590,000
Total borrowed funds	$ 906,079	$ 714,884

Borrowed Funds - Narrative (De

Borrowed Funds - Narrative (Details) - USD ($)	Sep. 27, 2016	Dec. 31, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Line of credit maximum borrowing capacity	$ 50,000,000
Line of credit unused facility fee	0.35%
Line of credit amount outstanding		$ 0	$ 0
One-Month LIBOR Plus 1.75%
Short-term Debt [Line Items]
Line of credit interest rate spread	1.75%
FHLB Advances
Short-term Debt [Line Items]
FHLB maturity date range, start		Jan. 2, 2019
FHLB maturity date range, end		Mar. 1, 2019
FHLB Advances | Minimum
Short-term Debt [Line Items]
FHLB fixed interest rate		2.51%
FHLB Advances | Maximum
Short-term Debt [Line Items]
FHLB fixed interest rate		2.58%

Borrowed Funds - Short-Term Cr

Borrowed Funds - Short-Term Credit Lines Available for Use (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
FRBs Discount Window Primary Credit Program
Line of Credit Facility [Line Items]
Amount outstanding	$ 881,113	$ 843,618
Available federal funds lines
Line of Credit Facility [Line Items]
Amount outstanding	684,000	667,000
Correspondent bank line of credit
Line of Credit Facility [Line Items]
Amount outstanding	$ 50,000	$ 50,000

Senior and Subordinated Debt -

Senior and Subordinated Debt - Schedule of Senior and Subordinated Debt (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total junior subordinated debentures		$ 56,526	$ 48,243
Senior and subordinated debt		203,808	195,170
Debt instrument, unamortized discount		6,000
GLST II and GLST III
Debt Instrument [Line Items]
Debt instrument, unamortized discount			4,000
Subordinated notes due in 2026
Debt Instrument [Line Items]
Subordinated notes		$ 147,282	146,927
Issuance date		Sep. 29, 2016
Maturity date		Sep. 29, 2026
Interest rate		5.875%
Junior Subordinated Debentures, First Midwest Capital Trust I | First Midwest Capital Trust I (FMCT)
Debt Instrument [Line Items]
Total junior subordinated debentures		$ 37,803	37,801
Issuance date		Nov. 11, 2003
Maturity date		Dec. 1, 2033
Interest rate		6.95%
Junior Subordinated Debentures, Great Lakes Statutory Trust II | Great Lakes Statutory Trust II (GLST II)
Debt Instrument [Line Items]
Total junior subordinated debentures	[1]	$ 4,580	$ 4,486
Issuance date	[1]	Dec. 15, 2005
Maturity date	[1]	Dec. 15, 2035
Basis spread on variable interest rate	[1],[2]	1.40%	1.40%
Junior Subordinated Debentures, Great Lakes Statutory Trust III | Great Lakes Statutory Trust III (GLST III)
Debt Instrument [Line Items]
Total junior subordinated debentures	[1]	$ 6,071	$ 5,956
Issuance date	[1]	Jun. 15, 2007
Maturity date	[1]	Sep. 15, 2037
Basis spread on variable interest rate	[1],[2]	1.70%	1.70%
Junior Subordinated Debentures, Northern States Statutory Trust I | Northern States Statutory Trust I (NSST I)
Debt Instrument [Line Items]
Total junior subordinated debentures	[1]	$ 8,072	$ 0
Issuance date	[1]	Sep. 7, 2005
Maturity date	[1]	Oct. 7, 2035
Basis spread on variable interest rate	[1],[2]	1.80%
[1]	The junior subordinated debentures related to GLST II, GLST III, and NSST I were assumed by the Company through acquisitions. These amounts include acquisition adjustment discounts that total $6.0 million and $4.0 million as of December 31, 2018 and 2017, respectively.
[2]	The interest rates are a variable rate, based on three-month LIBOR plus 1.400%, 1.700% and $1.800% for GLST II, GLST III, and NSST I, respectively.

Material Transactions Affecti_2

Material Transactions Affecting Stockholders' Equity (Details) - $ / shares	Oct. 12, 2018	May 17, 2017	Jan. 06, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01				$ 0.01
Common stock, increase shares authorized (in shares)		100,000,000
Common stock and preferred stock, shares authorized (in shares)		251,000,000
Preferred stock, shares authorized (in shares)		1,000,000		1,000,000				1,000,000
Common stock, shares authorized (in shares)		250,000,000		250,000,000				250,000,000
Common dividends declared per common share (in dollars per share)				$ 0.12	$ 0.11	$ 0.11	$ 0.11	$ 0.10	$ 0.10	$ 0.10	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09
Northern States Financial Corporation
Class of Stock [Line Items]
Common stock, shares issued (in shares)	3,310,912
Shares issued (in dollars per share)	$ 25.16
Standard Bancshares, Inc.
Class of Stock [Line Items]
Common stock, shares issued (in shares)			21,057,085
Shares issued (in dollars per share)			$ 25.34

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income		$ 157,870	$ 98,387	$ 92,349
Net income applicable to non-vested restricted shares		(1,312)	(916)	(1,043)
Net income applicable to common shares		$ 156,558	$ 97,471	$ 91,306
Weighted-average common shares outstanding:
Weighted-average common shares outstanding (basic) (in shares)		102,850	101,423	79,797
Dilutive effect of common stock equivalents (in shares)		4	20	13
Weighted-average diluted common shares outstanding (in shares)		102,854	101,443	79,810
Basic EPS (in dollars per share)		$ 1.52	$ 0.96	$ 1.14
Diluted EPS (in dollars per share)		$ 1.52	$ 0.96	$ 1.14
Anti-dilutive shares not included in the computation of diluted EPS (in shares)	[1]	27	229	494
[1]	This amount represents outstanding stock options for which the exercise price is greater than the average market price of the Company's common stock. The final outstanding stock options were exercised during the first quarter of 2018.

Income Taxes - Components of I

Income Taxes - Components of Income Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current income tax expense (benefit):
Federal	$ 13,497	$ 93,540	$ 46,748
State	(619)	104	790
Total	12,878	93,644	47,538
Deferred income tax expense (benefit):
Federal	14,489	(12,219)	(7,786)
State	11,820	8,142	6,419
Total	26,309	(4,077)	(1,367)
Total income tax expense	$ 39,187	$ 89,567	$ 46,171

Income Taxes - Narrative (Deta

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Revaluation of deferred tax assets			$ 8,721	$ (23,709)	$ 0
Acquired thrift's tax bad debt reserve	$ 2,500		5,800	2,500	2,500
Deferred tax assets, net	64,736		60,129	64,736
Unrecognized tax benefit that would affect effective tax rate	12,900		13,100	12,900	$ 1,400
Northern States Financial Corporation
Income Taxes [Line Items]
Deferred tax assets, net			17,000
Standard Bancshares and NI Bancshares Acquisitions
Income Taxes [Line Items]
Deferred tax assets, net	41,500			41,500
Federal
Income Taxes [Line Items]
Revaluation of deferred tax assets	$ 26,600		$ 8,700	(26,600)
State and Local Jurisdiction
Income Taxes [Line Items]
Revaluation of deferred tax assets		$ 2,800		$ 2,800

Income Taxes - Components of E

Income Taxes - Components of Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amount
Statutory federal income tax	$ 41,382	$ 65,784	$ 48,482
Deferred tax asset revaluation	(8,721)	23,709	0
Tax-exempt income, net of interest expense disallowance	(3,104)	(5,065)	(5,439)
State income tax, net of federal income tax effect	8,846	5,069	4,323
Other	784	70	(1,195)
Total income tax expense	$ 39,187	$ 89,567	$ 46,171
% of Pretax Income
Statutory federal income tax rate (percent of pretax income)	21.00%	35.00%	35.00%
Revaluation of deferred tax assets (percent of pretax income)	(4.40%)	12.60%	0.00%
Tax-exempt income, net of interest expense disallowance (percent of pretax income)	(1.60%)	(2.70%)	(3.90%)
State income tax, net of federal income tax effect (percent of pretax income)	4.50%	2.70%	3.10%
Other (percent of pretax income)	0.40%	0.10%	(0.90%)
Effective tax rate	19.90%	47.70%	33.30%

Income Taxes - Deferred Tax As

Income Taxes - Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Allowance for credit losses	$ 19,591	$ 20,285
Deferred gain on sale-leaseback transaction	13,752	15,668
Federal net operating loss (NOL) carryforwards	8,871	0
Equity based compensation	3,971	3,605
State NOL carryforwards	3,293	3,384
Non-equity based compensation	2,210	897
OREO	1,460	2,089
Deferred incentives	1,382	29
Property valuation adjustments	1,214	69
AMT and other credit carryforwards	244	667
Other	8,179	12,419
Total deferred tax assets	64,167	59,112
Deferred tax liabilities:
Accrued retirement benefits	(8,502)	(3,517)
Fixed assets	(7,322)	(1,660)
Deferred loan fees and costs	(4,985)	(4,169)
Cancellation of indebtedness income	0	(641)
Acquisition adjustments	(686)	2,489
Other	(2,823)	(2,449)
Total deferred tax liabilities	(24,318)	(9,947)
Deferred tax valuation allowance	0	0
Net deferred tax assets	39,849	49,165
Tax effect of adjustments related to other comprehensive (loss) income	20,280	15,571
Net deferred tax assets including adjustments	60,129	64,736
NOL carryforwards available to offset future taxable income:
AMT credits	0	410
Internal Revenue Service (IRS)
NOL carryforwards available to offset future taxable income:
Gross NOL Carryforwards	42,242	0
Illinois
NOL carryforwards available to offset future taxable income:
Gross NOL Carryforwards	209,802	188,995
Indiana
NOL carryforwards available to offset future taxable income:
Gross NOL Carryforwards	14,260	16,174
Wisconsin
NOL carryforwards available to offset future taxable income:
Gross NOL Carryforwards	$ 1,212	$ 0

Income Taxes - Rollforward of

Income Taxes - Rollforward of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance		$ 16,248	$ 2,039	$ 1,408
Additions for tax positions relating to the current year		1,209	845	640
Additions for tax positions relating to prior years		582	13,389	0
Reductions for tax positions relating to prior years		(60)	(25)	(9)
Reductions for settlements with taxing authorities		(1,629)	0	0
Ending balance		16,350	16,248	2,039
Interest and penalties not included above:
Interest expense, net of tax effect, and penalties	[1]	(21)	118	49
Accrued interest and penalties, net of tax effect, at end of year	[1]	$ 170	$ 191	$ 73
[1]	Included in income tax expense in the Consolidated Statements of Income.

Employee Benefit Plans - Narra

Employee Benefit Plans - Narrative (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined contribution plan, employer matching contribution percent of employee's compensation	4.00%
Defined contribution plan, discretionary contribution vesting period	6 years
Actuarial losses as a percentage of accumulated benefit obligation	50.40%	37.50%
Pension Plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Actuarial losses as a percentage of accumulated benefit obligation	10.00%
Contributions
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined contribution plan, employee contribution limit, percentage of compensation	100.00%
Voluntary 401K Plans
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined contribution plan, employer automatic contribution limit	2.00%
Deferred Profit Sharing
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined contribution plan, employer automatic contribution limit	15.00%

Employee Benefit Plans - Profi

Employee Benefit Plans - Profit Sharing Plan (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]
Profit sharing expense		$ 43,104	$ 41,886	$ 33,309
Profit Sharing Expense
Defined Contribution Plan Disclosure [Line Items]
Profit sharing expense	[1]	7,803	7,346	6,171
Company dividends received by the Profit Sharing Plan		$ 457	$ 441	$ 494
Company shares held by the Profit Sharing Plan at the end of the year:
Number of shares		1,047,213	1,079,975	1,175,858
Fair value		$ 20,745	$ 25,930	$ 29,667
[1]	Included in retirement and other employee benefits in the Consolidated Statements of Income.

Employee Benefit Plans - Pensi

Employee Benefit Plans - Pension Plan Cost and Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Accumulated benefit obligation	$ 58,271		$ 67,923
Change in projected benefit obligation
Beginning balance	67,923		68,959
Service cost	0		0
Interest cost	2,031		1,712	$ 1,635
Settlements	(7,199)		(6,271)
Actuarial (gain) loss	(3,717)		4,240
Benefits paid	(767)		(717)
Ending balance	58,271		67,923	68,959
Change in fair value of plan assets
Beginning balance	66,159		65,189
Actual return on plan assets	(6,983)		7,958
Benefits paid	(767)		(717)
Employer contributions	25,000		0
Settlements	(7,199)		(6,271)
Ending balance	76,210	[1]	66,159	$ 65,189
Funded status recognized in the Consolidated Statements of Financial Condition
Noncurrent asset (liability)	17,939
Noncurrent asset (liability)			(1,764)
Amounts recognized in accumulated other comprehensive loss
Prior service cost	0		0
Net loss	29,345		25,495
Net amount recognized	$ 29,345		$ 25,495
Actuarial losses included in accumulated other comprehensive loss as a percent of
Accumulated benefit obligation	50.40%		37.50%
Fair value of plan assets	38.50%		38.50%
Amounts expected to be amortized from accumulated other comprehensive loss into net periodic benefit cost in the next fiscal year
Prior service cost	$ 0		$ 0
Net loss	426		561
Net amount expected to be recognized	$ 426		$ 561
Weighted-average assumptions at the end of the year used to determine the actuarial present value of the projected benefit obligation
Discount rate	4.10%		3.45%
[1]	Additional information regarding the fair value of Pension Plan assets as of December 31, 2018 can be found in Note 21, "Fair Value."

Employee Benefit Plans - Net P

Employee Benefit Plans - Net Periodic Benefit Pension Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of net periodic benefit cost
Interest cost	$ 2,031	$ 1,712	$ 1,635
Expected return on plan assets	(3,820)	(3,802)	(4,057)
Recognized net actuarial loss	533	591	571
Amortization of prior service cost	0	0	0
Recognized settlement loss	2,703	2,480	1,338
Net periodic cost (income)	1,447	981	(513)
Other changes in plan assets and benefit obligations recognized as a charge to other comprehensive (loss) income
Net loss for the period	(7,086)	(83)	(3,911)
Amortization of net loss	3,236	3,071	1,909
Total unrealized (loss) gain	(3,850)	2,988	(2,002)
Total recognized in net periodic pension cost and other comprehensive (loss) income	$ (5,297)	$ 2,007	$ (1,489)
Weighted-average assumptions used to determine the net periodic cost
Discount rate	3.45%	3.86%	3.99%
Expected return on plan assets	5.75%	6.25%	6.50%

Employee Benefit Plans - Pen_2

Employee Benefit Plans - Pension Plan Asset Allocation (Details) - USD ($) $ in Thousands		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Asset Category
Fair Value of Plan Assets (in dollars)		$ 76,210	[1]	$ 66,159	$ 65,189
Percentage of Plan Assets		100.00%		100.00%
Equity securities
Asset Category
Fair Value of Plan Assets (in dollars)	[1]	$ 46,772
Percentage of Plan Assets		61.00%		60.00%
Fixed income
Asset Category
Fair Value of Plan Assets (in dollars)	[1]	$ 27,887
Percentage of Plan Assets		37.00%		35.00%
Cash equivalents
Asset Category
Fair Value of Plan Assets (in dollars)	[1]	$ 1,551
Percentage of Plan Assets		2.00%		5.00%
Minimum | Equity securities
Asset Category
Target plan asset allocations		50.00%
Minimum | Fixed income
Asset Category
Target plan asset allocations		30.00%
Minimum | Cash equivalents
Asset Category
Target plan asset allocations		2.00%
Maximum | Equity securities
Asset Category
Target plan asset allocations		60.00%
Maximum | Fixed income
Asset Category
Target plan asset allocations		48.00%
Maximum | Cash equivalents
Asset Category
Target plan asset allocations		10.00%
[1]	Additional information regarding the fair value of Pension Plan assets as of December 31, 2018 can be found in Note 21, "Fair Value."

Employee Benefit Plans - Estim

Employee Benefit Plans - Estimated Future Pension Benefit Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Retirement Benefits [Abstract]
2,019	$ 5,589
2,020	5,000
2,021	4,681
2,022	4,978
2,023	3,827
2024-2027	$ 19,488

Share-Based Compensation - Nar

Share-Based Compensation - Narrative (Details) - shares	May 17, 2017	May 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, increase shares authorized (in shares)	100,000,000
Stock options exercised in period (in shares)			42,000
2018 Stock and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, increase shares authorized (in shares)		2,000,000
Directors Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			14,000	16,000
Nonqualified Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted in period (in shares)			0	0	0
Stock options exercised in period (in shares)			0	0	0
Restricted Stock And Restricted Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Granted (in shares)			427,000
Restricted Stock And Restricted Stock Unit Awards | Vesting After Two Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage			50.00%
Restricted Stock And Restricted Stock Unit Awards | Vesting After Three Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage			50.00%
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of internal and external performance metric analysis			3 years
Metric weighting (percent)			50.00%
Granted (in shares)			133,000
Performance Shares | Vesting After Three Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage			33.33%
Performance Shares | Vesting After Fourth Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage			33.33%
Performance Shares | Vesting After Fifth Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage			33.33%
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares earned of those granted based on performance			0.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares earned of those granted based on performance			200.00%

Share-Based Compensation - Sha

Share-Based Compensation - Shares of Common Stock Available Under Share-Based Plans (Details)	Dec. 31, 2018shares
2018 Stock and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Authorized (in shares)	3,254,706
Shares Available For Grant (in shares)	3,223,548
Directors Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Authorized (in shares)	481,250
Shares Available For Grant (in shares)	116,532

Share-Based Compensation - Non

Share-Based Compensation - Nonqualified Stock Option Transactions (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Number of Options
Options outstanding beginning balance (in shares) | shares	232
Exercised (in shares) | shares	(42)
Expired (in shares) | shares	(190)
Options outstanding ending balance (in shares) | shares	0
Weighted Average Exercise Price
Options outstanding beginning balance (in dollars per share) | $ / shares	$ 25.19
Exercised (in dollars per share) | $ / shares	12.17
Expired (in dollars per share) | $ / shares	28.10
Options outstanding ending balance (in dollars per share) | $ / shares	$ 0

Share-Based Compensation - Res

Share-Based Compensation - Restricted Stock Award Transactions (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Restricted Stock/Unit Awards
Number of Shares/Units
Non-vested awards at beginning of year (in shares) | shares	1,053
Granted (in shares) | shares	427
Vested (in shares) | shares	(454)
Forfeited (in shares) | shares	(79)
Non-vested awards at end of year (in shares) | shares	947
Weighted Average Grant Date Fair Value
Non-vested awards at beginning of year (in dollars per share) | $ / shares	$ 20.36
Granted (in dollars per share) | $ / shares	24.96
Vested (in dollars per share) | $ / shares	17.54
Forfeited (in dollars per share) | $ / shares	22.86
Non-vested awards at end of year (in dollars per share) | $ / shares	$ 23.32
Performance Shares
Number of Shares/Units
Non-vested awards at beginning of year (in shares) | shares	466
Granted (in shares) | shares	133
Vested (in shares) | shares	(97)
Forfeited (in shares) | shares	(34)
Non-vested awards at end of year (in shares) | shares	468
Weighted Average Grant Date Fair Value
Non-vested awards at beginning of year (in dollars per share) | $ / shares	$ 18.16
Granted (in dollars per share) | $ / shares	24.96
Vested (in dollars per share) | $ / shares	17.54
Forfeited (in dollars per share) | $ / shares	22.86
Non-vested awards at end of year (in dollars per share) | $ / shares	$ 19.88

Share-Based Compensation - Oth

Share-Based Compensation - Other Restricted Stock Award/Unit Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit realized from the vesting/release of restricted stock, restricted stock unit, and performance share awards	$ 3,365	$ 4,601	$ 3,152
Restricted Stock Restricted Stock Unit and Performance Share Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of restricted stock, restricted stock unit, and performance share awards granted during the year (in dollars per share)	$ 24.96	$ 24.71	$ 17.28
Total fair value of restricted stock, restricted stock unit, and performance share awards vested during the year	$ 10,870	$ 13,760	$ 12,231
Income tax benefit realized from the vesting/release of restricted stock, restricted stock unit, and performance share awards	$ 2,970	$ 4,007	$ 2,529

Share-Based Compensation - Eff

Share-Based Compensation - Effect of Recording Share-Based Compensation Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based compensation expense	[1]	$ 12,062	$ 11,223	$ 7,879
Income tax benefit		3,365	4,601	3,152
Share-based compensation expense, net of tax		8,697	6,622	4,727
Unrecognized compensation expense		$ 13,982	$ 13,266	$ 9,990
Weighted-average amortization period remaining (in years)		1 year 2 months 13 days	1 year 3 months 10 days	1 year 4 months
[1]	Comprised of restricted stock, restricted stock unit, and performance share awards expense.

Regulatory and Capital Matter_2

Regulatory and Capital Matters - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash reserve balance	$ 149,200,000	$ 121,000,000
Adjustment to available dividends	149,900,000
Regulatory capital requirements under banking regulations, inclusion of trust-preferred securities in Tier One capital calculation (less than)	15,000,000,000
Trust-preferred securities included in Tier 2 capital	$ 60,700,000
Tier 1 risk based capital conservation buffer initial requirements phasing duration	4 years
Implementation of deductions and other adjustments to CET1, percentage			40.00%
Implementation of deductions and other adjustments to CET1 additional, percentage	20.00%
Risk weighted threshold of items deducted from CET1 capital	10.00%
Aggregate risk weighted threshold of items deducted from CET1	15.00%
January 2,019
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum ratio of CET1 to risk-weighted assets	4.50%
Capital conservation buffer	2.50%
Resulting minimum ratio of CET1 to risk-weighted assets after capital conversion buffer	7.00%
Minimum ratio of Tier 1 capital to risk-weighted assets	6.00%
Minimum ratio of Tier 1 capital to risk-weighted assets, adjusted	8.50%
Minimum ratio of Total capital to risk-weighted assets	8.00%
Minimum ratio of Total capital to risk-weighted assets, adjusted	10.50%
Minimum leverage ratio	4.00%

Regulatory and Capital Matter_3

Regulatory and Capital Matters - Summary of Capital Ratios (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
First Midwest Bancorp, Inc.
Total capital to risk-weighted assets:
Actual Capital	$ 1,626,489,000	$ 1,448,124,000
Actual Ratio (percent)	12.62%	12.15%
Adequately Capitalized Capital	$ 1,273,103,000	$ 1,102,634,000
Adequately Capitalized Ratio (percent)	9.875%	9.25%
Tier 1 capital to risk-weighted assets:
Actual Capital	$ 1,315,098,000	$ 1,204,468,000
Actual Ratio (percent)	10.20%	10.10%
Adequately Capitalized Capital	$ 1,015,259,000	$ 864,227,000
Adequately Capitalized Ratio (percent)	7.875%	7.25%
CET1 to risk-weighted assets:
Actual Capital	$ 1,315,432,000	$ 1,153,939,000
Actual Ratio (percent)	10.20%	9.68%
Adequately Capitalized Capital	$ 821,876,000	$ 685,421,000
Adequately Capitalized Ratio (percent)	6.375%	5.75%
Tier 1 capital to average assets:
Actual Capital	$ 1,315,098,000	$ 1,204,468,000
Actual Ratio (percent)	8.90%	8.99%
Adequately Capitalized Capital	$ 591,293,000	$ 536,200,000
Adequately Capitalized Ratio (percent)	4.00%	4.00%
First Midwest Bank
Total capital to risk-weighted assets:
Actual Capital	$ 1,463,026,000	$ 1,300,809,000
Actual Ratio (percent)	11.39%	10.95%
Adequately Capitalized Capital	$ 1,268,662,000	$ 1,099,133,000
Adequately Capitalized Ratio (percent)	9.875%	9.25%
To Be Well-Capitalized Under Prompt Corrective Action Provisions Capital	$ 1,284,721,000	$ 1,188,252,000
To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio (percent)	10.00%	10.00%
Tier 1 capital to risk-weighted assets:
Actual Capital	$ 1,359,607,000	$ 1,204,080,000
Actual Ratio (percent)	10.58%	10.13%
Adequately Capitalized Capital	$ 1,011,718,000	$ 861,482,000
Adequately Capitalized Ratio (percent)	7.875%	7.25%
To Be Well-Capitalized Under Prompt Corrective Action Provisions Capital	$ 1,027,777,000	$ 950,601,000
To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio (percent)	8.00%	8.00%
CET1 to risk-weighted assets:
Actual Capital	$ 1,359,607,000	$ 1,204,080,000
Actual Ratio (percent)	10.58%	10.13%
Adequately Capitalized Capital	$ 819,009,000	$ 683,245,000
Adequately Capitalized Ratio (percent)	6.375%	5.75%
To be Well-Capitalized Under Prompt Corrective Action Provisions Capital	$ 835,068,000	$ 772,364,000
To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio ( percent)	6.50%	6.50%
Tier 1 capital to average assets:
Actual Capital	$ 1,359,607,000	$ 1,204,080,000
Actual Ratio (percent)	9.41%	9.10%
Adequately Capitalized Capital	$ 577,991,000	$ 529,147,000
Adequately Capitalized Ratio (percent)	4.00%	4.00%
To Be Well-Capitalized Under Prompt Corrective Action Provisions Capital	$ 722,488,000	$ 661,434,000
To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio (percent)	5.00%	5.00%

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities - Fair Value Hedges (Details) - Fair Value Hedging $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross notional amount outstanding	$ 5,458
Derivative liability fair value in other liabilities	$ (101)
Weighted-average interest rate received	3.38%
Weighted-average interest rate paid	5.96%
Weighted-average maturity (in years)	10 months 4 days
Fair value of derivative	$ 110	[1]
[1]	This amount represents the fair value if credit risk related contingent features were triggered.

Derivative Instruments and He_4

Derivative Instruments and Hedging Activities - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount hedged of borrowed funds using forward starting interest rate swaps	$ 740,000
Amount to be hedged of borrowed funds using forward staring interest rate swaps	$ 400,000
Weighted-average interest rate to be paid	2.53%
Interest rate cash flow hedge to be reclassified during next 12 months, net	$ 1,800
Capital market products income	$ 7,721	$ 8,171	$ 10,024
Portion of fair value outstanding, interest rate swaps covered by collateral agreements (percent)	100.00%	100.00%
Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of variable rate loans hedged using interest rate swaps	$ 1,100,000
Amount hedged of borrowed funds using forward starting interest rate swaps	$ 1,100,000

Derivative Instruments and He_5

Derivative Instruments and Hedging Activities - Cash Flow Hedges (Details) - Cash Flow Hedging - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross notional amount outstanding		$ 2,280,000	$ 1,960,000
Derivative asset fair value in other assets	[1]	6,889	3,989
Derivative liability fair value in other liabilities	[1]	$ (11,328)	$ (10,219)
Weighted-average interest rate received		2.12%	1.58%
Weighted-average interest rate paid		2.20%	1.61%
Weighted-average maturity (in years)		1 year 6 months 10 days	2 years 2 months 30 days
[1]	Certain cash flow hedges are transacted through a clearinghouse ("centrally cleared") and their change in fair value is settled by the counterparties to the transaction, which results in no fair value.

Derivative Instruments and He_6

Derivative Instruments and Hedging Activities - Other Derivative Instruments (Details) - Other Derivative Instruments - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Gross notional amount outstanding		$ 3,085,226	$ 2,665,358
Derivative asset fair value in other assets	[1]	25,168	17,079
Derivative liability fair value in other liabilities	[1]	(17,533)	(14,930)
Fair value of derivative	[2]	$ 18,013	$ 15,059
[1]	Certain other derivative instruments are centrally cleared and their change in fair value is settled by the counterparties to the transaction, which resuts in no fair value.
[2]	This amount represents the fair value if credit risk related contingent factors were triggered.

Derivative Instruments and He_7

Derivative Instruments and Hedging Activities - Cash Flow Hedge Accounting on AOCI (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest Income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in other comprehensive income	$ 18,776	$ 11,150	$ (4,674)
Reclassification of gains (losses) included in net income	2,611	5,159	7,641
Interest Expense
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in other comprehensive income	(20,500)	(8,025)	(1,068)
Reclassification of gains (losses) included in net income	$ (3,673)	$ (3,951)	$ (4,074)

Derivative Instruments and He_8

Derivative Instruments and Hedging Activities - Effect of Derivatives on Interest Income (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
(Loss) gain on derivative, net	$ (1,154)	$ 1,041	$ 3,154
Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
(Loss) gain on derivative, net	(1,062)	1,208	3,567
Interest Income | Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
(Loss) gain on derivative, net	(92)	(167)	(413)
Interest Income | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
(Loss) gain on derivative, net	2,611	5,159	7,641
Interest Expense | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
(Loss) gain on derivative, net	$ (3,673)	$ (3,951)	$ (4,074)

Derivative Instruments and He_9

Derivative Instruments and Hedging Activities - Offsetting Derivatives (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Assets
Gross amounts recognized		$ 32,057	$ 21,068
Less: amounts offset in the Consolidated Statements of Financial Condition		0	0
Net amount presented in the Consolidated Statements of Financial Condition	[1]	32,057	21,068
Offsetting derivative positions		(11,678)	(16,880)
Cash collateral pledged		(9,060)	0
Net credit exposure		11,319	4,188
Liabilities
Gross amounts recognized		28,861	25,250
Less: amounts offset in the Consolidated Statements of Financial Condition		0	0
Net amount presented in the Consolidated Statements of Financial Condition	[1]	28,861	25,250
Offsetting derivative positions		(11,678)	(16,880)
Cash collateral pledged		(3,506)	(8,370)
Net credit exposure		$ 13,677	$ 0
[1]	Included in other assets or other liabilities in the Consolidated Statements of Financial Condition.

Commitments, Guarantees, and _3

Commitments, Guarantees, and Contingent Liabilities (Details) - Contractual or Notional Amounts of Financial Instruments - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Commitments to extend credit:
Letters of credit		$ 112,728	$ 128,801
Commitments to extend credit
Commitments to extend credit:
Commercial, industrial, and agricultural		1,729,286	1,729,426
Commercial real estate		296,882	377,551
Home equity		570,553	514,973
Other commitments	[1]	244,917	244,222
Total commitments to extend credit		$ 2,841,638	$ 2,866,172
[1]	Other commitments includes installment and overdraft protection program commitments.

Fair Value - Recurring Fair Va

Fair Value - Recurring Fair Value Measurements (Details) - USD ($) $ in Thousands		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	[2]	Dec. 31, 2015
Trading securities:
Total trading securities		$ 0		$ 20,447	[1]
Equity securities, at fair value		30,806		0
Securities available-for-sale:
Securities available-for-sale, at fair value		2,272,009
Securities available-for-sale, at fair value				1,884,209
Mortgage servicing rights (MSRs)		6,730	[2]	5,894	[2]	$ 6,120		$ 1,853
U.S. treasury securities
Securities available-for-sale:
Securities available-for-sale, at fair value		37,767
Securities available-for-sale, at fair value				46,345
U.S. agency securities
Securities available-for-sale:
Securities available-for-sale, at fair value		142,563
Securities available-for-sale, at fair value				156,847
CMOs
Securities available-for-sale:
Securities available-for-sale, at fair value		1,315,209
Securities available-for-sale, at fair value				1,095,186
MBSs
Securities available-for-sale:
Securities available-for-sale, at fair value		466,934
Securities available-for-sale, at fair value				369,543
Municipal securities
Securities available-for-sale:
Securities available-for-sale, at fair value		227,187
Securities available-for-sale, at fair value				208,991
Corporate debt securities
Securities available-for-sale:
Securities available-for-sale, at fair value		82,349
Securities available-for-sale, at fair value				0
Equity securities
Trading securities:
Equity securities, at fair value	[1]	30,806
Securities available-for-sale:
Securities available-for-sale, at fair value	[1]			7,297
Recurring | Level 1
Trading securities:
Money market funds		0		1,685
Mutual funds		0		18,762
Total trading securities	[3]	0		20,447
Equity securities, at fair value	[3]	19,658		0
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	37,767
Securities available-for-sale, at fair value	[3]			46,345
Mortgage servicing rights (MSRs)	[4]	0		0
Derivative assets	[4]	0		0
Liabilities
Derivative liabilities	[5]	0		0
Recurring | Level 1 | U.S. treasury securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	37,767
Securities available-for-sale, at fair value	[3]			46,345
Recurring | Level 1 | U.S. agency securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 1 | CMOs
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 1 | MBSs
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 1 | Municipal securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 1 | Corporate debt securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 1 | Equity securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 2
Trading securities:
Money market funds		0		0
Mutual funds		0		0
Total trading securities	[3]	0		0
Equity securities, at fair value	[3]	11,148		0
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	2,234,242
Securities available-for-sale, at fair value	[3]			1,837,864
Mortgage servicing rights (MSRs)	[4]	0		0
Derivative assets	[4]	32,057		21,068
Liabilities
Derivative liabilities	[5]	28,861		25,250
Recurring | Level 2 | U.S. treasury securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 2 | U.S. agency securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	142,563
Securities available-for-sale, at fair value	[3]			156,847
Recurring | Level 2 | CMOs
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	1,315,209
Securities available-for-sale, at fair value	[3]			1,095,186
Recurring | Level 2 | MBSs
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	466,934
Securities available-for-sale, at fair value	[3]			369,543
Recurring | Level 2 | Municipal securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	227,187
Securities available-for-sale, at fair value	[3]			208,991
Recurring | Level 2 | Corporate debt securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	82,349
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 2 | Equity securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]			7,297
Recurring | Level 3
Trading securities:
Money market funds		0		0
Mutual funds		0		0
Total trading securities	[3]	0		0
Equity securities, at fair value	[3]	0		0
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Mortgage servicing rights (MSRs)	[4]	6,730		5,894
Derivative assets	[4]	0		0
Liabilities
Derivative liabilities	[5]	0		0
Recurring | Level 3 | U.S. treasury securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 3 | U.S. agency securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 3 | CMOs
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 3 | MBSs
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 3 | Municipal securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 3 | Corporate debt securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]	$ 0
Securities available-for-sale, at fair value	[3]			0
Recurring | Level 3 | Equity securities
Securities available-for-sale:
Securities available-for-sale, at fair value	[3]			$ 0
[1]	As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."
[2]	Included in other assets in the Consolidated Statements of Financial Condition.
[3]	As a result of recently adopted accounting guidance, equity securities are no longer presented within trading securities or securities available-for-sale for the prior period and are not presented within equity securities for the current period. For further discussion of this guidance, see Note 2 of "Notes to the Consolidated Financial Statements" in Item 8 of this Form 10-K.
[4]	Included in other assets in the Consolidated Statements of Financial Condition.
[5]	Included in other liabilities in the Consolidated Statements of Financial Condition.

Fair Value - Rollforward of Ca

Fair Value - Rollforward of Carrying Value of CDOs (Details) - CDOs - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Rollforward of the Carrying Value of CDOs
Beginning balance		$ 33,260	$ 31,529
Additions		0	0
Change in other comprehensive income	[1]	14,421	2,337
Paydowns and sales		(47,681)	(606)
Ending balance		$ 0	$ 33,260
[1]	Included in unrealized holding (losses) gains in the Consolidated Statements of Comprehensive Income.

Fair Value - Narrative (Detail

Fair Value - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value [Line Items]
Total amount of loans being serviced for the benefit of others at the end of the year	$ 627,323	$ 607,016	$ 640,530
Minimum
Fair Value [Line Items]
Appraisal adjustment (percent)	0.00%
Maximum
Fair Value [Line Items]
Appraisal adjustment (percent)	15.00%

Fair Value - Significant Unobs

Fair Value - Significant Unobservable Inputs Used in the Valuation of MSRs (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Minimum
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Prepayment speed	6.50%	4.20%
Maturity (months)	20 months	6 months
Discount rate	9.50%	9.50%
Maximum
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Prepayment speed	13.50%	13.10%
Maturity (months)	104 months	92 months
Discount rate	12.00%	12.00%

Fair Value - Rollforward of _2

Fair Value - Rollforward of Carrying Value of MSRs (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Rollforward of Carrying Value of MSRs
Beginning balance		$ 5,894	[1]	$ 6,120	[1]	$ 1,853
Additions from acquisition		0		0		3,092
New MSRs		1,080		673		1,263
Total gains (losses) included in earnings:
Changes in valuation inputs and assumptions	[2]	475		(41)		610
Other changes in fair value	[2],[3]	(719)		(858)		(698)
Ending balance	[1]	6,730		5,894		6,120
Contractual servicing fees earned during the year	[2]	1,517		1,536		1,312
Total amount of loans being serviced for the benefit of others at the end of the year		$ 627,323		$ 607,016		$ 640,530
[1]	Included in other assets in the Consolidated Statements of Financial Condition.
[2]	Included in mortgage banking income in the Consolidated Statements of Income and related to assets held as of December 31, 2018, 2017, and 2016.
[3]	Primarily represents changes in expected future cash flows over time due to payoffs and paydowns.

Fair Value - Annual Fair Value

Fair Value - Annual Fair Value Measurements of Pension Plan Asses (Details) - USD ($) $ in Thousands		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		$ 76,210	[1]	$ 66,159	$ 65,189
Mutual funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	[2]	27,246		41,002
U.S. agency securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		8,015		13,075
Corporate bonds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		10,472		9,171
Common stocks
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		26,882		0
Common trust funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		3,595		2,911
Level 1
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		58,517		44,680
Level 1 | Mutual funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	[2]	27,246		41,002
Level 1 | U.S. agency securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		4,389		3,678
Level 1 | Corporate bonds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0		0
Level 1 | Common stocks
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		26,882		0
Level 1 | Common trust funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0		0
Level 2
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		17,693		21,479
Level 2 | Mutual funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	[2]	0		0
Level 2 | U.S. agency securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		3,626		9,397
Level 2 | Corporate bonds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		10,472		9,171
Level 2 | Common stocks
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0		0
Level 2 | Common trust funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		$ 3,595		$ 2,911
[1]	Additional information regarding the fair value of Pension Plan assets as of December 31, 2018 can be found in Note 21, "Fair Value."
[2]	Includes mutual funds, money market funds, cash, cash equivalents, and accrued interest.

Fair Value - Non-Recurring Fai

Fair Value - Non-Recurring Fair Value Measurements (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Fair Value (Details) - Assets Measured On A Non-Recurring Basis [Line Items]
OREO		$ 12,821	$ 20,851
Level 1 | Nonrecurring
Fair Value (Details) - Assets Measured On A Non-Recurring Basis [Line Items]
Collateral-dependent impaired loans	[1]	0	0
OREO	[2]	0	0
Loans held-for-sale	[3]	0	0
Assets held-for-sale	[4]	0	0
Level 2 | Nonrecurring
Fair Value (Details) - Assets Measured On A Non-Recurring Basis [Line Items]
Collateral-dependent impaired loans	[1]	0	0
OREO	[2]	0	0
Loans held-for-sale	[3]	0	0
Assets held-for-sale	[4]	0	0
Level 3 | Nonrecurring
Fair Value (Details) - Assets Measured On A Non-Recurring Basis [Line Items]
Collateral-dependent impaired loans	[1]	24,565	33,240
OREO	[2]	6,012	12,340
Loans held-for-sale	[3]	3,478	21,098
Assets held-for-sale	[4]	$ 3,722	$ 2,208
[1]	Includes impaired loans with charge-offs and impaired loans with a specific reserve during the periods presented.
[2]	Includes OREO with fair value adjustments subsequent to initial transfer that occurred during the periods presented.
[3]	Included in other assets in the Consolidated Statements of Financial Condition.
[4]	Included in premises, furniture, and equipment in the Consolidated Statements of Financial Condition.

Fair Value - Fair Value Measur

Fair Value - Fair Value Measurements of Other Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 211,189	$ 192,800
Interest-bearing deposits in other banks	78,069	153,770
Securities held-to-maturity	10,176	13,760
FHLB and FRB stock	80,302	69,708
Loans	11,344,564	10,342,083
Investment in BOLI	296,733	279,900
Liabilities
Deposits	12,084,112	11,053,325
Borrowed funds	906,079	714,884
Senior and subordinated debt	203,808	195,170
Level 1 | Carrying Amount
Assets
Cash and due from banks	211,189	192,800
Level 1 | Fair Value
Assets
Cash and due from banks	211,189	192,800
Level 2 | Carrying Amount
Assets
Interest-bearing deposits in other banks	78,069	153,770
Securities held-to-maturity	10,176	13,760
FHLB and FRB stock	80,302	69,708
Liabilities
Deposits	12,084,112	11,053,325
Borrowed funds	906,079	714,884
Senior and subordinated debt	203,808	195,170
Accrued interest payable	10,005	4,704
Level 2 | Fair Value
Assets
Interest-bearing deposits in other banks	78,069	153,770
Securities held-to-maturity	9,871	12,013
FHLB and FRB stock	80,302	69,708
Liabilities
Deposits	12,064,604	11,038,819
Borrowed funds	906,079	714,884
Senior and subordinated debt	211,207	208,666
Accrued interest payable	10,005	4,704
Level 3 | Carrying Amount
Assets
Loans	11,346,668	10,345,397
Investment in BOLI	296,733	279,900
Accrued interest receivable	54,847	45,261
Other interest-earning assets	5	228
Level 3 | Fair Value
Assets
Loans	11,052,040	10,059,992
Investment in BOLI	296,733	279,900
Accrued interest receivable	54,847	45,261
Other interest-earning assets	$ 5	$ 228

Related Party Transactions - Na

Related Party Transactions - Narrative (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (percent)	5.00%	5.00%

Condensed Parent Company Fina_3

Condensed Parent Company Financial Statements - Statements of Financial Condition (Parent Company Only) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and due from banks	$ 211,189	$ 192,800
Other assets	245,734	221,451
Total assets	15,505,649	14,077,052
Liabilities and Stockholders' Equity
Senior and subordinated debt	203,808	195,170
Accrued interest payable and other liabilities	256,652	248,799
Stockholders' equity	2,054,998	1,864,874	$ 1,257,080	$ 1,146,268
Total liabilities and stockholders' equity	15,505,649	14,077,052
Parent Company
Assets
Cash and due from banks	158,026	120,812
Investments in and advances to subsidiaries	2,091,158	1,952,414
Other assets	55,782	43,606
Total assets	2,304,966	2,116,832
Liabilities and Stockholders' Equity
Senior and subordinated debt	203,808	195,170
Accrued interest payable and other liabilities	46,160	56,788
Stockholders' equity	2,054,998	1,864,874
Total liabilities and stockholders' equity	$ 2,304,966	$ 2,116,832

Condensed Parent Company Fina_4

Condensed Parent Company Financial Statements - Statements of Income (Parent Company Only) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income
Interest income	$ 582,492	$ 509,716	$ 378,332
Securities transactions and other	9,636	9,859	7,282
Expenses
Interest expense	65,870	37,712	28,641
Other expenses	28,236	23,956	20,152
Income before income tax expense	197,057	187,954	138,520
Income tax benefit	(39,187)	(89,567)	(46,171)
Net income	157,870	98,387	92,349
Net income applicable to non-vested restricted shares	(1,312)	(916)	(1,043)
Net income applicable to common shares	156,558	97,471	91,306
Parent Company
Income
Dividends from subsidiaries	86,095	74,091	86,791
Interest income	453	2,211	2,188
Securities transactions and other	280	(1,372)	215
Total income	86,828	74,930	89,194
Expenses
Interest expense	12,708	12,428	12,477
Salaries and employee benefits	22,430	20,978	16,104
Other expenses	9,440	9,126	7,110
Total expenses	44,578	42,532	35,691
Income before income tax expense	42,250	32,398	53,503
Income tax benefit	13,299	14,851	12,878
Income before equity in undistributed income of subsidiaries	55,549	47,249	66,381
Equity in undistributed income of subsidiaries	102,321	51,138	25,968
Net income	157,870	98,387	92,349
Net income applicable to non-vested restricted shares	(1,312)	(916)	(1,043)
Net income applicable to common shares	$ 156,558	$ 97,471	$ 91,306

Condensed Parent Company Fina_5

Condensed Parent Company Financial Statements - Statements of Cash Flows (Parent Company Only) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities
Net income		$ 157,870	$ 98,387	$ 92,349
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of premises, furniture, and equipment		15,865	13,995	12,804
Net securities losses		0
Net securities losses			1,876	(1,420)
Share-based compensation expense	[1]	12,062	11,223	7,879
Tax benefit (expense) related to share-based compensation		258	349	(197)
Net decrease (increase) in other assets		(44,246)	121,577	(76,902)
Net (decrease) increase in other liabilities		(4,346)	(56,055)	47,315
Net cash provided by operating activities		253,184	234,266	121,731
Investing Activities
Purchases of premises, furniture, and equipment		(27,800)	(16,123)	(19,083)
Net cash used in investing activities		(1,002,386)	(145,780)	(1,049,338)
Financing Activities
Net proceeds from the issuance of subordinated debt		0	0	146,484
Payments for the retirement of senior and subordinated debt		0	0	(153,500)
Cash dividends paid		(44,293)	(37,129)	(29,198)
Restricted stock activity		(4,421)	(3,659)	(2,673)
Net cash provided by (used in) financing activities		691,890	(4,064)	808,553
Net (decrease) increase in cash and cash equivalents		(57,312)	84,422	(119,054)
Cash and cash equivalents at beginning of year		346,570	262,148	381,202
Cash and cash equivalents at end of year		289,258	346,570	262,148
Supplemental Disclosures of Cash Flow Information:
Common stock issued for acquisitions, net of issuance costs		83,303	534,090	54,896
Parent Company
Operating Activities
Net income		157,870	98,387	92,349
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiaries		(102,321)	(51,138)	(25,968)
Depreciation of premises, furniture, and equipment		42	9	2
Net securities losses		0
Net securities losses			1,523	0
Share-based compensation expense		12,062	11,223	7,879
Tax benefit (expense) related to share-based compensation		258	349	(197)
Net decrease (increase) in other assets		35,981	18,667	(75,104)
Net (decrease) increase in other liabilities		(17,942)	(52,377)	74,571
Net cash provided by operating activities		85,950	26,643	73,532
Investing Activities
Purchases of securities available-for-sale		0	0	(14)
Proceeds from sales and maturities of securities available-for-sale		0	42,516	601
Purchases of premises, furniture, and equipment		(61)	(119)	0
Net cash received (paid) for acquisitions		39	(47,364)	(14,905)
Net cash used in investing activities		(22)	(4,967)	(14,318)
Financing Activities
Net proceeds from the issuance of subordinated debt		0	0	146,484
Payments for the retirement of senior and subordinated debt		0	0	(153,500)
Cash dividends paid		(44,293)	(37,129)	(29,198)
Restricted stock activity		(4,421)	(3,952)	(2,476)
Net cash provided by (used in) financing activities		(48,714)	(41,081)	(38,690)
Net (decrease) increase in cash and cash equivalents		37,214	(19,405)	20,524
Cash and cash equivalents at beginning of year		120,812	140,217	119,693
Cash and cash equivalents at end of year		158,026	120,812	140,217
Supplemental Disclosures of Cash Flow Information:
Common stock issued for acquisitions, net of issuance costs		$ 83,303	$ 534,090	$ 54,896
[1]	Comprised of restricted stock, restricted stock unit, and performance share awards expense.