First Commonwealth Financial (FCF) 10-Q 7 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 03, 2019
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	FCF
Entity Registrant Name	FIRST COMMONWEALTH FINANCIAL CORP /PA/
Entity Central Index Key	0000712537
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		98,499,937
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes

Condensed Consolidated Statemen

Condensed Consolidated Statements of Financial Condition (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets
Cash and due from banks	$ 100,724	$ 95,934
Interest-bearing bank deposits	23,168	3,013
Securities available for sale, at fair value	893,101	909,247
Securities held to maturity, at amortized cost (Fair value of $380,443 and $383,993 at March 31, 2019 and December 31, 2018, respectively)	384,909	393,855
Other investments	25,378	32,126
Loans held for sale	9,627	11,881
Loans:
Portfolio loans	5,871,070	5,774,139
Allowance for credit losses	(49,653)	(47,764)
Net loans	5,821,417	5,726,375
Premises and equipment, net	129,107	80,474
Other real estate owned	3,993	3,935
Goodwill	274,202	274,202
Amortizing intangibles, net	12,876	13,038
Bank owned life insurance	217,192	215,766
Other assets	76,979	68,409
Total assets	7,972,673	7,828,255
Deposits (all domestic):
Noninterest-bearing	1,510,566	1,466,213
Interest-bearing	4,620,194	4,431,779
Total deposits	6,130,760	5,897,992
Short-term borrowings	565,616	721,823
Subordinated debentures	170,328	170,288
Other long-term debt	7,395	7,551
Capital Lease Obligations	7,118	7,217
Total long-term debt	184,841	185,056
Other liabilities	93,437	47,995
Total liabilities	6,974,654	6,852,866
Shareholders’ Equity
Preferred stock, $1 par value per share, 3,000,000 shares authorized, none issued	0	0
Common stock, $1 par value per share, 200,000,000 shares authorized; 113,914,902 shares issued at March 31, 2019 and December 31, 2018, and 98,625,806 and 98,518,668 shares outstanding at March 31, 2019 and December 31, 2018, respectively	113,915	113,915
Additional paid-in capital	493,664	492,273
Retained earnings	526,136	511,409
Accumulated other comprehensive loss, net	(4,102)	(11,341)
Treasury stock (15,289,096 and 15,396,234 shares at March 31, 2019 and December 31, 2018, respectively)	(131,594)	(130,867)
Total shareholders’ equity	998,019	975,389
Total liabilities and shareholders’ equity	$ 7,972,673	$ 7,828,255

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Financial Condition (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	3,000,000	3,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	113,914,902	113,914,902
Common stock, shares outstanding (in shares)	98,625,806	98,518,668
Treasury stock, shares (in shares)	15,289,096	15,396,234
Securities held to maturity, fair value	$ 380,443	$ 383,993

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Interest Income
Interest and fees on loans	$ 70,421	$ 58,483
Interest and dividends on investments:
Taxable interest	8,164	7,056
Interest exempt from federal income taxes	418	410
Dividends	537	519
Interest on bank deposits	54	31
Total interest income	79,594	66,499
Interest Expense
Interest on deposits	8,175	3,541
Interest on short-term borrowings	3,438	2,295
Interest on subordinated debentures	2,354	827
Interest on other long-term debt	71	77
Interest on lease obligations	70	74
Total interest expense	14,108	6,814
Net Interest Income	65,486	59,685
Provision for credit losses	4,095	6,903
Net Interest Income after Provision for Credit Losses	61,391	52,782
Noninterest Income
Net securities gains	0	2,840
Trust income	1,926	1,928
Service charges on deposit accounts	4,245	4,406
Insurance and retail brokerage commissions	1,961	1,868
Income from bank owned life insurance	1,426	1,494
Gain on sale of mortgage loans	1,428	1,484
Gain on sale of other loans and assets	1,084	574
Card-related interchange income	4,730	4,742
Derivatives mark to market	(26)	789
Swap fee income	393	290
Other income	1,705	1,628
Total noninterest income	18,872	22,043
Noninterest Expense
Salaries and employee benefits	27,220	24,873
Net occupancy expense	4,916	4,369
Furniture and equipment expense	3,668	3,540
Data processing expense	2,544	2,433
Marketing and Advertising Expense	1,240	809
Pennsylvania shares tax expense	916	903
Intangible amortization	754	784
Collection and repossession expense	547	823
Other professional fees and services	754	1,007
FDIC insurance	574	776
Loss on sale or write-down of assets	65	197
Litigation and operational losses	401	179
Merger and acquisition related	0	337
Other Noninterest Expense	6,131	5,843
Total noninterest expense	49,730	46,873
Income Before Income Taxes	30,533	27,952
Income tax provision	5,944	4,682
Net Income	$ 24,589	$ 23,270
Average Shares Outstanding (in shares)	98,479,041	97,433,137
Average Shares Outstanding Assuming Dilution (in shares)	98,706,827	97,601,162
Per Share Data:
Basic Earnings per Share (in dollars per share)	$ 0.25	$ 0.24
Diluted Earnings per Share (in dollars per share)	0.25	0.24
Cash Dividends Declared per Common Share (in dollars per share)	$ 0.1	$ 0.08

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Income	$ 24,589	$ 23,270
Other comprehensive income (loss), before tax (expense) benefit:
Unrealized holding gains (losses) on securities arising during the period	9,030	(3,982)
Less: reclassification adjustment for gains on securities included in net income	0	(2,840)
Unrealized holding gains (losses) on derivatives arising during the period	133	(130)
Less: reclassification adjustment for losses on derivatives included in net income	0	0
Total other comprehensive income (loss), before tax (expense) benefit	9,163	(6,952)
Income tax (expense) benefit related to items of other comprehensive income (loss)	(1,924)	1,460
Total other comprehensive income (loss)	7,239	(5,492)
Comprehensive Income	$ 31,828	$ 17,778

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), net [Member]	Treasury Stock [Member]	Previously Reported [Member]	Previously Reported [Member]Common Stock [Member]	Previously Reported [Member]Additional Paid-in Capital [Member]	Previously Reported [Member]Retained Earnings [Member]	Previously Reported [Member]Accumulated Other Comprehensive Income (Loss), net [Member]	Previously Reported [Member]Treasury Stock [Member]	Effect of ASU Adoption [Member]Accumulated Other Comprehensive Income (Loss), net [Member]
Cumulative effect of adoption of ASU 2018-02	$ 0			$ 1,344	$ (1,344)
Beginning balance at Dec. 31, 2017	888,127	$ 113,915	$ 470,123	438,760	(7,517)	$ (127,154)	$ 888,127	$ 113,915	$ 470,123	$ 437,416	$ (6,173)	$ (127,154)
Beginning balance, shares at Dec. 31, 2017		97,456,478						97,456,478
Net Income	23,270			23,270
Other comprehensive income (loss)	(5,492)				(5,492)
Dividends, declared (USD per share)	(7,803)			(7,803)
Treasury stock acquired	(1,079)					(1,079)
Treasury stock acquired, shares		(72,307)
Stock Issued During Period, Value, Treasury Stock Reissued	2,257		1,108	0		1,149
Stock Issued During Period, Shares, Treasury Stock Reissued		149,480
Restricted stock	69	$ 0	537	0		(468)
Restricted stock, shares		69,500
Stock Issued During Period, Value, Treasury Stock Reissued	2,257
Ending balance at Mar. 31, 2018	899,349	$ 113,915	471,768	454,227	(13,009)	(127,552)
Ending balance, shares at Mar. 31, 2018		97,603,151
Cumulative effect of adoption of ASU 2018-02													$ 0
Beginning balance at Dec. 31, 2018	$ 975,389	$ 113,915	492,273	511,409	(11,341)	(130,867)
Beginning balance, shares at Dec. 31, 2018	98,518,668	98,518,668
Net Income	$ 24,589			24,589
Other comprehensive income (loss)	7,239				7,239
Dividends, declared (USD per share)	(9,862)			(9,862)
Treasury stock acquired	(2,074)					(2,074)
Treasury stock acquired, shares		(159,562)
Stock Issued During Period, Value, Treasury Stock Reissued	2,531		941	0		1,590
Stock Issued During Period, Shares, Treasury Stock Reissued		188,700
Restricted stock	207	$ 0	450	0		(243)
Restricted stock, shares		78,000
Stock Issued During Period, Value, Treasury Stock Reissued	2,531
Ending balance at Mar. 31, 2019	$ 998,019	$ 113,915	$ 493,664	$ 526,136	$ (4,102)	$ (131,594)
Ending balance, shares at Mar. 31, 2019	98,625,806	98,625,806

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cash Dividends Declared per Common Share (in dollars per share)	$ 0.1	$ 0.08

Condensed Consolidated Statem_7

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Activities
Net Income	$ 24,589	$ 23,270
Provision for credit losses	4,095	6,903
Deferred tax expense	1,443	1,097
Depreciation and amortization	2,478	2,380
Net gains on securities and other assets	(2,218)	(5,143)
Net amortization of premiums and discounts on securities	784	775
Income from increase in cash surrender value of bank owned life insurance	(1,426)	(1,494)
Increase in interest receivable	(2,346)	(620)
Mortgage loans originated for sale	(34,985)	(38,218)
Proceeds from sale of mortgage loans	35,255	46,134
Increase (decrease) in interest payable	1,522	(235)
Increase in income taxes payable	4,454	3,557
Other-net	(14,956)	(17,004)
Net cash provided by operating activities	18,689	21,402
Investing Activities
Proceeds from sale and maturity of held-to-maturity securities	8,641	11,335
Payments to acquire held-to-maturity securities	0	0
Proceeds from Sale of Available-for-sale Securities	0	0
Proceeds from maturities and redemptions of available-for-sale securities	31,099	44,067
Purchases of available-for-sale securities	(6,401)	(130,012)
Purchases of FHLB stock	(10,293)	(13,491)
Proceeds from the redemption of FHLB stock	17,041	18,928
Proceeds from Sale of Loans Receivable	8,559	6,647
Proceeds from sale of other assets	1,144	1,141
Net (increase) decrease in loans	(104,189)	16,012
Payments for Purchase of Other Assets	(4,128)	(1,974)
Net cash used in investing activities	(58,527)	(47,347)
Financing Activities
Net (decrease) increase in federal funds purchased	(11,000)	6,000
Net decrease in other short-term borrowings	(145,207)	(125,450)
Net increase in deposits	232,892	122,849
Repayments of other long-term debt	(156)	(150)
Repayments of Long-term Capital Lease Obligations	99	92
Dividends paid	(9,862)	(7,803)
Purchase of treasury stock	(1,785)	(1,079)
Net cash provided by (used in) financing activities	64,783	(5,725)
Net increase (decrease) in cash and cash equivalents	24,945	(31,670)
Cash and cash equivalents at January 1	98,947	107,292
Cash and cash equivalents at March 31	$ 123,892	$ 75,622

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accounting and reporting policies of First Commonwealth Financial Corporation and its subsidiaries (“First Commonwealth” or the “Company”) conform with generally accepted accounting principles in the United States of America (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the financial statements and accompanying notes. Actual realized amounts could differ from those estimates. In the opinion of management, the unaudited interim consolidated financial statements include all adjustments (consisting of only normal recurring adjustments) necessary for a fair presentation of First Commonwealth’s financial position, results of operations, comprehensive income, cash flows and changes in shareholders’ equity as of and for the periods presented. Certain information and Note disclosures normally included in Consolidated Financial Statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the SEC. For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks, federal funds sold and interest-bearing bank deposits. Generally, federal funds are sold for one-day periods. The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results that may be expected for the full year of 2019 . These interim financial statements should be read in conjunction with First Commonwealth’s 2018 Annual Report on Form 10-K. Adoption of New Accounting Standards In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)," in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. Additionally, the FASB issued ASU No. 2018-01, "Leases (Topic 842)" in January 2018, ASU No. 2018-11, "Leases - Targeted Improvements" in July 2018 and ASU 2018-20, "Leases - Narrow-Scope Improvements for Lessors" in December 2018. These ASU's provide certain improvements and optional practical expedients to Topic 842. First Commonwealth adopted this guidance on January 1, 2019. Under this new guidance, all entities will classify leases to determine how to recognize lease-related revenue and expense. Quantitative and qualitative disclosures will be required by lessees and lessors to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The intention is to require enough information to supplement the amounts recorded in the financial statements so that users can understand more about the nature of an entity’s leasing activities. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. First Commonwealth has elected the transition option provided in ASU No. 2018-11, which provides for the modified retrospective approach to be applied on January 1, 2019. Upon adoption of this standard on January 1, 2019, we recognized right-of-use ("ROU") assets and related lease liabilities totaling $38.5 million and $41.8 million, respectively. Additionally, during the first quarter of 2019, we recognized an additional right-of-use asset and related lease liability totaling $10.0 million in connection with the relocation of leased space that includes a corporate loan production office and some administrative offices. We have elected to apply certain practical expedients provided under the standard including (i) to not apply the requirements in the new standard to short-term leases (ii) to not reassess the lease classification for any expired or existing lease (iii) to account for lease and non-lease components separately (iv) to not reassess initial direct costs for any existing leases. The initial impact of this standard primarily relates to operating leases of certain real estate properties. First Commonwealth has no material leasing arrangements for which it is the lessor of property or equipment.

Supplemental Comprehensive Inco

Supplemental Comprehensive Income Disclosures	3 Months Ended
	Mar. 31, 2019
Supplemental Comprehensive Income Disclosures [Abstract]
Supplemental Comprehensive Income Disclosures	Supplemental Comprehensive Income Disclosures The following table identifies the related tax effects allocated to each component of other comprehensive income (“OCI”) in the Consolidated Statements of Comprehensive Income. Reclassification adjustments related to securities available for sale are included in the "Net securities gains" line and reclassification adjustments related to losses on derivatives are included in the "Other operating expenses" line in the Consolidated Statements of Income. For the Three Months Ended March 31, 2019 2018 Pretax Amount Tax (Expense) Benefit Net of Tax Amount Pretax Amount Tax (Expense) Benefit Net of Tax Amount (dollars in thousands) Unrealized gains (losses) on securities: Unrealized holding gains (losses) on securities arising during the period $ 9,030 $ (1,896 ) $ 7,134 $ (3,982 ) $ 837 $ (3,145 ) Reclassification adjustment for gains on securities included in net income — — — (2,840 ) 596 (2,244 ) Total unrealized gains (losses) on securities 9,030 (1,896 ) 7,134 (6,822 ) 1,433 (5,389 ) Unrealized gains (losses) on derivatives: Unrealized holding gains (losses) on derivatives arising during the period 133 (28 ) 105 (130 ) 27 (103 ) Reclassification adjustment for losses on derivatives included in net income — — — — — — Total unrealized gains (losses) on derivatives 133 (28 ) 105 (130 ) 27 (103 ) Total other comprehensive income (loss) $ 9,163 $ (1,924 ) $ 7,239 $ (6,952 ) $ 1,460 $ (5,492 ) The following table details the change in components of OCI for the three months ended March 31 : 2019 2018 Securities Available for Sale Post-Retirement Obligation Derivatives Accumulated Other Comprehensive Income (Loss) Securities Available for Sale Post-Retirement Obligation Derivatives Accumulated Other Comprehensive Income (Loss) (dollars in thousands) Balance at December 31 $ (11,697 ) $ 461 $ (105 ) $ (11,341 ) $ (6,166 ) $ 299 $ (306 ) $ (6,173 ) Cumulative effect of adoption of ASU 2018-02 — — — — (1,344 ) — — (1,344 ) Balance at January 1 (11,697 ) 461 (105 ) (11,341 ) (7,510 ) 299 (306 ) (7,517 ) Other comprehensive income (loss) before reclassification adjustment 7,134 — 105 7,239 (3,145 ) — (103 ) (3,248 ) Amounts reclassified from accumulated other comprehensive (loss) income — — — — (2,244 ) — — (2,244 ) Net other comprehensive income (loss) during the period 7,134 — 105 7,239 (5,389 ) — (103 ) (5,492 ) Balance at March 31 $ (4,563 ) $ 461 $ — $ (4,102 ) $ (12,899 ) $ 299 $ (409 ) $ (13,009 )

Supplemental Cash Flow Disclosu

Supplemental Cash Flow Disclosures	3 Months Ended
	Mar. 31, 2019
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Disclosures	Supplemental Cash Flow Disclosures The following table presents information related to cash paid during the period for interest and income taxes, as well as detail on non-cash investing and financing activities for the three months ended March 31 : 2019 2018 (dollars in thousands) Cash paid during the period for: Interest $ 12,660 $ 7,072 Income taxes 61 28 Non-cash investing and financing activities: Loans transferred to other real estate owned and repossessed assets 982 1,186 Loans transferred from held to maturity to held for sale 4,156 8,019 Gross increase (decrease) in market value adjustment to securities available for sale 9,030 (6,822 ) Gross increase (decrease) in market value adjustment to derivatives 133 (131 ) Noncash treasury stock reissuance 2,531 2,257 Unsettled treasury stock repurchases 289 — Proceeds from death benefit on bank-owned life insurance not received — 2,306

Earnings per Share

Earnings per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share The following table summarizes the composition of the weighted-average common shares (denominator) used in the basic and diluted earnings per share computations: For the Three Months Ended March 31, 2019 2018 Weighted average common shares issued 113,914,902 113,914,902 Average treasury stock shares (15,291,253 ) (16,369,144 ) Average deferred compensation shares (37,411 ) (37,411 ) Average unearned nonvested shares (107,197 ) (75,210 ) Weighted average common shares and common stock equivalents used to calculate basic earnings per share 98,479,041 97,433,137 Additional common stock equivalents (nonvested stock) used to calculate diluted earnings per share 190,375 130,614 Additional common stock equivalents (deferred compensation) used to calculate diluted earnings per share 37,411 37,411 Weighted average common shares and common stock equivalents used to calculate diluted earnings per share 98,706,827 97,601,162 Basic Earnings per Share $ 0.25 $ 0.24 Diluted Earnings per Share $ 0.25 $ 0.24 The following table shows the number of shares and the price per share related to common stock equivalents that were not included in the computation of diluted earnings per share for the three months ended March 31 because to do so would have been antidilutive. 2019 2018 Price Range Price Range Shares From To Shares From To Restricted Stock 95,403 $ 12.99 $ 14.49 37,298 $ 9.84 $ 14.49 Restricted Stock Units 39,618 $ 14.22 $ 16.62 43,067 $ 13.25 $ 15.83

Commitments and Contingent Liab

Commitments and Contingent Liabilities	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities Commitments and Letters of Credit Standby letters of credit and commercial letters of credit are conditional commitments issued by First Commonwealth to guarantee the performance of a customer to a third party. The contract or notional amount of these instruments reflects the maximum amount of future payments that First Commonwealth could be required to pay under the guarantees if there were a total default by the guaranteed parties, without consideration of possible recoveries under recourse provisions or from collateral held or pledged. In addition, many of these commitments are expected to expire without being drawn upon; therefore, the total commitment amounts do not necessarily represent future cash requirements. The following table identifies the notional amount of those instruments at: March 31, 2019 December 31, 2018 (dollars in thousands) Financial instruments whose contract amounts represent credit risk: Commitments to extend credit $ 1,881,445 $ 1,883,914 Financial standby letters of credit 18,121 18,298 Performance standby letters of credit 28,520 22,027 Commercial letters of credit 887 887 The notional amounts outstanding as of March 31, 2019 include amounts issued in 2019 of $8.1 million in performance standby letters of credit. There were no financial standby or commercial letters of credit issued in 2019 . A liability of $0.3 million and $0.2 million has been recorded as of March 31, 2019 and December 31, 2018 , respectively, which represents the estimated fair value of letters of credit issued. The fair value of letters of credit is estimated based on the unrecognized portion of fees received at the time the commitment was issued. Unused commitments and letters of credit provide exposure to future credit loss in the event of nonperformance by the borrower or guaranteed parties. Management’s evaluation of the credit risk related to these commitments resulted in the recording of a liability of $4.6 million and $5.0 million as of March 31, 2019 and December 31, 2018 , respectively. This liability is reflected in "Other liabilities" in the Consolidated Statements of Financial Condition. The credit risk evaluation incorporated probability of default, loss given default and estimated utilization for the next twelve months for each loan category and the letters of credit. Legal Proceedings First Commonwealth and its subsidiaries are subject in the normal course of business to various pending and threatened legal proceedings in which claims for monetary damages are asserted. As of March 31, 2019 , management, after consultation with legal counsel, does not anticipate that the aggregate ultimate liability arising out of litigation pending or threatened against First Commonwealth or its subsidiaries will be material to First Commonwealth’s consolidated financial position. On at least a quarterly basis, First Commonwealth assesses its liabilities and contingencies in connection with such legal proceedings. For those matters where it is probable that First Commonwealth will incur losses and the amounts of the losses can be reasonably estimated, First Commonwealth records an expense and corresponding liability in its consolidated financial statements. To the extent the pending or threatened litigation could result in exposure in excess of that liability, the amount of such excess is not currently estimable. Although not considered probable, the range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability (if any), is between $0 and $1 million . Although First Commonwealth does not believe that the outcome of pending litigation will be material to First Commonwealth’s consolidated financial position, it cannot rule out the possibility that such outcomes will be material to the consolidated results of operations and cash flows for a particular reporting period in the future.

Investment Securities

Investment Securities	3 Months Ended
	Mar. 31, 2019
Investment Securities [Abstract]
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	Investment Securities Securities Available for Sale Below is an analysis of the amortized cost and estimated fair values of securities available for sale at: March 31, 2019 December 31, 2018 Amortized Gross Gross Estimated Amortized Gross Gross Estimated (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ 8,731 $ 539 $ (24 ) $ 9,246 $ 9,011 $ 479 $ (84 ) $ 9,406 Mortgage-Backed Securities – Commercial 169,153 457 (1,490 ) 168,120 169,633 214 (2,103 ) 167,744 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 660,080 2,749 (8,863 ) 653,966 686,906 1,846 (15,391 ) 673,361 Other Government-Sponsored Enterprises 10,000 6 — 10,006 10,000 12 — 10,012 Obligations of States and Political Subdivisions 28,010 204 — 28,214 27,592 126 (6 ) 27,712 Corporate Securities 22,903 665 (19 ) 23,549 20,912 321 (221 ) 21,012 Total Securities Available for Sale $ 898,877 $ 4,620 $ (10,396 ) $ 893,101 $ 924,054 $ 2,998 $ (17,805 ) $ 909,247 Mortgage-backed securities include mortgage-backed obligations of U.S. Government agencies and obligations of U.S. Government-sponsored enterprises. These obligations have contractual maturities ranging from less than one year to approximately 30 years with lower anticipated lives to maturity due to prepayments. All mortgage-backed securities contain a certain amount of risk related to the uncertainty of prepayments of the underlying mortgages. Interest rate changes have a direct impact upon prepayment speeds; therefore, First Commonwealth uses computer simulation models to test the average life and yield volatility of all mortgage-backed securities under various interest rate scenarios to monitor the potential impact on earnings and interest rate risk positions. Expected maturities will differ from contractual maturities because issuers may have the right to call or repay obligations with or without call or prepayment penalties. Other fixed income securities within the portfolio also contain prepayment risk. The amortized cost and estimated fair value of debt securities available for sale at March 31, 2019 , by contractual maturity, are shown below. Amortized Estimated (dollars in thousands) Due within 1 year $ — $ — Due after 1 but within 5 years 27,333 27,588 Due after 5 but within 10 years 33,580 34,181 Due after 10 years — — 60,913 61,769 Mortgage-Backed Securities (a) 837,964 831,332 Total Debt Securities $ 898,877 $ 893,101 (a) Mortgage-Backed Securities include an amortized cost of $177.9 million and a fair value of $177.4 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $660.1 million and a fair value of $654.0 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac. Proceeds from sales, gross gains (losses) realized on sales, maturities and other-than-temporary impairment charges related to securities available for sale were as follows for the three months ended March 31 : 2019 2018 (dollars in thousands) Proceeds from sales $ — $ — Gross gains (losses) realized: Sales Transactions: Gross gains $ — $ — Gross losses — — — — Maturities and impairment Gross gains — 2,840 Gross losses — — — 2,840 Net gains and impairment $ — $ 2,840 Gross gains of $2.8 million were recognized in 2018 as a result of a successful auction call on PreSTL XIV, one of our pooled trust preferred securities. There were no gains or losses recognized in 2019 . Securities available for sale with an estimated fair value of $625.2 million and $636.3 million were pledged as of March 31, 2019 and December 31, 2018 , respectively, to secure public deposits and for other purposes required or permitted by law. Securities Held to Maturity Below is an analysis of the amortized cost and fair values of debt securities held to maturity at: March 31, 2019 December 31, 2018 Amortized Gross Gross Estimated Amortized Gross Gross Estimated (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ 3,606 $ — $ (26 ) $ 3,580 $ 3,635 $ — $ (97 ) $ 3,538 Mortgage-Backed Securities- Commercial 54,898 — (1,763 ) 53,135 55,221 — (2,327 ) 52,894 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 270,807 352 (3,303 ) 267,856 279,109 212 (7,254 ) 272,067 Mortgage-Backed Securities – Commercial 12,894 — (95 ) 12,799 13,159 — (258 ) 12,901 Obligations of States and Political Subdivisions 42,304 400 (31 ) 42,673 42,331 175 (313 ) 42,193 Debt Securities Issued by Foreign Governments 400 — — 400 400 — — 400 Total Securities Held to Maturity $ 384,909 $ 752 $ (5,218 ) $ 380,443 $ 393,855 $ 387 $ (10,249 ) $ 383,993 The amortized cost and estimated fair value of debt securities held to maturity at March 31, 2019 , by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or repay obligations with or without call or prepayment penalties. Amortized Estimated (dollars in thousands) Due within 1 year $ 518 $ 518 Due after 1 but within 5 years 7,922 7,965 Due after 5 but within 10 years 34,264 34,590 Due after 10 years — — 42,704 43,073 Mortgage-Backed Securities (a) 342,205 337,370 Total Debt Securities $ 384,909 $ 380,443 (a) Mortgage-Backed Securities include an amortized cost of $58.5 million and a fair value of $56.7 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $283.7 million and a fair value of $280.7 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac. Securities held to maturity with an amortized cost of $324.7 million and $250.3 million were pledged as of March 31, 2019 and December 31, 2018 , respectively, to secure public deposits and for other purposes required or permitted by law.

Impairment of Investment Securi

Impairment of Investment Securities	3 Months Ended
	Mar. 31, 2019
Impairment of Investment Securities Disclosure [Abstract]
Impairment of Investment Securities	Impairment of Investment Securities Securities Available for Sale and Held to Maturity As required by FASB ASC Topic 320, “Investments – Debt and Equity Securities,” credit-related other-than-temporary impairment on debt securities is recognized in earnings, while non-credit related other-than-temporary impairment on debt securities not expected to be sold is recognized in OCI. During the three months ended March 31, 2019 and 2018 , no other-than-temporary impairment charges were recognized. First Commonwealth utilizes the specific identification method to determine the net gain or loss on debt securities and the average cost method to determine the net gain or loss on equity securities. We review our investment portfolio on a quarterly basis for indications of impairment. This review includes analyzing the length of time and the extent to which the fair value has been lower than the cost, the financial condition and near-term prospects of the issuer, including any specific events which may influence the operations of the issuer and whether we are more likely than not to sell, or be required to sell, the security. We evaluate whether we are more likely than not to sell debt securities based upon our investment strategy for the particular type of security, our cash flow needs, liquidity position, capital adequacy, tax position and interest rate risk position. In addition, the risk of future other-than-temporary impairment may be influenced by weakness in the U.S. economy or changes in real estate values. The following table presents the gross unrealized losses and estimated fair values at March 31, 2019 for both available for sale and held to maturity securities by investment category and time frame for which securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total Estimated Gross Estimated Gross Estimated Gross (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ — $ — $ 7,336 $ (50 ) $ 7,336 $ (50 ) Mortgage-Backed Securities – Commercial 48,274 (28 ) 124,003 (3,225 ) 172,277 (3,253 ) Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 4 — 710,446 (12,166 ) 710,450 (12,166 ) Mortgage-Backed Securities – Commercial — — 12,799 (95 ) 12,799 (95 ) Obligations of States and Political Subdivisions — — 5,925 (31 ) 5,925 (31 ) Debt Securities Issued by Foreign Governments 200 — — — 200 — Corporate Securities — — 4,976 (19 ) 4,976 (19 ) Total Securities $ 48,478 $ (28 ) $ 865,485 $ (15,586 ) $ 913,963 $ (15,614 ) At March 31, 2019 , fixed income securities issued by U.S. Government-sponsored enterprises and U.S. Government agencies comprised 79% and 21% , respectively, of total unrealized losses due to changes in market interest rates. At March 31, 2019 , there are 98 debt securities in an unrealized loss position. The following table presents the gross unrealized losses and estimated fair values at December 31, 2018 by investment category and time frame for which securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total Estimated Gross Estimated Gross Estimated Gross (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ 2,289 $ (41 ) $ 5,028 $ (140 ) $ 7,317 $ (181 ) Mortgage-Backed Securities - Commercial 95,826 (925 ) 75,959 (3,505 ) 171,785 (4,430 ) Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 156,732 (1,856 ) 626,003 (20,789 ) 782,735 (22,645 ) Mortgage-Backed Securities – Commercial — — 12,901 (258 ) 12,901 (258 ) Obligation of States and Political Subdivisions 8,591 (85 ) 9,338 (234 ) 17,929 (319 ) Corporate Securities 14,769 (214 ) 3,993 (7 ) 18,762 (221 ) Total Securities $ 278,207 $ (3,121 ) $ 733,222 $ (24,933 ) $ 1,011,429 $ (28,054 ) As of March 31, 2019 , our corporate securities had an amortized cost and an estimated fair value of $22.9 million and $23.5 million , respectively. As of December 31, 2018 , our corporate securities had an amortized cost and estimated fair value of $20.9 million and $21.0 million , respectively. Corporate securities are comprised of debt for large regional banks. There was one corporate security in an unrealized loss position as of March 31, 2019 and four corporate securities in an unrealized loss position as of December 31, 2018 . When unrealized losses exist on these investments, management reviews each of the issuer’s asset quality, earnings trends and capital position, to determine whether issues in an unrealized loss position were other-than-temporarily impaired. All interest payments on the corporate securities are being made as contractually required. During 2018, all of our pooled trust preferred collateralized debt obligations were liquidated either through a successful auction call or sale. Other-than-temporary impairment charges were recognized on the pooled trust preferred securities in 2008, 2009 and 2010. The following table provides a cumulative roll forward of credit losses recognized in earnings for the trust preferred securities: For the Three Months Ended March 31, 2019 2018 (dollars in thousands) Balance, beginning (a) $ — $ 12,208 Credit losses on debt securities for which other-than-temporary impairment was not previously recognized — — Additional credit losses on debt securities for which other-than-temporary impairment was previously recognized — — Increases in cash flows expected to be collected, recognized over the remaining life of the security (b) — (147 ) Reduction for debt securities sold during the period — — Reduction for debt securities called during the period — (2,302 ) Balance, ending $ — $ 9,759 (a) The beginning balance represents credit related losses included in other-than-temporary impairment charges recognized on debt securities in prior periods. (b) Represents the increase in cash flows recognized in interest income during the period. Other Investments As a member of the Federal Home Loan Bank ("FHLB"), First Commonwealth is required to purchase and hold stock in the FHLB to satisfy membership and borrowing requirements. The level of stock required to be held is dependent on the amount of First Commonwealth's mortgage-related assets and outstanding borrowings with the FHLB. This stock is restricted in that it can only be sold to the FHLB or to another member institution, and all sales of FHLB stock must be at par. As a result of these restrictions, FHLB stock is unlike other investment securities insofar as there is no trading market for FHLB stock and the transfer price is determined by FHLB membership rules and not by market participants. As of March 31, 2019 and December 31, 2018 , our FHLB stock totaled $23.7 million and $30.5 million , respectively, and is included in “Other investments” on the Consolidated Statements of Financial Condition. FHLB stock is held as a long-term investment and its value is determined based on the ultimate recoverability of the par value. First Commonwealth evaluates impairment quarterly and has concluded that the par value of its investment in FHLB stock will be recovered. Accordingly, no impairment charge was recorded on these securities during the three months ended March 31, 2019 . As of both March 31, 2019 and 2018 , "Other investments" also includes $1.7 million in equity securities. These securities do not have a readily determinable fair value and are carried at cost. During the three -months ended March 31, 2019 and 2018 , there were no gains or losses recognized through earnings on equity securities. On a quarterly basis, management evaluates equity securities by reviewing the severity and duration of decline in estimated fair value, research reports, analysts’ recommendations, credit rating changes, news stories, annual reports, regulatory filings, impact of interest rate changes and other relevant information.

Loans and Allowance for Credit

Loans and Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2019
Loans and Leases Receivable Disclosure [Abstract]
Loans and Allowance for Credit Losses	Loans and Allowance for Credit Losses The following table provides outstanding balances related to each of our loan types: March 31, 2019 December 31, 2018 Originated Acquired Total Originated Acquired Total (dollars in thousands) Commercial, financial, agricultural and other $ 1,143,885 $ 36,435 $ 1,180,320 $ 1,100,947 $ 37,526 $ 1,138,473 Real estate construction 383,164 6,223 389,387 353,008 5,970 358,978 Residential real estate 1,325,740 239,609 1,565,349 1,313,645 248,760 1,562,405 Commercial real estate 1,946,482 191,894 2,138,376 1,922,349 201,195 2,123,544 Loans to individuals 593,481 4,157 597,638 585,347 5,392 590,739 Total loans $ 5,392,752 $ 478,318 $ 5,871,070 $ 5,275,296 $ 498,843 $ 5,774,139 Credit Quality Information As part of the on-going monitoring of credit quality within the loan portfolio, the following credit worthiness categories are used in grading our loans: Pass Acceptable levels of risk exist in the relationship. Includes all loans not classified as OAEM, substandard or doubtful. Other Assets Especially Mentioned (OAEM) Potential weaknesses that deserve management’s close attention. The potential weaknesses may result in deterioration of the repayment prospects or weaken the Company’s credit position at some future date. The credit risk may be relatively minor, yet constitute an undesirable risk in light of the circumstances surrounding the specific credit. No loss of principal or interest is expected. Substandard Well-defined weakness or a weakness that jeopardizes the repayment of the debt. A loan may be classified as substandard as a result of deterioration of the borrower’s financial condition and repayment capacity. Loans for which repayment plans have not been met or collateral equity margins do not protect the Company may also be classified as substandard. Doubtful Loans with the characteristics of substandard loans with the added characteristic that collection or liquidation in full, on the basis of presently existing facts and conditions, is highly improbable. The use of creditworthiness categories to grade loans permits management’s use of migration analysis to estimate a portion of credit risk. The Company’s internal creditworthiness grading system provides a measurement of credit risk based primarily on an evaluation of the borrower’s cash flow and collateral. Movement between these rating categories provides a predictive measure of credit losses and therefore assists in determining the appropriate level for the loan loss reserves. Category ratings are reviewed each quarter, at which time management analyzes the results, as well as other external statistics and factors related to loan performance. Loans that migrate towards higher risk rating levels generally have an increased risk of default, whereas loans that migrate toward lower risk ratings generally will result in a lower risk factor being applied to those related loan balances. The following tables represent our credit risk profile by creditworthiness: March 31, 2019 Commercial, financial, agricultural and other Real estate construction Residential real estate Commercial real estate Loans to individuals Total (dollars in thousands) Originated loans Pass $ 1,107,013 $ 374,201 $ 1,315,339 $ 1,894,745 $ 593,253 $ 5,284,551 Non-Pass OAEM 31,225 8,963 809 32,635 — 73,632 Substandard 5,647 — 9,592 19,102 228 34,569 Doubtful — — — — — — Total Non-Pass 36,872 8,963 10,401 51,737 228 108,201 Total $ 1,143,885 $ 383,164 $ 1,325,740 $ 1,946,482 $ 593,481 $ 5,392,752 Acquired loans Pass $ 30,627 $ 5,602 $ 236,594 $ 189,052 $ 4,143 $ 466,018 Non-Pass OAEM 5,672 621 725 423 — 7,441 Substandard 136 — 2,290 2,419 14 4,859 Doubtful — — — — — — Total Non-Pass 5,808 621 3,015 2,842 14 12,300 Total $ 36,435 $ 6,223 $ 239,609 $ 191,894 $ 4,157 $ 478,318 December 31, 2018 Commercial, financial, agricultural and other Real estate construction Residential real estate Commercial real estate Loans to individuals Total (dollars in thousands) Originated loans Pass $ 1,055,394 $ 337,367 $ 1,302,912 $ 1,880,139 $ 585,141 $ 5,160,953 Non-Pass OAEM 33,723 15,641 1,026 28,904 — 79,294 Substandard 11,830 — 9,707 13,306 206 35,049 Doubtful — — — — — — Total Non-Pass 45,553 15,641 10,733 42,210 206 114,343 Total $ 1,100,947 $ 353,008 $ 1,313,645 $ 1,922,349 $ 585,347 $ 5,275,296 Acquired loans Pass $ 31,399 $ 5,337 $ 245,637 $ 198,201 $ 5,377 $ 485,951 Non-Pass OAEM 5,890 633 736 441 — 7,700 Substandard 237 — 2,387 2,553 15 5,192 Doubtful — — — — — — Total Non-Pass 6,127 633 3,123 2,994 15 12,892 Total $ 37,526 $ 5,970 $ 248,760 $ 201,195 $ 5,392 $ 498,843 Portfolio Risks The credit quality of our loan portfolio can potentially represent significant risk to our earnings, capital and liquidity. First Commonwealth devotes substantial resources to managing this risk primarily through our credit administration department that develops and administers policies and procedures for underwriting, maintaining, monitoring and collecting loans. Credit administration is independent of lending departments and oversight is provided by the Credit Committee of the First Commonwealth Board of Directors. Criticized loans have been evaluated when determining the appropriateness of the allowance for credit losses, which we believe is adequate to absorb losses inherent to the portfolio as of March 31, 2019 . However, changes in economic conditions, interest rates, borrower financial condition, delinquency trends or previously established fair values of collateral factors could significantly change those judgmental estimates. Age Analysis of Past Due Loans by Segment The following tables delineate the aging analysis of the recorded investments in past due loans as of March 31, 2019 and December 31, 2018 . Also included in these tables are loans that are 90 days or more past due and still accruing because they are well-secured and in the process of collection. March 31, 2019 30 - 59 60 - 89 90 days Nonaccrual Total past Current Total (dollars in thousands) Originated loans Commercial, financial, agricultural and other $ 207 $ 1,037 $ 83 $ 4,390 $ 5,717 $ 1,138,168 $ 1,143,885 Real estate construction 507 — — — 507 382,657 383,164 Residential real estate 2,995 1,739 460 6,126 11,320 1,314,420 1,325,740 Commercial real estate 1,161 122 — 8,539 9,822 1,936,660 1,946,482 Loans to individuals 2,406 481 759 228 3,874 589,607 593,481 Total $ 7,276 $ 3,379 $ 1,302 $ 19,283 $ 31,240 $ 5,361,512 $ 5,392,752 Acquired loans Commercial, financial, agricultural and other $ — $ — $ — $ 100 $ 100 $ 36,335 $ 36,435 Real estate construction — — — — — 6,223 6,223 Residential real estate 98 35 171 1,816 2,120 237,489 239,609 Commercial real estate 185 — — 947 1,132 190,762 191,894 Loans to individuals 22 7 36 14 79 4,078 4,157 Total $ 305 $ 42 $ 207 $ 2,877 $ 3,431 $ 474,887 $ 478,318 December 31, 2018 30 - 59 60 - 89 90 days Nonaccrual Total past Current Total (dollars in thousands) Originated loans Commercial, financial, agricultural and other $ 130 $ 247 $ 92 $ 10,223 $ 10,692 $ 1,090,255 $ 1,100,947 Real estate construction 212 — — — 212 352,796 353,008 Residential real estate 3,697 710 790 6,238 11,435 1,302,210 1,313,645 Commercial real estate 492 69 — 3,437 3,998 1,918,351 1,922,349 Loans to individuals 2,362 532 662 207 3,763 581,584 585,347 Total $ 6,893 $ 1,558 $ 1,544 $ 20,105 $ 30,100 $ 5,245,196 $ 5,275,296 Acquired loans Commercial, financial, agricultural and other $ 1 $ — $ — $ 204 $ 205 $ 37,321 $ 37,526 Real estate construction — — — — — 5,970 5,970 Residential real estate 226 24 27 1,904 2,181 246,579 248,760 Commercial real estate — — — 1,042 1,042 200,153 201,195 Loans to individuals 46 12 11 15 84 5,308 5,392 Total $ 273 $ 36 $ 38 $ 3,165 $ 3,512 $ 495,331 $ 498,843 Nonaccrual Loans The previous tables summarize nonaccrual loans by loan segment. The Company generally places loans on nonaccrual status when the full and timely collection of interest or principal becomes uncertain, when part of the principal balance has been charged off and no restructuring has occurred, or the loans reach a certain number of days past due. Generally, loans 90 days or more past due are placed on nonaccrual status, except for consumer loans, which are placed on nonaccrual status at 150 days past due. When a loan is placed on nonaccrual, the accrued unpaid interest receivable is reversed against interest income and all future payments received are applied as a reduction to the loan principal. Generally, the loan is returned to accrual status when (a) all delinquent interest and principal becomes current under the terms of the loan agreement or (b) the loan is both well-secured and in the process of collection and collectability is no longer in doubt. Impaired Loans Management considers loans to be impaired when, based on current information and events, it is determined that the Company will not be able to collect all amounts due according to the loan contract, including scheduled interest payments. Determination of impairment is treated the same across all loan categories. When management identifies a loan as impaired, the impairment is measured based on the present value of expected future cash flows, discounted at the loan’s effective interest rate, except when the sole source for repayment of the loan is the operation or liquidation of collateral. When the loan is collateral dependent, the appraised value less estimated cost to sell is utilized. If management determines the value of the impaired loan is less than the recorded investment in the loan, impairment is recognized through an allowance estimate or a charge-off to the allowance. Troubled debt restructured loans on accrual status are also considered to be impaired loans. Troubled debt restructured loans are those loans whose terms have been renegotiated to provide a reduction or deferral of principal or interest as a result of the financial difficulties experienced by the borrower, who could not obtain comparable terms from alternate financing sources. When the ultimate collectability of the total principal of an impaired loan is in doubt and the loan is on nonaccrual status, all payments are applied to principal under the cost recovery method. When the ultimate collectability of the total principal of an impaired loan is not in doubt and the loan is on nonaccrual status, contractual interest is credited to interest income when received under the cash basis method. At March 31, 2019 and December 31, 2018 , there were no impaired loans held for sale. During the three months ended , March 31, 2019 and 2018 , there were no gains or losses recognized on sales of impaired loans. The following tables include the recorded investment and unpaid principal balance for impaired loans with the associated allowance amount, if applicable, as of March 31, 2019 and December 31, 2018 . Also presented are the average recorded investment in impaired loans and the related amount of interest recognized while the loan was considered impaired. Average balances are calculated using month-end balances of the loans for the period reported and are included in the table below based on their period-end allowance position. March 31, 2019 December 31, 2018 Recorded Unpaid Related Recorded Unpaid Related (dollars in thousands) Originated loans: With no related allowance recorded: Commercial, financial, agricultural and other $ 2,599 $ 9,100 $ 8,735 $ 16,442 Real estate construction — — — — Residential real estate 10,545 12,264 10,726 12,571 Commercial real estate 3,752 4,042 3,599 3,812 Loans to individuals 339 530 281 408 Subtotal 17,235 25,936 23,341 33,233 With an allowance recorded: Commercial, financial, agricultural and other 3,317 3,479 $ 1,012 3,042 3,181 $ 797 Real estate construction — — — — — — Residential real estate 713 713 119 486 495 107 Commercial real estate 7,017 7,035 914 1,866 1,878 596 Loans to individuals — — — — — — Subtotal 11,047 11,227 2,045 5,394 5,554 1,500 Total $ 28,282 $ 37,163 $ 2,045 $ 28,735 $ 38,787 $ 1,500 March 31, 2019 December 31, 2018 Recorded Unpaid Related Recorded Unpaid Related (dollars in thousands) Acquired loans With no related allowance recorded: Commercial, financial, agricultural and other $ 100 $ 100 $ 73 $ 73 Real estate construction — — — — Residential real estate 1,937 2,369 2,031 2,604 Commercial real estate 947 1,962 1,042 2,052 Loans to individuals 14 16 15 17 Subtotal 2,998 4,447 3,161 4,746 With an allowance recorded: Commercial, financial, agricultural and other — — $ — 131 131 $ 131 Real estate construction — — — — — — Residential real estate — — — — — — Commercial real estate — — — — — — Loans to individuals — — — — — — Subtotal — — — 131 131 131 Total $ 2,998 $ 4,447 $ — $ 3,292 $ 4,877 $ 131 For the Three Months Ended March 31, 2019 2018 Originated Loans Acquired Loans Originated Loans Acquired Loans Average Interest Average Interest Average Interest Average Interest (dollars in thousands) With no related allowance recorded: Commercial, financial, agricultural and other $ 2,707 $ 13 $ 439 $ — $ 8,130 $ 10 $ 411 $ — Real estate construction — — — — — — — — Residential real estate 10,798 72 1,981 1 10,401 63 678 1 Commercial real estate 3,994 36 982 1 5,510 31 907 — Loans to individuals 324 1 14 — 354 2 17 — Subtotal 17,823 122 3,416 2 24,395 106 2,013 1 With an allowance recorded: Commercial, financial, agricultural and other 3,068 3 — — 17,720 66 — — Real estate construction — — — — — — — — Residential real estate 604 5 — — 706 — 93 — Commercial real estate 3,278 1 — — 1,960 1 118 — Loans to individuals — — — — — — — — Subtotal 6,950 9 — — 20,386 67 211 — Total $ 24,773 $ 131 $ 3,416 $ 2 $ 44,781 $ 173 $ 2,224 $ 1 Unfunded commitments related to nonperforming loans were $0.1 million at March 31, 2019 and $1.6 million at December 31, 2018 . After consideration of the requirements to draw and available collateral related to these commitments, a reserve of $12 thousand was established for these off balance sheet exposures at both March 31, 2019 and December 31, 2018 . The following table provides detail as to the total troubled debt restructured loans and total commitments outstanding on troubled debt restructured loans: March 31, 2019 December 31, 2018 (dollars in thousands) Troubled debt restructured loans Accrual status $ 9,120 $ 8,757 Nonaccrual status 5,874 11,761 Total $ 14,994 $ 20,518 Commitments Letters of credit $ 60 $ 60 Unused lines of credit 263 1,027 Total $ 323 $ 1,087 The following tables provide detail, including specific reserves and reasons for modification, related to loans identified as troubled debt restructurings: For the Three Months Ended March 31, 2019 Type of Modification Number Extend Modify Modify Total Post- Specific (dollars in thousands) Commercial, financial, agricultural and other 1 $ — $ — $ 61 $ 61 $ 62 $ — Residential real estate 6 17 49 514 580 570 40 Commercial real estate 2 — 556 242 798 767 — Loans to individuals 3 — — 48 48 46 — Total 12 $ 17 $ 605 $ 865 $ 1,487 $ 1,445 $ 40 For the Three Months Ended March 31, 2018 Type of Modification Number Extend Modify Modify Total Post- Specific (dollars in thousands) Commercial, financial, agricultural and other 2 $ 4,709 $ — $ 162 $ 4,871 $ 3,942 $ 531 Residential real estate 11 20 75 346 441 404 17 Commercial real estate 1 3,017 — — 3,017 2,994 227 Loans to individuals 4 — 28 30 58 53 — Total 18 $ 7,746 $ 103 $ 538 $ 8,387 $ 7,393 $ 775 The troubled debt restructurings included in the above tables are also included in the impaired loan tables provided earlier in this note. Loans defined as modified due to a change in rate may include loans that were modified for a change in rate as well as a re-amortization of the principal and an extension of the maturity. For the three months ended March 31, 2019 and 2018 , $0.6 million and $0.1 million , respectively, of total rate modifications represent loans with modifications to the rate as well as payment as a result of re-amortization. For both 2019 and 2018 the changes in loan balances between the pre-modification balance and the post-modification balance are due to customer payments. A troubled debt restructuring is considered to be in default when a restructured loan is 90 days or more past due. The following table provides information related to loans that were restructured within the past twelve months and that were considered to be in default during the three months ended March 31 : 2019 2018 Number of Recorded Number of Recorded (dollars in thousands) Commercial, financial, agricultural and other — $ — 1 $ 940 Loans to individuals 1 10 — — Total 1 $ 10 1 $ 940 The following tables provide detail related to the allowance for credit losses: For the Three Months Ended March 31, 2019 Commercial, Real estate Residential Commercial Loans to Total (dollars in thousands) Allowance for credit losses: Originated loans: Beginning balance $ 19,235 $ 2,002 $ 3,934 $ 18,382 $ 4,033 $ 47,586 Charge-offs (483 ) — (136 ) (299 ) (1,110 ) (2,028 ) Recoveries 76 42 81 41 114 354 Provision (credit) 987 210 271 1,094 1,126 3,688 Ending balance 19,815 2,254 4,150 19,218 4,163 49,600 Acquired loans: Beginning balance 139 — 35 4 — 178 Charge-offs (526 ) — (45 ) — (5 ) (576 ) Recoveries 11 — 24 — 9 44 Provision (credit) 394 — 21 (4 ) (4 ) 407 Ending balance 18 — 35 — — 53 Total ending balance $ 19,833 $ 2,254 $ 4,185 $ 19,218 $ 4,163 $ 49,653 Ending balance: individually evaluated for impairment $ 1,012 $ — $ 119 $ 914 $ — $ 2,045 Ending balance: collectively evaluated for impairment 18,821 2,254 4,066 18,304 4,163 47,608 Loans: Ending balance 1,180,320 389,387 1,565,349 2,138,376 597,638 5,871,070 Ending balance: individually evaluated for impairment 5,627 — 3,938 11,111 — 20,676 Ending balance: collectively evaluated for impairment 1,174,693 389,387 1,561,411 2,127,265 597,638 5,850,394 For the Three Months Ended March 31, 2018 Commercial, Real estate Residential Commercial Loans to Total (dollars in thousands) Allowance for credit losses: Originated loans: Beginning balance $ 23,418 $ 1,349 $ 2,753 $ 17,328 $ 3,404 $ 48,252 Charge-offs (290 ) — (455 ) (168 ) (1,169 ) (2,082 ) Recoveries 256 1 75 69 195 596 Provision (credit) 4,148 (236 ) 768 1,265 986 6,931 Ending balance 27,532 1,114 3,141 18,494 3,416 53,697 Acquired loans: Beginning balance 11 — 6 29 — 46 Charge-offs — — (16 ) — (4 ) (20 ) Recoveries 7 6 17 — 7 37 Provision (credit) 2 (6 ) 6 (27 ) (3 ) (28 ) Ending balance 20 — 13 2 — 35 Total ending balance $ 27,552 $ 1,114 $ 3,154 $ 18,496 $ 3,416 $ 53,732 Ending balance: individually evaluated for impairment $ 9,045 $ — $ 287 $ 2,141 $ — $ 11,473 Ending balance: collectively evaluated for impairment 18,507 1,114 2,867 16,355 3,416 42,259 Loans: Ending balance 1,131,594 246,961 1,434,623 2,027,072 541,055 5,381,305 Ending balance: individually evaluated for impairment 33,278 — 6,853 10,360 — 50,491 Ending balance: collectively evaluated for impairment 1,098,316 246,961 1,427,770 2,016,712 541,055 5,330,814

Leases Leases

Leases Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases of Lessee Disclosure [Text Block]	Note 9 Leases On January 1, 2019, the Company adopted ASU 2016-02 “Leases” (Topic 842) and all subsequent ASUs that modified Topic 842 using the transition option provided in ASU 2018-11, which provides for the modified retrospective approach. Under this approach comparative periods were not restated and no cumulative effect adjustment to the opening balance of retained earnings was required. First Commonwealth has elected to apply certain practical expedients provided under the standard including (i) to not apply the requirements in the new standard to short-term leases (ii) to not reassess the lease classification for any expired or existing lease (iii) to account for lease and non-lease components separately (iv) to not reassess initial direct costs for any existing leases. The impact of this standard primarily relates to operating leases of certain real estate properties, primarily certain branch and ATM locations and office space. First Commonwealth has no material leasing arrangements for which it is the lessor of property or equipment. Adoption of this standard resulted in the Company recognizing an ROU asset of $38.5 million and a lease liability of $41.8 million on January 1, 2019. The following table represents the Consolidated Statements of Condition classification of the Company’s ROU assets and lease liabilities, lease costs and other lease information as of and for the three months ended March 31, 2019 (dollars in thousands). Balance sheet: Operating lease asset classified as premises and equipment $ 47,566 Operating lease liability classified as other liabilities 51,371 Income statement: Operating lease cost classified as occupancy and equipment expense $ 1,337 Weighted average lease term, in years 16.28 Weighted average discount rate 3.49 % Operating cash flows $ 1,119 The ROU assets and lease liabilities are impacted by the length of the lease term and the discount rate used to present value the minimum lease payments. First Commonwealth's lease agreements often include one or more options to renew at the Company's discretion. If we consider the renewal option to be reasonably certain, we include the extended term in the calculation of the ROU asset and lease liability. First Commonwealth uses incremental borrowing rates when calculating the lease liability because the rate implicit in the lease is not readily determinable. The incremental borrowing rate used by First Commonwealth is an amortizing loan rate obtained from the Federal Home Loan Bank ("FHLB") of Pittsburgh. This rate is consistent with a collateralized borrowing rate and is available for terms similar to the lease payment schedules. Future minimum payments for operating leases with initial or remaining terms of one year or more as of March 31, 2019 were as follows (dollars in thousands): For the twelve months ended: March 31, 2020 $ 4,499 March 31, 2021 4,517 March 31, 2022 4,480 March 31, 2023 4,413 March 31, 2024 4,370 Thereafter 46,528 Total future minimum lease payments 68,807 Less remaining imputed interest 17,436 Present value of future minimum lease payments $ 51,371

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes In accordance with FASB ASC Topic 740-10, “Accounting for Uncertainty in Income Taxes”, at March 31, 2019 and December 31, 2018 , First Commonwealth had no material unrecognized tax benefits or accrued interest and penalties. If applicable, First Commonwealth will record interest and penalties as a component of noninterest expense. First Commonwealth is subject to routine audits of our tax returns by the Internal Revenue Service (“IRS”) as well as all states in which we conduct business. Generally, tax years prior to the year ended December 31, 2015 are no longer open to examination by federal and state taxing authorities. During the first quarter of 2018, First Commonwealth adopted ASU No. 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220)". Adoption of this ASU reclassified the stranded other accumulated income of $1.3 million resulting from the tax reform passed in December 2017 from accumulated other comprehensive income to retained earnings. There was no impact to total equity as a result of the adoption of this update.

Fair Values of Assets and Liabi

Fair Values of Assets and Liabilities	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Values of Assets and Liabilities	Fair Values of Assets and Liabilities FASB ASC Topic 820, “Fair Value Measurements and Disclosures,” requires disclosures for non-financial assets and non-financial liabilities, except for items that are recognized or disclosed at fair value in the financial statements on a recurring basis (at least annually). All non-financial assets are included either as a separate line item on the Consolidated Statements of Financial Condition or in the “Other assets” category of the Consolidated Statements of Financial Condition. Currently, First Commonwealth does not have any non-financial liabilities to disclose. FASB ASC Topic 825, “Financial Instruments”, permits entities to irrevocably elect to measure select financial instruments and certain other items at fair value. The unrealized gains and losses are required to be included in earnings each reporting period for the items that fair value measurement is elected. First Commonwealth has elected not to measure any existing financial instruments at fair value under FASB ASC Topic 825; however, in the future we may elect to adopt this guidance for select financial instruments. In accordance with FASB ASC Topic 820, First Commonwealth groups financial assets and financial liabilities measured at fair value in three levels based on the principal markets in which the assets and liabilities are transacted and the observability of the data points used to determine fair value. These levels are: • Level 1 – Valuations for assets and liabilities traded in active exchange markets, such as the New York Stock Exchange (“NYSE”). Valuations are obtained from readily available pricing sources for market transactions involving identical assets or liabilities. • Level 2 – Valuations for assets and liabilities traded in less active dealer or broker markets. Valuations are obtained for identical or comparable assets or liabilities from alternative pricing sources with reasonable levels of price transparency. Level 2 includes Obligations of U.S. Government securities issued by Agencies and Sponsored Enterprises, Obligations of States and Political Subdivisions, corporate securities, FHLB stock, loans held for sale, interest rate derivatives (including interest rate caps, interest rate collars, interest rate swaps and risk participation agreements), certain other real estate owned and certain impaired loans. Level 2 investment securities are valued by a recognized third party pricing service using observable inputs. The model used by the pricing service varies by asset class and incorporates available market, trade and bid information as well as cash flow information when applicable. Because many fixed-income investment securities do not trade on a daily basis, the model uses available information such as benchmark yield curves, benchmarking of like investment securities, sector groupings and matrix pricing. The model will also use processes such as an option adjusted spread to assess the impact of interest rates and to develop prepayment estimates. Market inputs normally used in the pricing model include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data including market research publications. Management validates the market values provided by the third party service by having another recognized pricing service price 100% of the securities on an annual basis and a random sample of securities each quarter, monthly monitoring of variances from prior period pricing and, on a monthly basis, evaluating pricing changes compared to expectations based on changes in the financial markets. Other investments recorded in the Consolidated Statements of Financial Condition are primarily comprised of FHLB stock whose estimated fair value is based on its par value. Additional information on FHLB stock is provided in Note 7, “Impairment of Investment Securities.” Loans held for sale primarily include residential mortgage loans originated for sale in the secondary mortgage market. The estimated fair value for these loans was determined on the basis of rates obtained in the respective secondary market. Loans held for sale could also include commercial loans for which fair value is determined using an executed trade or market bid obtained from potential buyers. Interest rate derivatives are reported at an estimated fair value utilizing Level 2 inputs and are included in other assets and other liabilities, and consist of interest rate swaps where there is no significant deterioration in the counterparties' (loan customers') credit risk since origination of the interest rate swap as well as interest rate caps, interest rate collars and risk participation agreements. First Commonwealth values its interest rate swap and cap positions using a yield curve by taking market prices/rates for an appropriate set of instruments. The set of instruments currently used to determine the U.S. Dollar yield curve includes cash LIBOR rates from overnight to one year, Eurodollar futures contracts and swap rates from one year to thirty years. These yield curves determine the valuations of interest rate swaps. Interest rate derivatives are further described in Note 12, “Derivatives.” For purposes of potential valuation adjustments to our derivative positions, First Commonwealth evaluates the credit risk of its counterparties as well as our own credit risk. Accordingly, we have considered factors such as the likelihood of default, expected loss given default, net exposures and remaining contractual life, among other things, in determining if any fair value adjustments related to credit risk are required. We review our counterparty exposure quarterly, and when necessary, appropriate adjustments are made to reflect the exposure. We also utilize this approach to estimate our own credit risk on derivative liability positions. In 2019 , we have not realized any losses due to a counterparty's inability to pay any uncollateralized positions. Interest rate derivatives also include interest rate forwards entered into to hedge residential mortgage loans held for sale and the related interest-rate lock commitments. This includes forward commitments to sell mortgage loans. The fair value of these derivative financial instruments are based on derivative market data inputs as of the valuation date and the underlying value of mortgage loans for rate lock commitments. In addition, the Company hedges foreign currency risk through the use of foreign exchange forward contracts. The fair value of foreign exchange forward contracts is based on the differential between the contract price and the market-based forward rate. The estimated fair value for other real estate owned included in Level 2 is determined by either an independent market-based appraisal less estimated costs to sell or an executed sales agreement. • Level 3 – Valuations for assets and liabilities that are derived from other valuation methodologies, including option pricing models, discounted cash flow models and similar techniques, and not based on market exchange, dealer or broker traded transactions. If the inputs used to provide the valuation are unobservable and/or there is very little, if any, market activity for the security or similar securities, the securities would be considered Level 3 securities. Level 3 valuations incorporate certain assumptions and projections in determining the fair value assigned to such assets or liabilities. The assets included in Level 3 are pooled trust preferred collateralized debt obligations, non-marketable equity investments, certain interest rate derivatives, certain other real estate owned and certain impaired loans. The estimated fair value of other investments included in Level 3 is based on carrying value as these securities do not have a readily determinable fair value. The estimated fair value of limited partnership investments included in Level 3 is based on par value. For interest rate derivatives included in Level 3, the fair value incorporates credit risk by considering such factors as likelihood of default and expected loss given default based on the credit quality of the underlying counterparties (loan customers). In accordance with ASU No. 2011 -4 , the following table provides information related to quantitative inputs and assumptions used in March 31, 2019 Level 3 fair value measurements. Fair Value (dollars Valuation Unobservable Inputs Range / Other Investments $ 1,670 CarryingValue N/A N/A Impaired Loans 1,044 (a) Reserve study Discount rate 10.00% Gas per MMBTU $2.61 - $3.49 (b) Oil per BBL/d $47.09 - $53.14 (b) 3,187 (a) Discounted Cash Flow Discount Rate 1.9% - 9.5% Limited Partnership Investments 3,200 Par Value N/A N/A (a) The remainder of impaired loans valued using Level 3 inputs are not included in this disclosure as the values of those loans are based on bankruptcy agreement documentation. (b) Unobservable inputs are defined as follows: MMBTU - million British thermal units; BBL/d - barrels per day. The discount rate is the significant unobservable input used in the fair value measurement of impaired loans. Significant increases in this rate would result in a decrease in the estimated fair value of the loans, while a decrease in this rate would result in a higher fair value measurement. Other unobservable inputs in the fair value measurement of impaired loans relate to gas, oil and natural gas prices. Increases in these prices would result in an increase in the estimated fair value of the loans, while a decrease in these prices would result in a lower fair value measurement. The tables below present the balances of assets and liabilities measured at fair value on a recurring basis: March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities - Residential $ — $ 9,246 $ — $ 9,246 Mortgage-Backed Securities - Commercial — 168,120 — 168,120 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities - Residential — 653,966 — 653,966 Other Government-Sponsored Enterprises — 10,006 — 10,006 Obligations of States and Political Subdivisions — 28,214 — 28,214 Corporate Securities — 23,549 — 23,549 Total Securities Available for Sale — 893,101 — 893,101 Other Investments — 23,708 1,670 25,378 Loans Held for Sale — 9,627 — 9,627 Other Assets(a) — 7,613 3,200 10,813 Total Assets $ — $ 934,049 $ 4,870 $ 938,919 Other Liabilities(a) $ — $ 7,868 $ — $ 7,868 Total Liabilities $ — $ 7,868 $ — $ 7,868 (a) Hedging and non-hedging interest rate derivatives and limited partnership investments December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities - Residential $ — $ 9,406 $ — $ 9,406 Mortgage-Backed Securities - Commercial — 167,744 — 167,744 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities - Residential — 673,361 — 673,361 Other Government-Sponsored Enterprises — 10,012 — 10,012 Obligations of States and Political Subdivisions — 27,712 — 27,712 Corporate Securities — 21,012 — 21,012 Total Securities Available for Sale — 909,247 — 909,247 Other Investments — 30,456 1,670 32,126 Loans Held for Sale — 11,881 — 11,881 Other Assets(a) — 1,769 2,696 4,465 Total Assets $ — $ 953,353 $ 4,366 $ 957,719 Other Liabilities(a) $ — $ 2,081 $ — $ 2,081 Total Liabilities $ — $ 2,081 $ — $ 2,081 (a) Hedging and non-hedging interest rate derivatives and limited partnership investments For the three months ended March 31 , changes in Level 3 assets and liabilities measured at fair value on a recurring basis are summarized as follows: 2019 Other Investments Other Total (dollars in thousands) Balance, beginning of period $ 1,670 $ 2,696 $ 4,366 Total gains or losses Included in earnings — — — Included in other comprehensive income — (47 ) (47 ) Purchases, issuances, sales and settlements Purchases — 551 551 Issuances — — — Sales — — — Settlements — — — Transfers from Level 3 — — — Transfers into Level 3 — — — Balance, end of period $ 1,670 $ 3,200 $ 4,870 2018 Pooled Trust Preferred Collateralized Debt Obligations Other Investments Other Total (dollars in thousands) Balance, beginning of period $ 23,646 $ 1,670 $ 2,143 $ 27,459 Total gains or losses Included in earnings 2,840 — — 2,840 Included in other comprehensive income 4,529 — — 4,529 Purchases, issuances, sales and settlements Purchases — — 149 149 Issuances — — — — Sales — — — — Settlements (16,883 ) — — (16,883 ) Transfers from Level 3 — — — — Transfers into Level 3 — — — — Balance, end of period $ 14,132 $ 1,670 $ 2,292 $ 18,094 During the three months ended March 31, 2019 and 2018 , there were no transfers between fair value Levels 1 , 2 or 3. There were no gains or losses included in earnings for the periods presented that are attributable to the change in realized gains (losses) relating to assets held at March 31, 2019 and 2018 . The tables below present the balances of assets measured at fair value on a nonrecurring basis at: March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Impaired loans $ — $ 14,391 $ 14,849 $ 29,240 Other real estate owned — 4,300 — 4,300 Total Assets $ — $ 18,691 $ 14,849 $ 33,540 December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Impaired loans $ — $ 15,076 $ 15,320 $ 30,396 Other real estate owned — 4,035 — 4,035 Total Assets $ — $ 19,111 $ 15,320 $ 34,431 The following gains(losses) were realized on the assets measured on a nonrecurring basis: For the Three Months Ended March 31, 2019 2018 (dollars in thousands) Impaired loans $ (969 ) $ (7,850 ) Other real estate owned (49 ) (30 ) Total losses $ (1,018 ) $ (7,880 ) Impaired loans over $100 thousand are individually reviewed to determine the amount of each loan considered to be at risk of non-collection. The fair value for impaired loans that are collateral based is determined by reviewing real property appraisals, equipment valuations, accounts receivable listings and other financial information. A discounted cash flow analysis is performed to determine fair value for impaired loans when an observable market price or a current appraisal is not available. For real estate secured loans, First Commonwealth’s loan policy requires updated appraisals be obtained at least every twelve months on all impaired loans with balances of $250 thousand and over. For real estate secured loans with balances under $250 thousand , we rely on broker price opinions. For non-real estate secured assets, the Company normally relies on third party valuations specific to the collateral type. The fair value for other real estate owned, determined by either an independent market-based appraisal less estimated costs to sell or an executed sales agreement, is classified as Level 2. The fair value for other real estate owned, determined using an internal valuation, is classified as Level 3. OREO has a current carrying value of $4.0 million as of March 31, 2019 and consists primarily of residential and commercial real estate properties in Pennsylvania. We review whether events and circumstances subsequent to a transfer to other real estate owned have occurred that indicate the balance of those assets may not be recoverable. If events and circumstances indicate further impairment we will record a charge to the extent that the carrying value of the assets exceed their fair values, less estimated cost to sell, as determined by valuation techniques appropriate in the circumstances. Certain other assets and liabilities, including goodwill and core deposit intangibles, are measured at fair value on a nonrecurring basis; that is, the instruments are not measured at fair value on an ongoing basis but are subject to fair value adjustments only in certain circumstances. Additional information related to goodwill is provided in Note 13, “Goodwill.” There were no other assets or liabilities measured at fair value on a nonrecurring basis during the three months ended March 31, 2019 . FASB ASC 825-10, “Transition Related to FSP FAS 107 -1 ” and APB 28 -1 , “Interim Disclosures about Fair Value of Financial Instruments,” requires disclosure of the fair value of financial assets and financial liabilities, including those financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or nonrecurring basis. The methodologies for estimating the fair value of financial assets and financial liabilities that are measured at fair value on a recurring or nonrecurring basis are as discussed above. The methodologies for other financial assets and financial liabilities are discussed below. Cash and due from banks and interest-bearing bank deposits : The carrying amounts for cash and due from banks and interest-bearing bank deposits approximate the estimated fair values of such assets. Securities : Fair values for securities available for sale and held to maturity are based on quoted market prices, if available. If quoted market prices are not available, fair values are based on quoted market prices of comparable instruments. Pooled trust preferred collateralized debt obligations values are derived from other valuation methodologies, including option pricing models, discounted cash flow models and similar techniques, and not based on market exchange, dealer or broker traded transactions. These valuations incorporate certain assumptions and projections in determining the fair value assigned to each instrument. The carrying value of other investments, which includes FHLB stock and other equity investments, is considered a reasonable estimate of fair value. Loans : The fair values of all loans are estimated by discounting the estimated future cash flows using interest rates currently offered for loans with similar terms to borrowers of similar credit quality adjusted for past due and nonperforming loans. Loans held for sale : The estimated fair value of loans held for sale is based on market bids obtained from potential buyers. Off-balance sheet instruments : Many of First Commonwealth’s off-balance sheet instruments, primarily loan commitments and standby letters of credit, are expected to expire without being drawn upon; therefore, the commitment amounts do not necessarily represent future cash requirements. FASB ASC Topic 460, “Guarantees” clarified that a guarantor is required to recognize, at the inception of a guarantee, a liability for the fair value of the obligation undertaken in issuing the guarantee. The carrying amount and fair value for standby letters of credit was $0.3 million and $0.2 million at March 31, 2019 and December 31, 2018 , respectively. See Note 5, “Commitments and Contingent Liabilities,” for additional information. Deposit liabilities : The estimated fair value of demand deposits, savings accounts and money market deposits is the amount payable on demand at the reporting date because of the customers’ ability to withdraw funds immediately. The carrying value of variable rate time deposit accounts and certificates of deposit approximate their fair values at the report date. Also, fair values of fixed rate time deposits for both periods are estimated by discounting the future cash flows using interest rates currently being offered and a schedule of aggregated expected maturities. Short-term borrowings : The fair values of borrowings from the FHLB were estimated based on the estimated incremental borrowing rate for similar type borrowings. The carrying amounts of other short-term borrowings such as federal funds purchased and securities sold under agreement to repurchase were used to approximate fair value due to the short-term nature of the borrowings. Subordinated debt, long-term debt and capital lease obligation : The fair value is estimated by discounting the future cash flows using First Commonwealth’s estimate of the current market rate for similar types of borrowing arrangements or an announced redemption price. The following table presents carrying amounts and fair values of First Commonwealth’s financial instruments: March 31, 2019 Fair Value Measurements Using: Carrying Total Level 1 Level 2 Level 3 (dollars in thousands) Financial assets Cash and due from banks $ 100,724 $ 100,724 $ 100,724 $ — $ — Interest-bearing deposits 23,168 23,168 23,168 — — Securities available for sale 893,101 893,101 — 893,101 — Securities held to maturity 384,909 380,443 — 380,443 — Other investments 25,378 25,378 — 23,708 1,670 Loans held for sale 9,627 9,627 — 9,627 — Loans 5,871,070 5,921,319 — 14,391 5,906,928 Financial liabilities Deposits 6,130,760 6,135,980 — 6,135,980 — Short-term borrowings 565,616 565,522 — 565,522 — Subordinated debt 170,328 169,764 — — 169,764 Long-term debt 7,395 7,701 — 7,701 — Capital lease obligation 7,118 7,118 — 7,118 — December 31, 2018 Fair Value Measurements Using: Carrying Total Level 1 Level 2 Level 3 (dollars in thousands) Financial assets Cash and due from banks $ 95,934 $ 95,934 $ 95,934 $ — $ — Interest-bearing deposits 3,013 3,013 3,013 — — Securities available for sale 909,247 909,247 — 909,247 — Securities held to maturity 393,855 383,993 — 383,993 — Other investments 32,126 32,126 — 30,456 1,670 Loans held for sale 11,881 11,881 — 11,881 — Loans 5,774,139 5,821,791 — 15,076 5,806,715 Financial liabilities Deposits 5,897,992 5,904,147 — 5,904,147 — Short-term borrowings 721,823 721,532 — 721,532 — Subordinated debt 170,288 168,067 — — 168,067 Long-term debt 7,551 7,720 — 7,720 — Capital lease obligation 7,217 7,217 — 7,217 —

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives Derivatives Not Designated as Hedging Instruments First Commonwealth is a party to interest rate derivatives that are not designated as hedging instruments. These derivatives relate to interest rate swaps that First Commonwealth enters into with customers to allow customers to convert variable rate loans to a fixed rate. First Commonwealth pays interest to the customer at a floating rate on the notional amount and receives interest from the customer at a fixed rate for the same notional amount. At the same time the interest rate swap is entered into with the customer, an offsetting interest rate swap is entered into with another financial institution. First Commonwealth pays the other financial institution interest at the same fixed rate on the same notional amount as the swap entered into with the customer, and receives interest from the financial institution for the same floating rate on the same notional amount. The changes in the fair value of the swaps offset each other, except for the credit risk of the counterparties, which is determined by taking into consideration the risk rating, probability of default and loss given default for all counterparties. We have 31 risk participation agreements with financial institution counterparties for interest rate swaps related to loans in which we are a participant. The risk participation agreements provide credit protection to the financial institution should the borrower fail to perform on its interest rate derivative contract with the financial institution. We have nine risk participation agreements with financial institution counterparties for interest rate swaps related to loans in which we are the lead bank. The risk participation agreement provides credit protection to us should the borrower fail to perform on its interest rate derivative contract with us. First Commonwealth is also party to interest rate caps and collars that are not designated as hedging instruments. The interest rate caps relate to contracts that First Commonwealth enters into with loan customers that provide a maximum interest rate on their variable rate loan. At the same time the interest rate cap is entered into with the customer, First Commonwealth enters into an offsetting interest rate cap with another financial institution. The notional amount and maximum interest rate on both interest cap contracts are identical. The interest rate collars relate to contracts that First Commonwealth enters into with loan customers that provides both a maximum and minimum interest rate on their variable rate loan. At the same time the interest rate collar is entered into with the customer, First Commonwealth enters into an offsetting interest rate collar with another financial institution. The notional amount and the maximum and minimum interest rates on both interest collar contracts are identical. The fee received, less the estimate of the loss for the credit exposure, was recognized in earnings at the time of the transaction. Derivatives Designated as Hedging Instruments In 2015, the Company entered into an interest rate swap contract that was designated as a cash flow hedge. This contract, which had a notional amount of $65.0 million, matured on March 4, 2019. The periodic net settlement of interest rate swaps was recorded as an adjustment to "Interest and fees on loans" in the Consolidated Statements of Income. For the three months ended March 31, 2019 there was a $0.1 million negative impact on net interest income as a result of these interest rate swaps. The Company also enters into interest rate lock commitments in conjunction with its mortgage origination business. These are commitments to originate loans whereby the interest rate on the loan is determined prior to funding and the customers have locked into that interest rate. The Company locks the rate in with an investor and commits to deliver the loan if settlement occurs (“best efforts”) or commits to deliver the locked loan in a binding (“mandatory”) delivery program with an investor. Loans under mandatory rate lock commitments are covered under forward sales contracts of mortgage-backed securities (“MBS”). Forward sales contracts of MBS are recorded at fair value with changes in fair value recorded in "Other noninterest expense" in the Consolidated Statements of Income. The impact to noninterest income for the three months ended March 31, 2019 was a decrease of $0.4 million . Interest rate lock commitments and commitments to deliver loans to investors are considered derivatives. The market value of interest rate lock commitments and best efforts contracts are not readily ascertainable with precision because they are not actively traded in stand-alone markets. We determine the fair value of rate lock commitments and delivery contracts by measuring the fair value of the underlying asset, which is impacted by current interest rates and taking into consideration the probability that the rate lock commitments will close or will be funded. At March 31, 2019 , the underlying funded mortgage loan commitments had a carrying value of $7.2 million and a fair value of $8.2 million , while the underlying unfunded mortgage loan commitments had a notional amount of $25.2 million . At December 31, 2018 , the underlying funded mortgage loan commitments had a carrying value of $6.9 million and a fair value of $7.6 million , while the underlying unfunded mortgage loan commitments had a notional amount of $9.9 million . The interest rate lock commitments decreased other noninterest income by $0.1 million for the three months ended March 31, 2019 . In addition, a small amount of interest income on loans is exposed to changes in foreign exchange rates. Several commercial borrowers have a portion of their operations outside of the United States and borrow funds on a short-term basis to fund those operations. In order to reduce the risk related to the translation of foreign denominated transactions into U.S. dollars, the Company enters into foreign exchange forward contracts. These contracts relate principally to the Euro and the Canadian dollar. The contracts are recorded at fair value with changes in fair value recorded in "Other noninterest expense" in the Consolidated Statements of Income. The impact on other noninterest expense for the three months ended March 31, 2019 totaled $2 thousand . At March 31, 2019 and December 31, 2018 , the underlying loans had a carrying value of $1.8 million and $1.9 million , respectively, and a fair value of $1.8 million and $1.9 million , respectively. The following table depicts the credit value adjustment recorded related to the notional amount of derivatives outstanding as well as the notional amount of risk participation agreements participated to other banks: March 31, 2019 December 31, 2018 (dollars in thousands) Derivatives not Designated as Hedging Instruments Credit value adjustment $ (29 ) $ (3 ) Notional amount: Interest rate derivatives 370,693 411,645 Interest rate caps 36,028 36,111 Interest rate collars 35,354 — Risk participation agreements 170,016 162,139 Sold credit protection on risk participation agreements (46,871 ) (59,315 ) Interest rate options 25,215 9,900 Derivatives Designated as Hedging Instruments Interest rate swaps: Fair value adjustment — (133 ) Notional amount — 65,000 Interest rate forwards: Fair value adjustment (234 ) (170 ) Notional amount 30,000 15,000 Foreign exchange forwards: Fair value adjustment 7 (6 ) Notional amount 1,797 1,927 The table below presents the amount representing the change in the fair value of derivative assets and derivative liabilities attributable to credit risk included in "Other income" on the Consolidated Statements of Income: For the Three Months Ended March 31, 2019 2018 (dollars in thousands) Non-hedging interest rate derivatives (Decrease) increase in other income $ (470 ) $ 789 Hedging interest rate derivatives Decrease in interest and fees on loans (118 ) (81 ) Increase in other expense 7 — Hedging interest rate forwards Decrease in other income (64 ) — Decrease in other expense — (62 ) Hedging foreign exchange forwards Increase (decrease) in other expense 2 (3 ) The fair value of our derivatives is included in a table in Note 11, “Fair Values of Assets and Liabilities,” in the line items “Other assets” and “Other liabilities.”

Goodwill

Goodwill	3 Months Ended
	Mar. 31, 2019
Goodwill Disclosure [Abstract]
Goodwill	Goodwill FASB ASC Topic 350-20, “Intangibles – Goodwill and Other” requires an annual valuation of the fair value of a reporting unit that has goodwill and a comparison of the fair value to the book value of equity to determine whether the goodwill has been impaired. Goodwill is also required to be tested on an interim basis if an event or circumstance indicates that it is more likely than not that an impairment loss has been incurred. When triggering events or circumstances indicate that goodwill testing is required, an assessment of qualitative factors can be completed before performing the two step goodwill impairment test. ASU No. 2011-8 provides that if an assessment of qualitative factors determines it is more likely than not that the fair value of a reporting unit exceeds its carrying amount, then the two step goodwill impairment test is not required. We consider First Commonwealth to be one reporting unit. The carrying amount of goodwill as of March 31, 2019 and December 31, 2018 was $274.2 million . No impairment charges on goodwill or other intangible assets were incurred in 2019 or 2018 . We test goodwill for impairment as of November 30th each year and again at any quarter-end if any material events occur during a quarter that may affect goodwill. As of March 31, 2019 , goodwill was not considered impaired; however, changing economic conditions that may adversely affect our performance, the fair value of our assets and liabilities, or our stock price could result in impairment, which could adversely affect earnings in future periods. Management will continue to monitor events that could impact this conclusion in the future.

Subordinated Debentures Subordi

Subordinated Debentures Subordinated Debentures Outstanding	3 Months Ended
	Mar. 31, 2019
Subordinated Debentures Outstanding [Abstract]
Subordinated Borrowings Disclosure [Text Block]	Subordinated Debentures Subordinated debentures outstanding are as follows: March 31, 2019 December 31, 2018 Due Amount Rate Amount Rate (dollars in thousands) Owed to: First Commonwealth Bank 2028 $ 49,152 4.875% until June 1, 2023, then LIBOR + 1.845% $ 49,131 4.875% until June 1, 2023, then LIBOR + 1.845% First Commonwealth Bank 2033 $ 49,009 5.50% until June 1, 2028, then LIBOR + 2.37% $ 48,990 5.50% until June 1, 2028, then LIBOR + 2.37% First Commonwealth Capital Trust II 2034 $ 30,929 LIBOR + 2.85% $ 30,929 LIBOR + 2.85% First Commonwealth Capital Trust III 2034 41,238 LIBOR + 2.85% 41,238 LIBOR + 2.85% Total $ 170,328 $ 170,288 On May 21, 2018, First Commonwealth issued ten-year subordinated notes with an aggregate principal amount of $50.0 million and a fixed-to-floating rate of 4.875%. The rate remains fixed until June 1, 2023, then adjusts on a quarterly basis to LIBOR + 1.845%. The Bank may redeem the notes, beginning with the interest payment due on June 1, 2023, in whole or in part at a redemption price equal to 100% of the principal amount of the subordinated notes, plus accrued and unpaid interest to the date of redemption. Deferred issuance costs of $0.9 million are being amortized on a straight-line basis over the term of the notes. On May 21, 2018, First Commonwealth issued fifteen-year subordinated notes with an aggregate principal amount of $50.0 million and a fixed-to-floating rate of 5.50%. The rate remains fixed until June 1, 2028, then adjusts on a quarterly basis to LIBOR + 2.37%. The Bank may redeem the notes, beginning with the interest payment due on June 1, 2028, in whole or in part at a redemption price equal to 100% of the principal amount of the subordinated notes, plus accrued and unpaid interest to the date of redemption. Deferred issuance costs of $1.1 million are being amortized on a straight-line basis over the term of the notes. First Commonwealth currently has two trusts, First Commonwealth Capital Trust II and First Commonwealth Capital Trust III, of which 100% of the common equity is owned by First Commonwealth. The trusts were formed for the purpose of issuing company obligated mandatorily redeemable capital securities to third-party investors and investing the proceeds from the sale of the capital securities solely in junior subordinated debt securities (“subordinated debentures”) of First Commonwealth. The subordinated debentures held by each trust are the sole assets of the trust. Interest on the debentures issued to First Commonwealth Capital Trust III is paid quarterly at a floating rate of LIBOR + 2.85% which is reset quarterly. Subject to regulatory approval, First Commonwealth may redeem the debentures, in whole or in part, at its option on any interest payment date at a redemption price equal to 100% of the principal amount of the debentures, plus accrued and unpaid interest to the date of the redemption. Deferred issuance costs of $0.6 million are being amortized on a straight-line basis over the term of the securities. Interest on the debentures issued to First Commonwealth Capital Trust II is paid quarterly at a floating rate of LIBOR + 2.85%, which is reset quarterly. Subject to regulatory approval, First Commonwealth may redeem the debentures, in whole or in part, at its option at a redemption price equal to 100% of the principal amount of the debentures, plus accrued and unpaid interest to the date of the redemption. Deferred issuance costs of $0.5 million are being amortized on a straight-line basis over the term of the securities.

New Accounting Pronouncements (

New Accounting Pronouncements (Notes)	3 Months Ended
	Mar. 31, 2019
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments,” which amends the guidance for recognizing credit losses from an “incurred loss” methodology that delays recognition of credit losses until it is probable a loss has been incurred to an expected credit loss methodology. The Current Expected Credit Loss ("CECL") methodology requires the use of the modified retrospective transition method by means of a cumulative-effect adjustment to equity as of the beginning of the period in which the guidance is adopted. The standard is effective for the Company as of January 1, 2020. We have established a CECL implementation team, which includes members from the finance and credit areas, with oversight by the Chief Executive Officer, Chief Financial Officer and Chief Credit Officer. During the third quarter of 2018, Management completed the implementation of third party software to assist with this ASU. In the fourth quarter of 2018, a third party was engaged to assist with evaluation of data and methodologies related to this standard. Management continued its implementation plan during the first quarter of 2019 with primary emphasis on the evaluation of data and methodologies. Management is currently evaluating the impact of the amended guidance on First Commonwealth’s financial condition or results of operations. In January 2017, the FASB issued ASU No. 2017-04, "Intangibles-Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment" which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under this ASU, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. Impairment should be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to the reporting unit. Income tax effects from any tax deductible goodwill should be taken into consideration of the carrying amount of the reporting unit when measuring for goodwill impairment, if applicable. An entity still has the option to perform the qualitative assessment for the reporting unit to determine if the quantitative impairment test is necessary. This standard is effective for interim and annual periods for fiscal years beginning after December 15, 2019. The adoption of this ASU is not expected to have a material impact on First Commonwealth’s financial condition or results of operations. In August 2018, the FASB issued ASU No. 2018-13, "Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement." This ASU updates disclosure requirements for fair value measurements, including elimination of the disclosure related to the amount and reason for transfers between Level 1 and Level 2 of the fair value hierarchy. ASU No. 2018-13 is effective for interim and annual reporting periods beginning after December 15, 2019. Adoption of this ASU will not have a material impact on First Commonwealth's financial condition or results of operations, as it relates only to disclosure requirements.

Subsequent Event (Notes)

Subsequent Event (Notes)	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Event On April 22, 2019, the Company announced that its banking subsidiary, First Commonwealth Bank, has signed a definitive agreement to acquire 14 branches located in State College, Lock Haven, Williamsport and Lewisburg, Pennsylvania, with approximately $525 million of deposits and $120 million of retail and business loans from Santander Bank, N.A. The transaction is subject to regulatory approval and is expected to close in the third quarter of 2019.

Supplemental Comprehensive In_2

Supplemental Comprehensive Income Disclosures (Tables)	3 Months Ended
	Mar. 31, 2019
Supplemental Comprehensive Income Disclosures [Abstract]
Supplemental Comprehensive Income Disclosures	The following table identifies the related tax effects allocated to each component of other comprehensive income (“OCI”) in the Consolidated Statements of Comprehensive Income. Reclassification adjustments related to securities available for sale are included in the "Net securities gains" line and reclassification adjustments related to losses on derivatives are included in the "Other operating expenses" line in the Consolidated Statements of Income. For the Three Months Ended March 31, 2019 2018 Pretax Amount Tax (Expense) Benefit Net of Tax Amount Pretax Amount Tax (Expense) Benefit Net of Tax Amount (dollars in thousands) Unrealized gains (losses) on securities: Unrealized holding gains (losses) on securities arising during the period $ 9,030 $ (1,896 ) $ 7,134 $ (3,982 ) $ 837 $ (3,145 ) Reclassification adjustment for gains on securities included in net income — — — (2,840 ) 596 (2,244 ) Total unrealized gains (losses) on securities 9,030 (1,896 ) 7,134 (6,822 ) 1,433 (5,389 ) Unrealized gains (losses) on derivatives: Unrealized holding gains (losses) on derivatives arising during the period 133 (28 ) 105 (130 ) 27 (103 ) Reclassification adjustment for losses on derivatives included in net income — — — — — — Total unrealized gains (losses) on derivatives 133 (28 ) 105 (130 ) 27 (103 ) Total other comprehensive income (loss) $ 9,163 $ (1,924 ) $ 7,239 $ (6,952 ) $ 1,460 $ (5,492 )
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table details the change in components of OCI for the three months ended March 31 : 2019 2018 Securities Available for Sale Post-Retirement Obligation Derivatives Accumulated Other Comprehensive Income (Loss) Securities Available for Sale Post-Retirement Obligation Derivatives Accumulated Other Comprehensive Income (Loss) (dollars in thousands) Balance at December 31 $ (11,697 ) $ 461 $ (105 ) $ (11,341 ) $ (6,166 ) $ 299 $ (306 ) $ (6,173 ) Cumulative effect of adoption of ASU 2018-02 — — — — (1,344 ) — — (1,344 ) Balance at January 1 (11,697 ) 461 (105 ) (11,341 ) (7,510 ) 299 (306 ) (7,517 ) Other comprehensive income (loss) before reclassification adjustment 7,134 — 105 7,239 (3,145 ) — (103 ) (3,248 ) Amounts reclassified from accumulated other comprehensive (loss) income — — — — (2,244 ) — — (2,244 ) Net other comprehensive income (loss) during the period 7,134 — 105 7,239 (5,389 ) — (103 ) (5,492 ) Balance at March 31 $ (4,563 ) $ 461 $ — $ (4,102 ) $ (12,899 ) $ 299 $ (409 ) $ (13,009 )

Supplemental Cash Flow Disclo_2

Supplemental Cash Flow Disclosures (Tables)	3 Months Ended
	Mar. 31, 2019
Supplemental Cash Flow Information [Abstract]
Schedule of Supplemental Cash Flow Disclosures	The following table presents information related to cash paid during the period for interest and income taxes, as well as detail on non-cash investing and financing activities for the three months ended March 31 : 2019 2018 (dollars in thousands) Cash paid during the period for: Interest $ 12,660 $ 7,072 Income taxes 61 28 Non-cash investing and financing activities: Loans transferred to other real estate owned and repossessed assets 982 1,186 Loans transferred from held to maturity to held for sale 4,156 8,019 Gross increase (decrease) in market value adjustment to securities available for sale 9,030 (6,822 ) Gross increase (decrease) in market value adjustment to derivatives 133 (131 ) Noncash treasury stock reissuance 2,531 2,257 Unsettled treasury stock repurchases 289 — Proceeds from death benefit on bank-owned life insurance not received — 2,306

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Composition of Weighted-Average Common Shares (Denominator) Used in Basic and Diluted Earnings Per Share	The following table summarizes the composition of the weighted-average common shares (denominator) used in the basic and diluted earnings per share computations: For the Three Months Ended March 31, 2019 2018 Weighted average common shares issued 113,914,902 113,914,902 Average treasury stock shares (15,291,253 ) (16,369,144 ) Average deferred compensation shares (37,411 ) (37,411 ) Average unearned nonvested shares (107,197 ) (75,210 ) Weighted average common shares and common stock equivalents used to calculate basic earnings per share 98,479,041 97,433,137 Additional common stock equivalents (nonvested stock) used to calculate diluted earnings per share 190,375 130,614 Additional common stock equivalents (deferred compensation) used to calculate diluted earnings per share 37,411 37,411 Weighted average common shares and common stock equivalents used to calculate diluted earnings per share 98,706,827 97,601,162 Basic Earnings per Share $ 0.25 $ 0.24 Diluted Earnings per Share $ 0.25 $ 0.24
Common Stock Equivalents Not Included in Computation of Diluted Earnings Per Share	The following table shows the number of shares and the price per share related to common stock equivalents that were not included in the computation of diluted earnings per share for the three months ended March 31 because to do so would have been antidilutive. 2019 2018 Price Range Price Range Shares From To Shares From To Restricted Stock 95,403 $ 12.99 $ 14.49 37,298 $ 9.84 $ 14.49 Restricted Stock Units 39,618 $ 14.22 $ 16.62 43,067 $ 13.25 $ 15.83

Commitments and Contingent Li_2

Commitments and Contingent Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Notional Amount of Outstanding Commitments	The following table identifies the notional amount of those instruments at: March 31, 2019 December 31, 2018 (dollars in thousands) Financial instruments whose contract amounts represent credit risk: Commitments to extend credit $ 1,881,445 $ 1,883,914 Financial standby letters of credit 18,121 18,298 Performance standby letters of credit 28,520 22,027 Commercial letters of credit 887 887

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Analysis of Amortized Cost and Estimated Fair Value of Securities Available for Sale	Below is an analysis of the amortized cost and estimated fair values of securities available for sale at: March 31, 2019 December 31, 2018 Amortized Gross Gross Estimated Amortized Gross Gross Estimated (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ 8,731 $ 539 $ (24 ) $ 9,246 $ 9,011 $ 479 $ (84 ) $ 9,406 Mortgage-Backed Securities – Commercial 169,153 457 (1,490 ) 168,120 169,633 214 (2,103 ) 167,744 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 660,080 2,749 (8,863 ) 653,966 686,906 1,846 (15,391 ) 673,361 Other Government-Sponsored Enterprises 10,000 6 — 10,006 10,000 12 — 10,012 Obligations of States and Political Subdivisions 28,010 204 — 28,214 27,592 126 (6 ) 27,712 Corporate Securities 22,903 665 (19 ) 23,549 20,912 321 (221 ) 21,012 Total Securities Available for Sale $ 898,877 $ 4,620 $ (10,396 ) $ 893,101 $ 924,054 $ 2,998 $ (17,805 ) $ 909,247
Amortized Cost and Estimated Fair Value of Debt Securities Available for Sale	The amortized cost and estimated fair value of debt securities available for sale at March 31, 2019 , by contractual maturity, are shown below. Amortized Estimated (dollars in thousands) Due within 1 year $ — $ — Due after 1 but within 5 years 27,333 27,588 Due after 5 but within 10 years 33,580 34,181 Due after 10 years — — 60,913 61,769 Mortgage-Backed Securities (a) 837,964 831,332 Total Debt Securities $ 898,877 $ 893,101 (a) Mortgage-Backed Securities include an amortized cost of $177.9 million and a fair value of $177.4 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $660.1 million and a fair value of $654.0 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac
Proceeds from Sale, Gross Gains (Losses) Realized on Sales, Maturities and Other-Than-Temporary Impairment Charges Related to Securities Available for Sale	Proceeds from sales, gross gains (losses) realized on sales, maturities and other-than-temporary impairment charges related to securities available for sale were as follows for the three months ended March 31 : 2019 2018 (dollars in thousands) Proceeds from sales $ — $ — Gross gains (losses) realized: Sales Transactions: Gross gains $ — $ — Gross losses — — — — Maturities and impairment Gross gains — 2,840 Gross losses — — — 2,840 Net gains and impairment $ — $ 2,840

Investment Securities Maturity

Investment Securities Maturity of Held-to-Maturity Securities (Tables)	3 Months Ended
	Mar. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity [Table Text Block]	Below is an analysis of the amortized cost and fair values of debt securities held to maturity at: March 31, 2019 December 31, 2018 Amortized Gross Gross Estimated Amortized Gross Gross Estimated (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ 3,606 $ — $ (26 ) $ 3,580 $ 3,635 $ — $ (97 ) $ 3,538 Mortgage-Backed Securities- Commercial 54,898 — (1,763 ) 53,135 55,221 — (2,327 ) 52,894 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 270,807 352 (3,303 ) 267,856 279,109 212 (7,254 ) 272,067 Mortgage-Backed Securities – Commercial 12,894 — (95 ) 12,799 13,159 — (258 ) 12,901 Obligations of States and Political Subdivisions 42,304 400 (31 ) 42,673 42,331 175 (313 ) 42,193 Debt Securities Issued by Foreign Governments 400 — — 400 400 — — 400 Total Securities Held to Maturity $ 384,909 $ 752 $ (5,218 ) $ 380,443 $ 393,855 $ 387 $ (10,249 ) $ 383,993
Schedule of Held-to-Maturity Securities by Maturity [Table Text Block]	The amortized cost and estimated fair value of debt securities held to maturity at March 31, 2019 , by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or repay obligations with or without call or prepayment penalties. Amortized Estimated (dollars in thousands) Due within 1 year $ 518 $ 518 Due after 1 but within 5 years 7,922 7,965 Due after 5 but within 10 years 34,264 34,590 Due after 10 years — — 42,704 43,073 Mortgage-Backed Securities (a) 342,205 337,370 Total Debt Securities $ 384,909 $ 380,443 (a) Mortgage-Backed Securities include an amortized cost of $58.5 million and a fair value of $56.7 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $283.7 million and a fair value of $280.7 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac.

Impairment of Investment Secu_2

Impairment of Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2019
Impairment of Investment Securities Disclosure [Abstract]
Schedule of Unrealized Losses and Estimated Fair Values	The following table presents the gross unrealized losses and estimated fair values at March 31, 2019 for both available for sale and held to maturity securities by investment category and time frame for which securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total Estimated Gross Estimated Gross Estimated Gross (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ — $ — $ 7,336 $ (50 ) $ 7,336 $ (50 ) Mortgage-Backed Securities – Commercial 48,274 (28 ) 124,003 (3,225 ) 172,277 (3,253 ) Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 4 — 710,446 (12,166 ) 710,450 (12,166 ) Mortgage-Backed Securities – Commercial — — 12,799 (95 ) 12,799 (95 ) Obligations of States and Political Subdivisions — — 5,925 (31 ) 5,925 (31 ) Debt Securities Issued by Foreign Governments 200 — — — 200 — Corporate Securities — — 4,976 (19 ) 4,976 (19 ) Total Securities $ 48,478 $ (28 ) $ 865,485 $ (15,586 ) $ 913,963 $ (15,614 ) The following table presents the gross unrealized losses and estimated fair values at December 31, 2018 by investment category and time frame for which securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total Estimated Gross Estimated Gross Estimated Gross (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities – Residential $ 2,289 $ (41 ) $ 5,028 $ (140 ) $ 7,317 $ (181 ) Mortgage-Backed Securities - Commercial 95,826 (925 ) 75,959 (3,505 ) 171,785 (4,430 ) Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities – Residential 156,732 (1,856 ) 626,003 (20,789 ) 782,735 (22,645 ) Mortgage-Backed Securities – Commercial — — 12,901 (258 ) 12,901 (258 ) Obligation of States and Political Subdivisions 8,591 (85 ) 9,338 (234 ) 17,929 (319 ) Corporate Securities 14,769 (214 ) 3,993 (7 ) 18,762 (221 ) Total Securities $ 278,207 $ (3,121 ) $ 733,222 $ (24,933 ) $ 1,011,429 $ (28,054 )
Cumulative Roll Forward of Credit Losses Recognized in Earnings for Debt Securities held and not Intended to be Sold	The following table provides a cumulative roll forward of credit losses recognized in earnings for the trust preferred securities: For the Three Months Ended March 31, 2019 2018 (dollars in thousands) Balance, beginning (a) $ — $ 12,208 Credit losses on debt securities for which other-than-temporary impairment was not previously recognized — — Additional credit losses on debt securities for which other-than-temporary impairment was previously recognized — — Increases in cash flows expected to be collected, recognized over the remaining life of the security (b) — (147 ) Reduction for debt securities sold during the period — — Reduction for debt securities called during the period — (2,302 ) Balance, ending $ — $ 9,759 (a) The beginning balance represents credit related losses included in other-than-temporary impairment charges recognized on debt securities in prior periods. (b) Represents the increase in cash flows recognized in interest income during the period.

Loans and Allowance for Credi_2

Loans and Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2019
Loans and Leases Receivable Disclosure [Abstract]
Outstanding Balances of Loan	The following table provides outstanding balances related to each of our loan types: March 31, 2019 December 31, 2018 Originated Acquired Total Originated Acquired Total (dollars in thousands) Commercial, financial, agricultural and other $ 1,143,885 $ 36,435 $ 1,180,320 $ 1,100,947 $ 37,526 $ 1,138,473 Real estate construction 383,164 6,223 389,387 353,008 5,970 358,978 Residential real estate 1,325,740 239,609 1,565,349 1,313,645 248,760 1,562,405 Commercial real estate 1,946,482 191,894 2,138,376 1,922,349 201,195 2,123,544 Loans to individuals 593,481 4,157 597,638 585,347 5,392 590,739 Total loans $ 5,392,752 $ 478,318 $ 5,871,070 $ 5,275,296 $ 498,843 $ 5,774,139
Credit Risk Profile by Creditworthiness	The following tables represent our credit risk profile by creditworthiness: March 31, 2019 Commercial, financial, agricultural and other Real estate construction Residential real estate Commercial real estate Loans to individuals Total (dollars in thousands) Originated loans Pass $ 1,107,013 $ 374,201 $ 1,315,339 $ 1,894,745 $ 593,253 $ 5,284,551 Non-Pass OAEM 31,225 8,963 809 32,635 — 73,632 Substandard 5,647 — 9,592 19,102 228 34,569 Doubtful — — — — — — Total Non-Pass 36,872 8,963 10,401 51,737 228 108,201 Total $ 1,143,885 $ 383,164 $ 1,325,740 $ 1,946,482 $ 593,481 $ 5,392,752 Acquired loans Pass $ 30,627 $ 5,602 $ 236,594 $ 189,052 $ 4,143 $ 466,018 Non-Pass OAEM 5,672 621 725 423 — 7,441 Substandard 136 — 2,290 2,419 14 4,859 Doubtful — — — — — — Total Non-Pass 5,808 621 3,015 2,842 14 12,300 Total $ 36,435 $ 6,223 $ 239,609 $ 191,894 $ 4,157 $ 478,318 December 31, 2018 Commercial, financial, agricultural and other Real estate construction Residential real estate Commercial real estate Loans to individuals Total (dollars in thousands) Originated loans Pass $ 1,055,394 $ 337,367 $ 1,302,912 $ 1,880,139 $ 585,141 $ 5,160,953 Non-Pass OAEM 33,723 15,641 1,026 28,904 — 79,294 Substandard 11,830 — 9,707 13,306 206 35,049 Doubtful — — — — — — Total Non-Pass 45,553 15,641 10,733 42,210 206 114,343 Total $ 1,100,947 $ 353,008 $ 1,313,645 $ 1,922,349 $ 585,347 $ 5,275,296 Acquired loans Pass $ 31,399 $ 5,337 $ 245,637 $ 198,201 $ 5,377 $ 485,951 Non-Pass OAEM 5,890 633 736 441 — 7,700 Substandard 237 — 2,387 2,553 15 5,192 Doubtful — — — — — — Total Non-Pass 6,127 633 3,123 2,994 15 12,892 Total $ 37,526 $ 5,970 $ 248,760 $ 201,195 $ 5,392 $ 498,843
Age Analysis of Past Due Loans by Segment	The following tables delineate the aging analysis of the recorded investments in past due loans as of March 31, 2019 and December 31, 2018 . Also included in these tables are loans that are 90 days or more past due and still accruing because they are well-secured and in the process of collection. March 31, 2019 30 - 59 60 - 89 90 days Nonaccrual Total past Current Total (dollars in thousands) Originated loans Commercial, financial, agricultural and other $ 207 $ 1,037 $ 83 $ 4,390 $ 5,717 $ 1,138,168 $ 1,143,885 Real estate construction 507 — — — 507 382,657 383,164 Residential real estate 2,995 1,739 460 6,126 11,320 1,314,420 1,325,740 Commercial real estate 1,161 122 — 8,539 9,822 1,936,660 1,946,482 Loans to individuals 2,406 481 759 228 3,874 589,607 593,481 Total $ 7,276 $ 3,379 $ 1,302 $ 19,283 $ 31,240 $ 5,361,512 $ 5,392,752 Acquired loans Commercial, financial, agricultural and other $ — $ — $ — $ 100 $ 100 $ 36,335 $ 36,435 Real estate construction — — — — — 6,223 6,223 Residential real estate 98 35 171 1,816 2,120 237,489 239,609 Commercial real estate 185 — — 947 1,132 190,762 191,894 Loans to individuals 22 7 36 14 79 4,078 4,157 Total $ 305 $ 42 $ 207 $ 2,877 $ 3,431 $ 474,887 $ 478,318 December 31, 2018 30 - 59 60 - 89 90 days Nonaccrual Total past Current Total (dollars in thousands) Originated loans Commercial, financial, agricultural and other $ 130 $ 247 $ 92 $ 10,223 $ 10,692 $ 1,090,255 $ 1,100,947 Real estate construction 212 — — — 212 352,796 353,008 Residential real estate 3,697 710 790 6,238 11,435 1,302,210 1,313,645 Commercial real estate 492 69 — 3,437 3,998 1,918,351 1,922,349 Loans to individuals 2,362 532 662 207 3,763 581,584 585,347 Total $ 6,893 $ 1,558 $ 1,544 $ 20,105 $ 30,100 $ 5,245,196 $ 5,275,296 Acquired loans Commercial, financial, agricultural and other $ 1 $ — $ — $ 204 $ 205 $ 37,321 $ 37,526 Real estate construction — — — — — 5,970 5,970 Residential real estate 226 24 27 1,904 2,181 246,579 248,760 Commercial real estate — — — 1,042 1,042 200,153 201,195 Loans to individuals 46 12 11 15 84 5,308 5,392 Total $ 273 $ 36 $ 38 $ 3,165 $ 3,512 $ 495,331 $ 498,843
Recorded Investment and Unpaid Principal Balance for Impaired Loans with Associated Allowance	The following tables include the recorded investment and unpaid principal balance for impaired loans with the associated allowance amount, if applicable, as of March 31, 2019 and December 31, 2018 . Also presented are the average recorded investment in impaired loans and the related amount of interest recognized while the loan was considered impaired. Average balances are calculated using month-end balances of the loans for the period reported and are included in the table below based on their period-end allowance position. March 31, 2019 December 31, 2018 Recorded Unpaid Related Recorded Unpaid Related (dollars in thousands) Originated loans: With no related allowance recorded: Commercial, financial, agricultural and other $ 2,599 $ 9,100 $ 8,735 $ 16,442 Real estate construction — — — — Residential real estate 10,545 12,264 10,726 12,571 Commercial real estate 3,752 4,042 3,599 3,812 Loans to individuals 339 530 281 408 Subtotal 17,235 25,936 23,341 33,233 With an allowance recorded: Commercial, financial, agricultural and other 3,317 3,479 $ 1,012 3,042 3,181 $ 797 Real estate construction — — — — — — Residential real estate 713 713 119 486 495 107 Commercial real estate 7,017 7,035 914 1,866 1,878 596 Loans to individuals — — — — — — Subtotal 11,047 11,227 2,045 5,394 5,554 1,500 Total $ 28,282 $ 37,163 $ 2,045 $ 28,735 $ 38,787 $ 1,500 March 31, 2019 December 31, 2018 Recorded Unpaid Related Recorded Unpaid Related (dollars in thousands) Acquired loans With no related allowance recorded: Commercial, financial, agricultural and other $ 100 $ 100 $ 73 $ 73 Real estate construction — — — — Residential real estate 1,937 2,369 2,031 2,604 Commercial real estate 947 1,962 1,042 2,052 Loans to individuals 14 16 15 17 Subtotal 2,998 4,447 3,161 4,746 With an allowance recorded: Commercial, financial, agricultural and other — — $ — 131 131 $ 131 Real estate construction — — — — — — Residential real estate — — — — — — Commercial real estate — — — — — — Loans to individuals — — — — — — Subtotal — — — 131 131 131 Total $ 2,998 $ 4,447 $ — $ 3,292 $ 4,877 $ 131 For the Three Months Ended March 31, 2019 2018 Originated Loans Acquired Loans Originated Loans Acquired Loans Average Interest Average Interest Average Interest Average Interest (dollars in thousands) With no related allowance recorded: Commercial, financial, agricultural and other $ 2,707 $ 13 $ 439 $ — $ 8,130 $ 10 $ 411 $ — Real estate construction — — — — — — — — Residential real estate 10,798 72 1,981 1 10,401 63 678 1 Commercial real estate 3,994 36 982 1 5,510 31 907 — Loans to individuals 324 1 14 — 354 2 17 — Subtotal 17,823 122 3,416 2 24,395 106 2,013 1 With an allowance recorded: Commercial, financial, agricultural and other 3,068 3 — — 17,720 66 — — Real estate construction — — — — — — — — Residential real estate 604 5 — — 706 — 93 — Commercial real estate 3,278 1 — — 1,960 1 118 — Loans to individuals — — — — — — — — Subtotal 6,950 9 — — 20,386 67 211 — Total $ 24,773 $ 131 $ 3,416 $ 2 $ 44,781 $ 173 $ 2,224 $ 1
Troubled Debt Restructured Loans and Commitments	The following tables provide detail, including specific reserves and reasons for modification, related to loans identified as troubled debt restructurings: For the Three Months Ended March 31, 2019 Type of Modification Number Extend Modify Modify Total Post- Specific (dollars in thousands) Commercial, financial, agricultural and other 1 $ — $ — $ 61 $ 61 $ 62 $ — Residential real estate 6 17 49 514 580 570 40 Commercial real estate 2 — 556 242 798 767 — Loans to individuals 3 — — 48 48 46 — Total 12 $ 17 $ 605 $ 865 $ 1,487 $ 1,445 $ 40 For the Three Months Ended March 31, 2018 Type of Modification Number Extend Modify Modify Total Post- Specific (dollars in thousands) Commercial, financial, agricultural and other 2 $ 4,709 $ — $ 162 $ 4,871 $ 3,942 $ 531 Residential real estate 11 20 75 346 441 404 17 Commercial real estate 1 3,017 — — 3,017 2,994 227 Loans to individuals 4 — 28 30 58 53 — Total 18 $ 7,746 $ 103 $ 538 $ 8,387 $ 7,393 $ 775 The troubled debt restructurings included in the above tables are also included in the impaired loan tables provided earlier in this note. Loans defined as modified due to a change in rate may include loans that were modified for a change in rate as well as a re-amortization of the principal and an extension of the maturity. For the three months ended March 31, 2019 and 2018 , $0.6 million and $0.1 million , respectively, of total rate modifications represent loans with modifications to the rate as well as payment as a result of re-amortization. For both 2019 and 2018 the changes in loan balances between the pre-modification balance and the post-modification balance are due to customer payments. The following table provides detail as to the total troubled debt restructured loans and total commitments outstanding on troubled debt restructured loans: March 31, 2019 December 31, 2018 (dollars in thousands) Troubled debt restructured loans Accrual status $ 9,120 $ 8,757 Nonaccrual status 5,874 11,761 Total $ 14,994 $ 20,518 Commitments Letters of credit $ 60 $ 60 Unused lines of credit 263 1,027 Total $ 323 $ 1,087
Troubled Debt Restructuring Subsequent Default [Table Text Block]	A troubled debt restructuring is considered to be in default when a restructured loan is 90 days or more past due. The following table provides information related to loans that were restructured within the past twelve months and that were considered to be in default during the three months ended March 31 : 2019 2018 Number of Recorded Number of Recorded (dollars in thousands) Commercial, financial, agricultural and other — $ — 1 $ 940 Loans to individuals 1 10 — — Total 1 $ 10 1 $ 940
Allowance for Credit Losses	he following tables provide detail related to the allowance for credit losses: For the Three Months Ended March 31, 2019 Commercial, Real estate Residential Commercial Loans to Total (dollars in thousands) Allowance for credit losses: Originated loans: Beginning balance $ 19,235 $ 2,002 $ 3,934 $ 18,382 $ 4,033 $ 47,586 Charge-offs (483 ) — (136 ) (299 ) (1,110 ) (2,028 ) Recoveries 76 42 81 41 114 354 Provision (credit) 987 210 271 1,094 1,126 3,688 Ending balance 19,815 2,254 4,150 19,218 4,163 49,600 Acquired loans: Beginning balance 139 — 35 4 — 178 Charge-offs (526 ) — (45 ) — (5 ) (576 ) Recoveries 11 — 24 — 9 44 Provision (credit) 394 — 21 (4 ) (4 ) 407 Ending balance 18 — 35 — — 53 Total ending balance $ 19,833 $ 2,254 $ 4,185 $ 19,218 $ 4,163 $ 49,653 Ending balance: individually evaluated for impairment $ 1,012 $ — $ 119 $ 914 $ — $ 2,045 Ending balance: collectively evaluated for impairment 18,821 2,254 4,066 18,304 4,163 47,608 Loans: Ending balance 1,180,320 389,387 1,565,349 2,138,376 597,638 5,871,070 Ending balance: individually evaluated for impairment 5,627 — 3,938 11,111 — 20,676 Ending balance: collectively evaluated for impairment 1,174,693 389,387 1,561,411 2,127,265 597,638 5,850,394 For the Three Months Ended March 31, 2018 Commercial, Real estate Residential Commercial Loans to Total (dollars in thousands) Allowance for credit losses: Originated loans: Beginning balance $ 23,418 $ 1,349 $ 2,753 $ 17,328 $ 3,404 $ 48,252 Charge-offs (290 ) — (455 ) (168 ) (1,169 ) (2,082 ) Recoveries 256 1 75 69 195 596 Provision (credit) 4,148 (236 ) 768 1,265 986 6,931 Ending balance 27,532 1,114 3,141 18,494 3,416 53,697 Acquired loans: Beginning balance 11 — 6 29 — 46 Charge-offs — — (16 ) — (4 ) (20 ) Recoveries 7 6 17 — 7 37 Provision (credit) 2 (6 ) 6 (27 ) (3 ) (28 ) Ending balance 20 — 13 2 — 35 Total ending balance $ 27,552 $ 1,114 $ 3,154 $ 18,496 $ 3,416 $ 53,732 Ending balance: individually evaluated for impairment $ 9,045 $ — $ 287 $ 2,141 $ — $ 11,473 Ending balance: collectively evaluated for impairment 18,507 1,114 2,867 16,355 3,416 42,259 Loans: Ending balance 1,131,594 246,961 1,434,623 2,027,072 541,055 5,381,305 Ending balance: individually evaluated for impairment 33,278 — 6,853 10,360 — 50,491 Ending balance: collectively evaluated for impairment 1,098,316 246,961 1,427,770 2,016,712 541,055 5,330,814

Leases Lease Liability Maturity

Leases Lease Liability Maturity (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Future minimum payments for operating leases with initial or remaining terms of one year or more as of March 31, 2019 were as follows (dollars in thousands): For the twelve months ended: March 31, 2020 $ 4,499 March 31, 2021 4,517 March 31, 2022 4,480 March 31, 2023 4,413 March 31, 2024 4,370 Thereafter 46,528 Total future minimum lease payments 68,807 Less remaining imputed interest 17,436 Present value of future minimum lease payments $ 51,371

Leases Lease Assets and Liabili

Leases Lease Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lessee, Operating Leases [Text Block]	The following table represents the Consolidated Statements of Condition classification of the Company’s ROU assets and lease liabilities, lease costs and other lease information as of and for the three months ended March 31, 2019 (dollars in thousands). Balance sheet: Operating lease asset classified as premises and equipment $ 47,566 Operating lease liability classified as other liabilities 51,371 Income statement: Operating lease cost classified as occupancy and equipment expense $ 1,337 Weighted average lease term, in years 16.28 Weighted average discount rate 3.49 % Operating cash flows $ 1,119

Fair Values of Assets and Lia_2

Fair Values of Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Inputs, Assets, Quantitative Information	In accordance with ASU No. 2011 -4 , the following table provides information related to quantitative inputs and assumptions used in March 31, 2019 Level 3 fair value measurements. Fair Value (dollars Valuation Unobservable Inputs Range / Other Investments $ 1,670 CarryingValue N/A N/A Impaired Loans 1,044 (a) Reserve study Discount rate 10.00% Gas per MMBTU $2.61 - $3.49 (b) Oil per BBL/d $47.09 - $53.14 (b) 3,187 (a) Discounted Cash Flow Discount Rate 1.9% - 9.5% Limited Partnership Investments 3,200 Par Value N/A N/A (a) The remainder of impaired loans valued using Level 3 inputs are not included in this disclosure as the values of those loans are based on bankruptcy agreement documentation. (b) Unobservable inputs are defined as follows: MMBTU - million British thermal units; BBL/d - barrels per day.
Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis	The tables below present the balances of assets and liabilities measured at fair value on a recurring basis: March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities - Residential $ — $ 9,246 $ — $ 9,246 Mortgage-Backed Securities - Commercial — 168,120 — 168,120 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities - Residential — 653,966 — 653,966 Other Government-Sponsored Enterprises — 10,006 — 10,006 Obligations of States and Political Subdivisions — 28,214 — 28,214 Corporate Securities — 23,549 — 23,549 Total Securities Available for Sale — 893,101 — 893,101 Other Investments — 23,708 1,670 25,378 Loans Held for Sale — 9,627 — 9,627 Other Assets(a) — 7,613 3,200 10,813 Total Assets $ — $ 934,049 $ 4,870 $ 938,919 Other Liabilities(a) $ — $ 7,868 $ — $ 7,868 Total Liabilities $ — $ 7,868 $ — $ 7,868 (a) Hedging and non-hedging interest rate derivatives and limited partnership investments December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Obligations of U.S. Government Agencies: Mortgage-Backed Securities - Residential $ — $ 9,406 $ — $ 9,406 Mortgage-Backed Securities - Commercial — 167,744 — 167,744 Obligations of U.S. Government-Sponsored Enterprises: Mortgage-Backed Securities - Residential — 673,361 — 673,361 Other Government-Sponsored Enterprises — 10,012 — 10,012 Obligations of States and Political Subdivisions — 27,712 — 27,712 Corporate Securities — 21,012 — 21,012 Total Securities Available for Sale — 909,247 — 909,247 Other Investments — 30,456 1,670 32,126 Loans Held for Sale — 11,881 — 11,881 Other Assets(a) — 1,769 2,696 4,465 Total Assets $ — $ 953,353 $ 4,366 $ 957,719 Other Liabilities(a) $ — $ 2,081 $ — $ 2,081 Total Liabilities $ — $ 2,081 $ — $ 2,081 (a) Hedging and non-hedging interest rate derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	For the three months ended March 31 , changes in Level 3 assets and liabilities measured at fair value on a recurring basis are summarized as follows: 2019 Other Investments Other Total (dollars in thousands) Balance, beginning of period $ 1,670 $ 2,696 $ 4,366 Total gains or losses Included in earnings — — — Included in other comprehensive income — (47 ) (47 ) Purchases, issuances, sales and settlements Purchases — 551 551 Issuances — — — Sales — — — Settlements — — — Transfers from Level 3 — — — Transfers into Level 3 — — — Balance, end of period $ 1,670 $ 3,200 $ 4,870 2018 Pooled Trust Preferred Collateralized Debt Obligations Other Investments Other Total (dollars in thousands) Balance, beginning of period $ 23,646 $ 1,670 $ 2,143 $ 27,459 Total gains or losses Included in earnings 2,840 — — 2,840 Included in other comprehensive income 4,529 — — 4,529 Purchases, issuances, sales and settlements Purchases — — 149 149 Issuances — — — — Sales — — — — Settlements (16,883 ) — — (16,883 ) Transfers from Level 3 — — — — Transfers into Level 3 — — — — Balance, end of period $ 14,132 $ 1,670 $ 2,292 $ 18,094 During the three months ended March 31, 2019 and 2018 , there were no transfers between fair value Levels 1 , 2 or 3. There were no gains or losses included in earnings for the periods presented that are attributable to the change in realized gains (losses) relating to assets held at March 31, 2019 and 2018 .
Schedule of Assets Measured on Non-Recurring Basis	The tables below present the balances of assets measured at fair value on a nonrecurring basis at: March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Impaired loans $ — $ 14,391 $ 14,849 $ 29,240 Other real estate owned — 4,300 — 4,300 Total Assets $ — $ 18,691 $ 14,849 $ 33,540 December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Impaired loans $ — $ 15,076 $ 15,320 $ 30,396 Other real estate owned — 4,035 — 4,035 Total Assets $ — $ 19,111 $ 15,320 $ 34,431
Losses Realized on Assets Measured on Non-Recurring Basis	The following gains(losses) were realized on the assets measured on a nonrecurring basis: For the Three Months Ended March 31, 2019 2018 (dollars in thousands) Impaired loans $ (969 ) $ (7,850 ) Other real estate owned (49 ) (30 ) Total losses $ (1,018 ) $ (7,880 )
Carrying Amounts and Fair Values of Financial Instruments	The following table presents carrying amounts and fair values of First Commonwealth’s financial instruments: March 31, 2019 Fair Value Measurements Using: Carrying Total Level 1 Level 2 Level 3 (dollars in thousands) Financial assets Cash and due from banks $ 100,724 $ 100,724 $ 100,724 $ — $ — Interest-bearing deposits 23,168 23,168 23,168 — — Securities available for sale 893,101 893,101 — 893,101 — Securities held to maturity 384,909 380,443 — 380,443 — Other investments 25,378 25,378 — 23,708 1,670 Loans held for sale 9,627 9,627 — 9,627 — Loans 5,871,070 5,921,319 — 14,391 5,906,928 Financial liabilities Deposits 6,130,760 6,135,980 — 6,135,980 — Short-term borrowings 565,616 565,522 — 565,522 — Subordinated debt 170,328 169,764 — — 169,764 Long-term debt 7,395 7,701 — 7,701 — Capital lease obligation 7,118 7,118 — 7,118 — December 31, 2018 Fair Value Measurements Using: Carrying Total Level 1 Level 2 Level 3 (dollars in thousands) Financial assets Cash and due from banks $ 95,934 $ 95,934 $ 95,934 $ — $ — Interest-bearing deposits 3,013 3,013 3,013 — — Securities available for sale 909,247 909,247 — 909,247 — Securities held to maturity 393,855 383,993 — 383,993 — Other investments 32,126 32,126 — 30,456 1,670 Loans held for sale 11,881 11,881 — 11,881 — Loans 5,774,139 5,821,791 — 15,076 5,806,715 Financial liabilities Deposits 5,897,992 5,904,147 — 5,904,147 — Short-term borrowings 721,823 721,532 — 721,532 — Subordinated debt 170,288 168,067 — — 168,067 Long-term debt 7,551 7,720 — 7,720 — Capital lease obligation 7,217 7,217 — 7,217 —

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Credit Value Adjustment Recorded Related to Notional Amount Of Derivatives Outstanding	The following table depicts the credit value adjustment recorded related to the notional amount of derivatives outstanding as well as the notional amount of risk participation agreements participated to other banks: March 31, 2019 December 31, 2018 (dollars in thousands) Derivatives not Designated as Hedging Instruments Credit value adjustment $ (29 ) $ (3 ) Notional amount: Interest rate derivatives 370,693 411,645 Interest rate caps 36,028 36,111 Interest rate collars 35,354 — Risk participation agreements 170,016 162,139 Sold credit protection on risk participation agreements (46,871 ) (59,315 ) Interest rate options 25,215 9,900 Derivatives Designated as Hedging Instruments Interest rate swaps: Fair value adjustment — (133 ) Notional amount — 65,000 Interest rate forwards: Fair value adjustment (234 ) (170 ) Notional amount 30,000 15,000 Foreign exchange forwards: Fair value adjustment 7 (6 ) Notional amount 1,797 1,927
Schedule of Changes in Fair Value of Derivative Assets and Liabilities	The table below presents the amount representing the change in the fair value of derivative assets and derivative liabilities attributable to credit risk included in "Other income" on the Consolidated Statements of Income: For the Three Months Ended March 31, 2019 2018 (dollars in thousands) Non-hedging interest rate derivatives (Decrease) increase in other income $ (470 ) $ 789 Hedging interest rate derivatives Decrease in interest and fees on loans (118 ) (81 ) Increase in other expense 7 — Hedging interest rate forwards Decrease in other income (64 ) — Decrease in other expense — (62 ) Hedging foreign exchange forwards Increase (decrease) in other expense 2 (3 )

Subordinated Debentures Subor_2

Subordinated Debentures Subordinated Debentures Outstanding (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue Recognition and Deferred Revenue [Abstract]
Schedule of Subordinated Borrowing [Table Text Block]	Subordinated debentures outstanding are as follows: March 31, 2019 December 31, 2018 Due Amount Rate Amount Rate (dollars in thousands) Owed to: First Commonwealth Bank 2028 $ 49,152 4.875% until June 1, 2023, then LIBOR + 1.845% $ 49,131 4.875% until June 1, 2023, then LIBOR + 1.845% First Commonwealth Bank 2033 $ 49,009 5.50% until June 1, 2028, then LIBOR + 2.37% $ 48,990 5.50% until June 1, 2028, then LIBOR + 2.37% First Commonwealth Capital Trust II 2034 $ 30,929 LIBOR + 2.85% $ 30,929 LIBOR + 2.85% First Commonwealth Capital Trust III 2034 41,238 LIBOR + 2.85% 41,238 LIBOR + 2.85% Total $ 170,328 $ 170,288

Revenue Recognition Revenue Rec

Revenue Recognition Revenue Recogntion (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue Recognition [Abstract]
Revenue Recognition, Transition Adjustment [Table Text Block]
Revenue Recognition and Deferred Revenue [Abstract]
Deferred Revenue, by Arrangement, Disclosure [Table Text Block]	The following presents noninterest income, segregated by revenue streams in-scope and out-of-scope of Topic 606: For the Three Months Ended March 31, 2019 2018 (dollars in thousands) Noninterest Income In-scope of Topic 606: Trust income $ 1,926 $ 1,928 Service charges on deposit accounts 4,245 4,406 Insurance and retail brokerage commissions 1,961 1,868 Card-related interchange income 4,730 4,742 Gain on sale of other loans and assets 258 207 Other income 862 892 Noninterest Income (in-scope of Topic 606) 13,982 14,043 Noninterest Income (out-of-scope of Topic 606) 4,890 8,000 Total Noninterest Income $ 18,872 $ 22,043

Basis of Presentation Additiona

Basis of Presentation Additional Information (Details) $ in Thousands	Dec. 31, 2017USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 0

Supplemental Comprehensive In_3

Supplemental Comprehensive Income Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Comprehensive Income Disclosures [Abstract]
Unrealized holding gains on securities arising during the period	$ 9,030	$ (3,982)
Reclassification adjustment for gains on securities included in net income	0	(2,840)
Total unrealized gains on securities	9,030	(6,822)
Unrealized holding gains (losses) on derivatives arising during the period	133	(130)
Unrealized holding gains on securities arising during the period	(1,896)	837
Reclassification adjustment for gains on derivatives included in net income, before Tax	0	0
Total unrealized gain on derivatives	133	(130)
Reclassification adjustment for gains on securities included in net income	0	596
Total other comprehensive (loss) income	9,163	(6,952)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax	(1,896)	1,433
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(28)	27
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax, Total	(28)	27
Other Comprehensive Income (Loss), Tax	(1,924)	1,460
Other comprehensive income (loss) before reclassification adjustment	7,134	(3,145)
Total unrealized (losses) gains on securities	7,134	(5,389)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	105	(103)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Total	105	(103)
Total other comprehensive (loss) income	7,239	(5,492)
Reclassification adjustment for gains on securities included in net income	$ 0	$ 2,244

Supplemental Comprehensive In_4

Supplemental Comprehensive Income Disclosures (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (11,341)
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 0
Other comprehensive income (loss) before reclassification adjustment	7,134	$ (3,145)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	105	(103)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0
Total other comprehensive (loss) income	7,239	(5,492)
Accumulated Other Comprehensive Income (Loss), Ending Balance	(4,102)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(11,697)	(7,510)
Cumulative Effect of New Accounting Principle in Period of Adoption				(1,344)
Other comprehensive income (loss) before reclassification adjustment	7,134	(3,145)
Amounts reclassified from accumulated other comprehensive income (loss)	0	(2,244)
Total other comprehensive (loss) income	7,134	(5,389)
Accumulated Other Comprehensive Income (Loss), Ending Balance	(4,563)	(12,899)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	461	299
Cumulative Effect of New Accounting Principle in Period of Adoption				0
Other comprehensive income (loss) before reclassification adjustment	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Total other comprehensive (loss) income	0	0
Accumulated Other Comprehensive Income (Loss), Ending Balance	461	299
Derivative [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(105)	(306)
Cumulative Effect of New Accounting Principle in Period of Adoption				0
Total other comprehensive (loss) income	105	(103)
Accumulated Other Comprehensive Income (Loss), Ending Balance	0	(409)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(11,341)	(7,517)
Cumulative Effect of New Accounting Principle in Period of Adoption				$ (1,344)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	7,239	(3,248)
Amounts reclassified from accumulated other comprehensive income (loss)	0	(2,244)
Total other comprehensive (loss) income	7,239	(5,492)
Accumulated Other Comprehensive Income (Loss), Ending Balance	(4,102)	(13,009)
Previously Reported [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(11,697)	(6,166)
Previously Reported [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	461	299
Previously Reported [Member] | Derivative [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(105)	(306)
Previously Reported [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (11,341)	$ (6,173)
Effect of ASU Adoption [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 0
Effect of ASU Adoption [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			0
Effect of ASU Adoption [Member] | Derivative [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			0
Effect of ASU Adoption [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 0

Supplemental Cash Flow Disclo_3

Supplemental Cash Flow Disclosures - Non-cash Investing and Financing Activities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash paid during the period for:
Interest	$ 12,660	$ 7,072
Income Taxes Paid, Net	61	28
Non-cash investing and financing activities:
Loans Transferred to Other Real Estate Owned and Repossessions	982	1,186
Fair value of loans transferred from held to maturity to held for sale	4,156	8,019
Gross increase (decrease) in market value adjustment to securities available for sale	9,030	(6,822)
Gross increase (decrease) in market value adjustment to derivatives	133	(131)
Stock Issued During Period, Value, Treasury Stock Reissued	2,531	2,257
Unsettled treasury stock repurchases	289	0
Unsettled Bank Owned Life Insurance Proceeds	$ 0	$ 2,306

Earnings per Share - Compositio

Earnings per Share - Composition of Weighted-Average Common Shares (Denominator) Used in Basic and Diluted Earnings Per Share (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Weighted Average Number of Shares Issued, Basic	113,914,902	113,914,902
Average treasury shares (in shares)	(15,291,253)	(16,369,144)
Weighted Average Number of Shares, Deferred Compensation Plans	(37,411)	(37,411)
Average unearned nonvested shares	(107,197)	(75,210)
Weighted average common shares and common stock equivalents used to calculate basic earnings per share (in shares)	98,479,041	97,433,137
Additional common stock equivalents (nonvested stock) used to calculate diluted earnings per share	190,375	130,614
Weighted Average Number Of Additional Shares Deferred Compensation Plan	37,411	37,411
Weighted average common shares and common stock equivalents used to calculate diluted earnings per share (in shares)	98,706,827	97,601,162
Basic Earnings per Share (in dollars per share)	$ 0.25	$ 0.24
Diluted Earnings per Share (in dollars per share)	$ 0.25	$ 0.24

Earnings per Share - Common Sto

Earnings per Share - Common Stock Equivalents Not Included in Computation of Diluted Earnings Per Share (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	95,403	37,298
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	39,618	43,067
Minimum [Member] | Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	$ 12.99	$ 9.84
Minimum [Member] | Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	14.22	13.25
Maximum [Member] | Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	14.49	14.49
Maximum [Member] | Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	$ 16.62	$ 15.83

Commitments and Contingent Li_3

Commitments and Contingent Liabilities - Notional Amount of Outstanding Commitments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments to extend credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	$ 1,881,445	$ 1,883,914
Financial standby letters of credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	18,121	18,298
Performance standby letters of credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	28,520	22,027
Commercial letters of credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	$ 887	$ 887

Commitments and Contingent Li_4

Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Notional Amount Of Performance Standby Letters Of Credit	$ 8,100,000
Notional Amount Of Commercial Letters Of Credit	0
Notional Amount Of Financial Standby Letters Of Credit	0
Financial instrument of credit risk	300,000	$ 200,000
Unfunded commitment liability	4,600,000	$ 5,000,000
Minimum [Member]
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	0
Maximum [Member]
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	$ 1,000,000

Investment Securities - Analysi

Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Investment Securities [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost		$ 0
Amortized Cost		898,877	$ 924,054
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		4,620	2,998
Gross Unrealized Losses		(10,396)	(17,805)
Securities available for sale, at fair value		893,101	909,247
Due within one year, Estimated Fair Value		0
Due after one but within five years, Amortized Cost		27,333
Due after one but within five years, Estimated Fair Value		27,588
Due after five but within ten years, Amortized Cost		33,580
Due after five but within ten years, Estimated Fair Value		34,181
Due after ten years, Amortized Cost		0
Due after ten years, Estimated Fair Value		0
Due within one year, Amortized Cost		60,913
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value		61,769
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	[1]	837,964
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	[1]	831,332
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost		177,900
Securities available for sale, at fair value		177,400
Residential Mortgage Backed Securities [Member]
Investment Securities [Line Items]
Securities available for sale, at fair value		653,966	673,361
Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Investment Securities [Line Items]
Securities available for sale, at fair value		10,006	10,012
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Securities available for sale, at fair value		28,214	27,712
Corporate Debt Securities [Member]
Investment Securities [Line Items]
Securities available for sale, at fair value		23,549	21,012
Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost		898,877
Securities available for sale, at fair value		893,101
US Government Agency Debt Securities Commercial [Domain]
Investment Securities [Line Items]
Amortized Cost		169,153	169,633
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		457	214
Gross Unrealized Losses		(1,490)	(2,103)
Securities available for sale, at fair value		168,120	167,744
Corporate Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost		22,903	20,912
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		665	321
Gross Unrealized Losses		(19)	(221)
Securities available for sale, at fair value		23,549	21,012
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Amortized Cost		28,010	27,592
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		204	126
Gross Unrealized Losses		0	(6)
Securities available for sale, at fair value		28,214	27,712
Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Investment Securities [Line Items]
Amortized Cost		10,000	10,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		6	12
Gross Unrealized Losses		0	0
Securities available for sale, at fair value		10,006	10,012
Residential Mortgage Backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost		660,080	686,906
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		2,749	1,846
Gross Unrealized Losses		(8,863)	(15,391)
Securities available for sale, at fair value		653,966	673,361
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost		8,731	9,011
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		539	479
Gross Unrealized Losses		(24)	(84)
Securities available for sale, at fair value		$ 9,246	$ 9,406
[1]	Mortgage-Backed Securities include an amortized cost of $177.9 million and a fair value of $177.4 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $660.1 million and a fair value of $654.0 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac.

Investment Securities - Amortiz

Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities Available for Sale (Detail) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Net Investment Income [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value		$ 61,769
Due after five but within ten years, Amortized Cost		33,580
Due after one but within five years, Amortized Cost		27,333
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	[1]	837,964
Due within one year, Amortized Cost		60,913
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost		0
Due after ten years, Amortized Cost		0
Corporate/Mortgage-Backed Securities, Amortized cost	[1]	831,332
Amortized Cost		898,877	$ 924,054
Due within one year, Estimated Fair Value		0
Due after one but within five years, Estimated Fair Value		27,588
Due after five but within ten years, Estimated Fair Value		34,181
Due after ten years, Estimated Fair Value		0
Securities available for sale, at fair value		893,101	909,247
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		4,620	2,998
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		10,396	17,805
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Net Investment Income [Line Items]
Amortized Cost		660,100
Securities available for sale, at fair value		654,000
Debt Securities [Member]
Net Investment Income [Line Items]
Amortized Cost		898,877
Securities available for sale, at fair value		893,101
Corporate Debt Securities [Member]
Net Investment Income [Line Items]
Securities available for sale, at fair value		23,549	21,012
Obligations of States and Political Subdivisions [Member]
Net Investment Income [Line Items]
Securities available for sale, at fair value		28,214	27,712
Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Net Investment Income [Line Items]
Securities available for sale, at fair value		10,006	10,012
Residential Mortgage Backed Securities [Member]
Net Investment Income [Line Items]
Securities available for sale, at fair value		653,966	$ 673,361
US Government Agencies Debt Securities [Member]
Net Investment Income [Line Items]
Amortized Cost		177,900
Securities available for sale, at fair value		$ 177,400
[1]	Mortgage-Backed Securities include an amortized cost of $177.9 million and a fair value of $177.4 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $660.1 million and a fair value of $654.0 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac.

Investment Securities - Amort_2

Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities Available for Sale (Detail) (1) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investment Securities [Line Items]
Amortized Cost	$ 898,877	$ 924,054
Securities available for sale, at fair value	893,101	909,247
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4,620	2,998
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	10,396	17,805
Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Investment Securities [Line Items]
Amortized Cost	10,000	10,000
Securities available for sale, at fair value	10,006	10,012
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	6	12
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	$ 0
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	177,900
Securities available for sale, at fair value	177,400
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Securities [Line Items]
Amortized Cost	660,100
Securities available for sale, at fair value	654,000
Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	898,877
Securities available for sale, at fair value	$ 893,101

Investment Securities - Proceed

Investment Securities - Proceeds from Sale, Gross Gains (Losses) Realized on Sales, Maturities and Other-Than-Temporary Impairment Charges Related to Securities Available for Sale (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Proceeds from Sale of Available-for-sale Securities	$ 0	$ 0
Sales Transactions:
Available-for-sale Securities, Gross Realized Gains	0	0
Gross losses	0	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	0	0
Maturities and impairment
Gross Gains	0	2,840
Gross Losses	0	0
Gain Losses Maturities And Impairment	0	2,840
Net gains and impairment	$ 0	$ 2,840

Investment Securities - Additio

Investment Securities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Gross Realized Gains	$ 0	$ 0
Gross Losses	0	0
Gross Gains	0	2,840
Debt Securities, Held-to-maturity, Restricted	324,700		$ 250,300
Proceeds from Sale of Available-for-sale Securities	0	$ 0
Debt Securities, Available-for-sale, Restricted	$ 625,200		$ 636,300

Investment Securities Schedule

Investment Securities Schedule of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Due within 1 year	$ 518
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	518
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	752	$ 387
Debt Securities, Held-to-maturity	384,909	393,855
Securities held to maturity, fair value	380,443	$ 383,993
Due after 1 but within 5 years	7,922
Due after 5 but within 10 years	34,264
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	34,590
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	7,965
Due after 10 years	0
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	0
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	42,704
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	43,073
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Amortized Cost	342,205
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value	337,370
US Government Agencies Residential Mortgage-backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	58,500
Securities held to maturity, fair value	56,700
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	283,700
Securities held to maturity, fair value	$ 280,700

Investment Securities Held to M

Investment Securities Held to Maturity Securities by Type (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 384,909	$ 393,855
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	752	387
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(5,218)	(10,249)
Securities held to maturity, fair value	380,443	383,993
US Government Agencies Residential Mortgage-backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	3,606	3,635
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(26)	(97)
Securities held to maturity, fair value	3,580	3,538
US Government Agency Debt Securities Commercial [Domain]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	54,898	55,221
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(1,763)	(2,327)
Securities held to maturity, fair value	53,135	52,894
Residential Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	270,807	279,109
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	352	212
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(3,303)	(7,254)
Securities held to maturity, fair value	267,856	272,067
Obligations of U.S. Government-Sponsored Enterprises - Mortgage-Backed Securities - Commercial [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	12,894	13,159
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(95)	(258)
Securities held to maturity, fair value	12,799	12,901
Obligations of States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	42,304	42,331
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	400	175
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(31)	(313)
Securities held to maturity, fair value	42,673	42,193
Debt Security, Government, Non-US [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	400	400
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Securities held to maturity, fair value	$ 400	$ 400

Other Investments - Additional

Other Investments - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Other Investments Disclosure [Abstract]
Other investments	$ 23.7	$ 30.5

Impairment of Investment Secu_3

Impairment of Investment Securities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Other than temporary impairment charges recognized	$ 0	$ 0
Amortized Cost	898,877,000		$ 924,054,000
Securities available for sale, at fair value	893,101,000		909,247,000
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	15,614,000		28,054,000
Federal Home Loan Bank Stock	$ 23,700,000		30,500,000
Other Investments and Securities, at Cost			1,700,000
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total	98
Corporate Debt Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Securities available for sale, at fair value	$ 23,549,000		21,012,000
Equity Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Other than temporary impairment charges recognized	$ 0	$ 0
Continuous Unrealized Loss Position, Fair Value			$ 0
US Government-sponsored Enterprises Debt Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Percent of Unrealized Losses	79.00%

Impairment of Investment Secu_4

Impairment of Investment Securities - Schedule of Unrealized Losses and Estimated Fair Values (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 48,478	$ 278,207
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(28)	(3,121)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	865,485	733,222
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(15,586)	(24,933)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	913,963	1,011,429
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	(15,614)	(28,054)
US Government Agencies Residential Mortgage-backed Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	2,289
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(41)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	7,336	5,028
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(50)	(140)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	7,336	7,317
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	(50)	(181)
US Government Agency Debt Securities Commercial [Domain]
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	48,274	95,826
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(28)	(925)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	124,003	75,959
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3,225)	(3,505)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	172,277	171,785
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,253)	(4,430)
Residential Mortgage Backed Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	4	156,732
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(1,856)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	710,446	626,003
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(12,166)	(20,789)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	710,450	782,735
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	(12,166)	(22,645)
Obligations of U.S. Government-Sponsored Enterprises - Mortgage-Backed Securities - Commercial [Member]
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	12,799	12,901
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(95)	(258)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	12,799	12,901
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	(95)	(258)
Obligations of States and Political Subdivisions [Member]
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	8,591
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(85)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5,925	9,338
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(31)	(234)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	5,925	17,929
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	(31)	(319)
Debt Security, Government, Non-US [Member]
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	200
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	200
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	0
Corporate Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	14,769
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(214)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,976	3,993
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(19)	(7)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total	4,976	18,762
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (19)	$ (221)

Impairment of Investment Secu_5

Impairment of Investment Securities - Cumulative Roll Forward of Credit Losses Recognized in Earnings for Debt Securities Held and Not Intended to be Sold (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Impairment of Investment Securities Disclosure [Abstract]
Balance, beginning (a)	[1]	$ 0	$ 12,208
Credit losses on debt securities for which other-than-temporary impairment was not previously recognized		0	0
Additional credit losses on debt securities for which other-than-temporary impairment was previously recognized		0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Period Increase (Decrease)		0	147
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold		0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Cash Flows		0	(2,302)
Balance, ending		$ 0	$ 9,759
[1]	The beginning balance represents credit related losses included in other-than-temporary impairment charges recognized on debt securities in prior periods.

Loans and Allowance for Credi_3

Loans and Allowance for Credit Losses - Outstanding Balances of Loan (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 5,871,070	$ 5,774,139	$ 5,381,305
Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		1,138,473
Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		358,978
Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		1,562,405
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		2,123,544
Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		590,739
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,392,752	5,275,296
Originated Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,143,885	1,100,947
Originated Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	383,164	353,008
Originated Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,325,740	1,313,645
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,946,482	1,922,349
Originated Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	593,481	585,347
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	478,318	498,843
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	36,435	37,526
Acquired Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,223	5,970
Acquired Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	239,609	248,760
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	191,894	201,195
Acquired Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 4,157	$ 5,392

Loans and Allowance for Credi_4

Loans and Allowance for Credit Losses - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non Accrual Status Of Loans After Number Of Days Past Due	90 days
Default Status Of TDRs After Number Of Days Past Due	90 days
Unfunded commitments related to nonperforming loans	$ 100,000		$ 1,600,000
Off balance sheet reserve to nonperforming loans	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	$ 0
Total gains or losses included in earnings	$ 0	2,840,000
Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non Accrual Status Of Loans After Number Of Days Past Due	150 days
Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans with modifications to rate and payment due to reamortization	$ 600,000	$ 100,000
Nonaccrual Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held for sale, Amount	0		$ 0
Loans and Leases Receivable, Gain (Loss) on Sales, Net	$ 0

Loans and Allowance for Credi_5

Loans and Allowance for Credit Losses - Credit Risk Profile by Creditworthiness (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 5,392,752	$ 5,275,296
Originated Loans [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	5,284,551	5,160,953
Originated Loans [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	73,632	79,294
Originated Loans [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	34,569	35,049
Originated Loans [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	108,201	114,343
Originated Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,143,885	1,100,947
Originated Loans [Member] | Commercial, financial, agricultural and other [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,107,013	1,055,394
Originated Loans [Member] | Commercial, financial, agricultural and other [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	31,225	33,723
Originated Loans [Member] | Commercial, financial, agricultural and other [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	5,647	11,830
Originated Loans [Member] | Commercial, financial, agricultural and other [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Commercial, financial, agricultural and other [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	36,872	45,553
Originated Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	383,164	353,008
Originated Loans [Member] | Real estate construction [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	374,201	337,367
Originated Loans [Member] | Real estate construction [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	8,963	15,641
Originated Loans [Member] | Real estate construction [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Real estate construction [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Real estate construction [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	8,963	15,641
Originated Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,325,740	1,313,645
Originated Loans [Member] | Residential real estate [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,315,339	1,302,912
Originated Loans [Member] | Residential real estate [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	809	1,026
Originated Loans [Member] | Residential real estate [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	9,592	9,707
Originated Loans [Member] | Residential real estate [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Residential real estate [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	10,401	10,733
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,946,482	1,922,349
Originated Loans [Member] | Commercial Real Estate [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,894,745	1,880,139
Originated Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	32,635	28,904
Originated Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	19,102	13,306
Originated Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Commercial Real Estate [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	51,737	42,210
Originated Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	593,481	585,347
Originated Loans [Member] | Loans to individuals [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	593,253	585,141
Originated Loans [Member] | Loans to individuals [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Loans to individuals [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	228	206
Originated Loans [Member] | Loans to individuals [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Originated Loans [Member] | Loans to individuals [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	228	206
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	478,318	498,843
Acquired Loans [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	466,018	485,951
Acquired Loans [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	7,441	7,700
Acquired Loans [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	4,859	5,192
Acquired Loans [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	12,300	12,892
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	36,435	37,526
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	30,627	31,399
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	5,672	5,890
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	136	237
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	5,808	6,127
Acquired Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	6,223	5,970
Acquired Loans [Member] | Real estate construction [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	5,602	5,337
Acquired Loans [Member] | Real estate construction [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	621	633
Acquired Loans [Member] | Real estate construction [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Real estate construction [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Real estate construction [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	621	633
Acquired Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	239,609	248,760
Acquired Loans [Member] | Residential real estate [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	236,594	245,637
Acquired Loans [Member] | Residential real estate [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	725	736
Acquired Loans [Member] | Residential real estate [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	2,290	2,387
Acquired Loans [Member] | Residential real estate [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Residential real estate [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	3,015	3,123
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	191,894	201,195
Acquired Loans [Member] | Commercial Real Estate [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	189,052	198,201
Acquired Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	423	441
Acquired Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	2,419	2,553
Acquired Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Commercial Real Estate [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	2,842	2,994
Acquired Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	4,157	5,392
Acquired Loans [Member] | Loans to individuals [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	4,143	5,377
Acquired Loans [Member] | Loans to individuals [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Loans to individuals [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	14	15
Acquired Loans [Member] | Loans to individuals [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	0	0
Acquired Loans [Member] | Loans to individuals [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 14	$ 15

Loans and Allowance for Credi_6

Loans and Allowance for Credit Losses - Age Analysis of Past Due Loans by Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 5,871,070	$ 5,774,139	$ 5,381,305
Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,180,320		1,131,594
Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	389,387		246,961
Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,565,349		1,434,623
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,138,376		2,027,072
Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	597,638		$ 541,055
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	3,431	3,512
Financing Receivable, Not Past Due	474,887	495,331
Total	478,318	498,843
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	100	205
Financing Receivable, Not Past Due	36,335	37,321
Total	36,435	37,526
Acquired Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	0	0
Financing Receivable, Not Past Due	6,223	5,970
Total	6,223	5,970
Acquired Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	2,120	2,181
Financing Receivable, Not Past Due	237,489	246,579
Total	239,609	248,760
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	1,132	1,042
Financing Receivable, Not Past Due	190,762	200,153
Total	191,894	201,195
Acquired Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	79	84
Financing Receivable, Not Past Due	4,078	5,308
Total	4,157	5,392
Acquired Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	305	273
Acquired Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	1
Acquired Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	98	226
Acquired Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	185	0
Acquired Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	22	46
Acquired Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	42	36
Acquired Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	35	24
Acquired Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	7	12
Acquired Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	207	38
Acquired Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	171	27
Acquired Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	36	11
Acquired Loans [Member] | Non Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	2,877	3,165
Acquired Loans [Member] | Non Accrual Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	100	204
Acquired Loans [Member] | Non Accrual Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Acquired Loans [Member] | Non Accrual Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	1,816	1,904
Acquired Loans [Member] | Non Accrual Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	947	1,042
Acquired Loans [Member] | Non Accrual Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	14	15
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	31,240	30,100
Financing Receivable, Not Past Due	5,361,512	5,245,196
Total	5,392,752	5,275,296
Originated Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	5,717	10,692
Financing Receivable, Not Past Due	1,138,168	1,090,255
Total	1,143,885	1,100,947
Originated Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	507	212
Financing Receivable, Not Past Due	382,657	352,796
Total	383,164	353,008
Originated Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	11,320	11,435
Financing Receivable, Not Past Due	1,314,420	1,302,210
Total	1,325,740	1,313,645
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	9,822	3,998
Financing Receivable, Not Past Due	1,936,660	1,918,351
Total	1,946,482	1,922,349
Originated Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment Equal To Or Greater Than Thirty Days Past Due	3,874	3,763
Financing Receivable, Not Past Due	589,607	581,584
Total	593,481	585,347
Originated Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	7,276	6,893
Originated Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	207	130
Originated Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	507	212
Originated Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	2,995	3,697
Originated Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	1,161	492
Originated Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	2,406	2,362
Originated Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	3,379	1,558
Originated Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	1,037	247
Originated Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Originated Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	1,739	710
Originated Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	122	69
Originated Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	481	532
Originated Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	1,302	1,544
Originated Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	83	92
Originated Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Originated Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	460	790
Originated Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Originated Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	759	662
Originated Loans [Member] | Non Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	19,283	20,105
Originated Loans [Member] | Non Accrual Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	4,390	10,223
Originated Loans [Member] | Non Accrual Loans [Member] | Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	0	0
Originated Loans [Member] | Non Accrual Loans [Member] | Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	6,126	6,238
Originated Loans [Member] | Non Accrual Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	8,539	3,437
Originated Loans [Member] | Non Accrual Loans [Member] | Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due and nonaccrual	$ 228	$ 207

Loans and Allowance for Credi_7

Loans and Allowance for Credit Losses - Recorded Investment and Unpaid Principal Balance for Impaired Loans with Associated Allowance (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Acquired Loans [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 3,416	$ 2,224
Impaired Financing Receivable, Interest Income, Accrual Method	2	1
Related allowance	0		$ 131
Recorded investment	2,998		3,292
Unpaid principal balance	4,447		4,877
Acquired Loans [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		131
Recorded investment	0		131
Unpaid principal balance	0		131
Acquired Loans [Member] | Commercial Financial Agricultural And Other With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	439	411
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Recorded investment	100		73
Unpaid principal balance	100		73
Acquired Loans [Member] | Real Estate Construction With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Recorded investment	0		0
Unpaid principal balance	0		0
Acquired Loans [Member] | Residential Real Estate With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1,981	678
Impaired Financing Receivable, Interest Income, Accrual Method	1	1
Recorded investment	1,937		2,031
Unpaid principal balance	2,369		2,604
Acquired Loans [Member] | Commercial Real Estate With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	982	907
Impaired Financing Receivable, Interest Income, Accrual Method	1	0
Recorded investment	947		1,042
Unpaid principal balance	1,962		2,052
Acquired Loans [Member] | Loans To Individuals With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	14	17
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Recorded investment	14		15
Unpaid principal balance	16		17
Acquired Loans [Member] | With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	3,416	2,013
Impaired Financing Receivable, Interest Income, Accrual Method	2	1
Recorded investment	2,998		3,161
Unpaid principal balance	4,447		4,746
Acquired Loans [Member] | Real Estate Construction With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		0
Recorded investment	0		0
Unpaid principal balance	0		0
Acquired Loans [Member] | Residential Real Estate With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	93
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		0
Recorded investment	0		0
Unpaid principal balance	0		0
Acquired Loans [Member] | Commercial Real Estate With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	118
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		0
Recorded investment	0		0
Unpaid principal balance	0		0
Acquired Loans [Member] | Loans To Individuals With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		0
Recorded investment	0		0
Unpaid principal balance	0		0
Acquired Loans [Member] | With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	211
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		131
Recorded investment	0		131
Unpaid principal balance	0		131
Originated Loans [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	24,773	44,781
Impaired Financing Receivable, Interest Income, Accrual Method	131	173
Related allowance	2,045		1,500
Recorded investment	28,282		28,735
Unpaid principal balance	37,163		38,787
Originated Loans [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	3,068	17,720
Impaired Financing Receivable, Interest Income, Accrual Method	3	66
Related allowance	1,012		797
Recorded investment	3,317		3,042
Unpaid principal balance	3,479		3,181
Originated Loans [Member] | Commercial Financial Agricultural And Other With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	2,707	8,130
Impaired Financing Receivable, Interest Income, Accrual Method	13	10
Recorded investment	2,599		8,735
Unpaid principal balance	9,100		16,442
Originated Loans [Member] | Real Estate Construction With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Recorded investment	0		0
Unpaid principal balance	0		0
Originated Loans [Member] | Residential Real Estate With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	10,798	10,401
Impaired Financing Receivable, Interest Income, Accrual Method	72	63
Recorded investment	10,545		10,726
Unpaid principal balance	12,264		12,571
Originated Loans [Member] | Commercial Real Estate With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	3,994	5,510
Impaired Financing Receivable, Interest Income, Accrual Method	36	31
Recorded investment	3,752		3,599
Unpaid principal balance	4,042		3,812
Originated Loans [Member] | Loans To Individuals With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	324	354
Impaired Financing Receivable, Interest Income, Accrual Method	1	2
Recorded investment	339		281
Unpaid principal balance	530		408
Originated Loans [Member] | With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	17,823	24,395
Impaired Financing Receivable, Interest Income, Accrual Method	122	106
Recorded investment	17,235		23,341
Unpaid principal balance	25,936		33,233
Originated Loans [Member] | Real Estate Construction With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		0
Recorded investment	0		0
Unpaid principal balance	0		0
Originated Loans [Member] | Residential Real Estate With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	604	706
Impaired Financing Receivable, Interest Income, Accrual Method	5	0
Related allowance	119		107
Recorded investment	713		486
Unpaid principal balance	713		495
Originated Loans [Member] | Commercial Real Estate With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	3,278	1,960
Impaired Financing Receivable, Interest Income, Accrual Method	1	1
Related allowance	914		596
Recorded investment	7,017		1,866
Unpaid principal balance	7,035		1,878
Originated Loans [Member] | Loans To Individuals With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Related allowance	0		0
Recorded investment	0		0
Unpaid principal balance	0		0
Originated Loans [Member] | With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	6,950	20,386
Impaired Financing Receivable, Interest Income, Accrual Method	9	$ 67
Related allowance	2,045		1,500
Recorded investment	11,047		5,394
Unpaid principal balance	$ 11,227		$ 5,554

Loans and Allowance for Credi_8

Loans and Allowance for Credit Losses - Troubled Debt Restructured Loans and Commitments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 14,994	$ 20,518
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	323	1,087
Letter of Credit [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	60	60
Unused lines of Credit [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	263	1,027
Accrual Loans [Member] [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring	9,120	8,757
Non Accrual Loans [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 5,874	$ 11,761

Loans and Allowance for Credi_9

Loans and Allowance for Credit Losses - Troubled Debt Restructurings Identified During Period (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)Contract	Mar. 31, 2018USD ($)Contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	12	18
Total Pre-Modification Outstanding Recorded Investment	$ 1,487	$ 8,387
Post- Modification Outstanding Recorded Investment	$ 1,445	$ 7,393
Troubled Debt Restructuring [Policy Text Block]	40000	775000
Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	1	2
Total Pre-Modification Outstanding Recorded Investment	$ 61	$ 4,871
Post- Modification Outstanding Recorded Investment	$ 62	$ 3,942
Troubled Debt Restructuring [Policy Text Block]	0	531
Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	6	11
Total Pre-Modification Outstanding Recorded Investment	$ 580	$ 441
Post- Modification Outstanding Recorded Investment	$ 570	$ 404
Troubled Debt Restructuring [Policy Text Block]	40	17
Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	2	1
Total Pre-Modification Outstanding Recorded Investment	$ 798	$ 3,017
Post- Modification Outstanding Recorded Investment	$ 767	$ 2,994
Troubled Debt Restructuring [Policy Text Block]	0	227
Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	3	4
Total Pre-Modification Outstanding Recorded Investment	$ 48	$ 58
Post- Modification Outstanding Recorded Investment	$ 46	$ 53
Troubled Debt Restructuring [Policy Text Block]	0	0
Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	$ 17	$ 7,746
Extended Maturity [Member] | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	0	4,709
Extended Maturity [Member] | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	17	20
Extended Maturity [Member] | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	0	3,017
Extended Maturity [Member] | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	0	0
Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	605	103
Contractual Interest Rate Reduction [Member] | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	0	0
Contractual Interest Rate Reduction [Member] | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	49	75
Contractual Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	556	0
Contractual Interest Rate Reduction [Member] | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	0	28
Contractual Payment Modification [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	865	538
Contractual Payment Modification [Member] | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	61	162
Contractual Payment Modification [Member] | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	514	346
Contractual Payment Modification [Member] | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	242	0
Contractual Payment Modification [Member] | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment	$ 48	$ 30

Loans and Allowance for Cred_10

Loans and Allowance for Credit Losses - Troubled Debt Restructuring is 90 Days or More Past Due (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)Contract	Mar. 31, 2018USD ($)Contract
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | Contract	1	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default | $	$ 10	$ 940
Commercial, financial, agricultural and other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | Contract	0	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default | $	$ 0	$ 940
Loans to individuals [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | Contract	1	0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default | $	$ 10	$ 0

Loans and Allowance for Cred_11

Loans and Allowance for Credit Losses - Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses	$ 4,095	$ 6,903
Ending Balance			$ 49,653		$ 53,732
Ending balance: individually evaluated for impaired			2,045		11,473
Ending balance: collectively evaluated for impaired			47,608		42,259
Total			5,871,070	$ 5,774,139	5,381,305
Ending balance: individually evaluated for impaired			20,676		50,491
Ending balance: collectively evaluated for impaired			5,850,394		5,330,814
Residential real estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Ending Balance			4,185		3,154
Total			1,565,349		1,434,623
Commercial Real Estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Ending Balance			19,218		18,496
Ending balance: individually evaluated for impaired			914		2,141
Ending balance: collectively evaluated for impaired			18,304		16,355
Total			2,138,376		2,027,072
Ending balance: individually evaluated for impaired			11,111		10,360
Ending balance: collectively evaluated for impaired			2,127,265		2,016,712
Commercial, financial, agricultural and other [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Ending Balance			19,833		27,552
Ending balance: individually evaluated for impaired			1,012		9,045
Ending balance: collectively evaluated for impaired			18,821		18,507
Total			1,180,320		1,131,594
Ending balance: individually evaluated for impaired			5,627		33,278
Ending balance: collectively evaluated for impaired			1,174,693		1,098,316
Real estate construction [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Ending Balance			2,254		1,114
Ending balance: individually evaluated for impaired			0		0
Ending balance: collectively evaluated for impaired			2,254		1,114
Total			389,387		246,961
Ending balance: individually evaluated for impaired			0		0
Ending balance: collectively evaluated for impaired			389,387		246,961
Residential real estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance: individually evaluated for impaired			119		287
Ending balance: collectively evaluated for impaired			4,066		2,867
Ending balance: individually evaluated for impaired			3,938		6,853
Ending balance: collectively evaluated for impaired			1,561,411		1,427,770
Loans to individuals [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Ending Balance			4,163		3,416
Ending balance: individually evaluated for impaired			0		0
Ending balance: collectively evaluated for impaired			4,163		3,416
Total			597,638		541,055
Ending balance: individually evaluated for impaired			0		0
Ending balance: collectively evaluated for impaired			597,638		541,055
Acquired Loans [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	178	46
Charge-offs	(576)	(20)
Recoveries	44	37
Provision for credit losses	407	(28)
Ending Balance	178	46	53	178	35
Total			478,318	498,843
Acquired Loans [Member] | Residential real estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	35	6
Charge-offs	(45)	(16)
Recoveries	24	17
Provision for credit losses	21	6
Ending Balance	35	6	35	35	13
Total			239,609	248,760
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	4	29
Charge-offs	0	0
Recoveries	0	0
Provision for credit losses	(4)	(27)
Ending Balance	4	29	0	4	2
Total			191,894	201,195
Acquired Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	139	11
Charge-offs	(526)	0
Recoveries	11	7
Provision for credit losses	394	2
Ending Balance	139	11	18	139	20
Total			36,435	37,526
Acquired Loans [Member] | Real estate construction [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	0	0
Charge-offs	0	0
Recoveries	0	6
Provision for credit losses	0	(6)
Ending Balance	0	0	0	0	0
Total			6,223	5,970
Acquired Loans [Member] | Loans to individuals [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	0	0
Charge-offs	(5)	(4)
Recoveries	9	7
Provision for credit losses	(4)	(3)
Ending Balance	0	0	0	0	0
Total			4,157	5,392
Originated Loans [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	47,586	48,252
Charge-offs	(2,028)	(2,082)
Recoveries	354	596
Provision for credit losses	3,688	6,931
Ending Balance	47,586	48,252	49,600	47,586	53,697
Total			5,392,752	5,275,296
Originated Loans [Member] | Residential real estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,934	2,753
Charge-offs	(136)	(455)
Recoveries	81	75
Provision for credit losses	271	768
Ending Balance	3,934	2,753	4,150	3,934	3,141
Total			1,325,740	1,313,645
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	18,382	17,328
Charge-offs	(299)	(168)
Recoveries	41	69
Provision for credit losses	1,094	1,265
Ending Balance	18,382	17,328	19,218	18,382	18,494
Total			1,946,482	1,922,349
Originated Loans [Member] | Commercial, financial, agricultural and other [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	19,235	23,418
Charge-offs	(483)	(290)
Recoveries	76	256
Provision for credit losses	987	4,148
Ending Balance	19,235	23,418	19,815	19,235	27,532
Total			1,143,885	1,100,947
Originated Loans [Member] | Real estate construction [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	2,002	1,349
Charge-offs	0	0
Recoveries	42	1
Provision for credit losses	210	(236)
Ending Balance	2,002	1,349	2,254	2,002	1,114
Total			383,164	353,008
Originated Loans [Member] | Loans to individuals [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	4,033	3,404
Charge-offs	(1,110)	(1,169)
Recoveries	114	195
Provision for credit losses	1,126	986
Ending Balance	$ 4,033	$ 3,404	4,163	4,033	$ 3,416
Total			$ 593,481	$ 585,347

Leases Operating Lease Assets a

Leases Operating Lease Assets and Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)Rate
Leases [Abstract]
Operating Lease, Right-of-Use Asset	$ 47,566
Operating Lease, Liability	51,371
Operating Lease, Cost	$ 1,337
Operating Lease, Weighted Average Remaining Lease Term	16 years 3 months 11 days
Operating Lease, Weighted Average Discount Rate, Percent | Rate	3.49%
Operating Leases, Rent Expense	$ 1,119

Leases Lease Liablity Maturity

Leases Lease Liablity Maturity (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 4,499
Operating Leases, Future Minimum Payments, Due in Two Years	4,517
Operating Leases, Future Minimum Payments, Due in Three Years	4,480
Operating Leases, Future Minimum Payments, Due in Four Years	4,413
Operating Leases, Future Minimum Payments, Due in Five Years	4,370
Operating Leases, Future Minimum Payments, Due Thereafter	46,528
Operating Leases, Future Minimum Payments Due	68,807
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	17,436
Operating Lease, Liability	$ 51,371

Income Taxes Income Taxes (Deta

Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2018	Dec. 31, 2017
Unrecognized Tax Benefits	$ 0
Cumulative effect of adoption of ASU 2018-02			$ 0
Retained Earnings [Member]
Cumulative effect of adoption of ASU 2018-02			$ 1,344
Effect of ASU Adoption [Member] | Retained Earnings [Member]
Cumulative effect of adoption of ASU 2018-02		$ 1,344

Fair Values of Assets and Lia_3

Fair Values of Assets and Liabilities - Quantitative Inputs and Assumptions Used in Level 3 Fair Value Measurements (Detail) - USD ($)		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value		$ 893,101,000	$ 909,247,000
Other Investments		25,378,000	32,126,000
Other Investments and Securities, at Cost			1,700,000
Assets		938,919,000	957,719,000
Impaired Loans [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		3,187,000
Impaired Loans [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		0
Impaired Loans [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		0
Impaired Loans [Member] | Reserve Study [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		1,044,000
Impaired Loans [Member] | Reserve Study [Member] | NGL per gallon [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs Monetary	[1]
Impaired Loans [Member] | Reserve Study [Member] | Minimum [Member] | Gas per MCF [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs Monetary		2.61
Impaired Loans [Member] | Reserve Study [Member] | Minimum [Member] | Oil per BBL/d [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs Monetary		47.09
Impaired Loans [Member] | Reserve Study [Member] | Maximum [Member] | Gas per MCF [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs Monetary		3.49
Impaired Loans [Member] | Reserve Study [Member] | Maximum [Member] | Oil per BBL/d [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs Monetary		$ 53.14
Impaired Loans [Member] | Reserve Study [Member] | Weighted average [Member] | Discount rates [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount Rate		10.00%
Limited Partnership Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		$ 3,200,000
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value		0	0
Other Investments		1,670,000	1,670,000
Assets		4,870,000	4,366,000
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned Assets Fair Value		4,300,000	4,035,000
Assets		33,540,000	34,431,000
Fair Value, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned Assets Fair Value		0	0
Assets		$ 14,849,000	$ 15,320,000
[1]	The remainder of impaired loans valued using Level 3 inputs are not included in this disclosure as the values of those loans are based on bankruptcy agreement documentation.

Fair Values of Assets and Lia_4

Fair Values of Assets and Liabilities - Schedule of Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 4,366	$ 27,459
Total gains or losses included in earnings	0	2,840
Total gains or losses included in other comprehensive income	(47)	4,529
Purchases	551	149
Issuances	0	0
Sales	0	0
Settlements	0	(16,883)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	4,870	18,094
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		23,646
Total gains or losses included in earnings		2,840
Total gains or losses included in other comprehensive income		4,529
Purchases		0
Issuances		0
Sales		0
Settlements		(16,883)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0
Balance, end of period		14,132
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,670	1,670
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	0	0
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	1,670	1,670
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,696	2,143
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	(47)	0
Purchases	551	149
Issuances	0	0
Sales	0	0
Settlements	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	3,200	2,292
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	$ 0	$ 0

Fair Values of Assets and Lia_5

Fair Values of Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2019		Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	$ 893,101		$ 909,247
Other investments	25,378		32,126
Loans Held for Sale	9,627		11,881
Other Assets	10,813	[1]	4,465	[2]
Total Assets	938,919		957,719
Other Liabilities	7,868	[1]	2,081	[2]
Total Liabilities	7,868		2,081
Limited Partnership Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	3,200
US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	9,246		9,406
US Government Agency Debt Securities Commercial [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	168,120		167,744
Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	653,966		673,361
Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	10,006		10,012
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	28,214		27,712
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	23,549		21,012
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Other investments	0		0
Loans Held for Sale	0		0
Other Assets	0	[1]	0	[2]
Total Assets	0		0
Other Liabilities	0	[1]	0	[2]
Total Liabilities	0		0
Level 1 [Member] | US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 1 [Member] | US Government Agency Debt Securities Commercial [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 1 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 1 [Member] | Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 1 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	893,101		909,247
Other investments	23,708		30,456
Loans Held for Sale	9,627		11,881
Other Assets	7,613	[1]	1,769	[2]
Total Assets	934,049		953,353
Other Liabilities	7,868	[1]	2,081	[2]
Total Liabilities	7,868		2,081
Level 2 [Member] | US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	9,246		9,406
Level 2 [Member] | US Government Agency Debt Securities Commercial [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	168,120		167,744
Level 2 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	653,966		673,361
Level 2 [Member] | Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	10,006		10,012
Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	28,214		27,712
Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	23,549		21,012
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Other investments	1,670		1,670
Loans Held for Sale	0		0
Other Assets	3,200	[1]	2,696	[2]
Total Assets	4,870		4,366
Other Liabilities	0	[1]	0	[2]
Total Liabilities	0		0
Level 3 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	0
Level 3 [Member] | US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 3 [Member] | US Government Agency Debt Securities Commercial [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 3 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 3 [Member] | Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 3 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0		0
Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	$ 0		$ 0
[1]	Hedging and non-hedging interest rate derivatives and limited partnership investments
[2]	on-hedging interest rate derivatives and limited partnership investments

Fair Values of Assets and Lia_6

Fair Values of Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Available-for-sale Securities	$ 893,101		$ 909,247
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	$ 0
Impaired loans considered to be credit risk of non-collection	100
Updated appraisal requirement floor	250
Other real estate owned	3,993		3,935
Financial instrument of credit risk	300		$ 200
Fair Value, Assets Measured on Recurring Basis, Gain (Loss) Included in Other Income, Assets and Liabilities Continue to be held	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Total gains or losses included in earnings	0	2,840
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Total gains or losses included in earnings	$ 0	$ 0
Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap Rates Term Used to Determine Yield Curve	3 years
Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap Rates Term Used to Determine Yield Curve	30 years

Fair Values of Assets and Lia_7

Fair Values of Assets and Liabilities - Schedule of Assets Measured on Non-Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	$ 938,919	$ 957,719
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	29,240	30,396
Other real estate owned	4,300	4,035
Total Assets	33,540	34,431
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	0	0
Level 1 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other real estate owned	0	0
Total Assets	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	934,049	953,353
Level 2 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	14,391	15,076
Other real estate owned	4,300	4,035
Total Assets	18,691	19,111
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	4,870	4,366
Level 3 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	14,849	15,320
Other real estate owned	0	0
Total Assets	$ 14,849	$ 15,320

Fair Values of Assets and Lia_8

Fair Values of Assets and Liabilities - Losses Realized on Assets Measured on Non-Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Impaired loans	$ (969)	$ (7,850)
Other real estate owned	(49)	(30)
Total losses	$ (1,018)	$ (7,880)

Fair Values of Assets and Lia_9

Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 100,724	$ 95,934
Interest-bearing deposits	23,168	3,013
Securities available for sale, at fair value	893,101	909,247
Debt Securities, Held-to-maturity	384,909	393,855
Other investments	25,378	32,126
Loans and Leases Receivable, Net of Deferred Income	5,871,070	5,774,139	$ 5,381,305
Deposits	6,130,760	5,897,992
Short-term borrowings	565,616	721,823
Subordinated debt	170,328	170,288
Long-term debt	7,395	7,551
Capital Lease Obligations	7,118	7,217
Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale, at fair value	0	0
Other investments	0	0
Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale, at fair value	893,101	909,247
Other investments	23,708	30,456
Level 3 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale, at fair value	0	0
Other investments	1,670	1,670
Carrying Amount [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	100,724	95,934
Interest-bearing deposits	23,168	3,013
Securities available for sale, at fair value	893,101	909,247
Debt Securities, Held-to-maturity	384,909	393,855
Other investments	25,378	32,126
Loans Held for sale, Amount	9,627	11,881
Loans and Leases Receivable, Net of Deferred Income	5,871,070	5,774,139
Deposits	6,130,760	5,897,992
Short-term borrowings	565,616	721,823
Subordinated debt	170,328	170,288
Long-term debt	7,395	7,551
Capital Lease Obligations	7,118	7,217
Estimate of Fair Value Measurement [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	100,724	95,934
Interest-bearing deposits	23,168	3,013
Securities available for sale, at fair value	893,101	909,247
Debt Securities, Held-to-maturity	380,443	383,993
Other investments	25,378	32,126
Loans Held for sale, Amount	9,627	11,881
Loans and Leases Receivable, Net of Deferred Income	5,921,319	5,821,791
Deposits	6,135,980	5,904,147
Short-term borrowings	565,522	721,532
Subordinated debt	169,764	168,067
Long-term debt	7,701	7,720
Capital Lease Obligations	7,118	7,217
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	100,724	95,934
Interest-bearing deposits	23,168	3,013
Securities available for sale, at fair value	0	0
Debt Securities, Held-to-maturity	0	0
Other investments	0	0
Loans Held for sale, Amount	0	0
Loans and Leases Receivable, Net of Deferred Income	0	0
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	0	0
Long-term debt	0	0
Capital Lease Obligations	0	0
Estimate of Fair Value Measurement [Member] | Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities available for sale, at fair value	893,101	909,247
Debt Securities, Held-to-maturity	380,443	383,993
Other investments	23,708	30,456
Loans Held for sale, Amount	9,627	11,881
Loans and Leases Receivable, Net of Deferred Income	14,391	15,076
Deposits	6,135,980	5,904,147
Short-term borrowings	565,522	721,532
Subordinated debt	0	0
Long-term debt	7,701	7,720
Capital Lease Obligations	7,118	7,217
Estimate of Fair Value Measurement [Member] | Level 3 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities available for sale, at fair value	0	0
Debt Securities, Held-to-maturity	0	0
Other investments	1,670	1,670
Loans Held for sale, Amount	0	0
Loans and Leases Receivable, Net of Deferred Income	5,906,928	5,806,715
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	169,764	168,067
Long-term debt	0	0
Capital Lease Obligations	$ 0	$ 0

Derivatives - Additional Inform

Derivatives - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)Derivatives	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Risk Participation Agreements Purchased [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps | Derivatives	31
Risk Participation Agreements Sold [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps | Derivatives	9
Forward Contracts [Member]
Risk participation Agreements [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ (64)	$ (62)
Derivative Liability, Cost Basis, Gross Asset	7,200		$ 6,900
Derivative Liability, Fair Value, Gross Asset	8,200		7,600
Derivative Liability, Notional Amount, Gross Asset	25,200		9,900
Forward Contracts [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Fair Value, Net	234		170
Derivative, Notional Amount	30,000		15,000
Foreign Exchange [Member]
Risk participation Agreements [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	2	(3)
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Fair Value, Net	(7)		6
Derivative, Notional Amount	1,797		1,927
Derivative Liability, Cost Basis, Gross Asset	1,800		1,900
Derivative Liability, Fair Value, Gross Asset	1,800		1,900
Interest Rate Swap [Member]
Risk participation Agreements [Line Items]
Derivative Instruments Designated As Hedging Instruments Interest Income	(118)	(81)
Derivative, Net Hedge Ineffectiveness Gain (Loss)	7	$ 0
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Fair Value, Net	0		133
Derivative, Notional Amount	$ 0		$ 65,000

Derivatives - Credit Value Adju

Derivatives - Credit Value Adjustment Recorded Related to Notional Amount of Derivatives Outstanding (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	$ (29)	$ (3)
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	370,693	411,645
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	0	(133)
Derivative, Notional Amount	0	65,000
Interest Rate Cap [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	36,028	36,111
interest Rate Collar [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	35,354	0
Credit Default Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	170,016	162,139
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	25,215	9,900
Forward Contracts [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	(234)	(170)
Derivative, Notional Amount	30,000	15,000
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	7	(6)
Derivative, Notional Amount	1,797	1,927
Short [Member] | Credit Default Swap, Selling Protection [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 46,871	$ 59,315

Derivatives - Schedule of Chang

Derivatives - Schedule of Changes in Fair Value of Derivative Assets and Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (470)	$ 789
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Instruments Designated As Hedging Instruments Interest Income	(118)	(81)
Derivative, Net Hedge Ineffectiveness Gain (Loss)	7	0
Forward Contracts [Member]
Derivative [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	(64)	(62)
Foreign Exchange [Member]
Derivative [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ 2	$ (3)

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Goodwill Disclosure [Abstract]
Goodwill	$ 274,202,000		$ 274,202,000
Impairment charges on goodwill	$ 0	$ 0

Subordinated Debentures Schedul

Subordinated Debentures Schedule of Subordinated Debentures Outstanding (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Subordinated debentures	$ 170,328	$ 170,288
First Commonwealth Bank 2028 [Member]
Debt Instrument [Line Items]
Subordinated debentures	49,152	49,131
First Commonwealth Bank 2033 [Member]
Debt Instrument [Line Items]
Subordinated debentures	49,009	48,990
First Commonwealth Capital Trust II [Member]
Debt Instrument [Line Items]
Subordinated debentures	30,929	30,929
First Commonwealth Capital Trust III [Member]
Debt Instrument [Line Items]
Subordinated debentures	$ 41,238	$ 41,238

Subordinated Debentures Subor_3

Subordinated Debentures Subordinated Debentures, Additional Information (Details) $ in Thousands	Mar. 31, 2019USD ($)
First Commonwealth Capital Trust II [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross	$ 630
First Commonwealth Bank 2028 [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross	923
First Commonwealth Bank 2033 [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross	1,051
First Commonwealth Capital Trust III [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross	$ 471

Revenue Recognition Revenue R_2

Revenue Recognition Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Additional Information [Abstract]
Management Fees, Incentive Revenue (Deprecated 2018-01-31)	$ 0.3
Brokerage Commissions Revenue	$ 0.7	$ 0.4

Revenue Recognition In-Scope an

Revenue Recognition In-Scope and Out-of-Scope Revenue Streams (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Trust income	$ 1,926	$ 1,928
Service charges on deposit accounts	4,245	4,406
Insurance and retail brokerage commissions	1,961	1,868
Card-related interchange income	4,730	4,742
Derivatives mark to market	(26)	789
Gain on sale of other loans and assets	1,084	574
Other income	1,705	1,628
Noninterest Income	18,872	22,043
In-Scope of Topic 606 [Member]
Trust income	1,926	1,928
Service charges on deposit accounts	4,245	4,406
Insurance and retail brokerage commissions	1,961	1,868
Card-related interchange income	4,730	4,742
Gain on sale of other loans and assets	258	207
Other income	862	892
Noninterest Income	13,982	14,043
Out-Of-Scope of Topic 606 [Member]
Noninterest Income	$ 4,890	$ 8,000

Subsequent Event Subsequent Eve

Subsequent Event Subsequent Event Table (Details) $ in Millions	Mar. 31, 2019USD ($)
Subsequent Event [Line Items]
Branch Acquisition, Number of Branches	14
Branch Acquisition, Total Deposits	$ 525
Branch Acquisition, Total Loans	$ 120