Otter Tail (OTTR) 10-Q 9 Aug 17 2017 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 31, 2017
Document Information [Line Items]
Entity Registrant Name	Otter Tail Corp
Entity Central Index Key	1,466,593
Trading Symbol	ottr
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		39,557,391
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Amendment Flag	false

Consolidated Balance Sheets (Cu

Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current Assets
Cash and Cash Equivalents
Accounts Receivable:
Trade—Net	79,029	68,242
Other	7,895	5,850
Inventories	87,267	83,740
Unbilled Revenues	15,560	20,080
Income Taxes Receivable		662
Regulatory Assets	16,540	21,297
Other	14,352	8,144
Total Current Assets	220,643	208,015
Investments	8,156	8,417
Other Assets	35,253	34,104
Balance	37,572	37,572
Other Intangibles—Net	14,391	14,958
Regulatory Assets	127,479	132,094
Plant
Electric Plant in Service	1,870,928	1,860,357
Nonelectric Operations	214,925	211,826
Construction Work in Progress	188,450	153,261
Total Gross Plant	2,274,303	2,225,444
Less Accumulated Depreciation and Amortization	773,741	748,219
Net Plant	1,500,562	1,477,225
Total Assets	1,944,056	1,912,385
Current Liabilities
Short-Term Debt	58,117	42,883
Current Maturities of Long-Term Debt	42,200	33,201
Accounts Payable	94,353	89,350
Accrued Salaries and Wages	15,115	17,497
Accrued Taxes	10,954	16,000
Other Accrued Liabilities	15,142	15,377
Liabilities of Discontinued Operations	1,113	1,363
Total Current Liabilities	236,994	215,671
Pensions Benefit Liability	98,297	97,627
Other Postretirement Benefits Liability	62,980	62,571
Other Noncurrent Liabilities	22,441	21,706
Commitments and Contingencies (note 9)
Deferred Credits
Deferred Income Taxes	235,554	226,591
Deferred Tax Credits	22,115	22,849
Regulatory Liabilities	83,561	82,433
Other	5,324	7,492
Total Deferred Credits	346,554	339,365
Capitalization
Long-Term Debt—Net	490,386	505,341
Common Shares, Par Value $5 Per Share—Authorized, 50,000,000 Shares; Outstanding, 2017—39,555,076 Shares; 2016—39,348,136 Shares	197,775	196,741
Premium on Common Shares	341,657	337,684
Retained Earnings	150,558	139,479
Accumulated Other Comprehensive Loss	(3,586)	(3,800)
Total Common Equity	686,404	670,104
Total Capitalization	1,176,790	1,175,445
Total Liabilities and Equity	1,944,056	1,912,385
Cumulative Preferred Shares [Member]
Capitalization
Cumulative Shares
Cumulative Preference Shares [Member]
Capitalization
Cumulative Shares

Consolidated Balance Sheets (C3

Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Common shares, par value (in dollars per share)	$ 5	$ 5
Common shares, authorized (in shares)	50,000,000	50,000,000
Common shares, outstanding (in shares)	39,555,076	39,348,136
Cumulative Preferred Shares [Member]
Cumulative shares, without par value (in dollars per share)	$ 0	$ 0
Cumulative shares, outstanding (in shares)	0	0
Cumulative shares, authorized (in shares)	1,500,000	1,500,000
Cumulative Preference Shares [Member]
Cumulative shares, without par value (in dollars per share)	$ 0	$ 0
Cumulative shares, outstanding (in shares)	0	0
Cumulative shares, authorized (in shares)	1,000,000	1,000,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating Revenues
Electric	$ 102,231	$ 97,918	$ 220,774	$ 210,903
Product Sales	109,855	105,564	205,429	198,821
Total Operating Revenues	212,086	203,482	426,203	409,724
Operating Expenses
Production Fuel – Electric	12,477	9,990	28,859	25,690
Purchased Power – Electric System Use	16,376	15,127	35,564	32,013
Electric Operation and Maintenance Expenses	37,850	38,981	76,229	78,999
Cost of Products Sold (depreciation included below)	84,013	80,949	159,290	153,588
Other Nonelectric Expenses	10,164	9,238	20,602	20,693
Depreciation and Amortization	17,908	18,525	35,762	36,814
Property Taxes – Electric	3,709	3,589	7,507	7,268
Total Operating Expenses	182,497	176,399	363,813	355,065
Operating Income	29,589	27,083	62,390	54,659
Interest Charges	7,527	7,976	14,989	15,970
Other Income	552	1,532	1,105	1,932
Income Before Income Taxes—Continuing Operations	22,614	20,639	48,506	40,621
Income Tax Expense—Continuing Operations	5,897	5,083	12,260	10,575
Net Income from Continuing Operations	16,717	15,556	36,246	30,046
Discontinued Operations
Income – net of Income Tax Expense of $40, $80, $78 and $100 for the respective periods	61	119	117	149
Net Income	$ 16,778	$ 15,675	$ 36,363	$ 30,195
Average Number of Common Shares Outstanding—Basic (in shares)	39,462,865	38,179,371	39,406,834	38,058,157
Average Number of Common Shares Outstanding—Diluted (in shares)	39,702,499	38,321,289	39,671,612	38,183,249
Basic Earnings Per Common Share:
Continuing Operations (in dollars per share)	$ 0.43	$ 0.41	$ 0.92	$ 0.79
Discontinued Operations (in dollars per share)
(in dollars per share)	0.43	0.41	0.92	0.79
Diluted Earnings Per Common Share:
Continuing Operations (in dollars per share)	0.42	0.41	0.92	0.79
Discontinued Operations (in dollars per share)
(in dollars per share)	0.42	0.41	0.92	0.79
Dividends Declared Per Common Share (in dollars per share)	$ 0.32	$ 0.3125	$ 0.64	$ 0.625

Consolidated Statements of Inc5

Consolidated Statements of Income (Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Expense - Discontinued Operations	$ 40	$ 80	$ 78	$ 100

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net Income	$ 16,778	$ 15,675	$ 36,363	$ 30,195
Unrealized Gain on Available-for-Sale Securities:
Reversal of Previously Recognized Gains Realized on Sale of Investments and Included in Other Income During Period	(1)		(1)
Gains Arising During Period	21	27	38	100
Income Tax Expense	(7)	(9)	(13)	(35)
Change in Unrealized Gains on Available-for-Sale Securities – net-of-tax	13	18	24	65
Pension and Postretirement Benefit Plans:
Amortization of Unrecognized Postretirement Benefit Losses and Costs (note 11)	159	155	316	309
Income Tax Expense	(63)	(63)	(126)	(124)
Pension and Postretirement Benefit Plans – net-of-tax	96	92	190	185
Total Other Comprehensive Income	109	110	214	250
Total Comprehensive Income	$ 16,887	$ 15,785	$ 36,577	$ 30,445

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows from Operating Activities
Net Income	$ 36,363	$ 30,195
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Net Income from Discontinued Operations	(117)	(149)
Depreciation and Amortization	35,762	36,814
Deferred Tax Credits	(734)	(828)
Deferred Income Taxes	8,666	9,679
Change in Deferred Debits and Other Assets	8,075	2,680
Discretionary Contribution to Pension Plan		(10,000)
Change in Noncurrent Liabilities and Deferred Credits	(695)	6,404
Allowance for Equity/Other Funds Used During Construction	(401)	(475)
Stock Compensation Expense—Equity Awards	1,920	828
Other—Net	39	(76)
Cash (Used for) Provided by Current Assets and Current Liabilities:
Change in Receivables	(12,832)	(12,673)
Change in Inventories	(3,527)	4,218
Change in Other Current Assets	2,095	(1,043)
Change in Payables and Other Current Liabilities	(5,878)	(5,441)
Change in Interest and Income Taxes Receivable/Payable	590	4,018
Net Cash Provided by Continuing Operations	69,326	64,151
Net Cash (Used in) Provided by Discontinued Operations	(54)	11
Net Cash Provided by Operating Activities	69,272	64,162
Cash Flows from Investing Activities
Capital Expenditures	(56,354)	(79,158)
Net Proceeds from Disposal of Noncurrent Assets	2,167	1,080
Final Purchase Price Adjustment – BTD-Georgia Acquisition		1,500
Cash Used for Investments and Other Assets	(2,431)	(1,719)
Net Cash Used in Investing Activities	(56,618)	(78,297)
Cash Flows from Financing Activities
Change in Checks Written in Excess of Cash	1,043	(2,024)
Net Short-Term Borrowings (Repayments)	15,234	(31,398)
Proceeds from Issuance of Common Stock – net of Issuance Expenses	4,266	21,645
Payments for Retirement of Capital Stock	(1,799)	(104)
Proceeds from Issuance of Long-Term Debt		50,000
Short-Term and Long-Term Debt Issuance Expenses		(59)
Payments for Retirement of Long-Term Debt	(6,114)	(106)
Dividends Paid	(25,284)	(23,819)
Net Cash (Used in) Provided by Financing Activities	(12,654)	14,135
Net Change in Cash and Cash Equivalents
Cash and Cash Equivalents at Beginning of Period
Cash and Cash Equivalents at End of Period

Note 1 - Summary of Significant

Note 1 - Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Significant Accounting Policies and New Accounting Pronouncements [Text Block]	1. Revenue Recognition Due to the diverse business operations of the Company, revenue recognition depends on the product produced and sold or service performed. The Company recognizes revenue when the earnings process is complete, evidenced by an agreement with the customer, there has been delivery and acceptance, the price is fixed or determinable and collectability is reasonably assured. In cases where significant obligations remain after delivery, revenue recognition is deferred until such obligations are fulfilled. Provisions for sales returns and warranty costs are recorded at the time of the sale based on historical information and current trends. Gains and losses on forward energy contracts subject to regulatory treatment, if any, are deferred and recognized on a net basis in revenue in the period realized. For the Company ’s operating companies recognizing revenue on certain products when shipped, those operating companies have no Agreements Subject to Legally Enforceable Netting Arrangements The Company does not Fair Value Measurements The Company follows Accounting Standards Codification (ASC) Topic 820, Fair Value Measurements and Disclosures 820 820 three Level 1 – Quoted prices are available in active markets for identical assets or liabilities as of the reported date. The types of assets and liabilities included in Level 1 Level 2 – Pricing inputs are other than quoted prices in active markets, but are either directly or indirectly observable as of the reported date. The types of assets and liabilities included in Level 2 Level 3 – Significant inputs to pricing have little or no 3 may The following tables present, for each of the hierarchy levels, the Company ’s assets and liabilities that are measured at fair value on a recurring basis as of June 30, 2017 December 31, 2016: June 30 , 201 7 (in thousands) Level 1 Level 2 Level 3 Assets: Investments: Equity Funds – Held by Captive Insurance Company $ 879 Corporate Debt Securities – Held by Captive Insurance Company $ 4,991 Government -Backed and Government-Sponsored ’ Debt Securities – Held by Captive Insurance Company 2,099 Other Assets: Money Market and Mutual Funds – Nonqualified Retirement Savings Plan 781 Total Assets $ 1,660 $ 7,090 December 31, 201 6 (in thousands) Level 1 Level 2 Level 3 Assets: Investments: Corporate Debt Securities – Held by Captive Insurance Company $ 5,280 Government -Backed and Government-Sponsored ’ Debt Securities – Held by Captive Insurance Company 2,945 Other Assets: Money Market and Mutual Funds – Nonqualified Retirement Savings Plan $ 849 Total Assets $ 849 $ 8,225 The valuation techniques and inputs used for the Level 2 Government-Backed and Government-Sponsored Enterprises ’ and Corporate Debt Securities Held by the Company’s Captive Insurance Company – Fair values are determined on the basis of valuations provided by a third may Coyote Station Lignite Supply Agreement – Variable Interest Entity —In October 2012 May 2016 December 2040. May 2016 December 2040 No none, none not If the LSA terminates prior to the expiration of its term or the production period terminates prior to December 31, 2040 ’s applicable lender) assume, all of CCMC’s obligations owed to CCMC’s lenders under its loans and leases. The Coyote Station owners have limited rights to assign their rights and obligations under the LSA without the consent of CCMC’s lenders during any period in which CCMC’s obligations to its lenders remain outstanding. In the event the contract is terminated because regulations or legislation render the burning of coal cost prohibitive and the assets worthless, OTP’s maximum exposure to loss as a result of its involvement with CCMC as of June 30, 2017 $58.9 35% Inventories Inventories , valued at the lower of cost or net realizable value, consist of the following: June 30 , December 31, (in thousands) 201 7 201 6 Finished Goods $ 24,646 $ 27,755 Work in Process 13,977 11,754 Raw Material, Fuel and Supplies 48,644 44,231 Total Inventories $ 87,267 $ 83,740 Goodwill and Other Intangible Assets An assessment of the carrying amounts of goodwill of the Company ’s operating units as of December 31, 2016 not The following table indicates there were no first six 2017: (in thousands) Gross Balance December 31, 2016 Accumulated Impairments Balance (net of impairments) December 31, 2016 Adjustments to Goodwill in 201 7 Balance (net of impairments) June 30, 2017 Manufacturing $ 18,270 $ -- $ 18,270 $ -- $ 18,270 Plastics 19,302 -- 19,302 -- 19,302 Total $ 37,572 $ -- $ 37,572 $ -- $ 37,572 Intangible assets with finite lives are amortized over their estimated useful lives and reviewed for impairment in accordance with requirements under ASC Topic 360 10 35, Property, Plant, and Equipment—Overall—Subsequent Measurement The following table summarizes the components of the Company ’s intangible assets at June 30, 2017 December 31, 2016: June 30 , 2017 (in thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Remaining Amortization Periods (months) Amortizable Intangible Assets: Customer Relationships $ 22,491 $ 8,427 $ 14,064 30 - 218 Covenant not to Compete 590 361 229 14 Other 98 -- 98 36 Total $ 23,179 $ 8,788 $ 14,391 December 31, 2016 (in thousands) Amortizable Intangible Assets: Customer Relationships $ 22,491 $ 7,861 $ 14,630 36 - 224 Covenant not to Compete 590 262 328 20 Total $ 23,081 $ 8,123 $ 14,958 The amortization expense for these intangible assets was: Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Amortization Expense – Intangible Assets $ 333 $ 398 $ 665 $ 755 The estimated annual amortization expense for these intangible assets for the next five (in thousands) 2017 2018 2019 2020 2021 Estimated Amortization Expense – Intangible Assets $ 1,330 $ 1,264 $ 1,133 $ 1,099 $ 1,099 Supplemental Disclosures of Cash Flow Information As of June 30, (in thousands) 201 7 201 6 Noncash Investing Activities: Transactions Related to Capital Additions not Settled in Cash $ 16,312 $ 17,837 New Accounting Standards Adopted Accounting Standards Update ( ASU ) 2015 11 July 2015 No. 2015 11, Inventory (Topic 330 December 15, 2016. 2015 11 first 2017. not New Accounting Standards Pending Adopt ion ASU 2014 09 —In May 2014 No. 2014 09, Revenue from Contracts with Customers (Topic 606 606 606 606 Amendments to the ASC in ASU 2014 09, December 15, 2017. not January 1, 2017. 1 2 one 3 application. The Company does not January 1, 2018. June 30, 2017 2014 09 not 2014 09. 2014 09 January 1, 2018, 2014 09 may ASU 2016 02 —In February 2016 No. 2016 02, Leases (Topic 842 2016 02 2016 02 842, 840 842 842 842 842 2016 02 December 15, 2018, 2016 02 2016 02, 2016 02 not 2016 02 2019. ASU 2017 04 —In January 2017 No. 2017 04, Intangibles—Goodwill and Other (Topic 350 2017 04 simplifies how an entity is required to test goodwill for impairment by eliminating Step 2 2 In computing the implied fair value of goodwill under Step 2, Under the amendments in ASU 2017 04, not The amendments in ASU 2017 04 no 2 2017 04 December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. ASU 2017 07 —In March 2017 No. 2017 07, Compensation—Retirement Benefits (Topic 715 2017 07 is intended to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. ASC Topic 715, Compensation—Retirement Benefits 715 , not not The amendments in ASU 2017 07 715 2017 07 2017 07 December 15, 2017, The majority of the Company ’s benefit costs to which the amendments in ASU 2017 07 2017 07 2017 07 may may 2017 07. not 2017 07 first 2018,

Note 2 - Segment Information

Note 2 - Segment Information	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Segment Reporting Disclosure [Text Block]	2. Segment Information Segment Information The accounting policies of the segments are described under note 1 – Summary of Significant Accounting Policies. The Company's businesses have been classified into three These businesses sell products and provide services to customers primarily in the United States. The Company’s business structure currently includes the following three Electric includes the production, transmission, distribution and sale of electric energy in Minnesota, North Dakota and South Dakota by OTP. In addition, OTP is a participant in the Midcontinent Independent System Operator, Inc. (MISO) markets. OTP ’s operations have been the Company’s primary business since 1907. Manufacturing consists of businesses in the following manufacturing activities: contract machining, metal parts stamping, fabrication and painting, and production of plastic thermoformed horticultural containers, life science and industrial packaging, and material handling components. These businesses have manufacturing facilities in Georgia, Illinois and Minnesota and sell products primarily in the United States. Plastics consists of businesses producing polyvinyl chloride (PVC) pipe at plants in North Dakota and Arizona. The PVC pipe is sold primarily in the upper Midwest and Southwest regions of the United States. OTP is a wholly owned subsidiary of the Company. All of the Company ’s other businesses are owned by its wholly owned subsidiary, Varistar Corporation (Varistar). The Company’s Corporate operating costs include items such as corporate staff and overhead costs, the results of the Company’s captive insurance company and other items excluded from the measurement of operating segment performance. Corporate assets consist primarily of cash, prepaid expenses, investments and fixed assets. Corporate is not No 10% ’s consolidated revenues in 2016. 98.3% 98.5% three June 30, 2017 2016, 98.3% 98.7% six June 30, 2017 2016. The Company evaluates the performance of its business segments and allocates resources to them based on earnings contribution and return on total invested capital. Information for the business segments for the three six June 30, 2017 2016 June 30, 2017 December 31, 2016 Operating Revenue Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 102,236 $ 97,925 $ 220,787 $ 210,919 Manufacturing 59,304 58,452 117,721 118,272 Plastics 50,551 47,112 87,708 80,549 Intersegment Eliminations (5 ) (7 ) (13 ) (16 ) Total $ 212,086 $ 203,482 $ 426,203 $ 409,724 Interest Charges Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 6,439 $ 6,156 $ 12,825 $ 12,440 Manufacturing 553 1,006 1,107 1,998 Plastics 173 279 326 523 Corporate and Intersegment Eliminations 362 535 731 1,009 Total $ 7,527 $ 7,976 $ 14,989 $ 15,970 Income Taxes Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 2,442 $ 1,920 $ 8,504 $ 6,532 Manufacturing 1,573 1,791 2,628 2,810 Plastics 2,858 2,262 4,248 3,629 Corporate (976 ) (890 ) (3,120 ) (2,396 ) Total $ 5,897 $ 5,083 $ 12,260 $ 10,575 Net Income (Loss) Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 10,134 $ 9,148 $ 25,694 $ 21,686 Manufacturing 2,955 3,009 5,127 4,862 Plastics 4,637 3,485 7,074 5,637 Corporate (1,009 ) (86 ) (1,649 ) (2,139 ) Discontinued Operations 61 119 117 149 Total $ 16,778 $ 15,675 $ 36,363 $ 30,195 Identifiable Assets June 30 , December 31, (in thousands) 201 7 201 6 Electric $ 1,639,699 $ 1,622,231 Manufacturing 170,429 166,525 Plastics 94,900 84,592 Corporate 39,028 39,037 Total $ 1,944,056 $ 1,912,385

Note 3 - Rate and Regulatory Ma

Note 3 - Rate and Regulatory Matters	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Public Utilities Disclosure [Text Block]	3. Below are descriptions of OTP ’s major capital expenditure projects that have had, or will have, a significant impact on OTP’s revenue requirements, rates and alternative revenue recovery mechanisms, followed by summaries of specific electric rate or rider proceedings with the Minnesota Public Utilities Commission (MPUC), the North Dakota Public Service Commission (NDPSC), the South Dakota Public Utilities Commission (SDPUC) and the Federal Energy Regulatory Commission (FERC) impacting OTP’s revenues in 2017 2016. Major Capital Expenditure Projects The Big Stone South – Brookings Multi-Value Transmission Project ( MVP ) and Capacity Expansion 2020 CapX2020 ) Project 345 70 December 2011. Construction began on this line in the third 2015 2017. OTP’s capitalized costs on this project as of June 30, 2017 $66.3 100% The Big Stone South – Ellendale MVP —This is a 345 163 December 2011. second 2016 2019. June 30, 2017 $65.5 100% Recovery of OTP ’s major transmission investments is through the MISO Tariff (several as MVPs) and, currently, Minnesota, North Dakota and South Dakota Transmission Cost Recovery (TCR) Riders. Minnesota 2016 —The MPUC rendered its final decision in OTP’s 2016 March 2017 May 1, 2017. 8.61% 7.5056% 10.74% 9.41%. July 6, 2017 May 1, 2017 ($ in thousands) Initial Request February 16, 2016 Interim Rate s Authorized April 14, 2016 Projected Final Rates Revenue Increase – Annualized based on Test Year Data $ 19,296 $ 16,816 $ 12,100 Revenue Percent Increase 9.80 % 9.56 % 6.23 % Return on Rate Base 8.07 % 8.07 % 7.5056 % Jurisdictional Rate Base based on Test Year Data $ 483,000 $ 483,000 $ 471,000 Return on Equity 10.40 % 10.1 % 9.41 % Based on Equity to Total Capital of 52.50 % 52.50 % 52.50 % Debt to Total Capital 47.50 % 47.50 % 47.50 % Interim Revenue (in thousands) April 16, 2016 through June 30, 2017 Billed and Accrued $ 18,956 Accrued Refund $ 7,449 Net Interim Revenue Earned and Reported $ 11,507 Interest on Refundable Amount $ 163 Refund Liability as of June 30, 2017 $ 7,612 OTP will continue to accrue the interim rate refund until final rates become effective , expected for bills rendered on and after November 1, 2017. The interim rate refund, including interest, will be applied as a credit to Minnesota customers’ electric bills in the fourth 2017. The MPUC ’s order also included: ( 1 2 Minnesota Conservation Improvement Programs (MNCIP) not May 25, 2016 13.5% 2017 12% 2018 10% 2019 1.7% 50% $5.0 2016, $4.3 2015 $3.0 2014. The MNDOC recently granted two two two Transmission Cost Recovery Rider —The Minnesota Public Utilities Act provides a mechanism for automatic adjustment outside of a general rate proceeding to recover the costs of new transmission facilities that meet certain criteria, plus a return on investment at the level approved in a utility’s last general rate case. Additionally, following approval of the rate schedule, the MPUC may In OTP ’s 2016 Environmental Cost Recovery Rider —OTP has an ECR rider for recovery of OTP’s Minnesota jurisdictional share of the revenue requirements of its investment in the Big Stone Plant Air Quality Control System (AQCS). The ECR rider provides for a return on the project’s construction work in progress (CWIP) balance at the level approved in OTP’s 2010 2016 North Dakota General Rates —OTP’s most recent general rate increase in North Dakota of $3.6 3.0%, November 25, 2009 December 2009. 8.62%, 10.75%. Renewable Resource Adjustment —OTP has a North Dakota Renewable Resource Adjustment which enables OTP to recover its North Dakota jurisdictional share of investments in renewable energy facilities. This rider allows OTP to recover costs associated with new renewable energy projects as they are completed, along with a return on investment. Transmission Cost Recovery Rider —North Dakota law provides a mechanism for automatic adjustment outside of a general rate proceeding to recover jurisdictional capital and operating costs incurred by a public utility for new or modified electric transmission facilities. For qualifying projects, the law authorizes a current return on CWIP and a return on investment at the level approved in the utility's most recent general rate case. Environmental Cost Recovery Rider —OTP has an ECR rider in North Dakota to recover its North Dakota jurisdictional share of the revenue requirements associated with its investment in the Big Stone Plant AQCS and Hoot Lake Plant Mercury and Air Toxics Standards (MATS) projects. The ECR rider provides for a current return on CWIP and a return on investment at the level approved in OTP’s most recent general rate case. South Dakota 2010 —OTP’s most recent general rate increase in South Dakota of approximately $643,000 2.32% April 21, 2011 June 1, 2011. 8.50%. Transmission Cost Recovery Rider —South Dakota law provides a mechanism for automatic adjustment outside of a general rate proceeding to recover jurisdictional capital and operating costs incurred by a public utility for new or modified electric transmission facilities. Environmental Cost Recovery Rider —OTP has an ECR rider in South Dakota to recover its South Dakota jurisdictional share of revenue requirements associated with its investment in the Big Stone Plant AQCS and Hoot Lake Plant MATS projects. Rate Rider Updates The following table provides summary information on the status of updates since January 1, 2015 Rate Rider R - Request Date A - Approval Date Effective Date Requested or Approved Annual Revenue ($000s) Rate Minnesota Conservation Improvement Program 2016 Incentive and Cost Recovery R – March 31, 2017 October 1, 201 7 $ 9,868 $0.00754/kwh 2015 Incentive and Cost Recovery A – July 19, 2016 October 1, 2016 $ 8,590 $0.00275/kwh 2014 Incentive and Cost Recovery A – July 10, 2015 October 1, 2015 $ 8,689 $0.00287/kwh Transmission Cost Recovery 201 6 Annual Update 1 A – July 5, 2016 September 1, 2016 $ 4,736 Various 2015 Annual Update A – March 9, 2016 April 1, 2016 $ 7,203 Various 2014 Annual Update A – February 18, 2015 March 1, 2015 $ 8,388 Various Environmental Cost Recovery 201 6 Annual Update 1 A – July 5, 2016 September 1, 2016 $ 11,884 6.927% of Rev 2015 Annual Update A – March 9, 2016 October 1, 2015 $ 12,104 7.006% of Rev North Dakota Renewable Resource Adjustment 201 6 Annual Update A – March 15, 2017 April 1, 2017 $ 9,156 7.00 5% of Rev 2015 Annual Update A – June 22, 2016 July 1, 2016 $ 9,262 7. 573% of Rev 201 4 Annual Update A – March 25, 2015 April 1, 2015 $ 5,441 4.069% of Rev Transmission Cost Recovery 201 6 Annual Update A – December 14, 2016 January 1, 2017 $ 6,916 Various 2015 Annual Update A – December 16, 2015 January 1, 2016 $ 9,985 Various Environmental Cost Recovery 201 7 Annual Update A – July 12, 2017 August 1, 2017 $ 9,917 7.633% of base 201 6 Annual Update A – June 22, 2016 July 1, 2016 $ 10,359 7. 904% of base 2015 Annual Update A – June 17, 2015 July 1, 2015 $ 12,249 9.193 % of base South Dakota Transmission Cost Recovery 201 6 Annual Update A – February 17, 2017 March 1, 2017 $ 2,053 Various 2015 Annual Update A – February 12, 2016 March 1, 2016 $ 1,895 Various 2014 Annual Update A – February 13, 2015 March 1, 2015 $ 1,538 Various Environmental Cost Recovery 201 6 Annual Update A – October 26, 2016 November 1, 2016 $ 2,238 $0.00536/kwh 201 5 Annual Update A – October 15, 2015 November 1, 2015 $ 2,728 $0.00643/kwh 1 Approved on a provisional basis and subject to change based on comments from the MNDOC. The following table presents revenue recorded by OTP under rate riders in place in Minnesota, North Dakota and South Dakota: Revenues R ecorded under R ider R ates Three Months Ended June 30, Six Months Ended June 30, Rate Rider (in thousands) 2017 2016 2017 2016 Minnesota Conservation Improvement Program Costs and Incentives 1 $ 2,102 $ 2,209 $ 4,068 $ 4,715 Transmission Cost Recovery 1,273 1,133 3,443 3,409 Environmental Cost Recovery 2,812 3,153 5,636 6,235 North Dakota Renewable Resource Adjustment 1,839 1,922 3,609 3,981 Transmission Cost Recovery 1,384 1,969 3,895 4,205 Environmental Cost Recovery 2,388 2,771 4,876 5,582 South Dakota Transmission Cost Recovery 287 411 728 1,062 Environmental Cost Recovery 545 627 1,142 1,260 Conservation Improvement Program Costs and Incentives 176 124 416 283 1 Includes MNCIP costs recovered in base rates. FERC Wholesale power sales and transmission rates are subject to the jurisdiction of the FERC under the Federal Power Act of 1935, one Multi-Value Transmission Projects —On December 16, 2010 On November 12, 2013 may 12.38% ’s transmission rates to a proposed 9.15%. 15 November 12, 2013 February 11, 2015. December 22, 2015 10.32%, September 28, 2016 10.32 On November 6, 2014 50 January 5, 2015 November 12, 2013 ’s incentive rate filing, OTP’s ROE will be 10.82% 10.32 0.5% September 28, 2016. On February 12, 2015 may 12.38% 8.67%. second second 15 February 12, 2015 May 11, 2016. June 18, 2015 February 16, 2016. June 30, 2016 ’ ROE should be 9.7%. second Based on the probable reduction by the FERC in the ROE component of the MISO Tariff, OTP had a $2.7 December 31, 2016, first 15 February June 2017 2016 $2.7 December 31, 2016 $1.6 June 30, 2017.

Note 4 - Regulatory Assets and

Note 4 - Regulatory Assets and Liabilities	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Schedule of Regulatory Assets and Liabilities [Text Block]	4. As a regulated entity, OTP accounts for the financial effects of regulation in accordance with ASC Topic 980, Regulated Operations 980 980 605 25 June 30 , 2017 Remaining Recovery/ Refund Period (in thousands) Current Long-Term Total (months) Regulatory Assets: Prior Service Costs and Actuarial Losses on Pensions and Other Postretirement Benefits 1 $ 6,444 $ 105,045 $ 111,489 see below Conservation Improvement Program Costs and Incentives 2 3,185 6,705 9,890 27 Deferred Marked-to-Market Losses 1 4,063 4,436 8,499 4 2 Accumulated ARO Accretion/Depreciation Adjustment 1 -- 6,400 6,400 asset lives Big Stone II Unrecovered Project Costs – Minnesota 1 699 1,762 2,461 46 Debt Reacquisition Premiums 1 277 1,087 1,364 183 Deferred Income Taxes 1 -- 1,026 1,026 asset lives Minnesota Deferred Rate Case Expenses Subject to Recovery 1 725 -- 725 10 North Dakota Renewable Resource Rider Accrued Revenues 2 331 294 625 21 Big Stone II Unrecovered Project Costs – South Dakota 2 100 492 592 7 1 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up 2 170 232 402 30 North Dakota Transmission Cost Recovery Rider Accrued Revenues 2 284 -- 284 6 Minnesota Transmission Cost Recovery Rider Accrued Revenues 2 180 -- 180 1 2 South Dakota Transmission Cost Recovery Rider Accrued Revenues 2 71 -- 71 6 Minnesota Renewable Resource Rider Accrued Revenues 2 11 -- 11 3 Total Regulatory Assets $ 16,540 $ 127,479 $ 144,019 Regulatory Liabilities: Accumulated Reserve for Estimated Removal Costs – Net of Salvage $ -- $ 82,158 $ 82,158 asset lives North Dakota Transmission Cost Recovery Rider Accrued Refund 929 498 1,427 18 Deferred Income Taxes -- 753 753 asset lives Minnesota Environmental Cost Recovery Rider Accrued Refund 645 -- 645 12 Revenue for Rate Case Expenses Subject to Refund – Minnesota 563 -- 563 10 Re fundable Fuel Clause Adjustment Revenues 509 -- 509 12 South Dakota Environmental Cost Recovery Rider Accrued Refund 332 -- 332 12 Nort h Dakota Environmental Cost Recovery Rider Accrued Refund 167 -- 167 12 Sout h Dakota Transmission Cost Recovery Rider Accrued Refund 151 -- 151 12 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up 66 66 132 18 Other 6 86 92 198 Total Regulatory Liabilities $ 3,368 $ 83,561 $ 86,929 Net Regulatory Asset Position $ 13,172 $ 43,918 $ 57,090 1 Costs subject to recovery without a rate of return. 2 Amount eligible for recovery under an alternative revenue program which includes an incentive or rate of return. December 31, 2016 Remaining Recovery/ Refund Period (in thousands) Current Long-Term Total (months) Regulatory Assets: Prior Service Costs and Actuarial Losses on Pensions and Other Postretirement Benefits 1 $ 6,443 $ 108,267 $ 114,710 see below Conservation Improvement Program Costs and Incentives 2 4,836 5,158 9,994 21 Deferred Marked-to-Market Losses 1 4,063 6,467 10,530 48 Accumulated ARO Accretion/Depreciation Adjustment 1 -- 6,153 6,153 asset lives Big Stone II Unrecovered Project Costs – Minnesota 1 778 2,087 2,865 52 Recoverable Fuel and Purchased Power Costs 1 1,798 -- 1,798 12 Debt Reacquisition Premiums 1 325 1,214 1,539 189 Deferred Income Taxes 1 -- 1,014 1,014 asset lives Minnesota Deferred Rate Case Expenses Subject to Recovery 1 1,082 -- 1,082 12 North Dakota Renewable Resource Rider Accrued Revenues 2 1,319 482 1,801 15 Big Stone II Unrecovered Project Costs – South Dakota 2 100 543 643 77 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up 2 333 -- 333 12 North Dakota Transmission Cost Recovery Rider Accrued Revenues 2 -- 568 568 24 South Dakota Transmission Cost Recovery Rider Accrued Revenues 2 73 141 214 14 North Dakota Environmental Cost Recovery Rider Accrued Revenues 2 113 -- 113 12 Minnesota Renewable Resource Rider Accrued Revenues 2 34 -- 34 9 Total Regulatory Assets $ 21,297 $ 132,094 $ 153,391 Regulatory Liabilities: Accumulated Reserve for Estimated Removal Costs – Net of Salvage $ -- $ 80,404 $ 80,404 asset lives North Dakota Transmission Cost Recovery Rider Accrued Refund 1,381 782 2,163 24 Deferred Income Taxes -- 818 818 asset lives Minnesota Environmental Cost Recovery Rider Accrued Refund 139 -- 139 12 Revenue for Rate Case Expenses Subject to Refund – Minnesota 711 208 919 16 Minnesota Transmission Cost Recovery Rider Accrued Refund 757 -- 757 12 South Dakota Environmental Cost Recovery Rider Accrued Refund 285 -- 285 12 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up -- 132 132 24 Other 21 89 110 204 Total Regulatory Liabilities $ 3,294 $ 82,433 $ 85,727 Net Regulatory Asset Position $ 18,003 $ 49,661 $ 67,664 1 Costs subject to recovery without a rate of return. 2 Amount eligible for recovery under an alternative revenue program which includes an incentive or rate of return. The regulatory asset related to prior service costs and actuarial losses on pensions and other postretirement benefits represents benefit costs and actuarial losses subject to recovery through rates as they are expensed over the remaining service lives of active employees included in the plans. These unrecognized benefit costs and actuarial losses are required to be recognized as components of Accumulated Other Comprehensive Income in equity under ASC Topic 715, Compensation—Retirement Benefits Conservation Improvement Program Costs and Incentives represent mandated conservation expenditures and incentives recoverable through retail electric rates. All Deferred Marked-to-Market Losses recorded as of June 30, 2017 December 2020. The Accumulated Asset Retirement Obligation (ARO) Accretion/Depreciation Adjustment will accrete and be amortized over the lives of property with asset retirement obligations. Big Stone II Unrecovered Project Costs – Minnesota are the Minnesota share of generation and transmission plant-related costs incurred by OTP related to its participation in the abandoned Big Stone II project. Debt Reacquisition Premiums are being recovered from OTP customers over the remaining original lives of the reacquired debt issues, the longest of which is 18 3 The regulatory assets and liabilities related to Deferred Income Taxes result from changes in statutory tax rates accounted for in accordance with ASC Topic 740, Income Taxes Minnesota Deferred Rate Case Expenses Subject to Recovery relate to costs incurred in conjunction with OTP ’s 2016 24 April 2016. North Dakota Renewable Resource Rider Accrued Revenues relate to qualifying renewable resource costs incurred to serve North Dakota customers that have not June 30, 2017. Big Stone II Unrecovered Project Costs – South Dakota are the South Dakota share of generation and transmission plant-related costs incurred by OTP related to its participation in the abandoned Big Stone II project. MISO Schedule 26/26A 26/26A The North Dakota Transmission Cost Recovery Rider Accrued Revenues relate to revenues earned on qualifying transmission system facilities that have not June 30, 2017. The Minnesota Transmission Cost Recovery Rider Accrued Revenues relate to revenues earned on qualifying transmission system facilities that have not June 30, 2017. The South Dakota Transmission Cost Recovery Rider Accrued Revenues relate to revenues earned on qualifying transmission system facilities that have not June 30, 2017. Minnesota Renewable Resource Rider Accrued Revenues relate to revenues earned on qualifying renewable resource costs incurred to serve Minnesota customers that have not April 4, 2013 ’s request to set the rider rate to zero May 1, 2013 18 April 2016. The Accumulated Reserve for Estimated Removal Costs – Net of Salvage is reduced as actual removal costs, net of salvage revenues, are incurred. The North Dakota Transmission Cost Recovery Rider Accrued Refund relates to amounts collected for qualifying transmission system facilities and operating costs incurred to serve North Dakota customers that are refundable to North Dakota customers as of June 30, 2017. The Minnesota Environmental Cost Recovery Rider Accrued Refund relates to amounts collected on the Minnesota share of OTP ’s investment in the Big Stone Plant AQCS project that are refundable to Minnesota customers as of June 30, 2017. Revenue for Rate Case Expenses Subject to Refund – Minnesota relates to revenues collected under general rates to recover costs related to prior rate case proceedings in excess of the actual costs incurred, which are subject to refund over a 24 April 2016. The South Dakota Environmental Cost Recovery Rider Accrued Refund relates to amounts collected on the South Dakota share of OTP ’s investments in the Big Stone Plant AQCS and Hoot Lake Plant MATS projects that are refundable to South Dakota customers as of June 30, 2017. The North Dakota Environmental Cost Recovery Rider Accrued Refund relates to amounts collected on the North Dakota share of OTP’s investments in the Big Stone Plant AQCS and Hoot Lake Plant MATS projects that are refundable to North Dakota customers as of June 30, 2017. The South Dakota Transmission Cost Recovery Rider Accrued Refund relates to amounts collected for qualifying transmission system facilities and operating costs incurred to serve South Dakota customers that are refundable to South Dakota customers as of June 30, 2017. If for any reason OTP ceases to meet the criteria for application of guidance under ASC 980 no 980

Note 5 - Open Contract Position

Note 5 - Open Contract Positions Subject to Legally Enforceable Netting Arrangements	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Open Contract Positions Subject to Legally Enforceable Netting Arrangements [Text Block]	5. Open Contract Position s Subject to Legally Enforceable Netting Arrangements OTP has certain derivative contracts that are designated as normal purchases. Individual counterparty exposures for these contracts can be offset according to legally enforceable netting arrangements. The following table shows the current fair value of these forward contract positions subject to legally enforceable netting arrangements as of June 30, 2017 December 31, 2016: (in thousands) June 30 , 201 7 December 31, 201 6 Open Contract Gain Positions Subject to Legally Enforceable Netting Arrangements $ -- $ -- Open Contract Loss Positions Subject to Legally Enforceable Netting Arrangements (13,856 ) (17,382 ) Net Balance Subject to Legally Enforceable Netting Arrangements $ (13,856 ) $ (17,382 ) The following table provides a breakdown of OTP ’s credit risk standing on forward energy contracts in marked-to-market loss positions as of June 30, 2017 December 31, 2016: (in thousands) June 30 , 201 7 December 31, 201 6 Loss Contracts Covered by Deposited Funds or Letters of Credit $ -- $ -- Contracts Requiring Cash Deposits if OTP ’s Credit Falls Below Investment Grade 1 13,856 17,382 Total Loss Contracts based on Current Market Values $ 13,856 $ 17,382 1 Certain OTP derivative energy contracts contain provisions that require an investment grade credit rating from each of the major credit rating agencies on OTP’s debt. If OTP’s debt ratings were to fall below investment grade, the counterparties to these forward energy contracts could request the immediate deposit of cash to cover contracts in net liability positions. Contracts Requiring Cash Deposits if OTP ’s Credit Falls Below Investment Grade $ 13,856 $ 17,382 Offsetting Gains with Counterparties under Master Netting Agreements -- -- Reporting Date Deposit Requirement if Credit Risk Feature Triggered $ 13,856 $ 17,382

Note 6 - Reconciliation of Comm

Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Stockholders Equity and Earnings per Share [Text Block]	6. ’ Equity, Common Shares and Earnings Per Share Reconciliation of Common Shareholders ’ Equity (in thousands) Par Value, Common Shares Premium on Common Shares Retained Earnings Accumulated Other Comprehensive Income/(Loss) Total Common Equity Balance, December 31, 201 6 $ 196,741 $ 337,684 $ 139,479 $ (3,800 ) $ 670,104 Common Stock Issuances, Net of Expenses 1,273 3,613 4,886 Common Stock Retirements (239 ) (1,560 ) (1,799 ) Net Income 36,363 36,363 Other Comprehensive Income 214 214 Employee Stock Incentive Plan s Expense 1,920 1,920 Common Dividends ($0. 64 per share) (25,284 ) (25,284 ) Balance, June 30, 2017 $ 197,775 $ 341,657 $ 150,558 $ (3,586 ) $ 686,404 Shelf Registration and Common Share Distribution Agreement The Company ’s shelf registration statement filed with the Securities and Exchange Commission on May 11, 2015, may May 11, 2018. May 11, 2015, may $75 Common Shares Following is a reconciliation of the Company ’s common shares outstanding from December 31, 2016 June 30, 2017: Common Shares Outstanding December 31, 201 6 39,348,136 Issuances: Executive Stock Performance Awards (2014 shares earned) 89,291 Automatic Dividend Reinvestment and Share Purchase Plan: Dividends Reinvested 68,235 Cash Invested 27,348 Vesting of Restricted Stock Units 21,925 Restricted Stock Issued to Directors 17,600 Employee Stock Purchase Plan: Dividends Reinvested 9,566 Cash Invested 5,284 Employee Stock Ownership Plan 14,835 Directors Deferred Compensation 560 Retirements: Shares Withheld for Individual Income Tax Requirements (47,704 ) Common Shares Outstanding June 30, 2017 39,555,076 Earnings Per Share The numerator used in the calculation of both basic and diluted earnings per common share is net income for the three - and six June 30, 2017 2016. not Three Months ended June 30 Six Months ended June 30 201 7 201 6 201 7 201 6 Weighted Average Common Shares Outstanding – Basic 39,462,865 38,179,371 39,406,834 38,058,157 Plus Outstanding Share Awards net of Share Reductions for Unrecognized Stock-Based Compensation Expense and Excess Tax Benefits: Shares Expected to be Awarded for Stock Performance Awards Granted to Executive Officers based on Measurement Period-to-Date Performance 173,974 91,381 187,806 69,133 Underlying Shares Related to Nonvested Restricted Stock Units Granted to Employees 50,087 39,374 53,980 39,608 Nonvested Restricted Shares 12,719 7,862 19,894 12,819 Shares Expected to be Issued Under the Deferred Compensation Program for Directors 2,854 3,301 3,098 3,532 Total Dilutive Shares 239,634 141,918 264,778 125,092 Weighted Average Common Shares Outstanding – Diluted 39,702,499 38,321,289 39,671,612 38,183,249 The effect of dilutive shares on earnings per share for the three - and six June 30, 2017 2016, no $ 0.01

Note 7 - Share-based Payments

Note 7 - Share-based Payments	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	7. Stock Incentive Awards T he following stock incentive awards were granted under the 2014 six June 30, 2017: Award Grant-Date Shares/Units Granted Weighted Average Grant-Date Fair Value per Award Vesting Stock Performance Awards Granted to Executive Officers February 2, 2017 59,500 $ 31.00 December 31, 2019 Restricted Stock Units Granted to Executive Officers February 2, 2017 15,900 $ 37.65 25% per year through February 6, 2021 Restricted Stock Units Granted to Key Employees April 10, 2017 9,995 $ 32.78 100% on April 8, 20 21 Restricted Stock Granted to Nonemployee Directors April 10, 2017 17,600 $ 37.75 25% per year through April 8, 20 21 Under the performance share awards , the aggregate award for performance at target is 59,500 39,667 January 1, 2017 December 31, 2019, 20 January 1, 2017 20 January 1, 2020. 19,833 3 may zero 150% 89,250 no 62 718, The vesting of restricted stock units is accelerated in the event of a change in control, disability, death or retirement, subject to proration in certain cases. All restricted stock units granted to executive officers are eligible to receive dividend equivalent payments on all unvested awards over the awards respective vesting periods, subject to forfeiture under the terms of the restricted stock unit award agreements. The grant-date fair value of each restricted stock unit granted to an executive officer was the average of the high and low market price of one The grant-date fair value of each restricted stock unit granted to a key employee that is not one four The restricted shares granted to the Company ’s nonemployee directors are eligible for full dividend and voting rights. Restricted shares not one The end of the period over which compensation expense is recognized for the above share-based awards for the individual grantees is the shorter of the indicated vesting period for the respective awards or the date the grantee becomes eligible for retirement as defined in their award agreement. As of June 30, 2017 $5.5 2.4 Amounts of compensation expense recognized under the Company ’s six three six June 30, 2017 2016 Three Months Ended June 30, Six Months Ended June 30, (in thousands) 201 7 201 6 201 7 201 6 Stock Performance Awards Granted to Executive Officers $ 425 $ 304 $ 1,074 $ 841 Restricted Stock Units Granted to Executive Officers 104 64 368 309 Restricted Stock Granted to Executive Officers 16 22 38 51 Restricted Stock Granted to Nonemployee Directors 144 128 272 235 Restricted Stock Units Granted to Key Employees 81 81 168 145 Employee Stock Purchase Plan (15% discount) -- 44 -- 88 Totals $ 770 $ 643 $ 1,920 $ 1,669

Note 8 - Retained Earnings Rest

Note 8 - Retained Earnings Restriction	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Retained Earnings Restrictions [Text Block]	8. The Company is a holding company with no ’s shareholders is from dividends paid or distributions made by the Company’s subsidiaries. As a result of certain statutory limitations or regulatory or financing agreements, restrictions could occur on the amount of distributions allowed to be made by the Company’s subsidiaries. Both the Company and OTP debt agreements contain restrictions on the payment of cash dividends upon a default or event of default. An event of default would be considered to have occurred if the Company did not June 30, 2017 10 10 December 31, 2016 Under the Federal Power Act, a public utility may not 1 2 not 3 no The MPUC indirectly limits the amount of dividends OTP can pay to the Company by requiring an equity -to-total-capitalization ratio between 47.5% 58.1% 2016 August 2, 2016. June 30, 2017 52.4% $452,000,000. $1,123,168,000. On May 1, 2017 47.4% 58.0% 2017 not $1,178,024,000.

Note 9 - Commitments and Contin

Note 9 - Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	9. Construction and Other Purchase Commitments At December 31, 201 6 2019, $84.8 June 30, 2017 2019, $71.7 Electric Utility Capacity and Energy Requirements and Coal and Delivery Contracts OTP has commitments for the purchase of capacity and energy requirements under agreements extending into 2040. ’s current coal purchase agreements for Big Stone Plant and Coyote Station expire at the end of 2019 2040 , first 2017 a portion of the coal supply for Big Stone Plant contracted for delivery in 2016 2018 2019. 2018 2019 $3.0 January 1, 2016 December 31, 2023. no Operating Leases OTP has obligations to make future operating lease payments primarily related to land leases and coal rail-car leases. The Company ’s nonelectric companies have obligations to make future operating lease payments primarily related to leases of buildings and manufacturing equipment. Contingencies OTP had a $2.7 refund liability on its balance sheet as of December 31, 2016 February June 2017 first 15 2016 $2.7 December 31, 2016 $1.6 June 30, 2017. Together with as many as 200 ’s start on April 1, 2005 May 2, 2015. has set a briefing schedule with final briefs due in January 2018. not not Contingencies, by their nature, relate to uncertainties that require the Company ’s management to exercise judgment both in assessing the likelihood a liability has been incurred as well as in estimating the amount of potential loss. The most significant contingencies impacting the Company’s consolidated financial statements are those related to environmental remediation, risks associated with indemnification obligations under divestitures of discontinued operations and litigation matters. Should all of these known items result in liabilities being incurred, the loss could be as high as $1.0 In 2014 both proposed standards of performance for carbon dioxide ( CO2 CO2 111 October 23, 2015. February 9, 2016 September 27, 2016 first 2017. 13783, Promoting Energy Independence and Economic Growth CO2 Other The Company is a party to litigation and regulatory enforcement matters arising in the normal course of business. The Company regularly analyzes current information and, as necessary, provides accruals for liabilities that are probable of occurring and that can be reasonably estimated. The Company believes the effect on its consolidated results of operations, financial position and cash flows, if any, for the disposition of all matters pending as of June 30, 2017 not

Note 10 - Short-term and Long-t

Note 10 - Short-term and Long-term Borrowings	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Debt Disclosure [Text Block]	10. The following table presents the status of our lines of credit as of June 30, 2017 December 31, 2016: (in thousands) Line Limit In Use on June 30 , 2017 Restricted due to Outstanding Letters of Credit Available on June 30 , 2017 Available on December 31, 201 6 Otter Tail Corporation Credit Agreement $ 130,000 $ 117 $ -- $ 129,883 $ 130,000 OTP Credit Agreement 170,000 58,000 300 111,700 127,067 Total $ 300,000 $ 58,117 $ 300 $ 241,583 $ 257,067 Debt Retirements On February 5, 2016 $50 a Term Loan Agreement at an interest rate based on the 30 LIBOR 90 The Company repaid $35.0 $50 fourth 2016 $3.0 January 2017, $3.0 June 2017 $9.0 August 7, 2017. August 9, 2017 no The following tables provide a breakdown of the assignment of the Company ’s consolidated short-term and long-term debt outstanding as of June 30, 2017 December 31, 2016: June 30 , 201 7 (in thousands) OTP Otter Tail Corporation Otter Tail Corporation Consolidated Short-Term Debt $ 58,000 $ 117 $ 58,117 Long-Term Debt: Term Loan, LIBOR plus 0.90%, due February 5, 2018 $ 9,000 $ 9,000 3.55% Guaranteed Senior Notes, due December 15, 2026 80,000 80,000 Senior Unsecured Notes 5.95%, Series A, due August 20, 2017 $ 33,000 33,000 Senior Unsecured Notes 4.63%, due December 1, 2021 140,000 140,000 Senior Unsecured Notes 6.15%, Series B, due August 20, 2022 30,000 30,000 Senior Unsecured Notes 6.37%, Series C, due August 20, 2027 42,000 42,000 Senior Unsecured Notes 4.68%, Series A, due February 27, 2029 60,000 60,000 Senior Unsecured Notes 6.47%, Series D, due August 20, 2037 50,000 50,000 Senior Unsecured Notes 5.47%, Series B, due February 27, 2044 90,000 90,000 North Dakota Development Note, 3.95%, due April 1, 2018 67 67 P artnership in Assisting Community Expansion (PACE) Note, 2.54%, 761 761 Total $ 445,000 $ 89,828 $ 534,828 Less: Current Maturities net of Unamortized Debt Issuance Costs 32,993 9,207 42,200 Unamortized Long-Term Debt Issuance Costs 1,742 500 2,242 Total Long-Term Debt net of Unamortized Debt Issuance Costs $ 410,265 $ 80,121 $ 490,386 Total Short-Term and Long-Term Debt (with current maturities) $ 501,258 $ 89,445 $ 590,703 December 31, 2016 (in thousands) OTP Otter Tail Corporation Otter Tail Corporation Consolidated Short-Term Debt $ 42,883 $ -- $ 42,883 Long-Term Debt: Term Loan, LIBOR plus 0.90%, due February 5, 2018 $ 15,000 $ 15,000 3.55% Guaranteed Senior Notes, due December 15, 2026 80,000 80,000 Senior Unsecured Notes 5.95%, Series A, due August 20, 2017 $ 33,000 33,000 Senior Unsecured Notes 4.63%, due December 1, 2021 140,000 140,000 Senior Unsecured Notes 6.15%, Series B, due August 20, 2022 30,000 30,000 Senior Unsecured Notes 6.37%, Series C, due August 20, 2027 42,000 42,000 Senior Unsecured Notes 4.68%, Series A, due February 27, 2029 60,000 60,000 Senior Unsecured Notes 6.47%, Series D, due August 20, 2037 50,000 50,000 Senior Unsecured Notes 5.47%, Series B, due February 27, 2044 90,000 90,000 North Dakota Development Note, 3.95%, due April 1, 2018 106 106 PACE Note, 2.54%, due March 18, 2021 836 836 Total $ 445,000 $ 95,942 $ 540,942 Less: Current Maturities net of Unamortized Debt Issuance Costs 32,970 231 33,201 Unamortized Long-Term Debt Issuance Costs 1,861 539 2,400 Total Long-Term Debt net of Unamortized Debt Issuance Costs $ 410,169 $ 95,172 $ 505,341 Total Short-Term and Long-Term Debt (with current maturities) $ 486,022 $ 95,403 $ 581,425

Note 11 - Pension Plan and Othe

Note 11 - Pension Plan and Other Postretirement Benefits	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Pension and Other Postretirement Benefits Disclosure [Text Block]	1 1 . Pension Plan and Other Postretirement Benefits Pension Plan —Components of net periodic pension benefit cost of the Company's noncontributory funded pension plan are as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2017 2016 2017 201 6 Service Cost —Benefit Earned During the Period $ 1,407 $ 1,381 $ 2,814 $ 2,763 Interest Cost on Projected Benefit Obligation 3,536 3,521 7,070 7,043 Expected Return on Assets (4,807 ) (4,866 ) (9,614 ) (9,733 ) Amortization of Prior-Service Cost: From Regulatory Asset 29 47 59 94 From Other Comprehensive Income 1 1 1 2 2 Amortization of Net Actuarial Loss: From Regulatory Asset 1,272 1,227 2,545 2,454 From Other Comprehensive Income 1 32 32 63 63 Net Periodic Pension Cost $ 1,470 $ 1,343 $ 2,939 $ 2,686 1 Corporate cost included in Other Nonelectric Expenses. Cash flows —The Company currently is not not 2017. $10.0 January 2016. Executive Survivor and Supplemental Retirement Plan —Components of net periodic pension benefit cost of the Company’s unfunded, nonqualified benefit plan for executive officers and certain key management employees are as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2017 2016 2017 2016 Service Cost —Benefit Earned During the Period $ 72 $ 63 $ 145 $ 126 Interest Cost on Projected Benefit Obligation 421 417 843 834 Amortization of Prior-Service Cost: From Regulatory Asset 4 4 8 8 From Other Comprehensive Income 1 10 10 19 19 Amortization of Net Actuarial Loss: From Regulatory Asset 72 73 143 146 From Other Comprehensive Income 2 110 111 220 223 Net Periodic Pension Cost $ 689 $ 678 $ 1,378 $ 1,356 1 Amortization of Prior Service Costs from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $ 4 $ 4 $ 8 $ 8 Other Nonelectric Expenses 6 6 11 11 2 Amortization of Net Actuarial Loss from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $ 66 $ 68 $ 132 $ 136 Other Nonelectric Expenses 44 43 88 87 Postretirement Benefits —Components of net periodic postretirement benefit cost for health insurance and life insurance benefits for retired OTP and corporate employees, net of the effect of Medicare Part D Subsidy: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2017 2016 2017 201 6 Service Cost —Benefit Earned During the Period $ 356 $ 305 $ 712 $ 611 Interest Cost on Projected Benefit Obligation 678 542 1,356 1,083 Amortization of Prior-Service Cost: From Regulatory Asset -- 33 -- 66 From Other Comprehensive Income 1 -- 1 -- 2 Amortization of Net Actuarial Loss: From Regulatory Asset 233 -- 466 -- From Other Comprehensive Income 1 6 -- 12 -- Net Periodic Postretirement Benefit Cost $ 1,273 $ 881 $ 2,546 $ 1,762 Effect of Medicare Part D Subsidy $ (140 ) $ (258 ) $ (280 ) $ (515 ) 1 Corporate cost included in Other Nonelectric Expenses.

Note 12 - Fair Value of Financi

Note 12 - Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Fair Value Disclosures [Text Block]	1 2 . Fair Value of Financial Instruments The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate that value: Short-Term Debt —The carrying amount approximates fair value because the debt obligations are short-term and the balances outstanding as of June 30, 2017 December 31, 2016 LIBOR 1.75 1.25 Long -Term Debt including Current Maturities 2 820. June 30 , 2017 December 31, 20 16 (in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Short -Term Debt (58,117 ) (58,117 ) (42,883 ) (42,883 ) Long -Term Debt including Current Maturities (532,586 ) (588,251 ) (538,542 ) (583,835 )

Note 14 - Income Tax Expense -

Note 14 - Income Tax Expense - Continuing Operations	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Income Tax Disclosure [Text Block]	1 4 . Income Tax Expense – Continuing Operations The following table provides a reconciliation of income tax expense calculated at the net composite federal and state statutory rate on income from continuing operations before income taxes and income tax expense for continuing operations reported on the Company ’s consolidated statements of income: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 201 7 201 6 201 7 201 6 Income Before Income Taxes – Continuing Operations $ 22,614 $ 20,639 $ 48,506 $ 40,621 Tax Computed at Company ’s Net Composite Federal and State 8,819 8,049 18,917 15,842 Increases (Decreases) in Tax from: Federal Production Tax Credits (2,010 ) (1,885 ) (4,062 ) (3,571 ) Excess Tax Deduction – 2014 Performance Share Awards -- -- (697 ) -- Section 199 Domestic Production Activities Deduction (330 ) (94 ) (660 ) (198 ) Corporate -Owned Life Insurance (207 ) (480 ) (501 ) (572 ) North Dakota Wind Tax Credit Amortization – Net of Federal Taxes (213 ) (213 ) (425 ) (425 ) Employee Stock Ownership Plan Dividend Deduction (173 ) (157 ) (345 ) (315 ) Other Items – Net 11 (137 ) 33 (186 ) Income Tax Expense – Continuing Operations $ 5,897 $ 5,083 $ 12,260 $ 10,575 Effective Income Tax Rate – Continuing Operations 26.1 % 24.6 % 25.3 % 26.0 % The following table summarizes the activity related to our unrecognized tax benefits: (in thousands) 201 7 201 6 Balance on January 1 $ 891 $ 468 Increases Related to Tax Positions for Prior Years -- -- Increases Related to Tax Positions for Current Year 147 26 Uncertain Positions Resolved During Year -- -- Balance on June 30 $ 1,038 $ 494 The balance of unrecognized tax benefits as of June 30, 201 7 June 30, 2017 not 12 no June 30, 2017. The Company and its subsidiaries file a consolidated U.S. federal income tax return and various state income tax returns. As of June 30, 2017, no 2013

Note 16 - Discontinued Operatio

Note 16 - Discontinued Operations	6 Months Ended
	Jun. 30, 2017
Notes to Financial Statements
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	1 6 . Discontinued Operations Included in discontinued operations are activities related to the Company’s former wind tower manufacturing business and dock and boatlift company. Included in liabilities of discontinued operations are warranty reserves. Details regarding the warranty reserves follow: (in thousands) 201 7 201 6 Warranty Reserve Balance, January 1 $ 1,369 $ 2,103 Additional Provision for Warranties Made During the Year -- -- Settlements Made During the Year (51 ) -- Decrease in Warranty Estimates for Prior Years (200 ) (230 ) Warranty Reserve Balance, June 30 $ 1,118 $ 1,873 The warranty reserve balances as of June 30, 2017 one fifteen Expenses associated with remediation activities of these companies could be substantial. For wind towers, the potential exists for multiple claims based on one ’s consolidated net income and financial condition.

Significant Accounting Policies

Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition Due to the diverse business operations of the Company, revenue recognition depends on the product produced and sold or service performed. The Company recognizes revenue when the earnings process is complete, evidenced by an agreement with the customer, there has been delivery and acceptance, the price is fixed or determinable and collectability is reasonably assured. In cases where significant obligations remain after delivery, revenue recognition is deferred until such obligations are fulfilled. Provisions for sales returns and warranty costs are recorded at the time of the sale based on historical information and current trends. Gains and losses on forward energy contracts subject to regulatory treatment, if any, are deferred and recognized on a net basis in revenue in the period realized. For the Company ’s operating companies recognizing revenue on certain products when shipped, those operating companies have no
Agreements Subject to Legally Enforceable Netting Arrangements [Policy Text Block]	Agreements Subject to Legally Enforceable Netting Arrangements The Company does not
Fair Value of Financial Instruments, Policy [Policy Text Block]	Fair Value Measurements The Company follows Accounting Standards Codification (ASC) Topic 820, Fair Value Measurements and Disclosures 820 820 three Level 1 – Quoted prices are available in active markets for identical assets or liabilities as of the reported date. The types of assets and liabilities included in Level 1 Level 2 – Pricing inputs are other than quoted prices in active markets, but are either directly or indirectly observable as of the reported date. The types of assets and liabilities included in Level 2 Level 3 – Significant inputs to pricing have little or no 3 may The following tables present, for each of the hierarchy levels, the Company ’s assets and liabilities that are measured at fair value on a recurring basis as of June 30, 2017 December 31, 2016: June 30 , 201 7 (in thousands) Level 1 Level 2 Level 3 Assets: Investments: Equity Funds – Held by Captive Insurance Company $ 879 Corporate Debt Securities – Held by Captive Insurance Company $ 4,991 Government -Backed and Government-Sponsored ’ Debt Securities – Held by Captive Insurance Company 2,099 Other Assets: Money Market and Mutual Funds – Nonqualified Retirement Savings Plan 781 Total Assets $ 1,660 $ 7,090 December 31, 201 6 (in thousands) Level 1 Level 2 Level 3 Assets: Investments: Corporate Debt Securities – Held by Captive Insurance Company $ 5,280 Government -Backed and Government-Sponsored ’ Debt Securities – Held by Captive Insurance Company 2,945 Other Assets: Money Market and Mutual Funds – Nonqualified Retirement Savings Plan $ 849 Total Assets $ 849 $ 8,225 The valuation techniques and inputs used for the Level 2 Government-Backed and Government-Sponsored Enterprises ’ and Corporate Debt Securities Held by the Company’s Captive Insurance Company – Fair values are determined on the basis of valuations provided by a third may
Consolidation, Variable Interest Entity, Policy [Policy Text Block]	Coyote Station Lignite Supply Agreement – Variable Interest Entity —In October 2012 May 2016 December 2040. May 2016 December 2040 No none, none not If the LSA terminates prior to the expiration of its term or the production period terminates prior to December 31, 2040 ’s applicable lender) assume, all of CCMC’s obligations owed to CCMC’s lenders under its loans and leases. The Coyote Station owners have limited rights to assign their rights and obligations under the LSA without the consent of CCMC’s lenders during any period in which CCMC’s obligations to its lenders remain outstanding. In the event the contract is terminated because regulations or legislation render the burning of coal cost prohibitive and the assets worthless, OTP’s maximum exposure to loss as a result of its involvement with CCMC as of June 30, 2017 $58.9 35%
Inventory, Policy [Policy Text Block]	Inventories Inventories , valued at the lower of cost or net realizable value, consist of the following: June 30 , December 31, (in thousands) 201 7 201 6 Finished Goods $ 24,646 $ 27,755 Work in Process 13,977 11,754 Raw Material, Fuel and Supplies 48,644 44,231 Total Inventories $ 87,267 $ 83,740
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	Goodwill and Other Intangible Assets An assessment of the carrying amounts of goodwill of the Company ’s operating units as of December 31, 2016 not The following table indicates there were no first six 2017: (in thousands) Gross Balance December 31, 2016 Accumulated Impairments Balance (net of impairments) December 31, 2016 Adjustments to Goodwill in 201 7 Balance (net of impairments) June 30, 2017 Manufacturing $ 18,270 $ -- $ 18,270 $ -- $ 18,270 Plastics 19,302 -- 19,302 -- 19,302 Total $ 37,572 $ -- $ 37,572 $ -- $ 37,572 Intangible assets with finite lives are amortized over their estimated useful lives and reviewed for impairment in accordance with requirements under ASC Topic 360 10 35, Property, Plant, and Equipment—Overall—Subsequent Measurement The following table summarizes the components of the Company ’s intangible assets at June 30, 2017 December 31, 2016: June 30 , 2017 (in thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Remaining Amortization Periods (months) Amortizable Intangible Assets: Customer Relationships $ 22,491 $ 8,427 $ 14,064 30 - 218 Covenant not to Compete 590 361 229 14 Other 98 -- 98 36 Total $ 23,179 $ 8,788 $ 14,391 December 31, 2016 (in thousands) Amortizable Intangible Assets: Customer Relationships $ 22,491 $ 7,861 $ 14,630 36 - 224 Covenant not to Compete 590 262 328 20 Total $ 23,081 $ 8,123 $ 14,958 The amortization expense for these intangible assets was: Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Amortization Expense – Intangible Assets $ 333 $ 398 $ 665 $ 755 The estimated annual amortization expense for these intangible assets for the next five (in thousands) 2017 2018 2019 2020 2021 Estimated Amortization Expense – Intangible Assets $ 1,330 $ 1,264 $ 1,133 $ 1,099 $ 1,099
Cash Flow Supplemental [Policy Text Block]	Supplemental Disclosures of Cash Flow Information As of June 30, (in thousands) 201 7 201 6 Noncash Investing Activities: Transactions Related to Capital Additions not Settled in Cash $ 16,312 $ 17,837
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Standards Adopted Accounting Standards Update ( ASU ) 2015 11 July 2015 No. 2015 11, Inventory (Topic 330 December 15, 2016. 2015 11 first 2017. not
Schedule of Prospective Adoption of New Accounting Pronouncements [Policy Text Block]	New Accounting Standards Pending Adopt ion ASU 2014 09 —In May 2014 No. 2014 09, Revenue from Contracts with Customers (Topic 606 606 606 606 Amendments to the ASC in ASU 2014 09, December 15, 2017. not January 1, 2017. 1 2 one 3 application. The Company does not January 1, 2018. June 30, 2017 2014 09 not 2014 09. 2014 09 January 1, 2018, 2014 09 may ASU 2016 02 —In February 2016 No. 2016 02, Leases (Topic 842 2016 02 2016 02 842, 840 842 842 842 842 2016 02 December 15, 2018, 2016 02 2016 02, 2016 02 not 2016 02 2019. ASU 2017 04 —In January 2017 No. 2017 04, Intangibles—Goodwill and Other (Topic 350 2017 04 simplifies how an entity is required to test goodwill for impairment by eliminating Step 2 2 In computing the implied fair value of goodwill under Step 2, Under the amendments in ASU 2017 04, not The amendments in ASU 2017 04 no 2 2017 04 December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. ASU 2017 07 —In March 2017 No. 2017 07, Compensation—Retirement Benefits (Topic 715 2017 07 is intended to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. ASC Topic 715, Compensation—Retirement Benefits 715 , not not The amendments in ASU 2017 07 715 2017 07 2017 07 December 15, 2017, The majority of the Company ’s benefit costs to which the amendments in ASU 2017 07 2017 07 2017 07 may may 2017 07. not 2017 07 first 2018,

Note 1 - Summary of Significa23

Note 1 - Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	June 30 , 201 7 (in thousands) Level 1 Level 2 Level 3 Assets: Investments: Equity Funds – Held by Captive Insurance Company $ 879 Corporate Debt Securities – Held by Captive Insurance Company $ 4,991 Government -Backed and Government-Sponsored ’ Debt Securities – Held by Captive Insurance Company 2,099 Other Assets: Money Market and Mutual Funds – Nonqualified Retirement Savings Plan 781 Total Assets $ 1,660 $ 7,090 December 31, 201 6 (in thousands) Level 1 Level 2 Level 3 Assets: Investments: Corporate Debt Securities – Held by Captive Insurance Company $ 5,280 Government -Backed and Government-Sponsored ’ Debt Securities – Held by Captive Insurance Company 2,945 Other Assets: Money Market and Mutual Funds – Nonqualified Retirement Savings Plan $ 849 Total Assets $ 849 $ 8,225
Schedule of Inventory, Current [Table Text Block]	June 30 , December 31, (in thousands) 201 7 201 6 Finished Goods $ 24,646 $ 27,755 Work in Process 13,977 11,754 Raw Material, Fuel and Supplies 48,644 44,231 Total Inventories $ 87,267 $ 83,740
Schedule of Goodwill [Table Text Block]	(in thousands) Gross Balance December 31, 2016 Accumulated Impairments Balance (net of impairments) December 31, 2016 Adjustments to Goodwill in 201 7 Balance (net of impairments) June 30, 2017 Manufacturing $ 18,270 $ -- $ 18,270 $ -- $ 18,270 Plastics 19,302 -- 19,302 -- 19,302 Total $ 37,572 $ -- $ 37,572 $ -- $ 37,572
Schedule of Other Intangible Assets [Table Text Block]	June 30 , 2017 (in thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Remaining Amortization Periods (months) Amortizable Intangible Assets: Customer Relationships $ 22,491 $ 8,427 $ 14,064 30 - 218 Covenant not to Compete 590 361 229 14 Other 98 -- 98 36 Total $ 23,179 $ 8,788 $ 14,391 December 31, 2016 (in thousands) Amortizable Intangible Assets: Customer Relationships $ 22,491 $ 7,861 $ 14,630 36 - 224 Covenant not to Compete 590 262 328 20 Total $ 23,081 $ 8,123 $ 14,958
Finite-lived Intangible Assets Amortization Expense [Table Text Block]	Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Amortization Expense – Intangible Assets $ 333 $ 398 $ 665 $ 755
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	(in thousands) 2017 2018 2019 2020 2021 Estimated Amortization Expense – Intangible Assets $ 1,330 $ 1,264 $ 1,133 $ 1,099 $ 1,099
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	As of June 30, (in thousands) 201 7 201 6 Noncash Investing Activities: Transactions Related to Capital Additions not Settled in Cash $ 16,312 $ 17,837

Note 2 - Segment Information (T

Note 2 - Segment Information (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Segment Reporting Information, by Segment [Table Text Block]	Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 102,236 $ 97,925 $ 220,787 $ 210,919 Manufacturing 59,304 58,452 117,721 118,272 Plastics 50,551 47,112 87,708 80,549 Intersegment Eliminations (5 ) (7 ) (13 ) (16 ) Total $ 212,086 $ 203,482 $ 426,203 $ 409,724 Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 6,439 $ 6,156 $ 12,825 $ 12,440 Manufacturing 553 1,006 1,107 1,998 Plastics 173 279 326 523 Corporate and Intersegment Eliminations 362 535 731 1,009 Total $ 7,527 $ 7,976 $ 14,989 $ 15,970 Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 2,442 $ 1,920 $ 8,504 $ 6,532 Manufacturing 1,573 1,791 2,628 2,810 Plastics 2,858 2,262 4,248 3,629 Corporate (976 ) (890 ) (3,120 ) (2,396 ) Total $ 5,897 $ 5,083 $ 12,260 $ 10,575 Three Months Ended Six Months Ended June 30, June 30, (in thousands) 201 7 201 6 201 7 201 6 Electric $ 10,134 $ 9,148 $ 25,694 $ 21,686 Manufacturing 2,955 3,009 5,127 4,862 Plastics 4,637 3,485 7,074 5,637 Corporate (1,009 ) (86 ) (1,649 ) (2,139 ) Discontinued Operations 61 119 117 149 Total $ 16,778 $ 15,675 $ 36,363 $ 30,195 June 30 , December 31, (in thousands) 201 7 201 6 Electric $ 1,639,699 $ 1,622,231 Manufacturing 170,429 166,525 Plastics 94,900 84,592 Corporate 39,028 39,037 Total $ 1,944,056 $ 1,912,385

Note 3 - Rate and Regulatory 25

Note 3 - Rate and Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Interim Revenue [Table Text Block]	Interim Revenue (in thousands) April 16, 2016 through June 30, 2017 Billed and Accrued $ 18,956 Accrued Refund $ 7,449 Net Interim Revenue Earned and Reported $ 11,507 Interest on Refundable Amount $ 163 Refund Liability as of June 30, 2017 $ 7,612
Schedule of Information on Status of Updates for Previous Periods [Table Text Block]	Rate Rider R - Request Date A - Approval Date Effective Date Requested or Approved Annual Revenue ($000s) Rate Minnesota Conservation Improvement Program 2016 Incentive and Cost Recovery R – March 31, 2017 October 1, 201 7 $ 9,868 $0.00754/kwh 2015 Incentive and Cost Recovery A – July 19, 2016 October 1, 2016 $ 8,590 $0.00275/kwh 2014 Incentive and Cost Recovery A – July 10, 2015 October 1, 2015 $ 8,689 $0.00287/kwh Transmission Cost Recovery 201 6 Annual Update 1 A – July 5, 2016 September 1, 2016 $ 4,736 Various 2015 Annual Update A – March 9, 2016 April 1, 2016 $ 7,203 Various 2014 Annual Update A – February 18, 2015 March 1, 2015 $ 8,388 Various Environmental Cost Recovery 201 6 Annual Update 1 A – July 5, 2016 September 1, 2016 $ 11,884 6.927% of Rev 2015 Annual Update A – March 9, 2016 October 1, 2015 $ 12,104 7.006% of Rev North Dakota Renewable Resource Adjustment 201 6 Annual Update A – March 15, 2017 April 1, 2017 $ 9,156 7.00 5% of Rev 2015 Annual Update A – June 22, 2016 July 1, 2016 $ 9,262 7. 573% of Rev 201 4 Annual Update A – March 25, 2015 April 1, 2015 $ 5,441 4.069% of Rev Transmission Cost Recovery 201 6 Annual Update A – December 14, 2016 January 1, 2017 $ 6,916 Various 2015 Annual Update A – December 16, 2015 January 1, 2016 $ 9,985 Various Environmental Cost Recovery 201 7 Annual Update A – July 12, 2017 August 1, 2017 $ 9,917 7.633% of base 201 6 Annual Update A – June 22, 2016 July 1, 2016 $ 10,359 7. 904% of base 2015 Annual Update A – June 17, 2015 July 1, 2015 $ 12,249 9.193 % of base South Dakota Transmission Cost Recovery 201 6 Annual Update A – February 17, 2017 March 1, 2017 $ 2,053 Various 2015 Annual Update A – February 12, 2016 March 1, 2016 $ 1,895 Various 2014 Annual Update A – February 13, 2015 March 1, 2015 $ 1,538 Various Environmental Cost Recovery 201 6 Annual Update A – October 26, 2016 November 1, 2016 $ 2,238 $0.00536/kwh 201 5 Annual Update A – October 15, 2015 November 1, 2015 $ 2,728 $0.00643/kwh
Schedule of Revenues Recorded under Rate Riders [Table Text Block]	Three Months Ended June 30, Six Months Ended June 30, Rate Rider (in thousands) 2017 2016 2017 2016 Minnesota Conservation Improvement Program Costs and Incentives 1 $ 2,102 $ 2,209 $ 4,068 $ 4,715 Transmission Cost Recovery 1,273 1,133 3,443 3,409 Environmental Cost Recovery 2,812 3,153 5,636 6,235 North Dakota Renewable Resource Adjustment 1,839 1,922 3,609 3,981 Transmission Cost Recovery 1,384 1,969 3,895 4,205 Environmental Cost Recovery 2,388 2,771 4,876 5,582 South Dakota Transmission Cost Recovery 287 411 728 1,062 Environmental Cost Recovery 545 627 1,142 1,260 Conservation Improvement Program Costs and Incentives 176 124 416 283
Minnesota 2016 General Rate Case Information [Member]
Notes Tables
Public Utilities General Disclosures [Table Text Block]	($ in thousands) Initial Request February 16, 2016 Interim Rate s Authorized April 14, 2016 Projected Final Rates Revenue Increase – Annualized based on Test Year Data $ 19,296 $ 16,816 $ 12,100 Revenue Percent Increase 9.80 % 9.56 % 6.23 % Return on Rate Base 8.07 % 8.07 % 7.5056 % Jurisdictional Rate Base based on Test Year Data $ 483,000 $ 483,000 $ 471,000 Return on Equity 10.40 % 10.1 % 9.41 % Based on Equity to Total Capital of 52.50 % 52.50 % 52.50 % Debt to Total Capital 47.50 % 47.50 % 47.50 %

Note 4 - Regulatory Assets an26

Note 4 - Regulatory Assets and Liabilities (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Regulatory Assets and Liabilities [Table Text Block]	June 30 , 2017 Remaining Recovery/ Refund Period (in thousands) Current Long-Term Total (months) Regulatory Assets: Prior Service Costs and Actuarial Losses on Pensions and Other Postretirement Benefits 1 $ 6,444 $ 105,045 $ 111,489 see below Conservation Improvement Program Costs and Incentives 2 3,185 6,705 9,890 27 Deferred Marked-to-Market Losses 1 4,063 4,436 8,499 4 2 Accumulated ARO Accretion/Depreciation Adjustment 1 -- 6,400 6,400 asset lives Big Stone II Unrecovered Project Costs – Minnesota 1 699 1,762 2,461 46 Debt Reacquisition Premiums 1 277 1,087 1,364 183 Deferred Income Taxes 1 -- 1,026 1,026 asset lives Minnesota Deferred Rate Case Expenses Subject to Recovery 1 725 -- 725 10 North Dakota Renewable Resource Rider Accrued Revenues 2 331 294 625 21 Big Stone II Unrecovered Project Costs – South Dakota 2 100 492 592 7 1 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up 2 170 232 402 30 North Dakota Transmission Cost Recovery Rider Accrued Revenues 2 284 -- 284 6 Minnesota Transmission Cost Recovery Rider Accrued Revenues 2 180 -- 180 1 2 South Dakota Transmission Cost Recovery Rider Accrued Revenues 2 71 -- 71 6 Minnesota Renewable Resource Rider Accrued Revenues 2 11 -- 11 3 Total Regulatory Assets $ 16,540 $ 127,479 $ 144,019 Regulatory Liabilities: Accumulated Reserve for Estimated Removal Costs – Net of Salvage $ -- $ 82,158 $ 82,158 asset lives North Dakota Transmission Cost Recovery Rider Accrued Refund 929 498 1,427 18 Deferred Income Taxes -- 753 753 asset lives Minnesota Environmental Cost Recovery Rider Accrued Refund 645 -- 645 12 Revenue for Rate Case Expenses Subject to Refund – Minnesota 563 -- 563 10 Re fundable Fuel Clause Adjustment Revenues 509 -- 509 12 South Dakota Environmental Cost Recovery Rider Accrued Refund 332 -- 332 12 Nort h Dakota Environmental Cost Recovery Rider Accrued Refund 167 -- 167 12 Sout h Dakota Transmission Cost Recovery Rider Accrued Refund 151 -- 151 12 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up 66 66 132 18 Other 6 86 92 198 Total Regulatory Liabilities $ 3,368 $ 83,561 $ 86,929 Net Regulatory Asset Position $ 13,172 $ 43,918 $ 57,090 December 31, 2016 Remaining Recovery/ Refund Period (in thousands) Current Long-Term Total (months) Regulatory Assets: Prior Service Costs and Actuarial Losses on Pensions and Other Postretirement Benefits 1 $ 6,443 $ 108,267 $ 114,710 see below Conservation Improvement Program Costs and Incentives 2 4,836 5,158 9,994 21 Deferred Marked-to-Market Losses 1 4,063 6,467 10,530 48 Accumulated ARO Accretion/Depreciation Adjustment 1 -- 6,153 6,153 asset lives Big Stone II Unrecovered Project Costs – Minnesota 1 778 2,087 2,865 52 Recoverable Fuel and Purchased Power Costs 1 1,798 -- 1,798 12 Debt Reacquisition Premiums 1 325 1,214 1,539 189 Deferred Income Taxes 1 -- 1,014 1,014 asset lives Minnesota Deferred Rate Case Expenses Subject to Recovery 1 1,082 -- 1,082 12 North Dakota Renewable Resource Rider Accrued Revenues 2 1,319 482 1,801 15 Big Stone II Unrecovered Project Costs – South Dakota 2 100 543 643 77 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up 2 333 -- 333 12 North Dakota Transmission Cost Recovery Rider Accrued Revenues 2 -- 568 568 24 South Dakota Transmission Cost Recovery Rider Accrued Revenues 2 73 141 214 14 North Dakota Environmental Cost Recovery Rider Accrued Revenues 2 113 -- 113 12 Minnesota Renewable Resource Rider Accrued Revenues 2 34 -- 34 9 Total Regulatory Assets $ 21,297 $ 132,094 $ 153,391 Regulatory Liabilities: Accumulated Reserve for Estimated Removal Costs – Net of Salvage $ -- $ 80,404 $ 80,404 asset lives North Dakota Transmission Cost Recovery Rider Accrued Refund 1,381 782 2,163 24 Deferred Income Taxes -- 818 818 asset lives Minnesota Environmental Cost Recovery Rider Accrued Refund 139 -- 139 12 Revenue for Rate Case Expenses Subject to Refund – Minnesota 711 208 919 16 Minnesota Transmission Cost Recovery Rider Accrued Refund 757 -- 757 12 South Dakota Environmental Cost Recovery Rider Accrued Refund 285 -- 285 12 MISO Schedule 26/26A Transmission Cost Recovery Rider True-up -- 132 132 24 Other 21 89 110 204 Total Regulatory Liabilities $ 3,294 $ 82,433 $ 85,727 Net Regulatory Asset Position $ 18,003 $ 49,661 $ 67,664

Note 5 - Open Contract Positi27

Note 5 - Open Contract Positions Subject to Legally Enforceable Netting Arrangements (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Derivative Asset and Derivative Liability Balances Subject to Legally Enforceable Netting Arrangements [Table Text Block]	(in thousands) June 30 , 201 7 December 31, 201 6 Open Contract Gain Positions Subject to Legally Enforceable Netting Arrangements $ -- $ -- Open Contract Loss Positions Subject to Legally Enforceable Netting Arrangements (13,856 ) (17,382 ) Net Balance Subject to Legally Enforceable Netting Arrangements $ (13,856 ) $ (17,382 )
Schedule of Credit Derivatives Loss Position [Table Text Block]	(in thousands) June 30 , 201 7 December 31, 201 6 Loss Contracts Covered by Deposited Funds or Letters of Credit $ -- $ -- Contracts Requiring Cash Deposits if OTP ’s Credit Falls Below Investment Grade 1 13,856 17,382 Total Loss Contracts based on Current Market Values $ 13,856 $ 17,382 1 Certain OTP derivative energy contracts contain provisions that require an investment grade credit rating from each of the major credit rating agencies on OTP’s debt. If OTP’s debt ratings were to fall below investment grade, the counterparties to these forward energy contracts could request the immediate deposit of cash to cover contracts in net liability positions. Contracts Requiring Cash Deposits if OTP ’s Credit Falls Below Investment Grade $ 13,856 $ 17,382 Offsetting Gains with Counterparties under Master Netting Agreements -- -- Reporting Date Deposit Requirement if Credit Risk Feature Triggered $ 13,856 $ 17,382

Note 6 - Reconciliation of Co28

Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Stockholders Equity [Table Text Block]	(in thousands) Par Value, Common Shares Premium on Common Shares Retained Earnings Accumulated Other Comprehensive Income/(Loss) Total Common Equity Balance, December 31, 201 6 $ 196,741 $ 337,684 $ 139,479 $ (3,800 ) $ 670,104 Common Stock Issuances, Net of Expenses 1,273 3,613 4,886 Common Stock Retirements (239 ) (1,560 ) (1,799 ) Net Income 36,363 36,363 Other Comprehensive Income 214 214 Employee Stock Incentive Plan s Expense 1,920 1,920 Common Dividends ($0. 64 per share) (25,284 ) (25,284 ) Balance, June 30, 2017 $ 197,775 $ 341,657 $ 150,558 $ (3,586 ) $ 686,404
Schedule of Common Stock Outstanding Roll Forward [Table Text Block]	Common Shares Outstanding December 31, 201 6 39,348,136 Issuances: Executive Stock Performance Awards (2014 shares earned) 89,291 Automatic Dividend Reinvestment and Share Purchase Plan: Dividends Reinvested 68,235 Cash Invested 27,348 Vesting of Restricted Stock Units 21,925 Restricted Stock Issued to Directors 17,600 Employee Stock Purchase Plan: Dividends Reinvested 9,566 Cash Invested 5,284 Employee Stock Ownership Plan 14,835 Directors Deferred Compensation 560 Retirements: Shares Withheld for Individual Income Tax Requirements (47,704 ) Common Shares Outstanding June 30, 2017 39,555,076
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	Three Months ended June 30 Six Months ended June 30 201 7 201 6 201 7 201 6 Weighted Average Common Shares Outstanding – Basic 39,462,865 38,179,371 39,406,834 38,058,157 Plus Outstanding Share Awards net of Share Reductions for Unrecognized Stock-Based Compensation Expense and Excess Tax Benefits: Shares Expected to be Awarded for Stock Performance Awards Granted to Executive Officers based on Measurement Period-to-Date Performance 173,974 91,381 187,806 69,133 Underlying Shares Related to Nonvested Restricted Stock Units Granted to Employees 50,087 39,374 53,980 39,608 Nonvested Restricted Shares 12,719 7,862 19,894 12,819 Shares Expected to be Issued Under the Deferred Compensation Program for Directors 2,854 3,301 3,098 3,532 Total Dilutive Shares 239,634 141,918 264,778 125,092 Weighted Average Common Shares Outstanding – Diluted 39,702,499 38,321,289 39,671,612 38,183,249

Note 7 - Share-based Payments (

Note 7 - Share-based Payments (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	Award Grant-Date Shares/Units Granted Weighted Average Grant-Date Fair Value per Award Vesting Stock Performance Awards Granted to Executive Officers February 2, 2017 59,500 $ 31.00 December 31, 2019 Restricted Stock Units Granted to Executive Officers February 2, 2017 15,900 $ 37.65 25% per year through February 6, 2021 Restricted Stock Units Granted to Key Employees April 10, 2017 9,995 $ 32.78 100% on April 8, 20 21 Restricted Stock Granted to Nonemployee Directors April 10, 2017 17,600 $ 37.75 25% per year through April 8, 20 21
Share-based Compensation, Activity [Table Text Block]	Three Months Ended June 30, Six Months Ended June 30, (in thousands) 201 7 201 6 201 7 201 6 Stock Performance Awards Granted to Executive Officers $ 425 $ 304 $ 1,074 $ 841 Restricted Stock Units Granted to Executive Officers 104 64 368 309 Restricted Stock Granted to Executive Officers 16 22 38 51 Restricted Stock Granted to Nonemployee Directors 144 128 272 235 Restricted Stock Units Granted to Key Employees 81 81 168 145 Employee Stock Purchase Plan (15% discount) -- 44 -- 88 Totals $ 770 $ 643 $ 1,920 $ 1,669

Note 10 - Short-term and Long30

Note 10 - Short-term and Long-term Borrowings (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Line of Credit Facilities [Table Text Block]	(in thousands) Line Limit In Use on June 30 , 2017 Restricted due to Outstanding Letters of Credit Available on June 30 , 2017 Available on December 31, 201 6 Otter Tail Corporation Credit Agreement $ 130,000 $ 117 $ -- $ 129,883 $ 130,000 OTP Credit Agreement 170,000 58,000 300 111,700 127,067 Total $ 300,000 $ 58,117 $ 300 $ 241,583 $ 257,067
Schedule of Debt [Table Text Block]	June 30 , 201 7 (in thousands) OTP Otter Tail Corporation Otter Tail Corporation Consolidated Short-Term Debt $ 58,000 $ 117 $ 58,117 Long-Term Debt: Term Loan, LIBOR plus 0.90%, due February 5, 2018 $ 9,000 $ 9,000 3.55% Guaranteed Senior Notes, due December 15, 2026 80,000 80,000 Senior Unsecured Notes 5.95%, Series A, due August 20, 2017 $ 33,000 33,000 Senior Unsecured Notes 4.63%, due December 1, 2021 140,000 140,000 Senior Unsecured Notes 6.15%, Series B, due August 20, 2022 30,000 30,000 Senior Unsecured Notes 6.37%, Series C, due August 20, 2027 42,000 42,000 Senior Unsecured Notes 4.68%, Series A, due February 27, 2029 60,000 60,000 Senior Unsecured Notes 6.47%, Series D, due August 20, 2037 50,000 50,000 Senior Unsecured Notes 5.47%, Series B, due February 27, 2044 90,000 90,000 North Dakota Development Note, 3.95%, due April 1, 2018 67 67 P artnership in Assisting Community Expansion (PACE) Note, 2.54%, 761 761 Total $ 445,000 $ 89,828 $ 534,828 Less: Current Maturities net of Unamortized Debt Issuance Costs 32,993 9,207 42,200 Unamortized Long-Term Debt Issuance Costs 1,742 500 2,242 Total Long-Term Debt net of Unamortized Debt Issuance Costs $ 410,265 $ 80,121 $ 490,386 Total Short-Term and Long-Term Debt (with current maturities) $ 501,258 $ 89,445 $ 590,703 December 31, 2016 (in thousands) OTP Otter Tail Corporation Otter Tail Corporation Consolidated Short-Term Debt $ 42,883 $ -- $ 42,883 Long-Term Debt: Term Loan, LIBOR plus 0.90%, due February 5, 2018 $ 15,000 $ 15,000 3.55% Guaranteed Senior Notes, due December 15, 2026 80,000 80,000 Senior Unsecured Notes 5.95%, Series A, due August 20, 2017 $ 33,000 33,000 Senior Unsecured Notes 4.63%, due December 1, 2021 140,000 140,000 Senior Unsecured Notes 6.15%, Series B, due August 20, 2022 30,000 30,000 Senior Unsecured Notes 6.37%, Series C, due August 20, 2027 42,000 42,000 Senior Unsecured Notes 4.68%, Series A, due February 27, 2029 60,000 60,000 Senior Unsecured Notes 6.47%, Series D, due August 20, 2037 50,000 50,000 Senior Unsecured Notes 5.47%, Series B, due February 27, 2044 90,000 90,000 North Dakota Development Note, 3.95%, due April 1, 2018 106 106 PACE Note, 2.54%, due March 18, 2021 836 836 Total $ 445,000 $ 95,942 $ 540,942 Less: Current Maturities net of Unamortized Debt Issuance Costs 32,970 231 33,201 Unamortized Long-Term Debt Issuance Costs 1,861 539 2,400 Total Long-Term Debt net of Unamortized Debt Issuance Costs $ 410,169 $ 95,172 $ 505,341 Total Short-Term and Long-Term Debt (with current maturities) $ 486,022 $ 95,403 $ 581,425

Note 11 - Pension Plan and Ot31

Note 11 - Pension Plan and Other Postretirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Net Benefit Costs [Table Text Block]	Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2017 2016 2017 201 6 Service Cost —Benefit Earned During the Period $ 1,407 $ 1,381 $ 2,814 $ 2,763 Interest Cost on Projected Benefit Obligation 3,536 3,521 7,070 7,043 Expected Return on Assets (4,807 ) (4,866 ) (9,614 ) (9,733 ) Amortization of Prior-Service Cost: From Regulatory Asset 29 47 59 94 From Other Comprehensive Income 1 1 1 2 2 Amortization of Net Actuarial Loss: From Regulatory Asset 1,272 1,227 2,545 2,454 From Other Comprehensive Income 1 32 32 63 63 Net Periodic Pension Cost $ 1,470 $ 1,343 $ 2,939 $ 2,686 Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2017 2016 2017 2016 Service Cost —Benefit Earned During the Period $ 72 $ 63 $ 145 $ 126 Interest Cost on Projected Benefit Obligation 421 417 843 834 Amortization of Prior-Service Cost: From Regulatory Asset 4 4 8 8 From Other Comprehensive Income 1 10 10 19 19 Amortization of Net Actuarial Loss: From Regulatory Asset 72 73 143 146 From Other Comprehensive Income 2 110 111 220 223 Net Periodic Pension Cost $ 689 $ 678 $ 1,378 $ 1,356 1 Amortization of Prior Service Costs from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $ 4 $ 4 $ 8 $ 8 Other Nonelectric Expenses 6 6 11 11 2 Amortization of Net Actuarial Loss from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $ 66 $ 68 $ 132 $ 136 Other Nonelectric Expenses 44 43 88 87 Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2017 2016 2017 201 6 Service Cost —Benefit Earned During the Period $ 356 $ 305 $ 712 $ 611 Interest Cost on Projected Benefit Obligation 678 542 1,356 1,083 Amortization of Prior-Service Cost: From Regulatory Asset -- 33 -- 66 From Other Comprehensive Income 1 -- 1 -- 2 Amortization of Net Actuarial Loss: From Regulatory Asset 233 -- 466 -- From Other Comprehensive Income 1 6 -- 12 -- Net Periodic Postretirement Benefit Cost $ 1,273 $ 881 $ 2,546 $ 1,762 Effect of Medicare Part D Subsidy $ (140 ) $ (258 ) $ (280 ) $ (515 )

Note 12 - Fair Value of Finan32

Note 12 - Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Fair Value, by Balance Sheet Grouping [Table Text Block]	June 30 , 2017 December 31, 20 16 (in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Short -Term Debt (58,117 ) (58,117 ) (42,883 ) (42,883 ) Long -Term Debt including Current Maturities (532,586 ) (588,251 ) (538,542 ) (583,835 )

Note 14 - Income Tax Expense 33

Note 14 - Income Tax Expense - Continuing Operations (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Three Months Ended June 30, Six Months Ended June 30, (in thousands) 201 7 201 6 201 7 201 6 Income Before Income Taxes – Continuing Operations $ 22,614 $ 20,639 $ 48,506 $ 40,621 Tax Computed at Company ’s Net Composite Federal and State 8,819 8,049 18,917 15,842 Increases (Decreases) in Tax from: Federal Production Tax Credits (2,010 ) (1,885 ) (4,062 ) (3,571 ) Excess Tax Deduction – 2014 Performance Share Awards -- -- (697 ) -- Section 199 Domestic Production Activities Deduction (330 ) (94 ) (660 ) (198 ) Corporate -Owned Life Insurance (207 ) (480 ) (501 ) (572 ) North Dakota Wind Tax Credit Amortization – Net of Federal Taxes (213 ) (213 ) (425 ) (425 ) Employee Stock Ownership Plan Dividend Deduction (173 ) (157 ) (345 ) (315 ) Other Items – Net 11 (137 ) 33 (186 ) Income Tax Expense – Continuing Operations $ 5,897 $ 5,083 $ 12,260 $ 10,575 Effective Income Tax Rate – Continuing Operations 26.1 % 24.6 % 25.3 % 26.0 %
Summary of Income Tax Contingencies [Table Text Block]	(in thousands) 201 7 201 6 Balance on January 1 $ 891 $ 468 Increases Related to Tax Positions for Prior Years -- -- Increases Related to Tax Positions for Current Year 147 26 Uncertain Positions Resolved During Year -- -- Balance on June 30 $ 1,038 $ 494

Note 16 - Discontinued Operat34

Note 16 - Discontinued Operations (Tables)	6 Months Ended
	Jun. 30, 2017
Notes Tables
Schedule of Product Warranty Liability [Table Text Block]	(in thousands) 201 7 201 6 Warranty Reserve Balance, January 1 $ 1,369 $ 2,103 Additional Provision for Warranties Made During the Year -- -- Settlements Made During the Year (51 ) -- Decrease in Warranty Estimates for Prior Years (200 ) (230 ) Warranty Reserve Balance, June 30 $ 1,118 $ 1,873

Note 1 - Summary of Significa35

Note 1 - Summary of Significant Accounting Policies (Details Textual) - Coyote Creek Mining Company, L.L.C. (CCMC) [Member] - Otter Tail Power Company [Member] - Lignite Sales Agreement [Member] $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 58.9
Variable Interest Entity Reporting Entity Involvement, Maximum Loss Exposure, Percentage	35.00%

Note 1 - Summary of Significa36

Note 1 - Summary of Significant Accounting Policies - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Inputs, Level 1 [Member]
Total Assets	$ 1,660	$ 849
Fair Value, Inputs, Level 1 [Member] | Equity Funds [Member]
Investments	879
Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Investments
Fair Value, Inputs, Level 1 [Member] | Government-backed and Government-sponsored Enterprises' Debt Securities [Member]
Investments
Fair Value, Inputs, Level 1 [Member] | Money Market and Mutual Funds [Member]
Other Assets	781	849
Fair Value, Inputs, Level 2 [Member]
Total Assets	7,090	8,225
Fair Value, Inputs, Level 2 [Member] | Equity Funds [Member]
Investments
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Investments	4,991	5,280
Fair Value, Inputs, Level 2 [Member] | Government-backed and Government-sponsored Enterprises' Debt Securities [Member]
Investments	2,099	2,945
Fair Value, Inputs, Level 2 [Member] | Money Market and Mutual Funds [Member]
Other Assets

Note 1 - Summary of Significa37

Note 1 - Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Finished Goods	$ 24,646	$ 27,755
Work in Process	13,977	11,754
Raw Material, Fuel and Supplies	48,644	44,231
Total Inventories	$ 87,267	$ 83,740

Note 1 - Summary of Significa38

Note 1 - Summary of Significant Accounting Policies - Summary of Changes to Goodwill by Business Segment (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Accumulated Impairments
Adjustments to Goodwill
Balance	37,572	$ 37,572
Gross Balance		37,572
Manufacturing [Member]
Accumulated Impairments
Adjustments to Goodwill
Balance	18,270	18,270
Gross Balance		18,270
Plastics [Member]
Accumulated Impairments
Adjustments to Goodwill
Balance	$ 19,302	19,302
Gross Balance		$ 19,302

Note 1 - Summary of Significa39

Note 1 - Summary of Significant Accounting Policies - Components of Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Amortizable Intangible Assets:
Gross Carrying Amount	$ 23,179	$ 23,081
Accumulated Amortization	8,788	8,123
Net Carrying Amount	14,391	14,958
Customer Relationships [Member]
Amortizable Intangible Assets:
Gross Carrying Amount	22,491	22,491
Accumulated Amortization	8,427	7,861
Net Carrying Amount	$ 14,064	$ 14,630
Customer Relationships [Member] | Minimum [Member]
Amortizable Intangible Assets:
Remaining Amortization Periods (Month)	2 years 180 days	3 years
Customer Relationships [Member] | Maximum [Member]
Amortizable Intangible Assets:
Remaining Amortization Periods (Month)	18 years 60 days	18 years 240 days
Covenant Not to Compete [Member]
Amortizable Intangible Assets:
Gross Carrying Amount	$ 590	$ 590
Accumulated Amortization	361	262
Net Carrying Amount	$ 229	$ 328
Remaining Amortization Periods (Month)	1 year 60 days	1 year 240 days
Other Intangible Assets [Member]
Amortizable Intangible Assets:
Gross Carrying Amount	$ 98
Accumulated Amortization
Net Carrying Amount	$ 98
Remaining Amortization Periods (Month)	3 years

Note 1 - Summary of Significa40

Note 1 - Summary of Significant Accounting Policies - Amortization Expense for Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Amortization Expense – Intangible Assets	$ 333	$ 398	$ 665	$ 755

Note 1 - Summary of Significa41

Note 1 - Summary of Significant Accounting Policies - Estimated Amortization Expense for Intangible Assets (Details) $ in Thousands	Jun. 30, 2017USD ($)
2,017	$ 1,330
2,018	1,264
2,019	1,133
2,020	1,099
2,021	$ 1,099

Note 1 - Summary of Significa42

Note 1 - Summary of Significant Accounting Policies - Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Jun. 30, 2016
Transactions Related to Capital Additions not Settled in Cash	$ 16,312	$ 17,837

Note 2 - Segment Information (D

Note 2 - Segment Information (Details Textual)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Number of Reportable Segments			3
Operating Revenues [Member] | UNITED STATES
Concentration Risk, Percentage	98.30%	98.50%	98.30%	98.70%

Note 2 - Segment Information -

Note 2 - Segment Information - Information on Continuing Operations for Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Annual Revenue	$ 212,086	$ 203,482	$ 426,203	$ 409,724
Interest Charges	7,527	7,976	14,989	15,970
Income Tax Expense—Continuing Operations	5,897	5,083	12,260	10,575
Net Income	16,778	15,675	36,363	30,195
Assets	1,944,056		1,944,056		$ 1,912,385
Discontinued Operations [Member]
Net Income	61	119	117	149
Operating Segments [Member] | Electric [Member]
Annual Revenue	102,236	97,925	220,787	210,919
Interest Charges	6,439	6,156	12,825	12,440
Income Tax Expense—Continuing Operations	2,442	1,920	8,504	6,532
Net Income	10,134	9,148	25,694	21,686
Assets	1,639,699		1,639,699		1,622,231
Operating Segments [Member] | Manufacturing [Member]
Annual Revenue	59,304	58,452	117,721	118,272
Interest Charges	553	1,006	1,107	1,998
Income Tax Expense—Continuing Operations	1,573	1,791	2,628	2,810
Net Income	2,955	3,009	5,127	4,862
Assets	170,429		170,429		166,525
Operating Segments [Member] | Plastics [Member]
Annual Revenue	50,551	47,112	87,708	80,549
Interest Charges	173	279	326	523
Income Tax Expense—Continuing Operations	2,858	2,262	4,248	3,629
Net Income	4,637	3,485	7,074	5,637
Assets	94,900		94,900		84,592
Intersegment Eliminations [Member]
Annual Revenue	(5)	(7)	(13)	(16)
Corporate and Eliminations [Member]
Interest Charges	362	535	731	1,009
Corporate, Non-Segment [Member]
Income Tax Expense—Continuing Operations	(976)	(890)	(3,120)	(2,396)
Net Income	(1,009)	$ (86)	(1,649)	$ (2,139)
Assets	$ 39,028		$ 39,028		$ 39,037

Note 3 - Rate and Regulatory 45

Note 3 - Rate and Regulatory Matters (Details Textual)	Sep. 28, 2016	Feb. 12, 2015	Nov. 06, 2014	Nov. 12, 2013	Jun. 30, 2016	Dec. 22, 2015	Apr. 21, 2011USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)	May 25, 2016	Nov. 25, 2009USD ($)
Regulatory Liabilities								$ 86,929,000	$ 85,727,000
Otter Tail Power Company [Member] | Federal Energy Regulatory Commission [Member]
Current Return on Equity Used in Transmission Rates	10.32%			12.38%	9.70%	10.32%
Additional Incentive Basis Point			0.50%
Expected Percentage of Return on Equity	10.82%
Proposed Reduced Return on Equity Used in Transmission Rates		8.67%		9.15%
Regulatory Liabilities								$ 1,600,000	$ 2,700,000
Otter Tail Power Company [Member] | Minnesota Public Utilities Commission [Member] | Conservation Improvement Program [Member]
Utility Incentive Percentage in Next Rolling Twelve Months										13.50%
Utility Incentive Percentage in Next Rolling Year Two										12.00%
Utility Incentive Percentage in Next Rolling Year Three										10.00%
Assumed Savings of Utility										1.70%
Expected Rate of Financial Incentive Reduction										50.00%
Number of Customers								2
Otter Tail Power Company [Member] | Minnesota Public Utilities Commission [Member] | Conservation Improvement Program [Member] | Fiscal Year 2016 [Member]
Amount Of Financial Incentive Requested								$ 5,000,000
Otter Tail Power Company [Member] | Minnesota Public Utilities Commission [Member] | Conservation Improvement Program [Member] | Fiscal Year 2015 [Member]
Financial Incentive Request Approved								4,300,000
Otter Tail Power Company [Member] | Minnesota Public Utilities Commission [Member] | Conservation Improvement Program [Member] | Fiscal Year 2014 [Member]
Financial Incentive Request Approved								$ 3,000,000
Otter Tail Power Company [Member] | Minnesota Public Utilities Commission [Member] | The 2016 General Rate Case [Member] | Maximum [Member]
Public Utilities Approved Rate Rate of Return on Rate Base Percentage Decrease								8.61%
Public Utilities Return on Equity Percentage Decrease								10.74%
Otter Tail Power Company [Member] | Minnesota Public Utilities Commission [Member] | The 2016 General Rate Case [Member] | Minimum [Member]
Public Utilities Approved Rate Rate of Return on Rate Base Percentage Decrease								7.5056%
Public Utilities Return on Equity Percentage Decrease								9.41%
Otter Tail Power Company [Member] | North Dakota Public Service Commission [Member] | The 2010 General Rate Case [Member]
General Rate Revenue Increase Requested											$ 3,600,000
Percentage of Allowed Rate of Return on Rate Base											8.62%
Percentage of Allowed Rate of Return on Equity											10.75%
Percentage of Increase in Base Rate Revenue Requested											3.00%
Otter Tail Power Company [Member] | South Dakota Public Utilities Commission [Member] | The 2010 General Rate Case [Member]
Public Utilities General Rate Revenue Increase Approved							$ 643,000
Percentage of Increase in Base Rate Revenue Requested							2.32%
Public Utilities Allowed Rate of Return on Rate Base Subsequent to Approval of Increase in Base Rate							8.50%
Otter Tail Power Company [Member] | Big Stone South - Brookings MVP [Member]
Expanded Capacity of Projects								345
Extended Distance of Transmission Line								70
Current Projected Cost								$ 66,300,000
Percentage of Assets of Project								100.00%
Otter Tail Power Company [Member] | Big Stone South - Ellendale MVP [Member] | Federal Energy Regulatory Commission [Member]
Expanded Capacity of Projects								345
Extended Distance of Transmission Line								163
Current Projected Cost								$ 65,500,000
Percentage of Assets of Project								100.00%

Note 3 - Rate and Regulatory 46

Note 3 - Rate and Regulatory Matters - Summary of Interim Rate Information (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Apr. 14, 2016	Feb. 16, 2016
Revenue Increase – Annualized based on Test Year Data, initial request			$ 19,296
Revenue Increase – Annualized based on Test Year Data, interim rate		$ 16,816
Revenue Increase – Annualized based on Test Year Data, projected final rates	$ 12,100
Revenue Percent Increase, initial request			9.80%
Revenue Percent Increase, interim rate		9.56%
Revenue Percent Increase, projected final rates	6.23%
Return on Rate Base, initial request			8.07%
Return on Rate Base, interim rate		8.07%
Return on Rate Base, projected final rates	7.5056%
Jurisdictional Rate Base based on Test Year Data, initial request			$ 483,000
Jurisdictional Rate Base based on Test Year Data, interim rate		$ 483,000
Jurisdictional Rate Base based on Test Year Data, projected final rates	$ 471,000
Return on Equity, initial request			10.40%
Return on Equity, interim rate		10.10%
Return on Equity, projected final rates	9.41%
Based on Equity to Total Capital of, initial request			52.50%
Based on Equity to Total Capital of, interim rate		52.50%
Based on Equity to Total Capital of, projected final rates	52.50%
Debt to Total Capital, initial request			47.50%
Debt to Total Capital, interim rate		47.50%
Debt to Total Capital, projected final rates	47.50%

Note 3 - Rate and Regulatory 47

Note 3 - Rate and Regulatory Matters - Schedule of Interim Revenue (Details) $ in Thousands	15 Months Ended
	Jun. 30, 2017USD ($)
Billed and Accrued	$ 18,956
Accrued Refund	7,449
Net Interim Revenue Earned and Reported	11,507
Interest on Refundable Amount	163
Refund Liability as of June 30, 2017	$ 7,612

Note 3 - Rate and Regulatory 48

Note 3 - Rate and Regulatory Matters - Summary of Status of Updates for Previous Two Years for Various Rate Riders (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)kWh	Jun. 30, 2016USD ($)
Annual Revenue		$ 212,086	$ 203,482	$ 426,203	$ 409,724
Otter Tail Power Company [Member] | Minnesota [Member] | Conservation Improvement Program Costs and Incentives [Member]
Annual Revenue	[1]	2,102	2,209	4,068	4,715
Otter Tail Power Company [Member] | Minnesota [Member] | Conservation Improvement Program Costs and Incentives [Member] | The 2016 Incentive and Cost Recovery [Member]
Annual Revenue				$ 9,868
Rate (Kilowatt-Hour) | kWh				0.00754
R - Request Date				Mar. 31, 2017
Effective Date Requested or Approved				Oct. 1, 2017
Otter Tail Power Company [Member] | Minnesota [Member] | Conservation Improvement Program Costs and Incentives [Member] | The 2015 Incentive and Cost Recovery [Member]
Annual Revenue				$ 8,590
Rate (Kilowatt-Hour) | kWh				0.00275
A - Approval Date				Jul. 19, 2016
Effective Date Requested or Approved				Oct. 1, 2016
Otter Tail Power Company [Member] | Minnesota [Member] | Conservation Improvement Program Costs and Incentives [Member] | The 2014 Incentive and Cost Recovery [Member]
Annual Revenue				$ 8,689
Rate (Kilowatt-Hour) | kWh				0.00287
A - Approval Date				Jul. 10, 2015
Effective Date Requested or Approved				Oct. 1, 2015
Otter Tail Power Company [Member] | Minnesota [Member] | Transmission Cost Recovery Rider [Member]
Annual Revenue		1,273	1,133	$ 3,443	3,409
Otter Tail Power Company [Member] | Minnesota [Member] | Transmission Cost Recovery Rider [Member] | The 2016 Annual Update [Member]
Annual Revenue	[2]			$ 4,736
Rate	[2]			Various
A - Approval Date	[2]			Jul. 5, 2016
Effective Date Requested or Approved	[2]			Sep. 1, 2016
Otter Tail Power Company [Member] | Minnesota [Member] | Transmission Cost Recovery Rider [Member] | The 2015 Annual Update [Member]
Annual Revenue				$ 7,203
Rate				Various
A - Approval Date				Mar. 9, 2016
Effective Date Requested or Approved				Apr. 1, 2016
Otter Tail Power Company [Member] | Minnesota [Member] | Transmission Cost Recovery Rider [Member] | The 2014 Annual Update [Member]
Annual Revenue				$ 8,388
Rate				Various
A - Approval Date				Feb. 18, 2015
Effective Date Requested or Approved				Mar. 1, 2015
Otter Tail Power Company [Member] | Minnesota [Member] | Environmental Cost Recovery Rider [Member]
Annual Revenue		2,812	3,153	$ 5,636	6,235
Otter Tail Power Company [Member] | Minnesota [Member] | Environmental Cost Recovery Rider [Member] | The 2016 Annual Update [Member]
Annual Revenue	[2]			$ 11,884
Rate of revenue	[2]			6.927%
A - Approval Date	[2]			Jul. 5, 2016
Effective Date Requested or Approved	[2]			Sep. 1, 2016
Otter Tail Power Company [Member] | Minnesota [Member] | Environmental Cost Recovery Rider [Member] | The 2015 Annual Update [Member]
Annual Revenue				$ 12,104
Rate of revenue				7.006%
A - Approval Date				Mar. 9, 2016
Effective Date Requested or Approved				Oct. 1, 2015
Otter Tail Power Company [Member] | North Dakota [Member] | Transmission Cost Recovery Rider [Member]
Annual Revenue		1,384	1,969	$ 3,895	4,205
Otter Tail Power Company [Member] | North Dakota [Member] | Transmission Cost Recovery Rider [Member] | The 2016 Annual Update [Member]
Annual Revenue				$ 6,916
Rate				Various
A - Approval Date				Dec. 14, 2016
Effective Date Requested or Approved				Jan. 1, 2017
Otter Tail Power Company [Member] | North Dakota [Member] | Transmission Cost Recovery Rider [Member] | The 2015 Annual Update [Member]
Annual Revenue				$ 9,985
Rate				Various
A - Approval Date				Dec. 16, 2015
Effective Date Requested or Approved				Jan. 1, 2016
Otter Tail Power Company [Member] | North Dakota [Member] | Environmental Cost Recovery Rider [Member]
Annual Revenue		2,388	2,771	$ 4,876	5,582
Otter Tail Power Company [Member] | North Dakota [Member] | Environmental Cost Recovery Rider [Member] | The 2016 Annual Update [Member]
Annual Revenue				$ 10,359
Rate of base				7.904%
A - Approval Date				Jun. 22, 2016
Effective Date Requested or Approved				Jul. 1, 2016
Otter Tail Power Company [Member] | North Dakota [Member] | Environmental Cost Recovery Rider [Member] | The 2015 Annual Update [Member]
Annual Revenue				$ 12,249
Rate of base				9.193%
A - Approval Date				Jun. 17, 2015
Effective Date Requested or Approved				Jul. 1, 2015
Otter Tail Power Company [Member] | North Dakota [Member] | Environmental Cost Recovery Rider [Member] | The 2017 Annual Update [Member]
Annual Revenue				$ 9,917
Rate of base				7.633%
R - Request Date				Jul. 12, 2017
Effective Date Requested or Approved				Aug. 1, 2017
Otter Tail Power Company [Member] | North Dakota [Member] | Renewable Resource Adjustment [Member]
Annual Revenue		1,839	1,922	$ 3,609	3,981
Otter Tail Power Company [Member] | North Dakota [Member] | Renewable Resource Adjustment [Member] | The 2016 Annual Update [Member]
Annual Revenue				$ 9,156
Rate of revenue				7.005%
A - Approval Date				Mar. 15, 2017
Effective Date Requested or Approved				Apr. 1, 2017
Otter Tail Power Company [Member] | North Dakota [Member] | Renewable Resource Adjustment [Member] | The 2015 Annual Update [Member]
Annual Revenue				$ 9,262
Rate of revenue				7.573%
A - Approval Date				Jun. 22, 2016
Effective Date Requested or Approved				Jul. 1, 2016
Otter Tail Power Company [Member] | North Dakota [Member] | Renewable Resource Adjustment [Member] | The 2014 Annual Update [Member]
Annual Revenue				$ 5,441
Rate of revenue				4.069%
A - Approval Date				Mar. 25, 2015
Effective Date Requested or Approved				Apr. 1, 2015
Otter Tail Power Company [Member] | South Dakota [Member] | Conservation Improvement Program Costs and Incentives [Member]
Annual Revenue		176	124	$ 416	283
Otter Tail Power Company [Member] | South Dakota [Member] | Transmission Cost Recovery Rider [Member]
Annual Revenue		287	411	728	1,062
Otter Tail Power Company [Member] | South Dakota [Member] | Transmission Cost Recovery Rider [Member] | The 2016 Annual Update [Member]
Annual Revenue				$ 2,053
Rate				Various
A - Approval Date				Feb. 17, 2017
Effective Date Requested or Approved				Mar. 1, 2017
Otter Tail Power Company [Member] | South Dakota [Member] | Transmission Cost Recovery Rider [Member] | The 2015 Annual Update [Member]
Annual Revenue				$ 1,895
Rate				Various
A - Approval Date				Feb. 12, 2016
Effective Date Requested or Approved				Mar. 1, 2016
Otter Tail Power Company [Member] | South Dakota [Member] | Transmission Cost Recovery Rider [Member] | The 2014 Annual Update [Member]
Annual Revenue				$ 1,538
Rate				Various
A - Approval Date				Feb. 13, 2015
Effective Date Requested or Approved				Mar. 1, 2015
Otter Tail Power Company [Member] | South Dakota [Member] | Environmental Cost Recovery Rider [Member]
Annual Revenue		$ 545	$ 627	$ 1,142	$ 1,260
Otter Tail Power Company [Member] | South Dakota [Member] | Environmental Cost Recovery Rider [Member] | The 2016 Annual Update [Member]
Annual Revenue				$ 2,238
Rate (Kilowatt-Hour) | kWh				0.00536
A - Approval Date				Oct. 26, 2016
Effective Date Requested or Approved				Nov. 1, 2016
Otter Tail Power Company [Member] | South Dakota [Member] | Environmental Cost Recovery Rider [Member] | The 2015 Annual Update [Member]
Annual Revenue				$ 2,728
Rate (Kilowatt-Hour) | kWh				0.00643
A - Approval Date				Oct. 15, 2015
Effective Date Requested or Approved				Nov. 1, 2015
[1]	Includes MNCIP costs recovered in base rates.
[2]	Approved on a provisional basis and subject to change based on comments from the MNDOC.

Note 3 - Rate and Regulatory 49

Note 3 - Rate and Regulatory Matters - Summary of Revenues Recorded Under Rate Riders (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues recorded under rate riders		$ 212,086	$ 203,482	$ 426,203	$ 409,724
Otter Tail Power Company [Member] | Minnesota [Member] | Conservation Improvement Program Costs and Incentives [Member]
Revenues recorded under rate riders	[1]	2,102	2,209	4,068	4,715
Otter Tail Power Company [Member] | Minnesota [Member] | Transmission Cost Recovery Rider [Member]
Revenues recorded under rate riders		1,273	1,133	3,443	3,409
Otter Tail Power Company [Member] | Minnesota [Member] | Environmental Cost Recovery Rider [Member]
Revenues recorded under rate riders		2,812	3,153	5,636	6,235
Otter Tail Power Company [Member] | North Dakota [Member] | Transmission Cost Recovery Rider [Member]
Revenues recorded under rate riders		1,384	1,969	3,895	4,205
Otter Tail Power Company [Member] | North Dakota [Member] | Environmental Cost Recovery Rider [Member]
Revenues recorded under rate riders		2,388	2,771	4,876	5,582
Otter Tail Power Company [Member] | North Dakota [Member] | Renewable Resource Adjustment [Member]
Revenues recorded under rate riders		1,839	1,922	3,609	3,981
Otter Tail Power Company [Member] | South Dakota [Member] | Conservation Improvement Program Costs and Incentives [Member]
Revenues recorded under rate riders		176	124	416	283
Otter Tail Power Company [Member] | South Dakota [Member] | Transmission Cost Recovery Rider [Member]
Revenues recorded under rate riders		287	411	728	1,062
Otter Tail Power Company [Member] | South Dakota [Member] | Environmental Cost Recovery Rider [Member]
Revenues recorded under rate riders		$ 545	$ 627	$ 1,142	$ 1,260
[1]	Includes MNCIP costs recovered in base rates.

Note 4 - Regulatory Assets an50

Note 4 - Regulatory Assets and Liabilities (Details Textual)	6 Months Ended
	Jun. 30, 2017
Debt Reacquisition Premiums [Member]
Regulatory Noncurrent Asset Remaining Recovery Period	15 years 90 days

Note 4 - Regulatory Assets an51

Note 4 - Regulatory Assets and Liabilities - Amount of Regulatory Assets and Liabilities Recorded on Consolidated Balance Sheet (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2017	Dec. 31, 2016
Regulatory Assets - Remaining Recovery/Refund Period (Month)
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)
Regulatory Liabilities - Current		$ 3,368	$ 3,294
Regulatory Liabilities - Long -Term		83,561	82,433
Regulatory Liabilities		86,929	85,727
Net Regulatory Asset Position - Current		13,172	18,003
Net Regulatory Asset Position - Long-Term		43,918	49,661
Net Regulatory Asset Position		57,090	67,664
Regulatory Assets - Current		16,540	21,297
Regulatory Assets - Long -Term		127,479	132,094
Regulatory Assets - Total		$ 144,019	$ 153,391
Accumulated Reserve for Estimated Removal Costs - Net of Salvage [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period		asset lives	asset lives
Regulatory Liabilities - Current
Regulatory Liabilities - Long -Term		82,158	80,404
Regulatory Liabilities		$ 82,158	$ 80,404
North Dakota Transmission Cost Recovery Rider Accrued Refund [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		1 year 180 days	2 years
Regulatory Liabilities - Current		$ 929	$ 1,381
Regulatory Liabilities - Long -Term		498	782
Regulatory Liabilities		$ 1,427	$ 2,163
Deferred Income Taxes [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period		asset lives	asset lives
Regulatory Liabilities - Current
Regulatory Liabilities - Long -Term		753	818
Regulatory Liabilities		$ 753	$ 818
Minnesota Environmental Cost Recovery Rider Accrued Refund [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		1 year	1 year
Regulatory Liabilities - Current		$ 645	$ 139
Regulatory Liabilities - Long -Term
Regulatory Liabilities		$ 645	$ 139
Revenue for Rate Case Expenses Subject to Refund - Minnesota [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		300 days	1 year 120 days
Regulatory Liabilities - Current		$ 563	$ 711
Regulatory Liabilities - Long -Term			208
Regulatory Liabilities		$ 563	$ 919
Refundable Fuel Clause Adjustment Revenues [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		1 year
Regulatory Liabilities - Current		$ 509
Regulatory Liabilities - Long -Term
Regulatory Liabilities		$ 509
South Dakota Environmental Cost Recovery Rider Accrued Refund [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		1 year	1 year
Regulatory Liabilities - Current		$ 332	$ 285
Regulatory Liabilities - Long -Term
Regulatory Liabilities		$ 332	$ 285
Minnesota Transmission Cost Recovery Rider Accrued Refund [member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)			1 year
Regulatory Liabilities - Current			$ 757
Regulatory Liabilities - Long -Term
Regulatory Liabilities			$ 757
North Dakota Environmental Cost Recovery Rider Accrued Refund [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		1 year
Regulatory Liabilities - Current		$ 167
Regulatory Liabilities - Long -Term
Regulatory Liabilities		$ 167
South Dakota Transmission Cost Recovery Rider Accrued Refund [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		1 year
Regulatory Liabilities - Current		$ 151
Regulatory Liabilities - Long -Term
Regulatory Liabilities		$ 151
MISO Schedule 26/26A Transmission Cost Recovery Rider True-up [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		1 year 180 days	2 years
Regulatory Liabilities - Current		$ 66
Regulatory Liabilities - Long -Term		66	132
Regulatory Liabilities		$ 132	$ 132
Other [Member]
Regulatory Liabilities - Remaining Recovery/Refund Period (Month)		16 years 180 days	17 years
Regulatory Liabilities - Current		$ 6	$ 21
Regulatory Liabilities - Long -Term		86	89
Regulatory Liabilities		92	110
Prior Service Costs and Actuarial Losses on Pensions and Other Postretirement Benefits [Member]
Regulatory Assets - Current	[1]	6,444	6,443
Regulatory Assets - Long -Term	[1]	105,045	108,267
Regulatory Assets - Total	[1]	$ 111,489	$ 114,710
Regulatory Assets - Remaining Recovery/Refund Period	[1]	see below	see below
Conservation Improvement Program Costs and Incentives [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	2 years 90 days	1 year 270 days
Regulatory Assets - Current	[2]	$ 3,185	$ 4,836
Regulatory Assets - Long -Term	[2]	6,705	5,158
Regulatory Assets - Total	[2]	$ 9,890	$ 9,994
Deferred Marked-to-Market Losses [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[1]	3 years 180 days	4 years
Regulatory Assets - Current	[1]	$ 4,063	$ 4,063
Regulatory Assets - Long -Term	[1]	4,436	6,467
Regulatory Assets - Total	[1]	8,499	10,530
Accumulated ARO Accretion/Depreciation Adjustment [Member]
Regulatory Assets - Current	[1]
Regulatory Assets - Long -Term	[1]	6,400	6,153
Regulatory Assets - Total	[1]	$ 6,400	$ 6,153
Regulatory Assets - Remaining Recovery/Refund Period	[1]	asset lives	asset lives
Big Stone II Unrecovered Project Costs - Minnesota [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[1]	3 years 300 days	4 years 120 days
Regulatory Assets - Current	[1]	$ 699	$ 778
Regulatory Assets - Long -Term	[1]	1,762	2,087
Regulatory Assets - Total	[1]	$ 2,461	$ 2,865
Debt Reacquisition Premiums [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[1]	15 years 90 days	15 years 270 days
Regulatory Assets - Current	[1]	$ 277	$ 325
Regulatory Assets - Long -Term	[1]	1,087	1,214
Regulatory Assets - Total	[1]	1,364	$ 1,539
Recoverable Fuel and Purchased Power Costs [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[1]		1 year
Regulatory Assets - Current	[1]		$ 1,798
Regulatory Assets - Long -Term	[1]
Regulatory Assets - Total	[1]		1,798
Deferred Income Taxes [Member]
Regulatory Assets - Current	[1]
Regulatory Assets - Long -Term	[1]	1,026	1,014
Regulatory Assets - Total	[1]	$ 1,026	$ 1,014
Regulatory Assets - Remaining Recovery/Refund Period	[1]	asset lives	asset lives
Minnesota Deferred Rate Case Expenses Subject to Recovery [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[1]	300 days	1 year
Regulatory Assets - Current	[1]	$ 725	$ 1,082
Regulatory Assets - Long -Term	[1]
Regulatory Assets - Total	[1]	$ 725	$ 1,082
North Dakota Renewable Resource Rider Accrued Revenues [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	1 year 270 days	1 year 90 days
Regulatory Assets - Current	[2]	$ 331	$ 1,319
Regulatory Assets - Long -Term	[2]	294	482
Regulatory Assets - Total	[2]	$ 625	$ 1,801
Big Stone II Unrecovered Project Costs - South Dakota [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	5 years 330 days	6 years 150 days
Regulatory Assets - Current	[2]	$ 100	$ 100
Regulatory Assets - Long -Term	[2]	492	543
Regulatory Assets - Total	[2]	$ 592	$ 643
MISO Schedule 26/26A Transmission Cost Recovery Rider True-up [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	2 years 180 days	1 year
Regulatory Assets - Current	[2]	$ 170	$ 333
Regulatory Assets - Long -Term	[2]	232
Regulatory Assets - Total	[2]	$ 402	$ 333
North Dakota Transmission Cost Recovery Rider Accrued Revenues [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	180 days	2 years
Regulatory Assets - Current	[2]	$ 284
Regulatory Assets - Long -Term	[2]		568
Regulatory Assets - Total	[2]	$ 284	$ 568
Minnesota Transmission Cost Recovery Rider Accrued Revenues [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	1 year
Regulatory Assets - Current	[2]	$ 180
Regulatory Assets - Long -Term	[2]
Regulatory Assets - Total	[2]	$ 180
South Dakota Transmission Cost Recovery Rider Accrued Revenues [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	180 days	1 year 60 days
Regulatory Assets - Current	[2]	$ 71	$ 73
Regulatory Assets - Long -Term	[2]		141
Regulatory Assets - Total	[2]	$ 71	$ 214
Minnesota Renewable Resource Rider Accrued Revenues [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]	90 days	270 days
Regulatory Assets - Current	[2]	$ 11	$ 34
Regulatory Assets - Long -Term	[2]
Regulatory Assets - Total	[2]	$ 11	$ 34
North Dakota Environmental Cost Recovery Rider Accrued Refund [Member]
Regulatory Assets - Remaining Recovery/Refund Period (Month)	[2]		1 year
Regulatory Assets - Current	[2]		$ 113
Regulatory Assets - Long -Term	[2]
Regulatory Assets - Total	[2]		$ 113
[1]	Costs subject to recovery without a rate of return.
[2]	Amount eligible for recovery under an alternative revenue program which includes an incentive or rate of return.

Note 5 - Open Contract Positi52

Note 5 - Open Contract Positions Subject to Legally Enforceable Netting Arrangements - Amount of Derivative Asset and Derivative Liability Balances (Details) - Legally Enforceable Netting Arrangements [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Open Contract Gain Positions Subject to Legally Enforceable Netting Arrangements
Open Contract Loss Positions Subject to Legally Enforceable Netting Arrangements	(13,856)	(17,382)
Net Balance Subject to Legally Enforceable Netting Arrangements	$ (13,856)	$ (17,382)

Note 5 - Open Contract Positi53

Note 5 - Open Contract Positions Subject to Legally Enforceable Netting Arrangements - Breakdown of OTP's Credit Risk Standing (Details) - Otter Tail Power Company [Member] - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Loss Contracts Covered by Deposited Funds or Letters of Credit
Contracts Requiring Cash Deposits if OTP's Credit Falls Below Investment Grade	[1]	13,856	17,382
Total Loss Contracts based on Current Market Values		$ 13,856	$ 17,382
[1]	Certain OTP derivative energy contracts contain provisions that require an investment grade credit rating from each of the major credit rating agencies on OTP's debt. If OTP's debt ratings were to fall below investment grade, the counterparties to these forward energy contracts could request the immediate deposit of cash to cover contracts in net liability positions. Contracts Requiring Cash Deposits if OTP's Credit Falls Below Investment Grade $13,856 $17,382 Offsetting Gains with Counterparties under Master Netting Agreements -- --Reporting Date Deposit Requirement if Credit Risk Feature Triggered $13,856 $17,382

Note 5 - Open Contract Positi54

Note 5 - Open Contract Positions Subject to Legally Enforceable Netting Arrangements - Breakdown of OTP's Credit Risk Standing (Details) (Parentheticals) - Otter Tail Power Company [Member] - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Contracts Requiring Cash Deposits if OTP's Credit Falls Below Investment Grade	[1]	$ 13,856	$ 17,382
Offsetting Gains with Counterparties under Master Netting Agreements
Reporting Date Deposit Requirement if Credit Risk Feature Triggered		$ 13,856	$ 17,382
[1]	Certain OTP derivative energy contracts contain provisions that require an investment grade credit rating from each of the major credit rating agencies on OTP's debt. If OTP's debt ratings were to fall below investment grade, the counterparties to these forward energy contracts could request the immediate deposit of cash to cover contracts in net liability positions. Contracts Requiring Cash Deposits if OTP's Credit Falls Below Investment Grade $13,856 $17,382 Offsetting Gains with Counterparties under Master Netting Agreements -- --Reporting Date Deposit Requirement if Credit Risk Feature Triggered $13,856 $17,382

Note 6 - Reconciliation of Co55

Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share (Details Textual) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	May 11, 2015
Maximum per Share Differences Between Basic and Diluted Earnings per Share in Total or from Continuing or Discontinued Operations	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Distribution Agreement [Member]
Agreement to Sell Shares, Value					$ 75

Note 6 - Reconciliation of Co56

Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share - Schedule of Reconciliation of Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Balance			$ 670,104
Common Stock Issuances, Net of Expenses			4,886
Common Stock Retirements			(1,799)
Net Income	$ 16,778	$ 15,675	36,363	$ 30,195
Other Comprehensive Income			214
Employee Stock Incentive Plans Expense			1,920
Common Dividends ($0.64 per share)			(25,284)
Balance	686,404		686,404
Par Value, Common Shares [Member]
Balance			196,741
Common Stock Issuances, Net of Expenses			1,273
Common Stock Retirements			(239)
Net Income
Other Comprehensive Income
Employee Stock Incentive Plans Expense
Common Dividends ($0.64 per share)
Balance	197,775		197,775
Premium on Common Shares [Member]
Balance			337,684
Common Stock Issuances, Net of Expenses			3,613
Common Stock Retirements			(1,560)
Net Income
Other Comprehensive Income
Employee Stock Incentive Plans Expense			1,920
Common Dividends ($0.64 per share)
Balance	341,657		341,657
Retained Earnings [Member]
Balance			139,479
Common Stock Issuances, Net of Expenses
Common Stock Retirements
Net Income			36,363
Other Comprehensive Income
Employee Stock Incentive Plans Expense
Common Dividends ($0.64 per share)			(25,284)
Balance	150,558		150,558
Accumulated Other Comprehensive Income/(Loss) [Member]
Balance			(3,800)
Common Stock Issuances, Net of Expenses
Common Stock Retirements
Net Income
Other Comprehensive Income			214
Employee Stock Incentive Plans Expense
Common Dividends ($0.64 per share)
Balance	$ (3,586)		$ (3,586)

Note 6 - Reconciliation of Co57

Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share - Schedule of Reconciliation of Stockholders' Equity (Details) (Parentheticals) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Dividends Declared Per Common Share (in dollars per share)	$ 0.32	$ 0.3125	$ 0.64	$ 0.625

Note 6 - Reconciliation of Co58

Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share - Reconciliation of Company's Common Shares (Details)	6 Months Ended
	Jun. 30, 2017shares
Common Shares Outstanding, December 31, 2016 Balance (in shares)	39,348,136
Issuances:
Executive Stock Performance Awards (2014 shares earned) (in shares)	89,291
Automatic Dividend Reinvestment and Share Purchase Plan:
Dividends Reinvested (in shares)	68,235
Cash Invested (in shares)	27,348
Vesting of Restricted Stock Units (in shares)	21,925
Restricted Stock Issued to Directors (in shares)	17,600
Employee Stock Purchase Plan:
Dividends Reinvested (in shares)	9,566
Cash Invested (in shares)	5,284
Employee Stock Ownership Plan (in shares)	14,835
Directors Deferred Compensation (in shares)	560
Retirements:
Shares Withheld for Individual Income Tax Requirements (in shares)	(47,704)
Common Shares Outstanding, June 30, 2017 Balance (in shares)	39,555,076

Note 6 - Reconciliation of Co59

Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share - Reconciliation of Weighted Average Common Shares Outstanding (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Weighted Average Common Shares Outstanding – Basic (in shares)	39,462,865	38,179,371	39,406,834	38,058,157
Plus Outstanding Share Awards net of Share Reductions for Unrecognized Stock-Based Compensation Expense and Excess Tax Benefits:
Shares Expected to be Awarded for Stock Performance Awards Granted to Executive Officers based on Measurement Period-to-Date Performance (in shares)	173,974	91,381	187,806	69,133
Underlying Shares Related to Nonvested Restricted Stock Units Granted to Employees (in shares)	50,087	39,374	53,980	39,608
Nonvested Restricted Shares (in shares)	12,719	7,862	19,894	12,819
Shares Expected to be Issued Under the Deferred Compensation Program for Directors (in shares)	2,854	3,301	3,098	3,532
Total Dilutive Shares (in shares)	239,634	141,918	264,778	125,092
Weighted Average Common Shares Outstanding – Diluted (in shares)	39,702,499	38,321,289	39,671,612	38,183,249

Note 7 - Share-based Payments60

Note 7 - Share-based Payments (Details Textual) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)shares
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized | $	$ 5.5
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 146 days
Stock Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	59,500
Stock Performance Awards [Member] | Minimum [Member]
Percentage of Target Amount as Actual Payment	0.00%
Stock Performance Awards [Member] | Maximum [Member]
Percentage of Target Amount as Actual Payment	150.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	89,250
Stock Performance Awards [Member] | Executive Officer [Member]
Targeted Aggregate Common Shares Award Total Shareholder Return Component	39,667
Threshold Trading Days for Common Stock	20 days
Targeted Aggregate Common Shares Award Return on Equity Component	19,833
Period Specified for Average Adjusted Return	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	59,500

Note 7 - Share-based Payments -

Note 7 - Share-based Payments - Stock Incentive Awards to Executive Officers, Key Employees and Nonemployee Directors (Details)	6 Months Ended
	Jun. 30, 2017$ / sharesshares
Stock Performance Awards [Member] | Executive Officer [Member]
Shares/units granted, grant date	Feb. 2, 2017
Shares/units granted (in shares) | shares	59,500
Shares/units granted, weighted average grant-date fair value per award (in dollars per share) | $ / shares	$ 31
Shares/units granted, vesting date	Dec. 31, 2019
Restricted Stock Units (RSUs) [Member] | Executive Officer [Member]
Shares/units granted, grant date	Feb. 2, 2017
Shares/units granted (in shares) | shares	15,900
Shares/units granted, weighted average grant-date fair value per award (in dollars per share) | $ / shares	$ 37.65
Shares/units granted, vesting percentage	25.00%
Shares/units granted, vesting date	Feb. 6, 2021
Restricted Stock Units (RSUs) [Member] | Key Employees [Member]
Shares/units granted, grant date	Apr. 10, 2017
Shares/units granted (in shares) | shares	9,995
Shares/units granted, weighted average grant-date fair value per award (in dollars per share) | $ / shares	$ 32.78
Shares/units granted, vesting percentage	100.00%
Shares/units granted, vesting date	Apr. 8, 2021
Restricted Stock Units (RSUs) [Member] | Nonemployee Directors [Member]
Shares/units granted, grant date	Apr. 10, 2017
Shares/units granted (in shares) | shares	17,600
Shares/units granted, weighted average grant-date fair value per award (in dollars per share) | $ / shares	$ 37.75
Shares/units granted, vesting percentage	25.00%
Shares/units granted, vesting date	Apr. 8, 2021

Note 7 - Share-based Payments62

Note 7 - Share-based Payments - Amounts of Compensation Expense Recognized Under Stock-based Payment Programs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Stock compensation expense	$ 770	$ 643	$ 1,920	$ 1,669
Employee Stock Purchase Plan [Member]
Stock compensation expense		44		88
Stock Performance Awards [Member] | Executive Officer [Member]
Stock compensation expense	425	304	1,074	841
Restricted Stock Units (RSUs) [Member] | Executive Officer [Member]
Stock compensation expense	104	64	368	309
Restricted Stock Units (RSUs) [Member] | Key Employees [Member]
Stock compensation expense	81	81	168	145
Restricted Stock [Member] | Executive Officer [Member]
Stock compensation expense	16	22	38	51
Restricted Stock [Member] | Nonemployee Directors [Member]
Stock compensation expense	$ 144	$ 128	$ 272	$ 235

Note 7 - Share-based Payments63

Note 7 - Share-based Payments - Amounts of Compensation Expense Recognized Under Stock-based Payment Programs (Details) (Parentheticals)	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Employee Stock Purchase Plan [Member]
Stock compensation expense, discount rate	15.00%	15.00%

Note 8 - Retained Earnings Re64

Note 8 - Retained Earnings Restriction (Details Textual) - USD ($)	May 01, 2017	Jun. 30, 2017	Dec. 31, 2016
Capitalization, Long-term Debt and Equity		$ 1,176,790,000	$ 1,175,445,000
OTP [Member]
Net Assets Restricted from Distribution		$ 452,000,000
Equity to Total Capitalization Ratio		52.40%
OTP [Member] | Minimum [Member]
Equity to Total Capitalization Ratio	47.40%	47.50%
OTP [Member] | Maximum [Member]
Capitalization, Long-term Debt and Equity	$ 1,178,024,000	$ 1,123,168,000
Equity to Total Capitalization Ratio	58.00%	58.10%

Note 9 - Commitments and Cont65

Note 9 - Commitments and Contingencies (Details Textual) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)
Loss Contingency, Estimate of Possible Loss	$ 1
Otter Tail Power Company [Member]
Number of Utilities	200
Otter Tail Power Company [Member] | Federal Energy Regulatory Commission [Member]
Estimated Liability of Refund Obligation	$ 1.6	$ 2.7
Otter Tail Power Company [Member] | Construction Programs [Member]
Long-term Purchase Commitment, Amount	$ 71.7	$ 84.8
Otter Tail Power Company [Member] | Coal Purchase Commitments 1 [Member]
Contract Expiration Year	2,019
Otter Tail Power Company [Member] | Coal Purchase Commitments 2 [Member]
Contract Expiration Year	2,040
Otter Tail Power Company [Member] | Coal Purchase Commitments [Member]
Long-term Purchase Commitment, Amount	$ 3

Note 10 - Short-term and Long66

Note 10 - Short-term and Long-term Borrowings (Details Textual) - Term Loan Agreement [Member] - USD ($) $ in Thousands	Aug. 09, 2017	Aug. 07, 2017	Feb. 05, 2016	Jun. 30, 2017	Jan. 31, 2017	Dec. 31, 2016
Proceeds from Bank Debt			$ 50,000
Debt Instrument, Interest Rate, Basis for Effective Rate			30 day LIBOR plus 90
Debt Instrument, Description of Variable Rate Basis			LIBOR
Debt Instrument, Basis Spread on Variable Rate			0.90%
Repayments of Debt				$ 3,000	$ 3,000	$ 35,000
Subsequent Event [Member]
Proceeds from Bank Debt	$ 0
Repayments of Debt		$ 9,000

Note 10 - Short-term and Long67

Note 10 - Short-term and Long-term Borrowings - Status of Lines of Credit (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available	$ 241,583	$ 257,067
Line Limit	300,000
In Use	58,117
Restricted due to Outstanding Letters of Credit	300
Otter Tail Corporation Credit Agreement [Member]
Available	129,883	130,000
Line Limit	130,000
In Use	117
Restricted due to Outstanding Letters of Credit
OTP Credit Agreement [Member]
Available	111,700	$ 127,067
Line Limit	170,000
In Use	58,000
Restricted due to Outstanding Letters of Credit	$ 300

Note 10 - Short-term and Long68

Note 10 - Short-term and Long-term Borrowings - Breakdown of Assignment of Consolidated Short-term and Long-term Debt Outstanding (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Short-Term Debt	$ 58,117	$ 42,883
Long-Term Debt	534,828	540,942
Less: Current Maturities net of Unamortized Debt Issuance Costs	42,200	33,201
Unamortized Long-Term Debt Issuance Costs	2,242	2,400
Total Long-Term Debt net of Unamortized Debt Issuance Costs	490,386	505,341
Total Short-Term and Long-Term Debt (with current maturities)	590,703	581,425
Term Loan, LIBOR Plus 0.90%, Due February 5, 2018 [Member]
Long-Term Debt	9,000	15,000
The 3.55% Guaranteed Senior Notes, Due December 15, 2026 [Member]
Long-Term Debt	80,000	80,000
Senior Unsecured Notes 5.95%, Series A, Due August 20, 2017 [Member]
Long-Term Debt	33,000	33,000
Senior Unsecured Notes 4.63%, Due December 1, 2021 [Member]
Long-Term Debt	140,000	140,000
Senior Unsecured Notes 6.15%, Series B, Due August 20, 2022 [Member]
Long-Term Debt	30,000	30,000
Senior Unsecured Notes 6.37%, Series C, Due August 20, 2027 [member]
Long-Term Debt	42,000	42,000
Senior Unsecured Notes 4.68%, Series A, Due February 27, 2029 [Member]
Long-Term Debt	60,000	60,000
Senior Unsecured Notes 6.47%, Series D, Due August 20, 2037 [Member]
Long-Term Debt	50,000	50,000
Senior Unsecured Notes 5.47%, Series B, Due February 27, 2044 [Member]
Long-Term Debt	90,000	90,000
North Dakota Development Note, 3.95%, Due April 1, 2018 [member]
Long-Term Debt	67	106
Partnership in Assisting Community Expansion (PACE) Note, 2.54%, due March 18, 2021 [Member]
Long-Term Debt	761	836
OTP [Member]
Short-Term Debt	58,000	42,883
Long-Term Debt	445,000	445,000
Less: Current Maturities net of Unamortized Debt Issuance Costs	32,993	32,970
Unamortized Long-Term Debt Issuance Costs	1,742	1,861
Total Long-Term Debt net of Unamortized Debt Issuance Costs	410,265	410,169
Total Short-Term and Long-Term Debt (with current maturities)	501,258	486,022
OTP [Member] | Senior Unsecured Notes 5.95%, Series A, Due August 20, 2017 [Member]
Long-Term Debt	33,000	33,000
OTP [Member] | Senior Unsecured Notes 4.63%, Due December 1, 2021 [Member]
Long-Term Debt	140,000	140,000
OTP [Member] | Senior Unsecured Notes 6.15%, Series B, Due August 20, 2022 [Member]
Long-Term Debt	30,000	30,000
OTP [Member] | Senior Unsecured Notes 6.37%, Series C, Due August 20, 2027 [member]
Long-Term Debt	42,000	42,000
OTP [Member] | Senior Unsecured Notes 4.68%, Series A, Due February 27, 2029 [Member]
Long-Term Debt	60,000	60,000
OTP [Member] | Senior Unsecured Notes 6.47%, Series D, Due August 20, 2037 [Member]
Long-Term Debt	50,000	50,000
OTP [Member] | Senior Unsecured Notes 5.47%, Series B, Due February 27, 2044 [Member]
Long-Term Debt	90,000	90,000
Otter Tail Corporation [Member]
Short-Term Debt	117
Long-Term Debt	89,828	95,942
Less: Current Maturities net of Unamortized Debt Issuance Costs	9,207	231
Unamortized Long-Term Debt Issuance Costs	500	539
Total Long-Term Debt net of Unamortized Debt Issuance Costs	80,121	95,172
Total Short-Term and Long-Term Debt (with current maturities)	89,445	95,403
Otter Tail Corporation [Member] | Term Loan, LIBOR Plus 0.90%, Due February 5, 2018 [Member]
Long-Term Debt	9,000	15,000
Otter Tail Corporation [Member] | The 3.55% Guaranteed Senior Notes, Due December 15, 2026 [Member]
Long-Term Debt	80,000	80,000
Otter Tail Corporation [Member] | North Dakota Development Note, 3.95%, Due April 1, 2018 [member]
Long-Term Debt	67	106
Otter Tail Corporation [Member] | Partnership in Assisting Community Expansion (PACE) Note, 2.54%, due March 18, 2021 [Member]
Long-Term Debt	$ 761	$ 836

Note 10 - Short-term and Long69

Note 10 - Short-term and Long-term Borrowings - Breakdown of Assignment of Consolidated Short-term and Long-term Debt Outstanding (Details) (Parentheticals)	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Term Loan, LIBOR Plus 0.90%, Due February 5, 2018 [Member]
Long-Term Debt, Interest Rate	0.90%	0.90%
Long-Term Debt, Due Date	Feb. 5, 2018	Feb. 5, 2018
The 3.55% Guaranteed Senior Notes, Due December 15, 2026 [Member]
Long-Term Debt, Interest Rate	3.55%	3.55%
Long-Term Debt, Due Date	Dec. 15, 2026	Dec. 15, 2026
Senior Unsecured Notes 5.95%, Series A, Due August 20, 2017 [Member]
Long-Term Debt, Interest Rate	5.95%	5.95%
Long-Term Debt, Due Date	Aug. 20, 2017	Aug. 20, 2017
Senior Unsecured Notes 4.63%, Due December 1, 2021 [Member]
Long-Term Debt, Interest Rate	4.63%	4.63%
Long-Term Debt, Due Date	Dec. 1, 2021	Dec. 1, 2021
Senior Unsecured Notes 6.15%, Series B, Due August 20, 2022 [Member]
Long-Term Debt, Interest Rate	6.15%	6.15%
Long-Term Debt, Due Date	Aug. 20, 2022	Aug. 20, 2022
Senior Unsecured Notes 6.37%, Series C, Due August 20, 2027 [member]
Long-Term Debt, Interest Rate	6.37%	6.37%
Long-Term Debt, Due Date	Aug. 20, 2027	Aug. 20, 2027
Senior Unsecured Notes 4.68%, Series A, Due February 27, 2029 [Member]
Long-Term Debt, Interest Rate	4.68%	4.68%
Long-Term Debt, Due Date	Feb. 27, 2029	Feb. 27, 2029
Senior Unsecured Notes 6.47%, Series D, Due August 20, 2037 [Member]
Long-Term Debt, Interest Rate	6.47%	6.47%
Long-Term Debt, Due Date	Aug. 20, 2037	Aug. 20, 2037
Senior Unsecured Notes 5.47%, Series B, Due February 27, 2044 [Member]
Long-Term Debt, Interest Rate	5.47%	5.47%
Long-Term Debt, Due Date	Feb. 27, 2044	Feb. 27, 2044
North Dakota Development Note, 3.95%, Due April 1, 2018 [member]
Long-Term Debt, Interest Rate	3.95%	3.95%
Long-Term Debt, Due Date	Apr. 1, 2018	Apr. 1, 2018
Partnership in Assisting Community Expansion (PACE) Note, 2.54%, due March 18, 2021 [Member]
Long-Term Debt, Interest Rate	2.54%	2.54%
Long-Term Debt, Due Date	Mar. 18, 2021	Mar. 18, 2021

Note 11 - Pension Plan and Ot70

Note 11 - Pension Plan and Other Postretirement Benefits (Details Textual)	1 Months Ended
	Jan. 31, 2016USD ($)
Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 10,000,000

Note 11 - Pension Plan and Ot71

Note 11 - Pension Plan and Other Postretirement Benefits - Components of Net Periodic Pension Benefit Cost (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plan [Member]
Amortization of Net Actuarial Loss:
From Regulatory Asset		$ 1,272	$ 1,227	$ 2,545	$ 2,454
From Other Comprehensive Income	[1]	32	32	63	63
Net Periodic Pension Cost		1,470	1,343	2,939	2,686
Service Cost—Benefit Earned During the Period		1,407	1,381	2,814	2,763
Interest Cost on Projected Benefit Obligation		3,536	3,521	7,070	7,043
Expected Return on Assets		(4,807)	(4,866)	(9,614)	(9,733)
Amortization of Prior-Service Cost:
From Regulatory Asset		29	47	59	94
From Other Comprehensive Income	[1]	1	1	2	2
Executive Survivor and Supplemental Retirement Plan [Member]
Amortization of Net Actuarial Loss:
From Regulatory Asset		72	73	143	146
From Other Comprehensive Income	[2]	110	111	220	223
Net Periodic Pension Cost		689	678	1,378	1,356
Service Cost—Benefit Earned During the Period		72	63	145	126
Interest Cost on Projected Benefit Obligation		421	417	843	834
Amortization of Prior-Service Cost:
From Regulatory Asset		4	4	8	8
From Other Comprehensive Income	[3]	10	10	19	19
Postretirement Benefits [Member]
Amortization of Net Actuarial Loss:
From Regulatory Asset		233		466
From Other Comprehensive Income	[1]	6		12
Net Periodic Pension Cost		1,273	881	2,546	1,762
Service Cost—Benefit Earned During the Period		356	305	712	611
Interest Cost on Projected Benefit Obligation		678	542	1,356	1,083
Amortization of Prior-Service Cost:
From Regulatory Asset			33		66
From Other Comprehensive Income	[1]		1		2
Effect of Medicare Part D Subsidy		$ (140)	$ (258)	$ (280)	$ (515)
[1]	Corporate cost included in Other Nonelectric Expenses.
[2]	Amortization of Net Actuarial Loss from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $66 $68 $132 $136 Other Nonelectric Expenses 44 43 88 87
[3]	Amortization of Prior Service Costs from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $4 $4 $8 $8 Other Nonelectric Expenses 6 6 11 11

Note 11 - Pension Plan and Ot72

Note 11 - Pension Plan and Other Postretirement Benefits - Components of Net Periodic Pension Benefit Cost (Details) (Parentheticals) - Executive Survivor and Supplemental Retirement Plan [Member] - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Amortization of Prior Service Costs from Other Comprehensive Income Charged to:	[1]	$ 10	$ 10	$ 19	$ 19
Amortization of Net Actuarial Loss from Other Comprehensive Income Charge to:	[2]	110	111	220	223
Electric Operation and Maintenance Expenses [Member]
Amortization of Prior Service Costs from Other Comprehensive Income Charged to:		4	4	8	8
Amortization of Net Actuarial Loss from Other Comprehensive Income Charge to:		66	68	132	136
Other Nonelectric Expenses [member]
Amortization of Prior Service Costs from Other Comprehensive Income Charged to:		6	6	11	11
Amortization of Net Actuarial Loss from Other Comprehensive Income Charge to:		$ 44	$ 43	$ 88	$ 87
[1]	Amortization of Prior Service Costs from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $4 $4 $8 $8 Other Nonelectric Expenses 6 6 11 11
[2]	Amortization of Net Actuarial Loss from Other Comprehensive Income Charged to: Electric Operation and Maintenance Expenses $66 $68 $132 $136 Other Nonelectric Expenses 44 43 88 87

Note 12 - Fair Value of Finan73

Note 12 - Fair Value of Financial Instruments (Details Textual) - London Interbank Offered Rate (LIBOR) [Member]	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Otter Tail Corporation Credit Agreement [Member]
Debt Instrument, Description of Variable Rate Basis	LIBOR	LIBOR
Debt Instrument, Basis Spread on Variable Rate	1.75%	1.75%
OTP Credit Agreement [Member]
Debt Instrument, Description of Variable Rate Basis	LIBOR	LIBOR
Debt Instrument, Basis Spread on Variable Rate	1.25%	1.25%

Note 12 - Fair Value of Finan74

Note 12 - Fair Value of Financial Instruments - Summary of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Reported Value Measurement [Member]
Short-Term Debt	$ (58,117)	$ (42,883)
Long-Term Debt including Current Maturities	(532,586)	(538,542)
Estimate of Fair Value Measurement [Member]
Short-Term Debt	(58,117)	(42,883)
Long-Term Debt including Current Maturities	$ (588,251)	$ (583,835)

Note 14 - Income Tax Expense 75

Note 14 - Income Tax Expense - Continuing Operations - Effective Income Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Before Income Taxes – Continuing Operations	$ 22,614	$ 20,639	$ 48,506	$ 40,621
Tax Computed at Company’s Net Composite Federal and State Statutory Rate (39%)	8,819	8,049	18,917	15,842
Increases (Decreases) in Tax from:
Federal Production Tax Credits	(2,010)	(1,885)	(4,062)	(3,571)
Excess Tax Deduction – 2014 Performance Share Awards			(697)
Section 199 Domestic Production Activities Deduction	(330)	(94)	(660)	(198)
Corporate-Owned Life Insurance	(207)	(480)	(501)	(572)
North Dakota Wind Tax Credit Amortization – Net of Federal Taxes	(213)	(213)	(425)	(425)
Employee Stock Ownership Plan Dividend Deduction	(173)	(157)	(345)	(315)
Other Items – Net	11	(137)	33	(186)
Income Tax Expense—Continuing Operations	$ 5,897	$ 5,083	$ 12,260	$ 10,575
Effective Income Tax Rate – Continuing Operations	26.10%	24.60%	25.30%	26.00%

Note 14 - Income Tax Expense 76

Note 14 - Income Tax Expense - Continuing Operations - Effective Income Tax Rate (Details) (Parentheticals)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Composite Federal and State Statutory Rate	39.00%	39.00%	39.00%	39.00%

Note 14 - Income Tax Expense 77

Note 14 - Income Tax Expense - Continuing Operations - Summary of Activity Related to Unrecognized Tax Benefit (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Balance on January 1	$ 891	$ 468
Increases Related to Tax Positions for Prior Years
Increases Related to Tax Positions for Current Year	147	26
Uncertain Positions Resolved During Year
Balance on June 30	$ 1,038	$ 494

Note 16 - Discontinued Operat78

Note 16 - Discontinued Operations (Details Textual)	6 Months Ended
	Jun. 30, 2017
Minimum [Member]
Standard Product Warranty Term	1 year
Maximum [Member]
Standard Product Warranty Term	15 years

Note 16 - Discontinued Operat79

Note 16 - Discontinued Operations - Schedule of Warranty Reserves (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Balance, January 1	$ 1,369	$ 2,103
Additional Provision for Warranties Made During the Year
Settlements Made During the Year	(51)
Decrease in Warranty Estimates for Prior Years	(200)	(230)
Balance, June 30	$ 1,118	$ 1,873