Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Operating Activities
Net Income	$ 125,152	$ 77,183
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation and Amortization	68,109	61,230
Deferred Tax Credits	(558)	(986)
Deferred Income Taxes	18,835	20,353
Change in Deferred Debits and Other Assets	6,166	3,439
Discretionary Contribution to Pension Plan	(10,000)	(11,200)
Change in Noncurrent Liabilities and Deferred Credits	2,662	3,237
Allowance for Equity Funds Used During Construction	(427)	(3,104)
Stock Compensation Expense	6,354	5,282
Other, Net	(3,480)	(176)
Cash (Used for) Provided by Current Assets and Current Liabilities:
Change in Receivables	(64,800)	(20,025)
Change in Inventories	(22,450)	15,980
Change in Other Current Assets	(12,159)	2,023
Change in Payables and Other Current Liabilities	40,574	(12,063)
Change in Interest Payable and Income Taxes Receivable/Payable	774	103
Net Cash Provided by Operating Activities	154,752	141,276
Investing Activities
Capital Expenditures	(117,312)	(220,630)
Proceeds from Disposal of Noncurrent Assets	5,819	4,617
Cash Used for Investments and Other Assets	(5,591)	(6,372)
Net Cash Used in Investing Activities	(117,084)	(222,385)
Financing Activities
Change in Checks Written in Excess of Cash	(3,133)	90
Net Short-Term Borrowings	16,860	42,600
Proceeds from Issuance of Common Stock	0	35,219
Common Stock Issuance Expenses	(67)	(465)
Payments for Shares Withheld for Employee Tax Obligations	(1,633)	(2,069)
Proceeds from Issuance of Long-Term Debt	0	75,000
Debt Issuance Expenses	(772)	(369)
Payments for Retirement of Long-Term Debt	(169)	(136)
Dividends Paid	(48,645)	(45,056)
Net Cash (Used in) Provided by Financing Activities	(37,559)	104,814
Net Change in Cash and Cash Equivalents	109	23,705
Cash and Cash Equivalents at Beginning of Period	1,163	21,199
Cash and Cash Equivalents at End of Period	1,272	44,904
Supplemental Disclosure of Noncash Investing Activities
Accrued Property, Plant, and Equipment Additions	$ 14,358	$ 112,314

Represents change in checks written in excess of cash.

No definition available.

Name:	ottr_ChangeInChecksWrittenInExcessOfCash
Namespace Prefix:	ottr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The net change during the reporting period in the value of expenditures made during the current reporting period for benefits that will be received over a period of years. Deferred charges differ from prepaid expenses in that they usually extend over a long period of time and may or may not be regularly recurring costs of operation. Also includes, the net change during the reporting period in other assets not otherwise defined in the taxonomy.

+ References

No definition available.