Note 10 - Short-term and Long-term Borrowings (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Line of Credit Facilities [Table Text Block]

(in thousands)	Line Limit		In Use on December 31, 2018		Restricted due to Outstanding Letters of Credit		Available on December 31, 2018		Available on December 31, 2017
Otter Tail Corporation Credit Agreement	$	130,000	$	9,215	$	--	$	120,785	$	130,000
OTP Credit Agreement		170,000		9,384		300		160,316		57,329
Total	$	300,000	$	18,599	$	300	$	281,101	$	187,329

Schedule of Debt [Table Text Block]

December 31, 201 8 (in thousands)	OTP		Otter Tail Corporation		Otter Tail Corporation Consolidated
Short-Term Debt	$	9,384	$	9,215	$	18,599
Long-Term Debt:
3.55% Guaranteed Senior Notes, due December 15, 2026			$	80,000	$	80,000
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
Senior Unsecured Notes 4.07%, Series 2018A, due February 7, 2048		100,000				100,000
PACE Note, 2.54%, due March 18, 2021				523		523
Total	$	512,000	$	80,523	$	592,523
Less: Current Maturities net of Unamortized Debt Issuance Costs		--		172		172
Unamortized Long-Term Debt Issuance Costs		1,942		407		2,349
Total Long-Term Debt net of Unamortized Debt Issuance Costs	$	510,058	$	79,944	$	590,002
Total Short-Term and Long-Term Debt (with current maturities)	$	519,442	$	89,331	$	608,773

December 31, 2017 (in thousands)	OTP		Otter Tail Corporation		Otter Tail Corporation Consolidated
Short-Term Debt	$	112,371	$	--	$	112,371
Long-Term Debt:
3.55% Guaranteed Senior Notes, due December 15, 2026			$	80,000	$	80,000
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				27		27
PACE Note, 2.54%, due March 18, 2021				684		684
Total	$	412,000	$	80,711	$	492,711
Less: Current Maturities net of Unamortized Debt Issuance Costs		--		186		186
Unamortized Long-Term Debt Issuance Costs		1,684		461		2,145
Total Long-Term Debt net of Unamortized Debt Issuance Costs	$	410,316	$	80,064	$	490,380
Total Short-Term and Long-Term Debt (with current maturities)	$	522,687	$	80,250	$	602,937

Schedule of Maturities of Long-term Debt [Table Text Block]

(in thousands)	2019		2020		2021		2022		2023
Aggregate Amounts of Debt Maturities	$	172	$	185	$	140,166	$	30,000	$	--