Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Derivative, Collateral, Right to Reclaim Cash	$ 4,434	$ 26,809
Current Assets:
Cash and cash equivalents	9,896	14,656
Accounts and notes receivable-less allowances of $2,419 and $5,233, respectively	166,657	165,824
Materials and supplies, fuel stock and stored natural gas	66,583	63,881
Regulatory assets	21,851	48,552
Other current assets	40,142	54,010
Total current assets	305,129	346,923
Net Utility Property	4,797,007	4,648,930
Goodwill	52,426	57,672
Non-current regulatory assets	670,802	614,354
Other property and investments-net and other non-current assets	257,092	114,697
Total assets	6,082,456	5,782,576
Current Liabilities:
Accounts payable	110,219	108,372
Current portion of long-term debt and capital leases	52,000	107,645
Short-term borrowings	185,800	190,000
Regulatory liabilities	51,715	113,209
Other current liabilities	130,979	120,358
Total current liabilities	530,713	639,584
Long-term debt and capital leases	1,843,768	1,755,529
Long-term debt to affiliated trusts	51,547	51,547
Pensions and other postretirement benefits	212,006	222,537
Deferred income taxes	528,513	487,602
Non-current regulatory liabilities	775,436	780,701
Other non-current liabilities, regulatory liabilities and deferred credits	201,189	71,031
Total liabilities	4,143,172	4,008,531
Commitments and Contingencies (See Notes to Consolidated Financial Statements)
Avista Corporation Shareholders’ Equity:
Common stock, no par value	1,210,741	1,136,491
Accumulated other comprehensive loss	(10,259)	(7,866)
Retained earnings	738,802	644,595
Total Avista Corporation shareholders’ equity	1,939,284	1,773,220
Noncontrolling Interests	0	825
Total equity	1,939,284	1,774,045
Total liabilities and equity	6,082,456	5,782,576
Prepaid Expense, Current	19,652	17,536
Income Taxes Receivable, Current	11,047	822
Other Assets, Miscellaneous, Current	$ 5,009	$ 8,843