Schedule I Disclosures for Parent Company Only Schedule I, Condensed Statement of Income for Parent Company (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended											12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Revenue	$ 355,448	$ 259,907	$ 279,826	$ 380,671	$ 318,862		$ 246,808		$ 242,363		$ 365,851	$ 1,275,852		$ 1,173,884		$ 1,272,188
Operating expenses												1,020,300		930,173		1,085,949
Operating income	71,103	55,566	49,037	79,846	75,262	[1]	77,810	[1]	20,591	[1]	70,048	255,552		243,711		186,239
Other income (expense):
Equity income (loss) in earnings of subsidiaries												(86)		10		1,121
Interest expense												(111,788)	[2]	(113,610)	[3]	(91,383)
Unrealized gain (loss) on interest rate swaps, net												30,169		1,882		(42,010)
Interest income												1,723		1,957		2,017
Other income (expense), net												1,798		2,965		3,726
Total other income (expense)												(78,012)		(106,816)		(128,771)
Income tax benefit (expense)												(61,608)		(48,400)		(18,224)
Net income (loss) available for common stock												114,962		81,528		49,730
Black Hills Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Revenue												0		0		0
Operating expenses												1,339		831		772
Operating income												(1,339)		(831)		(772)
Other income (expense):
Equity income (loss) in earnings of subsidiaries												100,690		93,479		87,150
Interest expense												(7,827)		(19,665)		(15,229)
Unrealized gain (loss) on interest rate swaps, net												30,169		1,882		(42,010)
Interest income												30		32		3
Other income (expense), net												(3)		49		(42)
Total other income (expense)												123,059		75,777		29,872
Income (loss) before income taxes												121,720		74,946		29,100
Income tax benefit (expense)												(6,758)		6,582		20,630
Net income (loss) available for common stock												$ 114,962		$ 81,528		$ 49,730

[1] Second quarter includes a pre-tax ceiling test impairment loss of $27 million and the third and fourth quarters include a pre-tax gain on sale of the Williston Basin assets of $27 million and $1.8 million, respectively.

[2] Power Generation includes costs associated with interest rate swaps settled and write-off of deferred financing costs upon repayment of Black Hills Wyoming Project Financing and Corporate includes a the write-off of deferred financing costs and a make-whole provision from early repayment of long-term debt (see Note 5).

[3] Corporate includes a make-whole provision from early repayment of long-term debt (see Note 5).