Schedule I Disclosures for Parent Company Only Schedule I, Fair Value by Balance Sheet Grouping (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Derivatives, Carrying Amount and Fair Value [Line Items]
Cash and cash equivalents	$ 7,841		$ 15,462
Notes payable	82,500		277,000
Long-term Debt, including current maturities	1,396,948		1,042,850
Reported Value Measurement [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Cash and cash equivalents	7,841		15,462
Notes payable	82,500		277,000
Long-term Debt, including current maturities	1,396,948		1,042,850
Total Estimate of Fair Value, Fair Value Disclosure [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Cash and cash equivalents, at fair value	7,841	[1]	15,462	[1]
Notes payable, fair value	82,500	[1]	277,000	[1]
Long-term debt, including current maturities, at fair value	1,491,422	[2]	1,231,559	[2]
Black Hills Corporation [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Cash and cash equivalents	1,664		1,266		3,114	219
Notes payable	82,500		277,000
Black Hills Corporation [Member] | Reported Value Measurement [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Cash and cash equivalents	1,664		1,266
Notes payable	82,500		277,000
Long-term Debt, including current maturities	1,000,000		550,000
Black Hills Corporation [Member] | Total Estimate of Fair Value, Fair Value Disclosure [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Cash and cash equivalents, at fair value	1,664	[1]	1,266	[1]
Notes payable, fair value	82,500	[1]	277,000	[1]
Long-term debt, including current maturities, at fair value	$ 1,028,384	[2]	$ 615,239	[2]

[1] Carrying value approximates fair value due to either short-term length of maturity or variable interest rates that approximate prevailing market rates and therefore is classified in Level 1 in the fair value hierarchy.

[2] Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy.