ACCOUNTS RECEIVABLE - OTHER (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	$ 16,269	$ 25,445
Proportionate ownership interest (as a percent)	12.00%
Gas
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	19	27
Westar Generating, Inc.
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	1,642	636
Westar Generating, Inc. | State Line Combined Cycle Unit
Accounts receivable other
Proportionate ownership interest (as a percent)	40.00%
Non-regulated subsidiary companies
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	1,037	602
Accounts receivable for plant reimbursements, line extensions, highway projects, etc.
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	811	5,322
Taxes receivable overpayment of estimated income taxes
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	5,516	10,807
Accounts receivable for energy trading margin deposit
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	5,818	3,878
Accounts receivable for true-up on maintenance contracts
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	1,323	1,512
Accounts receivable for true-up on maintenance contracts | Westar Generating, Inc.
Accounts receivable other
Percentage of accounts receivable belonging to Westar Generating, Inc.	40.00%
Accounts receivable for insurance proceeds for SLCC generator failure
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER		2,596
Accounts receivable for insurance proceeds for SLCC generator failure | Westar Generating, Inc.
Accounts receivable other
Percentage of accounts receivable belonging to Westar Generating, Inc.	40.00%
Other;.
Accounts receivable other
TOTAL ACCOUNTS RECEIVABLE - OTHER	$ 103	$ 65