SCHEDULE I - CONDENSED PARENT COMPANY FINANCIAL STATEMENTS STATEMENTS OF CASH FLOWS (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net income attributed to common shareholders	$ 276.9	$ 351.8	$ 281.4
Adjustments to reconcile net income to net cash provided by operating activities
Dividends from subsidiaries	186.1
Deferred income taxes and investment tax credits	165.9	209.8	146.0
Gain on sale of other assets	(3.5)	0	0
Other	43.5	34.9	25.3
Changes in working capital
Accounts receivable	11.2	(358.6)	(26.2)
Other current assets	(11.6)	(50.4)	6.6
Accounts payable	12.7	142.9	21.8
Other current liabilities	88.2	43.5	29.3
Net cash provided by operating activities	601.4	554.9	573.8
Investing activities
Net cash provided by (used for) investing activities	(336.5)	(1,022.7)	(602.6)
Financing Activities
Commercial paper, net	(8.4)	(156.4)	179.1
Issuance of long-term debt	200.0	1,174.0	428.0
Repayment of long-term debt	(175.0)	(363.5)	(305.2)
Proceeds from stock option exercises	85.8	38.7	55.8
Shares purchased for stock-based compensation	(142.9)	(2.0)	(89.9)
Dividends paid on common stock	(216.3)	(202.6)	(211.9)
Other	(9.3)	(22.4)	(24.7)
Net cash (used for) provided by financing activities	(269.2)	462.7	28.1
Cash and cash equivalents at beginning of year	16.8
Cash and cash equivalents at end of year	18.0	16.8
Supplemental cash flow information
Cash paid for interest	146.8	116.1	109.7
Cash paid (received) for income taxes	6.3	(4.8)	(47.6)
Integrys Energy Group, Inc.
Operating activities
Net income attributed to common shareholders	276.9	351.8	281.4
Adjustments to reconcile net income to net cash provided by operating activities
Equity earnings from subsidiaries	(324.5)	(401.3)	(321.3)
Dividends from subsidiaries	176.5	169.6	163.9
Deferred income taxes and investment tax credits	(46.0)	26.3	11.0
Gain on sale of other assets	(4.0)	0	0
Other	4.9	2.8	(3.7)
Changes in working capital
Accounts receivable	0.7	(0.7)	0.4
Accounts receivable from related parties	0.5	0.6	1.0
Other current assets	12.5	(7.9)	29.0
Accounts payable	1.6	0.6	(0.5)
Accounts payable to related parties	2.6	(0.2)	(0.4)
Other current liabilities	27.6	(2.4)	0.9
Net cash provided by operating activities	67.1	139.2	161.7
Investing activities
Short-term notes receivable from related parties	33.3	(50.4)	(12.1)
Issuance of long-term notes receivable to related parties	(20.0)	(35.0)	0
Repayment of long-term notes receivable from related parties	71.5	44.5	1.3
Equity contributions to subsidiaries	(218.4)	(234.6)	(89.9)
Return of capital from subsidiaries	52.5	75.0	110.5
Proceeds from the sale of other assets	4.1	0	0
Rabbi trust funding related to potential change in control	(115.5)	0	0
Net cash provided by (used for) investing activities	463.4	(200.5)	9.8
Financing Activities
Commercial paper, net	(116.0)	(85.2)	115.8
Short-term notes payable to related parties	(45.1)	(92.3)	76.2
Repayment of long-term notes payable to related parties	0	0	(21.0)
Issuance of long-term debt	0	400.0	0
Repayment of long-term debt	(100.0)	0	(100.0)
Proceeds from stock option exercises	85.8	38.7	55.8
Shares purchased for stock-based compensation	(127.6)	0	(75.3)
Issuance of common stock	2.4	19.2	0
Dividends paid on common stock	(216.3)	(202.6)	(211.9)
Other	(8.9)	(18.8)	(10.4)
Net cash (used for) provided by financing activities	(525.7)	59.0	(170.8)
Net change in cash and cash equivalents	4.8	(2.3)	0.7
Cash and cash equivalents at beginning of year	0.3	2.6	1.9
Cash and cash equivalents at end of year	5.1	0.3	2.6
Supplemental cash flow information
Cash paid for interest	59.4	44.4	44.4
Cash paid for interest – related parties	0.4	0.7	1.4
Cash paid (received) for income taxes	40.2	(3.0)	(24.1)
Integrys Energy Group, Inc. | UPPCO
Adjustments to reconcile net income to net cash provided by operating activities
(Gain) loss on sale of business	(86.5)	0	0
Investing activities
Proceeds from the sale of a business	336.7	0	0
Integrys Energy Group, Inc. | IES's retail energy business
Adjustments to reconcile net income to net cash provided by operating activities
(Gain) loss on sale of business	24.3	0	0
Investing activities
Proceeds from the sale of a business	$ 319.2	$ 0	$ 0