GUARANTEES (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Guarantees
Total guarantees	$ 821.1
Guarantees expiring in less than 1 year	522.0
Guarantees expiring within 1 to 3 years	4.9
Guarantees with expiration over 3 years	294.2
Integrys Energy Services
Guarantees
Total guarantees	597.1
UPPCO
Guarantees
Total guarantees	3.2
Guarantees supporting commodity transactions
Guarantees
Total guarantees	705.3
Guarantees expiring in less than 1 year	460.5
Guarantees expiring within 1 to 3 years	4.6
Guarantees with expiration over 3 years	240.2
Guarantees supporting commodity transactions | Integrys Energy Services
Guarantees
Total guarantees	520.4
Guarantees supporting commodity transactions | IBS
Guarantees
Total guarantees	5.0
Guarantees supporting commodity transactions | UPPCO
Guarantees
Total guarantees	2.0
Guarantees supporting commodity transactions | MERC
Guarantees
Total guarantees	120.0
Guarantees supporting commodity transactions | MGU
Guarantees
Total guarantees	57.5
Guarantees supporting commodity transactions | ITF
Guarantees
Total guarantees	0.4
Standby letters of credit
Guarantees
Total guarantees	27.7
Guarantees expiring in less than 1 year	27.3
Guarantees expiring within 1 to 3 years	0.3
Guarantees with expiration over 3 years	0.1
Standby letters of credit | Integrys Energy Services
Guarantees
Total guarantees	26.0
Standby letters of credit | ITF, MERC, MGU, NSG, PGL, UPPCO, and WPS
Guarantees
Total guarantees	1.7
Surety bonds
Guarantees
Total guarantees	32.7
Guarantees expiring in less than 1 year	32.7
Guarantees expiring within 1 to 3 years	0
Guarantees with expiration over 3 years	0
Other guarantees
Guarantees
Total guarantees	55.4
Guarantees expiring in less than 1 year	1.5
Guarantees expiring within 1 to 3 years	0
Guarantees with expiration over 3 years	53.9
Other guarantees | Integrys Energy Services
Guarantees
Total guarantees	35.0
Other guarantees | Integrys Energy Services | Texas retail marketing business
Guarantees
Total guarantees	10.0
Other guarantees | Integrys Energy Services | WPS Beaver Falls Generation, LLC and WPS Syracuse Generation, LLC
Guarantees
Total guarantees	1.8
Other guarantees | ITF
Guarantees
Total guarantees	2.4
Other indemnifications and workers compensation coverage
Guarantees
Total guarantees	$ 6.2