Consolidated Statements of Equity - USD ($) $ in Millions	Total	Total Common Shareholders' Equity	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income	Preferred Stock of Subsidiary
Balance at Dec. 31, 2013	$ 4,263.4	$ 4,233.0	$ 2.3	$ 349.7	$ 3,880.7	$ 0.3	$ 30.4
Equity
Net income attributed to common shareholders	588.3	588.3	0.0	0.0	588.3	0.0	0.0
Other comprehensive income (loss)	0.0
Common stock dividends	(352.0)	(352.0)	0.0	0.0	(352.0)	0.0	0.0
Exercise of stock options	50.3	50.3	0.0	50.3	0.0	0.0	0.0
Purchase of common stock	(123.2)	(123.2)	0.0	(123.2)	0.0	0.0	0.0
Stock-based compensation and other	23.3	23.3	0.0	23.3	0.0	0.0	0.0
Balance at Dec. 31, 2014	4,450.1	4,419.7	2.3	300.1	4,117.0	0.3	30.4
Equity
Net income attributed to common shareholders	638.5	638.5	0.0	0.0	638.5	0.0	0.0
Other comprehensive income (loss)	4.3	4.3	0.0	0.0	0.0	4.3	0.0
Common stock dividends	(455.4)	(455.4)	0.0	0.0	(455.4)	0.0	0.0
Exercise of stock options	30.1	30.1	0.0	30.1	0.0	0.0	0.0
Issuance of common stock for the acquisition of Integrys	4,072.9	4,072.9	0.9	4,072.0	0.0	0.0	0.0
Purchase of common stock	(74.7)	(74.7)	0.0	(74.7)	0.0	0.0	0.0
Addition of WPS preferred stock	51.1	0.0	0.0	0.0	0.0	0.0	51.1
Redemption of WPS preferred stock	(52.7)	(1.6)	0.0	(1.6)	0.0	0.0	(51.1)
Stock-based compensation and other	21.0	21.0	0.0	21.3	(0.3)	0.0	0.0
Balance at Dec. 31, 2015	8,685.2	8,654.8	3.2	4,347.2	4,299.8	4.6	30.4
Equity
Net income attributed to common shareholders	939.0	939.0	0.0	0.0	939.0	0.0	0.0
Other comprehensive income (loss)	(1.7)	(1.7)	0.0	0.0	0.0	(1.7)	0.0
Common stock dividends	(624.9)	(624.9)	0.0	0.0	(624.9)	0.0	0.0
Exercise of stock options	41.6	41.6	0.0	41.6	0.0	0.0	0.0
Purchase of common stock	(108.0)	(108.0)	0.0	(108.0)	0.0	0.0	0.0
Stock-based compensation and other	29.0	29.0	0.0	29.0	0.0	0.0	0.0
Balance at Dec. 31, 2016	$ 8,960.2	$ 8,929.8	$ 3.2	$ 4,309.8	$ 4,613.9	$ 2.9	$ 30.4