STATEMENTS OF EQUITY - USD ($) $ in Millions	Total	Total Common Shareholder's Equity	Common Stock	Additional Paid in Capital	Retained Earnings	WPSI transfer Total Common Shareholder's Equity	WPSI transfer Common Stock	WPSI transfer Additional Paid in Capital	WPSI transfer Retained Earnings	UMERC transfer Total Common Shareholder's Equity	UMERC transfer Common Stock	UMERC transfer Additional Paid in Capital	UMERC transfer Retained Earnings
Balance at Dec. 31, 2016		$ 1,628.2	$ 95.6	$ 966.9	$ 565.7
Equity
Net income	$ 154.9	154.9	0.0	0.0	154.9
Equity contribution from parent	75.0	75.0	0.0	75.0	0.0
Transfer of ownership interest in WPSI and related taxes						$ (25.3)	$ 0.0	$ (25.3)	$ 0.0
Transfer of net assets to UMERC										$ (20.6)	$ 0.0	$ (20.6)	$ 0.0
Payment of dividends to parent	(195.0)	(195.0)	0.0	0.0	(195.0)
Other		0.1	0.0	0.1	0.0
Balance at Dec. 31, 2017		1,617.3	95.6	996.1	525.6
Equity
Net income	172.8	172.8	0.0	0.0	172.8
Equity contribution from parent	120.0	120.0	0.0	120.0	0.0
Payment of dividends to parent	(140.0)	(140.0)	0.0	0.0	(140.0)
Other		(0.2)	0.0	(0.2)	0.0
Balance at Dec. 31, 2018		1,769.9	95.6	1,115.9	558.4
Equity
Net income	184.7	184.7	0.0	0.0	184.7
Equity contribution from parent	105.0	105.0	0.0	105.0	0.0
Payment of dividends to parent	$ (120.0)	(120.0)	0.0	0.0	(120.0)
Other		0.2	0.0	0.2	0.0
Balance at Dec. 31, 2019		$ 1,939.8	$ 95.6	$ 1,221.1	$ 623.1