CONDENSED STATEMENTS OF EQUITY - USD ($) $ in Millions	Total	Total common shareholder's equity	Common stock	Additional paid in capital	Retained earnings
Balance at Dec. 31, 2019		$ 1,939.8	$ 95.6	$ 1,221.1	$ 623.1
Statements of equity
Net income		68.2	0.0	0.0	68.2
Equity contribution from parent		100.0	0.0	100.0	0.0
Payment of dividends to parent		(30.0)	0.0	0.0	(30.0)
Stock-based compensation and other		0.1	0.0	0.1	0.0
Balance at Mar. 31, 2020		2,078.1	95.6	1,321.2	661.3
Balance at Dec. 31, 2019		1,939.8	95.6	1,221.1	623.1
Statements of equity
Net income	$ 192.2
Equity contribution from parent	205.0
Balance at Sep. 30, 2020		2,167.2	95.6	1,426.3	645.3
Balance at Mar. 31, 2020		2,078.1	95.6	1,321.2	661.3
Statements of equity
Net income		47.7	0.0	0.0	47.7
Equity contribution from parent		105.0	0.0	105.0	0.0
Payment of dividends to parent		(110.0)	0.0	0.0	(110.0)
Stock-based compensation and other		0.1	0.0	0.1	0.0
Balance at Jun. 30, 2020		2,120.9	95.6	1,426.3	599.0
Statements of equity
Net income	76.3	76.3	0.0	0.0	76.3
Payment of dividends to parent		(30.0)	0.0	0.0	(30.0)
Balance at Sep. 30, 2020		2,167.2	95.6	1,426.3	645.3
Balance at Dec. 31, 2020		2,116.7	95.6	1,436.4	584.7
Statements of equity
Net income		69.3	0.0	0.0	69.3
Payment of dividends to parent		(30.0)	0.0	0.0	(30.0)
Stock-based compensation and other		0.1	0.0	0.1	0.0
Balance at Mar. 31, 2021		2,156.1	95.6	1,436.5	624.0
Balance at Dec. 31, 2020		2,116.7	95.6	1,436.4	584.7
Statements of equity
Net income	201.4
Equity contribution from parent	55.0
Balance at Sep. 30, 2021		2,283.3	95.6	1,491.6	696.1
Balance at Mar. 31, 2021		2,156.1	95.6	1,436.5	624.0
Statements of equity
Net income		60.2	0.0	0.0	60.2
Payment of dividends to parent		(30.0)	0.0	0.0	(30.0)
Stock-based compensation and other		0.1	0.0	0.1	0.0
Balance at Jun. 30, 2021		2,186.4	95.6	1,436.6	654.2
Statements of equity
Net income	$ 71.9	71.9	0.0	0.0	71.9
Equity contribution from parent		55.0	0.0	55.0	0.0
Payment of dividends to parent		(30.0)	0.0	0.0	(30.0)
Balance at Sep. 30, 2021		$ 2,283.3	$ 95.6	$ 1,491.6	$ 696.1