Common Equity (Tables)

9 Months Ended

Sep. 30, 2020

Schedule of Capitalization, Equity [Line Items]

Common Share Activity

A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2020	245,022,800
Equity forward agreements	4,275,127
Shareowner Direct Plan	364,531
Equity-based compensation plans	98,205
Shares outstanding, September 30, 2020	249,760,663

Changes in Shareowners' Equity

A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$2		$2,683		$2,874			($1	)		($10	)		$200		$5,748
Net income attributable to Alliant Energy common shareowners					246											246
Common stock dividends ($0.38 per share)					(94		)									(94		)
Shareowner Direct Plan issuances			6													6
Equity-based compensation plans and other			4								(1		)			3
Ending balance, September 30, 2020		$2		$2,693		$3,026			($1	)		($11	)		$200		$5,909
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$2		$2,109		$2,598			$1			($10	)		$200		$4,900
Net income attributable to Alliant Energy common shareowners					226											226
Common stock dividends ($0.355 per share)					(85		)									(85		)
Equity forward settlements and Shareowner Direct Plan issuances			125													125
Equity-based compensation plans and other			3													3
Ending balance, September 30, 2019		$2		$2,237		$2,739			$1			($10	)		$200		$5,169

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$2		$2,446		$2,766			$1			($10	)		$200		$5,405
Net income attributable to Alliant Energy common shareowners					550											550
Common stock dividends ($1.14 per share)					(281		)									(281		)
Equity forward settlements and Shareowner Direct Plan issuances			241													241
Equity-based compensation plans and other			6								(1		)			5
Adoption of new accounting standard, net of tax (refer to Note 1(d))					(9		)									(9		)
Other comprehensive loss, net of tax								(2		)						(2		)
Ending balance, September 30, 2020		$2		$2,693		$3,026			($1	)		($11	)		$200		$5,909
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$2		$2,046		$2,546			$2			($10	)		$200		$4,786
Net income attributable to Alliant Energy common shareowners					446											446
Common stock dividends ($1.065 per share)					(253		)									(253		)
Equity forward settlements and Shareowner Direct Plan issuances			185													185
Equity-based compensation plans and other			6													6
Other comprehensive loss, net of tax								(1		)						(1		)
Ending balance, September 30, 2019		$2		$2,237		$2,739			$1			($10	)		$200		$5,169

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$33		$2,523		$915			$200		$3,671
Net income available for common stock					148					148
Common stock dividends					(59		)			(59		)
Capital contributions from parent			170							170
Ending balance, September 30, 2020		$33		$2,693		$1,004			$200		$3,930
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$33		$2,323		$789			$200		$3,345
Net income available for common stock					141					141
Common stock dividends					(42		)			(42		)
Ending balance, September 30, 2019		$33		$2,323		$888			$200		$3,444

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$33		$2,348		$891			$200		$3,472
Net income available for common stock					290					290
Common stock dividends					(177		)			(177		)
Capital contributions from parent			345							345
Ending balance, September 30, 2020		$33		$2,693		$1,004			$200		$3,930
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$33		$2,223		$775			$200		$3,231
Net income available for common stock					239					239
Common stock dividends					(126		)			(126		)
Capital contributions from parent			100							100
Ending balance, September 30, 2019		$33		$2,323		$888			$200		$3,444

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$66		$1,459		$927			$2,452
Net income					73			73
Common stock dividends					(43		)	(43		)
Ending balance, September 30, 2020		$66		$1,459		$957			$2,482
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$66		$1,309		$810			$2,185
Net income					76			76
Common stock dividends					(36		)	(36		)
Capital contributions from parent			100					100
Ending balance, September 30, 2019		$66		$1,409		$850			$2,325

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$66		$1,434		$864			$2,364
Net income					220			220
Common stock dividends					(127		)	(127		)
Capital contributions from parent			25					25
Ending balance, September 30, 2020		$66		$1,459		$957			$2,482
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$66		$1,309		$775			$2,150
Net income					183			183
Common stock dividends					(108		)	(108		)
Capital contributions from parent			100					100
Ending balance, September 30, 2019		$66		$1,409		$850			$2,325

IPL [Member]

Schedule of Capitalization, Equity [Line Items]

Changes in Shareowners' Equity

A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$2		$2,683		$2,874			($1	)		($10	)		$200		$5,748
Net income attributable to Alliant Energy common shareowners					246											246
Common stock dividends ($0.38 per share)					(94		)									(94		)
Shareowner Direct Plan issuances			6													6
Equity-based compensation plans and other			4								(1		)			3
Ending balance, September 30, 2020		$2		$2,693		$3,026			($1	)		($11	)		$200		$5,909
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$2		$2,109		$2,598			$1			($10	)		$200		$4,900
Net income attributable to Alliant Energy common shareowners					226											226
Common stock dividends ($0.355 per share)					(85		)									(85		)
Equity forward settlements and Shareowner Direct Plan issuances			125													125
Equity-based compensation plans and other			3													3
Ending balance, September 30, 2019		$2		$2,237		$2,739			$1			($10	)		$200		$5,169

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$2		$2,446		$2,766			$1			($10	)		$200		$5,405
Net income attributable to Alliant Energy common shareowners					550											550
Common stock dividends ($1.14 per share)					(281		)									(281		)
Equity forward settlements and Shareowner Direct Plan issuances			241													241
Equity-based compensation plans and other			6								(1		)			5
Adoption of new accounting standard, net of tax (refer to Note 1(d))					(9		)									(9		)
Other comprehensive loss, net of tax								(2		)						(2		)
Ending balance, September 30, 2020		$2		$2,693		$3,026			($1	)		($11	)		$200		$5,909
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$2		$2,046		$2,546			$2			($10	)		$200		$4,786
Net income attributable to Alliant Energy common shareowners					446											446
Common stock dividends ($1.065 per share)					(253		)									(253		)
Equity forward settlements and Shareowner Direct Plan issuances			185													185
Equity-based compensation plans and other			6													6
Other comprehensive loss, net of tax								(1		)						(1		)
Ending balance, September 30, 2019		$2		$2,237		$2,739			$1			($10	)		$200		$5,169

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$33		$2,523		$915			$200		$3,671
Net income available for common stock					148					148
Common stock dividends					(59		)			(59		)
Capital contributions from parent			170							170
Ending balance, September 30, 2020		$33		$2,693		$1,004			$200		$3,930
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$33		$2,323		$789			$200		$3,345
Net income available for common stock					141					141
Common stock dividends					(42		)			(42		)
Ending balance, September 30, 2019		$33		$2,323		$888			$200		$3,444

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$33		$2,348		$891			$200		$3,472
Net income available for common stock					290					290
Common stock dividends					(177		)			(177		)
Capital contributions from parent			345							345
Ending balance, September 30, 2020		$33		$2,693		$1,004			$200		$3,930
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$33		$2,223		$775			$200		$3,231
Net income available for common stock					239					239
Common stock dividends					(126		)			(126		)
Capital contributions from parent			100							100
Ending balance, September 30, 2019		$33		$2,323		$888			$200		$3,444

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$66		$1,459		$927			$2,452
Net income					73			73
Common stock dividends					(43		)	(43		)
Ending balance, September 30, 2020		$66		$1,459		$957			$2,482
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$66		$1,309		$810			$2,185
Net income					76			76
Common stock dividends					(36		)	(36		)
Capital contributions from parent			100					100
Ending balance, September 30, 2019		$66		$1,409		$850			$2,325

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$66		$1,434		$864			$2,364
Net income					220			220
Common stock dividends					(127		)	(127		)
Capital contributions from parent			25					25
Ending balance, September 30, 2020		$66		$1,459		$957			$2,482
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$66		$1,309		$775			$2,150
Net income					183			183
Common stock dividends					(108		)	(108		)
Capital contributions from parent			100					100
Ending balance, September 30, 2019		$66		$1,409		$850			$2,325

WPL [Member]

Schedule of Capitalization, Equity [Line Items]

Changes in Shareowners' Equity

A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$2		$2,683		$2,874			($1	)		($10	)		$200		$5,748
Net income attributable to Alliant Energy common shareowners					246											246
Common stock dividends ($0.38 per share)					(94		)									(94		)
Shareowner Direct Plan issuances			6													6
Equity-based compensation plans and other			4								(1		)			3
Ending balance, September 30, 2020		$2		$2,693		$3,026			($1	)		($11	)		$200		$5,909
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$2		$2,109		$2,598			$1			($10	)		$200		$4,900
Net income attributable to Alliant Energy common shareowners					226											226
Common stock dividends ($0.355 per share)					(85		)									(85		)
Equity forward settlements and Shareowner Direct Plan issuances			125													125
Equity-based compensation plans and other			3													3
Ending balance, September 30, 2019		$2		$2,237		$2,739			$1			($10	)		$200		$5,169

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$2		$2,446		$2,766			$1			($10	)		$200		$5,405
Net income attributable to Alliant Energy common shareowners					550											550
Common stock dividends ($1.14 per share)					(281		)									(281		)
Equity forward settlements and Shareowner Direct Plan issuances			241													241
Equity-based compensation plans and other			6								(1		)			5
Adoption of new accounting standard, net of tax (refer to Note 1(d))					(9		)									(9		)
Other comprehensive loss, net of tax								(2		)						(2		)
Ending balance, September 30, 2020		$2		$2,693		$3,026			($1	)		($11	)		$200		$5,909
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$2		$2,046		$2,546			$2			($10	)		$200		$4,786
Net income attributable to Alliant Energy common shareowners					446											446
Common stock dividends ($1.065 per share)					(253		)									(253		)
Equity forward settlements and Shareowner Direct Plan issuances			185													185
Equity-based compensation plans and other			6													6
Other comprehensive loss, net of tax								(1		)						(1		)
Ending balance, September 30, 2019		$2		$2,237		$2,739			$1			($10	)		$200		$5,169

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$33		$2,523		$915			$200		$3,671
Net income available for common stock					148					148
Common stock dividends					(59		)			(59		)
Capital contributions from parent			170							170
Ending balance, September 30, 2020		$33		$2,693		$1,004			$200		$3,930
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$33		$2,323		$789			$200		$3,345
Net income available for common stock					141					141
Common stock dividends					(42		)			(42		)
Ending balance, September 30, 2019		$33		$2,323		$888			$200		$3,444

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$33		$2,348		$891			$200		$3,472
Net income available for common stock					290					290
Common stock dividends					(177		)			(177		)
Capital contributions from parent			345							345
Ending balance, September 30, 2020		$33		$2,693		$1,004			$200		$3,930
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$33		$2,223		$775			$200		$3,231
Net income available for common stock					239					239
Common stock dividends					(126		)			(126		)
Capital contributions from parent			100							100
Ending balance, September 30, 2019		$33		$2,323		$888			$200		$3,444

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2020
Beginning balance, June 30, 2020		$66		$1,459		$927			$2,452
Net income					73			73
Common stock dividends					(43		)	(43		)
Ending balance, September 30, 2020		$66		$1,459		$957			$2,482
Three Months Ended September 30, 2019
Beginning balance, June 30, 2019		$66		$1,309		$810			$2,185
Net income					76			76
Common stock dividends					(36		)	(36		)
Capital contributions from parent			100					100
Ending balance, September 30, 2019		$66		$1,409		$850			$2,325

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2020
Beginning balance, December 31, 2019		$66		$1,434		$864			$2,364
Net income					220			220
Common stock dividends					(127		)	(127		)
Capital contributions from parent			25					25
Ending balance, September 30, 2020		$66		$1,459		$957			$2,482
Nine Months Ended September 30, 2019
Beginning balance, December 31, 2018		$66		$1,309		$775			$2,150
Net income					183			183
Common stock dividends					(108		)	(108		)
Capital contributions from parent			100					100
Ending balance, September 30, 2019		$66		$1,409		$850			$2,325