Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2014

Defined Benefit Plan Disclosure [Line Items]

Defined Benefit Pension And Other Postretirement Benefits Plans

The components of net periodic benefit costs (credits) for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included in the tables below (in millions). In the “IPL” and “WPL” tables below, the defined benefit pension plans costs represent those respective costs for IPL’s and WPL’s bargaining unit employees covered under the qualified plans that are sponsored by IPL and WPL, respectively, as well as amounts directly assigned to each of IPL and WPL related to IPL’s and WPL’s current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In the “IPL” and “WPL” tables below, the OPEB plans costs (credits) represent costs (credits) for IPL and WPL employees, respectively.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$3.3			$3.9			$9.9			$11.8			$1.3			$1.5			$3.9			$4.7
Interest cost	13.6			12.3			40.6			36.8			2.4			2.1			7.1			6.3
Expected return on plan assets	(18.8		)	(18.5		)	(56.3		)	(55.5		)	(2.1		)	(2.0		)	(6.2		)	(6.0		)
Amortization of prior service cost (credit)	—			0.1			—			0.2			(3.0		)	(3.0		)	(8.9		)	(8.9		)
Amortization of actuarial loss	4.8			9.0			14.6			27.1			0.6			1.3			1.8			3.7
		$2.9			$6.8			$8.8			$20.4			($0.8	)		($0.1	)		($2.3	)		($0.2	)

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$1.8			$2.2			$5.4			$6.5			$0.6			$0.8			$1.8			$2.2
Interest cost	6.2			5.7			18.8			17.1			1.0			0.9			3.0			2.7
Expected return on plan assets	(8.9		)	(8.8		)	(26.8		)	(26.4		)	(1.5		)	(1.4		)	(4.4		)	(4.2		)
Amortization of prior service cost (credit)	—			—			—			0.1			(1.6		)	(1.6		)	(4.7		)	(4.7		)
Amortization of actuarial loss	2.0			3.8			6.0			11.4			0.3			0.6			0.8			2.0
		$1.1			$2.9			$3.4			$8.7			($1.2	)		($0.7	)		($3.5	)		($2.0	)

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$1.3			$1.5			$3.7			$4.4			$0.5			$0.6			$1.5			$1.8
Interest cost	5.7			5.2			17.0			15.5			1.0			0.8			2.9			2.5
Expected return on plan assets	(8.1		)	(8.0		)	(24.3		)	(23.9		)	(0.4		)	(0.4		)	(1.0		)	(1.0		)
Amortization of prior service cost (credit)	—			0.1			0.2			0.3			(1.0		)	(0.9		)	(2.9		)	(2.9		)
Amortization of actuarial loss	2.3			4.2			6.9			12.8			0.3			0.5			0.9			1.5
		$1.2			$3.0			$3.5			$9.1			$0.4			$0.6			$1.4			$1.9

Schedule Of Qualified And Non-Qualified Pension And Other Postretirement Benefits Costs

The following table includes the allocated qualified and non-qualified pension and OPEB costs (credits) associated with Corporate Services employees providing services to IPL and WPL for the three and nine months ended September 30 (in millions):

	Pension Benefits Costs								OPEB Credits
	Three Months				Nine Months				Three Months						Nine Months
	2014		2013		2014		2013		2014			2013			2014			2013
IPL		$0.4		$0.4		$1.1		$1.4		$—			($0.1	)		($0.2	)		($0.2	)
WPL	0.3		0.4		0.8		1.1		(0.1		)	(0.1		)	(0.2		)	(0.2		)

Employees Participate In Defined Contribution Retirement Plans

For the three and nine months ended September 30, costs related to the 401(k) savings plans, which are partially based on the participants’ contributions, were as follows (in millions):

	Alliant Energy								IPL (a)								WPL (a)
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2014		2013		2014		2013		2014		2013		2014		2013		2014		2013		2014		2013
401(k) costs		$5.3		$4.7		$17.3		$14.7		$2.7		$2.4		$8.4		$7.6		$2.4		$2.1		$8.3		$6.5

(a) IPL’s and WPL’s amounts include allocated costs associated with Corporate Services employees.

Recognized Compensation Expense And Income Tax Benefits

A summary of compensation expense (including amounts allocated to IPL and WPL) and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2014		2013		2014		2013		2014		2013		2014		2013		2014		2013		2014		2013
Compensation expense		$1.2		$4.0		$7.4		$8.6		$0.6		$2.0		$4.0		$4.4		$0.5		$1.7		$3.1		$3.7
Income tax benefits	0.5		1.6		3.0		3.5		0.2		0.8		1.6		1.8		0.3		0.7		1.3		1.5

Schedule Of Equity-based Compensation Plans Activity

Information related to fair values of nonvested performance shares and units at September 30, 2014, by year of grant, was as follows:

	Performance Shares									Performance Units
	2014 Grant			2013 Grant			2012 Grant			2014 Grant			2013 Grant			2012 Grant
Nonvested awards	49,719			49,093			45,612			19,775			21,726			23,124
Alliant Energy common stock closing price on September 30, 2014		$55.41			$55.41			$55.41
Alliant Energy common stock closing price on grant date											$53.77			$47.58			$43.05
Estimated payout percentage based on performance criteria	94		%	117		%	126		%	94		%	117		%	126		%
Fair values of each nonvested award		$52.09			$64.83			$69.82			$50.54			$55.67			$54.24

Performance Shares [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Equity-based Compensation Plans Activity

A summary of the performance shares activity was as follows:

	2014		2013
Nonvested shares, January 1	139,940		145,277
Granted	51,221		49,093
Vested	(45,235	)	(54,430	)
Forfeited	(1,502	)	—
Nonvested shares, September 30	144,424		139,940

During the nine months ended September 30, certain performance shares vested, resulting in payouts (a combination of cash and common stock) as follows:

	2014			2013
	2011 Grant			2010 Grant
Performance shares vested	45,235			54,430
Percentage of target number of performance shares	147.5		%	197.5		%
Aggregate payout value (in millions)		$3.4			$4.8
Payout - cash (in millions)		$2.9			$4.4
Payout - common stock shares issued	4,810			4,177

Performance Units [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Equity-based Compensation Plans Activity

A summary of the performance units activity was as follows:

	2014		2013
Nonvested units, January 1	65,912		64,969
Granted	20,422		22,201
Vested	(20,751	)	(19,760	)
Forfeited	(958	)	(1,498	)
Nonvested units, September 30	64,625		65,912

During the nine months ended September 30, certain performance units vested, resulting in cash payouts as follows:

	2014			2013
	2011 Grant			2010 Grant
Performance units vested	20,751			19,760
Percentage of target number of performance units	147.5		%	197.5		%
Payout value (in millions)		$1.2			$1.3

Performance Contingent Restricted Stock [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Equity-based Compensation Plans Activity

A summary of the performance contingent restricted stock activity was as follows:

	2014				2013
	Shares		Weighted Average Fair Value		Shares		Weighted Average Fair Value
Nonvested shares, January 1	158,922			$42.71	211,651			$32.42
Granted	51,221		53.77		49,093		47.58
Vested (a)	(90,847	)	40.91		—		—
Forfeited (b)	(20,484	)	39.85		(101,822	)	23.67
Nonvested shares, September 30	98,812		50.69		158,922		42.71

(a) In 2014, 45,612 and 45,235 performance contingent restricted shares granted in 2012 and 2011, respectively, vested because the specified performance criteria for such shares were met.

(b) In 2013, 101,822 performance contingent restricted shares granted in 2009 were forfeited because the specified performance criteria for such shares were not met.

Performance Contingent Cash Awards [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Equity-based Compensation Plans Activity

A summary of the performance contingent cash awards activity was as follows:

	2014		2013
Nonvested awards, January 1	96,977		59,639
Granted	42,446		39,530
Vested (a)	(55,517	)	—
Forfeited	(4,295	)	(1,413	)
Nonvested awards, September 30	79,611		97,756

(a) In 2014, 34,766 and 20,751 performance contingent cash awards granted in 2012 and 2011 vested, resulting in cash payouts valued at $1.9 million and $1.1 million, respectively.

IPL [Member]

Defined Benefit Plan Disclosure [Line Items]

Defined Benefit Pension And Other Postretirement Benefits Plans

The components of net periodic benefit costs (credits) for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included in the tables below (in millions). In the “IPL” and “WPL” tables below, the defined benefit pension plans costs represent those respective costs for IPL’s and WPL’s bargaining unit employees covered under the qualified plans that are sponsored by IPL and WPL, respectively, as well as amounts directly assigned to each of IPL and WPL related to IPL’s and WPL’s current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In the “IPL” and “WPL” tables below, the OPEB plans costs (credits) represent costs (credits) for IPL and WPL employees, respectively.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$3.3			$3.9			$9.9			$11.8			$1.3			$1.5			$3.9			$4.7
Interest cost	13.6			12.3			40.6			36.8			2.4			2.1			7.1			6.3
Expected return on plan assets	(18.8		)	(18.5		)	(56.3		)	(55.5		)	(2.1		)	(2.0		)	(6.2		)	(6.0		)
Amortization of prior service cost (credit)	—			0.1			—			0.2			(3.0		)	(3.0		)	(8.9		)	(8.9		)
Amortization of actuarial loss	4.8			9.0			14.6			27.1			0.6			1.3			1.8			3.7
		$2.9			$6.8			$8.8			$20.4			($0.8	)		($0.1	)		($2.3	)		($0.2	)

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$1.8			$2.2			$5.4			$6.5			$0.6			$0.8			$1.8			$2.2
Interest cost	6.2			5.7			18.8			17.1			1.0			0.9			3.0			2.7
Expected return on plan assets	(8.9		)	(8.8		)	(26.8		)	(26.4		)	(1.5		)	(1.4		)	(4.4		)	(4.2		)
Amortization of prior service cost (credit)	—			—			—			0.1			(1.6		)	(1.6		)	(4.7		)	(4.7		)
Amortization of actuarial loss	2.0			3.8			6.0			11.4			0.3			0.6			0.8			2.0
		$1.1			$2.9			$3.4			$8.7			($1.2	)		($0.7	)		($3.5	)		($2.0	)

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$1.3			$1.5			$3.7			$4.4			$0.5			$0.6			$1.5			$1.8
Interest cost	5.7			5.2			17.0			15.5			1.0			0.8			2.9			2.5
Expected return on plan assets	(8.1		)	(8.0		)	(24.3		)	(23.9		)	(0.4		)	(0.4		)	(1.0		)	(1.0		)
Amortization of prior service cost (credit)	—			0.1			0.2			0.3			(1.0		)	(0.9		)	(2.9		)	(2.9		)
Amortization of actuarial loss	2.3			4.2			6.9			12.8			0.3			0.5			0.9			1.5
		$1.2			$3.0			$3.5			$9.1			$0.4			$0.6			$1.4			$1.9

Schedule Of Qualified And Non-Qualified Pension And Other Postretirement Benefits Costs

The following table includes the allocated qualified and non-qualified pension and OPEB costs (credits) associated with Corporate Services employees providing services to IPL and WPL for the three and nine months ended September 30 (in millions):

	Pension Benefits Costs								OPEB Credits
	Three Months				Nine Months				Three Months						Nine Months
	2014		2013		2014		2013		2014			2013			2014			2013
IPL		$0.4		$0.4		$1.1		$1.4		$—			($0.1	)		($0.2	)		($0.2	)
WPL	0.3		0.4		0.8		1.1		(0.1		)	(0.1		)	(0.2		)	(0.2		)

Employees Participate In Defined Contribution Retirement Plans

For the three and nine months ended September 30, costs related to the 401(k) savings plans, which are partially based on the participants’ contributions, were as follows (in millions):

	Alliant Energy								IPL (a)								WPL (a)
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2014		2013		2014		2013		2014		2013		2014		2013		2014		2013		2014		2013
401(k) costs		$5.3		$4.7		$17.3		$14.7		$2.7		$2.4		$8.4		$7.6		$2.4		$2.1		$8.3		$6.5

(a) IPL’s and WPL’s amounts include allocated costs associated with Corporate Services employees.

Recognized Compensation Expense And Income Tax Benefits

A summary of compensation expense (including amounts allocated to IPL and WPL) and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2014		2013		2014		2013		2014		2013		2014		2013		2014		2013		2014		2013
Compensation expense		$1.2		$4.0		$7.4		$8.6		$0.6		$2.0		$4.0		$4.4		$0.5		$1.7		$3.1		$3.7
Income tax benefits	0.5		1.6		3.0		3.5		0.2		0.8		1.6		1.8		0.3		0.7		1.3		1.5

WPL [Member]

Defined Benefit Plan Disclosure [Line Items]

Defined Benefit Pension And Other Postretirement Benefits Plans

The components of net periodic benefit costs (credits) for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included in the tables below (in millions). In the “IPL” and “WPL” tables below, the defined benefit pension plans costs represent those respective costs for IPL’s and WPL’s bargaining unit employees covered under the qualified plans that are sponsored by IPL and WPL, respectively, as well as amounts directly assigned to each of IPL and WPL related to IPL’s and WPL’s current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In the “IPL” and “WPL” tables below, the OPEB plans costs (credits) represent costs (credits) for IPL and WPL employees, respectively.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$3.3			$3.9			$9.9			$11.8			$1.3			$1.5			$3.9			$4.7
Interest cost	13.6			12.3			40.6			36.8			2.4			2.1			7.1			6.3
Expected return on plan assets	(18.8		)	(18.5		)	(56.3		)	(55.5		)	(2.1		)	(2.0		)	(6.2		)	(6.0		)
Amortization of prior service cost (credit)	—			0.1			—			0.2			(3.0		)	(3.0		)	(8.9		)	(8.9		)
Amortization of actuarial loss	4.8			9.0			14.6			27.1			0.6			1.3			1.8			3.7
		$2.9			$6.8			$8.8			$20.4			($0.8	)		($0.1	)		($2.3	)		($0.2	)

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$1.8			$2.2			$5.4			$6.5			$0.6			$0.8			$1.8			$2.2
Interest cost	6.2			5.7			18.8			17.1			1.0			0.9			3.0			2.7
Expected return on plan assets	(8.9		)	(8.8		)	(26.8		)	(26.4		)	(1.5		)	(1.4		)	(4.4		)	(4.2		)
Amortization of prior service cost (credit)	—			—			—			0.1			(1.6		)	(1.6		)	(4.7		)	(4.7		)
Amortization of actuarial loss	2.0			3.8			6.0			11.4			0.3			0.6			0.8			2.0
		$1.1			$2.9			$3.4			$8.7			($1.2	)		($0.7	)		($3.5	)		($2.0	)

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2014			2013			2014			2013			2014			2013			2014			2013
Service cost		$1.3			$1.5			$3.7			$4.4			$0.5			$0.6			$1.5			$1.8
Interest cost	5.7			5.2			17.0			15.5			1.0			0.8			2.9			2.5
Expected return on plan assets	(8.1		)	(8.0		)	(24.3		)	(23.9		)	(0.4		)	(0.4		)	(1.0		)	(1.0		)
Amortization of prior service cost (credit)	—			0.1			0.2			0.3			(1.0		)	(0.9		)	(2.9		)	(2.9		)
Amortization of actuarial loss	2.3			4.2			6.9			12.8			0.3			0.5			0.9			1.5
		$1.2			$3.0			$3.5			$9.1			$0.4			$0.6			$1.4			$1.9

Schedule Of Qualified And Non-Qualified Pension And Other Postretirement Benefits Costs

The following table includes the allocated qualified and non-qualified pension and OPEB costs (credits) associated with Corporate Services employees providing services to IPL and WPL for the three and nine months ended September 30 (in millions):

	Pension Benefits Costs								OPEB Credits
	Three Months				Nine Months				Three Months						Nine Months
	2014		2013		2014		2013		2014			2013			2014			2013
IPL		$0.4		$0.4		$1.1		$1.4		$—			($0.1	)		($0.2	)		($0.2	)
WPL	0.3		0.4		0.8		1.1		(0.1		)	(0.1		)	(0.2		)	(0.2		)

Employees Participate In Defined Contribution Retirement Plans

For the three and nine months ended September 30, costs related to the 401(k) savings plans, which are partially based on the participants’ contributions, were as follows (in millions):

	Alliant Energy								IPL (a)								WPL (a)
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2014		2013		2014		2013		2014		2013		2014		2013		2014		2013		2014		2013
401(k) costs		$5.3		$4.7		$17.3		$14.7		$2.7		$2.4		$8.4		$7.6		$2.4		$2.1		$8.3		$6.5

(a) IPL’s and WPL’s amounts include allocated costs associated with Corporate Services employees.

Recognized Compensation Expense And Income Tax Benefits

A summary of compensation expense (including amounts allocated to IPL and WPL) and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2014		2013		2014		2013		2014		2013		2014		2013		2014		2013		2014		2013
Compensation expense		$1.2		$4.0		$7.4		$8.6		$0.6		$2.0		$4.0		$4.4		$0.5		$1.7		$3.1		$3.7
Income tax benefits	0.5		1.6		3.0		3.5		0.2		0.8		1.6		1.8		0.3		0.7		1.3		1.5