Employee and Agent Benefits (Tables)

12 Months Ended

Dec. 31, 2017

Defined Benefit Plans and Other Postretirement Benefit Plans

Obligations and Funded Status (Table)

	Pension benefits						Other postretirement benefits
	December 31,						December 31,
	2017			2016			2017			2016
	(in millions)
Change in benefit obligation
Benefit obligation at beginning of year	$	(3,056.2	)	$	(3,052.2	)	$	(109.8	)	$	(165.7	)
Service cost		(67.1	)		(65.0	)		(0.1	)		(2.1	)
Interest cost		(124.4	)		(134.9	)		(3.9	)		(6.2	)
Actuarial gain (loss)		(268.0	)		(39.3	)		(1.7	)		5.8
Participant contribution		—			—			(3.5	)		(3.9	)
Benefits paid		109.0			235.2			9.9			10.7
Plan amendments		23.1			—			—			51.6
Benefit obligation at end of year	$	(3,383.6	)	$	(3,056.2	)	$	(109.1	)	$	(109.8	)
Change in plan assets
Fair value of plan assets at beginning of year	$	2,190.8		$	2,166.3		$	628.6		$	627.0
Actual return on plan assets		368.3			181.6			73.9			8.0
Employer contribution		92.1			78.1			0.7			0.4
Participant contributions		—			—			3.5			3.9
Benefits paid		(109.0	)		(235.2	)		(9.9	)		(10.7	)
Fair value of plan assets at end of year	$	2,542.2		$	2,190.8		$	696.8		$	628.6
Amount recognized in statement of financial position
Other assets	$	—		$	—		$	589.5		$	520.8
Other liabilities		(841.4	)		(865.4	)		(1.8	)		(2.0	)
Total	$	(841.4	)	$	(865.4	)	$	587.7		$	518.8
Amount recognized in accumulated other comprehensive (income) loss
Total net actuarial (gain) loss	$	682.8		$	706.9		$	(34.7	)	$	10.0
Prior service benefit		(23.7	)		(2.9	)		(24.1	)		(58.7	)
Pre-tax accumulated other comprehensive (income) loss	$	659.1		$	704.0		$	(58.8	)	$	(48.7	)

Components of Net Periodic Benefit Cost (Income) (Table)

	Pension benefits									Other postretirement benefits
	For the year ended December 31,
	2017			2016			2015			2017			2016			2015
	(in millions)
Service cost	$	67.1		$	65.0		$	63.2		$	0.1		$	2.1		$	2.0
Interest cost		124.4			134.9			120.3			3.9			6.2			6.6
Expected return on plan assets		(144.2	)		(155.0	)		(160.6	)		(27.5	)		(32.6	)		(33.9	)
Amortization of prior service benefit		(2.3	)		(2.2	)		(1.9	)		(34.6	)		(25.9	)		(18.5	)
Recognized net actuarial (gain) loss		68.0			77.0			102.4			—			0.2			(0.8	)
Plan amendments		—			—			—			—			—			5.8
Net periodic benefit cost (income)	$	113.0		$	119.7		$	123.4		$	(58.1	)	$	(50.0	)	$	(38.8	)

Amounts Recognized in Net Periodic Benefit Cost and Accumulated Other Comprehensive (Income) Loss (Table)

	Pension benefits						Other postretirement benefits
	For the year ended December 31,
	2017			2016			2017			2016
	(in millions)
Other changes recognized in accumulated other comprehensive income
Net actuarial (gain) loss	$	43.9		$	12.7		$	(44.7	)	$	18.8
Prior service benefit		(23.1	)		—			—			—
Amortization of net loss		(68.0	)		(77.0	)		—			(0.2	)
Amortization of prior service benefit		2.3			2.2			34.6			25.9
Plan amendments		—			—			—			(51.6	)
Total recognized in pre-tax accumulated other comprehensive income	$	(44.9	)	$	(62.1	)	$	(10.1	)	$	(7.1	)
Total recognized in net periodic benefit cost and pre-tax accumulated other comprehensive (income) loss	$	68.1		$	57.6		$	(68.2	)	$	(57.1	)

Weighted-Average Assumptions Used to Determine Benefit Obligations (Table)

	Pension benefits
	For the year ended December 31,
	2017			2016
Discount rate		3.60	%		4.15	%
Rate of compensation increase:
Cash balance benefit		4.96	%		5.02	%
Traditional benefit		2.66	%		2.70	%

	Other postretirement benefits
	For the year ended December 31,
	2017			2016
Discount rate		3.35	%		3.75	%
Rate of compensation increase		2.39	%		2.44	%

Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Table)

	Pension benefits
	For the year ended December 31,
	2017			2016			2015
Discount rate		4.15	%		4.50	%		4.00	%
Expected long-term return on plan assets		6.70	%		7.20	%		7.20	%
Rate of compensation increase:
Cash balance benefit		5.02	%		5.24	%		5.25	%
Traditional benefit		2.70	%		2.98	%		3.02	%

	Other postretirement benefits
	For the year ended December 31,
	2017			2016			2015
Discount rate (1)		3.75	%		3.35	%		4.00	%
Expected long-term return on plan assets		4.40	%		5.24	%		5.36	%
Rate of compensation increase		2.44	%		4.82	%		4.82	%

(1) The funded statuses of the OPEB plans for which subsidies were eliminated in 2016 were remeasured as of October 31, 2016, and a portion of the impact was reflected in the 2016 net periodic postretirement benefit cost. A discount rate of 4.15% was used until the remeasurement date at which time a discount rate of 3.35% was used.

Assumed Health Care Cost Trend Rates (Table)

	December 31,
	2017			2016
Health care cost trend rate assumed for next year under age 65		7.0	%		7.0	%
Health care cost trend rate assumed for next year age 65 and over		7.0	%		6.0	%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)		4.5	%		4.5	%
Year that the rate reaches the ultimate trend rate (under age 65)		2024			2023
Year that the rate reaches the ultimate trend rate (65 and older)		2024			2021

Effects of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Table)

	1-percentage point increase			1-percentage point decrease
	(in millions)
Effect on total of service cost and interest cost components	$	0.1		$	(0.1	)
Effect on accumulated postretirement benefit obligation		(1.5	)		1.4

Estimated Future Benefit Payments (Table)

	Pension benefits		Other postretirement benefits (gross benefit payments, including prescription drug benefits)
	(in millions)
Year ending December 31:
2018	$	127.5	$	13.1
2019		129.4		13.6
2020		139.5		12.5
2021		145.3		11.6
2022		154.5		10.8
2023-2027		882.6		9.9

Defined Benefit Pension Plans Supplemental Information (Table)

	For the year ended December 31,
	2017									2016
	Qualified Plan			Nonqualified Plan			Total			Qualified Plan			Nonqualified Plan			Total
	(in millions)
Amount recognized in statement of financial position
Other assets	$	—		$	—		$	—		$	—		$	—		$	—
Other liabilities		(340.0	)		(501.4	)		(841.4	)		(410.0	)		(455.4	)		(865.4	)
Total	$	(340.0	)	$	(501.4	)	$	(841.4	)	$	(410.0	)	$	(455.4	)	$	(865.4	)
Amount recognized in accumulated other comprehensive loss
Total net actuarial loss	$	516.4		$	166.4		$	682.8		$	587.5		$	119.4		$	706.9
Prior service benefit		(12.5	)		(11.2	)		(23.7	)		(1.6	)		(1.3	)		(2.9	)
Pre-tax accumulated other comprehensive loss	$	503.9		$	155.2		$	659.1		$	585.9		$	118.1		$	704.0
Components of net periodic benefit cost
Service cost	$	60.3		$	6.8		$	67.1		$	58.1		$	6.9		$	65.0
Interest cost		106.0			18.4			124.4			115.9			19.0			134.9
Expected return on plan assets		(144.2	)		—			(144.2	)		(155.0	)		—			(155.0	)
Amortization of prior service benefit		(1.2	)		(1.1	)		(2.3	)		(1.1	)		(1.1	)		(2.2	)
Recognized net actuarial loss		59.2			8.8			68.0			69.5			7.5			77.0
Net periodic benefit cost	$	80.1		$	32.9		$	113.0		$	87.4		$	32.3		$	119.7
Other changes recognized in accumulated other comprehensive (income) loss
Net actuarial (gain) loss	$	(11.9	)	$	55.8		$	43.9		$	(2.0	)	$	14.7		$	12.7
Prior service benefit		(12.2	)		(10.9	)		(23.1	)		—			—			—
Amortization of net loss		(59.2	)		(8.8	)		(68.0	)		(69.5	)		(7.5	)		(77.0	)
Amortization of prior service benefit		1.2			1.1			2.3			1.1			1.1			2.2
Total recognized in pre-tax accumulated other
comprehensive (income) loss	$	(82.1	)	$	37.2		$	(44.9	)	$	(70.4	)	$	8.3		$	(62.1	)
Total recognized in net periodic benefit cost and pre-tax accumulated other comprehensive (income) loss	$	(2.0	)	$	70.1		$	68.1		$	17.0		$	40.6		$	57.6

Pension benefits

Defined Benefit Plans and Other Postretirement Benefit Plans

Accumulated Benefit Obligation in Excess of Plan Assets (Table)

	December 31,
	2017		2016
	(in millions)
Projected benefit obligation	$	3,383.6	$	3,056.2
Accumulated benefit obligation		3,139.3		2,821.1
Fair value of plan assets		2,542.2		2,190.8

Fair Value of Plan Assets (Table)

	December 31, 2017
						Fair value hierarchy level
	Assets measured at fair value			Amount measured at net asset value
						Level 1		Level 2			Level 3
	(in millions)
Asset category
Pooled separate account investments:
U.S. large cap equity portfolios (1)	$	651.2		$	—	$	—	$	651.2		$	—
U.S. small/mid cap equity portfolios (2)		112.2			—		—		112.2			—
Balanced asset portfolios (3)		128.4			—		—		128.4			—
International equity portfolios (4)		325.8			—		—		325.8			—
Real estate investment portfolios (6)		126.2			—		—		126.2			—
Single client separate account investments:
Fixed income securities:
U.S. government and agencies		292.7			—		292.7		—			—
States and political subdivisions		16.9			—		—		16.9			—
Corporate		745.2			—		—		745.2			—
Commercial mortgage-backed securities		21.3			—		—		21.3			—
Other debt obligations		3.4			—		—		3.4			—
Hedge funds (7)		120.4			120.4		—		—			—
Pooled separate account investment (8)		4.6			—		—		4.6			—
Other (9)		(6.1	)		—		0.8		(6.9	)		—
Total	$	2,542.2		$	120.4	$	293.5	$	2,128.3		$	—

	December 31, 2016
					Fair value hierarchy level
	Assets measured at fair value		Amount measured at net asset value
					Level 1		Level 2		Level 3
	(in millions)
Asset category
Pooled separate account investments:
U.S. large cap equity portfolios (1)	$	772.7	$	—	$	—	$	772.7	$	—
U.S. small/mid cap equity portfolios (2)		153.0		—		—		153.0		—
Balanced asset portfolios (3)		123.0		—		—		123.0		—
International equity portfolios (4)		294.3		—		—		294.3		—
Fixed income security portfolios (5)		13.4		—		—		13.4		—
Real estate investment portfolios (6)		129.4		—		—		129.4		—
Single client separate account investments:
Fixed income securities:
U.S. government and agencies		226.9		—		226.9		—		—
Corporate		444.8		—		—		444.8		—
Commercial mortgage-backed securities		17.8		—		—		17.8		—
Other debt obligations		2.7		—		—		2.7		—
Pooled separate account investment (8)		6.9		—		—		6.9		—
Other (9)		5.9		—		—		5.9		—
Total	$	2,190.8	$	—	$	226.9	$	1,963.9	$	—

(1)	The portfolios invest primarily in publicly traded equity securities of large U.S. companies.
(2)	The portfolios invest primarily in publicly traded equity securities of mid-sized and small U.S. companies.
(3)	The portfolios are a combination of underlying fixed income and equity investment options. These investment options may include balanced, asset allocation, target-date and target-risk investment options. Although typically lower risk than investment options that invest solely in equities, all investment options in this category have the potential to lose value.
(4)	The portfolios invest primarily in publicly traded equity securities of non-U.S. companies.
(5)	The portfolios invest in various fixed income securities, primarily of U.S. origin. These include, but are not limited to, corporate bonds, residential mortgage-backed securities, commercial mortgage-backed securities, U.S. Treasury securities, agency securities, asset-backed securities and collateralized mortgage obligations.
(6)	The portfolio invests primarily in U.S. commercial real estate properties through a separate account.
(7)	The hedge funds have varying investment strategies that also have a variety of redemption terms and conditions. We do not have unfunded commitments associated with these hedge funds.
(8)	The single client separate accounts invest in a money market pooled separate account.
(9)	Includes cash and net (payables)/receivables for the single client separate accounts.

Target Asset Allocation (Table)

Asset category	Target allocation
Fixed income security portfolios	25% - 80%
Equity portfolios	5% - 60%
Real estate investment portfolios	10%
Altenatives	5%

Other postretirement benefits

Defined Benefit Plans and Other Postretirement Benefit Plans

Accumulated Benefit Obligation in Excess of Plan Assets (Table)

	December 31,
	2017		2016
	(in millions)
Accumulated postretirement benefit obligation	$	2.2	$	2.6
Fair value of plan assets		0.4		0.6

Fair Value of Plan Assets (Table)

	December 31, 2017
			Fair value hierarchy level
	Assets measured at fair value
			Level 1		Level 2		Level 3
	(in millions)
Asset category
Cash and cash equivalents	$	0.3	$	0.3	$	—	$	—
Fixed income security portfolios:
Fixed income investment funds (1)		209.8		177.7		32.1		—
U.S. equity portfolios (2)		159.4		108.5		50.9		—
International equity portfolios (3)		67.8		57.7		10.1		—
Alternative mutual fund portfolios (4)		251.4		251.4		—		—
Real estate mutual fund (5)		8.1		8.1		—		—
Total	$	696.8	$	603.7	$	93.1	$	—

	December 31, 2016
			Fair value hierarchy level
	Assets measured at fair value
			Level 1		Level 2		Level 3
	(in millions)
Asset category
Cash and cash equivalents	$	1.2	$	1.2	$	—	$	—
Fixed income security portfolios:
Fixed income investment funds (1)		195.5		164.3		31.2		—
U.S. equity portfolios (2)		145.5		103.2		42.3		—
International equity portfolios (3)		51.2		43.2		8.0		—
Alternative mutual fund portfolios (4)		227.5		227.5		—		—
Real estate mutual fund (5)		7.7		7.7		—		—
Total	$	628.6	$	547.1	$	81.5	$	—

(1)	The portfolios invest in various fixed income securities, primarily of U.S. origin. These include, but are not limited to, corporate bonds, residential mortgage-backed securities, commercial mortgage-backed securities, U.S. Treasury securities, agency securities, asset-backed securities and collateralized mortgage obligations.
(2)	The portfolios invest primarily in publicly traded equity securities of large U.S. companies.
(3)	The portfolios invest primarily in publicly traded equity securities of non-U.S. companies.
(4)	The portfolios invest primarily in equities, corporate bonds, foreign currencies, convertible securities and derivatives.
(5)	The mutual fund invests primarily in U.S. commercial real estate properties.

Reconciliation of Plan Assets Measured at Fair Value Using Significant Unobservable Inputs (Table)

	For the year ended December 31, 2016
			Actual return gains (losses) on plan assets
															Ending asset balance as of December 31, 2016
	Beginning asset balance as of December 31, 2015		Relating to assets still held at the reporting date			Relating to assets sold during the period			Net purchases, sales, and settlements		Transfers into Level 3		Transfers out of Level 3
	(in millions)
Asset category
Principal Life general account investment	$	33.5	$	(1.7	)	$	(33.6	)	$	1.8	$	—	$	—	$	—

	For the year ended December 31, 2015
			Actual return gains (losses) on plan assets
														Ending assets balance as of December 31, 2015
	Beginning assets balance as of December 31, 2014		Relating to assets still held at the reporting date		Relating to assets sold during the period		Net purchases, sales, and settlements			Transfers into Level 3		Transfers out of Level 3
	(in millions)
Asset category
Principal Life general account investment	$	36.3	$	0.2	$	—	$	(3.0	)	$	—	$	—	$	33.5

Target Asset Allocation (Table)

Asset category	Target allocation
U.S. equity portfolios		24	%
International equity portfolios		15	%
Fixed income security portfolios		32	%
Alternatives		24	%
Real estate		5	%