Condensed Consolidating Financial Information (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets
Fixed maturities, available-for-sale	$ 48,757.1	$ 50,939.3
Fixed maturities, trading	563.1	626.7
Equity securities, available-for-sale	110.5	136.5
Equity securities, trading	716.9	252.8
Mortgage loans	11,533.6	11,519.7
Real estate	1,271.6	1,180.3
Policy loans	859.7	864.9
Investment in unconsolidated entities	880.0	869.0
Other investments	2,064.4	2,422.1
Cash and cash equivalents	2,371.8	4,177.2	2,833.9	1,877.4
Accrued investment income	532.1	584.4
Premiums due and other receivables	1,241.0	1,084.4
Deferred acquisition costs	3,077.0	2,590.0	2,358.1	2,442.2
Property and equipment	500.7	464.2
Goodwill	1,100.3	543.4	482.3
Other intangibles	1,459.0	914.7
Separate account assets	130,018.4	81,653.8
Other assets	1,134.2	1,006.8
Total assets	208,191.4	161,830.2
Liabilities
Contractholder funds	35,958.3	37,786.5
Future policy benefits and claims	22,626.2	22,436.2
Other policyholder funds	758.9	716.4
Short-term debt	150.6	40.8
Long-term debt	2,601.4	2,671.3
Income taxes currently payable	5.2	15.3
Deferred income taxes	824.0	600.0
Separate account liabilities	130,018.4	81,653.8
Other liabilities	5,224.2	6,146.1
Total liabilities	198,167.2	152,066.4
Redeemable noncontrolling interest	247.2	60.4	22.2
Stockholders' equity
Common stock	4.6	4.5
Additional paid-in capital	9,798.9	9,730.9
Retained earnings (accumulated deficit)	5,405.4	4,862.0
Accumulated other comprehensive income	183.2	640.3
Treasury stock, at cost (164.1 million and 159.7 million shares in 2013 and 2012)	(5,708.0)	(5,554.4)
Total stockholders' equity attributable to Principal Financial Group, Inc.	9,684.2	9,683.4
Noncontrolling interest	92.8	20.0
Total stockholders' equity	9,777.0	9,703.4	9,306.2	9,246.8
Total liabilities and stockholders' equity	208,191.4	161,830.2
Principal Financial Group, Inc. Parent Only
Assets
Fixed maturities, trading		10.5
Investment in unconsolidated entities	11,956.2	11,853.3
Other investments	9.3	11.1
Cash and cash equivalents	131.5	207.1	226.7	370.9
Premiums due and other receivables		0.1
Other assets	59.2	78.0
Total assets	12,156.2	12,160.1
Liabilities
Long-term debt	2,448.8	2,448.6
Other liabilities	23.2	28.1
Total liabilities	2,472.0	2,476.7
Stockholders' equity
Common stock	4.6	4.5
Additional paid-in capital	9,798.9	9,730.9
Retained earnings (accumulated deficit)	5,405.4	4,862.0
Accumulated other comprehensive income	183.2	640.3
Treasury stock, at cost (164.1 million and 159.7 million shares in 2013 and 2012)	(5,708.0)	(5,554.4)
Total stockholders' equity attributable to Principal Financial Group, Inc.	9,684.2	9,683.4
Total stockholders' equity	9,684.2	9,683.4
Total liabilities and stockholders' equity	12,156.2	12,160.1
Principal Financial Services, Inc. Only
Assets
Investment in unconsolidated entities	11,647.6	10,632.1
Other investments	72.7	39.6
Cash and cash equivalents	688.7	612.5	702.4	519.7
Premiums due and other receivables	0.1	1,122.1
Other assets	94.8	51.0
Total assets	12,503.9	12,457.3
Liabilities
Income taxes currently payable	2.8	0.1
Other liabilities	544.9	603.9
Total liabilities	547.7	604.0
Stockholders' equity
Additional paid-in capital	9,163.7	9,393.8
Retained earnings (accumulated deficit)	2,578.2	1,783.4
Accumulated other comprehensive income	214.3	676.1
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,956.2	11,853.3
Total stockholders' equity	11,956.2	11,853.3
Total liabilities and stockholders' equity	12,503.9	12,457.3
Principal Life Insurance Company and Other Subsidiaries Combined
Assets
Fixed maturities, available-for-sale	48,757.1	50,939.3
Fixed maturities, trading	563.1	616.2
Equity securities, available-for-sale	110.5	136.5
Equity securities, trading	716.9	252.8
Mortgage loans	11,533.6	11,519.7
Real estate	1,271.6	1,180.3
Policy loans	859.7	864.9
Investment in unconsolidated entities	879.8	860.2
Other investments	1,982.5	2,371.4
Cash and cash equivalents	2,384.0	4,241.3	2,787.9	1,821.7
Accrued investment income	532.1	584.4
Premiums due and other receivables	2,330.4	2,206.7
Deferred acquisition costs	3,077.0	2,590.0
Property and equipment	500.7	464.2
Goodwill	1,100.3	543.4
Other intangibles	1,459.0	914.7
Separate account assets	130,018.4	81,653.8
Other assets	1,181.0	1,003.5
Total assets	209,257.7	162,943.3
Liabilities
Contractholder funds	35,958.3	37,786.5
Future policy benefits and claims	22,626.2	22,436.2
Other policyholder funds	758.9	716.4
Short-term debt	443.0	2,564.1
Long-term debt	1,236.9	222.7
Income taxes currently payable	44.7	47.2
Deferred income taxes	979.6	686.1
Separate account liabilities	130,018.4	81,653.8
Other liabilities	5,204.1	6,117.8
Total liabilities	197,270.1	152,230.8
Redeemable noncontrolling interest	247.2	60.4
Stockholders' equity
Common stock	17.8	17.8
Additional paid-in capital	9,057.1	8,287.7
Retained earnings (accumulated deficit)	2,387.2	1,666.7
Accumulated other comprehensive income	187.5	661.9
Treasury stock, at cost (164.1 million and 159.7 million shares in 2013 and 2012)	(2.0)	(2.0)
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,647.6	10,632.1
Noncontrolling interest	92.8	20.0
Total stockholders' equity	11,740.4	10,652.1
Total liabilities and stockholders' equity	209,257.7	162,943.3
Eliminations, Shelf Registration Debt Guarantor
Assets
Investment in unconsolidated entities	(23,603.6)	(22,476.6)
Other investments	(0.1)
Cash and cash equivalents	(832.4)	(883.7)	(883.1)	(834.9)
Premiums due and other receivables	(1,089.5)	(2,244.5)
Other assets	(200.8)	(125.7)
Total assets	(25,726.4)	(25,730.5)
Liabilities
Short-term debt	(292.4)	(2,523.3)
Long-term debt	(1,084.3)
Income taxes currently payable	(42.3)	(32.0)
Deferred income taxes	(155.6)	(86.1)
Other liabilities	(548.0)	(603.7)
Total liabilities	(2,122.6)	(3,245.1)
Stockholders' equity
Common stock	(17.8)	(17.8)
Additional paid-in capital	(18,220.8)	(17,681.5)
Retained earnings (accumulated deficit)	(4,965.4)	(3,450.1)
Accumulated other comprehensive income	(401.8)	(1,338.0)
Treasury stock, at cost (164.1 million and 159.7 million shares in 2013 and 2012)	2.0	2.0
Total stockholders' equity attributable to Principal Financial Group, Inc.	(23,603.8)	(22,485.4)
Total stockholders' equity	(23,603.8)	(22,485.4)
Total liabilities and stockholders' equity	(25,726.4)	(25,730.5)
Series A
Stockholders' equity
Preferred stock, value
Total stockholders' equity	0	0	0	0
Series B
Stockholders' equity
Preferred stock, value	0.1	0.1	0.1
Total stockholders' equity	0.1	0.1	0.1	0.1
Series B | Principal Financial Group, Inc. Parent Only
Stockholders' equity
Preferred stock, value	$ 0.1	$ 0.1