Condensed Consolidating Financial Information (Details 4) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Assets
Fixed maturities, available-for-sale	$ 49,627.5	$ 48,757.1
Fixed maturities, trading	609.4	563.1
Equity securities, available-for-sale	124.8	110.5
Equity securities, trading	807.6	716.9
Mortgage loans	11,744.9	11,533.6
Real estate	1,352.1	1,271.6
Policy loans	837.7	859.7
Investment in unconsolidated entities	873.4	880.0
Other investments	2,117.5	2,064.4
Cash and cash equivalents	1,270.8	2,371.8	1,707.1	4,177.2
Accrued investment income	545.1	532.1
Premiums due and other receivables	1,189.3	1,241.0
Deferred acquisition costs	2,985.4	3,077.0
Property and equipment	590.1	500.7
Goodwill	1,034.4	1,100.3
Other intangibles	1,361.4	1,459.0
Separate account assets	138,296.7	130,018.4
Other assets	1,054.7	1,134.2
Total assets	216,422.8	208,191.4
Liabilities
Contractholder funds	34,680.8	35,958.3
Future policy benefits and claims	23,399.5	22,626.2
Other policyholder funds	811.9	758.9
Short-term debt	126.3	150.6
Long-term debt	2,529.2	2,601.4
Income taxes currently payable	18.1	5.2
Deferred income taxes	1,150.6	824.0
Separate account liabilities	138,296.7	130,018.4
Other liabilities	4,984.6	5,224.2
Total liabilities	205,997.7	198,167.2
Redeemable noncontrolling interest	56.1	247.2	234.5	60.4
Stockholders' equity
Common stock	4.6	4.6
Additional paid-in capital	9,916.9	9,798.9
Retained earnings (accumulated deficit)	5,945.2	5,405.4
Accumulated other comprehensive income	380.1	183.2
Treasury stock, at cost (168.8 million and 164.1 million shares in 2014 and 2013)	(5,930.5)	(5,708.0)
Total stockholders' equity attributable to Principal Financial Group, Inc.	10,316.4	9,684.2
Noncontrolling interest	52.6	92.8
Total stockholders' equity	10,369.0	9,777.0	9,373.4	9,703.4
Total liabilities and stockholders' equity	216,422.8	208,191.4
Principal Financial Group, Inc. Parent Only
Assets
Investment in unconsolidated entities	12,583.2	11,956.2
Other investments	9.5	9.3
Cash and cash equivalents	150.7	131.5	50.8	207.1
Other assets	62.4	59.2
Total assets	12,805.8	12,156.2
Liabilities
Long-term debt	2,448.9	2,448.8
Other liabilities	40.5	23.2
Total liabilities	2,489.4	2,472.0
Stockholders' equity
Common stock	4.6	4.6
Additional paid-in capital	9,916.9	9,798.9
Retained earnings (accumulated deficit)	5,945.2	5,405.4
Accumulated other comprehensive income	380.1	183.2
Treasury stock, at cost (168.8 million and 164.1 million shares in 2014 and 2013)	(5,930.5)	(5,708.0)
Total stockholders' equity attributable to Principal Financial Group, Inc.	10,316.4	9,684.2
Total stockholders' equity	10,316.4	9,684.2
Total liabilities and stockholders' equity	12,805.8	12,156.2
Principal Financial Services, Inc. Only
Assets
Investment in unconsolidated entities	12,103.7	11,647.6
Other investments	179.0	72.7
Cash and cash equivalents	413.0	688.7	491.0	612.5
Premiums due and other receivables	0.6	0.1
Other assets	152.9	94.8
Total assets	12,849.2	12,503.9
Liabilities
Income taxes currently payable	16.0	2.8
Other liabilities	250.0	544.9
Total liabilities	266.0	547.7
Stockholders' equity
Additional paid-in capital	9,191.9	9,163.7
Retained earnings (accumulated deficit)	2,983.4	2,578.2
Accumulated other comprehensive income	407.9	214.3
Total stockholders' equity attributable to Principal Financial Group, Inc.	12,583.2	11,956.2
Total stockholders' equity	12,583.2	11,956.2
Total liabilities and stockholders' equity	12,849.2	12,503.9
Principal Life Insurance Company and Other Subsidiaries Combined
Assets
Fixed maturities, available-for-sale	49,627.5	48,757.1
Fixed maturities, trading	609.4	563.1
Equity securities, available-for-sale	124.8	110.5
Equity securities, trading	807.6	716.9
Mortgage loans	11,744.9	11,533.6
Real estate	1,352.1	1,271.6
Policy loans	837.7	859.7
Investment in unconsolidated entities	841.4	879.8
Other investments	1,929.0	1,982.5
Cash and cash equivalents	1,196.4	2,384.0	1,822.1	4,241.3
Accrued investment income	545.1	532.1
Premiums due and other receivables	1,188.3	2,330.4
Deferred acquisition costs	2,985.4	3,077.0
Property and equipment	590.1	500.7
Goodwill	1,034.4	1,100.3
Other intangibles	1,361.4	1,459.0
Separate account assets	138,296.7	130,018.4
Other assets	1,136.6	1,181.0
Total assets	216,208.8	209,257.7
Liabilities
Contractholder funds	34,680.8	35,958.3
Future policy benefits and claims	23,399.5	22,626.2
Other policyholder funds	811.9	758.9
Short-term debt	325.4	443.0
Long-term debt	80.3	1,236.9
Income taxes currently payable	83.9	44.7
Deferred income taxes	1,361.6	979.6
Separate account liabilities	138,296.7	130,018.4
Other liabilities	4,956.3	5,204.1
Total liabilities	203,996.4	197,270.1
Redeemable noncontrolling interest	56.1	247.2
Stockholders' equity
Common stock	17.8	17.8
Additional paid-in capital	9,284.2	9,057.1
Retained earnings (accumulated deficit)	2,450.2	2,387.2
Accumulated other comprehensive income	353.5	187.5
Treasury stock, at cost (168.8 million and 164.1 million shares in 2014 and 2013)	(2.0)	(2.0)
Total stockholders' equity attributable to Principal Financial Group, Inc.	12,103.7	11,647.6
Noncontrolling interest	52.6	92.8
Total stockholders' equity	12,156.3	11,740.4
Total liabilities and stockholders' equity	216,208.8	209,257.7
Eliminations, Shelf Registration Debt Guarantor
Assets
Investment in unconsolidated entities	(24,654.9)	(23,603.6)
Other investments		(0.1)
Cash and cash equivalents	(489.3)	(832.4)	(656.8)	(883.7)
Premiums due and other receivables	0.4	(1,089.5)
Other assets	(297.2)	(200.8)
Total assets	(25,441.0)	(25,726.4)
Liabilities
Short-term debt	(199.1)	(292.4)
Long-term debt		(1,084.3)
Income taxes currently payable	(81.8)	(42.3)
Deferred income taxes	(211.0)	(155.6)
Other liabilities	(262.2)	(548.0)
Total liabilities	(754.1)	(2,122.6)
Stockholders' equity
Common stock	(17.8)	(17.8)
Additional paid-in capital	(18,476.1)	(18,220.8)
Retained earnings (accumulated deficit)	(5,433.6)	(4,965.4)
Accumulated other comprehensive income	(761.4)	(401.8)
Treasury stock, at cost (168.8 million and 164.1 million shares in 2014 and 2013)	2.0	2.0
Total stockholders' equity attributable to Principal Financial Group, Inc.	(24,686.9)	(23,603.8)
Total stockholders' equity	(24,686.9)	(23,603.8)
Total liabilities and stockholders' equity	(25,441.0)	(25,726.4)
Series A
Stockholders' equity
Preferred stock, value
Total stockholders' equity	0	0	0	0
Series A | Principal Financial Group, Inc. Parent Only
Stockholders' equity
Preferred stock, value
Series B
Stockholders' equity
Preferred stock, value	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