Condensed Consolidating Financial Information (Details 4) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Assets
Fixed maturities, available-for-sale	$ 50,048.1	$ 48,757.1
Fixed maturities, trading	575.3	563.1
Equity securities, available-for-sale	136.1	110.5
Equity securities, trading	724.2	716.9
Mortgage loans	11,478.4	11,533.6
Real estate	1,390.8	1,271.6
Policy loans	843.8	859.7
Investment in unconsolidated entities	889.0	880.0
Other investments	2,021.4	2,064.4
Cash and cash equivalents	1,393.1	2,371.8	1,661.2	4,177.2
Accrued investment income	540.4	532.1
Premiums due and other receivables	1,199.3	1,241.0
Deferred acquisition costs	3,045.6	3,077.0
Property and equipment	546.0	500.7
Goodwill	1,075.2	1,100.3
Other intangibles	1,421.8	1,459.0
Separate account assets	132,804.6	130,018.4
Other assets	1,060.8	1,134.2
Total assets	211,193.9	208,191.4
Liabilities
Contractholder funds	35,736.3	35,958.3
Future policy benefits and claims	23,026.2	22,626.2
Other policyholder funds	791.6	758.9
Short-term debt	148.8	150.6
Long-term debt	2,516.0	2,601.4
Income taxes currently payable	6.4	5.2
Deferred income taxes	889.7	824.0
Separate account liabilities	132,804.6	130,018.4
Other liabilities	4,936.2	5,224.2
Total liabilities	200,855.8	198,167.2
Redeemable noncontrolling interest	280.2	247.2	58.9	60.4
Stockholders' equity
Common stock	4.6	4.6
Additional paid-in capital	9,813.1	9,798.9
Retained earnings (accumulated deficit)	5,605.3	5,405.4
Accumulated other comprehensive income	361.8	183.2
Treasury stock, at cost (166.1 million and 164.1 million shares in 2014 and 2013)	(5,797.0)	(5,708.0)
Total stockholders' equity attributable to Principal Financial Group, Inc.	9,987.9	9,684.2
Noncontrolling interest	70.0	92.8
Total stockholders' equity	10,057.9	9,777.0	9,826.6	9,703.4
Total liabilities and stockholders' equity	211,193.9	208,191.4
Principal Financial Group, Inc. Parent Only
Assets
Investment in unconsolidated entities	12,326.6	11,956.2
Other investments	9.2	9.3
Cash and cash equivalents	91.4	131.5	112.7	207.1
Accrued investment income	0.1
Other assets	59.1	59.2
Total assets	12,486.4	12,156.2
Liabilities
Long-term debt	2,448.8	2,448.8
Income taxes currently payable	(0.3)
Deferred income taxes	0.3
Other liabilities	49.7	23.2
Total liabilities	2,498.5	2,472.0
Stockholders' equity
Common stock	4.6	4.6
Additional paid-in capital	9,813.1	9,798.9
Retained earnings (accumulated deficit)	5,605.3	5,405.4
Accumulated other comprehensive income	361.8	183.2
Treasury stock, at cost (166.1 million and 164.1 million shares in 2014 and 2013)	(5,797.0)	(5,708.0)
Total stockholders' equity attributable to Principal Financial Group, Inc.	9,987.9	9,684.2
Total stockholders' equity	9,987.9	9,684.2
Total liabilities and stockholders' equity	12,486.4	12,156.2
Principal Financial Services, Inc. Only
Assets
Investment in unconsolidated entities	11,895.7	11,647.6
Other investments	100.9	72.7
Cash and cash equivalents	573.7	688.7	584.8	612.5
Premiums due and other receivables	0.4	0.1
Other assets	96.0	94.8
Total assets	12,666.7	12,503.9
Liabilities
Income taxes currently payable	19.4	2.8
Deferred income taxes	(27.4)
Other liabilities	348.1	544.9
Total liabilities	340.1	547.7
Stockholders' equity
Additional paid-in capital	9,144.5	9,163.7
Retained earnings (accumulated deficit)	2,790.4	2,578.2
Accumulated other comprehensive income	391.7	214.3
Total stockholders' equity attributable to Principal Financial Group, Inc.	12,326.6	11,956.2
Total stockholders' equity	12,326.6	11,956.2
Total liabilities and stockholders' equity	12,666.7	12,503.9
Principal Life Insurance Company and Other Subsidiaries Combined
Assets
Fixed maturities, available-for-sale	50,048.1	48,757.1
Fixed maturities, trading	575.3	563.1
Equity securities, available-for-sale	136.1	110.5
Equity securities, trading	724.2	716.9
Mortgage loans	11,478.4	11,533.6
Real estate	1,390.8	1,271.6
Policy loans	843.8	859.7
Investment in unconsolidated entities	859.4	879.8
Other investments	1,911.3	1,982.5
Cash and cash equivalents	1,367.3	2,384.0	1,755.9	4,241.3
Accrued investment income	540.3	532.1
Premiums due and other receivables	1,198.2	2,330.4
Deferred acquisition costs	3,045.6	3,077.0
Property and equipment	546.0	500.7
Goodwill	1,075.2	1,100.3
Other intangibles	1,421.8	1,459.0
Separate account assets	132,804.6	130,018.4
Other assets	1,125.0	1,181.0
Total assets	211,091.4	209,257.7
Liabilities
Contractholder funds	35,736.3	35,958.3
Future policy benefits and claims	23,026.2	22,626.2
Other policyholder funds	791.6	758.9
Short-term debt	399.7	443.0
Long-term debt	67.2	1,236.9
Income taxes currently payable	50.1	44.7
Deferred income taxes	1,069.8	979.6
Separate account liabilities	132,804.6	130,018.4
Other liabilities	4,900.0	5,204.1
Total liabilities	198,845.5	197,270.1
Redeemable noncontrolling interest	280.2	247.2
Stockholders' equity
Common stock	17.8	17.8
Additional paid-in capital	9,237.7	9,057.1
Retained earnings (accumulated deficit)	2,290.9	2,387.2
Accumulated other comprehensive income	351.3	187.5
Treasury stock, at cost (166.1 million and 164.1 million shares in 2014 and 2013)	(2.0)	(2.0)
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,895.7	11,647.6
Noncontrolling interest	70.0	92.8
Total stockholders' equity	11,965.7	11,740.4
Total liabilities and stockholders' equity	211,091.4	209,257.7
Eliminations, Shelf Registration Debt Guarantor
Assets
Investment in unconsolidated entities	(24,192.7)	(23,603.6)
Other investments		(0.1)
Cash and cash equivalents	(639.3)	(832.4)	(792.2)	(883.7)
Premiums due and other receivables	0.7	(1,089.5)
Other assets	(219.3)	(200.8)
Total assets	(25,050.6)	(25,726.4)
Liabilities
Short-term debt	(250.9)	(292.4)
Long-term debt		(1,084.3)
Income taxes currently payable	(62.8)	(42.3)
Deferred income taxes	(153.0)	(155.6)
Other liabilities	(361.6)	(548.0)
Total liabilities	(828.3)	(2,122.6)
Stockholders' equity
Common stock	(17.8)	(17.8)
Additional paid-in capital	(18,382.2)	(18,220.8)
Retained earnings (accumulated deficit)	(5,081.3)	(4,965.4)
Accumulated other comprehensive income	(743.0)	(401.8)
Treasury stock, at cost (166.1 million and 164.1 million shares in 2014 and 2013)	2.0	2.0
Total stockholders' equity attributable to Principal Financial Group, Inc.	(24,222.3)	(23,603.8)
Total stockholders' equity	(24,222.3)	(23,603.8)
Total liabilities and stockholders' equity	(25,050.6)	(25,726.4)
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
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