Condensed Consolidating Financial Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Revenues
Premiums and other considerations	$ 803.6	$ 694.7
Fees and other revenues	829.7	733.6
Net investment income (loss)	844.7	789.3
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	19.8	(26.4)
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	10.9	(44.7)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(30.1)	20.2
Net impairment losses on available-for-sale securities	(19.2)	(24.5)
Net realized capital gains (losses)	0.6	(50.9)
Total revenues	2,478.6	2,166.7
Expenses
Benefits, claims and settlement expenses	1,227.5	1,094.5
Dividends to policyholders	45.7	48.3
Operating expenses	829.0	795.7
Total expenses	2,102.2	1,938.5
Income (loss) before income taxes	376.4	228.2
Income taxes (benefits)	52.3	38.2
Net income (loss)	324.1	190.0
Net income (loss) attributable to noncontrolling interest	22.2	3.5
Net income (loss) attributable to Principal Financial Group, Inc.	301.9	186.5
Preferred stock dividends	8.2	8.2
Net income (loss) available to common stockholders	293.7	178.3
Net income (loss)	324.1	190.0
Other comprehensive income (loss)	176.6	(20.4)
Comprehensive income (loss)	500.7	169.6
Principal Financial Group, Inc. Parent Only
Revenues
Net investment income (loss)	0.1
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities		6.3
Net realized capital gains (losses)		6.3
Total revenues	0.1	6.3
Expenses
Operating expenses	35.6	35.0
Total expenses	35.6	35.0
Income (loss) before income taxes	(35.5)	(28.7)
Income taxes (benefits)	(14.2)	(11.5)
Equity in the net income (loss) of subsidiaries	323.2	203.7
Net income (loss)	301.9	186.5
Net income (loss) attributable to Principal Financial Group, Inc.	301.9	186.5
Preferred stock dividends	8.2	8.2
Net income (loss) available to common stockholders	293.7	178.3
Net income (loss)	301.9	186.5
Other comprehensive income (loss)	111.1	(81.3)
Comprehensive income (loss)	413.0	105.2
Principal Life Insurance Company Only
Revenues
Premiums and other considerations	705.7	605.1
Fees and other revenues	458.7	413.2
Net investment income (loss)	576.3	602.0
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	244.3	(304.9)
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	10.9	(44.2)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(29.3)	20.1
Net impairment losses on available-for-sale securities	(18.4)	(24.1)
Net realized capital gains (losses)	225.9	(329.0)
Total revenues	1,966.6	1,291.3
Expenses
Benefits, claims and settlement expenses	1,057.9	950.3
Dividends to policyholders	45.7	48.3
Operating expenses	499.8	470.7
Total expenses	1,603.4	1,469.3
Income (loss) before income taxes	363.2	(178.0)
Income taxes (benefits)	74.3	(88.4)
Equity in the net income (loss) of subsidiaries	(53.6)	240.6
Net income (loss)	235.3	151.0
Net income (loss) attributable to Principal Financial Group, Inc.	235.3	151.0
Net income (loss) available to common stockholders	235.3	151.0
Net income (loss)	235.3	151.0
Other comprehensive income (loss)	188.3	(65.9)
Comprehensive income (loss)	423.6	85.1
Principal Financial Services, Inc. and Other Subsidiaries Combined
Revenues
Premiums and other considerations	97.9	89.6
Fees and other revenues	471.3	404.3
Net investment income (loss)	339.1	179.9
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	(224.5)	272.1
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities		(0.5)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(0.8)	0.1
Net impairment losses on available-for-sale securities	(0.8)	(0.4)
Net realized capital gains (losses)	(225.3)	271.7
Total revenues	683.0	945.5
Expenses
Benefits, claims and settlement expenses	172.4	147.3
Operating expenses	374.8	362.5
Total expenses	547.2	509.8
Income (loss) before income taxes	135.8	435.7
Income taxes (benefits)	(7.7)	138.2
Equity in the net income (loss) of subsidiaries	201.9	(90.3)
Net income (loss)	345.4	207.2
Net income (loss) attributable to noncontrolling interest	22.2	3.5
Net income (loss) attributable to Principal Financial Group, Inc.	323.2	203.7
Net income (loss) available to common stockholders	323.2	203.7
Net income (loss)	345.4	207.2
Other comprehensive income (loss)	255.9	59.7
Comprehensive income (loss)	601.3	266.9
Eliminations, Notes Guarantor
Revenues
Fees and other revenues	(100.3)	(83.9)
Net investment income (loss)	(70.8)	7.4
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities		0.1
Net realized capital gains (losses)		0.1
Total revenues	(171.1)	(76.4)
Expenses
Benefits, claims and settlement expenses	(2.8)	(3.1)
Operating expenses	(81.2)	(72.5)
Total expenses	(84.0)	(75.6)
Income (loss) before income taxes	(87.1)	(0.8)
Income taxes (benefits)	(0.1)	(0.1)
Equity in the net income (loss) of subsidiaries	(471.5)	(354.0)
Net income (loss)	(558.5)	(354.7)
Net income (loss) attributable to Principal Financial Group, Inc.	(558.5)	(354.7)
Net income (loss) available to common stockholders	(558.5)	(354.7)
Net income (loss)	(558.5)	(354.7)
Other comprehensive income (loss)	(378.7)	67.1
Comprehensive income (loss)	$ (937.2)	$ (287.6)