Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues
Premiums and other considerations	$ 1,158.2	$ 672.7	$ 2,519.3	$ 2,221.7
Fees and other revenues	675.0	636.4	1,909.1	1,892.6
Net investment income (loss)	783.8	815.2	2,409.6	2,548.6
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	122.1	16.9	176.4	99.6
Total other-than-temporary impairment losses on available-for-sale securities	(43.6)	(12.7)	(126.4)	(67.6)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	9.2	(34.9)	31.2	(83.0)
Net impairment losses on available-for-sale securities	(34.4)	(47.6)	(95.2)	(150.6)
Net realized capital gains (losses)	87.7	(30.7)	81.2	(51.0)
Total revenues	2,704.7	2,093.6	6,919.2	6,611.9
Expenses
Benefits, claims and settlement expenses	1,647.0	1,114.9	3,969.5	3,497.7
Dividends to policyholders	49.7	52.2	149.5	158.7
Operating expenses	826.6	775.4	2,106.7	2,232.7
Total expenses	2,523.3	1,942.5	6,225.7	5,889.1
Income (loss) before income taxes	181.4	151.1	693.5	722.8
Income taxes (benefits)	(9.9)	76.6	99.2	190.3
Net income (loss)	191.3	74.5	594.3	532.5
Net income (loss) attributable to noncontrolling interest	3.4	(5.6)	15.3	36.6
Net income (loss) attributable to Principal Financial Group, Inc.	187.9	80.1	579.0	495.9
Preferred stock dividends	8.2	8.2	24.7	24.7
Net income (loss) available to common stockholders	$ 179.7	$ 71.9	$ 554.3	$ 471.2
Earnings per common share
Basic earnings per common share (in dollars per share)	$ 0.61	$ 0.23	$ 1.86	$ 1.48
Diluted earnings per common share (in dollars per share)	$ 0.60	$ 0.23	$ 1.84	$ 1.47