Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues
Premiums and other considerations	$ 2,126.1	$ 1,002.7	$ 4,826.8	$ 3,561.1
Fees and other revenues	987.1	915.0	2,882.8	2,687.7
Net investment income (loss)	838.0	856.1	2,581.8	2,417.0
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	693.2	55.5	623.7	283.9
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	2.6	(22.0)	(27.1)	(81.0)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(19.2)	10.7	(32.5)	11.6
Net impairment (losses) recoveries on available-for-sale securities	(16.6)	(11.3)	(59.6)	(69.4)
Net realized capital gains (losses)	676.6	44.2	564.1	214.5
Total revenues	4,627.8	2,818.0	10,855.5	8,880.3
Expenses
Benefits, claims and settlement expenses	2,504.6	1,482.2	6,020.7	4,800.6
Dividends to policyholders	32.6	45.5	92.7	122.3
Operating expenses	932.8	919.6	2,804.7	2,747.0
Total expenses	3,470.0	2,447.3	8,918.1	7,669.9
Income (loss) before income taxes	1,157.8	370.7	1,937.4	1,210.4
Income taxes (benefits)	344.6	43.3	455.8	186.8
Net income (loss)	813.2	327.4	1,481.6	1,023.6
Net income (loss) attributable to noncontrolling interest	3.0	19.2	13.0	25.1
Net income (loss) attributable to Principal Financial Group, Inc.	$ 810.2	$ 308.2	$ 1,468.6	$ 998.5
Earnings per common share
Basic earnings per common share (in dollars per share)	$ 2.80	$ 1.07	$ 5.08	$ 3.45
Diluted earnings per common share (in dollars per share)	2.76	1.06	5.02	3.41
Dividends declared per common share (in dollars per share)	$ 0.47	$ 0.41	$ 1.38	$ 1.18