Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues
Premiums and other considerations	$ 694.7	$ 679.8
Fees and other revenues	733.6	598.0
Net investment income (loss)	789.3	824.8
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	(26.4)	22.1
Total other-than-temporary impairment losses on available-for-sale securities	(44.7)	(33.7)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	20.2	4.9
Net impairment losses on available-for-sale securities	(24.5)	(28.8)
Net realized capital gains (losses)	(50.9)	(6.7)
Total revenues	2,166.7	2,095.9
Expenses
Benefits, claims and settlement expenses	1,094.5	1,212.5
Dividends to policyholders	48.3	50.3
Operating expenses	795.7	555.1
Total expenses	1,938.5	1,817.9
Income (loss) before income taxes	228.2	278.0
Income taxes (benefits)	38.2	56.7
Net income (loss)	190.0	221.3
Net income (loss) attributable to noncontrolling interest	3.5	9.2
Net income (loss) attributable to Principal Financial Group, Inc.	186.5	212.1
Preferred stock dividends	8.2	8.2
Net income (loss) available to common stockholders	$ 178.3	$ 203.9
Earnings per common share
Basic earnings per common share (in dollars per share)	$ 0.61	$ 0.68
Diluted earnings per common share (in dollars per share)	$ 0.61	$ 0.68