Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income (loss)	$ 191.3	$ 74.5	$ 594.3	$ 532.5
Other comprehensive income (loss), net:
Net unrealized gains (losses) on available-for-sale securities	296.0	7.4	558.0	329.5
Noncredit component of impairment losses on fixed maturities, available-for-sale	(4.0)	18.9	(14.8)	45.2
Net unrealized gains (losses) on derivative instruments	(18.2)	32.1	27.2	19.5
Foreign currency translation adjustment	48.6	(136.4)	27.2	(64.9)
Net unrecognized postretirement benefit obligation	8.7	(201.5)	26.2	(174.2)
Other comprehensive income (loss)	331.1	(279.5)	623.8	155.1
Comprehensive income (loss)	522.4	(205.0)	1,218.1	687.6
Comprehensive income (loss) attributable to noncontrolling interest	4.2	(5.9)	16.3	36.3
Comprehensive income (loss) attributable to Principal Financial Group, Inc.	$ 518.2	$ (199.1)	$ 1,201.8	$ 651.3