Consolidated Statements of Financial Position (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets
Fixed maturities, available-for-sale (2013 and 2012 include $232.8 million and $194.6 million related to consolidated variable interest entities)	$ 49,191.6	$ 50,939.3
Fixed maturities, trading (2013 and 2012 both include $110.4 million related to consolidated variable interest entities)	589.8	626.7
Equity securities, available-for-sale	135.3	136.5
Equity securities, trading	636.7	252.8
Mortgage loans	12,121.7	11,519.7
Real estate	1,264.8	1,180.3
Policy loans	865.3	864.9
Other investments (2013 and 2012 include $76.6 million and $80.3 million related to consolidated variable interest entities and $116.5 million and $113.9 million measured at fair value under the fair value option)	2,976.3	3,291.1
Total investments	67,781.5	68,811.3
Cash and cash equivalents	1,110.5	4,177.2
Accrued investment income	565.4	584.4
Premiums due and other receivables	1,219.0	1,084.4
Deferred acquisition costs	2,925.4	2,590.0
Property and equipment	476.4	464.2
Goodwill	1,138.5	543.4
Other intangibles	1,517.3	914.7
Separate account assets (2013 includes $33,179.6 million related to consolidated variable interest entities)	118,740.2	81,653.8
Other assets	1,038.5	1,006.8
Total assets	196,512.7	161,830.2
Liabilities
Contractholder funds	36,269.7	37,786.5
Future policy benefits and claims	22,129.5	22,436.2
Other policyholder funds	739.5	716.4
Short-term debt	175.3	40.8
Long-term debt	2,578.6	2,671.3
Income taxes currently payable	7.2	15.3
Deferred income taxes	578.7	600.0
Separate account liabilities (2013 includes $33,179.6 million related to consolidated variable interest entities)	118,740.2	81,653.8
Other liabilities (2013 and 2012 include $314.4 million and $302.9 million related to consolidated variable interest entities, of which $98.9 million and $85.0 million are measured at fair value under the fair value option)	5,831.5	6,146.1
Total liabilities	187,050.2	152,066.4
Redeemable noncontrolling interest	53.6	60.4
Stockholders' equity
Common stock, par value $.01 per share - 2,500.0 million shares authorized, 456.5 million and 453.5 million shares issued, and 293.9 million and 293.8 million shares outstanding in 2013 and 2012	4.6	4.5
Additional paid-in capital	9,819.8	9,730.9
Retained earnings (accumulated deficit)	5,125.2	4,862.0
Accumulated other comprehensive income (loss)	(0.5)	640.3
Treasury stock, at cost (162.6 million and 159.7 million shares in 2013 and 2012)	(5,645.8)	(5,554.4)
Total stockholders' equity attributable to Principal Financial Group, Inc.	9,303.4	9,683.4
Noncontrolling interest	105.5	20.0
Total stockholders' equity	9,408.9	9,703.4
Total liabilities and stockholders' equity	196,512.7	161,830.2
Series A
Stockholders' equity
Preferred stock, value
Series B
Stockholders' equity
Preferred stock, value	$ 0.1	$ 0.1