Goodwill and Other Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Changes in Goodwill
Beginning balance, Goodwill	$ 543.4	$ 482.3
Goodwill from acquisitions	634.4	73.8
Goodwill disposed	(1.4)
Foreign currency, Goodwill	(80.1)	(8.7)
Other changes in goodwill	4.0	(4.0)
Ending balance, Goodwill	1,100.3	543.4
Retirement and Investor Services
Changes in Goodwill
Beginning balance, Goodwill	68.6	72.6
Other changes in goodwill	4.0	(4.0)
Ending balance, Goodwill	72.6	68.6
Principal Global Investors
Changes in Goodwill
Beginning balance, Goodwill	239.9	237.0
Foreign currency, Goodwill	1.2	2.9
Ending balance, Goodwill	241.1	239.9
Principal International
Changes in Goodwill
Beginning balance, Goodwill	179.5	127.8
Goodwill from acquisitions	631.8	63.3
Foreign currency, Goodwill	(81.3)	(11.6)
Ending balance, Goodwill	730.0	179.5
U.S. Insurance Solutions
Changes in Goodwill
Beginning balance, Goodwill	55.4	44.9
Goodwill from acquisitions	2.6	10.5
Goodwill disposed	(1.4)
Ending balance, Goodwill	$ 56.6	$ 55.4

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 43

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 72

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 34

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation.

+ References+ Details

- Definition

Write-off of the carrying amount of goodwill associated with all or a portion of a reporting unit that is sold in the period.

+ References+ Details