Stockholders' Equity - Dividend Limitations (Details) - Principal Life Insurance Company Only - USD ($) $ in Millions		12 Months Ended
May 01, 2017	Dec. 31, 2017
Dividend Limitations
Statutory dividend limitation as percentage of policyholder surplus (as a percent)		10.00%
Dividends that can be paid in upcoming calendar year without exceeding statutory limitation		$ 1,122.4
Extraordinary dividend to parent	$ 1,068.4

Represents the statutory limitation on stockholder dividends as a percentage of the entity's policyholder surplus as of the preceding year-end.

No definition available.

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- Definition

The distributions of earnings to an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of dividends that can be declared or paid without approval of regulatory agency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Details

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