Schedule II - Condensed Financial Information of Registrant (Parent Only) - Financial Statement Footnotes (Details) - Principal Financial Group, Inc. parent only - Legal Entities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividends and Returns of Capital Received from (Contributed to) Unconsolidated Entity
Dividends and returns of capital received from (contributed to) unconsolidated entities	$ 494.2	$ 1,041.6	$ 1,002.5
Nonqualified benefit plans
Condensed Financial Statements, Captions [Line Items]
Assets held in Rabbi trusts	731.9	671.7
Liabilities held in Rabbi trusts	$ 593.7	$ 542.4