Schedule II - Condensed Financial Information of Registrant (Parent Only) - Financial Statement Footnotes (Details) - Principal Financial Group, Inc. Parent Only - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Dividends and Returns of Capital Received from (Contributed to) Unconsolidated Entity
Dividends and returns of capital received from (contributions to) unconsolidated entities	$ 685.5	$ 917.7	$ 319.5
Supplemental Disclosures of Non-Cash Investing Activity
Non-cash increase in investment in subsidiaries		$ 56.3