Debt (Details) (USD $) In Millions, unless otherwise specified						12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Other recourse short-term debt	Dec. 31, 2012 Other recourse short-term debt	Dec. 31, 2013 Line of credit	Dec. 31, 2013 Line of credit Principal Financial Services, Inc., Principal Life Insurance Company, and Principal Financial Group, co-borrowers	Dec. 31, 2013 Line of credit Principal Life	Dec. 31, 2013 Line of credit Principal Financial Services, Inc., Principal Life Insurance Company, Principal Financial Services V (UK) LTD, and Principal Financial Group, co-borrowers	Apr. 30, 2013 Line of credit Principal Financial Services, Inc., Principal Life Insurance Company, Principal Financial Services V (UK) LTD, and Principal Financial Group, co-borrowers	Dec. 31, 2013 Commercial paper	Dec. 31, 2012 Commercial paper
Short-Term Debt
Short-term debt	$ 150.6	$ 40.8	$ 32.8	$ 40.8	$ 117.8
Credit facilities	1,105.0	905.0				500.0	300.0		200.0
Term of credit facility						4 years	364 days	3 years
Outstanding borrowings related to credit facilities	150.6	40.8
Assets pledged as support for credit facilities	0
Support provided by back-stop facility for commercial paper program (as a percent)										100.00%	100.00%
Weighted-average interest rates on short-term borrowings (as a percent)	4.70%	4.70%
Back-stop facility outstanding balances										$ 0	$ 0