Insurance Subsidiaries (Details) (USD $)	0 Months Ended		9 Months Ended		0 Months Ended
	May 02, 2014	May 08, 2013	Sep. 30, 2014	Sep. 30, 2013	Jun. 13, 2014 Security Life of Denver International Limited	Jun. 24, 2014 Security Life of Denver Insurance Company [Member] COLORADO	Jun. 09, 2014 Security Life of Denver Insurance Company [Member] COLORADO	May 19, 2014 Security Life of Denver Insurance Company [Member] COLORADO	Dec. 31, 2013 Principal Insurance Subsidiaries [Member]	Dec. 31, 2012 Principal Insurance Subsidiaries [Member]
Statutory Accounting Practices [Line Items]
Partners' Capital Account, Contributions					$ 150,000,000
Dividends paid	690,000,000		7,700,000	2,600,000		32,000,000	32,000,000	690,000,000
Contributions from (distributions to) participants in consolidated investment entities, net		1,434,000,000	1,235,900,000	626,700,000
Statutory Accounting Practices, Negative Unassigned Funds Accounts, Balance										0
Statutory Accounting Practices, Statutory Capital and Surplus, Balance									$ 0