Regulatory Matters (Reconciliation Of The Statutory Capital And Surplus Of The Insurance) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Statutory capital and surplus	$ 1,228.4	$ 1,359.0
GAAP equity	2,171.8	2,152.8	2,169.0	1,990.4
Future Policy Benefits And Other Policyholder Funds [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	276.0	325.8
Dac Voba And Other Intangible Assets [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	365.7	351.6
Deferred Tax Liabilities [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	(245.6)	(265.3)
Asset Valuation Reserve [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	106.2	127.5
Valuation Of Investments [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	259.6	236.4
Interest Maintenance Reserve [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	28.5	25.5
Equity Of Stancorp And It Non Insurance Subsidiaries [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	277.5	116.1
Non Admitted Assets [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	166.3	178.2
Pension and postretirement benefit plans [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	(11.3)	(6.6)
Capital Lease Obligations [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	(2.1)	(3.4)
Surplus Note [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	(250.0)	(250.0)
Other Net [Member]
Statutory Accounting Practices Statutory To Gaap Reconciling Items [Line Items]
Adjustments to reconcile to GAAP equity:	$ (27.4)	$ (42.0)