2.4.0.84010 - Disclosure - Nature of Operations and Significant Accounting Policies (Details)truefalseIn Millions, unless otherwise specifiedfalse1false USDfalsefalse$I2013Q2http://www.sec.gov/CIK0001126328instant2013-06-30T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$I2012http://www.sec.gov/CIK0001126328instant2012-12-31T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 2us-gaap_SeparateAccountsDisclosureAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Separate Accounts2false 3pfg_SeparateAccountWithSharesOfPrincipalFinancialGroupStockpfg_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse181600000181.6USD$falsetruefalse2truefalsefalse148300000148.3USD$falsetruefalsexbrli:monetaryItemTypemonetaryThis item represents the value of a separate account that primarily includes shares of Principal Financial Group, Inc. stock that were allocated and issued to eligible participants of qualified employee benefit plans administered as part of the policy credits issued under the 2001 demutualization.No definition available.false2Separate account that primarily includes shares of Principal Financial Group, Inc. stock that were allocated and issued to eligible participants of qualified employee benefit plans as part of the 2001 demutualizationfalseNature of Operations and Significant Accounting Policies (Details) (USD $)HundredThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://principal.com/role/DisclosureNatureOfOperationsAndSignificantAccountingPoliciesDetails22