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Dividends-Additional Information (Details)
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dividends [Abstract]      
Target percentage used to determine annual variable dividend 33.33%pgr_DividendComputationTargetRateAsPercentOfUnderwritingAfterTaxIncome    
Gainshare factor used to determine annual variable dividend range, minimum 0pgr_CompanyPerformanceFactorRangeMinimum    
Gainshare factor used to determine annual variable dividend range, maximum 2pgr_CompanyPerformanceFactorRangeMaximum    
Gainshare factor used to determine annual variable dividend 1.32pgr_CompanyPerformanceFactor 1.21pgr_CompanyPerformanceFactor 1.12pgr_CompanyPerformanceFactor