Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Net premiums earned		$ 7,634.2	$ 6,313.3	$ 14,808.2	$ 12,340.0
Period over prior year period percent change in net premiums earned		21.00%		20.00%
Investment income		$ 192.1	138.8	$ 358.4	268.0
Period over prior year period percent change in investment income		38.00%		34.00%
Net realized gains (losses) on securities:
Gross Realized Gain (Loss), excluding Holding Period and OTTI		$ (9.6)	45.5	$ 97.4	97.6
Net Holding Period Realized Gain (Loss)		53.5	0.4	(101.7)	1.2
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net		(11.1)	(13.8)	(11.1)	(14.8)
Total net realized gains (losses) on securities		$ 32.8	32.1	$ (15.4)	84.0
Period Over Prior Year Period, Percent Increase (Decrease), Net Realized Gains (Losses) On Security Sales		(121.00%)		0.00%
Period Over Prior Year Period, Percent Increase (Decrease), Net Impairment Losses Recognized In Earnings		(20.00%)		(25.00%)
Period Over Prior Year Period, Percent Increase (Decrease), Total Net Realized Gains (Losses) On Securities		2.00%		(118.00%)
Fees and other revenues		$ 116.0	88.8	$ 219.8	174.0
Period over prior year period percent change in fees and other revenues		31.00%		26.00%
Service revenues		$ 42.9	32.7	$ 77.1	61.2
Period over prior year period percent change in service revenues		31.00%		26.00%
Other gains (losses)		$ 0.0	0.0	$ 0.0	0.2
Period Over Prior Year Period, Percent Increase (Decrease), Other Gains (Losses)				(100.00%)
Total revenues		$ 8,018.0	6,605.7	$ 15,448.1	12,927.4
Period over prior year period percent change in total revenues		21.00%		19.00%
Expenses
Losses and loss adjustment expenses		$ 5,375.3	4,614.9	$ 10,246.1	8,878.3
Period over prior year period percent change in losses and loss adjustment expenses		16.00%		15.00%
Policy acquisition costs		$ 630.8	514.2	$ 1,227.0	1,017.1
Period over prior year period percent change in policy acquisition costs		23.00%		21.00%
Other underwriting expenses		$ 1,046.9	845.0	$ 2,027.1	1,690.6
Period over prior year period percent change in other underwriting expenses		24.00%		20.00%
Investment expenses		$ 6.2	6.6	$ 12.2	12.2
Period over prior year period percent change in investment expenses		(6.00%)		0.00%
Service expenses		$ 37.0	27.0	$ 66.3	52.9
Period over prior year period percent change in service expenses		37.00%		25.00%
Interest expense		$ 41.7	43.4	$ 78.5	80.2
Period over prior year period percent change in interest expense		(4.00%)		(2.00%)
Total expenses		$ 7,137.9	6,051.1	$ 13,657.2	11,731.3
Period over prior year period percent change in total expenses		18.00%		16.00%
Net Income
Income before income taxes		$ 880.1	554.6	$ 1,790.9	1,196.1
Period over prior year period percent change in income before income taxes		59.00%		50.00%
Provision for income taxes		$ 178.9	181.9	$ 359.9	393.1
Period over prior year period percent change in provision for income taxes		(2.00%)		(8.00%)
Net income		$ 701.2	372.7	$ 1,431.0	803.0
Period over prior year period percent change in net income		88.00%		78.00%
Net (income) loss attributable to noncontrolling interest (NCI)		$ 3.0	(5.1)	$ (8.8)	(11.1)
Period over prior year period percent change in net (income) loss attributable to noncontrolling interest		(159.00%)		(21.00%)
Net income attributable to Progressive		$ 704.2	367.6	$ 1,422.2	791.9
Period over prior year period percent change in net income attributable to Progressive		92.00%		80.00%
Other Comprehensive Income (Loss)
Total net unrealized gains (losses) on securities		$ (50.1)	92.6	$ (204.6)	225.0
Period over prior year period percent change in total net unrealized gains (losses) on securities		(154.00%)		(191.00%)
Net unrealized losses on forecasted transactions		$ 0.2	(8.0)	$ 0.4	(5.7)
Period Over Prior Year Period, Percent Increase (Decrease), Unrealized Gain (Loss) On Forecasted Transactions		(103.00%)		(107.00%)
Foreign currency translation adjustment		$ 0.0	(0.1)	$ 0.0	0.2
Period over prior year period percent change in foreign currency translation adjustment		(100.00%)		(100.00%)
Other comprehensive income (loss)		$ (49.9)	84.5	$ (204.2)	219.5
Period over prior year period percent change in other comprehensive income		(159.00%)		(193.00%)
Other comprehensive (income) loss attributable to NCI		$ 0.6	(1.3)	$ 4.6	(2.2)
Period over prior year period change in Comprehensive (income) loss attributable to NCI		(146.00%)		(309.00%)
Comprehensive income attributable to Progressive		$ 654.9	450.8	$ 1,222.6	1,009.2
Period over prior year period percent change in comprehensive income		45.00%		21.00%
Computation of Per Share Earnings Available to Progressive Common Shareholders
Net income attributable to Progressive		$ 704.2	367.6	$ 1,422.2	791.9
Period over prior year period percent change in net income attributable to Progressive		92.00%		80.00%
Preferred Stock Dividends, Income Statement Impact		$ 6.7	0.0	$ 7.9	0.0
Net Income (Loss) Available to Common Stockholders, Basic		$ 697.5	$ 367.6	$ 1,414.3	$ 791.9
Period Over Prior Year Period, Percent Increase (Decrease), Net Income (Loss) Available to Common Stockholders		90.00%		79.00%
Average common shares outstanding - Basic		582.0	580.5	582.0	580.4
Period over prior year period percent change in average shares outstanding - basic		0.00%		0.00%
Net effect of dilutive stock-based compensation		3.8	3.3	3.6	3.1
Period over prior year period percent change in net effect of dilutive stock-based compensation		15.00%		16.00%
Total average equivalent common shares - Diluted		585.8	583.8	585.6	583.5
Period over prior year period percent change in total equivalent shares - diluted		0.00%		0.00%
Basic: Earnings per common share		$ 1.20	$ 0.63	$ 2.43	$ 1.36
Period over prior year period percent change in basic: earnings per share		89.00%		78.00%
Diluted: Earnings per common share		$ 1.19	0.63	$ 2.42	1.36
Period over prior year period percent change in diluted: earnings per share		89.00%		78.00%
Dividends declared per share	[1]	$ 0	$ 0	$ 0	$ 0

[1] Progressive maintains an annual variable common share dividend program. See Note 9 – Dividends for further discussion.