Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues
Net premiums earned		$ 6,544.0	$ 5,723.4	$ 18,884.0	$ 16,602.6
Period over prior year period percent change in net premiums earned		14.00%		14.00%
Investment income		$ 142.9	119.3	$ 410.9	352.7
Period over prior year period percent change in investment income		20.00%		17.00%
Net realized gains (losses) on securities:
Net impairment losses recognized in earnings		$ (43.0)	(61.6)	$ (57.8)	(61.8)
Period Over Prior Year Period, Percent Increase (Decrease), Net Impairment Losses Recognized In Earnings		(30.00%)		(6.00%)
Net realized gains (losses) on securities		$ 18.3	40.9	$ 117.1	90.8
Period over prior year period percent change in net realized gains (losses) on securities		(55.00%)		29.00%
Total net realized gains (losses) on securities		$ (24.7)	(20.7)	$ 59.3	29.0
Period over prior year period percent change in total net realized gains (losses) on securities		19.00%		104.00%
Fees and other revenues		$ 96.3	86.8	$ 270.3	248.2
Period over prior year period percent change in fees and other revenues		11.00%		9.00%
Service revenues		$ 33.3	26.2	$ 94.5	77.7
Period over prior year period percent change in service revenues		27.00%		22.00%
Gains on extinguishment of debt		$ 0.0	0.0	$ 0.2	1.6
Percent Increase (Decrease) Gain Loss on Extingiushment of Debt				(88.00%)
Total revenues		$ 6,791.8	5,935.0	$ 19,719.2	17,311.8
Period over prior year period percent change in total revenues		14.00%		14.00%
Expenses
Losses and loss adjustment expenses		$ 5,050.5	4,398.2	$ 13,928.8	12,554.6
Period over prior year period percent change in losses and loss adjustment expenses		15.00%		11.00%
Policy acquisition costs		$ 540.1	475.4	$ 1,557.2	1,374.6
Period over prior year period percent change in policy acquisition costs		14.00%		13.00%
Other underwriting expenses		$ 877.7	739.6	$ 2,568.3	2,262.2
Period over prior year period percent change in other underwriting expenses		19.00%		14.00%
Investment expenses		$ 5.8	4.8	$ 18.0	14.9
Period over prior year period percent change in investment expenses		21.00%		21.00%
Service expenses		$ 28.9	23.2	$ 81.8	68.5
Period over prior year period percent change in service expenses		25.00%		19.00%
Interest expense		$ 37.4	35.3	$ 117.6	103.8
Period over prior year period percent change in interest expense		6.00%		13.00%
Total expenses		$ 6,540.4	5,676.5	$ 18,271.7	16,378.6
Period over prior year period percent change in total expenses		15.00%		12.00%
Net Income
Income before income taxes		$ 251.4	258.5	$ 1,447.5	933.2
Period over prior year period percent change in income before income taxes		(3.00%)		55.00%
Provision for income taxes		$ 36.6	53.0	$ 429.7	274.1
Period over prior year period percent change in provision for income taxes		(31.00%)		57.00%
Net income		$ 214.8	205.5	$ 1,017.8	659.1
Period over prior year period percent change in net income		5.00%		54.00%
Net (income) loss attributable to noncontrolling interest (NCI)		$ 9.2	(6.8)	$ (1.9)	(11.3)
Period over prior year period percent change in net (income) loss attributable to noncontrolling interest		(235.00%)		(83.00%)
Net income attributable to Progressive		$ 224.0	198.7	$ 1,015.9	647.8
Period over prior year period percent change in net income attributable to Progressive		13.00%		57.00%
Other Comprehensive Income (Loss)
Total net unrealized gains (losses) on securities		$ 75.5	87.1	$ 300.5	248.2
Period over prior year period percent change in total net unrealized gains (losses) on securities		(13.00%)		21.00%
Net unrealized losses on forecasted transactions		$ 0.1	(0.3)	$ (5.6)	(0.9)
Period Over Prior Year Period, Percent Increase (Decrease), Unrealized Gain (Loss) On Forecasted Transactions		(133.00%)
Foreign currency translation adjustment		$ 0.6	0.3	$ 0.8	0.7
Period over prior year period percent change in foreign currency translation adjustment		100.00%		14.00%
Other comprehensive income		$ 76.2	87.1	$ 295.7	248.0
Period over prior year period percent change in other comprehensive income		(13.00%)		19.00%
Other comprehensive (income) loss attributable to NCI		$ (0.7)	1.2	$ (2.9)	(2.3)
Period over prior year period change in Comprehensive (income) loss attributable to NCI		(158.00%)		26.00%
Comprehensive income attributable to Progressive		$ 299.5	$ 287.0	$ 1,308.7	$ 893.5
Period over prior year period percent change in comprehensive income		4.00%		46.00%
Computation of Per Share Earnings Attributable to Progressive
Average shares outstanding - Basic		581.3	581.5	580.7	582.4
Period over prior year period percent change in average shares outstanding - basic		0.00%		0.00%
Net effect of dilutive stock-based compensation		4.3	3.1	5.0	3.2
Period over prior year period percent change in net effect of dilutive stock-based compensation		39.00%		56.00%
Total average equivalent shares - Diluted		585.6	584.6	585.7	585.6
Period over prior year period percent change in total equivalent shares - diluted		0.00%		0.00%
Basic: Earnings per share		$ 0.39	$ 0.34	$ 1.75	$ 1.11
Period over prior year period percent change in basic: earnings per share		13.00%		57.00%
Diluted: Earnings per share		$ 0.38	0.34	$ 1.73	1.11
Period over prior year period percent change in diluted: earnings per share		13.00%		57.00%
Dividends declared per share	[1]	$ 0	$ 0	$ 0	$ 0

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