Supplemental Information About Incurred and Paid Loss and LAE Development - Insurance Segment - PacificComp (Detail) $ in Millions		Dec. 31, 2016 USD ($) Claim		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2008 USD ($)	Dec. 31, 2007 USD ($)
Claims Development [Line Items]
Unpaid loss and LAE, net of reinsurance recoverables		$ 9,851.0	[1]	$ 9,629.9	$ 10,307.8	$ 10,650.4
Insurance Segment
Claims Development [Line Items]
Unpaid loss and LAE, net of reinsurance recoverables	[1]	1,906.6
Insurance Segment | Pacific Comp
Claims Development [Line Items]
Unpaid loss and LAE, net of reinsurance recoverables, prior to 2007		15.1
Unpaid loss and LAE, net of reinsurance recoverables	[1]	232.7
Insurance Segment | Pacific Comp | Accident Year 2007
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		123.0		123.4	122.8	121.7	$ 118.7	$ 116.8	$ 113.8	$ 112.4	$ 105.6	$ 90.9
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 4.5
Cumulative Number of Reported Claims | Claim	[2]	8,449
Paid Loss and LAE, Net of Reinsurance		$ 108.9		106.8	103.1	97.8	92.9	85.9	74.7	59.2	39.7	$ 17.9
Insurance Segment | Pacific Comp | Accident Year 2008
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		109.1		109.9	110.9	110.8	108.3	107.3	100.6	90.0	79.1
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 5.7
Cumulative Number of Reported Claims | Claim	[2]	5,789
Paid Loss and LAE, Net of Reinsurance		$ 97.2		94.6	91.2	85.8	78.6	69.2	55.3	35.6	$ 15.5
Insurance Segment | Pacific Comp | Accident Year 2009
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		83.0		82.0	82.0	80.2	75.8	74.5	61.0	58.2
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 4.3
Cumulative Number of Reported Claims | Claim	[2]	3,013
Paid Loss and LAE, Net of Reinsurance		$ 71.7		68.6	64.7	58.3	50.8	41.1	28.0	$ 12.0
Insurance Segment | Pacific Comp | Accident Year 2010
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		5.8		6.0	6.0	5.7	5.4	5.1	4.1
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 0.5
Cumulative Number of Reported Claims | Claim	[2]	211
Paid Loss and LAE, Net of Reinsurance		$ 4.9		4.8	4.5	4.0	3.4	2.7	$ 1.4
Insurance Segment | Pacific Comp | Accident Year 2011
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		2.8		3.0	3.0	3.0	2.8	2.8
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 0.3
Cumulative Number of Reported Claims | Claim	[2]	100
Paid Loss and LAE, Net of Reinsurance		$ 2.5		2.1	2.0	1.7	1.1	$ 0.6
Insurance Segment | Pacific Comp | Accident Year 2012
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		14.7		15.1	15.1	15.1	14.5
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 2.0
Cumulative Number of Reported Claims | Claim	[2]	560
Paid Loss and LAE, Net of Reinsurance		$ 11.0		10.0	8.2	5.6	$ 2.4
Insurance Segment | Pacific Comp | Accident Year 2013
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		29.3		30.4	30.4	31.0
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 5.7
Cumulative Number of Reported Claims | Claim	[2]	1,005
Paid Loss and LAE, Net of Reinsurance		$ 18.4		15.4	10.1	$ 4.7
Insurance Segment | Pacific Comp | Accident Year 2014
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		53.5		52.6	52.6
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 8.1
Cumulative Number of Reported Claims | Claim	[2]	2,218
Paid Loss and LAE, Net of Reinsurance		$ 30.1		20.8	$ 8.8
Insurance Segment | Pacific Comp | Accident Year 2015
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		76.8		76.6
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 25.4
Cumulative Number of Reported Claims | Claim	[2]	3,362
Paid Loss and LAE, Net of Reinsurance		$ 24.9		$ 10.4
Insurance Segment | Pacific Comp | Accident Year 2016
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		104.8
Incurred But Not Reported Loss and Loss Adjustment Expense Reserves		$ 47.2
Cumulative Number of Reported Claims | Claim	[2]	4,302
Paid Loss and LAE, Net of Reinsurance		$ 15.6
Insurance Segment | Pacific Comp | Accident Year 2007 through 2016
Claims Development [Line Items]
Incurred Loss and LAE, net of reinsurance		602.8
Paid Loss and LAE, Net of Reinsurance		$ 385.2

[1] Includes unallocated LAE, which aggregate to 1.3 percent of gross loss and LAE reserves as of December 31, 2016. Net loss and LAE Reserves by component are shown in the preceding tables, and consolidated gross loss and LAE reserves is presented in the Consolidated Balance Sheets.

[2] Represents claims reported by insured claimants.