Prior Accident Year Workers' Compensation Net Loss Reserves (Detail) (USD $)	12 Months Ended					3 Months Ended		12 Months Ended		3 Months Ended		12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Pacific Compensation Corporation	Dec. 31, 2010 Pacific Compensation Corporation	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation	Jun. 30, 2011 Pacific Compensation Corporation Workers' Compensation	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation	Dec. 31, 2010 Pacific Compensation Corporation Workers' Compensation	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation Medical Benefits	Jun. 30, 2011 Pacific Compensation Corporation Workers' Compensation Medical Benefits	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation Medical Benefits	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation Allocated Loss Adjustment Expenses	Jun. 30, 2011 Pacific Compensation Corporation Workers' Compensation Allocated Loss Adjustment Expenses	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation Allocated Loss Adjustment Expenses	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation Unallocated Loss Adjustment Expenses	Dec. 31, 2011 Pacific Compensation Corporation Workers' Compensation Unallocated Loss Adjustment Expenses
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Decrease in ceded loss and LAE reserves				$ 1,100,000	$ 5,000,000		$ 2,000,000	$ 2,000,000
Claims and Claim Adjustment Expense Incurred Related to Prior Year	(25,800,000)	(33,700,000)	(17,900,000)	28,700,000	13,400,000	13,400,000	15,000,000	28,400,000	12,500,000	4,200,000	10,000,000	14,200,000
Increases in allocated or unallocated LAE													$ 6,400,000	$ 3,000,000	$ 9,400,000	$ 2,800,000	$ 2,800,000