Supplementary Information Concerning Property-Casualty Insurance Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs	$ 67,007		$ 61,005		$ 63,984
Reserve for losses and loss adjustment expenses	2,045,071		2,097,048		2,082,679
Discount, if any, deducted
Unearned premiums	714,606		642,407		532,628
Net earned premiums	841,939		781,964		691,645
Net investment income	56,243	[1]	54,100	[1]	63,119	[1]
Losses and loss adjustment expenses incurred related to Current year	520,227		542,724		474,852
Losses and loss adjustment expenses incurred related to Prior year	(1,266)		(45,291)		2,145
Amortization of deferred policy acquisition costs	115,842	[2]	123,819	[2]	112,506	[2]
Other operating expenses	164,434	[1]	159,079	[1]	138,029	[1]
Net written premiums	$ 887,922		$ 833,655		$ 753,798

[1] Net investment income and Other operating expenses reflect only such amounts attributable to the Company's insurance operations.

[2] Amortization of deferred policy acquisition costs reflects only such amounts attributable to the Company's insurance operations. A portion of these costs is eliminated in consolidation.