Income Taxes - Net Deferred Tax Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Components Of Deferred Tax Assets And Liabilities [Abstract]
Deferred revenue	$ 11,639	$ 9,887
Employee benefits	77,994	74,068
Bad debt reserves	14,943	15,253
Investments in affiliates		13,670
Loss reserves	3,062	2,507
Pension	105,398	120,401
Net operating loss carryforward	15,541	23,727
Securities	6,128
Foreign tax credit	1,769	2,184
Other	7,904	8,712
Deferred tax assets before valuation allowance	244,378	270,409
Valuation allowance	(6,729)	(15,706)
Deferred tax assets	237,649	254,703
Depreciable and amortizable assets	304,632	284,532
Claims and related salvage	40,901	36,653
Investments in affiliates	3,193
Securities		8,934
Deferred tax liabilities	348,726	330,119
Net deferred tax liability	$ 111,077	$ 75,416