Components of Deferred Income Tax Amounts (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Income Tax Assets
Provision for bad debts	$ 7,585	$ 7,123
Employee retirement and other benefit obligations	62,637	54,708
Workers' compensation	10,007	8,526
Deferred compensation	10,895	15,502
Credits and net operating loss carryforwards	48,609	42,289
Other	23,781	16,427
Total deferred income tax assets	163,514	144,575
Deferred Income Tax Liabilities
Amortization of intangible assets	(22,169)	(20,475)
Property and equipment basis differences	(8,029)	(8,823)
Other	(5,257)	(4,742)
Total deferred income tax liabilities	(35,455)	(34,040)
Valuation allowance	(39,310)	(36,334)
Total deferred income tax assets, net	$ 88,749	$ 74,201