Temporary Differences and Resulting Deferred Income Tax Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Tax Assets And Liabilities [Line Items]
Accruals	$ 5,513	$ 5,084
Net operating loss carryforwards		1,314
Deferred Tax Assets, Gross, Current, Total	5,513	6,398
Benefit plans	10,862	11,237
Accruals	3,258	2,372
Net operating loss carryforwards	760	760
Share-based compensation	8,814	7,573
Partnership interest	1,785	1,851
Investment impairment	1,361	1,355
Other	1,590	1,316
Deferred Tax Assets, Gross, Noncurrent, Total	28,430	26,464
Less valuation allowance	(922)	(1,262)
Total deferred tax assets	33,021	31,600
Basis differences in intangible assets and property and equipment	(21,435)	(22,860)
Benefit plans	(1,467)	(2,476)
Other	(2,222)	(1,168)
Total deferred tax liabilities	(25,124)	(26,504)
Net deferred tax assets	$ 7,897	$ 5,096