Income Taxes (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax liabilities:
Excess tax amortization	$ 298,959	$ 284,257
Excess tax depreciation	10,159	12,105
Expenses deductible for tax purposes in a year different from the year accrued	22,295	16,507
Total deferred tax liabilities	331,413	312,869
Deferred tax assets:
Accrued pension liability	50,658	47,030
Deferred compensation and benefits	12,409	11,174
State taxes	6,656	6,254
Net operating losses, state	5,614	5,664
Expenses deductible for tax purposes in a year different from the year accrued	3,190	3,383
Other	2,058	2,239
Deferred tax assets	80,585	75,744
Valuation allowance for deferred taxes	(5,614)	(5,664)
Total deferred tax assets, net	74,971	70,080
Net deferred tax liability	$ 256,442	$ 242,789