Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts receivable, allowance for doubtful accounts	$ 2,409	$ 2,563
Property and equipment depreciation	$ 76,765	$ 75,159
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	21,877,000	21,822,000
Treasury stock, shares	2,462,758	2,462,758
Common Class B [Member]
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	3,175,000	3,175,000
Common stock, shares issued	0	0