Business and Summary of Significant Accounting Principles (Income Statements Immaterial Error Correction) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Depreciation and amortization expense	$ 32,120	$ 30,653	$ 97,850	$ 93,298
Operating income	25,392	31,933	69,710	74,494
Income before income tax expense	8,793	15,218	18,967	13,897
Income tax expense	5,270	7,979	10,387	7,303
Net income	3,523	7,239	8,580	6,594
Scenario As Previously Reported [Member]
Depreciation and amortization expense		30,702		93,054
Operating income		31,884		74,738
Income before income tax expense		15,169		14,141
Income tax expense		7,959		7,403
Net income		7,210		6,738
Adjustment [Member]
Depreciation and amortization expense		(49)		244
Operating income		49		(244)
Income before income tax expense		49		(244)
Income tax expense		20		(100)
Net income		$ 29		$ (144)