Income Taxes (Deferred Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Taxes Assets [Abstract]
Allowance for uncollectible accounts	$ 884	$ 841
Accrued assets and other	5,212	3,562
Valuation allowances	(2,084)	(1,491)
Total current deferred tax assets	4,012	2,912
Share-based compensation	9,500	9,138
Interest on unrecognized tax benefits	363	456
Accrued liabilities and other	3,077	2,951
Operating and capital loss carryforwards	9,169	7,624
Valuation allowances	(7,265)	(6,133)
Total non-current deferred tax assets	14,844	14,036
Total deferred tax assets	18,856	16,948
Deferred Tax Liabilities [Abstract]
Prepaid expenses	925	783
Property and equipment, principally due to differences in depreciation	3,997	4,143
Goodwill, principally due to differences in amortization	148,494	124,060
Total deferred tax liabilities	153,416	128,986
Net deferred tax liabilities	$ 134,560	$ 112,038