Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Condensed Consolidated Statements of Cash Flows [Abstract]
Cash and cash equivalents - unrestricted, beginning of period	$ 44,388	$ 124,398
Cash Flows from Operating Activities:
Net income	14,982	6,680
Amounts to reconcile net income to net cash flows provided by operating activities:
Income from discontinued operations, net of taxes	(2)	(8)
Income from unconsolidated companies	(109)	(325)
Loss on disposals of long-lived assets		40
Provision for deferred income taxes	15,363	3,076
Depreciation and amortization	62,688	58,328
Amortization of deferred financing costs	2,423	2,635
Amortization of discount on convertible notes	6,754	6,216
Stock-based compensation expense	5,277	4,826
Changes in:
Trade receivables	(12,255)	(17,184)
Interest receivable	(2,394)	1,951
Accounts payable and accrued liabilities	(16,228)	(22,580)
Other assets and liabilities	2,600	(4,005)
Net cash flows provided by operating activities - continuing operations	79,099	39,650
Net cash flows provided by (used in) operating activities - discontinued operations	51	(28)
Net cash flows provided by operating activities	79,150	39,622
Cash Flows from Investing Activities:
Purchases of property and equipment	(58,788)	(61,413)
Collection of notes receivable	2,870	2,465
Other investing activities	424	2,183
Net cash flows used in investing activities - continuing operations	(55,494)	(56,765)
Net cash flows used in investing activities - discontinued operations
Net cash flows used in investing activities	(55,494)	(56,765)
Cash Flows from Financing Activities:
Repayments under credit facility	(45,000)
Proceeds from exercise of stock option and purchase plans	6,833	4,193
Other financing activities, net	(373)	(85)
Net cash flows provided by (used in) financing activities - continuing operations	(38,540)	4,108
Net cash flows provided by financing activities - discontinued operations
Net cash flows provided by (used in) financing activities	(38,540)	4,108
Net change in cash and cash equivalents	(14,884)	(13,035)
Cash and cash equivalents - unrestricted, end of period	$ 29,504	$ 111,363