Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries [Abstract]
Parent company's percentage ownership of guarantors (as a percent)	100.00%
Assets
Cash and cash equivalents	$ 135,954	$ 104,402	$ 86,879	$ 124,281
Accounts receivable, net	180,807	182,467
Inventories	87,792	79,742
Notes receivable	10,300	0
Other current assets	47,239	38,945
Property and equipment, net	396,400	426,488
Investment in subsidiaries	0	0
Goodwill	797,624	768,393
Intangible assets	87,236	86,859
Intercompany balances	0	0
Other assets	454,683	474,615
Total assets	2,198,035	2,161,911
Liabilities and stockholders' equity
Current installments of long-term debt	14,978	26,191
Other current liabilities	211,926	210,902
Long-term debt, excluding current installments	1,454,088	1,364,476
Other non-current liabilities	116,906	116,628
Intercompany balances	0	0
Stockholders’ equity	400,137	443,714
Total liabilities and stockholders' equity	2,198,035	2,161,911
Parent Company
Assets
Cash and cash equivalents	60,907	24,042
Accounts receivable, net	0	0
Inventories	0	0
Notes receivable	10,300	0
Other current assets	8,366	8,699
Property and equipment, net	4,894	3,522
Investment in subsidiaries	545,641	551,256
Goodwill	0	0
Intangible assets	0	0
Intercompany balances	0	125,440
Other assets	64,792	17,002
Total assets	694,900	729,961
Liabilities and stockholders' equity
Current installments of long-term debt	0	0
Other current liabilities	25,872	31,231
Long-term debt, excluding current installments	250,000	250,000
Other non-current liabilities	5,101	5,016
Intercompany balances	13,790	0
Stockholders’ equity	400,137	443,714
Total liabilities and stockholders' equity	694,900	729,961
SGI
Assets
Cash and cash equivalents	137	56
Accounts receivable, net	53,100	53,531
Inventories	24,748	23,714
Notes receivable	0	0
Other current assets	5,592	3,409
Property and equipment, net	160,490	166,637
Investment in subsidiaries	782,243	721,909
Goodwill	273,656	273,656
Intangible assets	41,168	41,520
Intercompany balances	0	0
Other assets	19,905	82,748
Total assets	1,361,039	1,367,180
Liabilities and stockholders' equity
Current installments of long-term debt	6,280	6,280
Other current liabilities	55,576	56,050
Long-term debt, excluding current installments	1,200,653	1,104,884
Other non-current liabilities	42,971	38,772
Intercompany balances	36,990	71,603
Stockholders’ equity	18,569	89,591
Total liabilities and stockholders' equity	1,361,039	1,367,180
Guarantor Subsidiaries
Assets
Cash and cash equivalents	0	0
Accounts receivable, net	39,351	41,238
Inventories	15,695	16,884
Notes receivable	0	0
Other current assets	6,078	5,117
Property and equipment, net	34,011	36,028
Investment in subsidiaries	0	0
Goodwill	78,618	78,618
Intangible assets	22,963	25,849
Intercompany balances	274,434	231,357
Other assets	13,804	12,265
Total assets	484,954	447,356
Liabilities and stockholders' equity
Current installments of long-term debt	0	0
Other current liabilities	33,470	30,140
Long-term debt, excluding current installments	0	0
Other non-current liabilities	11,890	13,427
Intercompany balances	0	0
Stockholders’ equity	439,594	403,789
Total liabilities and stockholders' equity	484,954	447,356
Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	76,560	81,482
Accounts receivable, net	88,356	87,698
Inventories	47,349	39,144
Notes receivable	0	0
Other current assets	27,203	21,720
Property and equipment, net	197,005	220,301
Investment in subsidiaries	816,416	909,379
Goodwill	445,350	416,119
Intangible assets	23,105	19,490
Intercompany balances	0	0
Other assets	358,797	368,701
Total assets	2,080,141	2,164,034
Liabilities and stockholders' equity
Current installments of long-term debt	8,698	19,911
Other current liabilities	98,650	94,692
Long-term debt, excluding current installments	3,435	9,592
Other non-current liabilities	56,944	59,413
Intercompany balances	223,673	285,162
Stockholders’ equity	1,688,741	1,695,264
Total liabilities and stockholders' equity	2,080,141	2,164,034
Eliminating Entries
Assets
Cash and cash equivalents	(1,650)	(1,178)
Accounts receivable, net	0	0
Inventories	0	0
Notes receivable	0	0
Other current assets	0	0
Property and equipment, net	0	0
Investment in subsidiaries	(2,144,300)	(2,182,544)
Goodwill	0	0
Intangible assets	0	0
Intercompany balances	(274,434)	(356,797)
Other assets	(2,615)	(6,101)
Total assets	(2,422,999)	(2,546,620)
Liabilities and stockholders' equity
Current installments of long-term debt	0	0
Other current liabilities	(1,642)	(1,211)
Long-term debt, excluding current installments	0	0
Other non-current liabilities	0	0
Intercompany balances	(274,453)	(356,765)
Stockholders’ equity	(2,146,904)	(2,188,644)
Total liabilities and stockholders' equity	$ (2,422,999)	$ (2,546,620)