Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries
Parent company's percentage ownership of guarantors	100.00%
Assets
Cash and cash equivalents	$ 104,402	$ 124,281	$ 260,131	$ 140,639
Accounts receivable, net	182,467	178,179
Inventories	81,711	68,744
Other current assets	40,502	42,461
Property and equipment, net	426,488	450,581
Goodwill, net	766,349	763,915	772,732
Intangible assets, net	86,859	70,613
Other assets	473,123	452,764
Total assets	2,161,901	2,151,538	2,291,792
Liabilities and stockholders' equity
Debt payments due within one year	26,191	8,431
Other current liabilities	210,892	187,567
Long-term debt, excluding current installments	1,364,476	1,388,259
Other non-current liabilities	116,628	114,623
Stockholders' equity	443,714	452,658	619,758
Total liabilities and stockholders' equity	2,161,901	2,151,538
Parent Company
Assets
Cash and cash equivalents	24,042	62,639
Other current assets	8,699	14,997
Property and equipment, net	3,522	1,730
Investment in subsidiaries	551,256	510,260
Intercompany balances	125,440	133,483
Other assets	17,002	18,457
Total assets	729,961	741,566
Liabilities and stockholders' equity
Other current liabilities	31,231	29,363
Long-term debt, excluding current installments	250,000	250,000
Other non-current liabilities	5,016	9,545
Stockholders' equity	443,714	452,658
Total liabilities and stockholders' equity	729,961	741,566
SGI
Assets
Cash and cash equivalents	56	150
Accounts receivable, net	53,531	72,830
Inventories	23,714	29,416
Other current assets	3,409	2,783
Property and equipment, net	166,637	150,130
Investment in subsidiaries	721,909	670,471
Goodwill, net	273,656	273,656
Intangible assets, net	41,520	42,170
Other assets	82,748	98,933
Total assets	1,367,180	1,340,539
Liabilities and stockholders' equity
Debt payments due within one year	6,280	6,280
Other current liabilities	56,050	48,074
Long-term debt, excluding current installments	1,104,884	1,110,573
Other non-current liabilities	38,772	43,188
Intercompany balances	71,603	27,292
Stockholders' equity	89,591	105,132
Total liabilities and stockholders' equity	1,367,180	1,340,539
Guarantor Subsidiaries
Assets
Accounts receivable, net	41,238	45,541
Inventories	16,884	16,210
Other current assets	5,117	4,564
Property and equipment, net	36,028	43,859
Goodwill, net	78,618	78,843
Intangible assets, net	25,849	20,481
Intercompany balances	231,357	164,982
Other assets	12,265	6,046
Total assets	447,356	380,526
Liabilities and stockholders' equity
Other current liabilities	30,140	32,601
Other non-current liabilities	13,427	8,141
Stockholders' equity	403,789	339,784
Total liabilities and stockholders' equity	447,356	380,526
Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	81,482	62,770
Accounts receivable, net	87,698	59,808
Inventories	41,113	23,118
Other current assets	23,277	20,117
Property and equipment, net	220,301	254,862
Investment in subsidiaries	909,379	386,690
Goodwill, net	414,075	411,416
Intangible assets, net	19,490	7,962
Other assets	367,209	335,429
Total assets	2,164,024	1,562,172
Liabilities and stockholders' equity
Debt payments due within one year	19,911	2,151
Other current liabilities	94,682	78,817
Long-term debt, excluding current installments	9,592	27,686
Other non-current liabilities	59,413	53,749
Intercompany balances	285,162	271,186
Stockholders' equity	1,695,264	1,128,583
Total liabilities and stockholders' equity	2,164,024	1,562,172
Eliminating Entries
Assets
Cash and cash equivalents	(1,178)	(1,278)
Investment in subsidiaries	(2,182,544)	(1,567,421)
Intercompany balances	(356,797)	(298,465)
Other assets	(6,101)	(6,101)
Total assets	(2,546,620)	(1,873,265)
Liabilities and stockholders' equity
Other current liabilities	(1,211)	(1,288)
Intercompany balances	(356,765)	(298,478)
Stockholders' equity	(2,188,644)	(1,573,499)
Total liabilities and stockholders' equity	$ (2,546,620)	$ (1,873,265)