Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
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	$ 90,019	$ 109,015	$ 100,403	$ 104,402
Restricted cash	28,543	30,398
Accounts receivable, net	182,503	209,915
Inventories	70,780	71,255
Note receivable	10,373	10,298
Other current assets	53,091	53,782
Net property and equipment	380,684	376,877
Investment in subsidiaries	0	0
Goodwill	782,762	801,328
Intangible assets, net	99,375	84,291
Intercompany balances	0	0
Other assets	436,096	439,749
Total assets	2,134,226	2,186,908
Liabilities and stockholders' equity
Current installments of long-term debt	16,895	16,458
Other current liabilities	218,020	239,889
Long-term debt, excluding current installments	1,450,847	1,451,708
Other non-current liabilities	132,314	114,062
Intercompany balances	0	0
Stockholders’ equity	316,150	364,791
Total liabilities and stockholders’ equity	2,134,226	2,186,908
Parent Company
Assets
Cash and cash equivalents	16,703	27,159
Restricted cash	0	0
Accounts receivable, net	0	0
Inventories	0	0
Note receivable	10,373	10,298
Other current assets	9,059	9,693
Net property and equipment	6,079	5,727
Investment in subsidiaries	492,107	520,969
Goodwill	0	0
Intangible assets, net	0	0
Intercompany balances	58,739	79,735
Other assets	7,685	6,479
Total assets	600,745	660,060
Liabilities and stockholders' equity
Current installments of long-term debt	0	0
Other current liabilities	17,573	28,485
Long-term debt, excluding current installments	250,000	250,000
Other non-current liabilities	17,022	16,784
Intercompany balances	0	0
Stockholders’ equity	316,150	364,791
Total liabilities and stockholders’ equity	600,745	660,060
SGI
Assets
Cash and cash equivalents	151	201
Restricted cash	0	0
Accounts receivable, net	59,790	63,944
Inventories	25,281	25,411
Note receivable	0
Other current assets	4,111	3,809
Net property and equipment	147,453	154,243
Investment in subsidiaries	813,544	802,425
Goodwill	253,928	253,928
Intangible assets, net	41,816	42,000
Intercompany balances	0	0
Other assets	74,230	74,923
Total assets	1,420,304	1,420,884
Liabilities and stockholders' equity
Current installments of long-term debt	6,280	6,280
Other current liabilities	54,624	58,473
Long-term debt, excluding current installments	1,197,849	1,199,247
Other non-current liabilities	25,771	25,560
Intercompany balances	144,608	136,402
Stockholders’ equity	(8,828)	(5,078)
Total liabilities and stockholders’ equity	1,420,304	1,420,884
Guarantor Subsidiaries
Assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Accounts receivable, net	28,966	29,156
Inventories	15,191	16,063
Note receivable	0	0
Other current assets	7,340	6,773
Net property and equipment	33,697	32,957
Investment in subsidiaries	0	0
Goodwill	76,742	76,741
Intangible assets, net	38,369	20,367
Intercompany balances	310,248	302,396
Other assets	8,575	7,507
Total assets	519,128	491,960
Liabilities and stockholders' equity
Current installments of long-term debt	0	0
Other current liabilities	31,928	35,436
Long-term debt, excluding current installments	0	0
Other non-current liabilities	31,876	12,174
Intercompany balances	0	0
Stockholders’ equity	455,324	444,350
Total liabilities and stockholders’ equity	519,128	491,960
Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	74,647	82,834
Restricted cash	28,543	30,398
Accounts receivable, net	93,747	116,815
Inventories	30,308	29,781
Note receivable	0	0
Other current assets	32,581	33,507
Net property and equipment	193,455	183,950
Investment in subsidiaries	855,802	855,801
Goodwill	452,092	470,659
Intangible assets, net	19,190	21,924
Intercompany balances	0	0
Other assets	348,219	353,455
Total assets	2,128,584	2,179,124
Liabilities and stockholders' equity
Current installments of long-term debt	10,615	10,178
Other current liabilities	115,383	118,682
Long-term debt, excluding current installments	2,998	2,461
Other non-current liabilities	57,645	59,544
Intercompany balances	224,398	245,748
Stockholders’ equity	1,717,545	1,742,511
Total liabilities and stockholders’ equity	2,128,584	2,179,124
Eliminating Entries
Assets
Cash and cash equivalents	(1,482)	(1,179)
Restricted cash	0	0
Accounts receivable, net	0	0
Inventories	0	0
Note receivable	0	0
Other current assets	0	0
Net property and equipment	0	0
Investment in subsidiaries	(2,161,453)	(2,179,195)
Goodwill	0	0
Intangible assets, net	0	0
Intercompany balances	(368,987)	(382,131)
Other assets	(2,613)	(2,615)
Total assets	(2,534,535)	(2,565,120)
Liabilities and stockholders' equity
Current installments of long-term debt	0	0
Other current liabilities	(1,488)	(1,187)
Long-term debt, excluding current installments	0	0
Other non-current liabilities	0	0
Intercompany balances	(369,006)	(382,150)
Stockholders’ equity	(2,164,041)	(2,181,783)
Total liabilities and stockholders’ equity	$ (2,534,535)	$ (2,565,120)