Condensed Consolidating Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
REVENUES	$ 464,134	$ 474,935	$ 463,331	$ 447,385	$ 447,835	$ 459,957	$ 459,295	$ 426,000	$ 1,849,785	$ 1,793,087	$ 1,646,867
EXPENSES:
Operating									1,275,586	1,256,128	1,156,135
General and administrative									107,027	103,936	106,429
Depreciation and amortization									166,746	151,514	113,925
Asset impairments										955	30,082
Restructuring charges									4,010	0	0
Costs and Expenses									1,553,369	1,512,533	1,406,571
Operating income	80,359	73,953	77,176	64,928	66,539	65,436	79,753	68,826	296,416	280,554	240,296
OTHER (INCOME) EXPENSE:
Interest expense, net									67,755	49,696	39,535
Expenses associated with debt refinancing transactions									0	701	0
Other (income) expense									489	(58)	(1,204)
Total non-operating expense (income)									68,244	50,339	38,331
INCOME BEFORE INCOME TAXES									228,172	230,215	201,965
Income tax expense									(8,253)	(8,361)	(6,943)
INCOME BEFORE EQUITY IN SUBSIDIARIES									219,919	221,854	195,022
NET INCOME	$ 60,689	$ 55,340	$ 57,583	$ 46,307	$ 48,598	$ 50,676	$ 65,303	$ 57,277	219,919	221,854	195,022
Parent
Condensed Financial Statements, Captions [Line Items]
REVENUES									1,182,765	1,184,878	1,250,199
EXPENSES:
Operating									904,750	889,203	896,470
General and administrative									35,440	33,248	33,508
Depreciation and amortization									84,842	82,745	80,820
Asset impairments											29,915
Restructuring charges									197
Costs and Expenses									1,025,229	1,005,196	1,040,713
Operating income									157,536	179,682	209,486
OTHER (INCOME) EXPENSE:
Interest expense, net									51,928	35,919	35,138
Expenses associated with debt refinancing transactions										701
Other (income) expense									995	232	302
Total non-operating expense (income)									52,923	36,852	35,440
INCOME BEFORE INCOME TAXES									104,613	142,830	174,046
Income tax expense									(1,896)	(1,541)	(552)
INCOME BEFORE EQUITY IN SUBSIDIARIES									102,717	141,289	173,494
Income from equity in subsidiaries									117,202	80,565	21,528
NET INCOME									219,919	221,854	195,022
Combined Subsidiary Guarantors
Condensed Financial Statements, Captions [Line Items]
REVENUES									1,542,231	1,469,105	1,268,654
EXPENSES:
Operating									1,246,047	1,227,821	1,131,651
General and administrative									71,587	70,688	72,921
Depreciation and amortization									81,904	68,769	33,105
Asset impairments										955	167
Restructuring charges									3,813
Costs and Expenses									1,403,351	1,368,233	1,237,844
Operating income									138,880	100,872	30,810
OTHER (INCOME) EXPENSE:
Interest expense, net									15,827	13,777	4,397
Other (income) expense									(548)	(414)	(786)
Total non-operating expense (income)									15,279	13,363	3,611
INCOME BEFORE INCOME TAXES									123,601	87,509	27,199
Income tax expense									(6,357)	(6,820)	(6,391)
INCOME BEFORE EQUITY IN SUBSIDIARIES									117,244	80,689	20,808
NET INCOME									117,244	80,689	20,808
Consolidating Adjustments and Other
Condensed Financial Statements, Captions [Line Items]
REVENUES									(875,211)	(860,896)	(871,986)
EXPENSES:
Operating									(875,211)	(860,896)	(871,986)
Costs and Expenses									(875,211)	(860,896)	(871,986)
OTHER (INCOME) EXPENSE:
Other (income) expense									42	124	(720)
Total non-operating expense (income)									42	124	(720)
INCOME BEFORE INCOME TAXES									(42)	(124)	720
INCOME BEFORE EQUITY IN SUBSIDIARIES									(42)	(124)	720
Income from equity in subsidiaries									(117,202)	(80,565)	(21,528)
NET INCOME									$ (117,244)	$ (80,689)	$ (20,808)