Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Condensed Income Statements, Captions [Line Items]
Operating revenues, net	$ 210,760	$ 216,294	$ 212,145	$ 197,071	$ 281,227	$ 200,762	$ 195,543	$ 178,968	$ 836,270		$ 856,500		$ 646,686
Expenses:
Direct expenses									670,007		713,090		543,524
Selling, general, and administrative expenses									43,171		38,820		39,051
Total operating expenses									713,178		751,910		582,575
(Gain) loss on disposition of assets, net	(523)	56	242	1,073	529	1,399	14,701	(25)	848		(16,604)		317
Impairment of assets									10,508		1,648
Equity in loss of unconsolidated affiliate									96		262		863
Operating income									111,640		119,284		62,931
Interest expense									29,510		29,756		29,533
Loss on debt extinguishment									29,833
Other (income) expense, net									(818)		(613)		(651)
Total expenses									58,525		29,143		28,882
Earnings before income taxes	11,651	28,277	21,700	(8,513)	18,674	24,212	32,525	14,730	53,115		90,141		34,049
Income tax expense									20,427		31,185		15,992
Net earnings	7,392	17,249	13,368	(5,321)	16,825	13,777	19,516	8,838	32,688		58,956		18,057
Parent Company Only (issuer) [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net									504,180		564,445		415,740
Expenses:
Direct expenses									411,398		468,321		355,689
Selling, general, and administrative expenses									32,985		29,885		31,384
Management fees											(11,682)		(9,238)
Total operating expenses									444,383		486,524		377,835
(Gain) loss on disposition of assets, net									848		(16,585)		317
Impairment of assets									10,508		1,227
Equity in loss of unconsolidated affiliate									96		262		863
Operating income									48,345		93,017		36,725
Equity in net earnings of consolidated subsidiaries									(38,740)		(15,567)		(15,714)
Interest expense									29,510		29,434		29,518
Loss on debt extinguishment									29,833
Other (income) expense, net									(819)		(613)		(651)
Total expenses									19,784		13,254		13,153
Earnings before income taxes									28,561		79,763		23,572
Income tax expense									(4,127)		20,807		5,515
Net earnings									32,688		58,956		18,057
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net									332,090	[1]	292,055	[1]	230,946	[1]
Expenses:
Direct expenses									258,627	[1]	244,769	[1]	187,835	[1]
Selling, general, and administrative expenses									10,186	[1]	8,935	[1]	7,667	[1]
Management fees											11,682	[1]	9,238	[1]
Total operating expenses									268,813	[1]	265,386	[1]	204,740	[1]
(Gain) loss on disposition of assets, net											(19)	[1]
Impairment of assets											421	[1]
Operating income									63,277	[1]	26,267	[1]	26,206	[1]
Interest expense											322	[1]	15	[1]
Other (income) expense, net									(17)	[1]
Total expenses									(17)	[1]	322	[1]	15	[1]
Earnings before income taxes									63,294	[1]	25,945	[1]	26,191	[1]
Income tax expense									24,554	[1]	10,378	[1]	10,477	[1]
Net earnings									38,740	[1]	15,567	[1]	15,714	[1]
Eliminations [Member]
Expenses:
Direct expenses									(18)
Total operating expenses									(18)
Operating income									18
Equity in net earnings of consolidated subsidiaries									38,740		15,567		15,714
Other (income) expense, net									18
Total expenses									38,758		15,567		15,714
Earnings before income taxes									(38,740)		(15,567)		(15,714)
Net earnings									$ (38,740)		$ (15,567)		$ (15,714)

[1] Foreign subsidiaries represent minor subsidiaries and are included in the guarantors' subsidiaries amounts.