Basis of Presentation and Significant Accounting Policies - Schedule of Amounts Reclassified from Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues	$ 686,006	$ 886,136	$ 1,348,023	$ 1,691,559
Other - net	580	1,005	1,902	2,411
Selling, general and administrative expenses	(101,918)	(106,937)	(196,603)	(210,537)
Income before Provision for Income Taxes	34,967	99,245	89,449	160,378
Provision for Income Taxes	(11,475)	(29,544)	(24,803)	(45,801)
Net Income	23,492	69,701	64,646	114,577
Accumulated Other Comprehensive Income Component Recognized [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassification for the period	286	(1,700)	(721)	(2,561)
Accumulated Other Comprehensive Income Component Recognized [Member] | Realized (Losses) Gains on Derivative Financial Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues	(240)	(621)	(77)	(1,152)
Cost of operations	1,153	(1,117)	127	(2,006)
Other - net		101	10	116
Income before Provision for Income Taxes	913	(1,637)	60	(3,042)
Provision for Income Taxes	(234)	395	(13)	753
Net Income	679	(1,242)	47	(2,289)
Accumulated Other Comprehensive Income Component Recognized [Member] | Amortization of Prior Service Cost on Benefit Obligations [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of operations	(509)	(660)	(1,018)	(1,411)
Selling, general and administrative expenses	(86)	(50)	(171)	(100)
Income before Provision for Income Taxes	(595)	(710)	(1,189)	(1,511)
Provision for Income Taxes	198	245	395	518
Net Income	(397)	(465)	(794)	(993)
Accumulated Other Comprehensive Income Component Recognized [Member] | Realized Gain on Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other - net	7	10	41	724
Provision for Income Taxes	(3)	(3)	(15)	(3)
Net Income	$ 4	$ 7	$ 26	$ 721