Other Comprehensive Income (Loss) (Amounts Included in Accumulated Other Comprehensive Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Components of Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (12,171)	$ (5,593)
Amounts reclassified into earnings	2,176	1,017
Changes in fair value	(4,952)	(3,692)
Ending balance	(14,947)	(8,268)
Interest Rate Swap [Member]
Components of Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(6,037)	(4,372)
Amounts reclassified into earnings	1,060	638
Changes in fair value	(4,144)	(3,374)
Ending balance	(9,121)	(7,108)
Fuel [Member] | Commodity Contract [Member]
Components of Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(6,134)	(1,221)
Amounts reclassified into earnings	1,116	379
Changes in fair value	(808)	(318)
Ending balance	$ (5,826)	$ (1,160)