Other Comprehensive Income (Loss) (Amounts Included in Accumulated Other Comprehensive Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (5,593)	$ (1,869)
Amounts reclassified into earnings	5,148	2,317	$ 3,483
Changes in fair value	(11,726)	(6,041)	813
Ending balance	(12,171)	(5,593)	(1,869)
Interest Rate Swap [Member]
Components of Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4,372)	(3,226)
Amounts reclassified into earnings	3,155	2,824	3,483
Changes in fair value	(4,820)	(3,970)	188
Ending balance	(6,037)	(4,372)	(3,226)
Fuel [Member] | Commodity Contract [Member]
Components of Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,221)	1,357
Amounts reclassified into earnings	1,993	(507)
Changes in fair value	(6,906)	(2,071)	625
Ending balance	$ (6,134)	$ (1,221)	$ 1,357