Subsidiary Guarantors (Schedule Of Consolidating Statements Of Comprehensive Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2012	Jul. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net (loss) income attributable to common stockholders	$ (8,379)	$ (3,062)
Other comprehensive income (loss), net of taxes:
Unrealized income resulting from changes in fair value of derivative instruments	(2,083)	242
Realized income (loss) on derivative instruments reclassified into earnings	44	(355)
Unrealized loss resulting from changes in fair value of marketable securities	(6)	(6)
Other comprehensive income (loss)	(2,045)	(119)
Comprehensive income (loss)	(10,424)	(3,181)
Less: Comprehensive loss attributable to noncontrolling interest	(8)
Comprehensive (loss) income attributable to common stockholders	(10,416)	(3,181)
Casella Waste Systems Inc [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income attributable to common stockholders	(8,379)	(3,062)
Other comprehensive income (loss), net of taxes:
Unrealized income resulting from changes in fair value of derivative instruments	(1,257)	116
Realized income (loss) on derivative instruments reclassified into earnings		(78)
Other comprehensive income (loss)	(1,257)	38
Comprehensive income (loss)	(9,636)
Less: Comprehensive loss attributable to noncontrolling interest	(8)
Comprehensive (loss) income attributable to common stockholders	(9,628)	(3,024)
Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income attributable to common stockholders	(3,556)	509
Other comprehensive income (loss), net of taxes:
Unrealized loss resulting from changes in fair value of marketable securities	(6)	(6)
Other comprehensive income (loss)	(6)	(6)
Comprehensive income (loss)	(3,562)
Comprehensive (loss) income attributable to common stockholders	(3,562)	503
Non-Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income attributable to common stockholders	(16)	(1)
Other comprehensive income (loss), net of taxes:
Unrealized income resulting from changes in fair value of derivative instruments	(826)	126
Realized income (loss) on derivative instruments reclassified into earnings	44	(277)
Other comprehensive income (loss)	(782)	(151)
Comprehensive income (loss)	(798)
Comprehensive (loss) income attributable to common stockholders	(798)	(152)
Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income attributable to common stockholders	3,572	(508)
Other comprehensive income (loss), net of taxes:
Comprehensive income (loss)	3,572
Comprehensive (loss) income attributable to common stockholders	$ 3,572	$ (508)