Subsidiary Guarantors (Schedule of Condensed Consolidating Balance Sheet) (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Apr. 30, 2012	Jan. 31, 2012	Apr. 30, 2011
CURRENT ASSETS:
Cash and cash equivalents	$ 1,112	$ 4,534	$ 1,131	$ 1,817
Accounts receivable - trade, net of allowance for doubtful accounts	50,425	47,472
Refundable income taxes	1,209	1,281
Prepaid expenses	8,961	6,077
Deferred income taxes	3,253	3,712
Other current assets	854	609
Total current assets	69,813	67,356
Property, plant and equipment, net of accumulated depreciation and amortization	428,452	416,717
Goodwill	116,281	101,706
Intangible assets	11,979	2,970
Restricted assets	523	424
Notes receivable - related party/employee	516	722
Investments in unconsolidated entities	19,431	22,781
Other non-current assets	26,158	21,067
Total non-current assets	603,340	566,387
Total assets	673,153	633,743	674,369
CURRENT LIABILITIES:
Current maturities of long-term debt and capital leases	992	1,228
Current maturities of financing lease obligations	355	338
Accounts payable	47,695	46,709
Accrued interest	12,702	9,803
Current accrued capping, closure and post-closure costs	4,903	4,907
Other current liabilities	31,944	35,153
Total current liabilities	98,591	88,335
Long-term debt and capital leases, less current maturities	490,686	473,381
Financing lease obligations, less current maturities	1,549	1,818
Accrued capping, closure and post-closure costs, less current portion	37,681	34,722
Other long-term liabilities	11,753	11,920
Casella Waste Systems, Inc. stockholders' equity:
Additional paid-in capital	335,451	288,348
Accumulated deficit	(310,982)	(270,235)
Accumulated other comprehensive income (loss)	(619)	(1,952)
Total Casella Waste Systems, Inc. stockholders' equity	24,247	16,431
Noncontrolling interest	2,688	1,800
Total stockholders' equity	26,935	18,231
Total liabilities and stockholders' equity	673,153	633,743
Class A Common Stock [Member]
Casella Waste Systems, Inc. stockholders' equity:
Common stock	387	260
Total stockholders' equity	387	260
Class B Common Stock [Member]
Casella Waste Systems, Inc. stockholders' equity:
Common stock	10	10
Total stockholders' equity	10	10
Parent [Member]
CURRENT ASSETS:
Cash and cash equivalents	820	3,799	942	1,531
Accounts receivable - trade, net of allowance for doubtful accounts	229	652
Refundable income taxes		1,281
Prepaid expenses	3,308
Deferred income taxes		3,712
Other current assets	4,831	1,903
Total current assets	9,188	11,347
Property, plant and equipment, net of accumulated depreciation and amortization	3,024	3,486
Goodwill
Intangible assets	272	340
Notes receivable - related party/employee	516	722
Investments in unconsolidated entities	16,486	15,986
Investments in subsidiaries	(47,081)	(34,443)
Other non-current assets	15,010	15,056
Total non-current assets	(11,773)	1,147
Intercompany receivable	577,898	532,950
Total assets	575,313	545,444
CURRENT LIABILITIES:
Current maturities of long-term debt and capital leases	37	142
Current maturities of financing lease obligations
Accounts payable	22,111	21,952
Accrued interest	12,691
Current accrued capping, closure and post-closure costs
Other current liabilities	14,790	23,738
Total current liabilities	49,629	45,832
Long-term debt and capital leases, less current maturities	489,908	472,028
Financing lease obligations, less current maturities
Accrued capping, closure and post-closure costs, less current portion
Other long-term liabilities	11,529	11,153
Casella Waste Systems, Inc. stockholders' equity:
Additional paid-in capital	335,451	288,348
Accumulated deficit	(310,982)	(270,235)
Accumulated other comprehensive income (loss)	(619)	(1,952)
Total Casella Waste Systems, Inc. stockholders' equity	24,247	16,431
Noncontrolling interest
Total stockholders' equity	24,247	16,431
Total liabilities and stockholders' equity	575,313	545,444
Parent [Member] | Class A Common Stock [Member]
Casella Waste Systems, Inc. stockholders' equity:
Common stock	387	260
Parent [Member] | Class B Common Stock [Member]
Casella Waste Systems, Inc. stockholders' equity:
Common stock	10	10
Guarantors [Member]
CURRENT ASSETS:
Cash and cash equivalents	227	368	138	286
Accounts receivable - trade, net of allowance for doubtful accounts	49,756	46,820
Prepaid expenses	5,653
Other current assets	4,419	8,454
Total current assets	60,055	55,642
Property, plant and equipment, net of accumulated depreciation and amortization	416,934	409,383
Goodwill	116,281	101,706
Intangible assets	11,707	2,630
Restricted assets		424
Investments in unconsolidated entities	2,239	2,225
Other non-current assets	11,671	6,011
Total non-current assets	558,832	522,379
Intercompany receivable	(539,265)	(494,819)
Total assets	79,622	83,202
CURRENT LIABILITIES:
Current maturities of long-term debt and capital leases	955	1,086
Current maturities of financing lease obligations	355	338
Accounts payable	24,754	24,757
Accrued interest	11
Current accrued capping, closure and post-closure costs	4,903	4,907
Other current liabilities	16,849	10,872
Total current liabilities	47,827	41,960
Long-term debt and capital leases, less current maturities	778	1,353
Financing lease obligations, less current maturities	1,549	1,818
Accrued capping, closure and post-closure costs, less current portion	37,637	34,681
Other long-term liabilities	6,182	6,103
Casella Waste Systems, Inc. stockholders' equity:
Additional paid-in capital	45,391	46,279
Accumulated deficit	(59,851)	(49,097)
Accumulated other comprehensive income (loss)	9	5
Total Casella Waste Systems, Inc. stockholders' equity	(14,351)	(2,713)
Total stockholders' equity	(14,351)	(2,713)
Total liabilities and stockholders' equity	79,622	83,202
Guarantors [Member] | Class A Common Stock [Member]
Casella Waste Systems, Inc. stockholders' equity:
Common stock	100	100
Non-Guarantors [Member]
CURRENT ASSETS:
Cash and cash equivalents	65	367	51
Accounts receivable - trade, net of allowance for doubtful accounts	440
Other current assets	65
Total current assets	570	367
Property, plant and equipment, net of accumulated depreciation and amortization	8,494	3,848
Investments in unconsolidated entities	2,638	6,502
Total non-current assets	11,132	10,350
Intercompany receivable	(40,565)	(40,063)
Total assets	(28,863)	(29,346)
CURRENT LIABILITIES:
Current maturities of long-term debt and capital leases
Accounts payable	830
Other current liabilities	305	543
Total current liabilities	1,135	543
Accrued capping, closure and post-closure costs, less current portion	44	41
Casella Waste Systems, Inc. stockholders' equity:
Additional paid-in capital	5,608	1,998
Accumulated deficit	(37,710)	(34,140)
Accumulated other comprehensive income (loss)	(628)	412
Total Casella Waste Systems, Inc. stockholders' equity	(32,730)	(31,730)
Noncontrolling interest	2,688	1,800
Total stockholders' equity	(30,042)	(29,930)
Total liabilities and stockholders' equity	(28,863)	(29,346)
Elimination [Member]
CURRENT ASSETS:
Cash and cash equivalents
Investments in unconsolidated entities	(1,932)	(1,932)
Investments in subsidiaries	47,081	34,443
Total non-current assets	45,149	32,511
Intercompany receivable	1,932	1,932
Total assets	47,081	34,443
CURRENT LIABILITIES:
Current maturities of long-term debt and capital leases
Other current liabilities
Total current liabilities
Casella Waste Systems, Inc. stockholders' equity:
Additional paid-in capital	(50,999)	(48,277)
Accumulated deficit	97,561	83,237
Accumulated other comprehensive income (loss)	619	(417)
Total Casella Waste Systems, Inc. stockholders' equity	47,081	34,443
Total stockholders' equity	47,081	34,443
Total liabilities and stockholders' equity	47,081	34,443
Elimination [Member] | Class A Common Stock [Member]
Casella Waste Systems, Inc. stockholders' equity:
Common stock	$ (100)	$ (100)