Condensed Consolidating Financial Statements (Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2015	Apr. 30, 2014	Jan. 31, 2014	Apr. 30, 2013
Condensed Financial Statements, Captions [Line Items]
Cash & cash equivalents	$ 1,321,134	$ 2,185,307	$ 437,404	$ 1,747,584
Cash and cash equivalents - restricted	51,085	115,319	44,855
Receivables, net	777,453	191,618	677,221
Prepaid expenses and other current assets	260,802	198,267	345,231
Investments in available-for-sale securities	367,845	423,495
Total current assets	2,778,319	3,114,006	1,504,711
Mortgage loans held for investment, net	245,663	268,428	282,149
Investments in available-for-sale securities	7,883	4,329	443,770
Property and equipment, at cost less accumulated depreciation and amortization of $509,039, $469,733 and $446,049	308,805	304,911	314,565
Intangible assets, net	443,329	355,622	318,719
Goodwill	442,961	436,117	437,386	434,782
Amounts due from affiliates	0	0	0
Other assets	151,981	210,116	213,987
Total assets	4,378,941	4,693,529	3,515,287
Commercial paper borrowings	591,486	0	194,984
Customer deposits	1,286,216	769,785	806,887
Accounts payable, accrued expenses and other current liabilities	472,490	569,007	520,121
Accrued salaries, wages and payroll taxes	118,512	167,032	108,583
Accrued income taxes	1,619	406,655	23,375
Current portion of long-term debt	781	400,637	400,570
Total current liabilities	2,471,104	2,313,116	2,054,520
Long-term debt	505,460	505,837	505,959
Other noncurrent liabilities	255,992	318,027	268,049
Total liabilities	3,232,556	3,136,980	2,828,528
Stockholders’ equity	1,146,385	1,556,549	686,759
Total liabilities and stockholders' equity	4,378,941	4,693,529	3,515,287
Block Financial Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Cash & cash equivalents	969,387	612,376	181,483	558,110
Cash and cash equivalents - restricted	3,459	67,463	4,883
Receivables, net	436,907	89,975	529,954
Prepaid expenses and other current assets	89,490	10,202	14,686
Investments in available-for-sale securities	367,745	423,495
Total current assets	1,866,988	1,203,511	731,006
Mortgage loans held for investment, net	245,663	268,428	282,149
Investments in available-for-sale securities			439,395
Property and equipment, at cost less accumulated depreciation and amortization of $509,039, $469,733 and $446,049	136	121	126
Amounts due from affiliates	459,955	386,818	542,657
Other assets	132,374	173,168	144,759
Total assets	2,705,116	2,032,046	2,140,092
Commercial paper borrowings	591,486		194,984
Customer deposits	1,286,484	770,885	807,507
Accounts payable, accrued expenses and other current liabilities	178,197	223,677	190,857
Accrued salaries, wages and payroll taxes	1,929	2,190	1,823
Accrued income taxes	53,655	71,132	36,058
Current portion of long-term debt		399,882	399,824
Total current liabilities	2,111,751	1,467,766	1,631,053
Long-term debt	497,823	497,612	497,542
Other noncurrent liabilities	25,554	5,766	8,460
Total liabilities	2,635,128	1,971,144	2,137,055
Stockholders’ equity	69,988	60,902	3,037
Total liabilities and stockholders' equity	2,705,116	2,032,046	2,140,092
Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash & cash equivalents	352,015	1,574,031	256,541	1,192,197
Cash and cash equivalents - restricted	47,626	47,856	39,972
Receivables, net	340,546	101,643	147,267
Prepaid expenses and other current assets	245,850	188,065	343,228
Investments in available-for-sale securities	100
Total current assets	986,137	1,911,595	787,008
Investments in available-for-sale securities	7,883	4,329	4,375
Property and equipment, at cost less accumulated depreciation and amortization of $509,039, $469,733 and $446,049	308,669	304,790	314,439
Intangible assets, net	443,329	355,622	318,719
Goodwill	442,961	436,117	437,386
Investments in subsidiaries	69,988	60,902	3,037
Amounts due from affiliates	1,029	397	2,167,747
Other assets	19,607	25,677	59,520
Total assets	2,279,603	3,099,429	4,092,231
Accounts payable, accrued expenses and other current liabilities	293,245	344,573	328,595
Accrued salaries, wages and payroll taxes	116,583	164,842	106,760
Accrued income taxes	22,502	335,523
Current portion of long-term debt	781	755	746
Total current liabilities	433,111	845,693	436,101
Long-term debt	7,637	8,225	8,417
Other noncurrent liabilities	230,438	312,261	259,589
Amounts due to affiliates	973,159	1,028,919	542,657
Total liabilities	1,644,345	2,195,098	1,246,764
Stockholders’ equity	635,258	904,331	2,845,467
Total liabilities and stockholders' equity	2,279,603	3,099,429	4,092,231
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Investments in subsidiaries	635,258	904,331	2,845,467
Amounts due from affiliates	513,204	642,101	0
Other assets		11,271	9,708
Total assets	1,148,462	1,557,703	2,855,175
Accounts payable, accrued expenses and other current liabilities	1,048	757	669
Total current liabilities	1,048	757	669
Amounts due to affiliates	1,029	397	2,167,747
Total liabilities	2,077	1,154	2,168,416
Stockholders’ equity	1,146,385	1,556,549	686,759
Total liabilities and stockholders' equity	1,148,462	1,557,703	2,855,175
Intersegment Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash & cash equivalents	(268)	(1,100)	(620)	(2,723)
Prepaid expenses and other current assets	(74,538)		(12,683)
Total current assets	(74,806)	(1,100)	(13,303)
Investments in subsidiaries	(705,246)	(965,233)	(2,848,504)
Amounts due from affiliates	(974,188)	(1,029,316)	(2,710,404)
Total assets	(1,754,240)	(1,995,649)	(5,572,211)
Customer deposits	(268)	(1,100)	(620)
Accrued income taxes	(74,538)		(12,683)
Total current liabilities	(74,806)	(1,100)	(13,303)
Amounts due to affiliates	(974,188)	(1,029,316)	(2,710,404)
Total liabilities	(1,048,994)	(1,030,416)	(2,723,707)
Stockholders’ equity	(705,246)	(965,233)	(2,848,504)
Total liabilities and stockholders' equity	$ (1,754,240)	$ (1,995,649)	$ (5,572,211)