Segment Information (Details) (USD $) | 3 Months Ended | 9 Months Ended |
In Thousands, unless otherwise specified | Jan. 31, 2014 | Jan. 31, 2013 | Jan. 31, 2014 | Jan. 31, 2013 |
| CoreBusinesses |
Segment Information [Abstract] | ' | ' | ' | ' |
Number of core businesses | ' | ' | 3 | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | $457,933 | $472,435 | $1,318,106 | $1,314,924 |
Contribution to Profit | 112,936 | 114,647 | 283,193 | 271,022 |
Unallocated Shared Services and Administrative Costs | -39,556 | -31,021 | -124,062 | -85,460 |
Operating Income | 73,380 | 83,626 | 159,131 | 185,562 |
Research [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | 248,797 | 240,902 | 747,532 | 726,679 |
Direct contribution to profit | 103,244 | 100,369 | 309,832 | 300,624 |
Research [Member] | Distribution [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -11,011 | -11,495 | -33,714 | -34,813 |
Research [Member] | Technology Services [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -17,727 | -16,517 | -54,307 | -49,736 |
Research [Member] | Occupancy and Other [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -4,707 | -4,642 | -15,581 | -16,412 |
Research [Member] | Contribution to Profit (Loss) [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Contribution to Profit | 69,799 | 67,715 | 206,230 | 199,663 |
Professional Development [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | 94,201 | 113,106 | 270,832 | 316,360 |
Direct contribution to profit | 31,740 | 30,780 | 76,759 | 71,949 |
Professional Development [Member] | Distribution [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -9,320 | -10,196 | -27,861 | -30,937 |
Professional Development [Member] | Technology Services [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -7,543 | -7,238 | -23,260 | -21,662 |
Professional Development [Member] | Occupancy and Other [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -2,117 | -1,469 | -7,694 | -8,054 |
Professional Development [Member] | Contribution to Profit (Loss) [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Contribution to Profit | 12,760 | 11,877 | 17,944 | 11,296 |
Education [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | 114,935 | 118,427 | 299,742 | 271,885 |
Direct contribution to profit | 44,505 | 48,376 | 102,687 | 99,150 |
Education [Member] | Distribution [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -4,012 | -4,074 | -11,755 | -11,646 |
Education [Member] | Technology Services [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -8,429 | -8,049 | -25,802 | -22,548 |
Education [Member] | Occupancy and Other [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -1,687 | -1,198 | -6,111 | -4,893 |
Education [Member] | Contribution to Profit (Loss) [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Contribution to Profit | $30,377 | $35,055 | $59,019 | $60,063 |