Segment Information (Details) (USD $) | 3 Months Ended | 6 Months Ended |
In Thousands, unless otherwise specified | Oct. 31, 2013 | Oct. 31, 2012 | Oct. 31, 2013 | Oct. 31, 2012 |
| CoreBusinesses |
Segment Information [Abstract] | ' | ' | ' | ' |
Number of core businesses | ' | ' | 3 | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | $449,153 | $431,755 | $860,173 | $842,489 |
Contribution to Profit | 99,946 | 88,874 | 170,257 | 156,375 |
Unallocated Shared Services and Administrative Costs | -49,759 | -25,933 | -84,506 | -54,439 |
Operating Income | 50,187 | 62,941 | 85,751 | 101,936 |
Research [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | 252,947 | 249,831 | 498,735 | 485,777 |
Direct contribution to profit | 104,745 | 108,992 | 206,588 | 200,255 |
Research [Member] | Distribution [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -11,431 | -11,759 | -22,703 | -23,318 |
Research [Member] | Technology Services [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -17,627 | -17,546 | -36,580 | -33,219 |
Research [Member] | Occupancy and Other [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -5,410 | -6,051 | -10,874 | -11,770 |
Research [Member] | Contribution to Profit (Loss) [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Contribution to Profit | 70,277 | 73,636 | 136,431 | 131,948 |
Professional Development [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | 92,545 | 101,281 | 176,631 | 203,254 |
Direct contribution to profit | 26,905 | 19,963 | 45,019 | 41,169 |
Professional Development [Member] | Distribution [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -9,098 | -10,367 | -18,541 | -20,741 |
Professional Development [Member] | Technology Services [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -7,894 | -7,252 | -15,717 | -14,424 |
Professional Development [Member] | Occupancy and Other [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -2,852 | -3,249 | -5,577 | -6,585 |
Professional Development [Member] | Contribution to Profit (Loss) [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Contribution to Profit | 7,061 | -905 | 5,184 | -581 |
Education [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenue | 103,661 | 80,643 | 184,807 | 153,458 |
Direct contribution to profit | 37,216 | 28,871 | 58,182 | 50,774 |
Education [Member] | Distribution [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -3,739 | -3,779 | -7,743 | -7,572 |
Education [Member] | Technology Services [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -8,639 | -7,138 | -17,373 | -14,499 |
Education [Member] | Occupancy and Other [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Allocated Shared Services and Administrative Costs | -2,230 | -1,811 | -4,424 | -3,695 |
Education [Member] | Contribution to Profit (Loss) [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Contribution to Profit | $22,608 | $16,143 | $28,642 | $25,008 |