Stockholders' Equity Rollforward of OCI (Details) (USD $)	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Marketable Securities, Realized Gain (Loss)	$ (18,300,000)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	3,334,000	6,809,000	8,569,000	10,755,000
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	1,843,000	3,741,000	3,576,000	478,000
Accumulated other comprehensive income	5,177,000	10,550,000	12,145,000	11,233,000
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(822,000)	(1,481,000)	1,884,000
Other Comprehensive Income (Loss), Before Reclassifications, Tax	846,000	10,000	878,000
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1,668,000)	(1,491,000)	1,006,000
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	(5,835,000)	(175,000)	(152,000)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Tax	0	0	0
Tax effect of reclassification adjustment for gains included in income	2,130,000	71,000	58,000
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(3,705,000)	(104,000)	(94,000)
Unrealized translation gain	(3,475,000)	(1,760,000)	(2,186,000)
Change in net unrealized gain on available-for-sale securities	(1,898,000)	165,000	3,098,000
Other comprehensive income (loss)	(5,373,000)	(1,595,000)	912,000
Other-than-temporary impairments of AFS securities	12,400,000		12,400,000
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(3,416,000)	(1,979,000)	(3,429,000)
Other Comprehensive Income (Loss), Before Reclassifications, Tax	59,000	(219,000)	(1,243,000)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(3,475,000)	(1,760,000)	(2,186,000)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	2,594,000	498,000	5,313,000
Other Comprehensive Income (Loss), Before Reclassifications, Tax	787,000	229,000	2,121,000
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	$ 1,807,000	$ 269,000	$ 3,192,000