SEGMENT INFORMATION (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenue:
Total revenue	$ 300,034	$ 291,669	$ 588,968	$ 562,064
Income (loss) from operations:
Income from operations	28,947	27,310	51,177	49,386
Information services
Revenue:
Total revenue	230,655	225,584	456,259	436,240
Income (loss) from operations:
Income from operations	23,211	22,952	43,383	43,831
Information products
Revenue:
Total revenue	69,379	66,085	132,709	125,824
Income (loss) from operations:
Income from operations	8,201	4,436	10,503	5,576
Other
Income (loss) from operations:
Income from operations	$ (2,465)	$ (78)	$ (2,709)	$ (21)