Investments (Components of Other Comprehensive Income Related to Available-For-Sale Securities) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Other Comprehensive Income Related to Available-For-Sale Securities [Roll Forward]
Accumulated OCI related to available-for-sale securities, beginning of the period	$ 0	$ 17,967	$ (3,760)	$ 17,871
Unrealized gains on available-for-sale securities	0	928	0	1,089
Reclassification adjustment for gains included in net loss	0	(4,004)	(34)	(4,069)
Changes in accumulated OCI on available-for-sale securities, before tax	0	(3,076)	(34)	(2,980)
Deferred income tax benefit	0	0	3,794	0
Changes in accumulated OCI on available-for-sale securities, net of tax	0	(3,076)	3,760	(2,980)
Accumulated OCI related to available-for-sale securities, end of the period	$ 0	$ 14,891	$ 0	$ 14,891