Investments (Components of Other Comprehensive Income Related to Available-For-Sale Securities) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 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	$ 10,260	$ (8,391)	$ 13,240
Unrealized gains on available-for-sale securities	0	(1,376)	0	(287)
Reclassification adjustment for gains included in net loss	0	(87)	(34)	(4,156)
Changes in accumulated OCI on available-for-sale securities, before tax	0	(1,463)	(34)	(4,443)
Deferred income tax benefit	0	0	8,425	0
Changes in accumulated OCI on available-for-sale securities, net of tax	0	(1,463)	8,391	(4,443)
Accumulated OCI related to available-for-sale securities, end of the period	$ 0	$ 8,797	$ 0	$ 8,797