Summary of Significant Accounting Policies Marketable Securities (Details) - USD ($) $ in Millions	12 Months Ended
Jan. 31, 2016	Jan. 31, 2015
Marketable Securities [Abstract]
Gross Unrealized Gains	$ 0.9	$ 5.1
Gross Unrealized Losses	$ 1.8	$ 1.9

Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Name:	us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration