Business Combinations - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2017	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Jan. 31, 2017
Business Acquisition [Line Items]
Business combinations, net of cash acquired		$ 0	$ 2,798,194	$ 19,781	$ 2,799,993
Goodwill		$ 7,294,381		$ 7,294,381		$ 7,263,846
Sequence, Inc. [Member]
Business Acquisition [Line Items]
Business combinations, net of cash acquired	$ 26,000
Intangible assets	2,700
Goodwill	$ 23,000