Quarterly Financial Information - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 337,267	$ 290,516	$ 281,062	$ 272,143	$ 439,066	$ 292,683	$ 260,233	$ 252,151	$ 1,180,988	$ 1,244,133	$ 1,156,373
Gross profit	289,812	243,627	234,799	223,092	388,666	245,142	211,304	194,708	991,330	1,039,820	969,266
Operating Income	79,454	25,688	39,266	(7,663)	139,532	29,723	16,912	1,644	136,745	187,811	183,040
Net income attributable to Mentor Graphics shareholders	$ 60,271	$ 14,679	$ 31,212	$ (9,885)	$ 114,488	$ 21,030	$ 14,172	$ (2,551)	$ 96,277	$ 147,139	$ 155,258
Basic	$ 0.52	$ 0.13	$ 0.27	$ (0.08)	$ 0.98	$ 0.18	$ 0.13	$ (0.02)	$ 0.83	$ 1.28	$ 1.33
Diluted	$ 0.51	$ 0.12	$ 0.26	$ (0.08)	$ 0.96	$ 0.18	$ 0.13	$ (0.02)	$ 0.81	$ 1.26	$ 1.29
Adjustment of noncontrolling interest to redemption value	$ 0	$ 133	$ (144)	$ 269	$ (1,174)	$ (267)	$ 895	$ 667	$ 258	$ 121	$ (4,486)