Quarterly Financial Information - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 477,968	$ 322,516	$ 254,344	$ 227,639	$ 337,267	$ 290,516	$ 281,062	$ 272,143	$ 1,282,467	$ 1,180,988	$ 1,244,133
Gross profit	427,425	271,326	204,714	184,774	289,812	243,627	234,799	223,092	1,088,239	991,330	1,039,820
Operating income (loss)	152,582	56,314	6,250	(12,065)	79,454	25,688	39,266	(7,663)	203,081	136,745	187,811
Net income (loss) attributable to Mentor Graphics shareholders	$ 123,103	$ 41,762	$ 3,437	$ (13,436)	$ 60,271	$ 14,679	$ 31,212	$ (9,885)	$ 154,866	$ 96,277	$ 147,139
Basic	$ 1.12	$ 0.38	$ 0.03	$ (0.12)	$ 0.52	$ 0.13	$ 0.27	$ (0.08)	$ 1.42	$ 0.83	$ 1.28
Diluted	$ 1.05	$ 0.37	$ 0.03	$ (0.12)	$ 0.51	$ 0.12	$ 0.26	$ (0.08)	$ 1.37	$ 0.81	$ 1.26
Adjustment of noncontrolling interest to redemption value					$ 0	$ 133	$ (144)	$ 269	$ 0	$ 258	$ 121