Quarterly Financial Information - Unaudited (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 401,000	$ 275,642	$ 253,216	$ 226,515	$ 331,238	$ 268,760	$ 240,811	$ 247,918	$ 1,156,373	$ 1,088,727	$ 1,014,638
Gross profit	345,003	229,570	208,359	186,334	283,770	218,497	194,235	202,535	969,266	899,037	841,180
Operating Income	117,197	33,372	26,578	5,893	71,095	37,809	19,907	32,822	183,040	161,633	112,192
Net income attributable to Mentor Graphics shareholders	105,536	25,535	23,982	205	61,746	30,641	18,167	28,182	155,258	138,736	83,872
Basic (in dollars per share)	$ 0.91	$ 0.21	$ 0.19	$ 0.01	$ 0.50	$ 0.27	$ 0.17	$ 0.26	$ 1.33	$ 1.20	$ 0.76
Diluted (in dollars per share)	$ 0.89	$ 0.20	$ 0.19	$ 0.01	$ 0.49	$ 0.27	$ 0.16	$ 0.25	$ 1.29	$ 1.17	$ 0.74
Non-controlling interest adjustment to redemption value	$ (573)	$ (2,032)	$ (2,349)	$ 468	$ (5,272)	$ 0	$ 0	$ 0	$ (4,486)	$ (5,272)	$ 0