Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Revenues:
System and software	$ 166,301	$ 154,363	$ 455,614	$ 411,503
Service and support	102,459	96,145	301,875	282,780
Total revenues	268,760	250,508	757,489	694,283
Cost of revenues:
System and software	19,214	10,864	49,296	41,235
Service and support	29,290	27,621	86,834	79,676
Amortization of purchased technology	1,759	1,761	6,092	7,872
Total cost of revenues	50,263	40,246	142,222	128,783
Gross margin	218,497	210,262	615,267	565,500
Operating expenses:
Research and development	76,214	81,305	220,211	220,578
Marketing and selling	84,673	83,036	243,493	236,718
General and administration	17,794	17,922	54,308	52,055
Equity in (earnings) losses of Frontline	(381)	134	(1,630)	(2,022)
Amortization of intangible assets	1,242	1,296	4,547	4,361
Special charges	1,146	1,164	3,800	7,388
Total operating expenses	180,688	184,857	524,729	519,078
Operating income	37,809	25,405	90,538	46,422
Other income (expense), net	57	1,836	(239)	1,890
Interest expense	(4,652)	(4,615)	(13,983)	(26,689)
Income before income tax	33,214	22,626	76,316	21,623
Income tax expense (benefit)	1,148	(1,445)	(835)	(4,429)
Net income	32,066	24,071	77,151	26,052
Less: Income attributable to noncontrolling interest	1,425	0	161	0
Net income attributable to Mentor Graphics shareholders	$ 30,641	$ 24,071	$ 76,990	$ 26,052
Net income per share:
Basic (in dollars per share)	$ 0.27	$ 0.22	$ 0.70	$ 0.24
Diluted (in dollars per share)	$ 0.27	$ 0.22	$ 0.68	$ 0.23
Weighted average number of shares outstanding:
Basic (in shares)	111,575	109,501	110,454	110,423
Diluted (in shares)	114,721	111,563	113,584	113,181