Income Taxes (Details 6) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 03, 2015		Dec. 28, 2013		Dec. 29, 2012
Unrecognized Tax Benefits
Unrecognized tax benefits at the beginning of the fiscal year	$ 78,279		$ 92,378		$ 98,812
Gross amount of the increases (decreases) in unrecognized tax benefits of tax positions taken during a prior year	8,301	[1]	6,196	[1]	2,194	[1]
Gross amount of the increases in unrecognized tax benefits as a result of tax positions taken during the current year	12,381		5,119		3,082
Amount of decreases in unrecognized tax benefits relating to settlements with taxing authorities, including the utilization of tax attributes	0		(15,171)		(11,768)
Reductions to unrecognized tax benefits resulting from the lapse of the applicable statute of limitations	(86)		(11,850)		(189)
Effect of foreign currency translation	(1,651)		1,607		247
Unrecognized tax benefits at the end of the fiscal year	97,224		78,279		92,378
Total amounts of unrecognized tax benefits that, if upon resolution of the uncertain tax positions would reduce Cadence's effective tax rate	57,127		49,458		57,725
Interest and penalties recognized in Income Statements
Interest	255		(12,470)		(11,184)
Penalties	(748)		(7,698)		(1,862)
Interest and penalties recognized in Balance Sheets
Interest	1,155		37
Penalties	$ 446		$ 1,227

[1] Includes unrecognized tax benefits of tax positions recorded in connection with acquisitions