Significant Accounting Policies Net Income Per Share (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of weighted-average shares used in computing net income per share
Weighted average common shares outstanding	59,623,000	61,609,000	62,030,000
Dilutive effect of stock options outstanding using the treasury stock method	665,000	762,000	527,000
Shares used in computing diluted net income per share attributable to Micrel Incorporated shareholders	60,288,000	62,371,000	62,557,000
Stock options excluded from the weighted-average number of common shares outstanding for the diluted net income per share computations as they were anti-dilutive	5,200,000	4,100,000	4,000,000