Consolidated Statements of Operations (Parenthetical) (USD $)	0 Months Ended	12 Months Ended
	Dec. 27, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accelerated cash dividend per share	$ 0.0425
Payment of accelerated cash dividends	$ 2,500,000
Share-based compensation		7,624,000	7,097,000	7,592,000
Cost of revenues [Member]
Share-based compensation		997,000	1,060,000	1,178,000
Research and development [Member]
Share-based compensation		3,197,000	2,875,000	3,132,000
Selling, general and administrative [Member]
Share-based compensation		$ 3,430,000	$ 3,162,000	$ 3,282,000