Business Combination - OTSS (Details) - USD ($)		12 Months Ended
	Dec. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisitions
Acquisitions of businesses, net of cash acquired		$ 12,146,000	$ 28,177,000	$ 2,813,000
Preliminary allocation of fair value of the acquisition:
Goodwill		$ 411,203,000	402,934,000	385,750,000	$ 384,341,000
OTSS
Business Acquisitions
Acquisitions of businesses, net of cash acquired	$ 2,800,000
Goodwill, amount expected to be tax deductible	$ 0
Preliminary allocation of fair value of the acquisition:
Current assets				39,000
Deferred income tax asset				34,000
Goodwill				1,763,000
Intangibles:
Total assets acquired				2,836,000
Liabilities assumed:
Deferred revenue				13,000
Other current liabilities				10,000
Net assets acquired				2,813,000
OTSS | Proprietary technology
Intangibles:
Intangibles				1,000,000
General and administrative | OTSS
Other information
Transaction expenses			$ 37,000	$ 55,000