Business Acquisitions (Details textual) - USD ($) $ in Thousands				3 Months Ended
	Sep. 10, 2018	Apr. 03, 2018	Mar. 26, 2018	Sep. 30, 2018	Feb. 06, 2018	Jan. 01, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill				$ 911,260		$ 909,811	$ 909,811
Fishing Hot Spots [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles				2,200
Goodwill				4,700
Business Combination, Consideration Transferred			$ 7,100
Other minority interest investments [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred				$ 15,500
Fishidy [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 7,100
Payments for Purchase of Other Assets		$ 7,100
Acyclica [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 10,300
Consumer and Small and Medium-Sized Security Business [Member] | Held-for-sale [Member]
Business Acquisition [Line Items]
Carrying amount of disposal group					$ 28,800