Commitments and Contingencies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 03, 2017	Jul. 01, 2016	Jun. 29, 2016
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Obligation	$ 1,300
Operating Leases, Rent Expense	800	$ 300	$ 200
Guarantor Obligations, Maximum Exposure, Undiscounted	45,100
Accrued lease liability	10,700	10,700
Other Investments						$ 75,000
Guarantees, Fair Value Disclosure					$ 14,000
Anniversary payment	0	$ 88,001		$ 89,000	$ 87,000
Other Long-term Investments	75,000			$ 75,000
Next twelve months [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Obligation	74,200
Next twenty-four months [Member] [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Obligation	$ 105,800