Summary of Significant Accounting Policies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Summary of Significant Accounting Policies [Abstract]
Advertising expense	$ 5,300	$ 6,000	$ 7,700
Research and development expense	2,700	$ 2,200	$ 1,500
Right-of-use asset	12,803			$ 11,900
Accrued Rent				700
Lease liabilities	$ 13,601			$ 12,600