Customer Concentration (Total Revenues by Geographic Area) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Revenues	$ (5,795)	$ 44,165	$ (22,526)	$ 38,913	$ 45,119	$ 67,898	$ 46,575	$ 38,518	$ 54,757	$ 198,110	$ 320,060
UNITED STATES
Concentration Risk [Line Items]
Revenues									10,143	148,622	291,448
Europe [Member]
Concentration Risk [Line Items]
Revenues									26,254	27,709	16,144
Other geographic location [Member]
Concentration Risk [Line Items]
Revenues									$ 18,360	$ 21,779	$ 12,468