Business Segment, Geographic and Quarterly Financial Data - Operations by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Revenues	$ 9,568	$ 12,596	$ 15,175	$ 17,822	$ 18,201	$ 21,677	$ 18,683	$ 15,103	$ 55,161	$ 73,664	$ 79,017
Assets
Assets:	57,788				76,011				57,788	76,011
United States
Revenues:
Revenues									42,545	51,485	50,901
Assets
Assets:	37,684				47,437				37,684	47,437
Foreign
Revenues:
Revenues									12,616	22,179	$ 28,116
Assets
Assets:	$ 20,104				$ 28,574				$ 20,104	$ 28,574