Organization and Significant Accounting Policies - Activity in Deferred Revenue Reserve (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Movement in Deferred Revenue [Roll Forward]
Balance at beginning of year	$ 26,157	$ 0
Additions to deferred revenue through acquisitions	0	7,944
New contracts sold	31,617	20,569
Less: reductions for revenue recognized	(12,014)	(2,356)
Balance at end of year	45,760	26,157
Deferred revenue, current	18,607	11,012
Deferred revenue, noncurrent	$ 27,153	$ 15,145