Summary of Reconciliation of Unrecognized Tax Position (Detail)	9 Months Ended
	Sep. 30, 2018 USD ($)
Gross Position
Balance as of January 1, 2018	$ 14,140,000
Reduction for settlements	(14,140,000)
Balance as of September 30, 2018	0
Tax Effect
Balance as of January 1, 2018	3,521,000
Reduction for settlements	(3,521,000)
Balance as of September 30, 2018	$ 0