Income Taxes - Changes in Valuation Allowance for Deferred Tax Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets Valuation Allowance [Roll Forward]
Balance at beginning of year	$ 100,705	$ 109,242	$ 226,813
Decrease in valuation allowance—future year utilization	(45,651)	0	0
Increase (decrease) in valuation allowance—current year utilization	(10,943)	(8,597)	4,875
Decrease in valuation allowance—change in federal income tax rate	0	0	(72,482)
Decrease in valuation allowance—adoption of ASU 2016-09	0	0	(50,203)
Increase (decrease) in valuation allowance—other	(287)	60	239
Balance at end of year	$ 43,824	$ 100,705	$ 109,242