Comprehensive Income and Accumulated Other Comprehensive Income - Schedule of Changes in Accumulated Other Comprehensive Income (AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 409,762
Change in deferred tax valuation allowance	(198)
Ending Balance	430,405
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(832)	$ 3,612
Other comprehensive income (loss) before reclassification	5,981	(5,634)
Amounts reclassified from accumulated other comprehensive income	11	(214)
Change in deferred tax valuation allowance	(198)
Net current period other comprehensive income (loss)	5,794	(5,848)
Ending Balance	$ 4,962	$ (2,236)