Comprehensive Income - Components of Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Unrealized holding (losses) gains on available-for-sale securities, Gross amount	$ 1,787	$ (1,597)	$ 620
Unrealized holding gains (losses) on available-for-sale securities, Income tax (expense) benefit	(645)	582	(208)
Unrealized holding (losses) gains on available-for-sale investments, Net of tax amount	1,142	(1,015)	412
Realized (gains) on sales of available-for-sale securities	(412)	(347)
Realized (gains) on available-for-sale securities reclassified into income, Other-than-temporary impairment losses		230
Realized (gains) on available-for-sale securities reclassified into income, Total before tax	(412)	(117)
Realized (gains) on available-for-sale securities reclassified into income, Income tax expense	148	45
Realized (gains) on available-for-sale securities reclassified into income, Net of tax amount	(264)	(72)
Unrealized holding gains on interest rate swaps, Gross amount	161
Unrealized holding gains on interest rate swaps, Income tax expense	(62)
Unrealized holding gains on interest rate swaps, Net of tax amount	99
Foreign currency translation adjustments	$ (1,161)	$ (2,252)	$ (1,631)