Nature of Business and Summary of Significant Accounting Policies (Other Comprehensive Income) - Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$ 2,484	$ (1,384)	$ 3,874
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	(969)	540	(1,511)
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	1,515	(844)	2,363
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Before-Tax Amount	(4,989)	(10,145)	(6,780)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Tax (Expense) Benefit	1,946	3,957	2,644
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Net-of-Tax Amount	(3,043)	(6,188)	(4,136)
Defined benefit plan adjustments, Before-Tax Amount	(1,782)	2,303	(7,052)
Defined benefit plan adjustments, Tax (Expense) Benefit	553	(714)	2,186
Defined benefit plan adjustments, Net-of-Tax Amount	(1,229)	1,589	(4,866)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Before-Tax Amount	156	396
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Tax (Expense) Benefit	(49)	(123)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Net-of-Tax Amount	107	273
Foreign currency translation adjustment, Before-Tax Amount	(569)	(3,724)	(4,189)
Foreign currency translation adjustment, Net-of-Tax Amount	(569)	(3,724)	(4,189)
Total Other Comprehensive Income (Loss), Before-Tax Amount	(4,700)	(12,554)	(14,147)
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	1,481	3,660	3,319
Other Comprehensive Loss, net of tax	$ (3,219)	$ (8,894)	$ (10,828)