Nature of Business and Summary of Significant Accounting Policies (Other Comprehensive Income) - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (8,969)	$ (75)	$ 10,753
Other comprehensive income (loss) before reclassifications	(283)	(2,979)	(6,692)
Amounts reclassified from accumulated other comprehensive income	(2,936)	(5,915)	(4,136)
Ending balance	(12,188)	(8,969)	(75)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,932	8,964	10,737
Other comprehensive income (loss) before reclassifications	1,515	(844)	2,363
Amounts reclassified from accumulated other comprehensive income	(3,043)	(6,188)	(4,136)
Ending balance	404	1,932	8,964
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(3,895)	(5,757)	(891)
Other comprehensive income (loss) before reclassifications	(1,229)	1,589	(4,866)
Amounts reclassified from accumulated other comprehensive income	107	273
Ending balance	(5,017)	(3,895)	(5,757)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(7,006)	(3,282)	907
Other comprehensive income (loss) before reclassifications	(569)	(3,724)	(4,189)
Ending balance	$ (7,575)	$ (7,006)	$ (3,282)