Schedule of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 494,644	$ 716,161	$ 951,437
Changes before reclassifications	19,148	(9,535)
Current period other comprehensive income	19,148	(9,535)	(36,707)
Ending Balance	(50,976)	494,644	716,161
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(67,735)	(60,190)
Changes before reclassifications	19,632	(7,545)
Current period other comprehensive income	19,632	(7,545)
Ending Balance	(48,103)	(67,735)	(60,190)
Unrealized Losses of Available for Sale Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(2,693)	(703)
Changes before reclassifications	(484)	(1,990)
Current period other comprehensive income	(484)	(1,990)
Ending Balance	(3,177)	(2,693)	(703)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(70,428)	(60,893)	(24,186)
Ending Balance	$ (51,280)	$ (70,428)	$ (60,893)