Shareholders' Equity - Changes in Accumulated Other Comprehensive Income (Loss) Balances (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2016	$ (83,837)
Reclassification to the income statement	(1,565)
Change in fair value	39,773
Balance as of December 31, 2017	(45,629)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2016	(84,133)
Change in fair value	41,691
Balance as of December 31, 2017	(42,442)
Cash Flow Hedging Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2016	296
Reclassification to the income statement	(1,565)
Change in fair value	1,235
Balance as of December 31, 2017	(34)
Retirement Benefit Plan Activity
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2016	0
Change in fair value	(3,153)
Balance as of December 31, 2017	$ (3,153)