Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance			$ 2,897,438
Total other comprehensive income (loss)	$ 419	$ 1,343	(61)	$ 3,046
Ending Balance	1,974,991		1,974,991
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance			(2,100)
Other comprehensive loss before reclassifications			(10)
Change in cash flow hedges reclassed to earnings			351
Total other comprehensive income (loss)			341
Ending Balance	(1,759)		(1,759)
Foreign Currency Items [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance			994
Other comprehensive loss before reclassifications			(328)
Change in cash flow hedges reclassed to earnings			0
Total other comprehensive income (loss)			(328)
Ending Balance	666		666
Total [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance			(1,106)
Other comprehensive loss before reclassifications			(338)
Change in cash flow hedges reclassed to earnings			351
Total other comprehensive income (loss)			13
Ending Balance	$ (1,093)		$ (1,093)