Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			$ 6,467,445	$ 7,422,230
Other comprehensive income (loss) before reclassifications			1,423	(342)
Amounts reclassified from AOCL			1,156	2,348
Other comprehensive income, net	$ 793	$ 701	2,579	2,006
Ending Balance	5,964,857	7,757,983	5,964,857	7,757,983
Gains / (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			0	0
Other comprehensive income (loss) before reclassifications			674	(605)
Amounts reclassified from AOCL			0	0
Other comprehensive income, net			674	(605)
Ending Balance	674	(605)	674	(605)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(35,865)	(46,919)
Other comprehensive income (loss) before reclassifications			0	0
Amounts reclassified from AOCL			1,156	2,348
Other comprehensive income, net			1,156	2,348
Ending Balance	(34,709)	(44,571)	(34,709)	(44,571)
Foreign Currency Items [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(16,275)	(16,256)
Other comprehensive income (loss) before reclassifications			749	263
Amounts reclassified from AOCL			0	0
Other comprehensive income, net			749	263
Ending Balance	(15,526)	(15,993)	(15,526)	(15,993)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(52,140)	(63,175)
Other comprehensive income, net			2,579	2,006
Ending Balance	$ (49,561)	$ (61,169)	$ (49,561)	$ (61,169)