Changes in Accumulated Other Comprehensive Income (loss) by Component Net of Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 3,226,737	$ 1,840,961	$ 1,690,761
Net current-period other comprehensive income (loss)	1,210	15,950	(1,624)
Balance	3,184,034	3,226,737	1,840,961
Available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	137	133
Other comprehensive (loss) income before reclassifications	471	(11)
Amounts reclassified from accumulated other comprehensive income (loss)	54	15
Net current-period other comprehensive income (loss)	525	4
Balance	662	137	133
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	671	(6,781)
Other comprehensive (loss) income before reclassifications	3,790	1,631
Amounts reclassified from accumulated other comprehensive income (loss)	1,128	5,821
Net current-period other comprehensive income (loss)	4,918	7,452
Balance	5,589	671	(6,781)
Pension obligations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(6,810)	(4,195)
Other comprehensive (loss) income before reclassifications	(2,487)	(2,934)
Amounts reclassified from accumulated other comprehensive income (loss)	304	319
Net current-period other comprehensive income (loss)	(2,183)	(2,615)
Balance	(8,993)	(6,810)	(4,195)
Cumulative Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	9,293	(1,803)
Other comprehensive (loss) income before reclassifications	(2,050)	11,096
Net current-period other comprehensive income (loss)	(2,050)	11,096
Balance	7,243	9,293	(1,803)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	3,291	(12,646)
Other comprehensive (loss) income before reclassifications	(276)	9,782
Amounts reclassified from accumulated other comprehensive income (loss)	1,486	6,155
Net current-period other comprehensive income (loss)	1,210	15,937
Balance	$ 4,501	$ 3,291	$ (12,646)