Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Publicly traded equity securities	$ 2,231	$ 1,717
Derivative assets	77,353	73,074
Total financial assets	1,725,030	683,780
Liabilities:
Derivative liabilities	3,064	9,740
Cash [Member]
Assets:
Cash and cash equivalents	830,918	486,648
Money market and deposit accounts [Member]
Assets:
Cash and cash equivalents	602,927	119,518
Certificates of deposit [Member]
Assets:
Cash and cash equivalents	211,601	2,823
Fair value, inputs, Level 1 [Member]
Assets:
Publicly traded equity securities	2,231	1,717
Derivative assets	0	0
Total financial assets	1,436,076	607,883
Liabilities:
Derivative liabilities	0	0
Fair value, inputs, Level 1 [Member] | Cash [Member]
Assets:
Cash and cash equivalents	830,918	486,648
Fair value, inputs, Level 1 [Member] | Money market and deposit accounts [Member]
Assets:
Cash and cash equivalents	602,927	119,518
Fair value, inputs, Level 1 [Member] | Certificates of deposit [Member]
Assets:
Cash and cash equivalents	0	0
Fair value, inputs, Level 2 [Member]
Assets:
Publicly traded equity securities	0	0
Derivative assets	77,353	73,074
Total financial assets	288,954	75,897
Liabilities:
Derivative liabilities	3,064	9,740
Fair value, inputs, Level 2 [Member] | Cash [Member]
Assets:
Cash and cash equivalents	0	0
Fair value, inputs, Level 2 [Member] | Money market and deposit accounts [Member]
Assets:
Cash and cash equivalents	0	0
Fair value, inputs, Level 2 [Member] | Certificates of deposit [Member]
Assets:
Cash and cash equivalents	$ 211,601	$ 2,823