Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Derivative instruments	$ 29,304	$ 68,900
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Derivative liabilities	10,280	79,925
Fair value, measurements, recurring
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	451,258	1,139,554
Derivative instruments	29,304	68,900
Total financial assets	1,032,698	2,315,197
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Derivative liabilities	10,280	79,925
Fair value, measurements, recurring | Money market and deposit accounts
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	533,496	1,089,284
Fair value, measurements, recurring | Publicly traded equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	8,254	3,353
Fair value, measurements, recurring | Certificates of deposit
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	10,386	14,106
Fair value, measurements, recurring | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	451,258	1,139,554
Derivative instruments	0	0
Total financial assets	993,008	2,232,191
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Derivative liabilities	0	0
Fair value, measurements, recurring | Level 1 | Money market and deposit accounts
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	533,496	1,089,284
Fair value, measurements, recurring | Level 1 | Publicly traded equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	8,254	3,353
Fair value, measurements, recurring | Level 1 | Certificates of deposit
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	0	0
Fair value, measurements, recurring | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	0	0
Derivative instruments	29,304	68,900
Total financial assets	39,690	83,006
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Derivative liabilities	10,280	79,925
Fair value, measurements, recurring | Level 2 | Money market and deposit accounts
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	0	0
Fair value, measurements, recurring | Level 2 | Publicly traded equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	0	0
Fair value, measurements, recurring | Level 2 | Certificates of deposit
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Financial assets	$ 10,386	$ 14,106