Summary of Changes in Accumulated Balances of AOCI Including Current Period Other Comprehensive Income and Reclassifications Out of AOCI (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	[1]	$ 2,766,275
Other comprehensive income (loss) before reclassifications		(2,633)	$ (16,157)
Less net gain (loss) reclassified from AOCI		5,768	7,621
Tax effect		(605)	(2,792)
Net current-period other comprehensive income (loss)		(7,796)	(20,986)
Ending Balance		2,769,087
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		13,006	13,602
Other comprehensive income (loss) before reclassifications		(4,199)	(8,481)
Less net gain (loss) reclassified from AOCI		2,516	7,621
Tax effect		0	0
Net current-period other comprehensive income (loss)		(6,715)	(16,102)
Ending Balance		6,291	(2,500)
Foreign Currency Items
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		(12)	(10)
Other comprehensive income (loss) before reclassifications		(1)	3
Less net gain (loss) reclassified from AOCI		0	0
Tax effect		0	0
Net current-period other comprehensive income (loss)		(1)	3
Ending Balance		(13)	(7)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		12,816	21,033
Less net gain (loss) reclassified from AOCI		0	0
Tax effect		0	0
Net current-period other comprehensive income (loss)		0	0
Ending Balance		5,020	47
Unrealized Gains (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		(178)	7,441
Other comprehensive income (loss) before reclassifications		1,567	(7,679)
Less net gain (loss) reclassified from AOCI		3,252	0
Tax effect		(605)	(2,792)
Net current-period other comprehensive income (loss)		(1,080)	(4,887)
Ending Balance		$ (1,258)	$ 2,554

[1] December 31, 2016 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, filed with the Securities and Exchange Commission (the SEC) on February 27, 2017.