Summary of Changes in Accumulated Balances of Other Comprehensive Loss Including Current Period Reclassifications Out of AOCI and Other Amount of Current Period Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 2,400,847	$ 1,527,894
Other comprehensive income (loss) before reclassifications	(2,429)	12,782
Less net gain (loss) reclassified from AOCI	10,158	21,477
Tax effect	4,370	2,262
Net current-period other comprehensive loss	(8,217)	(6,433)
Ending Balance	2,766,275	2,400,847
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	13,602	15,906
Other comprehensive income (loss) before reclassifications	9,677	17,300
Less net gain (loss) reclassified from AOCI	10,273	19,604
Tax effect	0	0
Net current-period other comprehensive loss	(596)	(2,304)
Ending Balance	13,006	13,602
Unrealized Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	7,441	11,511
Other comprehensive income (loss) before reclassifications	(12,104)	(4,459)
Less net gain (loss) reclassified from AOCI	(115)	1,873
Tax effect	4,370	2,262
Net current-period other comprehensive loss	(7,619)	(4,070)
Ending Balance	(178)	7,441
Foreign Currency Items
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(10)	49
Other comprehensive income (loss) before reclassifications	(2)	(59)
Less net gain (loss) reclassified from AOCI		0
Tax effect	0	0
Net current-period other comprehensive loss	(2)	(59)
Ending Balance	(12)	(10)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	21,033	27,466
Ending Balance	$ 12,816	$ 21,033