Income Taxes - Difference Between Provision for Domestic and Foreign Income Taxes and Amount Calculated by Statutory Tax Rate to Net Income Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Provision computed at statutory rate	$ 30,223	$ (9,055)	$ (34,984)
Change in statutory tax rates	13,438
Difference in foreign tax rates	(12,344)	1,995	24,359
Permanent differences
Derivative assets adjustment	1,937	(149)	(143)
TPECs, hybrid and other interest	(7,526)	(10,353)	(27,273)
Permanent impairment			(62,334)
Thin capitalization	1,888	2,120	2,457
Permanent foreign currency gain (loss)	(838)	(54)	11,575
Penalty	4,001	689
Non-deductible bad debt expense			89
Other permanent differences	633	50	(69)
Withholding tax	3,339	3,092	(14,457)
Foreign exchange rate adjustment	16,075	(1,838)	(8,954)
Change in valuation allowance	(56,744)	10,095	95,757
Tax credits claimed	(659)	(706)	(875)
Tax credits expired	2,638	1,578
Uncertain tax positions liability	(2,111)	351	(1,211)
Change in net operating loss carry-forwards	6,878
Others	327	5,929	976
Income tax expense (benefit)	$ 1,155	$ 3,744	$ (15,087)