SEGMENT INFORMATIO - Information about reportable segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Interest income	$ 143,573	$ 149,812	$ 441,338	$ 453,929
Net (charge) credit for transfer of funds	0	0	0	0
Interest expense	(25,395)	(24,883)	(78,284)	(76,876)
Net interest income	118,178	124,929	363,054	377,053
(Provision) release for loan and lease losses	(21,503)	(31,176)	(63,542)	(138,412)
Non-interest income (loss)	26,146	18,758	64,393	44,714
Direct non-interest expenses	(63,402)	(68,000)	(197,529)	(202,645)
Segment (loss) income	59,419	44,511	166,376	80,710
Average earnings assets	11,354,259	11,587,431	11,631,135	11,831,006
Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Interest income	34,605	36,180	104,865	106,352
Net (charge) credit for transfer of funds	(12,074)	(12,629)	(37,673)	(36,212)
Interest expense	0	0	0	0
Net interest income	22,531	23,551	67,192	70,140
(Provision) release for loan and lease losses	(3,860)	(6,750)	(21,608)	(21,657)
Non-interest income (loss)	5,222	3,982	14,381	11,866
Direct non-interest expenses	(8,864)	(8,977)	(29,828)	(26,270)
Segment (loss) income	15,029	11,806	30,137	34,079
Average earnings assets	2,549,358	2,642,388	2,576,194	2,601,892
Consumer Retail Banking [Member]
Segment Reporting Information [Line Items]
Interest income	44,455	48,528	135,655	147,395
Net (charge) credit for transfer of funds	2,810	4,335	10,546	12,816
Interest expense	(6,323)	(5,869)	(18,765)	(17,379)
Net interest income	40,942	46,994	127,436	142,832
(Provision) release for loan and lease losses	(8,655)	(13,946)	(24,451)	(36,588)
Non-interest income (loss)	11,292	11,759	35,318	35,504
Direct non-interest expenses	(27,100)	(32,669)	(87,218)	(96,690)
Segment (loss) income	16,479	12,138	51,085	45,058
Average earnings assets	1,973,424	1,959,951	1,989,426	1,956,352
Commercial And Corporate [Member]
Segment Reporting Information [Line Items]
Interest income	28,981	32,636	93,915	100,192
Net (charge) credit for transfer of funds	(6,700)	(4,058)	(18,212)	(11,746)
Interest expense	0	0	0	0
Net interest income	22,281	28,578	75,703	88,446
(Provision) release for loan and lease losses	(8,162)	(11,355)	(17,730)	(84,170)
Non-interest income (loss)	985	647	2,459	2,350
Direct non-interest expenses	(11,871)	(10,896)	(33,194)	(30,013)
Segment (loss) income	3,233	6,974	27,238	(23,387)
Average earnings assets	2,410,037	2,760,788	2,489,268	2,947,562
Treasury And Investments [Member]
Segment Reporting Information [Line Items]
Interest income	12,529	11,500	39,206	36,276
Net (charge) credit for transfer of funds	15,839	8,563	44,226	23,936
Interest expense	(14,487)	(14,305)	(45,828)	(44,834)
Net interest income	13,881	5,758	37,604	15,378
(Provision) release for loan and lease losses	0	0	0	0
Non-interest income (loss)	6,154	(174)	3,815	(13,046)
Direct non-interest expenses	(914)	(1,103)	(3,462)	(3,487)
Segment (loss) income	19,121	4,481	37,957	(1,155)
Average earnings assets	2,565,019	2,531,084	2,774,118	2,683,313
United States Operations [Member]
Segment Reporting Information [Line Items]
Interest income	13,944	11,229	40,091	34,477
Net (charge) credit for transfer of funds	125	3,789	1,113	11,206
Interest expense	(3,811)	(3,931)	(11,214)	(12,326)
Net interest income	10,258	11,087	29,990	33,357
(Provision) release for loan and lease losses	2,024	1,307	1,563	6,715
Non-interest income (loss)	884	778	2,799	2,032
Direct non-interest expenses	(7,556)	(6,914)	(23,070)	(21,293)
Segment (loss) income	5,610	6,258	11,282	20,811
Average earnings assets	1,252,271	1,048,451	1,188,463	1,001,860
Virgin Islands Operations [Member]
Segment Reporting Information [Line Items]
Interest income	9,059	9,739	27,606	29,237
Net (charge) credit for transfer of funds	0	0	0	0
Interest expense	(774)	(778)	(2,477)	(2,337)
Net interest income	8,285	8,961	25,129	26,900
(Provision) release for loan and lease losses	(2,850)	(432)	(1,316)	(2,712)
Non-interest income (loss)	1,609	1,766	5,621	6,008
Direct non-interest expenses	(7,097)	(7,441)	(20,757)	(24,892)
Segment (loss) income	(53)	2,854	8,677	5,304
Average earnings assets	$ 604,150	$ 644,769	$ 613,666	$ 640,027