FAIR VALUE MEASUREMENTS (Details) (Measured on a Recurring Basis:, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Liabilities at fair value	$ 0
Transfers of assets
Amounts transferred from Level 1 to Level 2	0
Amounts transferred from Level 2 to Level 1	0
Amounts transferred in Level 3	0
Amounts transferred out of Level 3	0
Total
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	1,477,473
Total | Government agency and government-sponsored enterprises residential mortgage-backed securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	844,306
Total | Covered private label CMOs
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	37,594
Total | Municipal securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	447,933
Total | Corporate securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	84,211
Total | Government-sponsored enterprises debt securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	36,054
Total | Other securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	27,375
Level 1
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	509
Level 1 | Other securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	509
Level 2
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	1,439,370
Level 2 | Government agency and government-sponsored enterprises residential mortgage-backed securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	844,306
Level 2 | Municipal securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	447,933
Level 2 | Corporate securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	84,211
Level 2 | Government-sponsored enterprises debt securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	36,054
Level 2 | Other securities
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	26,866
Level 3
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	37,594
Level 3 | Covered private label CMOs
Assets measured and recorded at fair value on a recurring and nonrecurring basis
Assets at fair value	$ 37,594