Investment Securities (Gains and losses by category) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month	$ 148,896	$ 335,079
Available for sale - Amortized cost - more than 12 month	220,334	38,563
Total Available for Sale Amortization cost	369,230	373,642
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Available for sale - Unrealized Loss - less than 12 month	942	5,723
Available for sale - Unrealized Loss - more than 12 month	5,001	1,400
Total Available for Sale Unrealized Loss	5,943	7,123
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month	147,954	329,356
Available-for-sale, Fair Value - more than 12 month	215,333	37,163
Total Available for Sale Fair Value	363,287	366,519
Continuous Unrealized Loss Position Amortized Cost [Abstract]
Held to Maturity - Amortized cost - less than 12 month	153,665	525,258
Held to Maturity - Amortized cost - more than 12 month	352,399
Held to Maturity - Amortized Cost	506,064	525,258
Held To Maturity Securities, Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Held to Maturity- Unrealized Loss - less than 12 month	1,119	7,266
Held to Maturity- Unrealized Loss - more than 12 month	7,264
Held to Maturity- Unrealized Loss	8,383	7,266
Held To Maturity Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Held-to-Maturity - Fair Value - less than 12 Month	152,546	517,992
Held-to-Maturity - Fair Value - more than 12 Month	345,135
Held to Maturity - Fair Value	497,681	517,992
Investment Securities Continuous Unrealized Loss Position [Abstract]
Investment Securities - Amortized Cost	875,294	898,900
Investment Securities - Unrealized Loss	14,326	14,389
Investment Securities - Fair Value	860,968	884,511
CMO's issued by us government sponsored agencies at loss
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month	9,464	67,777
Available for sale - Amortized cost - more than 12 month	72,562	33,883
Total Available for Sale Amortization cost	82,026	101,660
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Available for sale - Unrealized Loss - less than 12 month	98	1,430
Available for sale - Unrealized Loss - more than 12 month	1,857	793
Total Available for Sale Unrealized Loss	1,955	2,223
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month	9,366	66,347
Available-for-sale, Fair Value - more than 12 month	70,705	33,090
Total Available for Sale Fair Value	80,071	99,437
Obligation of Puerto Rico Government and public instrumentalities at loss
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - more than 12 month	2,455	4,680
Total Available for Sale Amortization cost	2,455	4,680
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Available for sale - Unrealized Loss - more than 12 month	362	607
Total Available for Sale Unrealized Loss	362	607
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available-for-sale, Fair Value - more than 12 month	2,093	4,073
Total Available for Sale Fair Value	2,093	4,073
FNMA and FHLMC [Member]
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month	125,107	184,782
Available for sale - Amortized cost - more than 12 month	111,635
Total Available for Sale Amortization cost	236,742	184,782
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Available for sale - Unrealized Loss - less than 12 month	759	3,036
Available for sale - Unrealized Loss - more than 12 month	2,122
Total Available for Sale Unrealized Loss	2,881	3,036
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month	124,348	181,746
Available-for-sale, Fair Value - more than 12 month	109,513
Total Available for Sale Fair Value	233,861	181,746
Continuous Unrealized Loss Position Amortized Cost [Abstract]
Held to Maturity - Amortized cost - less than 12 month	153,665	525,258
Held to Maturity - Amortized cost - more than 12 month	352,399
Held to Maturity - Amortized Cost	506,064	525,258
Held To Maturity Securities, Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Held to Maturity- Unrealized Loss - less than 12 month	1,119	7,266
Held to Maturity- Unrealized Loss - more than 12 month	7,264
Held to Maturity- Unrealized Loss	8,383	7,266
Held To Maturity Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Held-to-Maturity - Fair Value - less than 12 Month	152,546	517,992
Held-to-Maturity - Fair Value - more than 12 Month	345,135
Held to Maturity - Fair Value	497,681	517,992
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month	14,001	29,445
Available for sale - Amortized cost - more than 12 month	20,803
Total Available for Sale Amortization cost	34,804	29,445
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Available for sale - Unrealized Loss - less than 12 month	85	620
Available for sale - Unrealized Loss - more than 12 month	499
Total Available for Sale Unrealized Loss	584	620
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month	13,916	28,825
Available-for-sale, Fair Value - more than 12 month	20,304
Total Available for Sale Fair Value	34,220	28,825
Obligation of US Government sponsored agencies at loss [Member]
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month		3,903
Available for sale - Amortized cost - more than 12 month	2,927
Total Available for Sale Amortization cost	2,927	3,903
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Available for sale - Unrealized Loss - less than 12 month		19
Available for sale - Unrealized Loss - more than 12 month	48
Total Available for Sale Unrealized Loss	48	19
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month		3,884
Available-for-sale, Fair Value - more than 12 month	2,879
Total Available for Sale Fair Value	2,879	3,884
US Treasury Securities at loss
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month	324	49,172
Available for sale - Amortized cost - more than 12 month	9,952
Total Available for Sale Amortization cost	10,276	49,172
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Available for sale - Unrealized Loss - less than 12 month	0	618
Available for sale - Unrealized Loss - more than 12 month	113
Total Available for Sale Unrealized Loss	113	618
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month	324	48,554
Available-for-sale, Fair Value - more than 12 month	9,839
Total Available for Sale Fair Value	$ 10,163	$ 48,554

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