Loans Receivable (Recorded Investment in loans individually evaluated for impairment) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Allowance for loan and lease losses	$ 168,592	$ 167,509
Originated Loan [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	170,594	174,915
Recorded Investment	152,116	156,941
Allowance for loan and lease losses	$ 22,296	$ 19,694
Coverage	0.15%	0.13%
Acquired BBVAPR Accounted for under ASC 310-20 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 926	$ 926
Recorded Investment	747	747
Allowance for loan and lease losses	$ 21	$ 20
Coverage	0.03%	0.03%
Acquired BBVAPR Accounted under ASC 310-30 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 813,942	$ 843,423
Recorded Investment	791,243	818,303
Allowance for loan and lease losses	$ 43,166	$ 45,755
Coverage	0.05%	0.06%
Eurobank Acquired Loans
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 135,734	$ 139,246
Recorded Investment	121,750	123,335
Allowance for loan and lease losses	$ 25,410	$ 25,174
Coverage	0.21%	0.20%
Commercial impaired loans with specific allowance [Member] \| Originated Loan [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 57,169	$ 57,922
Recorded Investment	52,049	52,585
Allowance for loan and lease losses	$ 13,274	$ 10,573
Coverage	0.26%	0.20%
Commercial impaired loans with specific allowance [Member] \| Acquired BBVAPR Accounted for under ASC 310-20 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 926	$ 926
Recorded Investment	747	747
Allowance for loan and lease losses	$ 21	$ 20
Coverage	0.03%	0.03%
Residential troubled-debt restructuring impaired loans with specific allowance [Member] \| Originated Loan [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 94,405	$ 94,971
Recorded Investment	84,283	85,403
Allowance for loan and lease losses	$ 9,022	$ 9,121
Coverage	0.11%	0.11%
Commercial impaired loans with no specific allowance financing receivable \| Originated Loan [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 19,020	$ 22,022
Recorded Investment	$ 15,784	$ 18,953
Coverage	0.00%	0.00%
Commercial impaired loans with no specific allowance financing receivable \| Acquired BBVAPR Accounted for under ASC 310-20 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 0	$ 0
Recorded Investment	$ 0	$ 0
Coverage	0.00%	0.00%
Mortgage impaired loan pool [Member] \| Acquired BBVAPR Accounted under ASC 310-30 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 536,514	$ 547,064
Recorded Investment	526,089	532,052
Allowance for loan and lease losses	$ 14,331	$ 14,085
Coverage	0.03%	(0.03%)
Commercial impaired loan pool [Member] \| Acquired BBVAPR Accounted under ASC 310-30 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 239,976	$ 250,451
Recorded Investment	229,216	241,124
Allowance for loan and lease losses	$ 22,045	$ 23,691
Coverage	0.10%	0.10%
Auto impaired loan pool. \| Acquired BBVAPR Accounted under ASC 310-30 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 35,560	$ 43,440
Recorded Investment	35,006	43,696
Allowance for loan and lease losses	$ 6,769	$ 7,961
Coverage	0.19%	0.18%
Consumer impaired loan pool. \| Acquired BBVAPR Accounted under ASC 310-30 [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 1,892	$ 2,468
Recorded Investment	932	1,431
Allowance for loan and lease losses	$ 21	$ 18
Coverage	0.02%	0.01%
Consumer impaired loan pool. \| Eurobank Acquired Loans
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 14	$ 15
Recorded Investment	4	4
Allowance for loan and lease losses	$ 4	$ 5
Coverage	1.00%	1.25%
Loans secured by 1-4 family residential properties, covered [Member] \| Eurobank Acquired Loans
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 79,633	$ 81,132
Recorded Investment	69,328	69,538
Allowance for loan and lease losses	$ 15,414	$ 15,187
Coverage	0.22%	0.22%
Commercial and Other Construction Loan [Member] \| Eurobank Acquired Loans
Financing Receivable, Impaired [Line Items]
Unpaid Principal	$ 56,087	$ 58,099
Recorded Investment	52,418	53,793
Allowance for loan and lease losses	$ 9,992	$ 9,982
Coverage	0.19%	0.19%

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953550-111524

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- Definition

Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
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