Securities (Amortized Cost and Fair Value of Securities Available for Sale) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	$ 2,698,865	$ 2,755,806
Securities Available for Sale, Gross Unrealized Gains	17,603	7,500
Securities Available for Sale, Gross Unrealized Losses	35,388	72,269
Securities Available for Sale, Fair Value	2,681,080	2,691,037
U.S. Treasury And Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	73,426	74,339
Securities Available for Sale, Gross Unrealized Losses	1,283	2,633
Securities Available for Sale, Fair Value	72,143	71,706
Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	245,707	246,713
Securities Available for Sale, Gross Unrealized Gains	1,833	360
Securities Available for Sale, Gross Unrealized Losses	1,600	6,646
Securities Available for Sale, Fair Value	245,940	240,427
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	1,418,881	1,468,912
Securities Available for Sale, Gross Unrealized Gains	9,964	4,284
Securities Available for Sale, Gross Unrealized Losses	15,813	29,794
Securities Available for Sale, Fair Value	1,413,032	1,443,402
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	798,447	799,060
Securities Available for Sale, Gross Unrealized Gains	4,594	1,953
Securities Available for Sale, Gross Unrealized Losses	15,207	30,936
Securities Available for Sale, Fair Value	787,834	770,077
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	158,904	163,282
Securities Available for Sale, Gross Unrealized Gains	1,212	903
Securities Available for Sale, Gross Unrealized Losses	1,485	2,260
Securities Available for Sale, Fair Value	158,631	161,925
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	3,500	3,500
Securities Available for Sale, Fair Value	$ 3,500	$ 3,500

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
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