Securities (Securities Available for Sale with Unrealized Losses) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	$ 1,077,963	$ 842,011
Available for sale, Losses less than 12 months, Gross Unrealized Losses	26,691	6,319
Available for sale, Losses 12 months or longer, Fair Value	1,773,312	1,569,320
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	106,039	39,099
Available for sale, Total, Fair Value	2,851,275	2,411,331
Available for sale, Total, Gross Unrealized Losses	132,730	45,418
U.S. Treasury and Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	41,765	45,616
Available for sale, Losses less than 12 months, Gross Unrealized Losses	2,027	42
Available for sale, Losses 12 months or longer, Fair Value	47,547	51,157
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	3,027	2,221
Available for sale, Total, Fair Value	89,312	96,773
Available for sale, Total, Gross Unrealized Losses	5,054	2,263
Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	53,337	2,768
Available for sale, Losses less than 12 months, Gross Unrealized Losses	1,568	11
Available for sale, Losses 12 months or longer, Fair Value	165,732	173,530
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	9,360	3,335
Available for sale, Total, Fair Value	219,069	176,298
Available for sale, Total, Gross Unrealized Losses	10,928	3,346
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	652,504	461,835
Available for sale, Losses less than 12 months, Gross Unrealized Losses	11,892	4,195
Available for sale, Losses 12 months or longer, Fair Value	1,029,004	898,099
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	52,500	16,192
Available for sale, Total, Fair Value	1,681,508	1,359,934
Available for sale, Total, Gross Unrealized Losses	64,392	20,387
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	247,504	203,618
Available for sale, Losses less than 12 months, Gross Unrealized Losses	8,368	995
Available for sale, Losses 12 months or longer, Fair Value	475,379	411,046
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	38,995	16,868
Available for sale, Total, Fair Value	722,883	614,664
Available for sale, Total, Gross Unrealized Losses	47,363	17,863
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	82,853	128,174
Available for sale, Losses less than 12 months, Gross Unrealized Losses	2,836	1,076
Available for sale, Losses 12 months or longer, Fair Value	55,650	35,488
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	2,157	483
Available for sale, Total, Fair Value	138,503	163,662
Available for sale, Total, Gross Unrealized Losses	$ 4,993	$ 1,559

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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-Publisher FASB
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