Securities (Securities Held to Maturity with Unrealized Losses) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Losses less than 12 months, Fair Value	$ 1,513,235	$ 934,207
Held to maturity, Losses less than 12 months, Gross Unrealized Losses	34,152	5,194
Held to maturity, Losses 12 months or longer, Fair Value	127,125	419,483
Held to maturity, Losses 12 months or longer, Gross Unrealized Losses	3,847	10,647
Held to maturity, Total, Fair Value	1,640,360	1,353,690
Held to maturity, Total, Gross Unrealized Losses	37,999	15,841
U.S. Treasury And Government Agency Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Losses less than 12 months, Fair Value	49,956	45,590
Held to maturity, Losses less than 12 months, Gross Unrealized Losses	44	410
Held to maturity, Total, Fair Value	49,956	45,590
Held to maturity, Total, Gross Unrealized Losses	44	410
Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Losses less than 12 months, Fair Value	494,470	22,652
Held to maturity, Losses less than 12 months, Gross Unrealized Losses	19,706	301
Held to maturity, Losses 12 months or longer, Fair Value	11,750	48,727
Held to maturity, Losses 12 months or longer, Gross Unrealized Losses	469	865
Held to maturity, Total, Fair Value	506,220	71,379
Held to maturity, Total, Gross Unrealized Losses	20,175	1,166
Residential Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Losses less than 12 months, Fair Value	278,369	349,635
Held to maturity, Losses less than 12 months, Gross Unrealized Losses	3,068	1,589
Held to maturity, Total, Fair Value	278,369	349,635
Held to maturity, Total, Gross Unrealized Losses	3,068	1,589
Commercial Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Losses less than 12 months, Fair Value	71,701
Held to maturity, Losses less than 12 months, Gross Unrealized Losses	4,038
Held to maturity, Total, Fair Value	71,701
Held to maturity, Total, Gross Unrealized Losses	4,038
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Losses less than 12 months, Fair Value	618,739	516,330
Held to maturity, Losses less than 12 months, Gross Unrealized Losses	7,296	2,894
Held to maturity, Losses 12 months or longer, Fair Value	115,375	370,756
Held to maturity, Losses 12 months or longer, Gross Unrealized Losses	3,378	9,782
Held to maturity, Total, Fair Value	734,114	887,086
Held to maturity, Total, Gross Unrealized Losses	$ 10,674	$ 12,676

Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity 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 7
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27337-111563

Reference 2: 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=73527792&loc=d3e27290-111563

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity in a continuous loss position.

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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)(1)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

Reference 2: 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=73527792&loc=d3e27337-111563

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This item represents the fair value of securities categorized as held-to-maturity securities that have been in a continuous unrealized loss position for twelve months or longer.

+ 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=73527792&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
-Paragraph 6
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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

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