Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 0	$ 37,390	$ 0	$ 120,800
Securities available-for-sale, amortized cost	2,215,335		2,215,335		$ 2,299,037
Available-for-sale Debt Securities Gross Unrealized Gain, instant	13,644		13,644		10,231
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(21,106)		(21,106)		(30,691)
Securities available for sale	2,207,873		2,207,873		2,278,577
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	1,391,636		1,391,636		1,486,690
Available-for-sale Debt Securities Gross Unrealized Gain, instant	3,143		3,143		2,760
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(17,362)		(17,362)		(23,718)
Securities available for sale	1,377,417		1,377,417		1,465,732
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	476,702		476,702		473,914
Available-for-sale Debt Securities Gross Unrealized Gain, instant	9,047		9,047		6,343
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(2,261)		(2,261)		(5,197)
Securities available for sale	483,488		483,488		475,060
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	341,462		341,462		332,348
Available-for-sale Debt Securities Gross Unrealized Gain, instant	1,372		1,372		1,065
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,230)		(1,230)		(1,511)
Securities available for sale	341,604		341,604		331,902
US Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	251		251		801
Available-for-sale Debt Securities Gross Unrealized Gain, instant	0		0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1)		(1)		(1)
Securities available for sale	250		250		800
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	5,284		5,284		5,284
Available-for-sale Debt Securities Gross Unrealized Gain, instant	82		82		63
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(252)		(252)		(264)
Securities available for sale	$ 5,114		$ 5,114		$ 5,083

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
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-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
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-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
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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The total amount of proceeds received for the sale of securities, categorized neither as held-to-maturity nor trading securities, during the reporting period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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