Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 0	$ 38,900
Securities available-for-sale, amortized cost	2,349,149		$ 2,299,037
Available-for-sale Debt Securities Gross Unrealized Gain, instant	11,017		10,231
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(28,807)		(30,691)
Securities available for sale	2,331,359		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	1,506,914		1,486,690
Available-for-sale Debt Securities Gross Unrealized Gain, instant	2,400		2,760
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(22,816)		(23,718)
Securities available for sale	1,486,498		1,465,732
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	484,376		473,914
Available-for-sale Debt Securities Gross Unrealized Gain, instant	7,316		6,343
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(4,337)		(5,197)
Securities available for sale	487,355		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	352,323		332,348
Available-for-sale Debt Securities Gross Unrealized Gain, instant	1,241		1,065
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,381)		(1,511)
Securities available for sale	352,183		331,902
US Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	252		801
Available-for-sale Debt Securities Gross Unrealized Gain, instant	0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0		(1)
Securities available for sale	252		800
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, amortized cost	5,284		5,284
Available-for-sale Debt Securities Gross Unrealized Gain, instant	60		63
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(273)		(264)
Securities available for sale	$ 5,071		$ 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=65884222&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=73527792&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=66010992&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
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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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
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-Topic 320
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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
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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.

+ References

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