Securities (Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Total investment securities	$ 1,893,947	$ 1,584,703
Gross unrealized gains	9,547	15,849
Gross unrealized losses	(57,630)	(22,118)
Securities available for sale	1,845,864	1,578,434
Debt securities
Schedule of Available-for-sale Securities [Line Items]
Total investment securities	1,879,496	1,571,561
Gross unrealized gains	9,478	15,809
Gross unrealized losses	(57,630)	(22,074)
Securities available for sale	1,831,344	1,565,296
U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Total investment securities	4,716	25,847
Gross unrealized gains	16	22
Gross unrealized losses	(32)	(103)
Securities available for sale	4,700	25,766
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Total investment securities	1,321,760	1,254,452
Gross unrealized gains	7,026	9,134
Gross unrealized losses	(38,286)	(20,884)
Securities available for sale	1,290,500	1,242,702
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Total investment securities	553,020	290,522
Gross unrealized gains	2,436	6,547
Gross unrealized losses	(19,312)	(1,087)
Securities available for sale	536,144	295,982
Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Total investment securities	0	740
Gross unrealized gains	0	106
Gross unrealized losses	0	0
Securities available for sale	0	846
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Total investment securities	14,451	13,142
Gross unrealized gains	69	40
Gross unrealized losses	0	(44)
Securities available for sale	$ 14,520	$ 13,138

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
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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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
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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