Investment Securities - Available-For-Sale Investment (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale Securities
Amortized Cost	$ 1,781,135	$ 1,256,721
Unrealized Gains	3,079	1,566
Unrealized Losses	16,736	23,323
Available-for-sale, at fair value	1,767,478	1,234,964
U.S. Treasury securities
Available-for-sale Securities
Amortized Cost	5,795	5,788
Unrealized Gains	0	5
Unrealized Losses	2	0
Available-for-sale, at fair value	5,793	5,793
Government sponsored agencies
Available-for-sale Securities
Amortized Cost	248,021	216,890
Unrealized Gains	619	189
Unrealized Losses	1,166	2,068
Available-for-sale, at fair value	247,474	215,011
State and political subdivisions
Available-for-sale Securities
Amortized Cost	297,560	311,704
Unrealized Gains	114	163
Unrealized Losses	5,639	11,779
Available-for-sale, at fair value	292,035	300,088
Residential mortgage-backed securities
Available-for-sale Securities
Amortized Cost	296,898	276,162
Unrealized Gains	26	112
Unrealized Losses	4,012	3,992
Available-for-sale, at fair value	292,912	272,282
Collateralized mortgage obligations
Available-for-sale Securities
Amortized Cost	737,963	323,965
Unrealized Gains	173	63
Unrealized Losses	4,949	4,003
Available-for-sale, at fair value	733,187	320,025
Corporate bonds
Available-for-sale Securities
Amortized Cost	158,828	90,859
Unrealized Gains	276	16
Unrealized Losses	936	1,401
Available-for-sale, at fair value	158,168	89,474
Preferred stock and trust preferred securities
Available-for-sale Securities
Amortized Cost	36,070	31,353
Unrealized Gains	1,871	1,018
Unrealized Losses	32	80
Available-for-sale, at fair value	$ 37,909	$ 32,291

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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=82897076&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt 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 (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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
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-Section 50
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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
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-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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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
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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