Investment Securities - Amortized cost and fair value for available for sale securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Investment securities available for sale
Amortized cost	$ 1,700,681	$ 1,540,650	$ 1,614,571
Gross Unrealized Gains	19,530	2,427	2,042
Gross Unrealized Losses	(2,935)	(26,010)	(38,614)
Fair Value	1,717,276	1,517,067	1,577,999
Government-sponsored entities debt
Investment securities available for sale
Amortized cost	65,604	48,982	48,933
Gross Unrealized Gains	933	21
Gross Unrealized Losses	(8)	(752)	(1,320)
Fair Value	66,529	48,251	47,613
State and municipal obligations
Investment securities available for sale
Amortized cost	177,533	200,184	223,533
Gross Unrealized Gains	4,614	1,709	1,932
Gross Unrealized Losses	(1)	(1,125)	(1,649)
Fair Value	182,146	200,768	223,816
Mortgage-backed securities
Investment securities available for sale
Amortized cost	1,457,544	1,291,484	1,342,105
Gross Unrealized Gains	13,983	697	110
Gross Unrealized Losses	(2,926)	(24,133)	(35,645)
Fair Value	1,468,601	1,268,048	1,306,570
Mortgage-backed securities issued by private label holdings
Investment securities available for sale
Fair Value	$ 0	$ 0	$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Section 50
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
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-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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