Investment Securities - Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available for sale:
Total	$ 892,063	$ 786,783
Unrealized Gain	1,853	6,161
Unrealized Loss	(19,216)	(5,515)
Estimated Fair Value	874,700	787,429
Held to maturity:
Amortized Cost	31,965	18,291
Unrealized Gain	0	0
Unrealized Loss	(838)	(209)
Estimated Fair Value	31,127	18,082
Total investment securities
Amortized Cost	924,028	805,074
Unrealized Gain	1,853	6,161
Unrealized Loss	(20,054)	(5,724)
Estimated Fair Value	905,827	805,511
Agency
Available for sale:
Total	41,567	47,051
Unrealized Gain	0	236
Unrealized Loss	(490)	(78)
Estimated Fair Value	41,077	47,209
Corporate
Available for sale:
Total	93,126	78,155
Unrealized Gain	433	1,585
Unrealized Loss	(1,057)	(194)
Estimated Fair Value	92,502	79,546
Municipal bonds
Available for sale:
Total	221,806	228,929
Unrealized Gain	1,281	3,942
Unrealized Loss	(3,186)	(743)
Estimated Fair Value	219,901	232,128
Collateralized mortgage obligation: residential
Available for sale:
Total	29,747	33,984
Unrealized Gain	81	132
Unrealized Loss	(670)	(335)
Estimated Fair Value	29,158	33,781
Mortgage-backed securities: residential
Available for sale:
Total	505,817	398,664
Unrealized Gain	58	266
Unrealized Loss	(13,813)	(4,165)
Estimated Fair Value	492,062	394,765
Held to maturity:
Amortized Cost	30,854	17,153
Unrealized Gain	0	0
Unrealized Loss	(838)	(209)
Estimated Fair Value	30,016	16,944
Other
Held to maturity:
Amortized Cost	1,111	1,138
Unrealized Gain	0	0
Unrealized Loss	0	0
Estimated Fair Value	$ 1,111	$ 1,138

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Available-for-sale Securities And Held-To-Maturity Securities, Accumulated Gross Unrealized Gain, before Tax

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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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