Securities - Amortized Cost and Fair Value of Securities Available for Sale and Held for Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	$ 998,241	$ 953,720
Gross Unrealized Gains, Available for Sale	2,619	4,202
Gross Unrealized Losses, Available for Sale	(17,902)	(8,462)
Fair Value, Available for Sale	982,958	949,460
Gross Amortized Cost, Held for Investment Securities	400,647	416,863
Gross Unrealized Gains, Held for Investment Securities	632	1,819
Gross Unrealized Losses, Held for Investment Securities	(9,412)	(4,212)
Fair Value, Held for Investment Securities	391,867	414,470
U.S. Treasury Securities and obligations of U.S. Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	8,697	9,475
Gross Unrealized Gains, Available for Sale	214	274
Gross Unrealized Losses, Available for Sale	(14)	(5)
Fair Value, Available for Sale	8,897	9,744
Mortgage-backed securities of U.S. Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	328,521	318,771
Gross Unrealized Gains, Available for Sale	225	891
Gross Unrealized Losses, Available for Sale	(8,861)	(3,306)
Fair Value, Available for Sale	319,885	316,356
Gross Amortized Cost, Held for Investment Securities	168,462	172,261
Gross Unrealized Gains, Held for Investment Securities	0	746
Gross Unrealized Losses, Held for Investment Securities	(3,524)	(1,392)
Fair Value, Held for Investment Securities	164,938	171,615
Collateralized Mortgage Obligations Of US Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	281,335	235,466
Gross Unrealized Gains, Available for Sale	70	272
Gross Unrealized Losses, Available for Sale	(8,127)	(4,694)
Fair Value, Available for Sale	273,278	231,044
Gross Amortized Cost, Held for Investment Securities	174,080	181,280
Gross Unrealized Gains, Held for Investment Securities	0	56
Gross Unrealized Losses, Held for Investment Securities	(5,841)	(2,767)
Fair Value, Held for Investment Securities	168,239	178,569
Commercial mortgage backed securities of U.S. Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	16,183	16,210
Gross Unrealized Gains, Available for Sale	8	165
Gross Unrealized Losses, Available for Sale	(150)	(34)
Fair Value, Available for Sale	16,041	16,341
Gross Amortized Cost, Held for Investment Securities	17,487	17,462
Gross Unrealized Gains, Held for Investment Securities	412	705
Gross Unrealized Losses, Held for Investment Securities	0	0
Fair Value, Held for Investment Securities	17,899	18,167
Private mortgage backed securities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	18,070	18,056
Gross Unrealized Gains, Available for Sale	379	384
Gross Unrealized Losses, Available for Sale	0	0
Fair Value, Available for Sale	18,449	18,440
Fair Value, Held for Investment Securities	0
Private collateralized mortgage obligations [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	44,374	47,045
Gross Unrealized Gains, Available for Sale	608	605
Gross Unrealized Losses, Available for Sale	(266)	(285)
Fair Value, Available for Sale	44,716	47,365
Gross Amortized Cost, Held for Investment Securities	5,018	5,337
Gross Unrealized Gains, Held for Investment Securities	9	9
Gross Unrealized Losses, Held for Investment Securities	(47)	(53)
Fair Value, Held for Investment Securities	4,980	5,293
Collateralized loan obligations [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	256,058	263,579
Gross Unrealized Gains, Available for Sale	731	798
Gross Unrealized Losses, Available for Sale	(3)	(68)
Fair Value, Available for Sale	256,786	264,309
Gross Amortized Cost, Held for Investment Securities	35,600	40,523
Gross Unrealized Gains, Held for Investment Securities	211	303
Gross Unrealized Losses, Held for Investment Securities	0	0
Fair Value, Held for Investment Securities	35,811	40,826
Obligations of state and political subdivisions [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	45,003	45,118
Gross Unrealized Gains, Available for Sale	384	813
Gross Unrealized Losses, Available for Sale	(481)	(70)
Fair Value, Available for Sale	$ 44,906	$ 45,861

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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.

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-Publisher FASB
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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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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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-Publisher FASB
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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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