Investments - Reconciliation from Amortized Cost to Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available for sale securities (AFS):
Amortized cost	$ 172,321	$ 130,308
Gross unrealized gains	5,666	3,245
Gross unrealized losses	396	572
Fair value	177,591	132,981
Held to maturity securities (HTM):
Amortized cost	360,935	366,041
Gross unrealized gains	1,249	718
Gross unrealized losses	1,804	3,581
Fair value	360,380	363,178
Mortgage-backed securities
Held to maturity securities (HTM):
Amortized cost	315,135	319,978
Gross unrealized gains	466	186
Gross unrealized losses	1,474	2,531
Fair value	314,127	317,633
Trust preferred securities
Available for sale securities (AFS):
Amortized cost	35,607	36,450
Gross unrealized gains	3,464	1,707
Gross unrealized losses	380	533
Fair value	38,691	37,624
Held to maturity securities (HTM):
Amortized cost	10,695	10,620
Gross unrealized gains	495	522
Gross unrealized losses	326	267
Fair value	10,864	10,875
Corporate debt securities
Available for sale securities (AFS):
Amortized cost	133,460	90,593
Gross unrealized gains	2,142	1,505
Gross unrealized losses	12	21
Fair value	135,590	92,077
Municipal securities
Available for sale securities (AFS):
Amortized cost	3,254	3,265
Gross unrealized gains	60	33
Gross unrealized losses	4	18
Fair value	3,310	3,280
Held to maturity securities (HTM):
Amortized cost	35,105	35,443
Gross unrealized gains	288	10
Gross unrealized losses	4	783
Fair value	$ 35,389	$ 34,670

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

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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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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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