Securities - Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Due within one year	$ 23,584
Due after one year through five years	71,430
Due after five years through ten years	81,302
Due after ten years	75,410
Available-for-sale Securities, Fair Value [Abstract]
Due within one year	23,843
Due after one year through five years	73,379
Due after five years through ten years	83,212
Due after ten years	74,292
Amortized Cost	674,104
Securities available for sale, at fair value	671,488	$ 674,248
Residential mortgage backed securities: \| Government agency mortgage backed securities
Available-for-sale Securities, Fair Value [Abstract]
Amortized Cost	196,121
Securities available for sale, at fair value	193,950	409,317
Residential mortgage backed securities: \| Government agency collateralized mortgage obligations
Available-for-sale Securities, Fair Value [Abstract]
Amortized Cost	180,258
Securities available for sale, at fair value	176,639	168,826
Commercial mortgage backed securities: \| Government agency mortgage backed securities
Available-for-sale Securities, Fair Value [Abstract]
Amortized Cost	31,015
Securities available for sale, at fair value	31,170	50,863
Commercial mortgage backed securities: \| Government agency collateralized mortgage obligations
Available-for-sale Securities, Fair Value [Abstract]
Amortized Cost	5,019
Securities available for sale, at fair value	5,006	$ 2,550
Other debt securities
Available-for-sale Securities, Fair Value [Abstract]
Amortized Cost	9,965
Securities available for sale, at fair value	$ 9,997

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

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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 after adjustments of available-for-sale debt securities at cost, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing after the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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