Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost
Due within one year	$ 23,491
Due after one year through five years	106,577
Due after five years through ten years	147,761
Due after ten years	94,150
Amortized Cost	1,141,627	$ 686,405
Fair Value
Due within one year	23,798
Due after one year through five years	110,274
Due after five years through ten years	153,199
Due after ten years	93,983
Securities available for sale, at fair value	1,150,459	674,248
Residential mortgage-backed securities
Amortized Cost
Available for sale debt securities	2,946
Other debt securities
Amortized Cost
Other debt securities, amortized cost	19,394
Amortized Cost	26,546	22,053
Fair Value
Other debt securities, fair value	19,617
Securities available for sale, at fair value	26,919	22,145
Government agency mortgage backed securities
Amortized Cost
Available for sale debt securities	14,750
Government agency mortgage backed securities \| Residential mortgage-backed securities
Amortized Cost
Available for sale debt securities	459,336
Amortized Cost	459,336	414,019
Fair Value
Securities available for sale, at fair value	459,558	409,317
Government agency mortgage backed securities \| Commercial mortgage-backed securities
Amortized Cost
Available for sale debt securities	45,340
Amortized Cost	45,340	50,628
Fair Value
Securities available for sale, at fair value	45,929	50,863
Government agency collateralized mortgage obligations
Amortized Cost
Available for sale debt securities	16,395
Government agency collateralized mortgage obligations \| Residential mortgage-backed securities
Amortized Cost
Available for sale debt securities	234,224
Amortized Cost	234,224	171,362
Fair Value
Securities available for sale, at fair value	232,658	168,826
Government agency collateralized mortgage obligations \| Commercial mortgage-backed securities
Amortized Cost
Available for sale debt securities	11,354
Amortized Cost	11,354	2,528
Fair Value
Securities available for sale, at fair value	$ 11,443	$ 2,550

This item represents the cost of debt 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 investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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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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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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Amount of available-for-sale debt securities at cost, net of adjustments, that do not have a single maturity date and which the entity has decided to disclose separately rather than allocating the cost over several maturity groupings. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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