Securities - Amortized Cost and Fair Value of Securities Available for Sale and Held to Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Dec. 30, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized cost within one year	$ 9,773	$ 7,455
Amortized cost one to five years	48,118	37,483
Amortized cost for five to ten years	33,409	21,112
Amortized cost for after ten years	66,492	60,566
Total amortized cost	157,792	126,616
Total available for sale investment securities, Amortized Cost	504,855	445,839
Within one year, amortized cost	7,383
One to five years, amortized cost	32,290	24,594
Five to ten years, amortized cost	85,899	87,645
After ten years, amortized cost	52,209	53,368
Total amortized cost	177,781	165,607
Total held to maturity investment securities, amortized cost	199,474	193,194
Fair value within one year	9,787	7,480
Fair value for one to five years	48,199	37,479
Fair value for five to ten years	33,891	20,984
Fair value for after ten years	68,511	59,967
Total fair value	160,388	125,910
Investment securities, available for sale	505,051	439,831
Within one year, fair value	7,366
One to five years, fair value	33,413	25,271
five to ten years, fair value	88,391	88,805
After ten years, fair value	52,364	51,746
Total fair value	181,534	165,822
Held-to-maturity, fair value	203,542	194,086	$ 194,086
Federal Agency Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	133,038	139,040
Total held to maturity investment securities, amortized cost	6,102	6,530
Investment securities, available for sale	131,914	137,195
Held-to-maturity, fair value	6,114	6,490
Federal Agency Mortgage-backed Pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	212,154	180,183
Total held to maturity investment securities, amortized cost	15,591	21,057
Investment securities, available for sale	210,881	176,726
Held-to-maturity, fair value	15,894	$ 21,774
Private Labeled Mortgage-backed Pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	1,871
Investment securities, available for sale	$ 1,868

Available for sale securities debt maturities rolling fair value.

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Held To Maturity Securities Debt Maturities Amortized Cost

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Held To Maturity Securities Debt Maturities Fair Value Aggregate

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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 next rolling twelve months following the latest balance sheet. 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. For 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 rolling twelve months following the latest balance sheet. 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. For 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 rolling twelve months following the latest balance sheet. For 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 sixth through tenth rolling twelve months following the latest balance sheet. 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. For 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 through tenth rolling twelve months following the latest balance sheet. For 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 through fifth rolling twelve months following the latest balance sheet. 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. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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

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Fair value of held-to-maturity debt securities maturing in the next rolling twelve months following the latest balance sheet. For 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 held-to-maturity debt securities maturing after the tenth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amortized cost of held-to-maturity debt securities maturing in the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amortized cost of held-to-maturity debt securities maturing after the tenth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amortized cost of held-to-maturity debt securities maturing in the sixth through tenth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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