Investments Maturities of AFS Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 60,984
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	342,959
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis	321,379
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	471,313
Investment securities available for sale at amortized cost	1,196,635	$ 1,283,161
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	61,511
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	344,253
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	315,209
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	468,854
Available-for-sale Securities	$ 1,189,827	$ 1,264,132

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

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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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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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