Fair Value Measurement and Fair Value of Financial Instruments (Quantitative Information for Significant Unobservable Inputs) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Quantitative information
Derivative assets	$ 66,146	$ 83,780
Available-for-sale investment securities	3,016,752	3,335,795
Other securities
Quantitative information
Available-for-sale investment securities	31,342	40,329
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Quantitative information
Derivative assets	679	0
Available-for-sale investment securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Warrants
Quantitative information
Warrants	679
Derivative assets	$ 679
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Warrants \| Black-Scholes option pricing model \| Weighted Average
Quantitative information
Volatility	44.00%
Liquidity discount	47.00%
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Other securities
Quantitative information
Available-for-sale investment securities	$ 0	0
Fair Value, Measurements, Nonrecurring \| Non-PCI impaired loans
Quantitative information
Impaired loans	38,188	70,154
Fair Value, Measurements, Nonrecurring \| OREO
Quantitative information
OREO	9	345
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans
Quantitative information
Impaired loans	38,188	70,154
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Discounted cash flows
Quantitative information
Impaired loans	$ 22,802	$ 31,835
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Discounted cash flows \| Minimum
Quantitative information
Discount	4.00%	4.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Discounted cash flows \| Maximum
Quantitative information
Discount	10.00%	8.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Discounted cash flows \| Weighted Average
Quantitative information
Discount	6.00%	5.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of collateral, discount
Quantitative information
Impaired loans	$ 3,207	$ 18,417
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of collateral, discount \| Minimum
Quantitative information
Discount	20.00%	0.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of collateral, discount \| Maximum
Quantitative information
Discount	32.00%	75.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of collateral, discount \| Weighted Average
Quantitative information
Discount	29.00%	35.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of collateral, contract value
Quantitative information
Impaired loans	$ 2,406	$ 4,961
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of property
Quantitative information
Impaired loans	$ 9,773	$ 14,941
Selling cost	8.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of property \| Minimum
Quantitative information
Selling cost		4.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of property \| Maximum
Quantitative information
Selling cost		8.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| Non-PCI impaired loans \| Fair value of property \| Weighted Average
Quantitative information
Selling cost	8.00%	6.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| OREO
Quantitative information
OREO	$ 9	$ 345
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| OREO \| Fair value of property
Quantitative information
OREO	$ 9	$ 345
Selling cost	8.00%	8.00%
Fair Value, Measurements, Nonrecurring \| Significant Unobservable Inputs (Level 3) \| OREO \| Fair value of property \| Weighted Average
Quantitative information
Selling cost	8.00%	8.00%

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- Definition

Impaired Loans, Fair Value Disclosure

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and elected not to be offset.

+ References

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-Publisher FASB
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- Definition

Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Adjustment to the discount rate used to measure fair value for lack of ability to convert business interests into cash quickly.

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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Amount of issuances of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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