Fair Value Measurement and Fair Value of Financial Instruments (Details 3) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Quantitative information
Available-for-sale investment securities	$ 2,956,776	$ 3,335,795
Derivative assets	80,466	83,780
Other securities
Quantitative information
Available-for-sale investment securities	147,135	40,329
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Quantitative information
Available-for-sale investment securities	115,615	0
Derivative assets	599	0
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Warrants
Quantitative information
Derivative assets	599
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Other securities
Quantitative information
Available-for-sale investment securities	115,615	$ 0
Significant Unobservable Inputs (Level 3) \| Discounted cash flows \| Fair Value, Measurements, Recurring \| Other securities
Quantitative information
Available-for-sale investment securities	$ 115,615
Significant Unobservable Inputs (Level 3) \| Discounted cash flows \| Fair Value, Measurements, Recurring \| Other securities \| Weighted Average
Quantitative information
Discount margin	1.91%
Significant Unobservable Inputs (Level 3) \| Black-Scholes option pricing model \| Fair Value, Measurements, Recurring \| Warrants
Quantitative information
Derivative assets	$ 599
Significant Unobservable Inputs (Level 3) \| Black-Scholes option pricing model \| Fair Value, Measurements, Recurring \| Warrants \| Weighted Average
Quantitative information
Volatility	44.00%
Liquidity discount	47.00%

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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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