Derivative Financial Instruments - Impact of Derivatives on Consolidated Statements of Income (Details) - Interest rate swaps - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Trading
Gain (loss) on derivatives, net	$ (874)	$ 3,931	$ (8,441)	$ 11,161
Designated as Hedging Instrument \| Fair Value Hedges
Fair Value Hedges
Hedge ineffectiveness gains (losses) recorded in earnings	2,748	3,199	(5,130)	2,000
Realized gains (losses) recorded in interest expense	154	6,944	7,582	21,593
Trading
Gain (loss) on derivatives, net	2,902	10,143	2,452	23,593
Designated as Hedging Instrument \| Cash Flow Hedges
Cash Flow Hedges
Hedge ineffectiveness losses recorded in earnings	(1,025)	(843)	(1,172)	(1,524)
Realized losses recorded in interest expense	(2,689)	(4,381)	(8,697)	(13,588)
Trading
Gain (loss) on derivatives, net	(3,714)	(5,224)	(9,869)	(15,112)
Trading
Trading
Interest reclassification	185	537	165	1,897
Realized gains (losses) recorded in earnings	(247)	(1,525)	(1,189)	783
Gain (loss) on derivatives, net	$ (62)	$ (988)	$ (1,024)	$ 2,680

Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Hedge Ineffectiveness

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Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Interest Reclassification

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

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-Publisher FASB
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The net gain (loss) relating to components of the gain (loss) on the cash flow hedging instrument excluded from the assessment of cash flow hedge effectiveness. Recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 50
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The net gain (loss) recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
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Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-SubTopic 25
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