Fair Value Measurements - Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Liabilities
Common stock warrants	$ (5,007)	$ (6,808)
Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	5,595	26,274
Derivative asset, fair value, gross liability	(431)	(19,650)
Derivative asset	5,164	6,624
Liabilities
Fair value of derivative liability	(2,053)	(46,061)
Derivative liability, fair value, gross asset	431	19,650
Derivative liability	(1,622)	(26,411)
Cash collateral	10,900	7,200
Interest rate derivatives \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	191	3,810
Derivative asset, fair value, gross liability	0	0
Derivative asset	191	3,810
Fair Value, Inputs, Level 1 \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	170	557
Liabilities
Fair value of derivative liability	(870)	(596)
Fair Value, Inputs, Level 1 \| Interest rate derivatives \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	0	0
Fair Value, Inputs, Level 2 \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	5,425	25,717
Liabilities
Fair value of derivative liability	(261)	(19,093)
Fair Value, Inputs, Level 2 \| Interest rate derivatives \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	191	3,810
Fair Value, Inputs, Level 3 \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	0	0
Liabilities
Fair value of derivative liability	(922)	(26,372)
Fair Value, Inputs, Level 3 \| Interest rate derivatives \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	0	0
Exchange Traded \| Future \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	5,404	22,464
Derivative asset, fair value, gross liability	(431)	(19,650)
Derivative asset	4,973	2,814
Liabilities
Fair value of derivative liability	(1,131)	(19,689)
Derivative liability, fair value, gross asset	431	19,650
Derivative liability	(700)	(39)
Exchange Traded \| J. Aron repurchase obligation derivative \| Fair Value, Measurements, Recurring
Liabilities
Fair value of derivative liability	4,085	(19,564)
Derivative liability, fair value, gross asset	0	0
Derivative liability	4,085	(19,564)
Exchange Traded \| Fair Value, Inputs, Level 1 \| Future \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	170	557
Liabilities
Fair value of derivative liability	(870)	(596)
Exchange Traded \| Fair Value, Inputs, Level 1 \| J. Aron repurchase obligation derivative \| Fair Value, Measurements, Recurring
Liabilities
Fair value of derivative liability	0	0
Exchange Traded \| Fair Value, Inputs, Level 2 \| Future \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	5,234	21,907
Liabilities
Fair value of derivative liability	(261)	(19,093)
Exchange Traded \| Fair Value, Inputs, Level 2 \| J. Aron repurchase obligation derivative \| Fair Value, Measurements, Recurring
Liabilities
Fair value of derivative liability	0	0
Exchange Traded \| Fair Value, Inputs, Level 3 \| Future \| Fair Value, Measurements, Recurring
Assets
Fair value of derivative asset	0	0
Liabilities
Fair value of derivative liability	0	0
Exchange Traded \| Fair Value, Inputs, Level 3 \| J. Aron repurchase obligation derivative \| Fair Value, Measurements, Recurring
Liabilities
Fair value of derivative liability	4,085	(19,564)
Over the Counter \| Fair Value, Measurements, Recurring
Liabilities
Common stock warrants	(5,007)	(6,808)
Derivative liability, fair value, gross asset	0	0
Over the Counter \| Fair Value, Inputs, Level 1 \| Fair Value, Measurements, Recurring
Liabilities
Common stock warrants	0	0
Over the Counter \| Fair Value, Inputs, Level 2 \| Fair Value, Measurements, Recurring
Liabilities
Common stock warrants	0	0
Over the Counter \| Fair Value, Inputs, Level 3 \| Fair Value, Measurements, Recurring
Liabilities
Common stock warrants	$ (5,007)	$ (6,808)

Fair value of liability associated with 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.

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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 elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, before effects of master netting arrangements, of a financial liability or 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 liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

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Fair value of asset associated with financial liability or 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.

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Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.

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