Fair Value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Earning assets
Loans held for investment, net, difference	$ 1,369,562	$ 713,135
Tax indemnification receivable	276,543	186,076
Derivative instruments	29,299	6,036
Total earning assets, difference	1,369,562	713,135
Interest-bearing liabilities
Long-term borrowings, difference	(31,296)	11,633
Total interest-bearing liabilities, difference	(56,209)	14,636
Excess of net asset fair value over carrying value	1,313,353	727,771
Certificates of deposit
Interest-bearing liabilities
Certificates of deposit, difference	(24,913)	3,003
Fair Value
Earning assets
Loans held for investment, net	16,130,066	12,343,726
Cash and cash equivalents	1,454,938	2,416,219
Available-for-sale investments	213,176	195,391
Accrued interest receivable	805,647	564,496
Tax indemnification receivable	276,543	186,076
Derivative instruments	43,410	15,314
Total earning assets	18,923,780	15,721,222
Interest-bearing liabilities
Short-term borrowings	350,000	500,175
Long-term borrowings	1,608,985	567,468
Accrued interest payable	26,587	16,385
Derivative instruments	52,578	30,497
Total interest-bearing liabilities	15,004,083	12,599,229
Fair Value \| Money-market and savings accounts
Interest-bearing liabilities
Deposits	6,520,085	5,556,254
Fair Value \| Certificates of deposit
Interest-bearing liabilities
Deposits	6,445,848	5,928,450
Carrying Value
Earning assets
Loans held for investment, net	14,760,504	11,630,591
Cash and cash equivalents	1,454,938	2,416,219
Available-for-sale investments	213,176	195,391
Accrued interest receivable	805,647	564,496
Tax indemnification receivable	276,543	186,076
Derivative instruments	43,410	15,314
Total earning assets	17,554,218	15,008,087
Interest-bearing liabilities
Short-term borrowings	350,000	500,175
Long-term borrowings	1,577,689	579,101
Accrued interest payable	26,587	16,385
Derivative instruments	52,578	30,497
Total interest-bearing liabilities	14,947,874	12,613,865
Carrying Value \| Money-market and savings accounts
Interest-bearing liabilities
Deposits	6,520,085	5,556,254
Carrying Value \| Certificates of deposit
Interest-bearing liabilities
Deposits	$ 6,420,935	$ 5,931,453

Accrued Interest Receivable, Fair Value Disclosure

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Assets, Fair Value Disclosure, Difference Between Carrying Value and Fair Value

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Deposits, Fair Value Disclosure, Difference Between Carrying Value and Fair Value

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Excess of net asset fair value over carrying value.

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Financial Liabilities Fair Value Disclosure, Difference Between Carrying Value and Fair Value

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Loans Receivable, Fair Value Disclosure, Difference

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Long-term Debt, Fair Value, Difference Between Carrying Value and Fair Value

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Fair value portion of accrued expenses.

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

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value, after the 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 not elected to be offset.

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Fair value, after the 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 not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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Carrying amount as of the balance sheet date of income taxes previously overpaid to tax authorities (such as U.S. Federal, state and local tax authorities) representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes. Also called income tax refund receivable.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

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