Fair Value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Earning assets
Loans held for investment, net, difference	$ 1,040,627	$ 713,135
Tax indemnification receivable	160,325	186,076
Derivative instruments	48,943	6,036
Total earning assets, difference	1,040,627	713,135
Interest-bearing liabilities
Long-term borrowings, difference	(15,057)	11,633
Derivative instruments	44,719	21,219
Total interest-bearing liabilities, difference	(34,465)	14,636
Excess of net asset fair value over carrying value	1,006,162	727,771
Certificates of deposit
Interest-bearing liabilities
Certificates of deposit, difference	(19,408)	3,003
Fair Value
Earning assets
Loans held for investment, net	14,286,053	12,343,726
Cash and cash equivalents	1,042,915	2,416,219
Available-for-sale investments	206,785	195,391
Accrued interest receivable	719,875	564,496
Tax indemnification receivable	160,325	186,076
Derivative instruments	65,116	15,314
Total earning assets	16,481,069	15,721,222
Interest-bearing liabilities
Short-term borrowings		500,175
Long-term borrowings	1,053,086	567,468
Accrued interest payable	19,309	16,385
Derivative instruments	60,892	30,497
Total interest-bearing liabilities	13,051,618	12,599,229
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,883,818	5,556,254
Fair Value | Certificates of deposit
Interest-bearing liabilities
Deposits	6,034,513	5,928,450
Carrying Value
Earning assets
Loans held for investment, net	13,245,426	11,630,591
Cash and cash equivalents	1,042,915	2,416,219
Available-for-sale investments	206,785	195,391
Accrued interest receivable	719,875	564,496
Tax indemnification receivable	160,325	186,076
Derivative instruments	65,116	15,314
Total earning assets	15,440,442	15,008,087
Interest-bearing liabilities
Short-term borrowings		500,175
Long-term borrowings	1,038,029	579,101
Accrued interest payable	19,309	16,385
Derivative instruments	60,892	30,497
Total interest-bearing liabilities	13,017,153	12,613,865
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,883,818	5,556,254
Carrying Value | Certificates of deposit
Interest-bearing liabilities
Deposits	$ 6,015,105	$ 5,931,453