Fair value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Earning assets
Loans held for investment, net, difference	$ 1,382,864	$ 713,135
Tax indemnification receivable	259,532	186,076
Derivative instruments	0	6,036
Total earning assets, difference	1,382,864	713,135
Interest-bearing liabilities
Long-term borrowings, difference	7,874	11,633
Total interest-bearing liabilities, difference	(31,565)	14,636
Excess of net asset fair value over carrying value	1,351,299	727,771
Certificates of Deposit
Interest-bearing liabilities
Certificates of deposits, difference	(39,439)	3,003
Fair Value
Earning assets
Loans held for investment, net	16,520,786	12,343,726
Cash and cash equivalents	1,918,793	2,416,219
Available-for-sale investments	208,603	195,391
Accrued interest receivable	766,106	564,496
Tax indemnification receivable	259,532	186,076
Derivative instruments	7,808	15,314
Total	19,681,628	15,721,222
Interest-bearing liabilities
Short-term borrowings	0	500,175
Long-term borrowings	2,160,105	567,468
Accrued interest payable	21,058	16,385
Derivative instruments	25,937	30,497
Total interest-bearing liabilities	15,681,529	12,599,229
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	7,963,925	5,556,254
Fair Value | Certificates of Deposit
Interest-bearing liabilities
Deposits	5,510,504	5,928,450
Carrying Value
Earning assets
Loans held for investment, net	15,137,922	11,630,591
Cash and cash equivalents	1,918,793	2,416,219
Available-for-sale investments	208,603	195,391
Accrued interest receivable	766,106	564,496
Tax indemnification receivable	259,532	186,076
Derivative instruments	7,808	15,314
Total	18,298,764	15,008,087
Interest-bearing liabilities
Short-term borrowings	0	500,175
Long-term borrowings	2,167,979	579,101
Accrued interest payable	21,058	16,385
Derivative instruments	25,937	30,497
Total interest-bearing liabilities	15,649,964	12,613,865
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	7,963,925	5,556,254
Carrying Value | Certificates of Deposit
Interest-bearing liabilities
Deposits	$ 5,471,065	$ 5,931,453