Fair Value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Earning assets
Loans held for investment, net, difference	$ 1,788,579	$ 1,382,864
Cash and cash equivalents, difference	0	0
Tax indemnification receivable	233,142	259,532
Derivative instruments	0	0
Total earning assets, difference	1,788,579	1,382,864
Interest-bearing liabilities
Long-term borrowings, difference	(27,260)	7,874
Total interest-bearing liabilities, difference	(37,589)	(31,565)
Excess of net asset fair value over carrying value	1,750,990	1,351,299
Certificates of deposit
Interest-bearing liabilities
Certificates of deposit, difference	(10,329)	(39,439)
Fair Value
Earning assets
Loans held for investment, net	18,349,005	16,520,786
Cash and cash equivalents	1,318,168	1,918,793
Available-for-sale investments	229,479	208,603
Accrued interest receivable	926,270	766,106
Tax indemnification receivable	233,142	259,532
Derivative instruments	326	7,808
Total earning assets	21,056,390	19,681,628
Interest-bearing liabilities
Short-term borrowings	0	0
Long-term borrowings	2,899,491	2,160,105
Accrued interest payable	27,114	21,058
Derivative instruments	11,252	25,937
Total interest-bearing liabilities	16,741,391	15,681,529
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	8,015,192	7,963,925
Fair Value | Certificates of deposit
Interest-bearing liabilities
Deposits	5,788,342	5,510,504
Carrying Value
Earning assets
Loans held for investment, net	16,560,426	15,137,922
Cash and cash equivalents	1,318,168	1,918,793
Available-for-sale investments	229,479	208,603
Accrued interest receivable	926,270	766,106
Tax indemnification receivable	233,142	259,532
Derivative instruments	326	7,808
Total earning assets	19,267,811	18,298,764
Interest-bearing liabilities
Short-term borrowings	0	0
Long-term borrowings	2,872,231	2,167,979
Accrued interest payable	27,114	21,058
Derivative instruments	11,252	25,937
Total interest-bearing liabilities	16,703,802	15,649,964
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	8,015,192	7,963,925
Carrying Value | Certificates of deposit
Interest-bearing liabilities
Deposits	$ 5,778,013	$ 5,471,065