Fair Value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Earning assets
Tax indemnification receivable	$ 187,156	$ 186,076
Derivative instruments	37,802	6,036
Interest-bearing liabilities
Derivative instruments	38,045	21,219
Fair Value
Earning assets
Loans held for investment, net	13,911,665	12,343,726
Cash and cash equivalents	938,480	2,416,219
Available-for-sale investments	203,597	195,391
Accrued interest receivable	650,813	564,496
Tax indemnification receivable	187,156	186,076
Derivative instruments	52,007	15,314
Total earning assets	15,943,718	15,721,222
Interest-bearing liabilities
Short-term borrowings	526,500	500,175
Long-term borrowings	555,365	567,468
Accrued interest payable	25,464	16,385
Derivative instruments	52,250	30,497
Total interest-bearing liabilities	12,721,829	12,599,229
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,805,018	5,556,254
Fair Value | Certificates of deposit
Interest-bearing liabilities
Deposits	5,757,232	5,928,450
Carrying Value
Earning assets
Loans held for investment, net	13,108,425	11,630,591
Cash and cash equivalents	938,480	2,416,219
Available-for-sale investments	203,597	195,391
Accrued interest receivable	650,813	564,496
Tax indemnification receivable	187,156	186,076
Derivative instruments	52,007	15,314
Total earning assets	15,140,478	15,008,087
Interest-bearing liabilities
Short-term borrowings	526,500	500,175
Long-term borrowings	558,513	579,101
Accrued interest payable	25,464	16,385
Derivative instruments	52,250	30,497
Total interest-bearing liabilities	12,705,119	12,613,865
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,805,018	5,556,254
Carrying Value | Certificates of deposit
Interest-bearing liabilities
Deposits	5,737,374	5,931,453
Difference
Earning assets
Loans held for investment, net	803,240	713,135
Cash and cash equivalents	0	0
Available-for-sale investments	0	0
Accrued interest receivable	0	0
Tax indemnification receivable	0	0
Derivative instruments	0	0
Total earning assets	803,240	713,135
Interest-bearing liabilities
Short-term borrowings	0	0
Long-term borrowings	3,148	11,633
Accrued interest payable	0	0
Derivative instruments	0	0
Total interest-bearing liabilities	(16,710)	14,636
Excess of net asset fair value over carrying value	786,530	727,771
Difference | Money-market and savings accounts
Interest-bearing liabilities
Deposits	0	0
Difference | Certificates of deposit
Interest-bearing liabilities
Deposits	$ (19,858)	$ 3,003