Fair value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Earning assets
Tax indemnification receivable	$ 186,076	$ 240,311
Derivative instruments	6,036	1,193
Interest-bearing liabilities
Derivative instruments	21,219	24,643
Fair Value
Earning assets
Loans held for investment, net	12,343,726	10,228,399
Cash and cash equivalents	2,416,219	2,359,780
Available for sale investments	195,391	168,934
Accrued interest receivable	564,496	469,697
Tax indemnification receivable	186,076	240,311
Derivative instruments	15,314	5,238
Total	15,721,222	13,472,359
Interest-bearing liabilities
Accrued interest payable	16,385	16,082
Derivative instruments	30,497	28,688
Total interest-bearing liabilities	12,599,229	10,590,151
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,556,254	5,231,736
Fair Value | Certificates of Deposit
Interest-bearing liabilities
Deposits	5,928,450	5,313,645
Fair Value | Short-term borrowings
Interest-bearing liabilities
Deposits	500,175	0
Fair Value | Long-term borrowings
Interest-bearing liabilities
Deposits	567,468	0
Carrying Value
Earning assets
Loans held for investment, net	11,630,591	9,509,786
Cash and cash equivalents	2,416,219	2,359,780
Available for sale investments	195,391	168,934
Accrued interest receivable	564,496	469,697
Tax indemnification receivable	186,076	240,311
Derivative instruments	15,314	5,238
Total	15,008,087	12,753,746
Interest-bearing liabilities
Accrued interest payable	16,385	16,082
Derivative instruments	30,497	28,688
Total interest-bearing liabilities	12,613,865	10,585,324
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,556,254	5,231,736
Carrying Value | Certificates of Deposit
Interest-bearing liabilities
Deposits	5,931,453	5,308,818
Carrying Value | Short-term borrowings
Interest-bearing liabilities
Deposits	500,175	0
Carrying Value | Long-term borrowings
Interest-bearing liabilities
Deposits	579,101	0
Difference
Earning assets
Loans held for investment, net	713,135	718,613
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	713,135	718,613
Interest-bearing liabilities
Accrued interest payable	0	0
Derivative instruments	0	0
Total interest-bearing liabilities	14,636	(4,827)
Excess of net asset fair value over carrying value	727,771	713,786
Difference | Money-market and savings accounts
Interest-bearing liabilities
Deposits	0	0
Difference | Certificates of Deposit
Interest-bearing liabilities
Deposits	3,003	(4,827)
Difference | Short-term borrowings
Interest-bearing liabilities
Deposits	0	0
Difference | Long-term borrowings
Interest-bearing liabilities
Deposits	$ 11,633	$ 0