Fair Value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Earning assets
Tax indemnification receivable	$ 228,910	$ 240,311
Fair Value
Earning assets
Loans held for investment, net	11,435,475	10,228,399
Cash and cash equivalents	1,278,863	2,359,780
Available-for-sale investments	173,845	168,934
Accrued interest receivable	562,239	469,697
Tax indemnification receivable	228,910	240,311
Derivative instruments	15,189	5,238
Total earning assets	13,694,521	13,472,359
Interest-bearing liabilities
Accrued interest payable	15,731	16,082
Derivative instruments	19,710	28,688
Total interest-bearing liabilities	10,369,862	10,590,151
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,159,236	5,231,736
Fair Value | Certificates of deposit
Interest-bearing liabilities
Deposits	5,175,185	5,313,645
Carrying Value
Earning assets
Loans held for investment, net	10,422,908	9,509,786
Cash and cash equivalents	1,278,863	2,359,780
Available-for-sale investments	173,845	168,934
Accrued interest receivable	562,239	469,697
Tax indemnification receivable	228,910	240,311
Derivative instruments	15,189	5,238
Total earning assets	12,681,954	12,753,746
Interest-bearing liabilities
Accrued interest payable	15,731	16,082
Derivative instruments	19,710	28,688
Total interest-bearing liabilities	10,376,046	10,585,324
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	5,159,236	5,231,736
Carrying Value | Certificates of deposit
Interest-bearing liabilities
Deposits	5,181,369	5,308,818
Difference
Earning assets
Loans held for investment, net	1,012,567	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 earning assets	1,012,567	718,613
Interest-bearing liabilities
Accrued interest payable	0	0
Derivative instruments	0	0
Total interest-bearing liabilities	6,184	(4,827)
Excess of net asset fair value over carrying value	1,018,751	713,786
Difference | Money-market and savings accounts
Interest-bearing liabilities
Deposits	0	0
Difference | Certificates of deposit
Interest-bearing liabilities
Deposits	$ 6,184	$ (4,827)