Income Taxes Deferred Tax (Liabilities) Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Allowance for loan losses	$ 110,248	$ 102,410
Other accruals not currently deductible	20,502	6,670
Share-based compensation expense	15,498	11,979
State income taxes	12,682	11,933
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Deferred Rent	10,050	0
Loan fee income	8,266	13,770
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Other	6,799	8,720
Net operating loss	4,116	4,406
Other	2,168	2,645
Deferred tax assets	190,329	162,533
Valuation allowance	(4,440)	(4,730)
Net deferred tax assets after valuation allowance	185,889	157,803
Deferred tax liabilities:
DeferredTaxLiabilities,ChangeInAccountingMethod	(35,262)	0
Derivative equity warrant assets	(36,406)	(31,955)
Net unrealized gains on available-for-sale securities	(17,970)	(10,199)
Deferred Tax Assets, Property, Plant and Equipment	(11,956)	0
Nonmarketable securities	(6,075)	(35,721)
Deferred Tax Liabilities, Deferred Expense	0	(1,843)
Other	(6,380)	(4,144)
Deferred tax liabilities	(114,049)	(83,862)
Net deferred tax (liabilities) assets	$ 71,840	$ 73,941