Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Allowance for loan losses	$ 93,580	$ 84,812
Net unrealized losses on AFS debt securities	19,704	12,404
Share-based compensation expense	10,642	9,418
State income taxes	13,854	9,186
Accrued compensation	8,291	8,336
Deferred rent	7,940	8,169
Other accruals	7,061	7,165
Net operating loss	2,447	2,300
Loan fee income and costs	0	1,189
Other	11,339	3,639
Deferred tax assets	174,858	146,618
Valuation allowance	(2,107)	(2,624)
Net deferred tax assets after valuation allowance	172,751	143,994
Deferred tax liabilities:
Derivative equity warrant assets	(32,861)	(29,127)
Change in accounting method (section 481(a))	(8,034)	(15,953)
Net unrealized gains on AFS equity securities	0	(11,145)
Non-marketable and other equity securities	(45,759)	(10,724)
Premises and equipment and other intangibles	(10,284)	(9,223)
Other	(10,380)	(3,977)
Deferred tax liabilities	(107,318)	(80,149)
Net deferred tax assets	$ 65,433	$ 63,845