Organization and Summary of Significant Accounting Policies - Correction of Immaterial Error (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Correction of an Immaterial Error to the Financial Statements
Service charges on deposit accounts	$ 7,933	$ 8,929	$ 23,609	$ 27,548
Credit and debit card fees	16,535	16,126	48,961	48,450
Occupancy expense	6,757	6,238	20,149	17,382
Card rewards program expense	5,805	5,438	17,882	17,107
Net income	$ 67,388	58,363	$ 204,399	171,998
Restatement adjustment | Misclassifications of noninterest income and noninterest expense
Correction of an Immaterial Error to the Financial Statements
Service charges on deposit accounts		(200)		(500)
Credit and debit card fees		1,300		5,000
Occupancy expense		400		1,200
Card rewards program expense		700		3,300
Net income		$ 0		$ 0