Deposits - Composition of Deposits and Interest Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	$ 7,036,576	$ 5,673,922	$ 5,427,891
Interest Expense	63,026	40,856	25,330
Noninterest-bearing demand
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,698,082	1,421,156	1,387,712
Interest Expense	0	0	0
Interest-bearing demand
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	962,331	573,693	603,141
Interest Expense	3,915	93	67
Money market
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,949,811	1,482,065	1,146,156
Interest Expense	30,236	20,018	9,204
Savings
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	830,919	784,970	893,119
Interest Expense	1,928	1,773	2,081
Certificates of deposit
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,595,433	1,412,038	1,397,763
Interest Expense	$ 26,947	$ 18,972	$ 13,978