Deposits - Components of Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amount
Noninterest demand deposits	$ 1,362,268	$ 944,791
Interest bearing demand deposits	1,317,513	1,051,752
Money market accounts	765,316	499,618
Savings accounts	520,413	498,501
Total non-maturity deposits	3,965,510	2,994,662
Certificate of deposit accounts	466,892	398,398
Total deposits	$ 4,432,402	$ 3,393,060
Percent
Noninterest demand deposits (as a percent)	30.70%	27.80%
Interest bearing demand deposits (as a percent)	29.70%	31.10%
Money market accounts (as a percent)	17.30%	14.70%
Savings accounts (as a percent)	11.80%	14.70%
Total non-maturity deposits (as a percent)	89.50%	88.30%
Certificate of deposit accounts (as a percent)	10.50%	11.70%
Total deposits (as a percent)	100.00%	100.00%