Deposits (Summary of Deposits) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Banking and Thrift [Abstract]
Demand checking accounts	$ 1,141,578	$ 1,033,551
NOW accounts	371,380	336,317
Savings accounts	613,467	619,961
Money market accounts	1,682,005	1,675,050
Total core deposit accounts	3,808,430	3,664,879
Certificate of deposit accounts maturing:
Within six months	730,512	475,303
After six months but within 1 year	650,461	562,018
After 1 year but within 2 years	495,509	538,435
After 2 years but within 3 years	56,508	95,806
After 3 years but within 4 years	58,492	46,027
After 4 years but within 5 years	29,759	71,556
After 5 Years	401	20
Total certificate of deposit accounts	2,021,642	1,789,165
Total deposits	$ 5,830,072	$ 5,454,044
Weighted Average Rate of Demand checking accounts
Demand checking accounts (as a percent)	0.00%	0.00%
NOW accounts (as a percent)	0.11%	0.10%
Savings accounts (as a percent)	0.46%	0.32%
Money market savings accounts (as a percent)	1.15%	1.18%
Total transaction deposit accounts (as a percent)	0.59%	0.60%
Weighted Average Rate of Certificate of deposit accounts maturing:
Within six months (as a percent)	2.24%	1.20%
After six months but within 1 year (as a percent)	2.24%	1.40%
After 1 year but within 2 years (as a percent)	2.26%	1.85%
After 2 years but within 3 years (as a percent)	2.19%	2.16%
After 3 years but within 4 years (as a percent)	2.64%	1.73%
After 4 years but within 5 years (as a percent)	2.58%	2.57%
After 5 years (as a percent)	2.19%	1.98%
Total certificate of deposit accounts (as a percent)	2.26%	1.58%
Total of weighted average rate of deposits (as a percent)	1.17%	0.92%