Income Taxes Income Tax Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate [Line Items]
Statutory U.S. Federal Tax Rate									21.00%	35.00%
Expected income taxes									$ 10,186	$ 14,604	$ 11,823
Tax-exempt income from bank owned life insurance									283	573	235
Other tax exempt income									(1,598)	(2,223)	(1,577)
Nondeductible interest expense									43	28	21
State taxes, net of federal taxes									3,354	2,062	1,628
Other items									218	(266)	280
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount									0	1,410	0
Effect of marginal tax rate									(15)	0	0
Total	$ 3,206	$ 2,731	$ 3,105	$ 2,863	$ 4,497	$ 3,538	$ 3,927	$ 3,080	$ 11,905	$ 15,042	$ 11,940