Securities (Realized Gains and Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 42,085	$ 249,233	$ 256,875	$ 551,889
Gross realized gains	210	2,720	2,339	5,194
Related tax expense	$ 62	$ 1,144	$ 690	$ 2,184