Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses)	$ (288)	$ (8)
Tax expense (benefit)	2,460	4,519
Net income	15,814	11,277
Unrealized Gains (Losses) on AFS Securities [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses)	149	(8)
Tax expense (benefit)	31	(3)
Net income	$ 118	$ (5)