Investment Securities - Schedule of Gross Unrealized Losses on Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 121,338	$ 192,171
Less than 12 months, unrealized losses	542	1,084
More than 12 months, fair value	124,903	3,313
More than 12 months, unrealized losses	869	29
Total, fair value	246,241	195,484
Total, unrealized losses	1,411	1,113
U.S. Treasury and government sponsored entities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	116,331	180,638
Less than 12 months, unrealized losses	496	1,051
More than 12 months, fair value	122,605	489
More than 12 months, unrealized losses	840	5
Total, fair value	238,936	181,127
Total, unrealized losses	1,336	1,056
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	3,994	11,533
Less than 12 months, unrealized losses	17	33
More than 12 months, fair value	2,298	1,786
More than 12 months, unrealized losses	29	20
Total, fair value	6,292	13,319
Total, unrealized losses	46	53
Preferred stock
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	1,013	0
Less than 12 months, unrealized losses	29	0
More than 12 months, fair value	0	1,038
More than 12 months, unrealized losses	0	4
Total, fair value	1,013	1,038
Total, unrealized losses	$ 29	$ 4