Investment Securities (Details 4) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value
Less than 12 months	$ 225,437,000		$ 225,437,000		$ 154,826,000
12 months or more	23,233,000		23,233,000		1,571,000
Total	248,670,000		248,670,000		156,397,000
Unrealized Losses
Less than 12 months	(871,000)		(871,000)		(2,760,000)
12 months or more	(6,000)		(6,000)		(2,000)
Total	(877,000)		(877,000)		$ (2,762,000)
Sales of Available-For-Sale Securities
Gains from sales of available-for-sale securities			2,800,000	$ 5,600,000
Proceeds from sales of available-for-sale securities	$ 0	$ 4,000,000.0	$ 31,000,000.0	$ 35,800,000