Securities (Realized Gain (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Available for Sale Securities sold:
Proceeds from sales	$ 909,942	$ 1,115,359	$ 791,767
Gross security gains	13,200	15,205	5,871
Gross security losses	$ 1,562	$ 2,022	$ 2,203