Accumulated Other Comprehensive Loss (Reclassifications Out of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gross gains									$ 325	$ 631	$ 0
Income tax (expense)/benefit	$ (18,969)	$ (2,848)	$ (10,532)	$ (9,757)	$ (10,200)	$ (9,600)	$ (9,100)	$ (8,100)	(42,106)	(37,000)	(27,500)
Net gain on sale of investment securities									129	630	0
Net Income									(1,395)	(2,247)	(1,420)
Unrealized gains (losses) on securities available-for-sale, net of tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income									84	409	0
Unrealized gains (losses) on securities available-for-sale, net of tax | Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gross gains									129	630	0
Income tax (expense)/benefit									(45)	(221)	0
Net gain on sale of investment securities									84	409	0
Amortization of defined benefit pension plan items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries, wages and employee benefits (operating expenses)									(2,276)	(4,086)	(2,184)
Income tax (expense)/benefit									797	1,430	764
Net Income									$ (1,479)	$ (2,656)	$ (1,420)