Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on sales of available for sale securities	$ 1,140	$ 1,609
Interest expense - subordinated debentures and term loans	2,116	1,990
Income tax expense	(6,941)	(6,611)
Total reclassifications for the period, net of tax	854	1,137
Unrealized gains (losses) on available for sale securities
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax	901	1,271
Unrealized gains (losses) on cash flow hedges
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax	(47)	(134)
Unrealized Gains (Losses) on Defined Benefit Plans
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax	0	0
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period | Unrealized gains (losses) on available for sale securities
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on sales of available for sale securities	1,140	1,609
Income tax expense	(239)	(338)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period | Unrealized gains (losses) on cash flow hedges
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	12	36
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period | Unrealized gains (losses) on cash flow hedges | Interest rate contracts
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Interest expense - subordinated debentures and term loans	$ (59)	$ (170)