Accumulated Other Comprehensive Income (Loss) - Changes in components of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period			$ 1,017
Other comprehensive income, net of tax	$ 4,307	$ 1,404	16,029	$ 27,751
Balance at the end of the period	17,046	2,870	17,046	2,870
Benefit Plans
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(149)	(297)	(149)	(6,450)
Amounts reclassified from accumulated other comprehensive income				6,153
Other comprehensive income, net of tax				6,153
Balance at the end of the period	(149)	(297)	(149)	(297)
Unrealized Gains and Losses on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	48,315	12,944	11,922	(18,394)
Other comprehensive income (loss) before reclassifications	1,494	5,824	37,887	34,732
Amounts reclassified from accumulated other comprehensive income	(12)	(341)	(12)	2,089
Other comprehensive income, net of tax	1,482	5,483	37,875	36,821
Balance at the end of the period	49,797	18,427	49,797	18,427
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(35,427)	(11,181)	(10,756)	(37)
Other comprehensive income (loss) before reclassifications	128	(3,891)	(26,638)	(14,766)
Amounts reclassified from accumulated other comprehensive income	2,697	(188)	4,792	(457)
Other comprehensive income, net of tax	2,825	(4,079)	(21,846)	(15,223)
Balance at the end of the period	(32,602)	(15,260)	(32,602)	(15,260)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	12,739	1,466	1,017	(24,881)
Other comprehensive income (loss) before reclassifications	1,622	1,933	11,249	19,966
Amounts reclassified from accumulated other comprehensive income	2,685	(529)	4,780	7,785
Other comprehensive income, net of tax	4,307	1,404	16,029	27,751
Balance at the end of the period	$ 17,046	$ 2,870	$ 17,046	$ 2,870