Accumulated Other Comprehensive Income (Loss) - Changes in components of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	$ 1,017
Other comprehensive income, net of tax	8,748	$ 11,507
Balance at the end of the period	9,765	(13,374)
Benefit Plans
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(149)	(6,450)
Amounts reclassified from accumulated other comprehensive loss		95
Other comprehensive income, net of tax		95
Balance at the end of the period	(149)	(6,355)
Losses on sales of available for sale securities:
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	11,922	(18,394)
Other comprehensive gain (loss) before reclassifications	31,551	15,827
Amounts reclassified from accumulated other comprehensive loss		(2,339)
Other comprehensive income, net of tax	31,551	13,488
Balance at the end of the period	43,473	(4,906)
Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(10,756)	(37)
Other comprehensive gain (loss) before reclassifications	(22,240)	(2,068)
Amounts reclassified from accumulated other comprehensive loss	(563)	(8)
Other comprehensive income, net of tax	(22,803)	(2,076)
Balance at the end of the period	(33,559)	(2,113)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	1,017	(24,881)
Other comprehensive gain (loss) before reclassifications	9,311	13,759
Amounts reclassified from accumulated other comprehensive loss	(563)	(2,252)
Other comprehensive income, net of tax	8,748	11,507
Balance at the end of the period	$ 9,765	$ (13,374)