Accumulated Other Comprehensive Income (Loss) - Changes in components of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period			$ 1,017
Other comprehensive income, net of tax	$ 2,974	$ 14,840	11,722	$ 26,347
Balance at the end of the period	12,739	1,466	12,739	1,466
Benefit Plans
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(149)	(6,355)	(149)	(6,450)
Amounts reclassified from accumulated other comprehensive loss		6,058		6,153
Other comprehensive income, net of tax		6,058		6,153
Balance at the end of the period	(149)	(297)	(149)	(297)
Losses on sales of available for sale securities:
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	43,473	(4,906)	11,922	(18,394)
Other comprehensive gain (loss) before reclassifications	4,842	17,758	36,393	28,908
Amounts reclassified from accumulated other comprehensive loss		92		2,430
Other comprehensive income, net of tax	4,842	17,850	36,393	31,338
Balance at the end of the period	48,315	12,944	48,315	12,944
Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(33,559)	(2,113)	(10,756)	(37)
Other comprehensive gain (loss) before reclassifications	(3,400)	(8,795)	(26,766)	(10,876)
Amounts reclassified from accumulated other comprehensive loss	1,532	(273)	2,095	(268)
Other comprehensive income, net of tax	(1,868)	(9,068)	(24,671)	(11,144)
Balance at the end of the period	(35,427)	(11,181)	(35,427)	(11,181)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	9,765	(13,374)	1,017	(24,881)
Other comprehensive gain (loss) before reclassifications	1,442	8,963	9,627	18,032
Amounts reclassified from accumulated other comprehensive loss	1,532	5,877	2,095	8,315
Other comprehensive income, net of tax	2,974	14,840	11,722	26,347
Balance at the end of the period	$ 12,739	$ 1,466	$ 12,739	$ 1,466

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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