Other Comprehensive Income/(Loss) (Details) - USD ($)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Pre-Tax Amount
Other Comprehensive Income/(Loss), Pre-Tax Amount		$ 22,033,000	$ 7,851,000
Tax (Expense) Benefit
Other Comprehensive Income/(Loss), Tax (Expense) Benefit		(4,691,000)	(1,675,000)
Net of Tax Amount
Other Comprehensive Income/(Loss), Net of Tax Amount		17,342,000	6,176,000
Accumulated Net Investment Gain (Loss) Attributable to Parent
Pre-Tax Amount
Change in net unrealized gains/(losses) on debt securities available-for-sale	[1]	21,568,000	7,398,000
Tax (Expense) Benefit
Change in net unrealized gains/(losses) on debt securities available-for-sale	[1]	(4,592,000)	(1,578,000)
Net of Tax Amount
Change in net unrealized gains/(losses) on debt securities available-for-sale	[1]	16,976,000	5,820,000
Reclassifications	[1]	0	0
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Pre-Tax Amount
Other Comprehensive Income/(Loss), Pre-Tax Amount		465,000	453,000
Tax (Expense) Benefit
Other Comprehensive Income/(Loss), Tax (Expense) Benefit		(99,000)	(97,000)
Net of Tax Amount
Other Comprehensive Income/(Loss), Net of Tax Amount		$ 366,000	$ 356,000

[1] Reclassification adjustments are comprised of realized security gains or losses. The realized gains or losses have been reclassified out of accumulated other comprehensive income/(loss) and have affected certain lines in the Consolidated Statements of Comprehensive Income as follows: the pre-tax amount is included in securities gains/losses-net, the tax expense amount is included in the provision for income taxes and the net of tax amount is included in net income. There were no reclassification adjustments for the three months ended March 31, 2020 or 2019.