CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 105,333	$ 107,498	$ 55,165
Other comprehensive income (loss), before tax expense (benefit):
Unrealized holding gains on securities arising during the period	20,625	2,783	7,023
Less: reclassification adjustment for gains on securities included in net income	(22)	(8,102)	(5,040)
Unrealized holding gains (losses) on derivatives arising during the period	935	326	(901)
Reclassification adjustment for losses on derivatives included in net income	0	10	119
Unrealized (losses) gains for postretirement obligations:
Net (loss) gain	(121)	144	94
Total other comprehensive income (loss), before income tax expense (benefit)	21,417	(4,839)	1,295
Income tax expense (benefit) related to items of other comprehensive income (loss)	4,497	(1,015)	441
Comprehensive Income	$ 122,253	$ 103,674	$ 56,019