Accumulated Other Comprehensive Income (Loss) - Changes in components of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period			$ (24,881)
Other comprehensive income (loss), net of tax	$ 1,404	$ (8,438)	27,751	$ (31,135)
Balance at the end of the period	2,870	(44,509)	2,870	(44,509)
Benefit Plans
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(297)	(7,456)	(6,450)	(5,998)
Amounts reclassified from accumulated other comprehensive income (loss)		151	6,153	453
Other comprehensive income (loss), net of tax		151	6,153	453
AOCI reclassification to retained earnings from adoption of ASU 2018-02				(1,760)
Balance at the end of the period	(297)	(7,305)	(297)	(7,305)
Unrealized Gains and Losses on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	12,944	(28,526)	(18,394)	(4,278)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	5,824	(8,624)	34,732	(32,224)
Amounts reclassified from accumulated other comprehensive income (loss)	(341)	9	2,089	508
Other comprehensive income (loss), net of tax	5,483	(8,615)	36,821	(31,716)
AOCI reclassification to retained earnings from adoption of ASU 2018-02				(1,147)
Balance at the end of the period	18,427	(37,141)	18,427	(37,141)
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	(11,181)	(89)	(37)	(151)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(3,891)	(1)	(14,766)	34
Amounts reclassified from accumulated other comprehensive income (loss)	(188)	27	(457)	94
Other comprehensive income (loss), net of tax	(4,079)	26	(15,223)	128
AOCI reclassification to retained earnings from adoption of ASU 2018-02				(40)
Balance at the end of the period	(15,260)	(63)	(15,260)	(63)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period	1,466	(36,071)	(24,881)	(10,427)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1,933	(8,625)	19,966	(32,190)
Amounts reclassified from accumulated other comprehensive income (loss)	(529)	187	7,785	1,055
Other comprehensive income (loss), net of tax	1,404	(8,438)	27,751	(31,135)
AOCI reclassification to retained earnings from adoption of ASU 2018-02				(2,947)
Balance at the end of the period	$ 2,870	$ (44,509)	$ 2,870	$ (44,509)