Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Balance	$ 549,683	$ 579,672	$ 559,559	$ 549,464	$ 579,672	$ 549,464
Total other comprehensive income (loss) , net of tax	8,918	(22,633)	(74)	2,210	(13,715)	2,136
Balance	571,921	549,683	565,390	559,559	571,921	565,390
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(14,159)	(3,982)	(10,029)	(15,649)	(3,982)	(15,649)
Other comprehensive income before reclassifications, net of tax	11,414		6,204		1,212	11,824
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	37		10		62	10
Total other comprehensive income (loss) , net of tax	11,451		6,214		1,274	11,834
Balance	(2,708)	(14,159)	(3,815)	(10,029)	(2,708)	(3,815)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Balance	(19,468)	(5,863)	199	3,704	(5,863)	3,704
Other comprehensive income before reclassifications, net of tax	(2,404)		(5,884)		(16,152)	(9,250)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	399		(447)		542	(586)
Total other comprehensive income (loss) , net of tax	(2,005)		(6,331)		(15,610)	(9,836)
Balance	(21,473)	(19,468)	(6,132)	199	(21,473)	(6,132)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(930)	(983)	(1,666)	(1,673)	(983)	(1,673)
Other comprehensive income before reclassifications, net of tax	0		0		0	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	52		8		105	15
Total other comprehensive income (loss) , net of tax	52		8		105	15
Balance	(878)	(930)	(1,658)	(1,666)	(878)	(1,658)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Balance	2,117	1,021	954	866	1,021	866
Other comprehensive income before reclassifications, net of tax	(580)		35		516	123
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0		0		0	0
Total other comprehensive income (loss) , net of tax	(580)		35		516	123
Balance	1,537	2,117	989	954	1,537	989
AOCI Attributable to Parent [Member]
Balance	(32,440)	(9,807)	(10,542)	(12,752)	(9,807)	(12,752)
Other comprehensive income before reclassifications, net of tax	8,430		355		(14,424)	2,697
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	488		(429)		709	(561)
Total other comprehensive income (loss) , net of tax	8,918	(22,633)	(74)	2,210	(13,715)	2,136
Balance	$ (23,522)	$ (32,440)	$ (10,616)	$ (10,542)	$ (23,522)	$ (10,616)