Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss 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	Jan. 01, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ 644,729			$ 644,729
Other Comprehensive Income (Loss), Net of Tax	$ (1,189)	(37,437)	$ 98	$ 109
Transition adjustment	(711,798)				(711,798)			$ (495,514)
Transition adjustment	(64,627)				(64,627)			$ (28,159)
Ending balance	393,704				393,704
Cumulative Effect, Period of Adoption, Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Transition adjustment		(5,300)
Transition adjustment							$ 2,200
Interest Rate Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		1,634			1,634
Losses (gains) arising during period					(40,148)
Amounts reclassified from accumulated other comprehensive loss					2,490
Net other comprehensive income					(37,658)
Ending balance	(36,024)				(36,024)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(23,916)		(21,814)	(23,916)	$ (21,814)
Losses (gains) arising during period					(1,106)
Amounts reclassified from accumulated other comprehensive loss					33	39
Income tax benefit						(2)
Net other comprehensive income					(1,073)	41
Ending balance	(24,989)		(24,480)		(24,989)	(24,480)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Transition adjustment			(2,707)			(2,707)
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(5,877)		(6,210)	(5,877)	(6,210)
Amounts reclassified from accumulated other comprehensive loss					105	166
Net other comprehensive income					105	166
Ending balance	(3,614)		(6,044)		(3,614)	(6,044)
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Transition adjustment	2,158				2,158
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(28,159)		(28,024)	(28,159)	(28,024)
Losses (gains) arising during period					(41,254)
Amounts reclassified from accumulated other comprehensive loss					2,628	205
Income tax benefit						(2)
Net other comprehensive income					(38,626)	207
Other Comprehensive Income (Loss), Net of Tax	(1,189)	$ (37,437)	98	$ 109
Ending balance	(64,627)		(30,524)		(64,627)	(30,524)
AOCI Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Transition adjustment	$ 2,158		$ (2,707)		$ 2,158	$ (2,707)