Accumulated Other Comprehensive Income (Loss) - Schedule of Amounts Reclassified out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses (gains) (recorded in interest and other finance expense, net)									$ 0	$ 0	$ (9,687)
Total before tax	$ 25,533	$ 31,886	$ 33,904	$ 28,256	$ 21,379	$ 35,653	$ 73,680	$ 36,951	119,579	167,663	84,049
Tax impact									(33,216)	(46,944)	(19,736)
Total after tax	$ 18,965	$ 24,253	$ 24,748	$ 18,954	$ 15,658	$ 25,817	$ 53,081	$ 26,754	86,920	121,310	64,860
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax									0	0	9,687
Tax impact									0	0	(3,131)
Total after tax									0	0	6,556
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses (gains) (recorded in interest and other finance expense, net)									$ 0	$ 0	$ 9,687