Segment Information - Reconciliation of Income Statement Items from Reportable Segments (Parenthetical) (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	[1]	Dec. 31, 2018	[1]	Dec. 31, 2017
Segment Reporting Information [Line Items]
Other expense	$ 394	$ 281	$ 456	$ 455	$ 436	$ 527	$ 543	$ 238	$ 1,586		$ 1,744		$ 2,028	[1]
Accounting Standards Update 2017-07
Segment Reporting Information [Line Items]
Other expense													$ 2,000

[1] We adopted ASU 2017-07 on January 1, 2018, which requires retrospective adoption. As a result, we recorded the nonservice cost component of net periodic benefit cost within other expense for the years ended December 31, 2019 and 2018, and we reclassified $2.0 million from operating expenses to other expense for 2017 to conform with current period presentation.