Supplementary Balance Sheet Information - Accumulated Other Comprehensive Income (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 2,099,920
Ending Balance	2,264,536
Reclassifications of AOCI	0
Foreign currency translation adjustments and transfers from noncontrolling interests
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(65,482)
Pretax Amount	14,266
Tax Effect	1,700
Net-of-Tax Amount	12,566
Ending Balance	(52,916)
Unrealized gain (loss) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	9,862
Pretax Amount	(2,780)
Tax Effect	(987)
Net-of-Tax Amount	(1,793)
Ending Balance	8,069
Change in AOCI related to postretirement healthcare plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(538)
Pretax Amount	388
Tax Effect	141
Net-of-Tax Amount	247
Ending Balance	(291)
Accumulated Other Comprehensive Income (Loss) (OCI)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(56,158)
Pretax Amount	11,874
Tax Effect	854
Net-of-Tax Amount	11,020
Ending Balance	$ (45,138)