Supplementary Balance Sheet Information - Accumulated Other Comprehensive Income (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 2,099,920
Ending Balance	2,356,760
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	23,250
Tax Effect	2,739
Net-of-Tax Amount	20,511
Ending Balance	(44,971)
Unrealized gain (loss) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	9,862
Pretax Amount	(4,900)
Tax Effect	(1,734)
Net-of-Tax Amount	(3,166)
Ending Balance	6,696
Change in AOCI related to postretirement healthcare plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(538)
Pretax Amount	(695)
Tax Effect	(250)
Net-of-Tax Amount	(445)
Ending Balance	(983)
Accumulated Other Comprehensive Income (Loss) (OCI)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(56,158)
Pretax Amount	17,655
Tax Effect	755
Net-of-Tax Amount	16,900
Ending Balance	$ (39,258)