Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Federal statutory income tax rate, percent			21.00%	35.00%
TCJA, provisional information, income tax expense (benefit)		$ 79,000
TCJA, provisional information, transition tax		32,000
TCJA, provisional information, benefit related to remeasurement of deferred tax assets		47,000
TCJA, income tax expense (benefit)			$ 34,000
Rate Change / Transition Tax			(71,516)	$ 79,077	$ 0
U.S. Minimum Tax on Foreign Entities			45,000
TCJA, benefit related to remeasurement of deferred tax assets			27,000
Valuation allowance		49,431	124,996	49,431
Foreign tax credits		102,242	218,026	102,242
Unrecognized tax benefits		42,902	47,534	42,902	$ 19,739
Reduction in provision for income taxes due to impact of effective tax rate		$ 38,000	44,000	$ 38,000
Discrete tax benefit resulting from settlement	$ 7,000
Federal tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount			248,000
State tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount			193,000
Foreign tax authority
Operating Loss Carryforwards [Line Items]
Foreign tax credits			$ 99,000