Basis of Presentation Narrative (Details) - USD ($) $ in Thousands			6 Months Ended
		Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effects	[1]		$ 0
Decrease in net cash flows used in investing activities			217,199	$ 656,240
Increase in net cash provided by operating activities			$ 134,834	87,689
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effects		$ 7,100
Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in net cash flows used in investing activities				12,700
Increase in net cash provided by operating activities				$ 12,700

[1] Result of adoption of ASU 2018-02, See Note 1 to Consolidated Financial Statements for further details.