Summary of Significant Accounting Policies (Schedule of New Accounting Pronouncements) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Assets, Current	$ 1,963,411	$ 1,883,508	$ 1,870,004
Total assets	5,278,563	5,052,884	5,032,985
Liabilities, Current	797,421	744,937	744,102
Liabilities	$ 4,633,797	4,657,551	4,650,436
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Assets, Current			1,879,850
Total assets			5,032,985
Liabilities, Current			744,102
Liabilities			$ 4,650,436
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Assets, Current		3,658
Total assets		19,899
Liabilities, Current		835
Liabilities		$ 7,115