Other Fair Value Information (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term borrowings	$ 439,140	$ 525,842
Long-term debt	8,084,886	7,380,443
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and loans receivable	951,289	962,938
Short-term borrowings	411,096	525,842
Long-term debt	7,692,079	7,131,587
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and loans receivable	943,707	958,377
Short-term borrowings	411,096	525,842
Long-term debt	$ 8,051,953	$ 7,221,459