Other Fair Value Information (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term borrowings	$ 422,924	$ 525,842
Long-term debt	8,198,419	7,380,443
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and loans receivable	970,810	962,938
Short-term borrowings	422,924	525,842
Long-term debt	7,888,362	7,131,587
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and loans receivable	963,311	958,377
Short-term borrowings	422,924	525,842
Long-term debt	$ 8,133,128	$ 7,221,459