Financial Instruments (Credit Facility) (Details)	12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2015 USD ($)	Nov. 09, 2015 USD ($)	Nov. 02, 2015	Dec. 31, 2014 USD ($)
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 79,000,000
Revolving credit facility, minimum interest coverage ratio	3.50			3.50
Borrowings outstanding		0			$ 0
Long-term borrowings outstanding		0			3,000,000
Short-term borrowings outstanding		5,000,000
Commercial paper issued under program		0			$ 0
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility, term	5 years
Revolving credit facility, current borrowing capacity	$ 1,000,000,000.0		$ 21,000,000
Line of credit facility, maximum borrowing capacity	$ 1,500,000,000.0
Revolving credit facility, covenant compliance ratio, 2013	4.35
Revolving credit facility, covenant compliance ratio, 2014	3.95
Revolving credit facility, covenant compliance ratio, 2015	3.50
Revolving credit facility, covenant compliance ratio, 2016 and thereafter	3.00			4.25
Borrowings outstanding		$ 4,000,000