Financing Arrangements (Details) - USD ($)		12 Months Ended
	Feb. 15, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Capital lease duration		25 years
Capital lease payment duration		15 years
Capital lease expiration date		Jun. 30, 2029
Capital lease obligations, current		$ 18,881,000
Capital lease obligations, noncurrent		209,817,000
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity		$ 2,000,000,000
Credit facility, maturity date		May 01, 2017
Line of credit facility fee		0.25%
Amount outstanding		$ 600,000,000
Committed Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Credit facility interest rate above LIBOR	1.45%
Uncommitted Credit Facilities [Member]
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity		300,000,000
Current borrowing capacity		$ 0