Debt (Consolidated Debt) (Details) - USD ($)		Sep. 30, 2016	Feb. 29, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long term debt		$ 4,323,522,000		$ 3,439,622,000
Weighted-Average Interest Rate	[1]	4.90%
Debt Instrument, Face Amount		$ 4,300,000,000.0		3,400,000,000.0
Current portion of long-term debt, net		250,020,000		250,335,000
Long-term debt, net	[2]	4,073,502,000		3,189,287,000
Senior Notes [Member] | Five Point Six Five Percentage Notes Due Two Thousand Sixteen [Member]
Debt Instrument [Line Items]
Long term debt	[3]	$ 250,020,000		250,208,000
Weighted-Average Interest Rate	[1]	5.70%
Debt Instrument, Face Amount		$ 250,000,000.0		$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage		5.65%		5.65%
Senior Notes [Member] | 6.40% Notes Due 2018 [Member]
Debt Instrument [Line Items]
Long term debt		$ 253,298,000		$ 254,694,000
Weighted-Average Interest Rate	[1]	5.50%
Debt Instrument, Face Amount		$ 250,000,000.0		$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage		6.40%		6.40%
Senior Notes [Member] | 6.55% Notes Due 2019 [Member]
Debt Instrument [Line Items]
Long term debt		$ 560,042,000		$ 562,600,000
Weighted-Average Interest Rate	[1]	5.70%
Debt Instrument, Face Amount		$ 550,000,000.0		$ 550,000,000
Debt Instrument, Interest Rate, Stated Percentage		6.55%		6.55%
Senior Notes [Member] | 4.25% Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long term debt		$ 552,620,000		$ 553,002,000
Weighted-Average Interest Rate	[1]	4.10%
Debt Instrument, Face Amount		$ 550,000,000.0		$ 550,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.25%		4.25%
Senior Notes [Member] | 3.20% Notes Due 2025 [Member]
Debt Instrument [Line Items]
Long term debt		$ 247,967,000		$ 247,788,000
Weighted-Average Interest Rate	[1]	3.20%
Debt Instrument, Face Amount		$ 250,000,000.0		$ 250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage		3.20%		3.20%
Senior Notes [Member] | Five Point Zero Percentage Notes Due Two Thousand Twenty Six [Member]
Debt Instrument [Line Items]
Long term debt		$ 644,129,000		$ 0
Weighted-Average Interest Rate	[1],[4]	5.10%
Debt Instrument, Face Amount		$ 650,000,000.0	$ 650,000,000.0	$ 0
Debt Instrument, Interest Rate, Stated Percentage		5.00%	5.00%	0.00%
Senior Notes [Member] | 6.40% Notes Due 2037 [Member]
Debt Instrument [Line Items]
Long term debt		$ 247,312,000		$ 247,230,000
Weighted-Average Interest Rate	[1]	6.40%
Debt Instrument, Face Amount		$ 250,000,000.0		$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage		6.40%		6.40%
Senior Notes [Member] | 4.20% Notes Due 2042 [Member]
Debt Instrument [Line Items]
Long term debt		$ 246,230,000		$ 246,142,000
Weighted-Average Interest Rate	[1]	4.30%
Debt Instrument, Face Amount		$ 250,000,000.0		$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.20%		4.20%
Senior Notes [Member] | 5.15% Notes Due 2043 [Member]
Debt Instrument [Line Items]
Long term debt		$ 550,885,000		$ 550,819,000
Weighted-Average Interest Rate	[1]	5.10%
Debt Instrument, Face Amount		$ 550,000,000.0		$ 550,000,000.0
Debt Instrument, Interest Rate, Stated Percentage		5.15%		5.15%
Senior Notes [Member] | 4.20% Notes Due 2045 [Member]
Debt Instrument [Line Items]
Long term debt		$ 247,408,000		$ 247,338,000
Weighted-Average Interest Rate	[1]	4.70%
Debt Instrument, Face Amount		$ 250,000,000.0		$ 250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage		4.20%		4.20%
Senior Notes [Member] | Four Point Two Five Percentage Notes Due Two Thousand Forty Six [Member]
Debt Instrument [Line Items]
Long term debt		$ 488,731,000		$ 0
Weighted-Average Interest Rate	[1]	4.80%
Debt Instrument, Face Amount		$ 500,000,000.0		$ 0
Debt Instrument, Interest Rate, Stated Percentage		4.25%		0.00%
Commercial Paper [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long term debt		$ 34,880,000		$ 279,801,000
Weighted-Average Interest Rate	[1],[4]	0.80%

[1] Weighted-average interest rate includes the amortization/accretion of discounts, premiums and gains/losses realized on historical cash flow and fair value hedges recognized as interest expense.

[2] Long-term debt is presented net of unamortized debt issuance costs of $18.7 million and $27.4 million at December 31, 2015 and September 30, 2016, respectively.

[3] These borrowings will mature in October 2016 and are reflected in current debt on our consolidated balance sheets at December 31, 2015 and September 30, 2016.

[4] These borrowings were outstanding for only a portion of the nine-month period ending September 30, 2016. The weighted-average interest rate for these borrowings was calculated based on the number of days the borrowings were outstanding during the noted period.