Debt - Carrying Values of Debt Instruments (Details) - USD ($)	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Principal	$ 7,617,600,000	$ 7,123,900,000
Adjustments	(56,600,000)	(62,700,000)
Carrying Value	7,561,000,000	7,061,200,000
Less: current portion	(5,400,000)	(10,400,000)
Long-term portion	$ 7,555,600,000	7,050,800,000
Credit facilities: Uncommitted Facility [Member]
Debt Instrument [Line Items]
Interest Rate	Variable
Principal	$ 0	0
Adjustments	0	0
Carrying Value	$ 0	0
Credit facilities: Puerto Rico Uncommitted Facility [Member]
Debt Instrument [Line Items]
Interest Rate	Variable
Principal	$ 0	0
Adjustments	0	0
Carrying Value	$ 0	0
Credit facilities: May 2017 [Member]
Debt Instrument [Line Items]
Interest Rate	Variable
Principal	$ 0	0
Adjustments	0	0
Carrying Value	$ 0	0
Credit facilities: June 2019 [Member]
Debt Instrument [Line Items]
Interest Rate	Variable
Principal	$ 0	0
Adjustments	0	0
Carrying Value	$ 0	0
Senior notes: May 2018 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	3.80%
Principal	$ 700,000,000	700,000,000
Adjustments	(100,000)	(100,000)
Carrying Value	$ 699,900,000	699,900,000
Senior notes: September 2019 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	5.50%
Principal	$ 650,000,000	650,000,000
Adjustments	(2,100,000)	(2,500,000)
Carrying Value	$ 647,900,000	647,500,000
Senior notes: March 2020 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	5.00%
Principal	$ 850,000,000	850,000,000
Adjustments	(100,000)	(100,000)
Carrying Value	$ 849,900,000	849,900,000
Senior notes: November 2021 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	5.25%
Principal	$ 600,000,000	600,000,000
Adjustments	0	0
Carrying Value	$ 600,000,000	600,000,000
Senior notes: June 2022 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	3.55%
Principal	$ 850,000,000	850,000,000
Adjustments	(1,600,000)	(1,800,000)
Carrying Value	$ 848,400,000	848,200,000
Senior notes: May 2023 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	4.75%
Principal	$ 550,000,000	550,000,000
Adjustments	17,900,000	11,500,000
Carrying Value	$ 567,900,000	561,500,000
Senior notes: March 2025 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	3.20%
Principal	$ 500,000,000	0
Adjustments	(2,000,000)	0
Carrying Value	$ 498,000,000	0
Senior notes: March 2035 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	6.086%
Principal	$ 275,700,000.0	275,700,000.0
Adjustments	(23,500,000)	(23,900,000)
Carrying Value	$ 252,200,000	251,800,000
Senior notes: March 2040 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	6.20%
Principal	$ 650,000,000	650,000,000
Adjustments	(500,000)	(500,000)
Carrying Value	$ 649,500,000	649,500,000
Senior notes: May 2041 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	5.70%
Principal	$ 600,000,000	600,000,000
Adjustments	(3,200,000)	(3,200,000)
Carrying Value	$ 596,800,000	596,800,000
Debentures: May 2021 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	9.25%
Principal	$ 35,300,000.0	35,300,000.0
Adjustments	(1,400,000)	(1,600,000)
Carrying Value	$ 33,900,000	33,700,000
Debentures: September 2035 [Member]
Debt Instrument [Line Items]
Interest rate (in percentage)	7.40%
Principal	$ 165,200,000.0	165,300,000.0
Adjustments	(40,000,000)	(40,500,000)
Carrying Value	$ 125,200,000	124,800,000
Tax-exempt: 2019 - 2044 [Member]
Debt Instrument [Line Items]
Interest Rate, minimum (in percentage)	0.43%
Interest Rate, maximum (in percentage)	5.625%
Principal	$ 1,079,100,000.0	1,083,800,000.0
Adjustments	0	0
Carrying Value	$ 1,079,100,000	1,083,800,000
Other: 2015 - 2046 [Member]
Debt Instrument [Line Items]
Interest Rate, minimum (in percentage)	4.00%
Interest Rate, maximum (in percentage)	12.203%
Principal	$ 112,300,000.0	113,800,000.0
Adjustments	0	0
Carrying Value	$ 112,300,000	$ 113,800,000