Debt - Narrative (Details) - USD ($)
|
3 Months Ended |
9 Months Ended |
12 Months Ended |
|
|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
Dec. 31, 2015 |
May 31, 2016 |
Jun. 30, 2014 |
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Aggregate amount of premiums on senior notes |
$ 148,100,000
|
|
|
|
|
|
|
| Early tender consideration for purchase of senior notes |
28,700,000
|
|
|
|
|
|
|
| Payments of debt extinguishment costs |
1,600,000
|
|
$ 176,900,000
|
$ 0
|
|
|
|
| Write off of deferred debt issuance costs and unamortized discounts |
17,800,000
|
|
17,800,000
|
|
|
|
|
| Non-cash interest expense |
7,200,000
|
|
7,200,000
|
|
|
|
|
| Balance availability under Letters of Credit Facilities |
1,513,500,000
|
|
1,513,500,000
|
|
$ 1,727,700,000
|
|
|
| Line of credit facility amount outstanding |
210,000,000
|
|
210,000,000
|
|
0
|
|
|
| Letters of credit utilizing availability under Credit Facilities |
508,000,000
|
|
508,000,000
|
|
503,300,000
|
|
|
| Long-term debt |
7,745,300,000
|
|
7,745,300,000
|
|
7,532,900,000
|
|
|
| Combined Aggregate Principal of Senior Notes and Debentures Purchased |
575,400,000.0
|
|
|
|
|
|
|
| Debt instrument, face amount |
7,820,800,000.0
|
|
$ 7,820,800,000.0
|
|
7,635,800,000.0
|
|
|
| Percentage of tax exempt financings |
|
|
90.00%
|
|
|
|
|
| Capital lease liabilities |
|
|
|
|
111,500,000
|
|
|
| Interest rate swaps at fair value |
27,900,000
|
|
$ 27,900,000
|
|
$ 16,500,000
|
|
|
| Net interest income related to net swap settlements |
1,500,000
|
$ 1,900,000
|
4,900,000
|
5,700,000
|
|
|
|
| Gain (loss) on the change in fair value of the hedged senior notes |
4,500,000
|
(9,200,000)
|
(9,600,000)
|
(6,300,000)
|
|
|
|
| Gain (loss) on the related interest rate swaps |
(3,800,000)
|
9,600,000
|
$ 11,400,000
|
7,300,000
|
|
|
|
| Minimum |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Range of capital lease liabilities matured |
|
|
2016
|
|
2016
|
|
|
| Maximum |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Range of capital lease liabilities matured |
|
|
2046
|
|
2046
|
|
|
| Interest Rate Swap |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Notional value of swap agreements |
300,000,000
|
|
$ 300,000,000
|
|
|
|
|
| Expected amortization of yield adjustment on senior notes |
|
|
1,600,000
|
|
|
|
|
| Interest rate locks |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Notional value of swap agreements |
$ 525,000,000
|
|
$ 525,000,000
|
|
|
|
|
| Derivative, interest rate floor |
1.90%
|
|
1.90%
|
|
|
|
|
| Derivative, interest rate cap |
2.2795%
|
|
2.2795%
|
|
|
|
|
| Accumulated and other comprehensive income, net of tax |
$ 12,200,000
|
|
$ 12,200,000
|
|
|
|
|
| Effective portion of interest rate locks amortized as an adjustment to interest expense |
7,800,000
|
$ 700,000
|
9,100,000
|
$ 2,000,000
|
|
|
|
| Interest rate locks | Long-term Debt |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Interest rate locks fair value |
20,300,000
|
|
20,300,000
|
|
|
|
|
| Line Of Credit Due May 2021 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Revolving credit facility maximum borrowing capacity |
|
|
|
|
|
$ 1,000,000,000
|
|
| Aggregate additional borrowings through increased commitments from existing lenders |
|
|
500,000,000
|
|
|
|
|
| Line Of Credit Due May 2017 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Revolving credit facility maximum borrowing capacity |
1,250,000,000.00
|
|
1,250,000,000.00
|
|
|
|
|
| Reduction in maximum borrowing capacity |
|
|
|
|
|
|
$ 1,000,000,000
|
| Line Of Credit Due June 2019 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Line of credit facility, increase |
|
|
500,000,000
|
|
|
|
|
| Long-term debt |
70,000,000
|
|
70,000,000
|
|
$ 0
|
|
|
| Debt instrument, face amount |
70,000,000
|
|
70,000,000
|
|
0
|
|
|
| Uncommitted Credit Facility |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Revolving credit facility maximum borrowing capacity |
135,000,000
|
|
135,000,000
|
|
|
|
|
| Uncommitted Revolver |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
73,000,000
|
|
73,000,000
|
|
19,000,000
|
|
|
| Debt instrument, face amount |
73,000,000
|
|
73,000,000
|
|
19,000,000.0
|
|
|
| Senior Notes 6.20% Due March 2040 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
$ 395,900,000
|
|
$ 395,900,000
|
|
643,400,000
|
|
|
| Interest rate (in percentage) |
6.20%
|
|
6.20%
|
|
|
|
|
| Debt instrument, face amount |
$ 399,900,000.0
|
|
$ 399,900,000.0
|
|
650,000,000
|
|
|
| Senior Notes Due May 2041 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
$ 380,100,000
|
|
$ 380,100,000
|
|
591,100,000
|
|
|
| Interest rate (in percentage) |
5.70%
|
|
5.70%
|
|
|
|
|
| Debt instrument, face amount |
$ 385,700,000.0
|
|
$ 385,700,000.0
|
|
600,000,000
|
|
|
| Debentures $360.0 million 7.400% Due September 2035 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
$ 112,800,000
|
|
$ 112,800,000
|
|
125,300,000
|
|
|
| Interest rate (in percentage) |
7.40%
|
|
7.40%
|
|
|
|
|
| Debt instrument, face amount |
$ 148,100,000.0
|
|
$ 148,100,000.0
|
|
165,200,000.0
|
|
|
| Senior Notes Due March 2035 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
$ 166,300,000
|
|
$ 166,300,000
|
|
251,800,000
|
|
|
| Interest rate (in percentage) |
6.086%
|
|
6.086%
|
|
|
|
|
| Debt instrument, face amount |
$ 181,900,000.0
|
|
$ 181,900,000.0
|
|
275,700,000.0
|
|
|
| Senior Notes $500.0 million 2.90% due 2026 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Interest rate (in percentage) |
2.90%
|
|
2.90%
|
|
|
|
|
| Debt instrument, face amount |
$ 500,000,000
|
|
$ 500,000,000
|
|
|
|
|
| Senior Notes $500.0 million 3.20% Due March 2025 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
$ 494,400,000
|
|
$ 494,400,000
|
|
494,000,000
|
|
|
| Interest rate (in percentage) |
3.20%
|
|
3.20%
|
|
|
|
|
| Debt instrument, face amount |
$ 500,000,000
|
|
$ 500,000,000
|
|
$ 500,000,000
|
|
|
| Senior Notes $500.0 million 3.20% Due March 2025 | Interest rate locks |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Interest rate (in percentage) |
|
|
|
|
3.20%
|
|
|
| Accumulated and other comprehensive income, net of tax |
13,800,000
|
|
13,800,000
|
|
$ 19,400,000
|
|
|
| Tax Exempt Bonds And Other Tax Exempt Financings |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
1,072,600,000
|
|
1,072,600,000
|
|
1,072,100,000
|
|
|
| Debt instrument, face amount |
$ 1,079,100,000.0
|
|
$ 1,079,100,000.0
|
|
1,079,100,000.0
|
|
|
| Tax Exempt Bonds And Other Tax Exempt Financings | Minimum |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Interest rate (in percentage) |
0.50%
|
|
0.50%
|
|
|
|
|
| Tax Exempt Bonds And Other Tax Exempt Financings | Maximum |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Interest rate (in percentage) |
5.625%
|
|
5.625%
|
|
|
|
|
| Senior Notes $550.0 million 4.750% Due May 2023 |
|
|
|
|
|
|
|
| Debt Instrument [Line Items] |
|
|
|
|
|
|
|
| Long-term debt |
$ 569,400,000
|
|
$ 569,400,000
|
|
559,400,000
|
|
|
| Interest rate (in percentage) |
4.75%
|
|
4.75%
|
|
|
|
|
| Debt instrument, face amount |
$ 550,000,000
|
|
$ 550,000,000
|
|
$ 550,000,000
|
|
|