Agreement of Limited Partnership (Details) (USD $) | 3 Months Ended | 12 Months Ended | 1 Months Ended |
In Millions, except Per Share data, unless otherwise specified | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Feb. 27, 2015 |
Agreement of limited partnership | | | | | | | | | | | | |
Payments of distributions to affiliates | | | | | | | | | ($304.10) | ($465.20) | ($558.30) | |
Available cash received from operating partnership (as a percent) | | | | | | | | | 99.00% | | | |
Total distributions declared | 49.4 | 98.6 | 95 | 61.1 | 58.4 | 132.2 | 156.7 | 117.9 | | | | |
Number of average trading days' closing prices used to determine the purchase price of outstanding units of non-affiliates | | | | | | | | | 20 days | | | |
Number of days before the purchase announcement is made, as a basis for determining the purchase price of outstanding units of non-affiliates | | | | | | | | | 5 days | | | |
Minimum Quarterly Distributions | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Target Limit | | | | | | | | | 0.605 | | | |
Target Increment | | | | | | | | | 0.605 | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 100.00% | | | |
First Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Target Limit | | | | | | | | | 0.715 | | | |
Target Increment | | | | | | | | | 0.11 | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 100.00% | | | |
Second Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Target Limit | | | | | | | | | 0.825 | | | |
Target Increment | | | | | | | | | 0.11 | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 100.00% | | | |
Third Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Target Limit | | | | | | | | | 1.045 | | | |
Target Increment | | | | | | | | | 0.22 | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 100.00% | | | |
Final Target and Beyond | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Target Increment | | | | | | | | | 0 | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 100.00% | | | |
Final Target and Beyond | Minimum | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Target Limit | | | | | | | | | 1.045 | | | |
Common and Class B Common Units | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Cash distribution made, excluding when cumulative distribution is specified, (as a percent) | | | | | | | | | 99.98% | | | |
Common Units | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Declared partnership distributions | 33 | 57.5 | 55.8 | 38.8 | 37.4 | 74.4 | 86.6 | 67.2 | | | | |
Cash distribution declared per common limited partnership unit (in dollars per unit) | $1.78 | $3.11 | $3.01 | $2.10 | $2.02 | $4.02 | $4.68 | $3.63 | | | | |
Common Units | Minimum Quarterly Distributions | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 98.99% | | | |
Common Units | First Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 98.99% | | | |
Common Units | Second Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 85.86% | | | |
Common Units | Third Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 75.76% | | | |
Common Units | Final Target and Beyond | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 50.51% | | | |
Class B Common Units | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Declared partnership distributions | 0.4 | 1 | 0.9 | 0.6 | 0.6 | 1.3 | 1.5 | 1.2 | | | | |
Cash distribution declared per common limited partnership unit (in dollars per unit) | $2.61 | $5.22 | $5.03 | $3.24 | $3.09 | $7 | $8.31 | $6.25 | | | | |
Class B Common Units | Minimum Quarterly Distributions | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 0.99% | | | |
Class B Common Units | First Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 0.99% | | | |
Class B Common Units | Second Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 0.99% | | | |
Class B Common Units | Third Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 0.99% | | | |
Class B Common Units | Final Target and Beyond | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 0.99% | | | |
Subsequent Event | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Cash distribution declared per common limited partnership unit (in dollars per unit) | | | | | | | | | | | | $2.50 |
General Partner | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Available cash distributed from operating partnership to General Partner (as a percent) | | | | | | | | | 1.00% | | | |
Cash distribution made, excluding when cumulative distribution is specified, (as a percent) | | | | | | | | | 0.03% | | | |
Partnership equity interest (as a percent) | 1.00% | | | | | | | | 1.00% | | | |
Declared partnership distributions | $16 | $40.10 | $38.30 | $21.70 | $20.40 | $56.50 | $68.60 | $49.50 | | | | |
Percentage of outstanding units owned by the General Partner and its affiliates | 75.30% | | | | | | | | 75.30% | | | |
Period within which highest price is paid for any unit preceding the date the purchase is announced used to determine the purchase price of outstanding units of non-affiliates | | | | | | | | | 90 days | | | |
General Partner | Minimum | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Percentage of ownership of non-affiliates of the General Partner allowing majority owner to acquire outstanding units held by non-affiliated persons | | | | | | | | | 25.00% | | | |
Notice period for making decision to purchase the outstanding units | | | | | | | | | 30 days | | | |
General Partner | Maximum | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Notice period for making decision to purchase the outstanding units | | | | | | | | | 60 days | | | |
General Partner | Minimum Quarterly Distributions | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 0.03% | | | |
General Partner | First Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 0.03% | | | |
General Partner | Second Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 13.16% | | | |
General Partner | Third Target | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 23.26% | | | |
General Partner | Final Target and Beyond | | | | | | | | | | | | |
Agreement of limited partnership | | | | | | | | | | | | |
Income and distribution allocation (as a percent) | | | | | | | | | 48.51% | | | |