| In millions, except per share items | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 |
| | 10-K | 10-K | 10-K | 10-K |
| Cash flows from operating activities | | | | |
| Net income (loss) | -127 | 215 | | |
| |
| Adjustments to reconcile to net cash provided by operating activities | | | | |
| Amortization of drilling contract intangible | -15 | -15 | | |
| Depreciation | 68 | 66 | | |
| Patent royalties expense | 23 | 7 | | |
| Loss on impairment | 356 | | | |
| Deferred income taxes | 5 | 18 | | |
| Other, net | 2 | | | |
| Changes in deferred revenues, net | -16 | -36 | | |
| Changes in deferred costs, net | 2 | -4 | | |
| Net cash provided by operating activities | 312 | 190 | | |
| |
| Cash flows from investing activities | | | | |
| Payments to affiliates for capital expenditures | -16 | -3 | | |
| Proceeds from affiliates for disposal of assets, net | 12 | | | |
| Net cash used in investing activities | -4 | -3 | | |
| |
| Cash flows from financing activities | | | | |
| Repayment of working capital note payable to affiliate | -43 | | | |
| Distributions of available cash to unitholders | -100 | -15 | | |
| Distributions to holder of noncontrolling interests | -101 | | | |
| Payments to repurchase common units | -1 | | | |
| Contributions for parent indemnification of lost revenues | 10 | 9 | | |
| Net cash used in financing activities | -235 | -101 | | |
| |
| Net increase in cash and cash equivalents | 73 | 86 | | |
| Cash and cash equivalents at beginning of period | 86 | | | |
| Cash and cash equivalents at end of period | 159 | 86 | | |