Note 20—Supplemental Cash Flow Information

Net cash provided by operating activities attributable to the net change in operating assets and liabilities were composed of the following (in millions):

	Years ended December 31,
	2013			2012			2011
Changes in operating assets and liabilities
Decrease (increase) in accounts receivable	$	58		$	(139	)	$	(174	)
Increase in other current assets	(152		)	(73		)	(73		)
Decrease in other assets	87			12			26
Increase (decrease) in accounts payable and other current liabilities	(625		)	931			978
Decrease in other long-term liabilities	(33		)	(63		)	(34		)
Change in income taxes receivable / payable, net	(151		)	(156		)	80
	$	(816	)	$	512		$	803

Additional cash flow information was as follows (in millions):

	Years ended December 31,
	2013		2012		2011
Certain cash operating activities
Cash payments for interest	$	669	$	719	$	501
Cash payments for income taxes	457		347		338

Non-cash investing and financing activities
Capital expenditures, accrued at end of period (a)	$	167	$	123	$	62
Issuance of shares in exchange for noncontrolling interest (b)	—		367		—
Non-cash proceeds received for the sale of assets (c)	—		194		—

(a) These amounts represent additions to property and equipment for which we had accrued a corresponding liability in accounts payable.

(b) On May 31, 2012, we issued 8.7 million shares to Quantum in a non-cash exchange for its interest in TPDI. See Note 16—Redeemable Noncontrolling Interest.

(c) During the year ended December 31, 2012, we completed the sale of 38 drilling units to Shelf Drilling. In connection with the sale transactions, we received net cash proceeds of $568 million and non-cash proceeds in the form of preference shares with an aggregate stated value of $195 million. We recognized the preference shares at their estimated fair value measured at the time of the sale, in the aggregate amount of $194 million, including the fair value associated with the embedded derivatives. See Note 7—Discontinued Operations.