Debt (Schedule of long-term debt instruments) (Details) (USD $)	3 Months Ended			1 Months Ended		12 Months Ended				0 Months Ended	1 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Mar. 31, 2015		Dec. 31, 2021	Dec. 31, 2018	Dec. 31, 2023	Dec. 31, 2020	Apr. 30, 2015	Apr. 21, 2015	Dec. 31, 2014		Apr. 30, 2014	Nov. 30, 2009
Debt Instrument
Total debt	$ 8,075,000,000			$ 8,075,000,000								$ 8,052,000,000
Less short-term portion	(593,000,000)	[1]		(593,000,000)	[1]							(618,000,000)	[1]
Total long-term debt	7,482,000,000			7,482,000,000								7,434,000,000
Loss on repurchase/redemption of debt securities and amendment of ABL facility	2,000,000		11,000,000
5 3/4 percent Senior Secured Notes
Debt Instrument
Stated interest rate	5.75%			5.75%
8 3/8 percent Senior Subordinated Notes
Debt Instrument
Stated interest rate	8.375%			8.375%
7 3/8 percent Senior Notes
Debt Instrument
Stated interest rate	7.375%			7.375%
8 1/4 percent Senior Notes
Debt Instrument
Stated interest rate	8.25%			8.25%
Redemption notice, amount	350,000,000			350,000,000
7 5/8 percent Senior Notes
Debt Instrument
Stated interest rate	7.625%			7.625%
6 1/8 percent Senior Notes
Debt Instrument
Stated interest rate	6.125%			6.125%
4 5/8 percent Senior Notes
Debt Instrument
Stated interest rate	4.625%			4.625%
5 3/4 percent Senior Notes
Debt Instrument
Stated interest rate	5.75%			5.75%
5 1/2 percent Senior Notes
Debt Instrument
Stated interest rate	5.50%			5.50%
Credit facility | $2.5 billion ABL Facility
Debt Instrument
Current borrowing capacity under credit facility	2,300,000,000			2,300,000,000
Letters of credit outstanding	50,000,000			50,000,000
Credit facility interest rate at period end	2.50%			2.50%
Average outstanding amount	818,000,000
Weighted average interest rate, long-term	2.30%			2.30%
ABL Facility maximum month-end outstanding amount	1,300,000,000
Senior secured notes | 4 5/8 percent Senior Notes
Debt Instrument
Face amount	1,000,000,000			1,000,000,000
Proceeds from issuance of long-term debt				990,000,000
Redemption price, percentage				101.00%
Senior notes | 5 3/4 percent Senior Notes
Debt Instrument
Face amount														850,000,000
Senior notes | 5 1/2 percent Senior Notes
Debt Instrument
Face amount	800,000,000			800,000,000
Proceeds from issuance of long-term debt				792,000,000
Redemption price, percentage				101.00%
Accounts receivable facility | Accounts Receivable Securitization Facility
Debt Instrument
Current borrowing capacity under credit facility	550,000,000			550,000,000
Average outstanding amount under facility	362,000,000
Weighted average interest rate, short-term	0.80%			0.80%
A/R Securitization maximum month-end outstanding amount	544,000,000
Collateral amount	589,000,000			589,000,000
Convertible senior notes | Convertible subordinated notes—4 percent
Debt Instrument
Total debt	7,000,000	[2]		7,000,000	[2]							32,000,000	[2]
Stated interest rate	4.00%		4.00%	4.00%
Loss on repurchase/redemption of debt securities and amendment of ABL facility	1,000,000
Extinguishment of debt, amount	26,000,000
Face amount	8,000,000			8,000,000											173,000,000
Unamortized discount	1,000,000			1,000,000
Convertible, conversion price (in dollars per share)	$ 11.11			$ 11.11
URNA and subsidiaries
Debt Instrument
Total debt	8,068,000,000			8,068,000,000								8,020,000,000
URNA and subsidiaries | $2.5 billion ABL Facility
Debt Instrument
Maximum borrowing capacity	2,500,000,000.0			2,500,000,000.0
URNA and subsidiaries | Capital leases
Debt Instrument
Total debt	98,000,000			98,000,000								105,000,000
URNA and subsidiaries | Credit facility | $2.5 billion ABL Facility
Debt Instrument
Total debt	109,000,000	[3]		109,000,000	[3]							1,304,000,000	[3]
URNA and subsidiaries | Senior secured notes | 5 3/4 percent Senior Secured Notes
Debt Instrument
Total debt	750,000,000	[4]		750,000,000	[4]							750,000,000	[4]
URNA and subsidiaries | Senior secured notes | 4 5/8 percent Senior Notes
Debt Instrument
Total debt	1,000,000,000	[5]		1,000,000,000	[5]							0	[5]
URNA and subsidiaries | Senior notes | 7 3/8 percent Senior Notes
Debt Instrument
Total debt	750,000,000			750,000,000								750,000,000
URNA and subsidiaries | Senior notes | 8 1/4 percent Senior Notes
Debt Instrument
Total debt	686,000,000	[6]		686,000,000	[6]							687,000,000	[6]
URNA and subsidiaries | Senior notes | 7 5/8 percent Senior Notes
Debt Instrument
Total debt	1,325,000,000			1,325,000,000								1,325,000,000
URNA and subsidiaries | Senior notes | 6 1/8 percent Senior Notes
Debt Instrument
Total debt	950,000,000			950,000,000								951,000,000
URNA and subsidiaries | Senior notes | 5 3/4 percent Senior Notes
Debt Instrument
Total debt	850,000,000			850,000,000								850,000,000
URNA and subsidiaries | Senior notes | 5 1/2 percent Senior Notes
Debt Instrument
Total debt	800,000,000	[7]		800,000,000	[7]							0	[7]
URNA and subsidiaries | Senior subordinated notes | 8 3/8 percent Senior Subordinated Notes
Debt Instrument
Total debt	750,000,000	[4]		750,000,000	[4]							750,000,000	[4]
URNA and subsidiaries | Accounts receivable facility | Accounts Receivable Securitization Facility
Debt Instrument
Total debt	0	[8]		0	[8]							548,000,000	[8]
Forecast | Senior secured notes | 4 5/8 percent Senior Notes
Debt Instrument
Redemption price, percentage						100.00%	103.469%
Forecast | Senior notes | 5 1/2 percent Senior Notes
Debt Instrument
Redemption price, percentage								100.00%	102.75%
Interest expense, net | Forecast | 8 1/4 percent Senior Notes
Debt Instrument
Loss on repurchase/redemption of debt securities and amendment of ABL facility										15,000,000
Subsequent event | Interest expense, net | 5 3/4 percent Senior Secured Notes and 8 3/8 percent Senior Subordinated Notes
Debt Instrument
Loss on repurchase/redemption of debt securities and amendment of ABL facility											$ 106,000,000

[1] As of March 31, 2015, our short-term debt primarily reflects the current portion of the debt discussed above that was redeemed in April 2015 using availability under our accounts receivable securitization facility.

[2] The difference between the March 31, 2015 carrying value of the 4 percent Convertible Senior Notes and the $8 principal amount reflects the $1 unamortized portion of the original issue discount recognized upon issuance of the notes, which is being amortized through the maturity date of November 15, 2015. Because the 4 percent Convertible Senior Notes were redeemable at March 31, 2015, an amount equal to the $1 unamortized portion of the original issue discount is separately classified in our condensed consolidated balance sheets and referred to as “temporary equity.” During the three months ended March 31, 2015, $26 of our 4 percent Convertible Notes were redeemed. We recognized a loss of approximately $1 in interest expense, net upon redemption. The loss represented the difference between the net carrying amount and the fair value of the debt component of the notes. Based on the price of our common stock during the first quarter of 2015, holders of the 4 percent Convertible Senior Notes have the right to redeem the notes during the second quarter of 2015 at a conversion price of $11.11 per share of common stock. Since April 1, 2015 (the beginning of the second quarter), none of the 4 percent Convertible Senior Notes have been redeemed.

[3] At March 31, 2015, $2.3 billion was available under our ABL facility, net of $50 of letters of credit. The interest rate applicable to the ABL facility was 2.5 percent at March 31, 2015. During the three months ended March 31, 2015, the monthly average amount outstanding under the ABL facility was $818, and the weighted-average interest rate thereon was 2.3 percent. The maximum month-end amount outstanding under the ABL facility during the three months ended March 31, 2015 was $1.3 billion. In March 2015, the ABL facility was amended, primarily to increase the facility size and to extend the maturity date. The size of the facility was increased to $2.5 billion. All amounts borrowed under the ABL facility must be repaid on or before March 2020. In March 2015, we repaid a portion of the outstanding borrowings under the ABL facility using a portion of the net proceeds from the debt issuances described below. In April 2015, we used, or expect to use, borrowings under the ABL facility to partially fund the debt redemptions described below.

[4] In March 2015, we issued redemption notices for all of our 5 3/4 percent Senior Secured Notes and 8 3/8 percent Senior Subordinated Notes. The notes were redeemed in April 2015 using borrowings under our accounts receivable securitization and ABL facilities. Upon redemption, we recognized an aggregate loss of $106 in interest expense, net. The loss represented the difference between the net carrying amount and the total purchase price of the notes.

[5] In March 2015, URNA issued $1.0 billion aggregate principal amount of 4 5/8 percent Senior Secured Notes (the “4 5/8 percent Notes”) which are due July 15, 2023. The net proceeds from issuance were approximately $990 (after deducting offering expenses). The 4 5/8 percent Notes are guaranteed by Holdings and certain domestic subsidiaries of URNA and are secured on a second-priority basis by liens on substantially all of URNA’s and the guarantors’ assets that secure the ABL facility, subject to certain exceptions. The 4 5/8 percent Notes may be redeemed on or after July 15, 2018, at specified redemption prices that range from 103.469 percent in 2018, to 100 percent in 2021 and thereafter, plus accrued and unpaid interest, if any. The indenture governing the 4 5/8 percent Notes contains certain restrictive covenants, including, among others, limitations on (i) liens; (ii) additional indebtedness; (iii) mergers, consolidations and acquisitions; (iv) sales, transfers and other dispositions of assets; (v) loans and other investments; (vi) dividends and other distributions, stock repurchases and redemptions and other restricted payments; (vii) restrictions affecting subsidiaries; (viii) transactions with affiliates; and (ix) designations of unrestricted subsidiaries, as well as a requirement to timely file periodic reports with the SEC. The indenture also includes covenants relating to the grant of and maintenance of liens for the benefit of the notes collateral agent. Each of the restrictive covenants is subject to important exceptions and qualifications that would allow URNA and its subsidiaries to engage in these activities under certain conditions. The indenture also requires that, in the event of a change of control (as defined in the indenture), URNA must make an offer to purchase all of the then-outstanding 4 5/8 percent Notes tendered at a purchase price in cash equal to 101 percent of the principal amount thereof, plus accrued and unpaid interest, if any, thereon.

[6] In March 2015, we issued redemption notices for $350 principal amount of our 8 1/4 percent Senior Notes. We expect to redeem the notes in April 2015 using borrowings under our ABL facility. Upon redemption, we expect to recognize a loss of approximately $15 in interest expense, net. The loss represents the difference between the net carrying amount and the total purchase price of the notes.

[7] In March 2015, URNA issued $800 aggregate principal amount of 5 1/2 percent Senior Notes (the “5 1/2 percent Notes”) which are due July 15, 2025. The net proceeds from the issuance were approximately $792 (after deducting offering expenses). The 5 1/2 percent Notes are unsecured and are guaranteed by Holdings and certain domestic subsidiaries of URNA. The 5 1/2 percent Notes may be redeemed on or after July 15, 2020, at specified redemption prices that range from 102.75 percent in 2020, to 100 percent in 2023 and thereafter, plus accrued and unpaid interest, if any. The indenture governing the 5 1/2 percent Notes contains certain restrictive covenants, including, among others, limitations on (i) liens; (ii) additional indebtedness; (iii) mergers, consolidations and acquisitions; (iv) sales, transfers and other dispositions of assets; (v) loans and other investments; (vi) dividends and other distributions, stock repurchases and redemptions and other restricted payments; (vii) restrictions affecting subsidiaries; (viii) transactions with affiliates; and (ix) designations of unrestricted subsidiaries, as well as a requirement to timely file periodic reports with the SEC. Each of the restrictive covenants is subject to important exceptions and qualifications that would allow URNA and its subsidiaries to engage in these activities under certain conditions. The indenture also requires that, in the event of a change of control (as defined in the indenture), URNA must make an offer to purchase all of the then outstanding 5 1/2 percent Notes tendered at a purchase price in cash equal to 101 percent of the principal amount thereof, plus accrued and unpaid interest, if any, thereon.

[8] At March 31, 2015, $550 was available under our accounts receivable securitization facility. During the three months ended March 31, 2015, the monthly average amount outstanding under the accounts receivable securitization facility was $362, and the weighted-average interest rate thereon was 0.8 percent. The maximum month-end amount outstanding under the accounts receivable securitization facility during the three months ended March 31, 2015 was $544. Borrowings under the accounts receivable securitization facility are permitted only to the extent that the face amount of the receivables in the collateral pool, net of applicable reserves, exceeds the outstanding loans. As of March 31, 2015, there were $589 of receivables, net of applicable reserves, in the collateral pool. In March 2015, we repaid all of the outstanding borrowings under the accounts receivable securitization facility using a portion of the net proceeds from the debt issuances described below. In April 2015, we used borrowings under the accounts receivable securitization facility to partially fund the debt redemptions described below.