Debt and Subordinated Convertible Debentures (Schedule of long-term debt instruments) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified					6 Months Ended							3 Months Ended																																																																			1 Months Ended
	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2012 Accounts Receivable Securitization Facility [Member]	Jun. 30, 2012 1.9 billion dollar ABL Facility [Member]	Jun. 30, 2012 10 7/8 percent Senior Notes [Member]	Jun. 30, 2012 10 1/4 percent Senior Notes [Member]	Jun. 30, 2012 9 1/4 percent Senior Notes [Member]	Jun. 30, 2012 8 3/8 percent Senior Subordinated Notes [Member]	Jun. 30, 2012 8 1/4 percent Senior Notes [Member]	Jun. 30, 2012 1 7/8 percent Convertible Senior Subordinated Notes [Member]	Jun. 30, 2012 5 3/4 percent Senior Secured Notes [Member]	Mar. 31, 2012 5 3/4 percent Senior Secured Notes [Member]		Jun. 30, 2012 7 3/8 percent Senior Notes [Member]	Mar. 31, 2012 7 3/8 percent Senior Notes [Member]		Jun. 30, 2012 7 5/8 percent Senior Notes [Member]	Mar. 31, 2012 7 5/8 percent Senior Notes [Member]		Jun. 30, 2012 4 percent Convertible Subordinated Notes [Member]	Nov. 30, 2009 4 percent Convertible Subordinated Notes [Member]	Jun. 30, 2012 Convertible quarterly income preferred securities (QUIPS) [Member]	Jun. 30, 2012 6 1/2 Subordinated Convertible Debentures [Member]	Dec. 31, 2011 6 1/2 Subordinated Convertible Debentures [Member]	Jun. 30, 2012 Subsidiaries [Member] Accounts Receivable Securitization Facility [Member]		Dec. 31, 2011 Subsidiaries [Member] Accounts Receivable Securitization Facility [Member]		Jun. 30, 2012 Subsidiaries [Member] 1.9 billion dollar ABL Facility [Member]		Dec. 31, 2011 Subsidiaries [Member] 1.9 billion dollar ABL Facility [Member]		Jun. 30, 2012 Subsidiaries [Member] 10 7/8 percent Senior Notes [Member]	Dec. 31, 2011 Subsidiaries [Member] 10 7/8 percent Senior Notes [Member]	Jun. 30, 2012 Subsidiaries [Member] 10 1/4 percent Senior Notes [Member]		Dec. 31, 2011 Subsidiaries [Member] 10 1/4 percent Senior Notes [Member]		Jun. 30, 2012 Subsidiaries [Member] 9 1/4 percent Senior Notes [Member]	Dec. 31, 2011 Subsidiaries [Member] 9 1/4 percent Senior Notes [Member]	Jun. 30, 2012 Subsidiaries [Member] 8 3/8 percent Senior Subordinated Notes [Member]	Dec. 31, 2011 Subsidiaries [Member] 8 3/8 percent Senior Subordinated Notes [Member]	Jun. 30, 2012 Subsidiaries [Member] 8 1/4 percent Senior Notes [Member]		Dec. 31, 2011 Subsidiaries [Member] 8 1/4 percent Senior Notes [Member]		Jun. 30, 2012 Subsidiaries [Member] 1 7/8 percent Convertible Senior Subordinated Notes [Member]		Dec. 31, 2011 Subsidiaries [Member] 1 7/8 percent Convertible Senior Subordinated Notes [Member]		Jun. 30, 2012 Subsidiaries [Member] Capital Leases [Member]		Dec. 31, 2011 Subsidiaries [Member] Capital Leases [Member]		Jun. 30, 2012 Subsidiaries [Member] 5 3/4 percent Senior Secured Notes [Member]		Dec. 31, 2011 Subsidiaries [Member] 5 3/4 percent Senior Secured Notes [Member]		Jun. 30, 2012 Subsidiaries [Member] 7 3/8 percent Senior Notes [Member]		Dec. 31, 2011 Subsidiaries [Member] 7 3/8 percent Senior Notes [Member]		Jun. 30, 2012 Subsidiaries [Member] 7 5/8 percent Senior Notes [Member]		Dec. 31, 2011 Subsidiaries [Member] 7 5/8 percent Senior Notes [Member]		Jun. 30, 2012 Subsidiaries [Member] Total URNA and subsidiaries debt [Member]		Dec. 31, 2011 Subsidiaries [Member] Total URNA and subsidiaries debt [Member]		Jun. 30, 2012 Parent Company [Member]	Dec. 31, 2011 Parent Company [Member]	Jun. 30, 2012 Parent Company [Member] 4 percent Convertible Subordinated Notes [Member]		Dec. 31, 2011 Parent Company [Member] 4 percent Convertible Subordinated Notes [Member]		Aug. 31, 1998 QUIPS [Member]
Debt Instrument [Line Items]
Total debt	$ 7,289,000,000	[1]	$ 2,987,000,000	[1]																							$ 252,000,000	[2]	$ 255,000,000	[2]	$ 1,287,000,000	[3]	$ 810,000,000	[3]	$ 490,000,000	$ 489,000,000	$ 224,000,000	[4]	$ 0	[4]	$ 493,000,000	$ 493,000,000	$ 750,000,000	$ 750,000,000	$ 698,000,000	[4]	$ 0	[4]	$ 5,000,000	[5]	$ 22,000,000	[5]	$ 132,000,000	[4]	$ 39,000,000	[4]	$ 750,000,000	[6]	$ 0	[6]	$ 750,000,000	[6]	$ 0	[6]	$ 1,325,000,000	[6]	$ 0	[6]	$ 7,156,000,000	[6]	$ 2,858,000,000	[6]			$ 133,000,000	[7]	$ 129,000,000	[7]
Less short-term portion	(421,000,000)	[8]	(395,000,000)	[8]																																																																					(133,000,000)	(129,000,000)
Total long-term debt	6,868,000,000		2,592,000,000																																																																						0	0
Unused borrowing capacity under facility					20,000,000	494,000,000
Interest rate at end of period					0.90%	2.30%
Average outstanding amount under facility					230,000,000
Weighted average interest rate					0.90%	2.40%
A/R Securitization maximum month-end outstanding amount					252,000,000
Letters of credit outstanding						119,000,000
Average outstanding amount						1,048,000,000
ABL Facility maximum month-end outstanding amount						1,287,000,000
Maximum borrowing capacity						1,900,000,000
Stated interest rate							10.875%	10.25%	9.25%	8.375%	8.25%	1.875%	5.75%			7.375%			7.625%			4.00%		6.50%	6.50%
Face amount														750,000,000	[6]		750,000,000	[6]		1,325,000,000	[6]		173,000,000								1,900,000,000
Convertible, conversion price (in dollars per share)												$ 21.83										$ 11.11
Converted debt instruments												17,000,000
Converted debt instruments, shares issued (in shares)												0.8
Principal carrying amount																						168,000,000
Unamortized discount																						35,000,000
Proceeds from QUIPS																																																																															300,000,000
Liquidation value (in dollars per security)																																																																															$ 50
Subordinated convertible debentures	$ 55,000,000		$ 55,000,000																						$ 55,000,000	$ 55,000,000																																															$ 55,000,000	$ 55,000,000

[1] In August 1998, a subsidiary trust of Holdings (the “Trust”) issued and sold $300 of 6 1/2 percent Convertible Quarterly Income Preferred Securities (“QUIPS”) in a private offering. The Trust used the proceeds from the offering to purchase 6 1/2 percent subordinated convertible debentures due 2028 (the “Debentures”), which resulted in Holdings receiving all of the net proceeds of the offering. The QUIPS are non-voting securities, carry a liquidation value of $50 (fifty dollars) per security and are convertible into Holdings’ common stock. Total debt at June 30, 2012 and December 31, 2011 excludes $55 of these Debentures, which are separately classified in our condensed consolidated balance sheets and referred to as “subordinated convertible debentures.” The subordinated convertible debentures reflect the obligation to our subsidiary that has issued the QUIPS. This subsidiary is not consolidated in our financial statements because we are not the primary beneficiary of the Trust.

[2] At June 30, 2012, $20 was available under our accounts receivable securitization facility. The interest rate applicable to the accounts receivable securitization facility was 0.9 percent at June 30, 2012. During the six months ended June 30, 2012, the monthly average amount outstanding under the accounts receivable securitization facility was $230, and the weighted-average interest rate thereon was 0.9 percent. The maximum month-end amount outstanding under the accounts receivable securitization facility during the six months ended June 30, 2012 was $252.

[3] At June 30, 2012, $494 was available under our ABL facility, net of $119 of letters of credit. The interest rate applicable to the ABL facility was 2.3 percent at June 30, 2012. During the six months ended June 30, 2012, the monthly average amount outstanding under the ABL facility was $1,048, and the weighted-average interest rate thereon was 2.4 percent. The maximum month-end amount outstanding under the ABL facility during the six months ended June 30, 2012 was $1,287. In March 2012, the size of the ABL facility was increased to $1.9 billion.

[4] Upon consummation of the RSC merger, we assumed certain of RSC's debt, including capital leases. See below for additional detail regarding the assumed RSC debt.

[5] Based on the price of our common stock during the first quarter of 2012, holders of the 1 7/8 percent Convertible Senior Subordinated Notes had the right to convert the notes during the second quarter of 2012 at a conversion price of $21.83 per share of common stock, and $17 of the 1 7/8 percent Convertible Senior Subordinated Notes were converted. Upon conversion of the notes, we issued approximately 0.8 million shares of our common stock to the applicable holders of the 1 7/8 percent Convertible Senior Subordinated Notes. Based on the price of our common stock during the second quarter of 2012, holders of the 1 7/8 percent Convertible Senior Subordinated Notes may convert the notes during the third quarter of 2012 at a conversion price of $21.83 per share of common stock. Between July 1, 2012 (the beginning of the third quarter) and July 13, 2012, none of the 1 7/8 percent Convertible Senior Subordinated Notes were converted.

[6] In connection with the RSC merger, on March 9, 2012, we issued the merger financing notes. See below for additional detail regarding each of the merger financing notes.

[7] The difference between the June 30, 2012 carrying value of the 4 percent Convertible Senior Notes and the $168 principal amount reflects the $35 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 June 30, 2012, an amount equal to the $35 unamortized portion of the original issue discount is separately classified in our condensed consolidated balance sheets and referred to as “temporary equity.” Based on the price of our common stock during the second quarter of 2012, holders of the 4 percent Convertible Senior Notes have the right to redeem the notes during the third quarter of 2012 at a conversion price of $11.11 per share of common stock. Between July 1, 2012 (the beginning of the third quarter) and July 13, 2012, none of the 4 percent Convertible Senior Notes were redeemed.

[8] As of June 30, 2012, our short-term debt primarily reflects $252 of borrowings under our accounts receivable securitization facility and $133 of 4 percent Convertible Senior Notes. The 4 percent Convertible Senior Notes mature in 2015, but are reflected as short-term debt because they are redeemable at June 30, 2012.