Long-term debt and cash flow hedges - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended		12 Months Ended							3 Months Ended		6 Months Ended		3 Months Ended		0 Months Ended		0 Months Ended					3 Months Ended			12 Months Ended																										1 Months Ended	6 Months Ended	0 Months Ended		6 Months Ended				0 Months Ended
	Mar. 31, 2011 Derivative	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2010 Derivative	Dec. 31, 2013	Jun. 30, 2014 Revolving Credit Facility	Jun. 30, 2014 Term Loan A	Jun. 30, 2014 Term Loan- A2	Jun. 30, 2014 Term Loan B Facility	Jun. 30, 2014 Previous Credit Facility	Jun. 30, 2014 Term Loan-A and Term Loan A2 facilities	Jun. 30, 2013 Term Loan-A and Term Loan A2 facilities	Jun. 30, 2014 Term Loan-A and Term Loan A2 facilities	Jun. 30, 2013 Term Loan-A and Term Loan A2 facilities	Jun. 30, 2014 Term Loan-A and Term Loan A2 facilities Quarterly installment payments commence in the fourth quarter of 2014 through September, 2016	Jun. 30, 2014 Term Loan-A and Term Loan A2 facilities Quarterly installment payments after September, 2016	Aug. 07, 2014 Subsequent Event Term Loan B Facility	Oct. 31, 2013 Amendment of Credit Facility	Aug. 07, 2014 Amendment of Credit Facility Subsequent Event	Aug. 01, 2014 Amendment of Credit Facility Subsequent Event	Aug. 07, 2014 Amendment of Credit Facility Subsequent Event Revolving Credit Facility	Aug. 07, 2014 Amendment of Credit Facility Subsequent Event Term Loan A	Mar. 31, 2011 One Point Nine One Percent Forward Starting Interest Rate Swaps	Mar. 31, 2011 Two Point Five Zero Percent Forward Starting Interest Rate Swaps	Mar. 31, 2011 One Point Nine Six Percent Forward Starting Interest Rate Swaps	Mar. 31, 2011 One Point Three Two Percent Forward Starting Interest Rate Swaps	Dec. 31, 2010 Two Point Three Eight Percent Forward Starting Interest Rate Swaps	Jun. 30, 2014 Interest Rate Swap	Dec. 31, 2013 Interest Rate Swap	Jun. 30, 2014 Short Term on Demand Credit Facility Revolving Credit Facility	Jun. 30, 2014 Letter of Credit Revolving Credit Facility	Mar. 31, 2011 Cash Flow Hedging Forward Starting Interest Rate Swaps	Mar. 31, 2011 Cash Flow Hedging One Point Nine One Percent Forward Starting Interest Rate Swaps	Mar. 31, 2011 Cash Flow Hedging Two Point Five Zero Percent Forward Starting Interest Rate Swaps	Mar. 31, 2011 Cash Flow Hedging One Point Nine Six Percent Forward Starting Interest Rate Swaps	Mar. 31, 2011 Cash Flow Hedging One Point Three Two Percent Forward Starting Interest Rate Swaps	Dec. 31, 2010 Cash Flow Hedging Two Point Three Eight Percent Forward Starting Interest Rate Swaps	Jun. 30, 2014 One Month Eurodollar Rate Plus Index Based Loans Term Loan B Facility	Jun. 30, 2014 One Two Three Six Month Eurodollar Rate Plus Index Based Loans Revolving Credit Facility	Jun. 30, 2014 One Two Three Six Month Eurodollar Rate Plus Index Based Loans Term Loan B Facility	Jun. 30, 2014 ABR-based loans	Jun. 30, 2014 Minimum One Month Eurodollar Rate Plus Index Based Loans Revolving Credit Facility	Jun. 30, 2014 Minimum One Month Eurodollar Rate Plus Index Based Loans Term Loan A	Jun. 30, 2014 Minimum One Month Eurodollar Rate Plus Index Based Loans Term Loan- A2	Jun. 30, 2014 Minimum One Two Three Six Month Eurodollar Rate Plus Index Based Loans Term Loan A	Jun. 30, 2014 Minimum One Two Three Six Month Eurodollar Rate Plus Index Based Loans Term Loan- A2	Jun. 30, 2014 Maximum One Month Eurodollar Rate Plus Index Based Loans Revolving Credit Facility	Jun. 30, 2014 Maximum One Month Eurodollar Rate Plus Index Based Loans Term Loan A	Jun. 30, 2014 Maximum One Month Eurodollar Rate Plus Index Based Loans Term Loan- A2	Jun. 30, 2014 Maximum One Two Three Six Month Eurodollar Rate Plus Index Based Loans Revolving Credit Facility	Jun. 30, 2014 Maximum One Two Three Six Month Eurodollar Rate Plus Index Based Loans Term Loan A	Jun. 30, 2014 Maximum One Two Three Six Month Eurodollar Rate Plus Index Based Loans Term Loan- A2	Sep. 29, 2010 7.00% Senior Unsecured Notes	Jun. 30, 2014 7.00% Senior Unsecured Notes	Jul. 31, 2014 7.00% Senior Unsecured Notes Subsequent Event	Jul. 31, 2014 7.00% Senior Unsecured Notes Subsequent Event	Jun. 30, 2014 Senior Notes 7.125%	Jun. 30, 2008 Senior Notes 7.125%	Jun. 30, 2006 Senior Notes 7.125%	Jun. 30, 2014 Accounts Receivable Securitization Facility	Aug. 01, 2014 Accounts Receivable Securitization Facility Amendment of Credit Facility Subsequent Event	Aug. 07, 2014 Three Point Seven Five Zero Percent Senior Secured Notes Due Two Thousand Nineteen Subsequent Event	Aug. 07, 2014 Four Point Seven Five Zero Percent Senior Secured Notes Due Two Thousand Twenty Two Subsequent Event	Dec. 31, 2013 Accounts Payable and Accrued Liabilities Interest Rate Swap	Dec. 31, 2013 Other Noncurrent Liabilities Interest Rate Swap
Debt Instrument [Line Items]
Line of credit facility, starting date																			Aug. 07, 2014																																										Aug. 01, 2014
Line of credit facility, maturity month																			2019-08
Line of credit facility, borrowing capacity						$ 800,000,000															$ 800,000,000	$ 1,774,000,000									$ 125,000,000
Reduction of long-term debt		179,126,000	196,096,000														550,000,000																																						250,000,000
Line of credit facility, maturity year																	2016
Accounts receivable securitization program credit facility, borrowing capacity																		275,000,000		360,000,000
Line of credit facility, maturity date																																																													Oct. 25, 2016
Senior notes, issued																																																					250,000,000						250,000,000			300,000,000	300,000,000
Senior notes, interest rate																																																					7.00%			7.00%			7.125%			3.75%	4.75%
Debt instrument redemption, date																																																							Jul. 31, 2014
Unsecured notes make-whole redemption price																																																							104.56%
Line of credit facility amount outstanding						0	913,000,000	861,000,000	550,000,000	0																				4,000,000
Rate adjustment to weighted average federal funds rate for credit facility borrowings		0.50%
Rate adjustment to one month Eurodollar rate on credit facility borrowings		1.00%
Consolidated leverage ratio																																						1.25%	1.50%	2.25%		0.50%	0.50%	0.50%	1.50%	1.50%	1.25%	1.25%	1.25%	2.25%	2.25%	2.25%
Current applicable margins						1.50%	1.50%	1.50%	2.25%																																0.50%
Line of credit facility, available borrowing capacity						776,000,000
Letters of credit, outstanding						20,000,000
Scheduled principal payments made											18,000,000	18,000,000	36,000,000	36,000,000	11,000,000	22,000,000
Accounts receivable securitization program credit facility, amount outstanding		130,000,000
Accounts receivable securitization program, additional capacity																																																												145,000,000
Senior notes, maturity date																																																						Oct. 01, 2018			Jun. 30, 2016
Senior notes, repayment terms																																																						Payable semiannually in arrears on April 1st and October 1st of each year			Interest on the 7.125% Notes is payable semiannually in arrears on June 30th and December 30th of each year
Treasury rate plus, basis points																																																					0.50%
Line of credit facility additional borrowing capacity																																																										150,000,000
Fair value of debt		3,150,000,000
Long-term debt		3,070,311,000			3,209,762,000
Number of additional forward starting interest rate swaps	6			4
Notional amount of interest rate cash flow hedges																																425,000,000	225,000,000	100,000,000	25,000,000	75,000,000	600,000,000
Average fixed rate payable on interest rate swap																							1.91%
Fixed rate payable on interest rate swap																								2.50%	1.96%	1.32%	2.38%
Maturity date of interest rate cash flow hedges																								Dec. 01, 2014	Dec. 01, 2013	Dec. 01, 2012	May 01, 2015
Fair value of our interest rate swaps, liability																												$ 16,000,000	$ 24,000,000																																			$ 19,000,000	$ 5,000,000