Business combinations - DigitalGlobe (Details) - USD ($)			3 Months Ended									12 Months Ended
	Jun. 15, 2018	Oct. 05, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2017	Oct. 04, 2017
Business combination
Debt issuance costs												$ 4,000,000	$ 3,000,000
Accelerated share-based awards relating to post-acquisition services														$ 33,000,000
Revenues			$ 410,000,000	$ 413,000,000	$ 412,000,000	$ 431,000,000	$ 418,000,000	$ 433,000,000	$ 487,000,000	$ 466,000,000		1,666,000,000	1,804,000,000	1,257,000,000
Income before income taxes												77,000,000	(923,000,000)	(223,000,000)
Liabilities
Goodwill			$ 1,455,000,000				$ 1,455,000,000				$ 1,617,000,000	1,455,000,000	1,455,000,000	1,617,000,000
Acquisition related costs												$ 16,000,000	$ 33,000,000	60,000,000
DigitalGlobe
Business combination
Common share exchanged for cash		$ 17.50
Common share exchange ratio (in shares)		0.3132
Closing price of share (in dollars per share)																$ 54.57
Share issuance costs		$ 3,000,000
Fair value of replacement awards attributable to pre-acquisition		16,000,000
Fair value of replacement awards attributable to post-acquisition		$ 14,000,000
Number of shares owned by dissenting shareholders		80,000
Number of dissenting common shareholders		352,225
Shares issued in acquisition	2,206,464
Revenues											222,000,000
Income before income taxes											$ 8,000,000
Proforma information
Revenue														2,300,000,000
Summary of fair value of consideration and preliminary estimated fair value of assets acquired and liabilities assumed
Cash paid		$ 1,131,000,000
Shares issued		1,063,000,000
Merger consideration to be settled		3,000,000
Liability to dissenting shareholders		115,000,000
Issuance of replacement equity-settled awards		16,000,000
Purchase consideration		2,328,000,000
Assets
Cash and cash equivalents		171,000,000
Trade and other receivables		142,000,000
Property, plant and equipment		696,000,000
Intangible assets, net		1,440,000,000
Other assets		106,000,000
Total Assets		2,555,000,000
Liabilities
Accounts payable		83,000,000
Other current liabilities		4,000,000
Pension and other postretirement benefit liabilities		29,000,000
Long-term debt		1,276,000,000
Other liabilities		504,000,000
Total Liabilities		1,896,000,000
Fair value of net identifiable assets acquired		659,000,000
Goodwill		1,669,000,000
Goodwill is deductible for income tax purposes		0
Acquisition related costs														$ 60,000,000
DigitalGlobe | Syndicated Credit Facility
Business combination
Aggregate principal amount		3,800,000,000													$ 3,750,000,000
Initial draw of debt		3,100,000,000
Debt issuance costs		63,000,000
Equity award-holders pay-out		1,200,000,000
Refinance debt of acquiree		1,300,000,000
Refinance debt		$ 742,000,000