Debt and Other Credit Facilities (Narrative) (Details) $ / shares in Units, £ in Millions			9 Months Ended	12 Months Ended
	Nov. 15, 2018 $ / shares	Apr. 25, 2018	Sep. 30, 2019 USD ($) $ / shares	Dec. 31, 2019 USD ($) transporter	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Feb. 07, 2020 USD ($)	Dec. 31, 2019 GBP (£)	Sep. 30, 2019 GBP (£)	Jun. 30, 2019	Sep. 30, 2018	Apr. 12, 2018
Debt Instrument [Line Items]
Revolving credit agreement				$ 1,210,000,000	$ 1,248,000,000
Nonrecourse project debt				7,000,000	17,000,000				£ 62.0
Exercise price (usd per share) | $ / shares			$ 40.02
Percentage of strike price above reported last sale price			31.00%
Proceeds from sale of warrants			$ 22,000,000	$ 0	22,000,000	$ 0
Class A 3.5% Index Linked Bonds
Debt Instrument [Line Items]
Guaranteed secured bonds, percentage				3.50%				3.50%
Class A 3.5% Index Linked Bonds | United Kingdom, Pounds
Debt Instrument [Line Items]
Secured bonds | £								£ 56.0
Class B 5.9% Fixed Rate Bonds
Debt Instrument [Line Items]
Guaranteed secured bonds, percentage				5.90%				5.90%
Class B 5.9% Fixed Rate Bonds | United Kingdom, Pounds
Debt Instrument [Line Items]
Secured bonds | £								£ 20.7
Minimum
Debt Instrument [Line Items]
Subordinated notes payable, interest rate				11.25%
Maximum
Debt Instrument [Line Items]
Subordinated notes payable, interest rate				16.00%
Convertible Debt
Debt Instrument [Line Items]
Conversion rate	0.0391961
Line of Credit | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity							$ 500,000,000
Term Loan A
Debt Instrument [Line Items]
Percentage of aggregate principal										2.50%
Term Loan A | Secured Debt
Debt Instrument [Line Items]
Revolving credit agreement				$ 350,000,000
Covenant, leverage ratio		3.50
Covenant, interest coverage ratio												3.00
Term Loan A | Secured Debt | Subsequent Event
Debt Instrument [Line Items]
Face amount due at maturity							275,000,000
Term Loan A | Secured Debt | Maximum
Debt Instrument [Line Items]
Covenant, leverage ratio		4.50
Term Loan B | LIBOR Margin
Debt Instrument [Line Items]
Basis spread on variable rate		3.75%
Term Loan B | Secured Debt
Debt Instrument [Line Items]
Revolving credit agreement				800,000,000
Percentage of aggregate principal											0.25%
Term Loan B | Secured Debt | Subsequent Event
Debt Instrument [Line Items]
Face amount due at maturity							520,000,000
Notes Due 2023 | Convertible Debt
Debt Instrument [Line Items]
Face amount due at maturity				350,000,000
If-converted value in excess of principal				68,000,000
Equity method investments				57,000,000	57,000,000
Interest cost, contractual coupon				9,000,000	1,000,000
Interest cost, amortization of discount				$ 12,000,000	$ 1,000,000
Interest rate, stated percentage	2.50%
Guaranteed secured bonds, percentage				6.50%	6.50%			6.50%
Conversion price (usd per share) | $ / shares	$ 25.51
Letters of Credit, Surety Bonds and Bank Guarantees
Debt Instrument [Line Items]
Letters of credit outstanding relate to joint venture operations				$ 170,000,000
Nonrecourse Project Finance Debt
Debt Instrument [Line Items]
Ownership percentage (in percentage)				50.00%				50.00%
Number of heavy equipment transporters | transporter				91
Number of heavy equipment transporters, term period, in years				22 years
Revolving Credit Facility
Debt Instrument [Line Items]
Letters of credit, outstanding amount				$ 500,000,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Letters of credit, outstanding amount				26,000,000
Long-term line of credit				0
Revolving Credit Facility | Line of Credit | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity							$ 500,000,000
Letter of Credit
Debt Instrument [Line Items]
Letters of credit, outstanding amount				500,000,000
Letter of Credit | Line of Credit
Debt Instrument [Line Items]
Letters of credit, outstanding amount				100,000,000
Letter of Credit | Committed Line of Credit | Line of Credit
Debt Instrument [Line Items]
Face amount due at maturity				1,000,000,000
Letter of Credit | Uncommitted Line of Credit | Line of Credit
Debt Instrument [Line Items]
Letters of credit, outstanding amount				199,000,000
Face amount due at maturity				1,000,000,000.0
Line of credit facility, maximum borrowing capacity				$ 368,000,000