Other long-term liabilities - Convertible Debentures (Details) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2019 $ / shares
Debt Instrument [Line Items]
Long-term debt	$ 3,931,868	$ 3,336,795
Debt instrument, convertible, number of equity instruments (in shares) \| shares	44,130
Debt conversion, shares issued (in shares) \| shares	19,429	56,926
Convertible Unsecured Subordinated Debentures \| Convertible Subordinated Debt
Debt Instrument [Line Items]
Long-term debt	$ 342	$ 470
Debt instrument, effective interest rate	0.00%
Conversion price (CAD per share) \| $ / shares			$ 10.60
Principle converted amount	$ 148	$ 447

The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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The number of shares issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or payments in the period.

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The price per share of the conversion feature embedded in the debt instrument.

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The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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