Supplemental cash flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Continuing operations	$ 29,404	$ 135,862	$ 98,801
Balance of cash, cash equivalents and restricted cash at end of year	29,404	135,862	128,041	$ 105,117
Supplemental Cash Flow Information [Abstract]
Cash paid for income taxes, net of refunds	84,045	62,889	154,693
Cash paid for interest	186,086	182,465	200,512
Prepaid expenses and other current assets
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash equivalents	$ 0	$ 0	$ 29,240