Supplemental cash flow information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash paid for:
Interest	$ 27,320	$ 29,756	$ 37,233
Income taxes, net of refunds	22,275	28,967	16,413
Increases in accounts payable for capital expenditures	$ 186	$ 709