Supplemental cash flow information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash paid during the period for:
Interest	$ 7,765	$ 5,861
Income taxes, net of refunds	4,470	5,697
Capital expenditures incurred but not yet paid	$ 1,123	$ 3,167