Fair Value of Financial Instruments (Details 2) (Fair Value, Inputs, Level 2 [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	$ 627,950	$ 626,194
Fair value	638,357	620,285
Series B Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	100,000	100,000
Fair value	109,722	107,704
Series C Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	25,000	25,000
Fair value	25,023	24,822
Revolving Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	209,077	191,919
Fair value	210,096	186,590
United States Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	180,000	190,000
Fair value	178,717	183,869
Canadian Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	20,912	21,983
Fair value	20,851	21,226
Australian Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	85,039	89,443
Fair value	85,895	88,299
Other Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	7,922	7,849
Fair value	$ 8,053	$ 7,775