LONG-TERM DEBT - Senior Secured Credit Facility (Details) (USD $)	6 Months Ended		3 Months Ended		6 Months Ended				6 Months Ended										6 Months Ended
	Jun. 30, 2014 At End Of Each Fiscal Quarter Thereafter	Jun. 30, 2014 Amendment Of Credit Facility	Jun. 30, 2014 2011 Credit Facility	Jun. 30, 2013 2011 Credit Facility	Jun. 30, 2014 2011 Credit Facility	Jun. 30, 2013 2011 Credit Facility	Jun. 30, 2014 2011 Credit Facility Maximum	Jun. 30, 2014 2011 Credit Facility Minimum	Jun. 30, 2014 2011 Credit Facility Foreign Subsidiaries	Jun. 30, 2014 2011 Credit Facility Foreign Subsidiaries Minimum	Jun. 30, 2014 2011 Credit Facility Acquisition Covenants Maximum	Jun. 30, 2014 2011 Credit Facility Acquisition Covenants Minimum	Jun. 30, 2014 2011 Credit Facility Revolving Credit Facility	Jun. 30, 2014 2011 Credit Facility Letter of Credit	Dec. 31, 2013 2011 Credit Facility LIBOR Maximum	Dec. 31, 2013 2011 Credit Facility LIBOR Minimum	Dec. 31, 2013 2011 Credit Facility Other Loans Maximum	Dec. 31, 2013 2011 Credit Facility Other Loans Minimum	Jun. 30, 2014 2011 Credit Facility Amendment Of Credit Facility	Jul. 27, 2011 2011 Credit Facility Amendment Of Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity																				$ 550,000,000
Line of credit, expiration date																			Mar. 31, 2016
Increase in total commitments							100,000,000.0
Capitalized finance costs		1,400,000	4,900,000		4,900,000
Line of credit, interest rate basis points															3.00%	2.25%	2.00%	1.25%
Interest coverage ratio								3.00
Additional interest rate above Federal Funds rate					0.50%
Additional interest rate above one-month adjusted LIBOR					1.00%
Commitment fee minimum			0.50%		0.50%
Consolidated funded indebtedness to total capitalization ratio							0.45
Leverage ratio							2.00				4.00	1.00
Debt instrument covenant annual capital expenditures									250,000,000
Coverage ratio	2.00									3.00
Line of credit, remaining borrowing capacity			189,300,000		189,300,000							25,000,000
Line of credit, amount outstanding													$ 40,000,000	$ 49,100,000
Line of credit, weighted average interest rate			2.88%	2.67%	2.88%	2.68%
Line of credit, covenant terms					the amended 2011 Credit Facility contains certain affirmative and negative covenants, including, without limitation, restrictions on (i) liens; (ii) debt, guarantees and other contingent obligations; (iii) mergers and consolidations; (iv) sales, transfers and other dispositions of property or assets; (v) loans, acquisitions, joint ventures and other investments (with acquisitions permitted so long as, after giving pro forma effect thereto, no default or event of default exists under the 2011 Credit Facility, the pro forma consolidated total leverage ratio does not exceed 4.00 to 1.00, we are in compliance with other financial covenants and we have at least $25.0 million of availability under the 2011 Credit Facility); (vi) dividends and other distributions to, and redemptions and repurchases from, equityholders; (vii) making investments, loans or advances; (viii) selling properties; (ix) prepaying, redeeming or repurchasing subordinated (contractually or structurally) debt; (x) engaging in transactions with affiliates; (xi) entering into hedging arrangements; (xii) entering into sale and leaseback transactions; (xiii) granting negative pledges other than to the lenders; (xiv) changes in the nature of business; (xv) amending organizational documents; and (xvi) changes in accounting policies or reporting practices; in each of the foregoing cases, with certain exceptions.