Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance	$ 13,468		$ 11,741		$ 11,172		$ 10,969
Valuation Allowances and Reserves, Charged to Cost and Expense	301		5,514		229
Valuation Allowances and Reserves, Adjustments	$ 1,426	[1]	$ (4,945)	[1]	$ (26)	[1]

[1] Primarily accounts receivable written off during the period.