Partners’ Equity, Income Allocations and Cash Distributions 2011 Issuances (Details) (USD $)	1 Months Ended			12 Months Ended			0 Months Ended	12 Months Ended
	Dec. 31, 2011	Nov. 30, 2009	May 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Nov. 09, 2011 Legacy Frontier [Member]	Dec. 31, 2011 Legacy Frontier [Member]
Capital Unit [Line Items]
Partners' Capital Account, Units	11,097,615			11,097,615
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest				2.00%		2.00%
Ownership Percentage by parent, Controlling Interest	42.00%			42.00%
Partners' Capital Account, Units, Sold in Public Offering	1,475,000	2,185,000	2,192,400
Sale of Common Units, Price Per Share	$ 53.50	$ 35.78	$ 27.80	$ 53.50
Proceeds from Issuance of Common Limited Partners Units	$ 75,800,000	$ 74,900,000	$ 58,400,000	$ 75,815,000	$ 0	$ 133,301,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares							3,807,615	3,807,615
General Partners' Contributed Capital	$ 5,900,000			$ 5,900,000		$ 3,800,000