Long-Term Debt and Capital Lease - Schedule of Long-Term Debt (Details) (USD $)	12 Months Ended								12 Months Ended		0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 LIBOR [Member]	Dec. 31, 2013 Minimum [Member] LIBOR [Member]	Dec. 31, 2013 Minimum [Member] Prime Rate [Member]	Mar. 28, 2013 Maximum [Member]	Mar. 27, 2013 Maximum [Member]	Dec. 31, 2013 Maximum [Member] LIBOR [Member]	Dec. 31, 2013 Maximum [Member] Prime Rate [Member]	May 24, 2012 Interest Rate Swap 9 [Member]	Dec. 31, 2013 Interest Rate Swap 9 [Member]	Dec. 31, 2012 Interest Rate Swap 9 [Member]	Dec. 31, 2013 Revolving Loan Facility [Member]		Dec. 31, 2012 Revolving Loan Facility [Member]	Dec. 31, 2013 Senior Notes [Member] Senior Notes 8.875% [Member]		Dec. 31, 2012 Senior Notes [Member] Senior Notes 8.875% [Member]	Dec. 31, 2013 Senior Notes [Member] Senior Notes 7.250% [Member]		Feb. 11, 2013 Senior Notes [Member] Senior Notes 7.250% [Member]	Dec. 31, 2012 Senior Notes [Member] Senior Notes 7.250% [Member]		Dec. 31, 2013 Notes Payable to Banks [Member] Unsecured, 4.75%, Due October 2029 [Member]		Dec. 31, 2012 Notes Payable to Banks [Member] Unsecured, 4.75%, Due October 2029 [Member]		Dec. 31, 2013 Capital Lease Obligations [Member]		Dec. 31, 2012 Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Total long-term debt and capital lease obligations	$ 658,695,000	$ 478,198,000												$ 235,000,000		$ 296,000,000	$ 173,695,000		$ 173,388,000	$ 250,000,000	[1],[2]		$ 0	[1],[2]	$ 0	[3]	$ 2,971,000	[3]	$ 0	[4]	$ 5,839,000	[4]
Less current portion	0	3,206,000
Long-term debt and capital lease obligations, net of current portion	658,695,000	474,992,000
Face amount														600,000,000	[5]		200,000,000	[2],[6]		250,000,000	[1],[2]	250,000					3,315,000	[3]
Fixed rate cost																	8.875%			7.25%	[1],[2]	7.25%					4.75%	[3]
Unamortized discount																	1,305,000		1,612,000
Weighted average interest rate														3.21%	[7]
Applicable margins				3.00%	2.00%	1.00%			3.00%	2.00%
Partnership redemption option maximum												35.00%
Partnership senior note redemption option price												108.875%
Repayment of debt											25,000,000
Prepayment premium												272,000	2,219,000
Maximum amount of borrowings and letters of credit available under Credit Facility							600,000,000	400,000,000
Cash paid for interest	33,038,000	29,239,000	22,818,000
Capitalized interest	$ 1,096,000	$ 1,136,000	$ 624,000

[1] On February 11, 2013, the Partnership completed a private placement of $250,000 in aggregate principal amount of 7.250% senior unsecured notes due 2021 to qualified institutional buyers under Rule 144A. The Partnership filed with the SEC a registration statement to exchange the 2021 Notes for substantially identical notes that are registered under the Securities Act, and completed the exchange offer on July 31, 2013.

[2] The 2018 and 2021 indentures restrict the Partnership’s ability to sell assets; pay distributions or repurchase units or redeem or repurchase subordinated debt; make investments; incur or guarantee additional indebtedness or issue preferred units; and consolidate, merge or transfer all or substantially all of its assets. Many of these covenants will terminate if the notes achieve an investment grade rating from each of Moody’s Investors Service, Inc. and Standard & Poor’s Ratings Services and no default (as defined in the indentures) has occurred.

[3] In October of 2013, the Partnership retired the note payable to bank with borrowings under the Partnership's revolving credit facility.

[4] In November of 2013, the Partnership retired the capital lease obligations with borrowings under the Partnership's revolving credit facility. In conjunction with the retirement, the Partnership incurred a debt prepayment premium in the amount of $272, which is included in the Consolidated Statement of Operations for the year ended December 31, 2013.

[5] Effective March 28, 2013, the Partnership increased the maximum amount of borrowings and letters of credit available under the Credit Facility from $400,000 to $600,000 and extended the maturity date of the facility from April 2016 to March 2018.

[6] Pursuant to the indenture under which the senior notes were issued, the Partnership has the option to redeem up to 35% of the aggregate principal amount at a redemption price of 108.875% of the principal amount, plus accrued and unpaid interest with the proceeds of certain equity offerings. On April 24, 2012, the Partnership notified the trustee of its intention to exercise a partial redemption of the Partnership’s senior notes pursuant to the indenture. On May 24, 2012, the Partnership redeemed $25,000 of the senior notes from various holders using proceeds of the Partnership’s January 2012 follow-on equity offering, which in the interim were used to pay down amounts outstanding under the Partnership’s revolving credit facility. In conjunction with the redemption, the Partnership incurred a debt prepayment premium in the amount of $2,219, which is included in the Consolidated Statement of Operations for the year ended December 31, 2012.

[7] Interest rate fluctuates based on the LIBOR rate plus an applicable margin set on the date of each advance. The margin above LIBOR is set every three months. Indebtedness under the credit facility bears interest at LIBOR plus an applicable margin or the base prime rate plus an applicable margin. The applicable margin for revolving loans that are LIBOR loans ranges from 2.00% to 3.00% and the applicable margin for revolving loans that are base prime rate loans ranges from 1.00% to 2.00%. The applicable margin for LIBOR borrowings at December 31, 2013 is 3.00%. The credit facility contains various covenants which limit the Partnership’s ability to make certain investments and acquisitions; enter into certain agreements; incur indebtedness; sell assets; and make certain amendments to the Omnibus Agreement. The Partnership is permitted to make quarterly distributions so long as no event of default exists.