Long-Term Debt and Capital Lease - Schedule of Long-Term Debt (Details) (USD $)	12 Months Ended			12 Months Ended				12 Months Ended																		0 Months Ended	12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2012 Senior Notes [Member]		Dec. 31, 2011 Senior Notes [Member]		Dec. 31, 2012 Revolving Loan Facility [Member]		Dec. 31, 2011 Revolving Loan Facility [Member]		Dec. 31, 2012 Capital Lease Obligations [Member]	Dec. 31, 2011 Capital Lease Obligations [Member]	Dec. 31, 2012 LIBOR [Member]	Dec. 31, 2012 Minimum [Member] LIBOR [Member]	Dec. 31, 2012 Minimum [Member] Prime Rate [Member]	Dec. 31, 2012 Maximum [Member] LIBOR [Member]	Dec. 31, 2012 Maximum [Member] Prime Rate [Member]	Dec. 31, 2012 Interest Rate Swap 1 [Member] Senior Notes [Member]	Dec. 31, 2012 Interest Rate Swap 3 [Member] Senior Notes [Member]	Dec. 31, 2012 Interest Rate Swap 4 [Member] Revolving Loan Facility [Member] swap	Dec. 31, 2012 Interest rate Swap 5 [Member] Revolving Loan Facility [Member] swap	Dec. 31, 2012 Interest Rate Swap 6 [Member] Revolving Loan Facility [Member] swap	Dec. 31, 2012 Interest Rate Swap 7 [Member] Revolving Loan Facility [Member]	Dec. 31, 2012 Interest Rate Swap 8 [Member] Revolving Loan Facility [Member] swap	Apr. 24, 2012 Interest Rate Swap 9 [Member]	Dec. 31, 2012 Unsecured, 4.75%, Due October 2029 [Member] Notes Payable to Banks [Member]	Dec. 31, 2011 Unsecured, 4.75%, Due October 2029 [Member] Notes Payable to Banks [Member]	Dec. 31, 2012 Secured, 7.50%, Due January 2017 [Member] Notes Payable to Banks [Member]	Dec. 31, 2011 Secured, 7.50%, Due January 2017 [Member] Notes Payable to Banks [Member]	Dec. 31, 2012 Repayment of Debt [Member]	Dec. 31, 2012 Repayment of Debt [Member] Interest Rate Swap 9 [Member]
Debt Instrument [Line Items]
Total long-term debt and capital lease obligations	$ 478,198,000	$ 460,202,000		$ 173,388,000	[1],[2]	$ 197,808,000	[1],[2]	$ 296,000,000	[3],[4]	$ 250,000,000	[3],[4]	$ 5,839,000	$ 6,031,000														$ 2,971,000	$ 0	$ 0	$ 6,363,000
Less current portion	3,206,000	1,261,000	[5]
Long-term debt and capital lease obligations, net of current portion	474,992,000	458,941,000	[5]
Face amount				200,000,000				400,000,000																			3,315,000		7,354,000
Fixed rate cost				8.875%																	2.82%	3.40%	4.61%	4.77%	5.25%		4.75%		7.50%
Weighted average interest rate								3.58%
Maturity date				Apr. 30, 2018				Apr. 30, 2016																			Oct. 31, 2029		Jan. 31, 2017
Unamortized discount				1,612,000		2,192,000
Applicable margins														3.00%	2.00%	1.00%	3.25%	2.25%
Applicable margin for next three months														2.25%
Applicable margin thereafter														2.75%
Notional Amount of Interest Rate Derivatives																			40,000,000	60,000,000	40,000,000	25,000,000	25,000,000	30,000,000	75,000,000
Number of interest rate swaps																					2	2	2		2
Effective fixed rate																					2.58%	3.05%	4.31%		5.10%
Partnership redemption option maximum																															35.00%	35.00%
Partnership senior note redemption option price																															108.875%	108.875%
Repayment of debt																										25,000,000
Prepayment premium																										$ 2,219,000
Interest rate terms	The applicable margin for revolving loans that are LIBOR loans ranges from 2.00% to 3.25% and the applicable margin for revolving loans that are base prime rate loans ranges from 1.00% to 2.25%.  The applicable margin for existing LIBOR borrowings is 3.00%.  Effective October 1, 2012, the applicable margin for existing LIBOR borrowings remained at 3.00%.  Effective January 1, 2013, the applicable margin for existing LIBOR borrowings will decrease to 2.25%.

[1] Effective September 2010, the Partnership entered into an interest rate swap that swapped $40,000 of fixed rate to floating rate. The floating rate cost was the applicable three-month LIBOR rate. This interest rate swap was scheduled to mature in April 2018, but was terminated in August 2011.** Effective September 2010, the Partnership entered into an interest rate swap that swapped $60,000 of fixed rate to floating rate. The floating rate cost was the applicable three-month LIBOR rate. This interest rate swap was scheduled to mature in April 2018, but was terminated in August 2011.

[2] 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.

[3] 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 3.25% and the applicable margin for revolving loans that are base prime rate loans ranges from 1.00% to 2.25%. The applicable margin for existing LIBOR borrowings is 3.00%. Effective January 1, 2013, the applicable margin for existing LIBOR borrowings decreased to 2.25%. Effective April 1, 2013, the applicable margin for existing LIBOR borrowings will increase to 2.75%.

[4] Effective October 2008, the Partnership entered into a cash flow hedge that swapped $40,000 of floating rate to fixed rate. The fixed rate cost was 2.82% plus the Partnership’s applicable LIBOR borrowing spread. Effective April 2009, the Partnership entered into two subsequent swaps to lower its effective fixed rate to 2.58% plus the Partnership’s applicable LIBOR borrowing spread. These cash flow hedges were scheduled to mature in October 2010, but were terminated in March 2010.*** Effective January 2008, the Partnership entered into a cash flow hedge that swapped $25,000 of floating rate to fixed rate. The fixed rate cost was 3.40% plus the Partnership’s applicable LIBOR borrowing spread. Effective April 2009, the Partnership entered into two subsequent swaps to lower its effective fixed rate to 3.050% plus the Partnership’s applicable LIBOR borrowing spread. These cash flow hedges matured in January 2010.*** Effective September 2007, the Partnership entered into a cash flow hedge that swapped $25,000 of floating rate to fixed rate. The fixed rate cost was 4.61% plus the Partnership’s applicable LIBOR borrowing spread. Effective March 2009, the Partnership entered into two subsequent swaps to lower its effective fixed rate to 4.31% plus the Partnership’s applicable LIBOR borrowing spread. These cash flow hedges were scheduled to mature in September 2010, but were terminated in March 2010.*** Effective November 2006, the Partnership entered into an interest rate swap that swapped $30,000 of floating rate to fixed rate. The fixed rate cost was 4.77% plus the Partnership’s applicable LIBOR borrowing spread. This cash flow hedge matured in March 2010.*** Effective March 2006, the Partnership entered into a cash flow hedge that swapped $75,000 of floating rate to fixed rate. The fixed rate cost was 5.25% plus the Partnership’s applicable LIBOR borrowing spread. Effective February 2009, the Partnership entered into two subsequent swaps to lower its effective fixed rate to 5.10% plus the Partnership’s applicable LIBOR borrowing spread. These cash flow hedges were scheduled to mature in November 2010, but were terminated in March 2010.

[5] Financial information has been revised to include balances attributable to Redbird Class A interests and the Blending and Packaging Assets acquired from Cross. See Note 2(a) – Principles of Presentation and Consolidation.