Incentive Plans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value of common units under the incentive plan			Average closing price over the last 20 trading days prior to the vesting date.
Vesting period of Grants in years			4 years
Risk free interest rate			0.12%
Risk free interest rate			1.06%
Volatility rate			28.80%
Volatility rate			29.92%
Partnership's historical distribution rate	7.40%		7.40%
Partnership's historical forfeiture rate	5.20%		5.20%
Expenses related to Incentive Plan to be reimbursed to general partner			$ 601,000	$ 60,000
Payments made in connection with Long-Term Incentive Plan			6,500,000	7,000,000
Unaccrued cost associated with outstanding grants and related DERs	7,700,000		7,700,000
General Partner [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expenses related to Incentive Plan to be reimbursed to general partner	$ 1,100,000	$ 600,000	$ 1,500,000	$ 7,500,000