Employees, Retirement and Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Nonvested Restricted Stock Units Activity

A summary of restricted and phantom unit activity and changes during the three months ended March 31, 2018, is presented below:

Restricted and Phantom Units	Units	Weighted Average Grant-Date Fair Value
Outstanding at January 1, 2018 (nonvested)	119,009	$	34.77
Granted	12,890	30.23
Outstanding at March 31, 2018 (nonvested)	131,899	$	34.33

Schedule of Nonvested Performance-based Units Activity

A summary of performance unit activity and changes for the three months ended March 31, 2018, is presented below:

Performance Units	Units
Outstanding at January 1, 2018 (nonvested)	36,911
Granted	2,764
Vesting and transfer of common units to recipients	(4,283	)
Outstanding at March 31, 2018 (nonvested)	35,392