Employees, Retirement and Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2012

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

Schedule of Nonvested Restricted Stock Units Activity

A summary of restricted unit activity and changes during the year ended December 31, 2012 is presented below:

Restricted Units	Units		Weighted- Average Grant-Date Fair Value		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ($000)
Outstanding at January 1, 2012 (nonvested)	59,072		$	25.23
Granted	90,528		31.01
Vesting and transfer of full ownership to recipients	(89,034	)	27.10
Forfeited	(2,094	)	28.66
Outstanding at December 31, 2012 (nonvested)	58,472		$	31.21	1.1 years	$	1,923

Schedule of Nonvested Performance-based Units Activity

A summary of performance unit activity and changes during the twelve months ended December 31, 2012 is presented below:

Performance Units	Units
Outstanding at January 1, 2012 (nonvested)	85,982
Granted	11,436
Vesting and transfer of common units to recipients	(42,920	)
Outstanding at December 31, 2012 (nonvested)	54,498