Stock Based Compensation

12 Months Ended

Dec. 31, 2015

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

Stock Based Compensation

Stock Based Compensation

We are authorized to issue up to 13.8 million shares of the General Partner's common stock under our stock-based employee and non-employee compensation plans.

Restricted Stock Units

Under our 2015 Long-Term Incentive Plan, which was approved by the General Partner's shareholders in April 2015, and our 2015 Non-Employee Directors Compensation Plan (collectively, the "Compensation Plans"), RSUs may be granted to non-employee directors, executive officers and selected management employees. A RSU is economically equivalent to a share of the General Partner's common stock.

RSUs granted to employees in 2015 vest ratably over a three-year period and are payable in shares of our common stock with a new share of such common stock issued upon each RSU's vesting. RSUs granted to employees prior to 2015 vest ratably over a five-year period and are payable in the same manner. RSUs granted to existing non-employee directors vest 100% over one year and have contractual lives of one year.

To the extent that a recipient of a RSU grant is not determined to be retirement eligible, as defined by the Compensation Plans, we recognize expense on a straight-line basis over the vesting period. Expense is recognized immediately at the date of grant to the extent a recipient is retirement eligible and expense is accelerated to the extent that a participant will become retirement eligible prior to the end of the contractual life of granted RSUs.

The following table summarizes transactions for our RSUs, excluding dividend equivalents, for 2015: 

Restricted Stock Units	Number of RSUs		Weighted Average Grant Date Fair Value
RSU's at December 31, 2014	2,150,009		$15.03
Granted	611,075		$21.15
Vested	(758,457	)	$14.13
Forfeited	(187,505	)	$17.02
RSU's at December 31, 2015	1,815,122		$17.26

Compensation cost recognized for RSUs totaled $11.7 million, $12.3 million and $13.3 million for the years ended December 31, 2015, 2014 and 2013, respectively.

As of December 31, 2015, there was $10.9 million of total unrecognized compensation expense related to nonvested RSUs granted under the Plan, which is expected to be recognized over a weighted average period of 2.1 years.

The weighted average grant date fair value of RSUs as of December 31, 2013 was $13.71.