Incentive Plan (401(k)) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Incentive Plan [Abstract]
Vesting percentage of discretionary contributions	100.00%
Aggregate cost of contributions to the 401(k) Plan	$ 2.4	$ 2.0	$ 1.5