Incentive Plan (Summary of Incentive Award Plan's Stock Option) (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Shares:
Options outstanding, beginning of period (in shares) | shares	80,933
Exercised (in shares) | shares	(29,311)
Options outstanding, end of period (in shares) | shares	51,622
Exercisable, end of period (in shares) | shares	51,622
Weighted average exercise price
Options outstanding, beginning of period (in dollars per share) | $ / shares	$ 37.25
Exercised (in dollars per share) | $ / shares	30.58
Options outstanding, end of period (in dollars per share) | $ / shares	41.04
Exercisable, end of period (in dollars per share) | $ / shares	$ 41.04