Incentive Plan (Summary of Incentive Award Plan's Stock Option) (Details)	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Shares
Options outstanding, end of period (shares) | shares	51,622
Exercised (shares) | shares	(30,945)
Options outstanding, end of period (shares) | shares	20,677
Exercisable, end of period (shares) | shares	20,677
Weighted average exercise price
Options outstanding, beginning of period ($ per share) | $ / shares	$ 41.04
Exercised ($ per share) | $ / shares	40.58
Options outstanding, end of period ($ per share) | $ / shares	41.73
Exercisable, end of period ($ per share) | $ / shares	$ 41.73