Incentive Plan (Summary of Incentive Award Plan's Stock Option) (Details)	9 Months Ended
	Sep. 30, 2016 $ / shares shares
Shares
Options outstanding, end of period (shares) | shares	51,622
Exercised (shares) | shares	(33,948)
Options outstanding, end of period (shares) | shares	17,674
Exercisable, end of period (shares) | shares	17,674
Weighted average exercise price
Options outstanding, beginning of period ($ per share) | $ / shares	$ 41.04
Exercised ($ per share) | $ / shares	40.68
Options outstanding, end of period ($ per share) | $ / shares	41.73
Exercisable, end of period ($ per share) | $ / shares	$ 41.73