Incentive Plan (Summary of Incentive Award Plan's Stock Option) (Details)	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Shares:
Options outstanding, beginning of period (in shares) | shares	51,622
Exercised (in shares) | shares	(33,948)
Options outstanding, end of period (in shares) | shares	17,674
Exercisable, end of period (in shares) | shares	17,674
Weighted average exercise price
Options outstanding, beginning of period (in dollars per share) | $ / shares	$ 41.04
Exercised (in dollars per share) | $ / shares	40.68
Options outstanding, end of period (in dollars per share) | $ / shares	41.73
Exercisable, end of period (in dollars per share) | $ / shares	$ 41.73