Stock-Based Compensation Performance Share Units Activity (Details) - PSU	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, shares, beginning of period	43,219
Outstanding, weighted average fair value, beginning of period | $ / shares	$ 74.35
Granted, shares	65,982	[1]
Granted, weighted average fair value | $ / shares	$ 68.10	[1]
DividendEquivalentUnitsGranted	2,046
DividendEquivalentUnitsWeightedAverageFairValueGrants | $ / shares	$ 44.71
Forfeited, shares	(13,532)
Forfeited, weighted average fair value | $ / shares	$ 64.29
DividendEquivalentUnitsForfeited	(222)
DividendEquivalentUnitsForfeitedWeightedAverageFairValue | $ / shares	$ 44.71
Adjustments due to the Special Cash Dividend	11,575	[1]
Outstanding and nonvested, shares, end of period	109,068	[1],[2]
Outstanding and nonvested, weighted average fair value, end of period | $ / shares	$ 65.82	[1],[2]
Adjustments due to the Special Cash Dividend - PSUs Not Deemed Granted	5,907	[1]

[1] Represents shares of PSUs for which performance targets have been established and which are deemed granted under U.S. GAAP. An additional adjustment of 5,907 PSUs which have not yet been deemed granted under U.S. GAAP is not reflected in the table above.

[2] The weighted average fair value of outstanding PSUs as of September 30, 2015 reflects the adjustment for the Special Cash Dividend.