Stock-Based Compensation - Summary of Restricted Stock, Stock Grants, Stock Units and Performance Shares (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restricted Stock Units, Stock Grants, and Stock Units
Stocks granted and the weighted average fair value
Units granted (in shares)	152,651	179,291	182,240
Grant date fair value (in dollars per share)	$ 64.12	$ 54.89	$ 55.14
Number of granted awards to be settled in cash (in shares)	45,104	49,018	52,620
Performance Shares
Stocks granted and the weighted average fair value
Units granted (in shares)	151,430	166,244	176,332
Grant date fair value (in dollars per share)	$ 64.97	$ 54.86	$ 55.45