Stock-based Compensation Expense Activity in Non-Performance Based Restricted Stock Awards (Details) - Restricted Stock And Restricted Stock Units	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Shares
Nonvested, beginning of period (in shares) | shares	105,288
Granted (in shares) | shares	61,156
Vested (in shares) | shares	(39,073)
Forfeited (in shares) | shares	(9,250)
Nonvested, end of period (in shares) | shares	118,121
Weighted Average Grant Date Fair Value
Nonvested, beginning of period (in dollars per share) | $ / shares	$ 61.34
Granted (in dollars per share) | $ / shares	56.64
Vested (in dollars per share) | $ / shares	61.97
Forfeited (in dollars per share) | $ / shares	62.37
Nonvested, end of period (in dollars per share) | $ / shares	$ 58.62