Share-Based Compensation - Cash-settled Restricted Stock Activity (Details) - Cash-settled Restricted Stock	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Shares
Unvested, Beginning balance (in shares) | shares	103,790
Granted (in shares) | shares	33,505
Vested (in shares) | shares	(26,300)
Forfeited (in shares) | shares	(7,550)
Unvested, Ending balance (in shares) | shares	103,445
Weighted-Average Grant Date Fair Value
Unvested, Beginning balance (in dollars per share) | $ / shares	$ 90.06
Granted (in dollars per share) | $ / shares	93.51
Vested (in dollars per share) | $ / shares	91.96
Forfeited (in dollars per share) | $ / shares	93.51
Unvested, Ending balance (in dollars per share) | $ / shares	$ 93.51