Share-Based Compensation - Restricted Stock Units Activity (Details) - Restricted Stock	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Shares
Unvested, Beginning balance (in shares) | shares	217,898
Granted (in shares) | shares	57,930
Vested (in shares) | shares	(72,744)
Forfeited (in shares) | shares	(8,495)
Unvested, Ending balance (in shares) | shares	194,589
Weighted-Average Grant Date Fair Value
Unvested, Beginning balance (in dollars per share) | $ / shares	$ 76.19
Granted (in dollars per share) | $ / shares	93.16
Vested (in dollars per share) | $ / shares	71.89
Forfeited (in dollars per share) | $ / shares	78.14
Unvested, Ending balance (in dollars per share) | $ / shares	$ 82.76