Share-Based Compensation - Unvested RSAs Outstanding (Details) - RSAs	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Number of Shares
Unvested RSAs, Beginning Balance (in shares) | shares	366,993
Granted (in shares) | shares	4,687
Vested (in shares) | shares	(93,076)
Forfeited (in shares) | shares	(140)
Unvested RSAs, Ending Balance (in shares) | shares	278,464
Weighted-Average Grant Date Fair Value
Unvested RSAs, Beginning Balance (in dollars per share) | $ / shares	$ 29.79
Granted (in dollars per share) | $ / shares	42.11
Vested (in dollars per share) | $ / shares	22.91
Forfeited (in dollars per share) | $ / shares	22.87
Unvested RSAs, Ending Balance (in dollars per share) | $ / shares	$ 32.31