Share-Based Compensation - Unvested RSAs Outstanding (Details) - RSAs	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Number of Shares
Unvested RSAs, Beginning Balance (in shares) | shares	344,362
Granted (in shares) | shares	7,034
Vested (in shares) | shares	(108,638)
Forfeited (in shares) | shares	(1,900)
Unvested RSAs, Ending Balance (in shares) | shares	240,858
Weighted-Average Grant Date Fair Value
Unvested RSAs, Beginning Balance (in dollars per share) | $ / shares	$ 36.80
Granted (in dollars per share) | $ / shares	37.78
Vested (in dollars per share) | $ / shares	23.48
Forfeited (in dollars per share) | $ / shares	40.54
Unvested RSAs, Ending Balance (in dollars per share) | $ / shares	$ 42.81