Share-Based Compensation - Unvested RSAs Outstanding (Details) - RSAs	9 Months Ended
	Sep. 30, 2019 $ / shares shares
Number of Shares
Unvested RSAs, Beginning Balance (in shares) | shares	344,362
Granted (in shares) | shares	119,743
Vested (in shares) | shares	(113,043)
Forfeited (in shares) | shares	(2,400)
Unvested RSAs, Ending Balance (in shares) | shares	348,662
Weighted-Average Grant Date Fair Value
Unvested RSAs, Beginning Balance (in dollars per share) | $ / shares	$ 36.80
Granted (in dollars per share) | $ / shares	37.08
Vested (in dollars per share) | $ / shares	23.61
Forfeited (in dollars per share) | $ / shares	40.54
Unvested RSAs, Ending Balance (in dollars per share) | $ / shares	$ 41.51