Stock-Based Compensation - Summary of Stock Options Outstanding (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Number of Shares
Beginning of period (in shares) | shares	2,121
Granted (in shares) | shares	188
Exercised (in shares) | shares	(123)
Forfeited (in shares) | shares	(10)
Expired (in shares) | shares	(7)
End of period (in shares) | shares	2,169
Weighted Average Exercise Price
Beginning of period (in dollars per share) | $ / shares	$ 31.53
Granted (in dollars per share) | $ / shares	40.49
Exercised (in dollars per share) | $ / shares	24.70
Forfeited (in dollars per share) | $ / shares	36.38
Expired (in dollars per share) | $ / shares	27.33
End of period (in dollars per share) | $ / shares	$ 32.69