Stockholders' Equity - RSU, RSA Activity Under Equity-Based Plans (Details)	6 Months Ended
	Jun. 30, 2019 $ / shares shares
RSUs
Number of Units
Nonvested At Dec 31, 2018 (in shares) | shares	1,737,554
Granted (in shares) | shares	724,172
Vested (in shares) | shares	(511,813)
Forfeited (in shares) | shares	(106,737)
Nonvested At June 30, 2019 (in shares) | shares	1,843,176
Weighted-Average Grant Date Fair Value
Nonvested at Dec 31, 2018 (in dollars per share) | $ / shares	$ 32.83
Granted (in dollars per share) | $ / shares	60.58
Vested (in dollars per share) | $ / shares	30.34
Forfeited (in dollars per share) | $ / shares	36.52
Nonvested at Jun 30, 2019 (in dollars per share) | $ / shares	$ 44.18
RSAs
Number of Units
Nonvested At Dec 31, 2018 (in shares) | shares	346,792
Granted (in shares) | shares	0
Vested (in shares) | shares	(31,248)
Forfeited (in shares) | shares	(11,103)
Nonvested At June 30, 2019 (in shares) | shares	304,441
Weighted-Average Grant Date Fair Value
Nonvested at Dec 31, 2018 (in dollars per share) | $ / shares	$ 49.13
Granted (in dollars per share) | $ / shares	0
Vested (in dollars per share) | $ / shares	50.61
Forfeited (in dollars per share) | $ / shares	49.35
Nonvested at Jun 30, 2019 (in dollars per share) | $ / shares	$ 49.11