Share-Based Compensation Schedule of Share-based compensation (Details) - Common Class A [Member]	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Restricted Class A Common Stock
Restricted Class A Common Stock
Restricted class A common stock at the beginning of the period, (in shares) | shares	199,411
Restricted class A common stock granted, (in shares) | shares	236,888
Restricted class A common stock vested/exercised, (in shares) | shares	(62,735)
Restricted class A common stock forfeited, (in shares) | shares	(90,824)
Restricted class A common stock at the end of the period, (in shares) | shares	282,740
Weighted-average grant date fair value
Restricted class A common stock at the beginning of the period, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 15.26
Restricted stock granted, weighted-average grant date fair value (in dollars per share) | $ / shares	21.74
Restricted stock vested/exercised, weighted-average grant date fair value (in dollars per share) | $ / shares	9.09
Restricted stock forfeited, weighted-average grant date fair value (in dollars per share) | $ / shares	20.23
Restricted class A common stock at the end of the period, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 20.63
Stock Options
Stock Options
Stock Options at the beginning of the period (in shares) | shares	1,637,029
Stock Options, granted (in shares) | shares	3,276,164
Stock Options, vested/exercised (in shares) | shares	(80,727)
Stock Options, forfeited (in shares) | shares	(463,400)
Stock Options at the end of the period (in shares) | shares	4,369,066.000
Weighted-average exercise price
Stock Options at the beginning of the period, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 19.71
Stock Options granted, weighted-average grant date fair value (in dollars per share) | $ / shares	21.76
Stock Options vested/exercised, weighted-average grant date fair value (in dollars per share) | $ / shares	19.50
Stock Options, forfeited, weighted-average grant date fair value (in dollars per share) | $ / shares	21.07
Stock Options at the end of the period, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 21.11