Stock-Based Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Movement in Outstanding Shares of Restricted Class A Common Stock and Weighted-Average Grant Date Fair Value Per Share

The following table details the movement in our outstanding shares of restricted class A common stock and the weighted-average grant date fair value per share:

	Restricted Class A Common Stock			Weighted-Average Grant Date Fair Value Per Share
Balance as of December 31, 2015		1,114,908		$	27.64
Granted		872,294			28.88
Vested		(641,780	)		27.21
Forfeited		(35,427	)		27.49
Balance as of December 31, 2016		1,309,995		$	28.68
Granted		925,319			31.78
Vested		(748,016	)		28.69
Forfeited		(3,123	)		27.37
Balance as of December 31, 2017		1,484,175		$	30.61