Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Common stock, shares outstanding	119,428,910
Preferred stock, par value (usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury stock, shares outstanding	2,853,433	934,434
Common Class A [Member]
Common stock, par value (usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	33,340,291	33,158,855
Common stock, shares outstanding	30,486,858	32,224,421
Common Class B [Member]
Common stock, par value (usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	88,942,052	89,108,569
Common stock, shares outstanding	88,942,052	89,108,569