CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) (USD $)
Mar. 31, 2015
Dec. 31, 2014
Preferred stock, par value (in dollars per share) 0.00001 0.00001
Preferred stock, shares authorized (in shares) 10,000,000 10,000,000
Preferred stock, shares issued (in shares) 0 0
Preferred stock, shares outstanding (in shares) 0 0
Treasury stock, shares (in shares) 2,569,125 2,173,793
Class A Common Stock    
Common stock, par value (in dollars per share) 0.00001 0.00001
Common stock, shares authorized (in shares) 890,000,000 890,000,000
Common stock, shares outstanding (in shares) 145,954,701 145,455,008
Class B Common Stock    
Common stock, shares authorized (in shares) 100,000,000 100,000,000
Common stock, shares issued (in shares) 43,042,826 43,042,826
Common stock, shares outstanding (in shares) 43,042,826 43,042,826