Stockholders' Equity (Details) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity [Abstract]
Voting common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Voting common stock, shares outstanding (in shares)	198,169,855	196,217,971
Voting common stock, par value (in dollars per share)	$ 0.01	$ 0.01