Stockholders' Equity - Table of Declared Cash Dividends Per Share (Details) - $ / shares	3 Months Ended													12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock - Class A
Dividends, Common Stock [Abstract]
Dividends declared per Common Share	$ 0.035	[1]	$ 0.035	$ 0.035	$ 0.035	$ 0.030	$ 0.030	$ 0.030	$ 0.030	$ 0.025	$ 0.025	$ 0.025	$ 0.025	$ 0.140	$ 0.120	$ 0.100

[1] See Note (24) Subsequent Events for when dividend was declared.