Stockholders' Equity, Stock Repurchase Program, Dividends and Shelf Registration (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended					6 Months Ended
	Apr. 16, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Mar. 18, 2020	May 31, 2019	Apr. 23, 2018
Stock Repurchase Program [Abstract]
Incremental Class A shares authorized to buyback (in shares)										1,212,759
Dividends [Abstract]
Dividends declared (in dollars per share)			$ 0.02	$ 0.02	$ 0.02	$ 0.02
Shelf Registration [Abstract]
Maximum amount of debt and equity to be issued under shelf registration											$ 500
Class A Stock [Member]
Dividends [Abstract]
Dividends declared (in dollars per share)		$ 0.02	$ 0.02				$ 0.04	$ 0.04
Class A Stock [Member] | Stock Repurchase Program [Member]
Stock Repurchase Program [Abstract]
Stock repurchase authorized, amount									$ 30
Shares repurchased (in shares)	1,200,000	65,704	147,402				120,797	273,756
Average price per share of repurchased shares (in dollars per share)	$ 21.00	$ 11.74	$ 19.02				$ 14.21	$ 19.54
Remaining authorized repurchase amount		$ 29					$ 29
Class B Stock [Member]
Dividends [Abstract]
Dividends declared (in dollars per share)		$ 0.02	$ 0.02				$ 0.04	$ 0.04