Stockholders' Deficit - Share Repurchases (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Stock repurchased during period, value	$ 42,717	$ 7,877	$ 90,073	$ 27,880
2019 Repurchase Program
Class of Stock [Line Items]
Stock repurchased during period (in shares)	523,898		956,847
Stock repurchased during period, value	$ 42,700		$ 81,700
Cumulative amount of shares repurchased (in shares)	956,847		956,847
Cumulative payments for repurchase of common stock	$ 81,700		$ 81,700
Remaining dollar value of shares that may be repurchased	$ 118,300		$ 118,300
October 2015 Share Repurchase Program
Class of Stock [Line Items]
Stock repurchased during period (in shares)	0		110,499
Stock repurchased during period, value	$ 0		$ 8,400
Cumulative amount of shares repurchased (in shares)	1,589,995		1,589,995
Cumulative payments for repurchase of common stock	$ 126,200		$ 126,200