Stock Based Compensation and Other Benefit Plans - Stock Options Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding at beginning of period (in shares)	4,684,839
Outstanding at beginning of period (in dollars per share)	$ 7.02
Options granted	0
Weighted-average exercise price of the stock on the date of grant (in dollars per share)	$ 0.00	$ 4.32	$ 9.00
Exercised (in shares)	(416,017)
Exercised (in dollars per share)	$ 5.83
Expired or cancelled (in shares)	(303,297)
Expired or cancelled (in dollars per share)	$ 8.40
Outstanding at end of period (in shares)	3,965,525	4,684,839
Outstanding at end of period (in dollars per share)	$ 7.03	$ 7.02
Outstanding at end of period	5 years 6 months 11 days
Outstanding at end of period	$ 6,172,506
Vested or expected to vest at end of period (in shares)	3,942,351
Vested or expected to vest at end of period (in dollars per share)	$ 7.05
Vested or expected to vest at end of period	5 years 6 months 4 days
Vested or expected to vest at end of period	$ 6,102,803
Options exercisable at end of period (in shares)	3,010,995
Options exercisable at end of period (in dollars per share)	$ 7.60
Options exercisable at end of period	4 years 8 months 12 days
Options exercisable at end of period	$ 3,732,798