Stockholders' Equity - Other (Details) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
	May 16, 2016 shares	Dec. 31, 2016 USD ($) item $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares
Equity incentive plans
Shares available for issuance		2,800
Stock-based compensation
Stock-based compensation expense (in dollars) | $		$ 4,700	$ 5,600	$ 5,900
Number of shares
Exercised (in shares)			(15)
Forfeited or expired (in shares)			(27)
Weighted-average exercise price
Exercised (in dollars per share) | $ / shares			$ 10.60
Forfeited or expired (in dollars per share) | $ / shares			$ 10.60
Common Class A
Equity incentive plans
Shares authorized for issuance		7,200
Employee and Directors Stock Options
Equity incentive plans
Granted (in shares)		890	215	140
Vested at the end of the period (in shares)		1,533
Stock-based compensation
Unrecognized compensation cost related to unvested stock options (in dollars) | $		$ 3,500
Weighted-average periods over which unrecognized compensation cost recognized		2 years 2 months 12 days
Estimated forfeitures (as a percent)		1.50%
Valuation assumptions
Dividend yield (as a percent)		0.00%
Number of shares
Outstanding at the beginning of the period (in shares)		2,043	1,870	1,730
Granted (in shares)		890	215	140
Exercised (in shares)		(13)
Outstanding at the end of the period (in shares)		2,920	2,043	1,870	1,730
Vested at the end of the period (in shares)		1,533
Exercisable at the end of the period (in shares)		1,533
Weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share) | $ / shares		$ 11.49		$ 11.20
Granted (in dollars per share) | $ / shares		11.97	$ 13.61	11.56
Exercised (in dollars per share) | $ / shares		10.60
Forfeited or expired (in dollars per share) | $ / shares				$ 11.23
Outstanding at the end of the period (in dollars per share) | $ / shares		11.64	$ 11.49		$ 11.20
Vested at the end of the period (in dollars per share) | $ / shares		11.55
Exercisable at the end of the period (in dollars per share) | $ / shares		$ 11.55
Weighted-average remaining contractual term
Outstanding		7 years 7 months 6 days	7 years 7 months 6 days	8 years 4 months 24 days	9 years 3 months 18 days
Granted		6 years 2 months 12 days	6 years 2 months 12 days	9 years 8 months 12 days
Vested at the end of the period		6 years 6 months
Exercisable at the end of the period		6 years 6 months
Aggregate intrinsic value
Outstanding at the beginning of the period (in dollars) | $		$ 6,740	$ 4,721	$ 2,208
Outstanding at the end of the period (in dollars) | $		1,274	$ 6,740	$ 4,721	$ 2,208
Vested at the end of the period (in dollars) | $		974
Exercisable at the end of the period (in dollars) | $		$ 974
Weighted-average grant date fair value of options granted (in dollars per share) | $ / shares		$ 3.71	$ 4.13	$ 3.75
Restricted Stock
Equity incentive plans
Granted (in shares)		395	99	79
Stock-based compensation
Unrecognized compensation cost related to unvested restricted stock (in dollars) | $		$ 3,300
Weighted-average periods over which unrecognized compensation cost recognized		2 years
Number of shares
Outstanding at the beginning of the period (in shares)		494	719	945
Granted (in shares)		395	99	79
Vested (in shares)		(328)	(324)	(305)
Outstanding at the end of the period (in shares)		561	494	719	945
Weighted-average grant date fair value
Outstanding at the beginning of the period (in dollars per share) | $ / shares		$ 9.79	$ 9.82	$ 10.18
Granted (in dollars per share) | $ / shares		11.82	12.42	11.34
Vested (in dollars per share) | $ / shares		10.88	10.65	11.33
Outstanding at the end of the period (in dollars per share) | $ / shares		$ 10.58	$ 9.79	$ 9.82	$ 10.18
Restricted Stock | Common Class A
Equity incentive plans
Additional of number of shares authorized to issue	3,200
Time Based Restricted Stock and Stock Option
Equity incentive plans
Number of equal annual installments for vesting of awards | item		3
Time Based Stock Option | Black Scholes Pricing Model
Valuation assumptions
Risk-free interest rate, minimum (as a percent)		1.60%	1.76%	1.76%
Risk-free interest rate, maximum (as a percent)		2.44%	2.12%	1.92%
Volatility, minimum (as a percent)		26.40%	25.80%	28.40%
Volatility, maximum (as a percent)		32.40%	29.50%	30.90%
Weighted-average expected term		6 years 2 months 12 days	6 years 3 months 18 days
Time Based Stock Option | Black Scholes Pricing Model | Maximum
Valuation assumptions
Weighted-average expected term				6 years 3 months 18 days
Time Based Stock Option | Black Scholes Pricing Model | Minimum
Valuation assumptions
Weighted-average expected term				6 years
Time Based Restricted Stock
Weighted-average grant date fair value
Vesting period		3 years
Event Based Restricted Stock and Stock Option | Common Class A
Equity incentive plans
Closing price per share to be attained for vesting of awards to begin (in dollars per share) | $ / shares		$ 15.00
Event Based Restricted Stock and Stock Option | Common Class A | Minimum
Equity incentive plans
Number of trading days on which the closing price per share should attain the specified price per share for vesting of awards to begin | item		10
Event Based Stock Option
Aggregate intrinsic value
Unvested options		300
Event Based Restricted Stock
Aggregate intrinsic value
Unvested options		200