Employee and Non-Employee Director Stock and Benefit Plans - Stock Options/2007 Plan (Details)	1 Months Ended	7 Months Ended	12 Months Ended
	Aug. 31, 2016 USD ($)	Jul. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2016 installment $ / shares shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2014 $ / shares shares
Number of Shares
Exercised (in shares)			(24,498)
Stock options
Number of Shares
Outstanding at the beginning of the period (in shares)		42,665	42,665	306,853	343,326
Granted (in shares)			196,851
Exercised (in shares)			(42,665)	(71,455)	(14,228)
Forfeited (in shares)				(192,733)	(22,245)
Outstanding at the end of the period (in shares)			196,851	42,665	306,853
Amount exercisable at the end of the period (in shares)			0	42,665	306,853
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares		$ 12.17	$ 12.17	$ 17.23	$ 17.29
Granted (in dollars per share) | $ / shares			16.18
Exercised (in dollars per share) | $ / shares			12.17	16.26	14.28
Forfeited (in dollars per share) | $ / shares				18.71	20.09
Outstanding at the end of the period (in dollars per share) | $ / shares			$ 16.18	12.17	17.23
Amount exercisable at the end of the period (in dollars per share) | $ / shares				$ 12.17	$ 17.23
2007 Plan
Employee and non-employee director stock and benefit plans
Shares of common stock authorized			13,068,208
Directors' Equity Subplan | Restricted stock unit awards.
Employee and non-employee director stock and benefit plans
Value of shares granted at or shortly after the time of appointment | $	$ 120,000	$ 100,000
Value of shares granted on the forty fifth day following each of the annual meetings of stockholders | $	$ 80,000	$ 72,000
Chief Executive Officer | Time-based award
Employee and non-employee director stock and benefit plans
Number of equal annual vesting installments | installment			3
Number of Shares
Granted (in shares)			196,851
Weighted Average Exercise Price
Expiration period (in years)			8 years