CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Accounts receivable, allowance (in dollars)	$ 2,570	$ 7,529
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	2,761,535
Preferred stock, shares outstanding	0	2,761,535
Redemption amount	$ 0	$ 69,038
Common stock and additional paid-in capital, par value (in dollars per share)
Common stock and additional paid-in capital, shares authorized	55,000,000	55,000,000
Common stock and additional paid-in capital, shares issued	19,697,000	19,927,000
Common stock and additional paid-in capital, shares outstanding	19,697,000	19,927,000
Preferred stock, par value (in dollars per share)
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	2,811,535	0
Preferred stock, shares outstanding	2,811,535	0
Redemption amount	$ 70,288	$ 0