Common Stock, Preferred Stock and Warrants - Additional Information (Detail)		1 Months Ended								2 Months Ended	3 Months Ended			12 Months Ended
	Apr. 27, 2017 USD ($) shares	Jan. 31, 2019 USD ($) director shares	Jan. 31, 2018 USD ($) director executive_office shares	Jun. 30, 2017 USD ($) shares	Oct. 31, 2016 shares	Mar. 31, 2016 USD ($) shares	Jan. 31, 2016 USD ($) director executive_office shares	Jun. 30, 2014 USD ($) $ / shares shares	Jun. 30, 2014 shares	Feb. 28, 2017 USD ($) director shares	Mar. 31, 2018	Jun. 30, 2017 USD ($) shares	Mar. 31, 2017 USD ($) executive_office shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Jun. 30, 2015 USD ($)
Class of Stock [Line Items]
Total number of shares authorized (in shares) | shares														105,000,000
Common stock, shares authorized (in shares) | shares														100,000,000	100,000,000
Common stock, par value (USD per share) | $ / shares														$ 0.001	$ 0.001
Preferred shares, shares authorized (in shares) | shares														5,000,000	5,000,000
Preferred stock, par value (USD per share) | $ / shares														$ 0.001	$ 0.001
Common stock, shares issued (in shares) | shares														29,169,913	26,957,354
Common stock, shares outstanding (in shares) | shares														29,169,913	26,957,354
Repurchase of common stock (in shares) | shares								3,112,840	3,112,840
Repurchase of common stock, average price per share (USD per share) | $ / shares								$ 7.71
Repurchase of common stock, value								$ 24,000,000
Repurchase of convertible senior notes														$ 0	$ 35,614,000	$ 8,035,000
Cash dividend paid														$ 0	$ 0
4.875% convertible senior notes (due 2020)
Class of Stock [Line Items]
Amount of convertible notes repurchased and retired							$ 2,000,000
4.25% Convertible Senior Notes (due 2018)
Class of Stock [Line Items]
Amount of convertible notes repurchased and retired				$ 12,000,000								$ 12,000,000	$ 39,100,000			$ 6,100,000
Repurchase of convertible senior notes				11,600,000									$ 24,100,000
Debt instrument shares common stock issued upon conversion (in shares) | shares													2,900,000
Restricted Stock
Class of Stock [Line Items]
Retirement of restricted stock (in shares) | shares														(42,346)	(29,689)	(50,719)
Restricted stock surrendered, in values														$ 100,000	$ 100,000	$ 1,500,000
Common Stock
Class of Stock [Line Items]
Retirement of restricted stock (in shares) | shares															(9,000)	(25,000)
Common Stock | 4.25% Convertible Senior Notes (due 2018)
Class of Stock [Line Items]
Amount of convertible notes repurchased and retired				$ 11,600,000						$ 39,100,000		$ 11,600,000
Debt instrument shares common stock issued upon conversion (in shares) | shares				112,400						2,865,000		112,400			3,000,000
Common stock shares issued upon conversion of debt instrument, value				$ 400,000						$ 15,100,000					$ 15,500,000
Common Stock | Hong Kong Meisheng Cultural Co
Class of Stock [Line Items]
Common stock issued (in shares) | shares	3,660,891
Common stock issued, value	$ 19,300,000
Securities
Class of Stock [Line Items]
Retirement of common stock (share) | shares																1,766,284	1,547,361
Retirement of common stock																$ 13,500,000	$ 13,200,000
Securities | 4.875% convertible senior notes (due 2020)
Class of Stock [Line Items]
Amount of convertible notes repurchased and retired																	2,000,000
Repurchase of convertible senior notes																	1,900,000
Securities | 4.25% Convertible Senior Notes (due 2018)
Class of Stock [Line Items]
Amount of convertible notes repurchased and retired																	6,100,000
Repurchase of convertible senior notes																	$ 6,100,000
Maximum | Restricted Stock
Class of Stock [Line Items]
Vesting period														2 years
Maximum | Securities
Class of Stock [Line Items]
Stock repurchase, authorized amount																		$ 35,000,000
Executive officer
Class of Stock [Line Items]
Restricted stock issued (in shares) | shares			1,914,894			134,058	449,120			873,787
Restricted stock issued, value			$ 4,500,000			$ 900,000	$ 3,600,000			$ 4,500,000
Number of executive officers | executive_office			2				2						2
Vesting period						3 years	3 years
Executive officer | Restricted Stock
Class of Stock [Line Items]
Vesting period						3 years					3 years
Non-employee directors
Class of Stock [Line Items]
Restricted stock issued (in shares) | shares	13,319		249,480		2,463		62,710			94,102				41,580
Restricted stock issued, value	$ 100,000		$ 600,000				$ 500,000			$ 500,000				$ 100,000
Number of non-employee directors | director			6				5			5
Non-employee directors | Hong Kong Meisheng Cultural Co
Class of Stock [Line Items]
Restricted stock issued (in shares) | shares	13,319
Restricted stock issued, value	$ 100,000
Subsequent Event | Executive officer
Class of Stock [Line Items]
Restricted stock issued (in shares) | shares		3,061,224
Restricted stock issued, value		$ 4,500,000
Number of executive officers | director		2