Notes payable, convertible senior notes and line of credit - Summary of Notes Payable (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Banks - varying payments and rates	$ 98,000	$ 60,000
Other than banks	4,399	11,180
Notes payable	$ 102,399	$ 71,180