CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Accounts and accrued income receivable, allowances	$ 31,552	$ 34,662
Pledged securities included in debt securities	$ 122,441	$ 120,742
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	500,000	500,000
Preferred stock, outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares outstanding	109,098,000	107,541,000