Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Accounts and accrued income receivable, allowances	$ 21,984	$ 22,841
Pledged securities included in debt securities	$ 91,636	$ 110,975
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	112,476,000	111,496,000