Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Available-for-sale investment securities, at fair value (includes assets pledged as collateral of $534,327 in 2017 and $767,437 in 2016)	$ 534,327	$ 767,437
Held-to-maturity investment security, at fair value	0	144,593
Loans held-for-investment (net of allowance for loan losses of $287,128 in 2017 and $260,520 in 2016; includes assets pledged as collateral of $18,880,598 in 2017 and $16,441,068 in 2016)	287,128	260,520
Loans pledged as collateral	18,880,598	16,441,068
Premises and equipment, accumulated depreciation	$ 111,898	$ 114,890
STOCKHOLDERS’ EQUITY
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	165,214,770	164,604,072
Treasury stock, shares (in shares)	20,671,710	20,436,621