Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Securities held-to-maturity	$ 244,239	$ 236,125
Preferred stock, par value (in USD per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000,000	10,000,000,000
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000,000	500,000,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, shares issued (in shares)	115,889,175,000	115,889,175,000
Common stock, shares outstanding (in shares)	115,889,175,000	115,889,175,000