Fair Value - Fair Value Option Maturities, Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair value
Total fair value	$ 2,668,929	$ 2,521,647
Recurring basis
Fair value
Total fair value	2,668,929	2,521,647
Mortgage loans held for sale | Recurring basis
Fair value
Current through 89 days delinquent	2,357,344	2,324,203
Not in foreclosure	235,957	143,631
In foreclosure	75,628	53,813
Total fair value	2,668,929	2,521,647
Principal amount due upon maturity
Current through 89 days delinquent	2,252,816	2,220,371
Not in foreclosure	240,728	144,011
In foreclosure	79,577	56,254
Total principal amount due upon maturity	2,573,121	2,420,636
Difference
Current through 89 days delinquent	104,528	103,832
Not in foreclosure	(4,771)	(380)
In foreclosure	(3,949)	(2,441)
Total difference	$ 95,808	$ 101,011