Summary of Significant Accounting Policies Prior Period Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Payments for Origination and Purchases of Loans Held-for-sale							$ (158,097)	$ (188,072)	$ (258,202)
Proceeds from the sale of loans held for sale							161,357	196,813	262,948
Net Cash Provided by (Used in) Operating Activities							$ 86,006	68,660	$ 33,306
Loans Held For Sale [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Payments for Origination and Purchases of Loans Held-for-sale	$ (35,151)	$ (37,470)	$ (74,695)	$ (88,457)	$ (118,106)	$ (140,981)		(188,072)
Proceeds from the sale of loans held for sale	37,003	43,210	76,263	94,269	122,283	148,026		196,813
Net Cash Provided by (Used in) Operating Activities	1,852	5,740	1,568	5,812	4,177	7,045		8,741
Loans Held For Sale [Member] | As Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Payments for Origination and Purchases of Loans Held-for-sale	(28,468)	(24,828)	(61,508)	(64,035)	(95,665)	(105,557)		(143,993)
Proceeds from the sale of loans held for sale	30,320	30,568	63,076	69,847	99,842	112,602		152,734
Net Cash Provided by (Used in) Operating Activities	1,852	5,740	1,568	5,812	4,177	7,045		8,741
Loans Held For Sale [Member] | Adjustments [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Payments for Origination and Purchases of Loans Held-for-sale	(6,683)	(12,642)	(13,187)	(24,422)	(22,441)	(35,424)		(44,079)
Proceeds from the sale of loans held for sale	6,683	12,642	13,187	24,422	22,441	35,424		44,079
Net Cash Provided by (Used in) Operating Activities	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		$ 0