Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income before noncontrolling interests	$ 211,834	$ 114,311	$ 82,595
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Gains attributable to the fair value of future servicing rights, net of guaranty obligation	(193,886)	(192,825)	(133,631)
Change in the fair value of premiums and origination fees (NOTE 2)	5,781	(10,796)	1,959
Amortization and depreciation	131,246	111,427	98,173
Stock compensation-equity and liability classified	21,134	18,477	14,084
Provision (benefit) for credit losses	(243)	(612)	1,644
Deferred tax expense (benefit)	(30,961)	37,595	16,919
Originations of loans held for sale	(17,018,424)	(12,040,559)	(12,111,553)
Sales of loans to third parties	17,937,915	12,697,209	10,688,356
Amortization of deferred loan fees and costs	(2,298)	(1,578)	(1,775)
Amortization of debt issuance costs and debt discount	4,886	5,581	3,756
Origination fees received from loans held for investment	1,109	2,104	1,429
Tax shortfall (benefit) from vesting of equity awards			(1,410)
Cash paid to settle risk-sharing obligations		(1,613)	(795)
Changes in:
Servicing fees and other receivables	(12,234)	(5,744)	(623)
Other assets	(7,064)	(1,014)	2,974
Accounts payable and other liabilities	22,866	22,035	7,739
Performance deposits from borrowers	(4,019)	5,368	(8,556)
Net cash provided by (used in) operating activities	1,067,642	759,366	(1,338,715)
Cash flows from investing activities
Capital expenditures	(5,207)	(2,478)	(1,413)
Purchase of equity-method investments			(5,000)
Funding of preferred equity investments	(16,884)	(24,835)
Capital invested in Interim Program JV	(6,342)
Net cash paid to increase ownership interest in a previously held equity method investment		(1,058)
Acquisitions, net of cash received	(15,000)	(6,350)	(12,767)
Purchase of mortgage servicing rights	(7,781)	(43,097)
Originations of loans held for investment	(183,916)	(414,763)	(180,375)
Principal collected on loans held for investment upon payoff	219,516	425,820	172,323
Transfer of loans held for investment upon formation of Interim Program JV	119,750
Net cash provided by (used in) investing activities	104,136	(66,761)	(27,232)
Cash flows from financing activities
Borrowings (repayments) of warehouse notes payable, net	(955,040)	(649,845)	1,423,911
Borrowings of interim warehouse notes payable	140,341	325,828	137,397
Repayments of interim warehouse notes payable	(237,912)	(355,738)	(125,542)
Repayments of note payable	(1,104)	(1,104)	(4,819)
Proceeds from issuance of common stock	3,013	3,765	7,553
Repurchase of common stock	(34,899)	(12,893)	(50,261)
Debt issuance costs	(3,890)	(3,630)	(4,145)
Distributions to noncontrolling interests		(5)
Tax benefit from vesting of equity awards			1,410
Net cash provided by (used in) financing activities	(1,089,491)	(693,622)	1,385,504
Net increase (decrease) in cash, cash equivalents, restricted cash, and restricted cash equivalents (NOTE 2)	82,287	(1,017)	19,557
Cash, cash equivalents, restricted cash, and restricted cash equivalents at beginning of period	213,467	214,484	194,927
Total of cash, cash equivalents, restricted cash, and restricted cash equivalents at end of period	295,754	213,467	214,484
Supplemental Disclosure of Cash Flow Information:
Cash paid to third parties for interest	56,267	39,311	32,854
Cash paid for income taxes	$ 45,524	$ 34,432	$ 34,832