CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Additional paid-in capital As previously reported	Additional paid-in capital	Retained earnings As previously reported	Retained earnings	Noncontrolling interest As previously reported	Noncontrolling interest	As previously reported Class A Common Stock	As previously reported	Class A Common Stock	Total
Balance at Dec. 31, 2016		$ 182,772		$ 164,549		$ 1,052,033			$ 2	$ 1,399,356
Balance (in shares) at Dec. 31, 2016									22,427
Changes in stockholders' equity
Net income				38,439		149,185				187,624
Stock and unit-based compensation		4,861				10,200				15,061
Issuance of Class A common stock in settlement of director fees		133				120				253
Repurchase of Class A common stock		(8,599)							$ (8,599)	(8,599)
Shares of Class A common stock repurchased									(505)
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		20,583				(20,583)				$ 20,583
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc. (in shares)									1,297	1,297
Tax effect of exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		(3,404)								$ (3,404)
Balance at Sep. 30, 2017		196,346		202,988		1,190,955			$ 2	1,590,291
Balance (in shares) at Sep. 30, 2017									23,219
Balance at Jun. 30, 2017		199,146		185,907		1,126,197			$ 2	1,511,252
Balance (in shares) at Jun. 30, 2017									23,473
Changes in stockholders' equity
Net income				17,081		65,411				82,492
Stock and unit-based compensation		1,411				2,944				4,355
Issuance of Class A common stock in settlement of director fees		25				59				84
Repurchase of Class A common stock		(8,599)							$ (8,599)	(8,599)
Shares of Class A common stock repurchased									(505)
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		3,656				(3,656)				$ 3,656
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc. (in shares)									251	251
Tax effect of exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		707								$ 707
Balance at Sep. 30, 2017		196,346		202,988		1,190,955			$ 2	1,590,291
Balance (in shares) at Sep. 30, 2017									23,219
Changes in stockholders' equity
Cumulative effect of change in accounting principle for all existing classes of mortgage servicing rights at fair value | Accounting Standards Codification 250 Mortgage Servicing Rights Fair Value				189		587				776
Balance after adjustment		204,103		265,495		1,250,850			$ 2	1,720,450
Balance at Dec. 31, 2017	$ 204,103		$ 265,306		$ 1,250,263		$ 2	$ 1,719,674		1,719,674
Balance (in shares) at Dec. 31, 2017							23,530		23,530
Changes in stockholders' equity
Net income				48,945		142,538				191,483
Class A common stock dividends				(10,054)						(10,054)
Stock and unit-based compensation		7,400				18,084				25,484
Stock and unit-based compensation (in shares)									285
Issuance of Class A common stock in settlement of director fees		79				166				245
Repurchase of Class A common stock		(1,554)				(3,272)			$ (4,826)	(4,826)
Shares of Class A common stock repurchased									(236)
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		32,501				(32,502)			$ 1	$ 32,501
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc. (in shares)									1,616	1,616
Tax effect of exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		(6,072)								$ (6,072)
Balance at Sep. 30, 2018		236,457		304,386		1,375,864			$ 3	1,916,710
Balance (in shares) at Sep. 30, 2018									25,195
Balance at Jun. 30, 2018		229,941		299,951		1,332,049			$ 3	1,861,944
Balance (in shares) at Jun. 30, 2018									25,009
Changes in stockholders' equity
Net income				14,489		41,663				56,152
Stock and unit-based compensation		2,944				6,472			$ 55	9,416
Class A common stock dividends				(10,054)						(10,054)
Issuance of Class A common stock in settlement of director fees		28				57				85
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		4,377				(4,377)				$ 4,377
Exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc. (in shares)									131	131
Tax effect of exchange of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.		(833)								$ (833)
Balance at Sep. 30, 2018		$ 236,457		$ 304,386		$ 1,375,864			$ 3	$ 1,916,710
Balance (in shares) at Sep. 30, 2018									25,195