Noncontrolling Interest (Details) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended								12 Months Ended
	Nov. 01, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income and the effects of changes in noncontrolling interest
Net income attributable to PennyMac Financial Services, Inc. common stockholders		$ 152,661	$ 121,473	$ 72,696	$ 46,135	$ 38,749	$ 14,489	$ 17,837	$ 16,619	$ 392,965	$ 87,694	$ 100,757
Shares of Class A common stock of PennyMac Financial Services, Inc. issued pursuant to exchange of Class A units of Private National Mortgage Acceptance Company, LLC by noncontrolling interest unitholders and issued as equity compensation (in shares)											1,635	1,608
Increase in the Company's paid in capital for exchange of Class A units of Private National Mortgage Acceptance Company, LLC to common stock of PennyMac Financial Services, Inc. pursuant to the Reorganization											$ (326,653)
Shares of common stock of PennyMac Financial Services, Inc. issued for exchange of Class A units of Private National Mortgage Acceptance Company, LLC by noncontrolling interest unitholdes pursuant to the Reorganization											52,263
New PFSI | Class A Unit
Noncontrolling Interest [Line Items]
Common stock conversion ratio (as a percent)	100.00%
New PFSI | Common Stock
Noncontrolling Interest [Line Items]
Common stock conversion ratio (as a percent)	100.00%
Private National Mortgage Acceptance Company, LLC
Net income and the effects of changes in noncontrolling interest
Percentage of Private National Mortgage Acceptance Company, LLC held by noncontrolling interest (as a percent)												69.20%
Noncontrolling interest in Private National Mortgage Acceptance Company, LLC
Net income and the effects of changes in noncontrolling interest
Increase in the Company's paid-in capital accounts for exchanges of Class A units of Private National Mortgage Acceptance Company, LLC to Class A common stock of PennyMac Financial Services, Inc.											$ 33,156	$ 27,119
Increase in the Company's paid in capital for exchange of Class A units of Private National Mortgage Acceptance Company, LLC to common stock of PennyMac Financial Services, Inc. pursuant to the Reorganization											(1,390,973)
Additional paid-in-capital and Par
Net income and the effects of changes in noncontrolling interest
Increase in the Company's paid in capital for exchange of Class A units of Private National Mortgage Acceptance Company, LLC to common stock of PennyMac Financial Services, Inc. pursuant to the Reorganization											$ 1,064,320