Net Interest Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest income:
Cash and short-term investments	$ 1,259	$ 2,894	$ 4,863	$ 7,533
Loans held for sale at fair value	41,854	35,800	120,866	101,509
Placement fees relating to custodial funds	9,163	43,231	44,419	98,628
Interest income, excluding related parties	52,276	81,925	170,148	207,670
Interest income	52,952	83,452	172,834	212,685
Interest expense:
Assets sold under agreements to repurchase	27,322	19,429	70,493	47,709
Mortgage loan participation purchase and sale agreements	999	2,304	3,870	7,034
Obligations under capital lease	83	274	354	476
Notes payable	10,738	17,525	37,668	53,559
Interest shortfall on repayments of mortgage loans serviced for Agency securitizations	20,711	12,453	54,536	24,978
Interest on mortgage loan impound deposits	1,256	2,104	4,561	4,967
Interest expense, non-affiliates	61,109	54,089	171,482	138,723
Interest expense	63,179	56,380	177,898	146,847
Net interest (expense) income	(10,227)	27,072	(5,064)	65,838
PMT
Interest income:
From PennyMac Mortgage Investment Trust	676	1,527	2,686	5,015
Interest expense:
To PennyMac Mortgage Investment Trust Excess servicing spread financing at fair value	2,070	2,291	6,416	8,124
Assets sold under agreements to repurchase
Interest expense:
Assets sold under agreements to repurchase	$ 27,322	19,429	$ 70,493	47,709
Incentives recorded		$ 1,600		$ 14,700