Net Interest Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Interest income:
Cash and short-term investments	$ 2,894	$ 814	$ 7,533	$ 2,001
Loans held for sale at fair value	35,800	34,941	101,509	95,982
Placement fees relating to custodial funds	43,231	23,397	98,628	55,014
Interest income, excluding related parties	81,925	59,152	207,670	152,997
Interest income	83,452	60,964	212,685	158,683
Interest expense:
Assets sold under agreements to repurchase	19,429	4,676	47,709	15,943
Mortgage loan participation purchase and sale agreements	2,304	2,533	7,034	6,450
Notes payable	17,525	21,369	53,559	55,939
Obligations under capital lease	274	122	476	444
Interest shortfall on repayments of mortgage loans serviced for Agency securitizations	12,453	4,883	24,978	14,259
Interest on mortgage loan impound deposits	2,104	1,452	4,967	3,517
Interest expense, non-affiliates	54,089	35,035	138,723	96,552
Interest expense	56,380	38,775	146,847	108,136
Net interest income	27,072	22,189	65,838	50,547
PMT
Interest income:
From PennyMac Mortgage Investment Trust	1,527	1,812	5,015	5,686
Interest expense:
To PennyMac Mortgage Investment Trust Excess servicing spread financing at fair value	2,291	3,740	8,124	11,584
Assets sold under agreements to repurchase
Interest expense:
Assets sold under agreements to repurchase	19,429	4,676	47,709	15,943
Incentives recorded	$ 1,600	$ 12,800	$ 14,700	$ 35,500