Real Estate and Other Investments - Carrying Amount and Maximum Exposure to Loss Related to VIEs (Detail) - VIE, Not Primary Beneficiary - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Mortgage loans
Variable Interest Entity [Line Items]
Carrying amount	$ 590,432	$ 633,533
Maximum exposure to loss	590,432	633,533
Investment in unconsolidated affiliates
Variable Interest Entity [Line Items]
Carrying amount	326,537	330,730
Maximum exposure to loss	326,537	330,730
Accrued investment income
Variable Interest Entity [Line Items]
Carrying amount	2,018	2,191
Maximum exposure to loss	$ 2,018	$ 2,191