Real Estate and Other Investments - Carrying Amount and Maximum Exposure to Loss Related to VIEs (Detail) - VIE, Not Primary Beneficiary - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Mortgage loans
Variable Interest Entity [Line Items]
Carrying amount	$ 623,141	$ 633,533
Maximum exposure to loss	623,141	633,533
Investment in unconsolidated affiliates
Variable Interest Entity [Line Items]
Carrying amount	322,901	330,730
Maximum exposure to loss	322,901	330,730
Accrued investment income
Variable Interest Entity [Line Items]
Carrying amount	2,114	2,191
Maximum exposure to loss	$ 2,114	$ 2,191