Significant Accounting Policies (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2020 USD ($) numberOfSegments	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounting Policies [Abstract]
Number of reportable segments | numberOfSegments		4
Assets:
Other long-term investments		$ 377,239		$ 326,347
Agent debit balances		424,000		423,877
Agent debit balances, allowance for credit losses		1,200		1,000
Commercial mortgage participations
Assets:
Other long-term investments		161,841		137,692
Accrued interest receivable		454
Carrying value, net of valuation allowance		161,841		137,692
Commercial mortgage participations | Unfunded commitment
Assets:
Carrying value, net of valuation allowance		$ 87,000
Cumulative Effect, Period Of Adoption, Adjustment
Assets:
Agent debit balances			$ (240)
Cumulative Effect, Period Of Adoption, Adjustment | Commercial mortgage participations
Assets:
Other long-term investments			(335)
Cumulative Effect, Period Of Adoption, Adjusted Balance
Assets:
Agent debit balances			423,637
Cumulative Effect, Period Of Adoption, Adjusted Balance | Commercial mortgage participations
Assets:
Other long-term investments			$ 137,357
ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standard	[1]			(454)
ASU 2016-13 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standard	[1]			(454)
ASU 2016-13, adjustment, net of tax, for commercial loan participations | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standard				265
ASU 2016-13, adjustment for agent debit balances | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standard				$ (189)

[1] Adoption of Accounting Standard Update (ASU) 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, on January 1, 2020. See more information in Note 2, New Accounting Standards.