Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Policy loans	$ 12,719	$ 13,054
Accrued investment income	86,004	22,615
Receivables from parent and affiliates	111,703	212,696
Liabilities:
Cash collateral for loaned securities	23,350	10,568
Short-term debt	28,101	1,000
Reinsurance payable	275,822	250,277
Payables to parent and affiliates	91,432	25,677
Fair Value
Assets:
Commercial mortgage and other loans	1,235,842	451,142
Policy loans	12,719	13,054
Short-term investments	35,000	0
Cash and cash equivalents	261,886	311
Accrued investment income	86,004	22,615
Reinsurance recoverables	63,775	0
Receivables from parent and affiliates	70,779	14,868
Other assets	53,858	1,085
Total assets	1,819,863	503,075
Liabilities:
Policyholders’ account balances - investment contracts	247,986	102,438
Cash collateral for loaned securities	23,350	10,568
Short-term debt	28,146	1,000
Long-term debt	994,198	0
Reinsurance payable	63,775	0
Payables to parent and affiliates	91,432	25,677
Other liabilities	189,366	83,464
Separate account liabilities - investment contracts	187	293
Total liabilities	1,638,440	223,440
Fair Value | Accounting Standards Update 2015-07
Liabilities:
Cost Method Investments, Fair Value Disclosure	3,400	3,300
Fair Value | Level 1
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term investments	0	0
Cash and cash equivalents	6,886	311
Accrued investment income	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	6,886	311
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	0	0
Short-term debt	0	0
Long-term debt	0	0
Reinsurance payable	0	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Separate account liabilities - investment contracts	0	0
Total liabilities	0	0
Fair Value | Level 2
Assets:
Commercial mortgage and other loans	0	2,793
Policy loans	0	0
Short-term investments	35,000	0
Cash and cash equivalents	255,000	0
Accrued investment income	86,004	22,615
Reinsurance recoverables	0	0
Receivables from parent and affiliates	70,779	14,868
Other assets	53,858	1,085
Total assets	500,641	41,361
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	23,350	10,568
Short-term debt	28,146	1,000
Long-term debt	994,198	0
Reinsurance payable	0	0
Payables to parent and affiliates	91,432	25,677
Other liabilities	189,366	83,464
Separate account liabilities - investment contracts	187	293
Total liabilities	1,326,679	121,002
Fair Value | Level 3
Assets:
Commercial mortgage and other loans	1,235,842	448,349
Policy loans	12,719	13,054
Short-term investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables	63,775	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	1,312,336	461,403
Liabilities:
Policyholders’ account balances - investment contracts	247,986	102,438
Cash collateral for loaned securities	0	0
Short-term debt	0	0
Long-term debt	0	0
Reinsurance payable	63,775	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Separate account liabilities - investment contracts	0	0
Total liabilities	311,761	102,438
Carrying Amount
Assets:
Commercial mortgage and other loans	1,231,893	438,172
Policy loans	12,719	13,054
Short-term investments	35,000	0
Cash and cash equivalents	261,886	311
Accrued investment income	86,004	22,615
Reinsurance recoverables	63,775	0
Receivables from parent and affiliates	70,779	14,868
Other assets	53,858	1,085
Total assets	1,815,914	490,105
Liabilities:
Policyholders’ account balances - investment contracts	250,493	103,003
Cash collateral for loaned securities	23,350	10,568
Short-term debt	28,101	1,000
Long-term debt	971,899	0
Reinsurance payable	63,775	0
Payables to parent and affiliates	91,432	25,677
Other liabilities	189,366	83,464
Separate account liabilities - investment contracts	187	293
Total liabilities	1,618,603	224,005
Carrying Amount | Accounting Standards Update 2015-07
Liabilities:
Cost Method Investments, Fair Value Disclosure	$ 3,100	$ 3,100