Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets:
Policy loans	$ 12,865	$ 13,054
Accrued investment income	73,279	22,615
Receivables from parent and affiliates	129,585	212,696
Liabilities:
Cash collateral for loaned securities	21,084	10,568
Short-term debt	32,852	1,000
Long-term debt	971,898	0
Payables to parent and affiliates	321,008	25,677
Carrying Amount
Assets:
Commercial mortgage and other loans	1,232,800	438,172
Policy loans	12,865	13,054
Short-term investments	35,000
Cash and cash equivalents	559	311
Accrued investment income	73,279	22,615
Receivables from parent and affiliates	79,531	14,868
Other assets	111,114	1,085
Total assets	1,545,148	490,105
Liabilities:
Policyholders’ account balances - investment contracts	246,966	103,003
Cash collateral for loaned securities	21,084	10,568
Short-term debt	32,852	1,000
Long-term debt	971,898
Payables to parent and affiliates	104,484	25,678
Other liabilities	428,019	83,464
Separate account liabilities - investment contracts	214	293
Total liabilities	1,805,517	224,006
Carrying Amount | Accounting Standards Update 2015-07
Liabilities:
Cost Method Investments, Fair Value Disclosure	3,000	3,100
Fair Value
Assets:
Commercial mortgage and other loans	1,276,141	451,142
Policy loans	12,865	13,054
Short-term investments	35,000
Cash and cash equivalents	559	311
Accrued investment income	73,279	22,615
Receivables from parent and affiliates	79,531	14,868
Other assets	111,114	1,085
Total assets	1,588,489	503,075
Liabilities:
Policyholders’ account balances - investment contracts	248,455	102,438
Cash collateral for loaned securities	21,084	10,568
Short-term debt	32,954	1,000
Long-term debt	1,023,803
Payables to parent and affiliates	104,484	25,678
Other liabilities	428,019	83,464
Separate account liabilities - investment contracts	214	293
Total liabilities	1,859,013	223,441
Fair Value | Accounting Standards Update 2015-07
Liabilities:
Cost Method Investments, Fair Value Disclosure	3,300	3,300
Fair Value | Level 1
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term investments	0
Cash and cash equivalents	559	311
Accrued investment income	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	559	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
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
Cash and cash equivalents	0	0
Accrued investment income	73,279	22,615
Receivables from parent and affiliates	79,531	14,868
Other assets	46,157	1,085
Total assets	233,967	41,361
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	21,084	10,568
Short-term debt	32,954	1,000
Long-term debt	1,023,803
Payables to parent and affiliates	104,484	25,678
Other liabilities	363,062	83,464
Separate account liabilities - investment contracts	214	293
Total liabilities	1,545,601	121,003
Fair Value | Level 3
Assets:
Commercial mortgage and other loans	1,276,141	448,349
Policy loans	12,865	13,054
Short-term investments	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Receivables from parent and affiliates	0	0
Other assets	64,957	0
Total assets	1,353,963	461,403
Liabilities:
Policyholders’ account balances - investment contracts	248,455	102,438
Cash collateral for loaned securities	0	0
Short-term debt	0	0
Long-term debt	0
Payables to parent and affiliates	0	0
Other liabilities	64,957	0
Separate account liabilities - investment contracts	0	0
Total liabilities	$ 313,412	$ 102,438