Accumulated Other Comprehensive Income (Reclassification out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on investments		$ 162,366	[1]	$ 6,525
Provision for income taxes		(117,189)		(33,149)
Portion of net loss recognized in other comprehensive income, before taxes		337		(638)
Net income		220,318		50,044
Gain on pension plan curtailment		(29,578)		0
Unrealized gains on securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax		(96,134)		(3,936)
OTTI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax		281		1,671
Pension under- funding
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax		18,819		(2,616)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax		(77,034)		(4,881)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains on securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on investments		147,898		6,056
Provision for income taxes		(51,764)		(2,120)
Net income		96,134		3,936
Reclassification out of Accumulated Other Comprehensive Income | OTTI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes		151		899
Portion of net loss recognized in other comprehensive income, before taxes		(432)		(2,570)
Net income		(281)		(1,671)
Reclassification out of Accumulated Other Comprehensive Income | Pension under- funding
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and postretirement unrecognized net of period benefit cost		(28,953)		4,025
Gain on pension plan curtailment		(29,578)		0
Provision for income taxes		10,134		(1,409)
Total reclassifications for the period, net of tax		18,819		(2,616)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of prior service cost
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and postretirement unrecognized net of period benefit cost	[2]	0		(25)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of net loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and postretirement unrecognized net of period benefit cost	[2]	$ 625		$ 4,050

[1] (a)2016 includes $146,727 related to the sale of Assurant Employee Benefits mainly through reinsurance transactions.

[2] These accumulated other comprehensive income components are included in the computation of net periodic pension cost. See Note 14 - Retirement and Other Employee Benefits for additional information.