Schedule III Supplemental Insurance Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental insurance information
Deferred acquisition costs	$ 353,408	$ 314,071
Future policy benefits, losses, claims and expenses	25,924,574	24,566,218
Unearned premium reserves	43,837	42,937
Other policy claims and benefits payable	753,215	764,523
Premium income	446,395	464,093	422,153
Net investment income	1,228,388	1,091,389	1,191,551
Benefits, claims, losses and settlement expenses	1,222,445	1,232,091	1,198,310
Amortization of deferred acquisition costs	41,045	55,490	51,434
Other operating expenses	822,077	691,831	643,081
Individual Markets Segment
Supplemental insurance information
Deferred acquisition costs	284,174	238,150
Future policy benefits, losses, claims and expenses	14,980,872	13,945,756
Unearned premium reserves	43,837	42,937
Other policy claims and benefits payable	726,479	740,056
Premium income	360,305	354,202	314,350
Net investment income	748,015	688,279	729,885
Benefits, claims, losses and settlement expenses	902,982	921,096	882,726
Amortization of deferred acquisition costs	13,700	34,650	28,926
Other operating expenses	123,150	107,491	107,969
Retirement Services Segment
Supplemental insurance information
Deferred acquisition costs	69,234	75,921
Future policy benefits, losses, claims and expenses	10,533,822	10,229,678
Other policy claims and benefits payable	581	499
Premium income	1,215	3,954	3,670
Net investment income	426,340	351,729	414,114
Benefits, claims, losses and settlement expenses	206,339	196,115	204,296
Amortization of deferred acquisition costs	27,345	20,840	22,508
Other operating expenses	619,820	517,369	469,919
Other Segment
Supplemental insurance information
Future policy benefits, losses, claims and expenses	409,880	390,784
Other policy claims and benefits payable	26,155	23,968
Premium income	84,875	105,937	104,133
Net investment income	54,033	51,381	47,552
Benefits, claims, losses and settlement expenses	113,124	114,880	111,288
Other operating expenses	$ 79,107	$ 66,971	$ 65,193