Reinsurance Reinsurance (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Premiums Written
Written premiums, direct	$ 1,647,341,000	$ 1,565,188,000
Written premiums, assumed	204,464,000	240,079,000
Written premiums, ceded	(276,403,000)	(279,387,000)
Total net premiums written	1,575,402,000	1,525,880,000
Premiums Earned
Earned premiums, direct	1,524,736,000	1,381,572,000
Earned premiums, assumed	203,342,000	225,762,000
Earned premiums, ceded	(256,065,000)	(243,722,000)
Net premiums earned	1,472,013,000	1,363,612,000
Ceded losses incurred	118,391,000	100,684,000
Uncollectible reinsurance	1,000,000			1,000,000
Fees and Commissions, Other	$ 43,651,000		$ 37,170,000