Reserve for Loss and Loss Adjustment Expenses (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve for reported loss and LAE	$ 1,252,284	$ 1,087,401
Reserve for losses incurred but not reported	1,019,008	870,434
Reserve for loss and loss adjustment expenses	2,271,292	1,957,835	1,740,281
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Reserve for loss and loss adjustment expenses	1,957,835	1,740,281	1,398,438
Less: reinsurance recoverable on unpaid losses	84,036	110,858	20,289
Net loss and loss adjustment expense reserves	1,873,799	1,629,423	1,378,149
Net incurred losses related to Current year	1,479,425	1,351,043	1,239,016
Net incurred losses related to Prior years	18,846	(1,413)	23,332
Net incurred losses	1,498,271	1,349,630	1,262,348
Net paid losses related to Current year	(430,394)	(517,606)	(485,015)
Net paid losses related to Prior years	(705,397)	(598,490)	(530,294)
Net paid losses	(1,135,791)	(1,116,096)	(1,015,309)
Effect of foreign exchange movements	(40,860)	10,842	4,235
Net loss and loss adjustment expense reserves	2,195,419	1,873,799	1,629,423
Reinsurance recoverable on unpaid losses	75,873	84,036	110,858
Reserve for loss and loss adjustment expenses	2,271,292	1,957,835	1,740,281
Percentage of prior year net loss and loss adjustment expense reserves	1.00%	0.10%	1.70%
NGHC Quota Share
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Net incurred losses related to Current year	$ 8,371	$ 6,078	$ 5,179