Subsequent Event (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Oct. 10, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Subsequent Event [Line Items]
Net losses and loss expenses incurred		$ 1,491,803	$ 1,464,285	$ 4,506,674	$ 3,385,307
Minimum | Subsequent Event [Member]
Subsequent Event [Line Items]
Net losses and loss expenses incurred	$ 100,000
Maximum | Subsequent Event [Member]
Subsequent Event [Line Items]
Net losses and loss expenses incurred	$ 200,000