Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income and other, net	$ 393,365	$ 421,384	$ 41,232
Income tax expense	$ (140,731)	(130,858)	$ (22,753)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income and other, net		497
Income tax expense		(189)
Net of tax		$ 308