CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Comprehensive income (loss), net of tax
Net income	$ 1,014,652	$ 582,716	$ 281,882
Other comprehensive income (loss)
Net unrealized gain (loss) on securities	248,412	84,703	(17,075)
Reclassification of net realized (gain) loss on securities into earnings	(10,308)	37,724	(7,308)
Total other comprehensive income (loss)	238,104	122,427	(24,383)
Total comprehensive income	1,252,756	705,143	257,499
Comprehensive income attributable to noncontrolling interests	57,119	78,263	13,246
Comprehensive income attributable to common stockholders	$ 1,195,637	$ 626,880	$ 244,253