Condensed Consolidated Statements of Comprehensive Income - Entity [Domain] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net income	$ 228,367	$ 53,518	$ 363,623	$ 286,268
Other comprehensive income:
Unrealized (loss) gain on available for sale securities	(75)	66	(4)	95
Net gain on pension and other postretirement benefits	400	232	800	449
Total other comprehensive income	325	298	796	544
Comprehensive income	$ 228,692	$ 53,816	$ 364,419	$ 286,812