Condensed Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 76,704	$ 64,849	$ 145,706	$ 102,555
Unrealized gain (loss) on interest rate derivative instruments, net of deferred taxes of $749, $0, ($191) and $0	1,238	0	(356)	0
Other comprehensive income (loss)	1,238	0	(356)	0
Comprehensive income	$ 77,942	$ 64,849	$ 145,350	$ 102,555