Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income available to common stockholders	$ 28,032	$ 9,882
Other comprehensive income:
Unrealized gain (loss) on derivatives, net of income taxes	16,171	(764)
Less interest income (expense) on derivatives recognized into earnings, net of income taxes	1,233	(563)
Comprehensive income	$ 42,970	$ 9,681