CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		$ 110,701	$ 63,659	$ 332,795
Other comprehensive income (loss), net of tax
Change in unrealized gains on investments in available-for-sale securities		1,181	122	783
Adjustment for net (gains) losses realized and included in net income, net of tax		0	(557)	(712)
Total change in unrealized gains on investments in available-for-sale securities, net of tax	[1]	1,181	(435)	71
Unrealized gains (losses) on cash flow hedges		0	0	4,626
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		0	(1,821)	(5,390)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	[2]	0	(1,821)	(764)
Total other comprehensive income (loss), net of tax		1,181	(2,256)	(693)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest		111,882	61,403	332,102
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		(47)	53	0
Comprehensive income		$ 111,929	$ 61,350	$ 332,102

[1] Net of tax of $314, ($234) and $38 for the years ended December 31, 2017, 2016 and 2015, respectively.

[2] Net of tax of zero, ($981) and ($411) for the years ended December 31, 2017, 2016 and 2015, respectively.