Stockholders' Equity and EPS - Activity Related to Net Gains on Cash Flow Hedges in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cash flow hedge gains expected to reclassified out of AOCI over next 12 months	$ 700
Beginning balance	5,264,843	$ 4,319,415
Ending balance	5,483,823	4,559,724
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	0	0
Net increase in fair value, net of tax	795	0
Net realized loss reclassified to net income, net of tax	2	0
Ending balance	$ 797	$ 0