Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	$ 811,850
Accumulated other comprehensive loss at end of period	836,216
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(133)	$ (209)
Losses reclassified from net accumulated other comprehensive loss	19	19
Net current period other comprehensive income	19	19
Accumulated other comprehensive loss at end of period	$ (114)	$ (190)