Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Measurement [Abstract]

Fair Value Assets Recurring and Nonrecurring

		December 31, 2018					December 31, 2017
	Category		Carrying amount		Fair value		Carrying amount		Fair value
Fair values disclosed:
Cash and cash equivalents	Level 1	$	237,744	$	237,744	$	267,910	$	267,910
Restricted cash	Level 1		67,823		67,823		63,206		63,206
Short-term debt	Level 2		19,896		19,896		7,018		7,018
Long-term debt
Senior unsecured notes	Level 1		489,136		487,813		487,339		520,000
Term loans	Level 2		222,162		224,582		325,553		329,687