Accumulated Other Comprehensive Loss (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period			$ 651,983,000
Other comprehensive income before reclassifications	$ 497,000	$ (70,000)	530,000	$ 208,000
Amounts reclassified from accumulated other comprehensive income			0	(9,665,000)
Other comprehensive income (loss)	497,000	(70,000)	530,000	(9,457,000)
Balance at end of period	188,055,000		188,055,000
Unrealized gains and losses on available-for-sale securities, tax impact			0	0
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(5,446,000)	(5,414,000)	(5,479,000)	3,973,000
Balance at end of period	(4,949,000)	(5,484,000)	(4,949,000)	(5,484,000)
Foreign currency translation adjustment
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(5,439,000)	(5,414,000)	(5,479,000)	3,924,000
Other comprehensive income before reclassifications	487,000	(70,000)	527,000	208,000
Amounts reclassified from accumulated other comprehensive income			0	(9,616,000)
Other comprehensive income (loss)	487,000	(70,000)	527,000	(9,408,000)
Balance at end of period	(4,952,000)	(5,484,000)	(4,952,000)	(5,484,000)
Unrealized gain (loss) on available for sale securities
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(7,000)	0	0	49,000
Other comprehensive income before reclassifications	10,000	0	3,000	0
Amounts reclassified from accumulated other comprehensive income			0	(49,000)
Other comprehensive income (loss)	10,000	0	3,000	(49,000)
Balance at end of period	$ 3,000	$ 0	$ 3,000	$ 0