Business Information - Information by Geographic Region, After Elimination of All Significant Inter-company Accounts and Transactions (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Disclosure [Line Items]
Total revenues	$ 76,600	$ 92,000	$ 63,000	$ 43,600	$ 76,300	$ 44,600	$ 86,700	$ 79,600	$ 275,234	$ 287,152	$ 285,079
Income (loss) before taxes	24,000	30,600	12,500	400	21,100	3,000	25,400	21,700	67,470	71,206	70,475
Total assets	337,650				353,446				337,650	353,446	386,970
Americas [Member]
Segment Reporting Disclosure [Line Items]
Total revenues									160,633	160,082	179,204
Income (loss) before taxes									32,642	32,741	56,862
Total assets	168,853				144,462				168,853	144,462	166,128
Europe
Segment Reporting Disclosure [Line Items]
Total revenues									83,369	84,360	57,606
Income (loss) before taxes									26,818	31,872	8,422
Total assets	33,460				54,772				33,460	54,772	40,758
Australia
Segment Reporting Disclosure [Line Items]
Total revenues									26,149	34,868	44,801
Income (loss) before taxes									9,752	6,270	10,982
Total assets	128,861				149,534				128,861	149,534	172,406
Asia
Segment Reporting Disclosure [Line Items]
Total revenues									5,083	7,842	3,468
Income (loss) before taxes									(1,742)	323	(5,791)
Total assets	$ 6,476				$ 4,678				$ 6,476	$ 4,678	$ 7,678