Selected Quarterly Financial Data (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 197,179	$ 198,899	$ 159,404	$ 195,110	$ 207,680	$ 168,230	$ 154,214	$ 181,599	$ 750,592	$ 711,723	$ 519,385
Gross profit	49,797	42,787	43,534	42,494	47,860	36,698	33,424	30,369	178,612	148,351	57,796
Net earnings	$ 24,370	$ 20,970	$ 23,619	$ 17,937	$ 24,448	$ 14,010	$ 13,361	$ 12,004	$ 86,896	$ 63,823	$ 4,336
Net earnings per common share—basic and diluted (in dollars per share)	$ 1.14	$ 0.98	$ 1.11	$ 0.84	$ 1.14	$ 0.66	$ 0.63	$ 0.56	$ 4.07	$ 2.99	$ 0.20