Geographic Area Information - Geographical Information Pertaining to Company's Operating Revenues (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues	$ 27,803	$ 21,734	$ 55,427	$ 40,743
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues	19,711	14,673	39,274	27,088
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues	3,768	2,427	7,089	4,728
Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues	2,275	2,817	4,966	5,376
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues	1,496	1,467	3,005	2,866
Asia/Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues	$ 553	$ 350	$ 1,093	$ 685