Supplemental Cash Flow Information (Details 4) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2012
Supplemental Cash Flow Information
Income taxes paid, net of refunds received		3,026	282
Cash paid for interest		43,936	52,872
Additional capital lease obligation to finance property and equipment		11,199
Convertible senior subordinated notes
Supplemental Cash Flow Information
Shares issued in connection with certain redemptions (in shares)	8,123	387,147	772,398	772,438
Capital Lease Obligations [Member]
Supplemental Cash Flow Information
Additional capital lease obligation to finance property and equipment		3,192	61