Stock Options, Employee Stock Purchase Plan and Restricted Stock - Non-vested Restricted Stock Activity (Details) - $ / shares	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, Beginning balance	337,000		337,000		337,000		337,000
Nonvested, Beginning balance (in per share)	$ 35.31		$ 35.31		$ 35.31		$ 35.31
Granted (in shares)
Granted (in per share)
Vested (in shares)
Vested (in per share)
Forfeited (in shares)
Forfeited (in per share)
Nonvested, Ending balance	337,000							337,000
Nonvested, Ending balance (in per share)	$ 35.31							$ 35.31
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, Beginning balance	337,000	16,000	337,000	16,000	337,000	16,000	337,000	16,000	18,000
Nonvested, Beginning balance (in per share)	$ 35.31	$ 15.36	$ 35.31	$ 15.36	$ 35.31	$ 15.36	$ 35.31	$ 15.36	$ 14.63
Granted (in shares)				72,000		337,000		337,000	32,000
Granted (in per share)				$ 24.74		$ 27.54		$ 35.31	$ 15.36
Vested (in shares)			(18,000)	(16,000)	(84,000)	(16,000)	(84,000)	(16,000)	(34,000)
Vested (in per share)			$ 24.74	$ 15.36	$ 35.31	$ 15.36	$ 35.31
Forfeited (in shares)
Forfeited (in per share)								$ 15.36	$ 14.98
Nonvested, Ending balance		16,000	319,000	72,000	253,000	337,000	253,000	337,000	16,000
Nonvested, Ending balance (in per share)		$ 15.36	$ 35.9	$ 24.74	$ 35.31	$ 27.54	$ 35.31	$ 35.31	$ 15.36
Restricted stock vested not yet been released to grantees					66,000		66,000